Future Powering Options Exploring alternative methods of ship propulsion

July 2013

Future ship powering options c1 Contents

Foreword 2 Glossary 76

Executive summary 3 References 77

1. Introduction 8 Appendices 78 1.1 Drivers for change 9 1. Terms of reference 78 1.1.1 Carbon emissions 9 2. Membership of the working group 79 1.1.2 Price of oil 10 3. Referee and review group 81 1.2 The shipping industry 11 4. Statement from Vice-President of the European 1.2.1 Technical development 11 Commission Siim Kallas and EU Commissioner 1.2.2 Operation 13 for Climate Action Connie Hedegaard, October 2012 82 1.3 International regulations 15 5. A ship systems approach 83 1.3.1 Emissions control under MARPOL Annex VI 16 6. Further aspects relating to nuclear merchant ship 1.4 Global context of shipping 17 propulsion 84 7. International atomic energy principles and 2. Design options 18 requirements 89 2.1 Ship energy considerations 18 8. The energy efficiency design index 92 2.2 The ship system 19 9. Calendar for main emission legislation events 2.3 Energy Efficiency Design Index 20 2010–2020 93 10. Potential applicability of measures and options 3. Primary propulsion options 22 discussed 94 Conventional propulsion options and fuels 3.1 Diesel engines 22 3.2 26 3.3 Liquid natural gas (LNG) 29 3.4 Gas turbines 31 Other propulsion technology options 3.5 Nuclear 33 3.6 Batteries 41 3.7 Fuel cells 43 3.8 sources 47 3.9 Hydrogen 50 3.10 Anhydrous ammonia 51 3.11 Compressed air and liquid nitrogen 51 3.12 Hybrid propulsion 53

4. Further Propulsion Considerations 54 4.1 Propulsors 54 4.2 Energy-saving devices 60 4.3 Hull design and appendages 62 4.4 Hull coatings 62 4.5 Superconducting electric motors 64 4.6 Ship operational considerations 66 © Royal Academy of Engineering 4.6.1 Operational profile 66 July 2013 ISBN: 978-1-909327-01-6 4.6.2 Weather routing 66 4.6.3 Plant operational practices 66 Published by Royal Academy of Engineering Prince Philip House 5. Time frame for technical development 68 3 Carlton House Terrace London SW1Y 5DG Tel: 020 7766 0600 6. Conclusions 70 Fax: 020 7930 1549 www.raeng.org.uk

Registered Charity Number: 293074 c2 Royal Academy of Engineering Future ship powering options 1 Foreword Executive summary

Shipping is vital to the world economy. It is a critical part of international International agreements on the need to combat climate change, the import and export markets and supports the global distribution of goods. To achieve fluctuating but generally rising costs of marine fuels which account for As for all industries, concerns about climate change require the reduction effective a large proportion of the running costs of a ship, and developments on a of greenhouse gas emissions from the shipping sector. This entails higher number of other fronts have led many in the industry to question whether fuel prices for low sulphur fuels. It means that the industry must prepare improvements the present methods of ship propulsion are sustainable. These concerns for the new future and investigate alternative, more economic ship in efficiency and are enhanced by the introduction of environmental regulations intended propulsion systems. to reduce the impact of climate change – primarily MARPOL Annex VI and reductions in the Energy Efficiency Design Index regulations together with the possible This report, prepared by an expert working group at the Royal Academy emissions for introduction of carbon taxes. of Engineering, gives a fascinating insight into the development of ship propulsion systems. It sets out how we got to the current technological , an This report embraces a number of conventional propulsion methods and solutions and examines a wide range of possibilities for future ship integrated fuels and also addresses the newer options of biofuels, liquid natural Photo by Carmel King powering options. The report presents a thorough review of the range of gas and hydrogen. In the case of other propulsion options, the subjects technologies, and examines the advantages and limitations of systems systems of nuclear propulsion, alternative fuels, batteries, fuel cells, renewable from solar and power, through fuel cells to nuclear propulsion. engineering energy, superconducting electric motors and hybrid propulsion are considered. Additional propulsion influences are addressed and include I believe that this report will be of great benefit to the shipping industry, approach is conventional and non-conventional propulsors, magnetohydrodynamic offering an overview that is both broad and expertly informed. I hope that required propulsion, energy-saving devices, hull design and coatings. it is made full use of as this important sector joins the challenge to reduce emissions on a global scale and maintain its competitiveness. There are other factors that affect the emissions from shipping. Avoiding poor weather by using weather-routing technologies offers important fuel consumption benefits. Similar benefits are also realisable if ship speed is optimised during voyages and the crew are trained to understand the implications of the decisions and actions they take. Furthermore, the condition of a ship’s machinery has a significant influence on fuel consumption and emissions performance. There is, therefore, good reason Sir John Parker GBE FREng to keep machinery well-maintained and operated by well-motivated crews. President of the Royal Academy of Engineering Studies show that larger ships are more carbon-efficient than smaller vessels, and it is known that deploying slower ship speeds is an effective means of reducing emissions. However, de-rating existing engines installed in ships, or fitting smaller engines than are conventionally adopted for a given ship size in order to meet constraints, can create significant operational risks from under-powering ships, particularly in poor weather.

2 Royal Academy of Engineering Future ship powering options 3 Executive summary

To achieve effective improvements in efficiency and reductions in Medium- to long-term options The diesel engine emissions for ships, an integrated systems engineering approach is Biofuels are potential medium-term alternatives to conventional fuels for is currently the required. This must embrace all of the elements of naval architecture, diesel engines. Synthetic fuels based on branch-chain higher alcohols and marine and control engineering alongside operation practices. Moreover, new types of E-coli as well as algae and other microorganisms are medium- most widespread a systems approach must include all of the stakeholder requirements to to long-term possibilities, but further work is necessary to examine their of marine prime achieve a sustainable and optimal design solution. With any propulsion storage, handling, and impacts on health, safety and the environment. option it is essential that the overall emission profile of the propulsion Di-methyl ether shows some potential as an ; however, movers. It is a method and the fuel used is properly assessed, so that reductions in there are presently disadvantages which need resolution in terms of well-understood exhaust emissions from ships are not at the cost of increasing harmful lubricity and corrosion together with the creation of sufficient production emissions in land-based sectors that produce either the propulsion and supply networks. technology and a machinery or the fuel. reliable form of Fuel cells offer potential for ship propulsion with good experience gained in The report identifies a range of short-, medium- and long-term auxiliary and low-power propulsion machinery. For , the marine propulsion propulsion options: and auxiliary high-temperature solid oxide and molten carbonate fuel cells show most promise, while for lower powers the low temperature proton exchange power generation, Short-term options membrane fuel cells are more suitable. While hydrogen is the easiest fuel with engine The diesel engine is currently the most widespread of marine prime to use in fuel cells, this would require a worldwide infrastructure to be movers. It is a well-understood technology and a reliable form of marine developed for supply to ships. manufacturers propulsion and auxiliary power generation, with engine manufacturers having well- having well-established repair and spare part networks around the world. Nuclear ship propulsion has the advantage during operation of producing In addition, there is a supply of trained engineers and the education no CO2, NOX, SOX, volatile organic or particulate emissions. A significant established repair requirements for future engineers are well-understood, with appropriate body of experience exists in the design and safe operation of shipboard and spare part training facilities available. However, diesel engines will continue to nuclear propulsion plant, particularly in the case of PWR designs. The produce CO2 emissions as well as NOX, SOX, volatile organic compounds and conventional methods of design, planning, building and operation of networks around particulate matter. merchant ships would, however, need a complete overhaul since the the world process would be driven by a safety case and systems engineering Liquid natural gas (LNG) can be used in reciprocating engine propulsion approach. Issues would also need to be addressed in terms of international systems and is a known technology with classification society rules for the regulation, public perception and acceptability, financing the initial capital fuel systems already in existence. Service experience with dual fuel and cost, training and retention of crews, setting up and maintenance of a converted diesel engines, although limited at the present time, has been global infrastructure support system, insurance and nuclear emergency satisfactory and currently LNG is considerably cheaper than conventional response plans for ports . fuels. LNG, while not free of harmful emissions, has benefits in terms of

CO2, NOX, SOX emissions, given that methane slip is avoided during the Battery technology is developing rapidly, offering some potential for combustion and fuelling processes. propulsion. However, full ship battery propulsion requires further technical development and is likely to be confined to relatively small Gas turbines have been successfully used in niche areas of the marine ships. Nevertheless, battery-based propulsion would be beneficial due market and represent a proven high power density propulsion technology. to producing no CO2, NOX, SOX, volatile organic or particulate emissions in However, the fuel for aero-derivative gas turbines is expensive when operation. Batteries may offer a potential hybrid solution in conjunction compared to conventional marine fuels and gas turbine thermal efficiencies with other modes of propulsion for some small- to medium-sized ships are lower than for slow-speed diesel engines of similar power. provided that their recharging does not increase the production of other harmful emissions from land-based sources or elsewhere. Renewable energy, principally derived from wind and solar origins, is considered as an augment to the main propulsion and auxiliary power Superconducting electric motor technology has been successfully used requirements of a ship. in demonstrator applications, with low electrical losses resulting in a more efficient motor. Depending upon the type of prime mover deployed, exhaust emissions will be lower, the machine can run for some time after a coolant failure, and further advantages may accrue from their smaller size.

4 Royal Academy of Engineering Future ship powering options 5 Hydrogen, compressed air and liquid nitrogen are likely to be long-term To develop future propulsion considerations. While the latter two options are energy storage ship propulsion media, hydrogen is a fuel which generates no CO2 or SOX emissions to the atmosphere and would use land-based sources of power for its creation. systems within It would need a supply infrastructure to be viable in a marine context, but reasonable it is ideal for use in fuel cells. Compressed air and nitrogen would use land- based sources of power for creation and the tank storage technologies timescales, are well understood – though tank corrosion is an issue in salt-laden research and environments. The size, pressure rating and cryogenic capabilities, in the case of liquid nitrogen, of the ship storage tanks will determine the amount funding are of energy storage and hence usefulness of the concept. As with hydrogen, needed in a number a supply and infrastructure and distribution network would be needed. of areas In summary, the following options are considered appropriate:

i. For existing ships, reciprocating engines with exhaust gas attenuation technologies are the principal option together with fuels that produce

fewer CO2 emissions. LNG is one such fuel and, together with some other alternatives, would require an adequate bunkering infrastructure to be developed, particularly for deep sea voyages. Some attention could also be usefully paid to reducing the demand for shipboard energy. ii. For new buildings planned in the near-term, the scenario is broadly similar but with the option to include hybrid propulsion systems depending on ship size and intended use. iii. In the case of ships to be built in the medium- to long-term, further propulsion options include alternative fuel options, fuel cells, batteries and nuclear. The former methods await technological development but nuclear, while well understood technically, would require a major change to ship owning and operation infrastructure and practices.

Renewable power sources such as wind and solar are likely to be augments to power requirements, assuming a return to full propulsion is not contemplated. If, in the future, a hydrogen economy is adopted, then hydrogen may become a realistic marine fuel option.

To develop future ship propulsion systems within reasonable timescales, research and funding are needed in a number of areas: fuel cells capable of sustainable powers for ship propulsion; modular nuclear reactors; hull form and skin friction reduction measures; ship operational methodologies and perhaps high capability batteries and hydrogen generation. There is also a need for further soundly based techno-economic studies on target emissions from ships.

6 Royal Academy of Engineering Future ship powering options 7 Introduction

of the total sea trade in terms of the weight “The most developed and the emerging of cargo transported, while container economies must stabilise and then reduce 1. Introduction shipping was around 15%. material consumption levels through: dramatic improvements in resource use The carriage of freight by sea is low-cost. efficiency, including: reducing waste; Consequently, because the transport costs investment in sustainable resources, are low the international community is not technologies and infrastructures; and generally aware of shipping economics. systematically decoupling economic Within the shipping industry, however, activity from environmental impact.” competition for trade between companies (Royal Society, 2012) is strong and there are four elements which have a significant influence on To lay a foundation for the consideration shipping economics. These are the freight; of alternative means of propulsion of the shipbuilding; the sale and purchase; merchant ships, the Royal Academy of International The propulsion of merchant shipping are also included. International shipping is and the scrapping markets. Freight rates Engineering convened a working group has, during the last century, undergone estimated to contribute some 3% of global are largely a function of the available in July 2010, (Appendices 1, 2 and 3), to shipping is a significant transformation. It is now emissions of CO2 and this, if no attenuating transport capacity any political intervention consider the issues involved and this report estimated to dominated by diesel propulsion machinery action is implemented, will vary as the and world trade levels where these are summarises the findings. It principally with the cost of fuel accounting for a shipping industry changes to reflect world all variables. There are also components considers the technical and regulatory contribute some large proportion of the running costs of trade. Although the industry has reduced of the derivative, voyage charter and issues relating to the options and aims to 3% of global the ship. Against this background, recent its consumption of fossil fuels by, for time-charter markets and it is all of these place these into short-, medium- and long- developments have led many in the industry example, employing increasingly thermally component aspects which generate cash term perspectives. emissions of CO2 to question whether the present modes of efficient diesel engines in recent decades, for the shipping industry. The shipbuilding ship propulsion are sustainable due to three the current total fuel oil consumption is in market produces new ships for the industry main factors: excess of 350 million tonnes per annum. at agreed prices and thereby takes cash a. Rising fuel costs as a result of the out of the industry in return for ships to escalating price of oil. At present some 95% of the world’s goods be delivered at some time in the future, 1.1 Drivers for change b. Environmental regulations introduced to are moved by sea. Furthermore, Figure typically in two or three years. In contrast, 1.1.1 Carbon emissions mitigate the effects of climate change. 1.1 (Stopford, 2012) underlines generally the sale and purchase market moves cash c. The potential introduction of carbon increasing trends in cargo growth with only between shipping companies while the The Kyoto Protocol under Article 2.2 taxes. small perturbations that have coincided demolition market generates a small income stated that “the Parties included in Annex with world financial or political difficulties. when ships are scrapped. I shall pursue limitation or reduction of Within the wider international debate on This trend of increasing shipping activity is emissions of greenhouse gas emissions not climate change there are increasing calls for forecast to increase further in a recent IMO The cyclic nature of economic prosperity controlled by the Montreal Protocol from shipping to reduce emissions of greenhouse study. Additionally, it can be seen that, in in the shipping industry has been a aviation and marine bunker fuels, working gases, most notably carbon dioxide 2011, the oil and the bulk transport trades characteristic of the industry for many through the International Civil Aviation although other exhaust gases components respectively accounted for 28% and 39% years. While the design life of a ship is Organization (ICAO) and the International normally about 25 years, when freight rates Maritime Organization (IMO), respectively.”. are low many younger ships may become Work has continued on this aspect under 10 15% due for scrapping since they are relatively the Subsidiary Body for Scientific and 28% • Oil 9 inefficient and generally unfit for profit Technological Advice and the Subsidiary Gas • 8 Body for Implementation although firm Iron ore generation. As such, the remaining value of 15% • agreements are yet to be reached. Sea trade in 2011 • Coal 7 these ships has to be written off company • Other bulk balance sheets. Consequently, under those 3% Container 6 • conditions, while there is an appetite within Failure to reach agreement at the • Other 5 11% the industry for innovation, there are also international level has prompted individual 18% 4 nations or groups of nations to consider 10% reservations about the risks associated 3 with innovation in alternative propulsion the issue. The European Union, under the European Climate Change Programme II, is 2 methods. Figure 1.1 The trend in carrying out a consultation on options to 1 cargo growth 1962 to 2011 In the wider context, a recent report by include shipping in its overall commitments [Stopford 2012] Billion tonnes of cargo 0 the Royal Society recommended that to greenhouse gas reduction. It has 1971 1977 1974 1965 1995 1962 1992 2001 2010 welcomed the introduction of the Energy 1983 1968 1986 1989 1998 1980 2007 2004

8 Royal Academy of Engineering Future ship powering options 9 Introduction

Efficiency Design Index (EEDI) developed 1.1.2 Price of oil concerns over the years that supplies are At present and for the foreseeable future within the IMO forum and sees monitoring The 18th and dwindling and that production may one day predictions of the future price of fuel will While air- and water-related emissions emissions as the first step in controlling 19th Centuries fail to meet demand. This concept is known remain uncertain and financing shipboard already influence the design and operation emissions. However, it is clearly intent on as peak oil. With demand growing, especially fuel supplies is the responsibility of ship of ships, of more immediate concern to ship pushing forward with actual reductions were times of in developing nations, and the apparent rate operators to exercise judgement and operators is the current and future price of (Appendix 4). innovation, not of discovery of new oil fields dropping, the the necessity for hedging arrangements. oil. With fuel costs accounting for as much prospect of a global peak in oil production Clearly, if at some time in the future the as 50 to 60% of total operating costs, rises The United Kingdom legally enshrined just in hull form, has led some to speculate that the price of price of oil was to decrease, then the in bunker fuel prices have implications for greenhouse gas emission reduction targets structure and oil will rise significantly in the future. attractiveness of alternative means of ship operating economics and margins. under the 2008 Climate Change Act: 80% propulsion from a purely operational Within this scenario the level playing field reductions relative to 1990 levels by 2050 sail design but Proven oil reserves relative to current viewpoint would wane. However, within the concept, cherished by ship operators, is an with interim budgets specified up to that also in matters of demand have remained relatively constant wider context of a likely increasing demand essential aspect of shipping commerce. date. Currently, aviation and shipping are for many years (BP 2012) due mainly to better for seaborne transport and reductions in not included in these targets. However, ship performancE methods of identifying prospective fields land-based emissions, marine emissions Historically, the bunker prices of marine the Committee for Climate Change, an as well as the opening up of previously require some attention. fuels have fluctuated significantly and independent statutory body set up to uneconomic fields. This has been made Figure 1.2 shows the changes for 380 advise government on setting and meeting possible by advanced drilling techniques cSt marine fuel over the last 20 years. the carbon budgets, have concluded that which have now become economic because Furthermore, these fluctuations are there is no reason to treat shipping any prices have increased. Furthermore, the reflected in the various markets around differently from other sectors. Specifically, price of oil appears to have a relationship 1.2 The Shipping the world and there are similar trends they recommend that: with the activities of global finance industry observable between the different grades • International shipping emissions should markets as well as on the fundamentals of of fuel. Over the same period, crude oil 1.2.1 Technical development be added at around 9 MtCO2e per year, supply and demand; something that world prices (BP 2012) have shown similar general based on a projection of UK emissions governments, led by the US, are attempting The evolution of ships and their trade tends in price fluctuation; however, when which reflects current international to control. routes has a long history, almost as long viewed in a longer time frame major policy; that is, the EEDI adopted by the as that of mankind. This development global events, such as World War II, do not International Maritime Organisation. Increases in the use of natural gas are also of merchant ships witnessed a gradual appear to have had a significant effect. • Non-Kyoto climate effects of aviation, influential in that liquefied natural gas (LNG) progression from relatively small and simple Consequently, over the last two decades for example contrails and induced has become a global commodity supplying sail-powered ships in earlier centuries bunker prices have been showing an cirrus, and shipping should be further industry and the domestic market. The through to the larger and more complex fast increasing mean trend together with large researched, closely monitored and supply is supplemented by unconventional clipper ships in the latter part of the 19th fluctuations about the mean trend. reduced where possible, but not types of petroleum, particularly shale Century: some of these, under favourable included in carbon budgets. gas in the US and tar sands in Canada, conditions, being able to attain speeds Recognising that oil is ultimately a finite which are opening up new resources of of the order of 20 knots. Then as coaling resource, there have been repeated hydrocarbons and demonstrating that many stations became more plentiful around the years will pass before the world runs out of globe, steamships started to make their this energy source. It remains to be seen, 380CST appearance and increased in numbers. however, as to whether these sources can • Houston 380CST $800 be extracted at a sufficient rate and price The 18th and 19th centuries were times of • Singapore 380CST to satisfy global demand. Furthermore, innovation, not just in hull form, structure Rotterdam 380CST $700 • concerns have been expressed about the and sail design but also in matters of ship • Fujairah 380CST $600 extraction procedures on the surrounding performance. For example, the introduction environment and, in the case of the in 1761 of copper hull sheathing on $500 United Kingdom, a recent report (Royal HMS Alarm (Lambert 2008), initially to $400 Society and Royal Academy of Engineering, 2012) prevent attacks on the hull by ship-boring has reviewed the hydraulic fracturing molluscs, showed significant benefit in $300 processes involved. It concluded that the fouling prevention and hence propulsion $200 risks associated with the extraction of shale efficiency. Figure 1.3 shows a subsequent gas can be managed effectively as long as $100 development of this in relation to one of the operational best practices are implemented later tea clippers, the Cutty Sark. $ and robustly enforced through regulation. Figure 1.3 Copper sheathing on Figure 1.2 Historical bunker prices the hull of the Cutty Sark Jul 07 Jul 93 Jul 00 Jan 11 Jan 97 Oct 12 Jun 10 Oct 91 Jan 90 Jan 04 Jun 03 Oct 05 Jun 96 Feb 01 Sep 01 Oct 98 Mar 12 Mar 91 Nov95 Dec 92 Aug 11 Apr 95 Apr 02 Feb 94 Feb 08 Dec 99 Dec 06 Sep 94 Sep 08 Apr 09 Mar 05

Mar 98 [Courtesy J.Hensher] Aug 97 Nov 02 Nov 09

[Platts] Aug 90 Aug 04 for 380 cSt marine fuel May 92 May 99 May 06

10 Royal Academy of Engineering Future ship powering options 11 Introduction

Figure 1.8 Medium-sized cruise ship [Courtesy A. Greig]

Gas turbines made their appearance in naval Figure 1.4 ss Turbinia 1.2.2 Operation [Courtesy J.S.Carlton] ships as a method of marine propulsion, Merchant ships are commonly designed and particularly for high-speed and sprint built to one-off designs or in small batches modes of operation. For naval propulsion to suit the trade in which they are engaged: the gas turbines were marinised versions In parallel with sail propulsion, the pace of one year later. This line of development this implies that, unlike the automotive or of aero-engines. Subsequently, however, mechanical and hydrodynamic propulsion paved the way for a small oil tanker, the aircraft industries, prototype testing is not for commercial ships, as well as the aero development increased rapidly during the Vulcanus, to become the first ship to be generally feasible. Cargo ships embrace a derivatives, the industrial gas turbine found 18th and 19th centuries (Pomeroy 2010). propelled by a diesel engine. It was followed range of types from large crude oil tankers favour in certain sectors of the industry These advances began with the steam by a much larger ocean-going cargo ship, making long international voyages to small due to its relative robustness in terms of engine which, at that time, comprised the Selandia in 1912. About this time, the cargo vessels port-hopping around a coast. Figure 1.6 Offshore supply ship operation and fuel usage. elementary boilers supplying reciprocating first gas-powered ship Holzapfel 1 also © Andrew Mackinnon The nature of their trade varies: the liner engines; for example, Jonathan Hull’s patent entered service. However, such was the follows fixed routes carrying cargoes, these Today the steam turbine has very largely involving a Newcomen Steam engine in growth of diesel propulsion that by 1939 days often in containers, while other ships given way to the diesel engine. This 1736. Steam-based propulsion technology some 54% of the fleet was powered in this wander the globe picking up cargoes where transition happened relatively quickly progressed to embrace the technical way. The performance of diesel engines has they can. These so-called tramp ships may and coincided with the breakthrough of advances developed by James Watt which progressively improved, demonstrated by carry bulk cargoes of grain, cement, iron ore turbocharging and heavy fuel burning in led to the Savannah in 1819 being powered a comparison of the thermal efficiency for or coal and may be fitted with deck cranes slow speed diesel engines which gave by a steam engine driving paddle wheels. these early engines in current operation, which render them independent of port these engines both the power and the fuel Towards the end of the 19th century when thermal efficiency has risen to values facilities. In contrast, some ships have a economy to become more efficient than the steam turbine was adopted, initially approaching 55% for slow speed engines. specialist function which might be servicing steam turbine propulsion. Consequently, demonstrated by Sir Charles Parsons in his offshore oil or wind farm facilities, (Figure steam turbines are normally only found celebrated vessel Turbinia at the Spithead The burning of heavy fuel was introduced 1.6); short sea, roll-on/roll-off ferries; today in nuclear powered ships and fleet review of 1897; (Figure 1.4). This single in the 1930s. Research started (Lamb 1948) natural gas (LNG) carriers, (Figure 1.7); submarines as well as some LNG ships; event was to totally change ship propulsion during the Second World War for its use in refrigerated carriers of food or cruise ships although in this latter case they are also since it heralded the end of steam marine diesel engines and it has become the acting as holiday destinations, (Figure 1.8). giving way to reciprocating machinery. In reciprocating marine machinery in favour standard fuel for the majority of seagoing Figure 1.7 A large LNG carrier © Mercator Media 2013 the merchant sector the general demise of of the steam turbine. ships today. Recently, however, local and Each ship type has evolved specialised hull steam plant has, in turn, led to a shortage of international legislation has begun to be and machinery forms which are adapted to qualified steam plant operators. Only nine years later, in 1906, the rms formulated and the focus is moving to their trading requirements. Consequently, Mauritania was launched and was propelled the more expensive lighter marine fuels innovative technologies are rarely suitable Developments with cruise ship technology by steam turbines developing 76,000 shp and the use of dual-fuelled engines. With for general application to all ships and a have led to the use of diesel-electric together with screw propulsion. Figure 1.5 these engines, different grades of fuel careful selection must be made based on propulsion arrangements. This is due to gives some impression of the development are burnt depending upon the prevailing the ship’s characteristics, available crew endeavouring to achieve low noise and which took place during that period in requirements within the emission zones. skills and the desired operational profile of vibration signatures, similar to steam terms of the sizes of the two ships and the In recent years, increasing oil prices have the ship. turbine-driven ships, combined with the installed power of their machinery. Eight prompted interest in alternative propulsion enhanced operational efficiency that is years later, the Transylvania became the options and changes in fuels for merchant The ownership of shipping assets is achievable with this mode of propulsion by first ship to use geared steam turbines to ships. Typical of these have been the frequently complex. It would not be utilising payoffs between propulsion and improve propulsive efficiency. burning of LNG in reciprocating engines, unusual for a ship to be built in China, using hotel loadings. wind-assisted propulsion, ducted propellers, investment finance raised in Singapore, In parallel with the arrival of the steam energy-saving appendages and interest in for an owner based in Athens who then Figure 1.5 rms Mauritania on the River Tyne turbine, Rudolf Diesel, in 1892, took out a nuclear power. devolves operational responsibility to a © Tyne Wear Archives Museum patent and ran his first reciprocating engine management company situated in Monaco.

12 Royal Academy of Engineering Future ship powering options 13 Introduction

Such an arrangement might involve a this environment, innovative technologies change and commercial shipping’s charterer in South America shipping goods should not be considered in a single-country the IMO’s 1.3 International contribution to levels. from the USA to Germany. The ship in sense or even in a Euro-centric way. Many International regulations question could very possibly be registered factors influence the take-up of ideas and • Standards of Training, Certification The international maritime community in the Bahamas and thus be subjected to technologies in the marine industry which Safety and Watchkeeping (STCW) sets operates in territorial and international the laws of that country. In this example include their initial cost and the commercial standards for the training for seafarer Management (ISM) waters across the globe and requires a the Bahamas is the vessel’s flag state while relationships between the shipyards, skills and qualifications. These regulatory regime which can properly serve the United States and Germany are, for the shipowners and the innovators as well as Code provides an are reflected in the certificates of this level of international complexity. The period of the ship’s stay in harbours there, the political aspirations of nations. It is, competency acquired by merchant international International Maritime Organisation, based referred to as port states. therefore, essential for the marine industry navy officers as they progress up the in London, is a limb of the United Nations to take a global perspective on these standard for the promotional ladder towards Master and and provides this forum together with a Based on gross tonnage, at the end of 2011 matters. Chief Engineer. safe management secretariat for flag state governments. In Panama and Liberia were the two largest this forum, observed by other interested flag states and in terms of ship numbers this At the end of 2011, the total world fleet, and operation In addition to these conventions, the IMO’s parties, suites of regulations are agreed, amounted to 12%, and 5% respectively of having individual deadweight tonnage in International Safety Management (ISM) of ships and revised and published as Conventions and the world’s cargo-carrying merchant fleet excess of 100GT, comprised 104,305 ships Code provides an international standard for pollution when ratified, implemented by states in over 100 GT. The United Kingdom, in 12th (IHS Fairplay, 2011) of which the cargo carrying for the safe management and operation of national laws which then apply to ships place, on the same basis accounted for fleet accounted for 55,138 ships and ships and for pollution prevention. prevention flying their flags. Frequently, IMO rules are 1.2%. If analysed in terms of the nationality represented a total deadweight of 1,483.1 made retrospective to an incident and the of the owner for ships over 1,000 GT, Japan Mdwt. During that year, 2,609 ships were The responsibility for governmental attainment of international agreement and Greece dominate with the United completed while 1,412 were either disposed application of IMO’s international rules may involve protracted implementation Kingdom in 6th place (IHS Fairplay, 2011). of or, in some cases, lost. This difference in the United Kingdom rests with the timescales in order to satisfy the concerns represented a net gain in world tonnage of Maritime and Coastguard Agency, which of nations. The marine industry has generally been 121.5 Mdwt and the average age of the fleet is a limb of the Department for Transport. cautious in its approach to technology in all was 19 years. This agency employs technical expertise The IMO Conventions most relevant to this but a few sectors. This is for many reasons, commensurate with this role and represents report are: including the use of new technologies in The composition of the cargo-carrying fleet the UK in several international maritime • Safety of Life at Sea Convention an extremely hostile environment. The based on deadweight is shown by Table fora. Its surveyors provide enforcement (SOLAS) has a broad coverage from cyclic economic nature of world trading and 1.1. On this basis it is seen that tankers and of regulations on UK-flagged ships and the safety aspects of ship structural its consequent influence on the finances bulk carriers account for 78% of the world constitute a port state control inspectorate construction, stability and fire protection of shipping companies, together with the fleet. Next in significance as a sector is the for regulation compliance by visiting ships. through to safety management constantly changing international political container fleet which amounts to a further and navigation rules. SOLAS is the scenarios under which the industry has to 13%. These three ship types account for The contraction of the European cornerstone of international maritime work are also contributing factors. Within 91% of the world cargo-carrying fleet. commercial shipbuilding and marine safety requirements, having been engineering industries has led to a initiated as a result of the Titanic disaster refocusing of technical activity in these and built upon over time so that today fields. Besides that which exists in the it has become a comprehensive safety Ship Type Proportion of the Sub-class Sub-class proportion navies and some shipyards specialising in cargo-carrying fleet (%) of cargo-carrying fleet (%) document. complex ships, the principal repository of Tanker 37 Crude oil carriers 24 naval architectural and marine engineering • Prevention of Marine Pollution Chemical tankers 6 knowledge largely rests with the principal Convention (MARPOL) applies LNG carriers 2 classification societies together with principally to the protection of the Products tankers 4 some major consultancy organisations, marine environment and embraces LPG tankers 1 universities and the professional contamination by oil, chemical spills, Bulk carriers 41 Dry bulk 40 learned societies. The classification sewage, marine species, garbage and Self discharging dry bulk <1 societies have progressively developed air pollution by engine exhaust gases. Dry bulk/oil <1 standards for ships’ hull and machinery The requirements are stringent and Other dry bulk types <1 design, construction and repair based national penalties for non-compliance Container 13 on programmes of continuing research often severe. A recent focus has General & refrigerated cargo 6 combined with accumulated experience been on addressing the international Table 1.1 Composition Ro/Ro and Ro/Pax 2 of shipbuilding and service operation. The of the world cargo fleet Cruise and passenger <1 community’s concerns about climate (over 100 Dwt) based on once pre-eminent technical position of Miscellaneous <1 dwt [(IHS Fairplay (2011)]

14 Royal Academy of Engineering Future ship powering options 15 Introduction

• International shipping 200 • International aviation 180 Domestic exc. road transport • 160 6% Road transport exc. car and taxis • 140 20% • Cars and taxis 120 5% 100

equivalent 26% 2 80

60

40 43% British and European shipbuilding and repair states with 54.6% of world merchant Figure 1.10 Total UK 20 Ships compare acted as the foundation for much of this shipping tonnage. Accordingly, Annex

transport greenhouse gas Million tonnes of CO 0 well in CO2 knowledge. However, these activities have VI entered into force on 19 May 2005. It emissions: 1990 –2009 1992 1996 1990 1994 1998 2002 2006 2000 2004 either transferred or are in the process of applied retrospectively to new engines [DfT] 2008 emission terms transferring to other geographical locations; of greater than 130 kW installed on with other forms chiefly to the Far East. Nevertheless, vessels constructed on or after 1st the major classification societies have January 2000, or which underwent a of transport offices in these newer centres of activity major conversion after that date. In which enables these technical knowledge anticipation of the Annex VI ratification, repositories to be continually enhanced. most marine engine manufacturers have Mode of transport relative CO2 index An alternative scenario is based on a been building engines compliant with the 1.4 Global context Aeroplane 398 statistical analysis of the United Kingdom 1.3.1 Emissions control under above standards since 2000. Small goods vehicle 226 of shipping transport greenhouse gas emissions over MARPOL Annex VI Large articulated truck 49 the twenty year period 1990 to 2009, • 2008 Amendments (Tier II/III) – Annex Ships compare well in CO2 emission terms (Figure 1.10). It is seen that the international During the 1990s, attention to air pollution VI amendments adopted in October Railway haulage 6 with other forms of transport. Using a large shipping component was around 6% in and global warming led to regulations 2008 introduced new fuel quality Large container ship 3 tanker as reference for transporting one 2009: the absolute quantity in terms of restricting the emission of the oxides requirements which commenced in Large tanker 1 tonne of cargo over one mile, Table 1.4 CO2 equivalent having remained broadly of nitrogen (NOX) and sulphur (SOX): July 2010; Tier II and III NOX emission shows the relative relationship between constant throughout the period under pollutants produced during combustion standards for new engines; and Tier I Table 1.4 Relative CO2 emissions of different modes of transport. These studies different modes of transport[MOL, 2004] review. in diesel engine cylinders. Subsequent NOX requirements for existing pre-2000 were completed some 10 years ago and amendments have included restrictions on engines. The revised Annex VI entered in the intervening time technology will Carbon efficiency has a strong relationship the emissions of ozone, particulate matter into force on 1 July 2010. By October have reduced CO2 emissions in each of the to ship size. Figure 1.11 outlines the and greenhouse gases. 2008, Annex VI was ratified by 53 sectors, consequently, today some variation approximate trend between the mass of countries, including the Unites States, in the absolute detail of the table can be CO2 emitted per tonne-mile and the size of The MARPOL Annex VI NOX emission which represented 81.9% of tonnage. expected. This will be particularly true ships, in this case plotted for container ships standards are arranged in three tiers: Tiers of the automobile industry where and crude oil tankers. Clearly, the trend I, II and III. The Tier I standards were defined The NOX limits apply globally, whereas at emissions control of engines has been observable is one of decreasing specific in the 1997 version of the Annex, while this time the SOX emissions requirements of particularly good. emission with increasing size of the ship. the Tier II/III standards were introduced by Annex VI vary depending on where the ship amendments adopted in 2008, as follows: is sailing. More stringent emission levels for

• 1997 Protocol (Tier I) – The 1997 SOX apply in certain Emission Control Areas. Protocol to MARPOL, which includes Currently there are four ECAs located in the Annex VI, became effective on 18 May Baltic Sea, North Sea, around North America 2004 when Annex VI was ratified by and the US Caribbean as seen in Figure 1.9. 80

70

60

50

40

30

20

per tonne-mile 10 2

Figure 1.11 Carbon gCO 0

efficiency of container ships 8+ 1–2 0–1 3–5 2–3 5–8 0–10 200+

and crude oil tankers 10–60 60–80 80–120

[Committee on Climate Change 120–200 (2011)] Container (‘000 TEU) Crude tanker ‘000 DWT)

Figure 1.9 Current emission control areas [Lloyd’s Register]

16 Royal Academy of Engineering Future ship powering options 17 Design Options

restrictions. The propeller open water the propeller efficiency for large full form ships, such 2.2 The ship system 2. Design options open water as tankers and bulk carriers, is generally relatively low, albeit that an optimum If a change to a ship’s power generation efficiency propeller has been designed for the method is contemplated, either as a is combined powering conditions prevailing at the departure from conventional practice or in aft end of the ship. In the case of faster terms of a retrofit, significant implications with the hull and more slender-lined ships, such as usually arise for the ship system. From efficiency, container and Ro/Ro ships, the propeller a ship owner’s perspective, it may be open water efficiency generally rises conceptually convenient to consider a relative rotative appreciably. However, the propeller open conventional diesel-propelled system efficiency and water efficiency is combined with the hull being replaced by an alternative propulsion efficiency, relative rotative efficiency and method and then expect the resulting transmission transmission efficiencies to give the overall system to operate and behave in the same 2.1 Ship energy This ship type has been chosen for Figure efficiencies to propulsion efficiency for the ship. way as before. However, looking more 2.1 because they form 64% of the world deeply into the desired solution may show considerations fleet as seen in Table 1.1. Such a ship give the overall When poor weather is encountered, that to swap one prime mover option for could be expected to comprise a slow propulsion further energy losses occur. These arise another requires the interfaces to the other speed diesel engine directly coupled to To achieve full potential efficiency and from the added resistance of the hull due ship sub-systems to be in the same place or a fixed pitch propeller. From the figure it efficiency for environmental benefits a ship must be to its interaction with surface waves and aligned in the same way. This, if achievable, is seen that from the total energy input considered as an engineering system within the ship underlying swell. Additionally, the wind will minimise cost and ease the transition to the machinery system from the fuel, its intended operational profile. This implies acting on the ship’s exposed surfaces acts process. only around 27% is actually available that the design, operation and maintenance as a further source of resistance. at the ship’s propeller. However, there aspects of the ship have to be considered To ascertain the viability of alternative are a number of options to enhance the as an integrated system. More specifically, propulsion solutions, the whole market overall efficiency and energy available for the integrated design has to embrace, opportunity must be analysed in a systemic propulsion purposes; for example, exhaust within a single system, the traditional and structured manner. In contrast to heat recovery within certain constraints disciplines of naval architecture, marine and many current design solutions which such as the dew point of aggressive electrical engineering together with control have historically evolved, the discipline of chemical species in the exhaust gases, and technology. systems engineering, (Appendix 5), enables low grade heat from cooling water systems. a wider perspective to be taken when Typical energy flows in a ship are illustrated radical departures from traditional solutions For merchant ships the propeller is usually in Figure 2.1 for a tanker or bulk carrier are contemplated. The design life cycle designed to give high efficiency during before any energy saving measures is can be divided into four stages: assembling operation, consistent with any vibration contemplated. stakeholder requirements; exploring the considerations and operational profile system meta-solution to find the best model for success; progressing the design based To ascertain the viability of on the requirements and, finally, defining and analysing the system to ensure it meets alternative propulsion solutions the original requirements. Fundamental to this design process is the desired ship’s Losses in exhaust, cooling, the whole market opportunity friction, processes, etc operational profile and the perceived must be analysed in a systemic and tolerance on this profile necessary to meet structured manner market fluctuations. Furthermore, the fluctuations in daily ship and fuel costs that might be anticipated together with the operational profile should be used to define Propeller losses a design space within which the ship system Losses in shaft line can be progressed. 100% Input Thrust Power = Figure 2.1 Typical Thrust x Ship Speed power utilisation in a tanker or bulk carrier Propeller Shaftlline Engine

18 Royal Academy of Engineering Future ship powering options 19 Design Options

procedure. However, certain ship types, 2.3 Energy Efficiency whatever their size, are for the time being Design Index excluded from Index compliance and these are diesel-electric and turbine-driven ships; fishing vessels; offshore and service vessels. The Energy Efficiency Design Index (EEDI) is a developing ship design parameter which Full implementation of the EEDI-based seeks to govern the CO2 production of ships system is to be achieved within a phased Picture of carrier taken by crew in storm conditions in relation to their usefulness to society. process, not dissimilar to the MEPC Annex It is one of three initiatives developed by VI requirements for NO emissions. To the IMO MEPC Subcommittee: the others X An account of a capesize bulk carrier in a storm (Cooper 2012). facilitate this, a reducing factor will be being the Energy Efficiency Operational applied to the ship type reference lines and Index (EEOI) and the Ship Energy Efficiency “… in a Storm Force 10/11 with 8 to 10 metre swells,… We managed to the reducing factor will vary with respect to Management Plan (SEEMP). The EEDI, maintain about 85% of available main engine power for the 24 hours that we the phase implementation time intervals; regarded by some as an imperfect were hove-to. It was just about enough to keep us from falling too far off the currently set at 2013–2017; 2018–2022 and parameter, in its simplest terms is the ratio wind and seas. We lost about 80 miles that day, with us making two or three 2023–27. In each of these periods the factor between the cost to society expressed as knots astern. will be set to a prescribed value such that the carbon dioxide production potential of the Required Index value can be reduced “This saga could have a different ending if we had been trapped on a lee shore the ship and its benefit to society in terms in steps. or in confined waters… of its cargo capacity and speed for some “…there is no way I could have turned that vessel through the wind with its nominal design point. The CO2 production The Actual EEDI, calculated for the proposed potential comprises four components: high accommodation and large square funnel. The main engine governor was ship design, must then be shown to be • The carbon dioxide directly attributable giving us the maximum power available for the conditions and although the less than or equal to the Required EEDI. to the ship’s propulsion machinery. Chief Engineer could have overridden the governor and increased power, the The computation of the Actual EEDI for a • The carbon dioxide arising from the danger would have been burying the bows repeatedly into the very heavy subject ship design is achieved through the auxiliary and hotel power loads of swell with a high risk of damage to air pipes, stores and rope hatches, and even use of the relationship defined in Appendix the ship. to the forward hatch covers, not to mention overloading the main engine with 8. This includes the four CO -producing or • The reduction of carbon dioxide due 2 a resultant loss of power.” regulating components in the numerator There is a to energy efficiency technologies. while the denominator is essentially the For example, heat recovery systems. considerable product of ship speed and cargo capacity. • The reduction of carbon dioxide due range of to the incorporation of innovative • To increase the ship’s deadweight by There is a considerable range of energy- Examination of the Actual EEDI defining energy efficiency technologies in the energy-saving changes to or enhancements in the saving technologies available for ships. equation suggests a number of ways that design. Typically, these might include design. These broadly relate to primary propulsion compliance with the requirements might be technologies the introduction of or novel and hydrodynamic options. However, there achieved as well as options for reducing the hydrodynamic devices. available for If the option to install engines into the ship is also an emerging class of devices which value of the Index for a given ship. Typically of a lower power rating were adopted, this are dependent on aerodynamic principles. these are: ships. These The EEDI parameter governs the ship would be a relatively simple and effective The deployment of these technologies in design philosophy and the particular value broadly relate way to reduce the value of EEDI. Such an specific instances is dependent on the ship’s • The installation of engines, subject to calculated for a proposed ship design has to option, however, begs the question as to type, size and operational profile, with in certain minima, in a ship with less power to primary be verified by an independent organisation whether the ship would then have sufficient some cases sociopolitical considerations, and, thereby, the adoption of a lower against defined criteria, expressed as propulsion and power to navigate safely in poor weather as well as on the ship’s hull form. This is ship speed. reference lines, to obtain certification. conditions. The description in the above further complicated for some existing ship • To incorporate a range of energy- hydrodynamic To define the reference lines parametric text box illustrates a situation where a designs in relation to any other energy- efficient technologies in order to studies were undertaken embracing options capesize bulk carrier was caught in a storm saving devices that have been previously minimise the fuel consumption for a variations in size for the ship types being (Cooper 2012). Another potentially dangerous fitted: some being incompatible with each given power absorption. considered. At present the Index is applied situation is to be found in manoeuvring other. In all cases, however, a total systems • The use of renewable or innovative to the design of ships above 400grt and satisfactorily in restricted channels or engineering approach should be undertaken energy reduction technologies so as to will include tankers, gas carriers, container harbours under a range of adverse tidal and to avoid disappointing results. minimise the CO production. ships, cargo ships and refrigerated 2 weather conditions. However, in the latter • To employ low-carbon fuels and in so cargo ships. These ships will require an context, tugs might normally be employed. doing produce less CO than would International Energy Efficiency Certificate 2 otherwise have been the case with (IEEC) to show compliance with the EEDI conventional fuels.

20 Royal Academy of Engineering Future ship powering options 21 Primary propulsion options

Uaxial

-1 1 (m s-1) Figure 3.2 Flow studies

in diesel injector nozzles Liquid (%) 3. Primary propulsion [edited from Andriotis et al. options 2008] 0.2 0.9 fuel oil consumption in medium speed • Humidification of inlet air or water four stroke engines. Typical of these injection developments have been flow studies in • Emulsification of fuels injector nozzles with particular reference to the effects of cavitation on fuel atomisation Secondary methods and spray structure and repeatability; • Selective catalytic reduction systems

(Figure 3.2). • Low sulphur fuels for SOX limitation • Exhaust gas scrubber systems both using In the context of this report, primary However, since the early 1990s, the drivers direct seawater scrubbing or closed Since the 1960s propulsion options relate to the sources CONVENTIONAL for diesel engine development changed. circuit freshwater scrubbing and 70s the and modes of developing power to propel PROPULSION The concept of reduction of NOX and SOX, the ship. In contrast, further propulsion involving primary and secondary processes, The primary methods of limiting NOX development of considerations, Section 4 considers the OPTIONS AND without detriment to fuel consumption production in the combustion process are slow and medium means of converting that power into useful FUELS became a major priority to meet the limits directed towards optimising the engine speed diesel and efficient ship propulsion. imposed in current and future emission parameters which include reducing the peak 3.1 Diesel engines control areas. The result has been a number temperature and duration of the process, by engines has been of developments in marine diesel engine much higher-pressure fuel injection over a technology which include: shorter period, accurate timing and control driven by the Today diesel propelled machinery is the of the injection, the use of Miller inlet valve need for better principal means of marine propulsion. Primary methods timing and higher-pressure turbocharging. Engines are broadly classified into slow • Low NOX combustion, adjustable This has led to current developments in fuel economy speed two stroke; medium speed four camshafts two-stage turbocharging for even higher stroke; and high speed four stroke engines; • Variable inlet valve control operating pressures but with significantly (Figures 3.1 (a & b)). While some ships, due • Improved combustion chamber design lower fuel consumptions, thereby making to their design and operational profile, use • Higher boost pressures way for further efficiency improvements in either slow or medium speed diesel engines • Greater mechanical strength in engine engines. as the principal mode of propulsion, most architecture ships are fitted with additional medium • Development of two stage turbocharging Debate among engine builders exists a. Low speed marine diesel engine, the Wärtsilä RT-flex82T version B main engine© Wärtsilä or high speed diesel engines to drive • Exhaust gas recirculation concerning the most effective method generator sets for auxiliary power purposes. • Waste gate technology for the various engines. Exhaust gas Additionally, all merchant ships have an • Sequential turbocharging recirculation is a method which can be emergency means of generating electrical • Variable turbine geometry deployed for NOX reduction purposes in power as required by SOLAS.

Since the 1960s and 70s the development Miller Cycle of slow and medium speed diesel engines In the Miller Cycle the charge air is compressed to a higher pressure than is needed has been driven by the need for better fuel for the engine cycle. A reduced filling of the cylinders is then controlled by suitable economy. The result has been increased timing of the inlet valve which then permits some expansion of the charge air to stroke/bore ratio, peak pressures and mean take place within the cylinders. This expansion process allows cooling of the charge piston speeds in slow speed, two stroke at the beginning of the cycle whereupon its density increases. This results in the engines to achieve significant reductions in potential for the power of a given engine to be increased. The practical application specific fuel oil consumption. of the Miller Cycle, however, requires a turbocharger capable of achieving high

b. Medium speed diesel engine © Wärtsilä compressor pressure ratios in association with high efficiency at these conditions. Similar improvements in turbocharging While initially developed with the aim of increasing engine power density, it has Figure 3.1 Typical marine efficiency, fuel injection technology, been found that the Miller Cycle can be used, by reducing cycle temperatures at

propulsion diesel engines brake mean effective pressure and firing constant pressure, to reduce NOX formation during combustion. pressures have brought down specific

22 Royal Academy of Engineering Future ship powering options 23 Primary propulsion options

slow and medium speed diesel engines. In control systems, and the selective catalytic differences between an ultra-long stroke is to install secondary abatement systems the case of two stroke, slow speed engines, reduction elements which may replace the A new class of engine and a more traditional engine. for the removal of sulphur from the exhaust development programmes have been normal silencer. ultra-long stroke after combustion. This requires the use of undertaken with exhaust gas recirculation To reduce fuel consumption there has been high volumes of seawater or, alternatively, systems over the last 20 years or so. The Green Ship of the Future Project engines has a tendency to run large marine engines a smaller volume of freshwater with a Among these have been in-service trials undertook a retrofit study for a 38,500 been introduced at part load. While such restrictions have dosing of caustic soda. There is also a conducted onboard the Alexander Maersk dwt tanker powered by a slow speed diesel largely been confined to continuous powers further process which is based on the which have made useful contributions to engine which was planned to spend 13.5% into the marine above 60% of maximum continuous rating ionisation of seawater. The third choice is the understanding of these systems. With of its time in an environmental control propulsion (MCR), more recently in container ship the use of LNG as a fuel, which is principally the EGR method of NOX reduction some of area (Green Ship of the Future Project, 2012). operation these limitations have been as methane (CH4); see Section 3.3. However, the oxygen in the scavenged air is replaced Three options were considered: the use market. These low as 10% MCR. To achieve these very methane is a greenhouse gas and if with CO2 since carbon dioxide has a higher of low sulphur fuel; placing an exhaust engines have a low loads the lubricating oil supply has to significant methane slip occurs within the heat capacity which reduces the peak gas scrubber in the system or using LNG be reduced together with the introduction engine combustion or bunkering processes temperatures within the cylinders. In- as a fuel. The low sulphur fuel option lower design of engine tuning methods for part and low this aspect can be enhanced. service trials have shown that components introduced some lubrication issues. The speed and if used load. Of significance in this context are in the system such as the piston rings, exhaust scrubber alternative, based on exhaust gas bypass; variable turbine area; EGR blowers, the water mist catcher and using heavy fuel oil after 2015, required a with an optimum engine control timing and high-pressure Methane Slip control systems have performed well. Water new funnel layout due to the introduction large diameter tuning. Methane slip is a cause for concern injection into the cylinders at the time of the scrubber together with its associated because of the properties of methane, of combustion and humidification of the machinery and new tanks. In the latter case, propeller at these In the marine industry, while fuels are when considered as a greenhouse gas, inlet air is also helpful in reducing the NOX the LNG fuel usage required new piping and low rotational classified into different grades there are are 21 times more potent than CO2 content of the exhaust gases from slow a fuel supply system together with new no standard specifications. Consequently, (IPCC 1995). It may derive from two speed engines. Several methods have been LNG tanks; in this case two 350 m3 tanks speeds, the fuel composition and quality can be variable sources, the first being operational designed and tested for this purpose by the mounted on deck. The associated costs, overall ship when bunkering in ports around the world. emissions while the second derives various manufacturers of slow and medium based on industry quotations, for these While slow speed engines are reasonably from engine emissions. In the first speed engines. last two options were estimated at 5.84M propulsion tolerant of fuel variations, medium speed case, this may be from the venting US$, 50% of which was for the scrubber efficiency can be engines tend to be less so (Wilson, 2012). of methane to atmosphere during An additional secondary method of NOX and auxiliary machinery, and 7.56M US$ However, that the fuels lack specification refuelling while in the latter case reduction to meet the Tier 3 targets is respectively. In the LNG case, the tanks and enhanced does not imply that the diesel engine of engine emissions this relates to selective catalytic reduction. SCR systems machinery conversion were costed at 4.38M combustion processes cannot be managed. unburnt or incomplete combustion of can be useful when working in emission US$ with 40 days’ off-hire time. In contrast Indeed, guidelines for fuel ignition and methane passing through the engine control areas; however, cost becomes the scrubber option required an estimated quality to assist in the fuel management system. In the context of engine a critical factor when deciding on the 20 days’ off-hire time. processes have been developed (CIMAC emissions, methane slip may be due most appropriate system. In the case of 2011). Since the marine supply chain has to the engine concept, engine design, medium speed, four stroke engines it is A new class of ultra-long stroke engines been contaminated to a small extent its operational profile or due reported that SCR systems offer an 80% has been introduced into the marine with biofuels, (Section 3.2), in the case of to maintenance.

improvement in NOX reduction (Troberg, propulsion market. These engines have distillate fuels, additional management 2012). One approach relies on the injection of a lower design speed and if used with an practices need to be put in place to control ammonia into the exhaust gas flow, usually optimum large diameter propeller at these this aspect. Some potential advantages and in the form of a urea solution. This reacts low rotational speeds, the overall ship disadvantages of the technology:

with the NOX exhaust component at the propulsion efficiency can be enhanced. This To control the sulphur in the fuel the ship Advantages surface of the selective catalytic reduction hydrodynamic benefit can then be coupled operator has three principal choices. The i. Diesel engine technology is a well-

elements to form N and H2O. This method, with the enhanced fuel oil consumption first is to bunker low sulphur fuels either understood and reliable form of however, requires space to be allocated in characteristics of the engine. Table 3.1 wholly or partially, so that in the latter marine propulsion and auxiliary power the ship for the urea storage, the dosing and shows the quoted fuel consumption case the ship can switch to a low sulphur generation technology. fuel when in an ECA. This, however, has ii. The training of engineers to operate implications for fuel storage and handling diesel machinery is well known and systems on the ship; changeover processes; facilities exist for the appropriate levels Engine parameter K98 ME engine S90 ME engine the technology of engine and boiler fuel of education. Stroke (mm) 2660 3260 injection systems and the choices of iii. Engine manufacturers have well- Table 3.1 Comparison lubricating oils, etc. An alternative solution established repair and spare part between an ultra-long Speed (rpm) 97 84 stroke and a traditional Specific fuel oil consumption (g/kWh) 174 167 engine (Jakobsen 2012)

24 Royal Academy of Engineering Future ship powering options 25 Primary propulsion options

networks around the world. of storage, fuel handling, health, safety aqueous and alcohol-weak gasoline phases iv. Diesel fuel in all grades has a worldwide 3.2 Biofuels Using biofuels and the environment. Additionally, the to form which then create the potential distribution network and is easily derived from influence on exhaust emissions, lubricating for combustion problems. Moreover, the obtainable. Living systems comprise a collection of oil performance, material compatibility and former phase will collect at the bottom of v. Many primary and secondary methods cells, genes and proteins which permit them natural long-term storage were also considered. the storage tanks in the ship and is likely for reducing emissions which are to grow and replicate. Understanding these sources such as In part, these trials were stimulated by the to be very corrosive. Furthermore, while perceived to be harmful are now complex systems has occupied biologists current practice within the automotive bioethanol behaves as a solvent which available. Furthermore, there is a and chemists for much of the last century vegetable oils industry of blending FAME into diesel effectively cleans dirty storage tanks and continuing programme of research and and has resulted in first generation biofuels would require fuels intended for the automotive sector fuel lines it becomes contaminated during development being undertaken by the with work continuing on subsequent which, therefore, enhances the probability this process. engine builders. generations. The first-generation of a land area of cross-contamination with the marine vi. Diesel engines are generally able to cope biofuels in widespread use are biodiesel equivalent to distillates. This probability is further To power the current worldwide fleet of with part load, transient and dynamic and bioethanol. Biodiesel is produced influenced by the EU marine fuel sulphur merchant ships, it is estimated that it would that of about 18 behaviour in a seaway. from animal fats and vegetable oils such requirements at berth of 0.1% and inland require around 7.3 x 10 J/year (MacKay, as coconut, palm, rape seed, soybean and twice the size the waterways of 0.001%. The Maersk Kalmar 2011). Using biofuels derived from natural Disadvantages tallow. These fuels are generally known United Kingdom trials showed that while the automotive sources such as vegetable oils would i. Diesel engines produce CO2 emissions as Fatty Acid Methyl Esters (FAME) and biodiesel formulation was not optimal require a land area equivalent to that of

as well as NOX, SOX, volatile organic are produced by reacting the vegetable oil for ship propulsion, the fuel was usable about twice the size the United Kingdom compounds and particulate matter. or animal fat constituents with an alcohol during the trials. Furthermore, concerns (MacKay 2011). Oilseed rape, when used to Therefore, they have to be made such as methanol. In contrast, bioethanol is over microbial growth were shown not produce biodiesel, has a power per unit compliant with the MARPOL Annex VI produced by fermenting renewable sources to be an issue within the confines of the area potential of about 0.13W/m2 (MacKay, requirements and included during an of sugar or starch, typically cassava, corn, trial; however, further investigation of this 2009). Notwithstanding the size of the land EEDI evaluation of the ship. sorghum, sugar beet, sugar cane, and aspect was considered necessary in the required for this purpose, there is also the

ii. The SOX emissions are a function of the wheat. future. Similarly, as engine running and ethical question of whether it might be sulphur content of the fuel used in the lubricant interaction times were relatively better to deploy such agricultural areas for engine and to comply with regulations There are a number of chemical short within these trials, to arrive at world food production. an abatement technology has to be compositions of FAME raw materials. definitive conclusions further sea trials and employed. The blend levels used result in fuels having test bed running were recommended. The science of synthetic biology, in the iii. There is now some contamination of the some variability in their cold temperature context of fuels, has focused on the marine fuel supply by first-generation performance, degradability and stability. The processes involved in production of biodiesel and bioethanol. In biofuels which needs to be carefully In turn, this has implications for handling, production from sugar or vegetable oils the longer term more advanced biodiesel managed on board ships. storage, treatment, engine operations and are not particularly efficient and waste fuels are likely to be developed together emissions. a significant quantity of the biomass or with the associated synthetic biology-based organic matter. The underlying reason processes for efficient fuel production FAME is able to hold high levels of water for this is that stalks and leaves, although in significant quantities (Royal Academy of in suspension and water may also induce rich sources of sugars, are discarded Engineering 2009). Alternative synthetic fuels hydrolytic reactions which break down because they are difficult to break down based on the branch-chain higher alcohols the FAME to form fatty acids. These are with present technology. Consequently, and new types of E-coli as well as other corrosive and can attack metal surfaces. an efficiency enhancement for these types of microorganisms, such as yeast, Alternatively, if the water separates out processes must await the development of may make their appearance. In the case of of the FAME fuel this may give rise to the necessary enzymes. algae-derived fuels, these are generally no microbiological growth which can then lead more efficient at photosynthesis than land- to the filter clogging. Corrosion problems In contrast to FAME the bioethanols are based plants; however, this efficiency can have also been experienced when used with single chemical compounds which are be enhanced by water heavily enriched with

marine diesel engines. colourless, hygroscopic, miscible with water CO2. Even with this efficiency improvement, and are volatile. However, since bioethanol algae-derived fuels are unlikely to satisfy A recent trial centred on the container is hygroscopic and highly soluble in water, the demands of the worldwide marine ship Maersk Kalmar (Lloyd’s Register 2011) small quantities of water can be dissolved industry. endeavoured to evaluate the impact in fuel blends containing bioethanol and of Fatty Acid Methyl Esters and marine separation of the ethanol can result when A further alternative fuel for compression- distillate fuel containing FAME. The focus critical levels of water take-up are reached. ignition engines is di-methyl ether (DME). of this trial was undertaken in the contexts This facilitates alcohol-rich water/ethanol This can be produced from the conversion

26 Royal Academy of Engineering Future ship powering options 27 Primary propulsion options

to develop the of a number of sources including natural the demand from the marine and other 3.3 Liquid natural gas process, due to the compression ratios and gas, coal, oil residues and biomass. DME is markets. combustion temperatures for CH4, reduces same level of relatively easy to handle; indeed it is not iii. Di-methyl ether shows some potential (LNG) NOX production by around 85%. This meets dissimilar to LPG, because it is condensed benefits as an alternative fuel. the MARPOL Annex VI, Tier 3 limits without energy as when pressurised above 0.5MPa and iv. Synthetic fuels can be derived from the need for selective catalytic reduction. The burning of natural gas in internal it is thought to be both non-toxic and syngas, created by partial combustion Furthermore, since sulphur is absent from conventional combustion engines is not a new concept. environmentally benign. DME has a high of a wide range of biomass feedstocks. the fuel, no SO emissions are produced. In Neither is its use associated with diesel- X diesel fuels, cetane number which may lead to a better the context of the EEDI the use of LNG as a electric propulsion or mechanical drive mixing with air in the engine cylinder Disadvantages fuel with its associated CO savings would di-methyl ether systems for ships. A significant step in 2 (Arcoumanis et al 2008) while its high oxygen i. With the first generation of biofuels, reduce the Actual EEDI for a ship by 25%. the adoption of natural gas as a fuel requires a higher content can achieve smokeless combustion biodiesel and bioethanol, problems has been the Dual Fuel Diesel-Electric through the low formation and oxidisation have been experienced when used in When liquefied, the storage space required injected volume systems on LNG carriers that are either rates of particulates. Notwithstanding the marine environment. However, this for natural gas is about four times higher being built or already in service. However, of fuel due to its these potential benefits, to develop the may not be the case with the second- than for conventional fuels. There is also ship operating philosophies have varied same level of energy as conventional diesel generation biofuels. a need for well-insulated tanks and a lower density between companies. Some operators fuels, di-methyl ether requires a higher ii. At the present time, significant land safe area in case of accidental spillage. prefer to use conventional heavy fuel oil and combustion injected volume of fuel due to its lower areas need to be devoted to first- Consequently, the required storage space when its cost is lower than the commercial density and combustion enthalpy. Moreover, generation fuel production to satisfy on a vessel will be greater than that needed enthalpy value of boil-off gas from the LNG tanks; or DME-fuelled systems require lubricity- the marine market. for conventional fuel oils which may impact when the ship is running with limited LNG enhancing additives and anti-corrosive iii. The effective greenhouse gas emissions on the available cargo volume for the ship. on board in the ballast condition or during sealing materials to maintain leakage-free of all types of biofuels, including fuels Clearly, however, there are many alternative lay-up. In this case the need for a shipboard operation. Additionally, if DME were used derived from biomass, is currently an tank arrangements that might be adopted re-liquefaction is limited. However, it can as a fuel some attention would have to be area of active research. It is possible that as well as a number of system alternatives be installed so that on the occasions when paid to the optimisation of the fuel injection the available global resource of biomass by which LNG can be utilised for propulsion the boil-off cargo exceeds the ship’s fuel equipment to allow for the low density, low and biofuels may be inadequate to purposes. One option comprises a slow requirements the additional boil-off fluid lubricity and corrosiveness of the fuel. supply shipping. speed, gas injection engine with LNG can be returned to the cargo tanks. By iv. The production processes used at delivered under pressure to the engine. way of contrast, a large fleet of ships has Research has suggested that di-methyl present to convert sugars and vegetable The fuel is then vaporised at the engine, been built using the opposite philosophical ether when used in compression-ignition oils are not particularly efficient, but thereby making the process safer, easier to viewpoint. These ships operate on heavy engines, despite its disadvantages, is able research is underway to enhance this install and operate rather than delivering fuel oil and use a large liquefaction plant to provide high thermal efficiency with low aspect. high-pressure natural gas from the fuel to reliquefy all of the boil-off LNG: this combustion noise and NO levels together v. Further work is necessary to examine tanks. With this arrangement, high gas X auxiliary plant also runs on heavy fuel oil. with soot-free combustion. Consequently, aspects of storage and handling of these injection pressures are needed so as to Consequently, these latter ships deliver all this alternative fuel merits further study. fuels, and their impact on health, safety overcome the cylinder pressure in the upper the cargo loaded and use heavy fuel oil for However, to deploy it in the marine industry and the environment. part of the piston stroke as well as being the ships’ operational energy needs. on a worldwide basis would require a fuel vi. The presently perceived disadvantages able to get the required mass of gas into supply chain network to be developed which of di-methyl ether in terms of its lubricity the cylinder within a short time interval. An Given the recent volatility of world oil could sustain the needs of the industry. and corrosive issues together with alternative arrangement is a low-pressure prices the price of LNG in terms of net This latter issue would be lessened if it creating sufficient production and supply two stroke dual-fuel engine. This has the energy value has been consistently lower were used for short sea and inter-island require resolution. low pressure LNG gas admitted by valves by a significant margin. Furthermore, the type services. around the cylinder at the bottom of the availability of LNG is growing at a fast rate stroke which is then ignited by pilot fuel at from both conventional and shale gas Some potential advantages and the end of compression. A further option is reserves. Consequently, the attractiveness disadvantages of the technology: the established DFDE system used on LNG of LNG as a marine fuel, subject to the Advantages carriers which has now also been deployed logistical hurdles being overcome, has been i. Biofuels are potential alternatives to on a passenger ferry. In another context, growing in strength. conventional fuels. if a cruise ship used LNG as a propulsion ii. Synthetic fuels based on branch-chain fuel, evaporating the fuel could be used The principal constituent of LNG is CH4 higher alcohols and new types of to provide cooling in the air conditioning which, when used as a fuel, reduces CO2 algae and other microorganisms are a system. emissions by around 25%. Additionally, the medium- to long-term possibility, given lesser amount of nitrogen in the combustion that production volumes can satisfy

28 Royal Academy of Engineering Future ship powering options 29 Primary propulsion options

In cases where a ship is lying at anchor or There are many land-based fuel oil burning Unlike the current diesel bunkering ii. The benefits in terms of CO2, NOX, SOX There are many delayed in port and a reliquification plant power plants that have been converted to infrastructure for the majority of seagoing and the other emissions are significant. land-based is not fitted, then methane may have to run on gas due to restrictions on emissions ships, there is presently a lack of a similar iii. Designs for suitable marine propulsion be vented or burnt off to maintain tank having been imposed in the country of system for the supply of LNG to support the machinery systems exist. fuel oil burning pressures at acceptable levels. This would operation and/or where the price and operation of LNG-fuelled ships. However, iv. It is relatively easy to convert many power plants result in reduced operational efficiency and availability of gas is more favourable. a number of major commercial ports on existing marine engines to burn LNG. add to the global warming burden. Similar conversions are feasible on ships. the world trade routes have LNG terminals v. Currently LNG fuel is considerably that have been A recent example is the chemical carrier in the vicinity which serve land-based cheaper than the conventional range of converted to run The coldness of LNG can be used to cool mv Bit Viking which had its twin diesel consumers and these facilities might be marine fuels. the inlet air of a prime mover to 5°C. For engines converted for operation in the adapted to additionally serve the marine on gas… similar a gas turbine this is particularly effective Baltic and Norwegian waters on LNG. The community. This would require additional Disadvantages conversions are and enables the turbine to be run at 110% conversion process included the cylinder financial investment as well as the provision i. Methane slip has to be avoided during of its rated efficiency, even when ambient heads and liners, pistons and rings, the of a bunker fleet or safe bunkering jetties. the bunkering and combustion processes feasible on ships temperatures would otherwise produce connecting rods and turbochargers. In Indeed, some ports already have plans of new and in-service engines since an inlet temperature of 38°C. Such an inlet addition, gas rails and admission valves for such investment, typical of which is this is damaging in the context of temperature would imply running at 73% together with a pilot fuel system were Singapore, but rather more supply ports greenhouse gases. efficiency which is a gain of 50% overall. required. For this, in the case of the Bit would be required before LNG-fuelled deep ii. There is a general lack of a worldwide (TICA 2012) Viking, two 500m3 storage tanks were sea ships could be considered totally viable. bunkering infrastructure at present. mounted on the open deck giving the ship In Europe a second jetty is being built in iii. LNG requires a heat source to evaporate Dual-fuel engine experience of well over 12 days of operation at 80% load between the port of Zeebrugge to accommodate it to form the gas. As well as using the a million hours shows that times between bunkers. More recently, in December 2012, ships between 1,500m3 and Q-Flex sizes inlet air to the prime mover, it may be overhauls are extended and component an order was placed for a pair of liquefied and Antwerp already bunkers LNG-fuelled possible to use a heat exchanger with lifetime is longer; the combustion space in natural gas-powered Jones Act 3,100 teu inland waterway barges. As such, the LNG sea water, but some fuel is likely to be the engines has remained much cleaner and containerships. These ships are dual-fuel bunkering distribution network will embrace needed to be burned to provide this low- products of combustion in turbochargers vessels and are planned for delivery in 2015 Scandinavia, Belgium and The Netherlands grade heat. and lubricating oils are much less of a and 2016. The ships, which are reportedly with further plans developing. In the case problem. more expensive to build, are planned to of short sea ferry or inter-island type operate along the west coast of the United routes, then either bespoke local terminals Offshore supply vessels and ferries have States of America, which falls within an ECA, or supply by road tanker may provide a now been built to operate on LNG where as well as during one third of a Florida- solution. 3.4 Gas turbines the availability of the fuel exists: Figure 3.4 Puerto Rico voyage which is also is in the shows the example of the MF Fanafjord ECA. For these ships it is planned to use LNG Since classification society rules already Gas turbines were first introduced into which operates a short sea crossing in a as the primary fuel at all times, with diesel exist for the burning of LNG fuel in ships and warship propulsion in the 1950s to facilitate Norwegian Fjord and uses spark ignition serving as backup. coupled with the design and operational high speed sprint modes of operation since gas engines. experience having been satisfactory to their power density was high. A further date, there is little of a technical nature that operational advantage was the relative ease would prevent the adoption of LNG as a with which gas turbines could be started marine fuel. Any constraints would largely and stopped which gave rapid access to high derive from commercial considerations and levels of power. Gas turbines can be used relate in significant measure to the likely either in purely mechanical propulsion drive future price differentials between LNG and configurations or alternatively to generate conventional fuels as well as availability electricity, which is then used by electric at ports. drives to propel the ship. This gave rise to a variety of hybrid powering arrangements Some potential advantages and involving combinations of gas turbines disadvantages of the technology: with steam turbines (COSAG); with diesel Advantages engines (CODAG) and with diesel generators i. LNG fuelling of reciprocating engines (CODLAG) to accommodate the evolving as a known technology and service power requirements of a modern warship: experience, albeit limited at the present typically loiter, towed array deployment, time, has been satisfactory. cruise and sprint modes. Figure 3.4 MF Fanafjord: an LNG fuelled ferry [Courtesy A. Greig]

30 Royal Academy of Engineering Future ship powering options 31 Primary propulsion options

Introduction of the gas turbine into the of just over 40%. Consequently this fits In the 1950s Shell merchant service was more gradual by the power requirements of a number of experimented comparison with naval applications. Apart merchant ship types and sizes. The WR21 from early full-scale hull resistance research was a further development in marine gas with a gas turbine exercises using the Clyde paddle steamer turbine technology with variable inlet in the tanker, Lucy Ashton at the end of its commercial turbine stator vanes and incorporating service life, there were a number of early both compressor inter-cooling and exhaust Auris, while the applications of gas turbines. In the 1950s heat recuperation technologies. This liberty ship John Shell experimented with a gas turbine in thermodynamic arrangement was designed the tanker, Auris, while the liberty ship John to deliver low specific fuel consumption Sergeant was Sergeant was retrofitted with an industrial together with a thermal efficiency in the Figure 3.6 ns Savannah [Courtesy J.S. Carlton] retrofitted with gas turbine. Then around 1968 the RoRo region of 43%. This engine is used as a ship Adm W.M Callaghan was built having source of power for the Type 45 destroyers an industrial gas two aero-derived Pratt & Whitney FT4 of the Royal Navy. Additionally, the WR21 turbine gas turbines and leased to the USN Sea has an enhanced part-load performance. Some potential advantages and OTHER PROPULSION Lift command. In 1971 the containership disadvantages of the technology: Euroliner also featured two Pratt & Whitney Gas turbines have the advantage of low Advantages TECHNOLOGY FT4 gas turbines and sailed between the weight when compared to their diesel i. Gas turbines represent a proven high OPTIONS US and Europe. The twin screw high-speed engine equivalents: typically the MT30 power density propulsion technology. ferry Finnjet in Baltic Sea followed during unit weighs about 28 tonnes including ii. Their low weight gives considerable 1977 and then more recently with cruise the enclosure and ancillary components. flexibility when locating them in a ship. 3.5 Nuclear ships including the Millennium Class and This weight advantage, therefore, allows iii. NOX emissions are low and SOX emissions Queen Mary 2 in the early 2000s. As with designers considerable flexibility in locating negligible because higher grades of fuel Existing onboard energy storage and naval ships, these latter vessels were gas turbines in a ship when a turbo-electric are burnt. power generation systems predominantly designed as combined cycle ships with drive is specified. iv. Maintenance is normally running hours- develop power by breaking chemical bonds combinations of gas turbines and diesel- based and the turbines can be removed between atoms. In contrast, nuclear power electric generators. The advanced modern aero-derivative from the ship for replacement relatively generation is the fission of large, heavy gas turbine units are designed to burn easily. nuclei into smaller fission products under For the merchant ship gas turbine market commercially available distillate fuels which controlled chain reactions; (Appendix 6). two types of prime mover made their meet the current legislation on emissions Disadvantages This releases a large amount of heat appearance: the aero-derivative and the and smoke requirements. Distillate fuels, i. The fuel for aero-derivative gas turbines energy which is transferred to a coolant to industrial gas turbines. The former were however, are considerably more expensive is currently expensive when compared to generate useable power via an appropriate able to supply high power but requiring the than the conventional marine fuels burnt in conventional marine fuels because it is a thermodynamic cycle. Nuclear propulsion, use of high grades of fuel, while the latter diesel engines used by merchant ships: for high distillate fuel. therefore, represents a potentially radical generally gave more modest levels of power example, the ratio of distillate fuel price to ii. All gas turbines are less efficient as the solution by being a CO2-free propulsion but used poorer grades of fuel as well an average of 180 cSt and 380 cSt bunker ambient temperature rises, and this source when operating. as offering easier maintenance regimes. fuel was 1.5 in October 2012 (Bunkerworld is particularly true of aero-derivative Typical of the latter application were the 2012). For this reason they are not currently turbines (TICA 2012). Nuclear ship propulsion is not new, it HS1500 high-speed car ferries favoured in the merchant marine industry. iii. Thermal efficiencies are lower than for was first introduced into the submarine which operated for a time on a number of diesel engines of similar power. environment, together with stringent routes around the United Kingdom and A further variation of gas turbine crew selection, education and training elsewhere. technology is the combination of a gas regimes, by Admiral Rickover of the turbine with a heat recovery steam turbine United States Navy in 1955 when the A range of commercially available aero- running on the flue gases, enabling a USN Nautilus sailed on its maiden voyage. derivative gas turbines have been designed rather greater overall thermal efficiency for Since that time, some 700 nuclear reactors for the marine market; these include the electricity generation. have served at sea and today there LM2500, the WR21 and the MT30, are around 200 reactors providing the Figure 3.5. Earlier machines included the power to propel ships and submarines. Olympus and Tyne gas turbines. In the case Shortly after the naval initiatives the NS of the MT30 this has a maximum rating Savannah (Figure 3.6) was conceived as a of 40MW at 15 ºC and a thermal efficiency Figure 3.5 mt30 marine gas turbine. This photograph passenger cargo demonstrator ship under is reproduced with the permission of Rolls-Royce plc, © Rolls-Royce plc 2013

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President Eisenhower’s Atoms for Peace ppm. Development in various parts of the Molten salt reactors are possible steam generators. The others are integral Molten salt programme. Following the NS Savannah world is being undertaken to produce a future candidates for ship propulsion, plants, with the steam generators inside the reactors are in the 1960s, the Otto Hahn and Mutsu robust reactor for this fuel source which has however, a lengthy period of research reactor pressure vessel. Currently, the US came from Germany and Japan respectively: a further advantage in that the half-lives and development is necessary for this to Department of Energy is co-sponsoring a possible future again both ships being largely designed of the irradiated products are generally happen. Nevertheless, some of their relative project to examine the cost-effectiveness candidates for as demonstrators for nuclear propulsion. considerably shorter than those from merits and disadvantages are discussed in of small modular reactors in the region Since that time, a relatively small number natural uranium based fuels. Thorium-based Appendix 6. of 180MW. ship propulsion, of other nuclear-propelled merchant ships reactors, depending on their configuration, however, a have been built, most notably the Russian may only produce some 3% of the high The era of nuclear power began with The design and regulatory process icebreaker classes with perhaps the most level waste developed by current nuclear reactors that had low power output, To design and build nuclear-powered lengthy period famous being the Lenin, as well as a number reactors and have a lower weapons typically tens of MW. Over time, economies merchant ships significant changes to the of research and of dual purpose ships engaged on specialist proliferation risk than conventional of scale have produced the latest normal design procedures are required. duties, such as the Yamal and, more uranium-plutonium cycle reactors. However generation of power plants which generate The process would be driven by a safety development is recently, the 50 Years of Victory which some thorium reactors require starter fuels up to 4.5 GW of thermal power yielding case in which the building, operation, necessary for are combined passenger cruise ships and to grow the fissile 233U. Therefore, they do 1.0 to 1.6 GW electric. These are far too maintenance and decommissioning of icebreakers. not displace some level of security being large for shipboard application; however, the ship are the principal features. The this to happen. deployed. recently interest in a new type of reactor, safety case would embrace the nuclear, There are several potential fuels, modes the small modular reactor, has arisen. mechanical, electro-technical and naval of fission and reactor coolants that could These reactors are much smaller in terms architectural aspects of the ship design with be used for merchant ship propulsion. of power output and physical size and are the safety and integrity of the nuclear plant However, the most common reactor type intended to be constructed in a modular taking precedence. Within this concept Thorium Reactors is the uranium-fuelled pressurised water fashion involving a significant element of the process of undertaking the safety reactor. Natural uranium comprises three A number of options exist for utilising factory build. The underlying economic analysis would typically split the ship into isotopes: 238U, 99.3%; 235U, 0.7% and 234U, the energy contained in Thorium all of principle with these modular reactors is a series of subsystems: some having real 0.005%. The fissile component in the fuel is which involve the breeding of Th into that economies of scale are traded for and others virtual boundaries. The analysis 233 235U where neutrons emitted in the fission U. Typically these are: economies of mass production. There are would consider the effects of a failure process are slowed down (moderated) • Solid fuel in a light water reactor. several small modular reactor designs, occurring in one of the subsystems on the by the coolant (water) before causing • Liquid metal cooled fast breeder (Table 3.2), that have appropriate power nuclear power plant and vice versa. With fissions in further 235U atoms. The energy reactor. outputs which are suitable for large ship such a procedure all parties concerned with absorbed by the coolant is transferred to • Gas-cooled fast breeder reactor. powering applications (Table 3.3). The the ship would need to be involved: this a secondary steam cycle that generates • Sub-critical accelerator driven. small modular reactors identified in Table would include the builder, classification either electricity or direct shaft power. In • Molten salt reactor. 3.2 are all are PWR. Moreover, the KLT 405, society, flag state and national nuclear PWR reactors only a small percentage of Each of these options has relative VBER 150 and SMR units are derived from administration as well as the duty holder, naturally occurring uranium is fissionable, advantages and disadvantages and submarine reactor plants and have separate the ship owner. Moreover, the duty holder 235 U, which implies that uranium has to be in some cases they are currently at 235 enriched in its U component. While it is the theoretical concept stage: China possible to achieve virtually any level of announced in early 2011 that it was Small reactor designs Country of manufacture Power output (MWe) enrichment that is desired, uranium for use starting a molten salt thorium reactor KLT 40S Russia OKBM 35 in civilian programmes is generally around programme. Molten salt reactors 235 5% of U. Levels of enrichment of 20% embrace a family of reactor designs VBER 150 Russia OKBM 110 or greater are subject to stringent controls that use a mixture of molten fluoride, SMART South Korea KAERI 100 due to international safeguards and nuclear or chloride salts as the coolant with MRX JAERI 30 weapons proliferation concerns and are only operating temperatures of the SMR United States of America Westinghouse 200 used in specialist or military applications. order of 650ºC. More recently an Table 3.2 Proposed mPower United States of America B+W 125 small modular reactor investigation has been undertaken NuScale United States of America NuScale Power 45 designs Another potential source of fissionable to assess the potential for molten uranium fuel is thorium which is more salt reactors to power warships plentiful than uranium and typically exists (Hill et. al. 2012). in the soil in concentrations of around 6 Ship type Size Typical power requirements (MW) Bulk carrier 320000 dwt 30 Table 3.3 Typical Container ship 12000 TEU 80 power requirements Cruise ship 100000 dwt 70 for large ships

34 Royal Academy of Engineering Future ship powering options 35 Primary propulsion options

would be called upon to demonstrate to IAEA principles and requirements in their Ship design and operational underwater they are, for much of the In any future an independent regulator their ability to certification processes. Consequently, From the considerations time, shielded from the natural radiation merchant ship operate the ship in a proper and competent the port and flag state authorities, in health physics The quantity of fuel used in a PWR reactor sources which come either from space or manner. Furthermore, the entire process turn, are likely to depend on their national is considerably less than the amount of via the rocks and minerals within the Earth. application would need to embrace the principles and approaches to satisfy themselves that perspective conventional fuel burnt in conventionally Nevertheless, a level of monitoring would of nuclear requirements defined by the International their dependent communities are suitably the application powered large ships. For example, the be required in the context of a crew member Atomic Energy Agency (IAEA), and adapted protected. Notwithstanding nuclear- mass of uranium fuel, enriched in 235U to trained in health physics and professionally propulsion there for the marine environment; (Appendix 7). powered ships visiting ports in the normal of nuclear 3.5%, which would be used by a 12,500 supported from the shore. would need to course of their duties, issues surrounding propulsion is teu container ship undertaking a voyage at In any future merchant ship application of the ship’s plant maintenance require 25 knots from Rotterdam to a port on the Nuclear plant ownership and safety be cooperation nuclear propulsion there would need to careful consideration. While normal hull relatively well east coast of the United States of America A key question relating to merchant ship between IMO and be cooperation between IMO and the IAEA and structural maintenance is unlikely to understood. would amount to a few kilograms. This is in nuclear powering applications is whether to enable their different and extensive be a significant issue, any maintenance contrast to some 1,550 tonnes of heavy fuel a nuclear plant is purchased or leased by the IAEA to enable sets of expertise to be reflected in design involving either directly or indirectly the Given the correct oil that would normally be burnt. Nuclear the ship owner. This question embraces their different regulation. Indeed, the role of land-based nuclear plant would be of concern within design of the propulsion, if applied to merchant ships, consideration of the cost of failures nuclear regulators and the views of the flag the safety case and the port regulations. would therefore have the potential to occurring in the system: a situation which and extensive and port state controls would be critical Indeed, small modular reactor plants may fit shielding around permit further concepts in ship design to be has on occasions been extremely expensive sets of expertise for any successful implementation of well with these operational and duty holder the reactor, contemplated: typically in the field of ship to solve in some naval installations. The marine nuclear propulsion. In this respect, considerations. speed or deadweight capacity; (Appendix 6). leasing option of standard nuclear plants, to be reflected in the trade routes upon which nuclear ships which is a known such as small modular reactors, provided design regulation could be deployed and the countries that In addition to the requirements imposed on technology, the In the case of a nuclear-propelled ship they are built in sufficient numbers, would would be prepared to accept nuclear- a nuclear-propelled ship, nuclear regulatory requiring assistance while on passage, the help to distribute these costs between powered merchant ships need careful arrangements would be applied to the shore emitted radiation salvage or rescue processes demand careful different owners which would not be consideration. Moreover, given that ships facilities used to support the shipboard dosage is very low analysis. It is unlikely that the standard the case for bespoke units. Furthermore, frequently sail between ports and through reactor plants. These arrangements would Lloyd’s Form would suffice and amendment if this concept were adopted, although territorial waters of different countries, need to be identified in the appropriate to or reconstitution of that approach not relieving ship owners from their the processes for mutual acceptance and safety cases and levels of security similar would almost certainly be required. From responsibilities as duty holders, it may recognition of nuclear certification would to those currently applied to civil nuclear a machinery perspective such a scenario simplify the execution of those duties become a key element in ship operation and power plants are likely to act as a basis for would be an extreme case, since a nuclear- by the plant manufacturer undertaking voyage planning. This scenario is further the consideration. propelled ship would need to have an the complete machinery cycle through complicated because national land-based auxiliary means of propulsion: particularly the design, certification, manufacture, nuclear regulators around the world adopt if it was fitted with a single reactor plant. operation and eventual disposal of the different approaches to demonstrate the Typically, this might be a diesel engine propulsion plant. Indeed, the operation and capable of propelling the ship at six or seven disposal aspects of the nuclear plant life knots towards a safe haven. Alternatively, cycle are particularly onerous as both would if two independent small nuclear power require detailed knowledge on the part of Nuclear Codes, Rules and Applications plants were provided then the need for an the ship owner which, at present, few, if In 1981 the International Maritime Organisation adopted a Code of Safety for auxiliary propulsion diesel engine may be any, would possess or wish to possess. Nuclear Merchant Ships, Resolution A.491(XII), and although it has not been reduced. implemented it is still extant. However, although being relatively far-sighted at A further issue with regard to nuclear fuel the time of its adoption it would need to be updated to be aligned with the current From the health physics perspective the is that non-nuclear nations with shipping thinking on nuclear safety. Prior to that Resolution, Lloyd’s Register also maintained application of nuclear propulsion is relatively interests might wish to take advantage of a set of Provisional Rules for nuclear-propelled merchant ships between 1960 and well understood. Given the correct design leasing small modular reactors to prevent 1976 and these have recently been revised for use by the marine industry in of the shielding around the reactor, which is them having to acquire nuclear technology design studies. a known technology, the emitted radiation and material themselves in order to sail dosage is very low. Indeed, it is claimed that commercial nuclear-powered ships on In addition to the full nuclear ship propulsion, there are a set of conventionally submariners operating nuclear-propelled their trade routes. Such a situation may powered ships which are used to transport nuclear fuel. These ships have systems submarines generally receive much lower conceivably create a potential proliferation and redundancies built into their ship systems and have contributed to the thinking doses of radiation than the remainder issue which would need resolution prior to on aspects of merchant marine nuclear safety. In another context, a series of non- of the population. This is because when the introduction of these power plants. powered barges which have nuclear power plants installed on them for use in the Arctic have also contributed in a similar way.

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Fossil Fuel OECD (Regional) IAEA (Global) Propulsion Paris Convention 1960 Vienna Convention 1963 Range of fuel prices Brussels Convention 1963 Revised Vienna Convention 1997 Table 3.4 Nuclear Nuclear Revised Paris & Brussels Conventions 2004 Convention on Supplementary Compensation 1997 liability conventions Refuelling interval Operating fuel costs

Figure 3.7 Schematic have allowed the establishment of specialist The implementation of insurance principles outline for through- nuclear insurance pools which insure the in the merchant marine environment will life fuel cost analysis Ship life cycle liabilities associated with nuclear facilities. differ fundamentally from that which Table 3.4 shows the conventions in force at applies to navies where governments take present. a major role in underwriting the risk. This is unlikely in the merchant service. This, If full plant ownership were contemplated a lower initial cost but then an operating Furthermore, there are issues concerning therefore, raises further issues relating Considering the sea staff training programmes, analogous cost gradient reflecting the fuel the understanding of nuclear damage to the insurance of nuclear-propelled life cycle costs to those operated by the navies who consumption during the ship’s existence for which operators must provide merchant ships: in particular, the stance use this technology, would be required. with the average reflecting oil price changes compensation in the event of an incident. of hull and machinery underwriters as of a ship, while Nevertheless, even with the leasing over shorter time intervals; (Figures 3.7). Currently loss of life, personal injury, loss distinct from that of P&I Clubs. In the the nuclear model, assuming the leaser provides the If, however, fuelling for the life of the ship of or damage to property and economic former case, nuclear technology and its expert staff to operate the plant, some were contemplated and possible for a loss related to the foregoing are insurable. mechanical risks are comparatively well- option has a level of expertise would still be required merchant ship, then the operating fuel costs However, concerns remain: the full understood and, if not, lend themselves to higher initial of nuclear operation by the ship’s officers. would become constant; that is, a straight insurability of the reinstatement of an some level of probabilistic analysis of risk. In both respects the current STCW Code line on Figure 3.7 rather than the saw-tooth impaired environment, use or enjoyment Cover would be restricted to exclude any capital cost, the requirements are deficient. Moreover, characteristic shown in the figure. of the environment and preventative physical damage to the vessel’s machinery gradient of the training would need to have a reactor- measures. Additionally, in the maritime case arising from failure of the nuclear plant, specific element with revision periods A nuclear option would be more difficult to is the measurement of damage at sea. certainly that which results in radiation curve is much and recertification being necessary. This finance because the initial cost has to be release. Current policy conditions have a shallower with would have implications for some current paid upfront and the owner becomes a price Assessing the risk posed by nuclear standard restriction that excludes that type employment arrangements within the taker not a price setter: since there is no propulsion is fundamental to the insurance of event. Some cover may be accessible, step increments merchant navy. Furthermore, shore-based choice but to take market rates to capture issue and Table 3.5 identifies the nuclear but the capacity available to do so would when refuelling facilities would need a nuclear safety income to amortise the cost of build. Clearly, perils, machinery risks and fire protection be restricted as underwriters reinsurance organisation manned by suitably qualified for the nuclear option other cost elements issues that require assessment. programmes mirror that policy exclusion, is required and experienced personnel. arise about which little is known at meaning any insurance share written would present: these include the cost of finance, The issues highlighted in Table 3.5 are be net without the benefit of reinsurance Nuclear safety considerations will drive maintenance, pilotage, port dues, survey principally the risk assessment principles of protection. Secondly and more importantly, different shore infrastructure requirements fees and insurance. While these elements land-based plants, however, in the marine issues such as ports of refuge, availability of from those currently in place for are well known for conventionally propelled case the issue is further complicated. It salvage services and formal vessel response conventionally propelled merchant ships. ships, through-life fuel costs, while is a mobile platform with limited internal plans are key. While hull underwriters would These would impact on factories, shipyards, reflecting the underlying market trends, space; has limited maintenance resources; not provide cover for the direct effect of ports and dockyards throughout the are likely to be significantly influenced by has operational imperative; risks arise from nuclear and radiological effects of reactor whole life cycle of the nuclear propulsion future marine fuel policies. This is because the existence of hostile zones and the failure and consequent contamination it is plant and, in so doing, would be a major higher grades of fuel are, in present attendant risk of a collision, grounding or likely that conventional cover will be in place cost driver for nuclear powered merchant terms, considerably more expensive and, foundering hazard. otherwise, including salvage and sue and shipping. There would be a number of life furthermore, any introduction of carbon tax cycle requirements that would need to be will only exacerbate this situation. satisfied: (Appendix 6). Insurance Nuclear perils Machinery risks Fire protection As previously concluded when discussing The key principles of nuclear liability are Reactor characteristics Design authority, systems engineering Fire hazard other related aspects of nuclear propulsion, established by international treaties which Barriers to release Adequacy or failure of maintenance Plant segregation and the small modular reactor concept may be of influence national legislation and dictate – Predictive, preventive, corrective compartmentalisation assistance in simplifying these issues. the scope of operator liability. Countries Reactor protection Equipment reliability Fire detection are either signatories to the conventions Radiation protection Plant protection Fire suppression Cost models between nuclear and or have legislation that adheres to the Accident mitigation Condition monitoring Fire water supply conventional propulsion principles embodied within the conventions. Considering the life cycle costs of a ship, As such, nuclear liability insurance policies Emergency planning Operating history Control of hazardous operations, ignition sources while the nuclear option has a higher initial must follow relevant national legislation capital cost, the gradient of the curve is and often require government approval. Human factors OEM support Control of fire, loading and housekeeping much shallower with step increments General non-nuclear risk insurance policies when refuelling is required. In contrast, have radioactive contamination exclusions; Regulatory framework Spare part availability and quality Fire team conventional propulsion alternatives have these fulfil the channelling principle and Table 3.5 Risk Terrorism and sabotage Values Fire drills assessment issues

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labour: costs incurred by common interests Some potential advantages and support system; and emergency usually to be sustained for some days. Nuclear in the maritime adventure to prevent or disadvantages of the technology: lithium-air response plans. However, new technologies in this or any propulsion mitigate loss. Therefore as insurers assess a Advantages batteries may v. Insurance is a major issue for merchant other area need care in their introduction has clear nuclear powered risk, it is likely they would i. Nuclear ship propulsion during operation offer the promise ships that would require careful in terms of performance and reliability. require: emits no CO2, NOX, SOX, volatile organic consideration and resolution for greenhouse gas • Confirmation that the route assumed has and particulate emissions. of a significant merchant ships. New battery chemistries include metal- sufficient on-call salvage services. ii. A significant documented body of vi. The non-technical issues need resolution sulphur, where the metal is magnesium, advantages and • That a formal vessel response plan is in experience exists in the design and energy density before nuclear propulsion could become sodium or lithium or metal-oxygen – also has been shown place (OPA 90 VRP provisions). safe operation of shipboard nuclear multiplier above a realistic option for international referred to as metal-air where the metal • That the coastal states en-route have propulsion plant: particularly in the case trade routes. This would take time to is zinc, lithium or sodium. Currently the to be a practical formal port of refuge arrangements in of PWR designs. the current best implement and among these issues leading contender is the lithium-air battery. proposition with place. iii. The nuclear power plant concepts are performance number some national prejudices against Theoretically a lithium-air battery can suitable for merchant ship propulsion. nuclear-propelled ships. liberate 11,780 Wh from the oxidation of naval ships and As far as the radiation element of risk is iv. Small modular marinised reactor or from lithium- vii. Nuclear propulsion, due to these one kilogram of lithium. Unlike most other submarines concerned, available cover would be limited molten salt reactor plants may attenuate ion battery constraints, should only be considered as batteries, which carry the necessary oxidant and expensive. Other solutions would many of the difficulties associated with a medium- to long-term option. within the battery, the lithium-air battery therefore be needed such as accessing nuclear propulsion although they will not technology draws in oxygen from the atmosphere existing nuclear pools. dispose of them. during discharge and liberates it during v. Nuclear propulsion would offer further charging. Hence, lithium-air batteries can In the alternative case of one member flexibility for merchant ship design and be very light but require a means of supply of a P&I Club purchasing a nuclear ship operational planning with respect to 3.6 Batteries and removal air: analogous to a fossil- which was subsequently the subject ship speeds, hull form and ship numbers fuelled engine. of a claim, this could expose the other deployed on a route. The lead acid battery, the zinc-carbon dry members of the mutual club to considerable vi. The costs of the fuel are initially paid for cell and the nickel-cadmium battery have Despite the high theoretical energy density financial liability. Furthermore, from a P&I along with the reactor plant and thereby been the most common battery types of lithium-air battery technology, the perspective, which is third party rather than remove exposure to price fluctuations throughout much of the past 150 years. currently achieved performance is below first-party cover, the problem of cover for for significant periods of operational During that time they have evolved little. that initially expected from a practical radiation is magnified by definition. service. As storage media they variously exhibit device; that is, 2,000 Wh/kg. Nevertheless, low energy density, low power density the development of lithium-air batteries is Nuclear propulsion in the future Disadvantages or suffer from other weaknesses. These at an early stage and has encountered both Nuclear propulsion has clear greenhouse i. The conventional methods of planning, include an unacceptable self discharge rate successes and setbacks; including problems gas advantages and has been shown building and operation of merchant ships or a memory effect in which the maximum with capacity fading, cycle life, a noticeable to be a practical proposition with naval will need complete overhaul since the energy capacity of a partially discharged mismatch in charging and discharge voltage ships and submarines as well in certain process would be driven by a safety case battery is reduced with each re-charge. as well as in limitations in the rate of oxygen specialised ships and demonstrator and systems engineering approach. Consequently, these attributes do not diffusion. Given that many research groups projects. Considerable experience has ii. There would be a number of additional commend them practically or economically are working in this technical area, lithium- been accumulated in the operation of PWR constraints imposed on the ship design for large-scale use as an alternative means air batteries may offer the promise of a propulsion units, nevertheless considerable and operation. of power for marine propulsion. significant energy density multiplier above difficulty and cost would be incurred in iii. In contrast to the second advantage, the current best performance from lithium- developing a deep sea, international there is a relatively small number of In recent years, there have been significant ion battery technology. merchant ship today. The difficulties would nuclear propulsion experts at all levels Super store improvements, (Figure 3.8), and energy Rechargeable-battery capacity arise from a number of aspects: design and this will cause competition with World trends. Wh/kg and power density are becoming much Despite the potential of lithium-air execution and planning, operation, training land-based installations. higher. These newer battery types can batteries, many companies in Japan, China, 400 of crews and shore staff, nuclear regulation, be recharged more quickly; have lower iv. In contrast to conventional methods New Li technologhy South Korea, Europe and the USA consider security, public perception, disposal and of ship propulsion, there are further 300 self discharge rates and are free of a that lithium-ion battery performance can be

so on. It has been seen that the concept of issues surrounding the deployment 200 memory effect. significantly improved. There is, therefore, Li-ion/Poly small modular marinised reactor plants or of nuclear technology which require NiMH the provision of significant research 100 molten salt reactors may attenuate many resolution. These include international Although they provide better performance, funding for improving lithium-ion battery NiCd of these difficulties although not dispose of regulation; public perception; initial 0 these newer battery types do not as yet performance as well as developing other 2015 1970 2010 1990 1980 them. As such, it would be prudent to keep a capital cost and financing; training and 2000 generally satisfy the marine propulsion post-lithium-ion battery technologies. watching brief on the development of these retention of crews; refuelling and safe Dashed lines denote forecast data needs. In this sector significant power is technologies with a view to implementation storage for spent fuel; the setting up Figure 3.8 World trends in rechargeable required and for all but the shortest of A report (IDTechEx 2011) explored the pattern in the medium to long term. and maintenance of an infrastructure battery capacity (Source: Avicenne) coastal voyages, the power output has of patenting activities in the advanced

40 Royal Academy of Engineering Future ship powering options 41 Primary propulsion options

energy storage sector over the prior the oceans the abundance of magnesium one round trip and recharging is done during seven-year period. Their report showed and lithium is 1,290 ppm and 0.17 ppm unloading and loading of the passengers 3.7 Fuel cells that four companies have approximately respectively. from shore-power. The recharging takes 8,500 applications between them which four minutes via a 400V supply at the stem Invented in 1838, the fuel cell predates indicate an intense level of activity in the Estimates forecast that by 2030 the cost of the ferry. In addition, photovoltaic panels the four stroke spark ignition engine and field of energy storage. In addition, many of both lithium-air and lithium-ion battery contribute to the electrical energy used by the diesel engine. For more than a century small, typically university-derived, spin-off packs will be similar and extra large battery navigation equipment. it was little more than an engineering companies are pursuing narrowly focused packs suitable for marine propulsion may curiosity as there was neither the need innovations and some of their efforts may cost somewhat less per kWh. Although Some potential advantages and nor the means to develop it. Interest was prove significant in the future. magnesium currently costs about 1/20 disadvantages of the technology: rekindled in fuel cells as the space race of that of lithium, there are other costs Advantages progressed for three reasons: their mass With regard to raw material availability, in the construction of a battery. The cost i. Battery-based propulsion of merchant is low, the only exhaust product is water

world deposits of lithium are comparatively of recharging will be linked to the cost of ships is beneficial from the CO2, NOX, SOX, and materials technology had developed limited. There is a consensus that global electricity needed to refill the batteries. In volatile organic and particulate emissions sufficiently to enable their promised high reserves of lithium are between 10–11 the case of marine propulsion this could be points of view since during operation efficiency to become a reality. million tonnes with the majority vested in provided by a range of renewable sources none occur. Chile (IEEE). Therefore, if a growing adoption feeding the national grid into the port. ii. Batteries, by virtue of the rapidly Fuel cells, like a battery, produce energy of lithium-based batteries takes place developing technology surrounding from an electro-chemical process rather the rate of consumption of the limited A new battery technology spun-out of them, offer a potential solution for the than combustion. Fuel cells have no moving global stock and costs of lithium may be Stanford University (Stanford 1&2) is the all- propulsion of smaller ships in the medium parts but do require additional support plant expected to increase. An alternative battery electron battery which is claimed to have to long term. such as pumps, fans and humidifiers. Two technology that may address this risk is the much higher power and energy density than iii. Batteries in conjunction with other reactants, typically hydrogen and oxygen, magnesium-ion battery. Active research is available from a chemical battery together modes of propulsion may offer a combine within the fuel cell to produce programmes are underway and there with a significantly lower cost/kWh. potential hybrid solution for the water, releasing both electrical energy are optimistic reports that rechargeable propulsion of small- to medium-sized and some thermal energy in the process. magnesium-ion batteries, using the best In a related technology, energy storage ships. Unlike a conventional battery in which new cathode materials, could deliver based on super-capacitors has been the reactants consumed in the energy a threefold increase in energy density implemented on a small 22 m passenger Disadvantages conversion process are stored internally compared to lithium-ion: about the same ferry, the Ar Vag Tredan; (Figure 3.9). i. At present, the size of the necessary and eventually depleted, the reactants improvement as that forecast for lithium- This ship makes short voyages of around battery pack would preclude their use consumed by the fuel cell are stored air. Moreover, magnesium is more common 2.5 nm in sheltered waters at a maximum as the sole means of propulsion in all externally and are supplied to the fuel cell in than lithium. Its crustal abundance is 29,000 speed of 10 knots. The energy storage in but the smallest of ships on short sea an analogous way to a conventional diesel ppm whereas for lithium it is 17ppm and in the super-capacitors is enough to permit voyages. engine. Hence a fuel cell has the potential to ii. Full battery propulsion must await produce power as long as it has a supply of further technical development and even reactants. then it is likely to be confined to the smaller ship end of the market. Many values are quoted for the efficiency iii. The battery pack requires replacement of a fuel cell and all should be treated with when it reaches its life as determined by caution and considered in context. The the total number of charge/discharge fuel types, storage conditions, inclusion cycles. of a reformer and type of output power must all be considered. A comparison of fuel cell performance with that of diesel engines should be not be based on simply considering the engines themselves: the whole propulsion chain should be taken into account particularly as diesel engines produce rotary output and fuel cells DC electrical output. One view is to consider the theoretical maximum efficiency of a heat

Figure 3.9 Ar Vag Tredan super-capacitor driven ferry [Courtesy stx-Lorient]

42 Royal Academy of Engineering Future ship powering options 43 Primary propulsion options

90

Fuel cell and heat engine combined cycle 80

Efficiency % 70

60 Hydrogen

50 Heat engine 40 gas by converting methane into hydrogen cell technology in Ships (FCSHIP) (2002– Figure 3.10 Theoretical heat 30 PEMFC PAFC MCFC SOFC engine and fuel cell efficiencies within the fuel cell itself; termed internal 2004) and New-H-Ship (2004–2006). [Larminie and Dicks 2000] 0 reformation. The disadvantage is that These programmes assessed the technical 0 200 600 400 800 carbon in the fuel is converted into CO2. feasibility of installing fuel cells on ships 1000 Temperature ºC followed by a number of demonstrator Until recently, fuel cell development in the projects (EC 2002–2006). The projects had marine field has been limited, the exception a strong representation from the Nordic engine and a fuel cell; Figure 3.10. The heat The proton exchange membrane fuel cell is being Air Independent Propulsion for countries, including Iceland, who saw fuel engine limit is calculated using the Carnot classified as low temperature and is being submarines and Autonomous Underwater cells as a catalyst for developing a hydrogen cycle with a lower reservoir temperature developed for the automotive market, Vehicles. The first practical application of economy. Nordic countries, in particular of 100 ºC. The fuel cell is supplied directly among other applications, in the 1–300 a fuel cell for motive power in a submarine Iceland, have huge reserves of hydro- and with gaseous hydrogen and oxygen, not kW range. The phosphoric acid fuel cell was in 1964 when Allis-Chalmers produced geothermal power with which to produce air. With the exception of fuels cells used is also low temperature and has a higher a 750kW fuel cell for the Electric Boat green hydrogen: that is, production without in space and submarines, air is substituted power band, typically 10kW to 1MW, but Company to power a one-man underwater significantly adding to the greenhouse for oxygen as one of the reactants. Using is not suitable for marine applications due research vessel. More recently, Siemens, gas burden. A more recent project moved air, with the normal 21% oxygen content, to the nature of its electrolyte. The direct at the behest of the German government, away from hydrogen as a fuel, MC-WAP – reduces efficiency but this is offset by the methanol fuel cell is a third low temperature developed a successful 120kW PEMFC fuel molten-carbonate fuel cells for waterborne free supply as in the case of diesel engines. fuel cell which uses methanol as its cell for the German navy. A pair of these applications (2005–2011). The purpose of hydrogen source. The high temperature units is used for the AIP pack in the Class this initiative was to study the application of The high temperature fuel cells have the fuel cells, molten carbonate and solid 214 submarines which were constructed the molten carbonate fuel cell technology potential to achieve efficiencies similar to oxide fuel cells, can be built for much for a number of navies, including those onboard large vessels, such as Ro/Pax, if not better than those of large marine larger powers from a few kilowatts up to of South Korea and Greece. The Class Ro/Ro and cruise ships. This included the diesel engines, especially if they are 10MW and, therefore, are candidates for 209 boats, which were mainly produced design, construction, installation on board combined with a steam plant to make use main propulsion as well as auxiliary power for export, are offered with a 6m long and testing of a 500 kW auxiliary power unit, of their thermal output. Table 3.6 shows generators. AIP extension and retrofitting to existing powered by MCFC and fuelled by diesel oil. an alternative evaluation together with boats is an option. Both submarine types Project METHAPU (Validation of renewable comparative specific powers and power A major issue for fuel cells is their fuels: carry liquid oxygen, internally for the 209 methanol based auxiliary power systems densities. While efficiencies are similar, oxygen can be obtained from air but and externally for the 214, and store the for commercial vessels) (2006–2010) diesel engines significantly outperform fuel hydrogen is more of a challenge. One hydrogen in external metal hydride tanks. developed a methanol/air SOFC for use cells in terms of specific powers and power option is a direct supply of hydrogen, but Fuel cells are also used for autonomous in marine applications. A prototype 20kW densities. at present bulk storage is problematic, underwater vehicles; the Hugin series, built unit, produced by Wärtsilä, was installed (Section 3.9), and the infrastructure by Kongsberg, uses an aluminium-oxygen aboard the Swedish Wallenius Lines car In Table 3.6 the values are roughly is lacking. The external reformation of semi-fuel cell. The hydrogen peroxide fuel, carrier mv Undine to assist in auxiliary estimated and based on available product diesel is an alternative and is seen as a electrolyte and the anodes reportedly power production. So far the programme documentation for the fuel cells as well as viable alternative for the military which require frequent replacement. has demonstrated the ability of SOFC DNV’s Internal Report No. 2010–0605 for uses high distillate fuel. However, it is technology to withstand the demands of the combustion engines. Estimated electric more challenging to reform the low-cost, Some small ferries have been used to the marine environment and data analysis efficiencies are based on the lower heating heavy fuel oil commonly used by the demonstrate fuel cell technology. At is proceeding. While methanol requires a value of the relevant fuel and specific power merchant marine. A more realistic shorter- Expo2000 the msWeltfrieden was fitted number of additional precautions, when and power density are compared for two term scenario for marine fuel cell power with a 10kW PEM fuel cell, where the compared to conventional fuels, it was types of fuel cell power packs and two types generation would be operation by natural hydrogen was stored in metal hydride. Since demonstrated that it could safely be used of internal combustion engine. gas. A number of high temperature fuel cells 2008 ZEMSHIPS’ (zero emissions ships) without major deviations from operating are capable of operating directly on natural Alsterwasser, a 100-person passenger procedures or ship constructional methods. ferry, has been in use on the Alster River in Moreover, it was shown that the use of Hamburg. This ferry is powered by a pair of this fuel would present no greater risk to 48kW PEM fuel cells using air and hydrogen, the ship, its occupants or the environment Electric power generator electric efficiency Specific power) power density the latter being stored as pressurised gas. than would normally be attributed to (%) (kW/m2 (W/kg) conventional marine machinery. PaFCXell Fuel cell (MCFC) 45–50 3 15 The European Commission under the is a German-funded project currently Table 3.6 Characteristic Fuel cell (HTPEM) ≈ 45 30 60 5th, 6th and 7th Framework programmes underway to investigate the integration of properties of two fuel has funded studies, research and small PEM fuel cells into the auxiliary power cell types and two types Marine diesel (4 stroke) 40 80 90 demonstrators. Early projects included fuel of combustion engines. Marine gas (4 stroke) 45 80 90 generation grid of a cruise ship. [DNV 2012]

44 Royal Academy of Engineering Future ship powering options 45 Primary propulsion options

Figure 3.12 The rotor ship Baden-Baden, formerly the Buckau. Image courtesy of Wikimedia Commons

Some potential advantages and 3.8 Renewable energy Figure 3.11 The hybrid disadvantages of the technology: propulsion ship Advantages sources mv Viking Lady i. Fuel cell technology has a potential for © Viking Lady ship propulsion in the medium to long Wind energy term. Methods that use the wind to provide FellowSHIP is a joint industry research (DNV, 2012). Nevertheless, fuel cells, due to ii. At the present time encouraging energy to drive ships include a variety and development project with the aim the Nernst equation, cannot use all the fuel experience is being gained through of techniques. Typically these embrace of developing and demonstrating hybrid since the concentration of the reactants auxiliary, hybrid and low power Flettner rotors, or spinnakers, soft fuel cell power packs, especially usable dictates the voltage. So essentially 15 to propulsion machinery. sails, wing sails and wind turbines. for marine and offshore use: the partners 20% of the fuel (hydrogen) is left in the iii. For marine propulsion, the high include two major diesel manufacturers, anode outlet and should be used otherwise. temperature solid oxide and molten Soft sails are historically the oldest of these Wärtsilä and MTU, as well as DNV. The carbonate fuel cells show most promise. techniques, predating the use of mechanical FellowSHIP project has successfully The part load efficiency of fuel cells, in For lower powers, the low temperature forms of propulsion. While some remarkable installed a 330 kW MCFC operating on LNG contrast to diesel engines and gas turbines, proton exchange membrane fuel cells sailing passages were made, particularly aboard the Norwegian shipping company frequently shows an increase at lower loads. are better suited. in relation to the tea clippers in the 19th Eidesvik’s 6,200 dwt hybrid propulsion However in particular with external, and to iv. Methanol is a possible alternative fuel. and early 20th centuries, soft sail-derived Viking Lady; (Figure 3.11). This fuel cell a lesser extent, with internal reforming, the v. Fuel cells produce a DC electrical output power was dependent on the availability of operates in conjunction with four generator supply of the fuel could impede dynamic and are, therefore, suited to ships with the wind and relied on the skill of seamen to sets that can run on either diesel or LNG. loading and fast transients. electrical transmissions. make the best use of the available weather. They have successfully demonstrated vi. Fuel cells have no moving parts However, to some extent the mimicking of smooth operation for over 7,000 hours In the longer term however, it is the and consequently are quieter than these skills lends itself to automated control which suggests that fuel cells can be operating environment and adoption conventional machinery. systems today. adapted for stable, high-efficiency, low- of electric as opposed to mechanical vii. If fuelled with hydrogen, they emit no emission onboard operation. When internal transmission that is expected to change carbon dioxide from the ship. The made its appearance consumption was taken into account, the in favour of the fuel cell. Indeed, green viii. They require clean fuels and so do in the 1920s as seen in Figure 3.12. electric efficiency was estimated to be hydrogen, generated using renewable not emit SO , but also they are low- X The Flettner rotor utilises the Magnus 44.5 % with no NO , SO and PM emissions energy ashore and consumed in hydrogen- temperature devices and emit no NO . X X X effect of fluid mechanics, where if wind detectable. If heat recovery was enabled, fuelled fuel cells onboard ships, may offer passes across a rotating cylinder a lift the overall fuel efficiency was increased to a solution. In such an ideal operating Disadvantages force is produced. This force has a linear 55%; however, there remains potential for environment, the benefits of fuel cell i. Although hydrogen is the easiest fuel relationship with wind speed and, unlike further increasing these performance levels technology could be fully exploited. to use this would require a worldwide conventional sails or aerofoils, a true marine infrastructure to be developed cross-wind relative to the ship will produce for supply to ships: perhaps adjacent to a useful forward thrust at any ship speed an automotive sector. An additional Fuel Cell Applications even when this is greater than the wind ii. The use of more conventional marine speed. For a large ship, Flettner rotors can benefit for The US Navy, US Coast Guard and other navies have undertaken a number of studies fuels in fuel cells would present problems provide a small but significant proportion of for the installation of fuel cells. An additional benefit for the military is that fuel cells and necessitate complex onboard pre- the military is the total propulsive power. However, the are very quiet compared to diesel engines. A detailed concept study was conducted processing to take place. They would vorticity produced by a rotor is complex and that fuel cells into replacing a diesel generator set for the US Coastguard’s USCGC Vindicator by a in this case be a significantly more a full understanding of the mechanisms 2.5MW MCFC fuel cell. The package included a fuel reformer for low sulphur NATO expensive way of generating electricity are very quiet is still evolving, principally through the standard F-76 distillate fuel: the reformer separated the fuel into hydrogen and than conventional methods. means of computational fluid dynamics. compared to carbon dioxide. The US Office of Naval Research developed a 2.5MW ship service iii. Fuel cells produce DC electrical output The vorticity in the wake of a rotor raises fuel cell which was based on a MCFC and will reform naval fuel. The goal was to and, hence, are not so suited to ships diesel engines the issue of vortex interaction if more achieve their objective using commercial or near commercial technologies and for with mechanical transmission systems. than one rotor is fitted to a ship. This it to be highly reliable, maintainable and self-contained with respect to water and iv. Fuel cells have lower specific powers and requires exploration for a particular design, energy balance. The steam reformation of NATO F-76 was demonstrated for over power densities than diesel engines. particularly with respect to any interference 1,400 hours and has fuelled a sub-scale MCFC for 1,000 hours. It also demonstrated with the ship’s superstructure or high adequate tolerance to salt, shock and vibration. freeboard under certain wind conditions.

46 Royal Academy of Engineering Future ship powering options 47 Primary propulsion options

When power is provided by wind sources this will tend to alter the design basis of the propeller. Some allowance of the average power to be derived from the wind, therefore, needs to be taken into account in Figure 3.15 Application of a to assist propulsion © Sky Sails Figure 3.16 An image of a combination of solar and wind energy from Solar Sailor the propeller © Solar Sailor 2013 design in order In the case of the Baden-Baden two rotors, context of an augmentation of propulsive Solar energy generation capability, even if efficiency to optimise 18m high and 2.7m in diameter, were fitted power. There are, however, fluctuations Photovoltaic methods offer an approach for could be improved to 100% (MacKay 2009). in place of the previously fitted three masts. in the loadings derived from the sails and limited amounts of power generation on As such, coupled with a maximum attainable the overall It was found that the ship could sail much while there is a broad linearity of resultant board ships and trials have demonstrated specific power from the sun at given global performance of closer to the wind than when previously load when considered in the context of wind that some benefit is available for auxiliary locations and the generally limited available under sail and in 1926 the ship made a speed, there can be significant scatter in the power requirements. However, the deck area suggest that the power attainable the ship successful crossing of the Atlantic Ocean. results and this has to be taken into account maximum contribution is small when would only be sufficient to augment the Subsequently, another 3,000-tonne cargo- in the control system design. Fluctuations of compared with the power required to drive auxiliary power demands. passenger was ordered, the Barbara, and this nature require attention in the fatigue the ship (Mackay 2011). sailed between Hamburg and Italy for six and structural design of the installation. Conceptual proposals have been made years. In this case the rotors differed in that The average raw power of sunshine is a to increase the available area for energy they were 17m high and 4m in diameter, Soft sails and kites, Figure 3.15, have variable depending upon the latitude and capture from the sun by arrangements of rotating at 150rpm and they were three in been explored experimentally on modern the angle at which the photovoltaic cell solar panels on mast-like structures arranged number. The problem, however, remains merchant shipping. Their contribution in the is positioned relative to the sun. In the along the deck, sometimes in combination that if there is no wind the ship becomes ahead and leeway directions is a function of United Kingdom, the average value over the with wind augmentation; (Figure 3.16). becalmed in the absence of some other the relative magnitude and direction of the year is about 100 W/m2 on a horizontally Again, the number of masts that can be form of power: this, however, is a problem ship and wind speed. mounted surface. Throughout the world the accommodated is dependent on the type for all types of ship where wind is a source variation in power availability under average of ship and its duty as well the attitude of of power. In the case of wind turbines mounted on cloud cover is typically between 87 W/m2 the panels with respect to the sun in order Figure 3.13 E Ship 1 © Roberto Smera ships for the generation of electric power, in Anchorage to 273 W/m2 in Nouakchott to maximise the panels’ effectiveness. It More recently, the E-Ship 1, a 10,500 dwt similar considerations apply in that an on the coast of Mauritania. However, the is likely that these arrangements will only vessel shown in Figure 3.13, was built in adequate differential wind speed over the effect of cloud cover is significant in terms be effective in the sense of an augment to 2010. In addition to being fitted with two turbine rotor is required. For small ships of the energy that can be derived from the auxiliary power requirements. 3.5 MW diesel engines, E-Ship 1 has four and leisure boats gyroscopic couples from sun using this technology. Consequently, Flettner rotors: two aft, port and starboard, a also need to be taken into weather conditions and position on the Some potential advantages and and two forward behind the bridge and account to prevent stability issues in a planet are significant influencing factors in disadvantages of the technology: accommodation structure. With this seaway. developing the potential of solar power. Advantages arrangement the ship is capable of a i. Power derived from the wind is free from service speed of 17.5 knots. When power is provided by wind sources There is design potential to adopt a range exhaust pollutants. this will tend to alter the design basis of of rigid and flexible technologies. However, ii. Partial propulsion benefits can be Apart from leisure craft, the principal usage the propeller and lead to an off-design the principal constraint is the ability to find achieved through wind-based methods. of sail power today is in some aspects performance in some operating conditions. a large deck surface area on the ship which iii. Solar power has been demonstrated to of the luxury cruise market or with sail Some allowance of the average power to does not interfere with cargo handling augment auxiliary power. training ships. However, wing sails have be derived from the wind, therefore, needs or other purposes for which the ship was been used and a number of trials have to be taken into account in the propeller designed. In this context car transporters Disadvantages been undertaken in recent years. The mv design in order to optimise the overall are an obvious candidate for the application i. systems rely on the wind Ashington, Figure 3.14, provides an example performance of the ship. of this technology. strength to be effective. of wing sail application and sea trials have ii. The use of some wind-based systems shown that benefit can be obtained in the Resulting from the laws of physics, this rely upon adequate control system Figure 3.14 mv Ashington wing sail application technology inherently suffers from low technology being installed on board © Mercator Media 2013 the ship.

48 Royal Academy of Engineering Future ship powering options 49 Primary propulsion options

iii. Applications involving power derived would require increased above water Hydrogen is from the wind are limited to the structures to accommodate this storage 3.10 Anhydrous 3.11 Compressed air a potential augmentation of propulsion unless a capacity and, therefore, this may create ammonia and liquid nitrogen full return to sail is contemplated for difficulties in retrofitting ships to use liquid alternative specific applications. hydrogen fuel. Anhydrous ammonia is a dangerous, Compressed air and liquid nitrogen iv. While a return to full sail propulsion fuel for ship poisonous gas, but it can be compactly are two further alternative sources of is possible, this may have a number A significant advantage of liquid H fuel is 2 transported as a liquid in pressurised energy storage for ship propulsion. Both propulsion. of adverse commercial and financial that it generates no CO or SO emissions 2 X tanks at about 30 bar or cryogenically in require energy to produce or compress implications in some instances in terms to the atmosphere. NO emissions can be X unpressurised tanks. This is a bulk industrial in the cases of liquid nitrogen and air of voyage times, number of ships managed as for any other fuel, but where commodity, and can be burned in both respectively. As with hydrogen the required, etc. hydrogen is burned in a fuel cell, there are diesel engines and gas turbines. While it necessary energy requirement can be v. Solar power availability is global position no NO emissions. However, there are ship X emits no carbon dioxide at the point of use, derived from conventional and non-fossil dependent. safety design issues which need resolution. it cannot be considered ‘carbon-free’ unless fuels or renewable sources together vi. Solar energy is feasible as an augment These centre on the flammability of the its manufacture (on land) does not emit with the same caveats. Furthermore, to auxiliary power but photovoltaic fuel when stored; the necessary pressure carbon dioxide, which is not currently the being energy storage media they exhibit processes are inherently of low vessels and cryogenic systems that would case. Its calorific value is about half that of similar system behaviours to those of the effectiveness, even under the best of be required. These issues are similar to, but diesel, so storage requires some adaptation more conventional battery or capacitor conditions, and require a significant more extreme than, those already required but much less than carrying hydrogen. technologies. deck or structural area upon which to and which have been solved with LNG or place an array of cells. LPG ships. The coldness of the ammonia can be used An assessment of the usefulness of these to cool the inlet air to the prime mover to storage media will depend on their system Similarly to LNG fuelling, for liquid hydrogen 5°C. As previously discussed in the context mass for the amount of energy required to become a realistic possibility for deep of LNG, for a gas turbine this can between recharge. However, inherently sea ship propulsion, a liquid H supply 2 be particularly effective. these are low energy density propulsion 3.9 Hydrogen infrastructure would need to be developed. methods. To successfully deploy these A further utilisation of hydrogen fuels The corrosion sensitivity of copper alloys to media it would be necessary to include Hydrogen is a potential alternative fuel might be in conjunction with fuel cell usage; ammonia is well known, but the sensitivity pressure vessels and, in the case of liquid for ship propulsion. It requires energy to Section 3.8. of steels to ammonia stress corrosion nitrogen, cryogenic systems: both well produce hydrogen and this could come cracking can be controlled by adding a small known technologies in land-based systems. from either conventional fuels or non- Some potential advantages and amount of water (0.2%) to the ammonia In the case of compressed air there would fossil sources such as wind, hydro-electric disadvantages of the technology: (Loginow 1989). be the attendant danger of blast if a tank or nuclear. Currently, all hydrogen used in Advantages for some reason ruptured. However, the industry is made from natural gas. In the i. Liquid H generates no CO , or SO 2 2 X Some potential advantages and technology for protecting compressed gas case of conventional sources, in order to emissions to the atmosphere originating disadvantages of the technology tanks from shock, in for example a collision be effective in CO reduction the issue of from the ship. 2 Advantages scenario, is well known in the container and whether the greenhouse gas emissions ii. Uses land-based sources of power for i. No greenhouse gas emissions on board railway industries. Corrosion of pressurised are simply being transferred from a creation. ship. tanks in a marine environment may also source on the sea to one on land has iii. Hydrogen can be used in fuel cells and ii. No sulphur emissions. present a problem and suitable inspection to be adequately resolved as carbon internal combustion engines. iii. There is mature, bulk manufacture of regimes would be essential. sequestration and storage has yet to be iv. Burning it produces a large feed-stock in 130 million tonnes a year. demonstrated at scale. fresh water. On land, compressed air energy storage is Disadvantages used only in conjunction with diesel or gas Veldhuis (2007) assessed the application Disadvantages i. Handling requires new procedures for turbines: the compressed air feed means of liquid H to a concept propulsion study i. Largely untried in the marine industry for 2 dangerous gases. that the pre compressor is not needed, and of a high speed container vessel designed propulsion purposes. ii. New bunkering facilities and therefore the prime mover can operate with for high value, time-sensitive goods as an ii. Hydrogen has some safety issues that infrastructure required worldwide. approximately 15% greater efficiency. alternative to air freight. Liquid hydrogen need resolution. iii. Some additives needed to promote benefits from a much higher specific heat iii. It has a low energy density. ignition in diesel engines. With compressed air storage, the per unit weight than conventional fuels but iv. Would need a hydrogen supply infra- iv. Made from natural gas, so always more considerable amount of energy used to requires a much greater volume for storage. structure to make it viable for the marine expensive than LNG. compress the air is not all stored on board If stored at 700 bar pressure the storage industry. v. There are some corrosion issues which the ship as the hot, compressed air is tanks would be at least six times bigger than need to be overcome. allowed to cool to room temperature. for conventional fuels. New ship designs

50 Royal Academy of Engineering Future ship powering options 51 Primary propulsion options

Serial hybrid system

3 x 368kVA share G1 G2 G3 supply Generators 400V, 50Hz, 3ph Cos ø = 0.9

ships ships Emer service ˜ ˜ service Swbd

battery DC link variable DC link battery bank speed bank 350kWh drive 350kWh This heat energy is lost. Therefore, to obtain Disadvantages Solid State Solid State substantial energy from the pure expansion i. A supply infrastructure and distribution Generator Generator of this stored compressed air (without using network would need to be developed. ˜ ˜ Figure 3.17 375 kW 375 kW it in the compressor of a prime mover), low- ii. The size, pressure rating and cryogenic Propulsion plant of 0–615 RPM M1 M2 0–615 RPM grade heat must be provided to supply the capabilities, in the case of nitrogen, of the Raasay hybrid ferry [Courtesy CMAL] needed energy. Sea water heat exchangers the ship storage tanks will determine the 375 kW Prop1 Prop2 375 kW are a possible source of this heat. The amount of energy storage and hence same situation arises with liquid nitrogen: usefulness of the concept. a source of low-grade heat is required to iii. There is an attendant blast risk with drive the evaporation and create a useful high pressure tanks should fracture be pressure. initiated. iv. Corrosion can be a significant issue Being energy storage media they have the in salt-laden environments with high 3.12 Hybrid propulsion grid when the vessel is moored in harbour advantage of generating no CO2, NOX or SOX pressure tanks. for the night. On low load sailings the ship emissions to the atmosphere when in use v. Largely untried in the marine industry can also be operated by only the batteries on board the ship. for propulsion purposes. Hybrid propulsion is an option where one feeding the electric motors; (Figure 3.17). vi. These are low energy density methods or more modes of powering the ship can Some potential advantages and of energy storage and, therefore, are be utilised to optimise performance for In this case the principal reasons for disadvantages of the technology: likely to be suitable only for short sea economic, environmental or operational considering hybrid propulsion were: Advantages routes. reasons. Most commonly today the different • greater redundancy i. Compressed air and nitrogen generate powering modes feed a common electrical • reduced fuel consumption bus bar from which power can be drawn no CO2, NOX or SOX emissions to the • reduced impact of CO2 emissions and atmosphere when in use on board a ship. for various purposes. This, however, need other pollutants ii. Uses land-based sources of non-fossil not necessarily be the case since many • uncertainty of future fuel costs fuel power for creation. examples of mechanical linkages between • insurance against increasing iii. Tank storage technologies are well independent power sources have been environmental legislation understood. designed and operated in ships, both past • noise reduction and present. Typical examples are to be • possibility to operate in zero emission found with 10,500 dwt E-Ship which was mode when the ship is in port built in 2010, Section 3.8, and COGAG and • lower maintenance CODAG naval vessels. The Royal Navy’s Type 45 destroyer’s is another typical It is estimated that this hybrid diesel-electric example where an integrated electric propulsion system will use at least 20% less propulsion system comprising two WR21 fuel for the ship than an equivalent diesel- gas turbine alternators and two diesel- mechanical propulsion system operating at electric generators supply propulsion design speed with the vessel fully loaded. electric induction motors at 4.16 kV. This fuel saving, in overall terms, relies on Similarly, with the Viking Lady in its the shore power component being derived deployment of dual-fuel generator sets from renewable sources. There will also be

and a fuel cell; Section 3.7. consequent reductions in CO2 emissions and at lower speeds and light loaded conditions The choice for a hybrid option can also greater fuel savings can be achieved. In port be location dependent. For example, the the ship is capable of operating on batteries new buildings to the order of CMAL for only with zero ship-produced emissions. the inter-island ferry service between the Islands of Skye and Raasay in the Hybrid propulsion, therefore, permits Hebrides where there is a strong desire to a further degree of design flexibility to preserve the environment. In this case the enable a ship to be configured to equitably propulsion system comprises diesel engines balance the constraints of economics and and a system of batteries. In this case the the environment by combining different batteries can either be recharged from power sources to meet the demands of the the diesel engines or from the land-based operational profile.

52 Royal Academy of Engineering Future ship powering options 53 Further propulsion considerations

vessels. A variant of these propellers is the As propeller-specific loading increases, to CLT propeller which attempts to enhance avoid the unwelcome effects of cavitation 4. Further propulsion propulsion efficiency by the use of blade the blade area has to increase which end plates. frequently has the effect of reducing considerations propeller open water efficiency. Moreover, Irrespective of any intrinsic engine in recent years there has been a growing improvements in specific fuel oil awareness of the effects of underwater consumption, provided there are no propeller radiated noise on marine mammals restrictions on propeller diameter and fish. introduced by the ship’s hull or base line clearances, a large diameter, slow turning For some small, high-speed vessels both the propeller will normally give the best overall propeller advance and rotational speeds can propulsive efficiency for a particular be high and the propeller immersion low. In ship design speed. The hull’s ability to these cases it is sometimes not possible to There are three There are other options, when fully controllable pitch propeller. The choice of accept such a propeller, in relation to hull adequately control the effects of cavitation integrated with the prime mover propeller type should be determined from clearances and in providing good inflow acceptably within the other design classes of characteristics, that can enhance ship the ship’s operational profile and the desire into the propeller without creating unduly constraints and thrust breakdown or serious propulsor: fixed propulsion efficiency and thereby reduce for optimisation of fuel usage together with high pressure impulses on the hull from blade material cavitation erosion may emissions given the correct circumstances. any special ship service requirements such cavitation growth and collapse on the result. To overcome this problem partially or pitch propellers; These include the propulsor type and as manoeuvring, vibration reduction, noise propeller blades, is a major determinant super-cavitating propellers sometimes find controllable characteristics; a range of energy-saving emissions or shallow water operation. when designing for efficiency. These latter application. However, with these propellers devices; hull form design; hull coatings and aspects have been accentuated in recent there can be an efficiency penalty since the pitch propellers appendage design and configuration. Fixed pitch propellers, Figure 4.1, have years by increases in power transmitted blade section forms are no longer minimised and ducted traditionally formed the basis of propeller per shaft; the tendency today in many ships for drag but are designed to attenuate production. This class of propellers to locate deckhouses at the aft end of the the worst consequences of the cavitation propellers 4.1 Propulsors embraces those weighing only a few hull above the propeller; the maximization environment. For even more onerous kilograms, normally for use on small power- of the cargo carrying capacity, which propulsion conditions surface piercing boats, to those destined, for example, to imposes constraints on ships’ hull lines; propellers may be deployed which provide Several propulsor types are available propel large container ships, sometimes ship structural failure and international a means of maintaining a reasonable for ship and marine vehicle propulsion. weighing in excess of 130 tonnes. Design legislation. propulsion efficiency. This again underlines The majority, however, fall into three philosophies normally focus on propeller classes: fixed pitch propellers, which are efficiency where the open water efficiency by far the greater proportion; controllable ranges from around 50% for large full pitch propellers and ducted propellers, form tankers and bulk carriers through to which normally include either a fixed or 70 or 75% for some finer hull form, faster Cavitation The underlying physical process which produces cavitation, at a generalised level, can be considered as an extension of the well-known situation in which a kettle of water will boil at a lower temperature when taken to the top of a mountain. In the case of propeller cavitation, if the pressure over the blade surfaces falls to a too low a level during one revolution

then cavitation will form at sea water temperature. When Cavitation on a LNG the cavitation collapses, often very rapidly, at some later ship’s propeller point in the revolution then radiated pressures result which may cause unacceptable ship structural vibration and noise some distance from the ship. Moreover, if sufficient energy transfer takes place during the cavitation collapse process then erosion of the blade material may occur. Depending on the energies involved this may either give rise to erosion which fully penetrates the blade in a short time or may Figure 4.1 A cruise ship’s starboard fixed pitch simply roughen the material surface. Even in this latter case Cavitation induced propeller this may be sufficient to increase the propeller blade drag. material erosion [Courtesy J.S. Carlton]

54 Royal Academy of Engineering Future ship powering options 55 Further propulsion considerations

the need for a ship engineering systems overall efficiency over the entire operational approach to the ship design problem: profile. Apart from providing a means of particularly in achieving the appropriate enhancing overall efficiency in this way, the combination of power absorption, shaft controllable pitch propeller has advantages rotational speed, ship speed and inflow to in ship manoeuvring or dynamic positioning the propeller together with adequate hull situations. While for most seagoing ships clearances and static pressure. fixed and controllable pitch propellers provide acceptably efficient propulsion Figure 4.3 A contra- Controllable pitch propellers provide, solutions, a further propulsor variant is the rotating propeller unlike fixed pitch propellers whose only ducted propeller. system incorporating operational variable is rotational speed, an a podded propulsor [Courtesy ABB] extra degree of freedom because in addition Ducted propellers comprise two principal to possible rotational speed changes the components: an annular duct surrounding blades have the ability to change blade a propeller which operates inside the duct. pitch; Figure 4.2. Nevertheless, for some These propulsors have found extensive trainable about a common pod strut. propeller configuration. Contra-rotating propulsion applications, particularly those application where high thrust at low speed Azimuthing thrusters have been in propellers have been of considerable involving shaft-driven generators, it may is required; typically in anchor handling, common use for many years for dynamic theoretical and experimental interest as be desirable from an overall efficiency towing and trawling situations when the positioning and situations where high well as having been the subject of some full point of view for the shaft speed to be held duct contributes some 40 to 50% of the levels of manoeuvrability are needed. The scale development exercises. While they constant and vary the power absorption by propulsor’s total thrust at or near zero essential difference between azimuthing have found significant application in small adjusting the blade pitch: thereby, reducing ship speed. Ducts, in addition to being propellers and a further variant, the high-speed outboard units, the mechanical the number of propeller operating variables fixed structures rigidly attached to the podded propulsor, is where the engine problems associated with two long shafts to one. While this latter arrangement can be hull as seen in the Figure, are in some or motor driving the propeller is sited: if rotating co-axially in opposite directions helpful for overall energy efficiency, it may cases designed to be steerable which the engine or motor driving the propeller have generally precluded them from wider introduce additional cavitation difficulties. then obviates the need for a rudder since is sited in the ship’s hull then the system is use. Interest in the concept has been cyclic, the thrust can then be vectored by the termed an azimuthing propulsor and most however, an upsurge in interest in 1988 Where two or more design operating points azimuthing duct. commonly the mechanical drive would be resulted in a system being fitted to a 37,000 are required for the ship, controllable pitch of a Z or L type to the propeller shaft. In dwt bulk carrier and subsequently to a propellers may provide a better solution As an alternative to steerable ducted the case of a podded propulsor, the drive 258,000 dwt VLCC in 1993. More recently in terms of efficiency by accepting some propellers there are either non-ducted system comprises an electric motor directly a variant of the original contra-rotating efficiency penalty in particular operation or ducted azimuthing propulsors where coupled to a propeller shaft, supported concept has been proposed and fitted to conditions in order to achieve a higher both propeller and duct, if fitted, are on a system of bearings, in the pod. The some ships. This comprises the combination propellers associated with these latter of a traditional propeller, driven from a propulsors have been of the fixed pitch, conventional line shaft, as the forward non-ducted type, whereas azimuthing member of the pair with a podded propulsor units have either fixed or controllable pitch acting as the astern component: Figure 4.3. propellers. Currently, the largest size of Furthermore, such an arrangement has podded propulsor unit is around 23 MW and the potential benefit of removing the need their use has been mainly in the context of for a rudder since the azimuthing podded cruise ships and ice breakers, where their propulsor provides the steerage capability manoeuvring potential is fully exploited. for the ship.

The contra-rotating propeller principle, Cycloidal propeller development started in comprising two coaxial propellers sited the 1920s, initially with the Kirsten–Boeing one behind the other and rotating in and subsequently the Voith–Schneider opposite directions, has the hydrodynamic designs. They comprise a set of vertically advantage of recovering part of the mounted vanes, six or eight in number, Figure 4.2 Controllable slipstream rotational energy which would which rotate on a disc mounted in a pitch propeller testing. otherwise be lost in a conventional single horizontal or near horizontal plane. The This photograph is reproduced with the permission of Rolls-Royce plc, © Rolls-Royce plc 2013

56 Royal Academy of Engineering Future ship powering options 57 Further propulsion considerations

Figure 4.4 Typical fast ferry application of waterjet propulsion

vanes are constrained to move about their Yamato 1. This 150-tonne craft used liquid spindle axis relative to the rotating disc in a helium-cooled superconducting magnets to predetermined way by a governing linkage. achieve the required high magnetic fields; While having comparatively low efficiency, however, the achieved speed was around vertical axis propellers have significant 8 knots. advantages when manoeuvrability or station keeping is a high ship operational An anticipated benefit of MHD drives priority since the resultant thrust can was that they were expected to be near be varied and readily directed along any silent in operation and hence became of navigational bearing. considerable interest to the submarine community. However, in practice this Waterjet propulsion has found application proved not to be the case. The production on a variety of small high-speed craft and of bubbles at the electrodes creates ferries while its application to larger craft is broadband noise emissions that span a growing with tunnel diameters of upwards frequency range from 2kHz to 20 kHz and of 2 m. Waterjets, Figure 4.4, potentially beyond, but with most of the energy in the offer a relatively efficient solution in difficult range 2kHz to 6kHz. This noise is created hydrodynamic situations for conventional principally through coalescence of bubbles propellers together with very good having diameters between 0.075mm manoeuvrability. and 0.15mm which become spherical as they move away from the walls of the Magnetohydrodynamic propulsion duct and hence become effective omni- can provide a means of ship propulsion directional acoustic sources. Although MHD without the need for propellers or paddles. principles have been used successfully in It is based on the Lorentz force equation electromagnetic rail guns and in liquid metal derived in the 19th century. The idea pumps, they have proved less successful for of electromagnetic thrusters was first marine propulsion. patented in the USA in 1961 (Rice 1961). In the early 1990’s Mitsubishi Heavy Industries built the MHD powered demonstration ship

58 Royal Academy of Engineering Future ship powering options 59 Further propulsion considerations

efficiency enhancements in specific ship 4.2 Energy-saving applications. The devices are directed MagnEtohydrodynamic Propulsion devices towards different ship types and flow The Lorentz force equation can be written as configurations and have some merit in their particular areas of application. Energy-saving devices based on F = e[J + (v x B)] However, due to the complexities of the hydrodynamic interaction can be considered flow in the ship’s afterbody region, many as operating in three basic zones of the hull: where J, B and v are vectors defining, respectively, electric and magnetic fields and the velocity v of require a combination of model testing, before the propeller; at the propeller station the charge carriers. It states that a force F is experienced by a charge of magnitude e equal to the computational fluid dynamic and classical and after the propeller. However, some vector sum of that due to the electric field, eJ, and that due to the motion of the charge through any analysis to optimize their performance. It devices overlap these somewhat artificial additional magnetic field, e(v x B). Here v x B is the vector cross product of v and B and creates a has to be realised that if some devices are boundaries. Those acting just ahead of force vector normal to the plane containing vectors v and B. In its simplest configuration, the electric used outside of their intended fields of the propeller are interacting with the final and magnetic fields are arranged orthogonal to each other with the normal to their plane pointing in application, disappointing results can occur. stages of the ship’s boundary layer growth. the direction of the desired thrust. The electric field J leads to the transport of charge across the duct As such, care in application is essential. This is to gain some direct flow-related and hence creates the velocity field v necessary to produce the axial thrust from the cross product of benefit or present the propeller with a v and B. It is also pertinent to consider whether more advantageous flow regime in which the various energy-saving devices are to operate: in some cases both. Devices at compatible with each other so as to enable a the propeller station and downstream are Internal duct flow cumulative benefit to be gained from fitting operating within both the hull wake field Induced current several devices to a ship. In general this is and its modification by the slipstream of the density J not the case because some devices remove propeller. In this way they are attempting or alter the flow regimes upon which others to recover energy which would otherwise Lofantz force depend. However, if devices depend on J x B be lost. different regions of the flow field around the ship and are mutually independent, Table 4.1 includes some of the more it can be possible to deploy them in common flow augmentation devices combination in order to gain an enhanced most of which aim to achieve propulsive benefit. Magnetic fieldB Water flow

Magneto-hydrodynamic operation principle

Energy saving and flow conditioning device operation 2 Wake equalizing duct The thrust of an MHD drive is proportional to sB where s is the conductivity of the liquid being pumped; in the case of a ship this being sea water. The necessary magnetic fields can be large even Asymmetric stern by modern standards. For torpedoes with a high top speed it may be necessary to create fields in Grothuis spoilers the range 15T to 20T, however, for ships and submarines at typical speeds the magnetic field can be Semi or partial stern tunnels Devices which operated on the flow lower, around 5T to 10T. This, however, raises serious concerns around magnetic stealth in relation before the propeller. Mewis ducts to warships.

Reaction fins The electric field has certain detrimental consequences. Unlike fresh water, in which hydrogen Mitsui integrated ducted propellers appears at the cathode and oxygen at the anode, in seawater trace elements which typically are Hitachi Zozen nozzle ions of sodium, chlorine, magnesium, sulphur, potassium and calcium give rise, in addition to oxygen, Increased diameter/low rpm propellers to the production of other chemical species and to chlorine gas at the anode. The high pH at the

Propellers with end plates cathode leads to scale production, typically of calcium hydroxide or magnesium hydroxide, which are Operation at the propeller electrically insulating. Consequently, over a period of a few days the current can reduce by 12% and Keppel propellers with it the effectiveness of the drive. Where copper or aluminium anodes have been used, these can Propeller boss cap fins be severely corroded as CuO2, AlO2, or their chlorides are produced and hence careful selection of Grim vane wheels electrode material is necessary. The electrolysis process produces gases at the electrodes and these Devices operating just behind or at the Additional rudder thrusting fins have the effect of blanketing the electrodes and hence the cathode is best placed at the bottom of Table 4.1 Energy saving propeller and flow conditioning the duct to encourage hydrogen to rise into the induced flow and be swept out of the duct. Rudder bulb fins devices [Carlton, 2012]

60 Royal Academy of Engineering Future ship powering options 61 Further propulsion considerations

Within the Ship necessary compromises that have to be and temporary roughness. The former and, while relatively expensive, can be 4.3 Hull design and made between resistance and propulsion, refers to the amount of unevenness and effective in preventing fouling when used design process stability, seakeeping and manoeuvrability condition of the hull plating in terms of the in the correct circumstances. Many of appendages in order to meet the desired operational bowing of the ship’s plates, weld seams and these products are under evaluation by it is important profile. During this process, it is essential to the condition of the steel surface, while the shipowners to see how well they satisfy recognise that the propulsor has to operate latter principally accounts for fouling and their particular needs: among other to consider A ship’s propulsive efficiency comprises within the flow field generated by the hull deposits that build up on the hull surface. factors, these relate to application cost, three components: propulsor open water alternative and by not taking due recognition of this, durability and effectiveness in minimising efficiency, hull efficiency and the relative hull design decisions may be taken which Fouling commences with slime, comprising fuel consumption within the operational design solutions rotative efficiency. The latter component ultimately inhibit the propulsor design from bacteria and diatoms, which then spectrum. is small since it is the ratio of the torque and not simply attaining the best efficiency. This underlines progresses to algae and in turn on to animal absorbed by a propeller in open water the need for a holistic systems approach to foulers such as barnacles, culminating in Research work is progressing to find follow accepted to that when working in the wake field ship hydrodynamic design. the climax community. In this cycle (Christie ecologically friendly alternatives. One such wisdom behind the ship. In general, the first two 1981) the colonization by marine bacteria method is based around electrochemically components are dominant and propeller Within the design process it is important on a non-toxic surface is immediate, their active coating systems. This concept open water efficiency is generally to consider alternative design solutions numbers reaching several hundred in a few produces regularly changing pH values considered in Section 4.1. and not simply follow ‘accepted wisdom’. minutes, several thousand within a few on the surface of the hull and thereby An example of this is to be found in hours and several millions within two to effectively prevents fouling colonization The hull efficiency is governed by the hull recent research into tanker design where three days. Diatoms tend to appear within without having to use biocides (Fraunhofer form and its principal dimensions. These convention might dictate a hull block the first two or three days and then grow 2012). Initial tests have been promising in are subject to a number of constraints in coefficient in the region of 0.82 for a 250m rapidly, reaching peak numbers within the proving product stability and efficiency in addition to those imposed by the principles long ship. However, model tests have first fortnight. Depending on the prevailing preventing bio-fouling. of ship hydrodynamics. For example, ship suggested that a solution which relaxes the local conditions, this early diatom growth length may be a commercial function length constraint slightly and in conjunction may be overtaken by fouling algae. The Research has been undertaken over many of nominal berth length; hull draught with a block coefficient of 0.63 enhances mixture of bacteria, diatoms and algae in years to endeavour to minimise frictional restrictions due to port water depths; the performance in both the ballast and this early stage of surface colonization is drag. Methods involving the injection of breadth by safe navigation in channels or loaded conditions with estimated potential recognized as the primary slime film. The small quantities of long-chain polymers into through locks and in the case of container fuel savings of around 8.8 tonnes/day. fouling community which will eventually the turbulent boundary layer surrounding ships, the outreach of the dockside cranes. establish itself on the surface is known as the hull, such as polyethylene oxide, Additionally, there may be constraints the climax community and is particularly were shown in the 1960s to significantly imposed by the building dock. These and dependent on the localized environment. reduce resistance, provided the molecular other similar factors have to be recognised In conditions of good illumination this weight and concentration were chosen but, nevertheless, challenged for validity 4.4 Hull coatings community may be dominated by green correctly. Those methods which relied on in an attempt to achieve the most algae, barnacles or mussels. the injection of chemical substances into hydrodynamically efficient hull form. If this Hull coatings and roughness play an the sea along the hull surface are unlikely design optimisation is not done effectively important part in the minimisation of the The tin-based marine coatings, particularly to be environmentally acceptable today. the ship will inevitably carry an efficiency skin friction component of resistance. This tributyltin (TBT), were excellent in Nevertheless, current research is focusing penalty by not being correctly optimised. is a significant component of the total keeping underwater hull surfaces free on a range of methods involving boundary resistance as seen from Table 4.2 (Carlton of fouling and, in so doing, reducing layer fluid injection and manipulation. Once valid design constraints have been 2012). Hull surface roughness comprises the fuel consumption. However, they These typically embrace the injection of established the hull form can be effectively sum of two elements; permanent roughness were exceedingly detrimental to the low-pressure air either to develop a micro- designed: a process which is based on the environment and were eventually banned bubble interface between the hull and the in 2008 following discussion at IMO MEPC. sea water or through the provision of an air Currently a number of alternative marine cushion trapped by an especially developed Ship type Frictional to total resistance ratio paints have come on to the market such hull form. Further research is exploring the ULCC 516893 dwt (loaded) 0.85 as copper-based and synthetic biocide frictional resistance benefits obtainable Crude oil tanker 140803 dwt (loaded) 0.78 paints; nevertheless, further work is from the texture of hull coatings and in (ballast) 0.63 proceeding to find alternatives. Silicon- some cases endeavouring to emulate the Products tanker 50801 dwt (loaded) 0.67 based paints have also been marketed skin of marine mammals and fish. Container ship 37000 dwt 0.62 Table 4.2 Comparative importance of frictional Cruise ship 0.66 resistance with respect Ro/Ro ferry 0.55 to ship type

62 Royal Academy of Engineering Future ship powering options 63 Further propulsion considerations

4.5 Superconducting Despite being discovered over 100 High temperature years ago, superconductivity remains The discovery of superconductivity, in 1911, is credited to Heike Kamerlingh-Onnes. He spent his superconductors electric motors an active area of fundamental research. career exploring extremely cold refrigeration techniques and, in 1908, was the first to liquefy helium However, it is not unreasonable to expect which he used to study platinum and gold at very low temperatures – but without detecting what were discovered that superconducting motors operating would become known as superconductivity. He then turned to mercury and at about 4.2°K the Although large conventional electric at commercially accessible cryogenic resistance of his mercury sample dropped from 0.11Ω to less than 10-5Ω. This sudden and significant in 1986, but their motors are efficient, superconducting temperatures, and constructed using an drop in resistance is a signature of superconductivity and the temperature at which it occurs is the motors can be more efficient, around 99% production affordable wire, will become available critical temperature. Shortly afterwards superconductivity was also discovered in tin and lead and in – especially when running at less than in the next decade or two. However, it 1913 Onnes was awarded the Nobel Prize for the discovery of superconductivity. as useful their maximum speed. This improvement takes a significant time for a totally new conductors is can lead to savings in fuel and gaseous superconducting material to become In 1933, Meissner and Ochsenfeld reported that magnetic fields are expelled from superconductors. emissions. Moreover, superconducting available as a useful engineering wire, The appearance of a critical temperature and the Meissner effect are taken as the defining evidence still not fully motors are smaller and more power-dense and most superconducting materials are that a substance is in a superconducting state. than conventional motors of similar power; industrialised inherently unsuitable for this engineering typically around 30 kW/kg compared application. The design of superconducting All superconductors are characterised by three parameters: a critical temperature; a critical magnetic to about 5 kW/kg for a conventional rotating machinery is itself also an active field strength; and a critical current density. If any of these are transiently exceeded the material will motor. Additionally, high-temperature research area, so commercial availability suddenly return to the normal non-superconducting state and possibly serious damage can occur. superconducting motors have signature of this technology must be viewed in the Critical currents and fields depend upon temperature and both, in general, decrease smoothly to zero benefits that are attractive in naval service. medium to long term. as temperature increases to the critical temperature, as shown in the Figure.

In January 2009, the American Some potential advantages and J (A/m2) Superconductor Corporation (AMSC), c disadvantages of the technology: together with the Northrop Grumman Advantages 11 Corporation, announced the successful 10 i. The technology has been shown to be completion of the full-power land-based viable in large demonstrator applications. testing of a 36.5 MW high temperature ii. Losses in the electrical machine are low Niobium-titanium alloy superconductor ship propulsion motor, 109 resulting in a more efficient motor. Nb3Sn (Figure 4.5). However, there are currently Nb Ge iii. Exhaust emissions can be lower. 3 no superconducting motors in use on ships. 108 5 10 v. The size and weight of the electrical Liquid helium 10 20 machine is lower. 15 30 Figure 4.5 Superconductor motors and generators High-temperature superconductors were 20 40 are significantly smaller and lighter than conventional discovered in 1986, but their production 25 50 rotating machines. This photo shows a 36.5 Disadvantages 60 as useful conductors is still not fully Liquid hydrogen megawatt superconductor ship propulsion motor that i. A cryogenic cooling system has to be PbMo S was designed and manufactured by AMSC for the U.S. industrialised: they are expensive and T(K) 6 8 µ H (T) provided for the current and expected o c2 Navy. This machine, which successfully passed land- difficult to make and require particular future generations of machines and based testing, was less than half the size and weight grain alignments. Although a new simpler of a conventional motor of the same power rating. continued operation of the motor will superconductor material, magnesium Photo courtesy of AMSC be dependent on the reliability of the Typical current, field and temperature dependencies of superconductivity. diboride, was discovered in 2001, its lower cooling system. critical temperature and sensitivity to ii. The technology has yet to be proven at High temperature superconductivity was first reported in a paper published in April 1986. This magnetic fields mean that its applicability sea. paper by Bednorz and Muller described an insulating barium-lanthanum-copper-oxygen ceramic to rotating machinery is still a matter of compound with a previously unheard-of critical temperature of 30°K. In less than a year of their research. publication a second compound, this time of yttrium-barium-copper-oxygen (YBCO), was identified with a transition temperature of ~96°K. In 1987, Bednorz and Alexander received the Nobel Prize for their work and an urgent search started for additional high-temperature superconductors. At Despite being discovered over 100 years the present time, many high-temperature superconductors with critical temperatures above 96°K have been identified, and many more completely new classes of superconducting materials have ago, superconductivity remains an been discovered. Nevertheless, the current front-runner for most engineering applications involving active area of fundamental research magnetic fields is YBCO, discovered in 1987, but it has taken more than 20 years to develop effective engineering conductors using it. One difficulty is that the grain alignment required means that the conductors are flat tapes, not round wires, which makes winding coils more complicated and limits the design of coils and hence the machines that can be built using them.

64 Royal Academy of Engineering Future ship powering options 65 Further propulsion considerations

The more advanced systems take into 4.6 Ship operational account the ocean currents, wave and considerations swell composition and wind speeds in their optimisation of the voyage parameters. The resulting track information can then be 4.6.1 Operational profile imported to the ship’s navigation system. In The intended operational profile of a ship, in this way, on board monitoring and decision terms of the proportion of time likely to be support systems can be deployed and an spent at particular speeds, is a fundamental energy-efficient approach to ship operation parameter in forming the design basis of a implemented. Indeed, when arrival times ship and its propulsion machinery. From the are critical these approaches to voyage operational profile the choice of machinery planning help to mitigate the effects of type and arrangement will be made as well the approach common some years ago as the propeller type and its design point(s). of steaming at full speed on departure These parameters, together with the hull for a day or so ‘to get some time in hand’ form, are fundamental to the determination against any adverse conditions that might of the basic overall efficiency of the ship. subsequently be encountered during the voyage. Recognising the approximately 4.6.2 Weather routing cubic relationship of power with ship speed, in the presence this is seen as a very expensive practice, of adverse The underlying purpose of weather routing both economically and environmentally. is to establish the optimum track for long weather, the distance voyages, since, in the presence of 4.6.3 Plant operational practices shortest route adverse weather, the shortest route is not always the fastest or the most economic. The condition of the ship’s machinery has is not always the This is because, notwithstanding the an important influence on the economic fastest or the potential for causing damage (Section 2.3), performance of the ship. Condition maintaining speed in storms or poor monitoring, performance measurement most economic weather causes added resistance due to and maintenance practices are therefore the wind and waves, the magnitude of a critical component in keeping the which is dependent on the severity and plant in optimal condition. Furthermore, direction of the weather relative to the unmotivated crews, for whatever reason, ship. This increases fuel consumption. are unlikely to maintain a ship at its peak Alternatively, if speed is reduced through performance. Alternatively, a poorly adverse conditions, estimated times of designed machinery space with limited a minimum level. These types of capability environmental consequences. Slower ship arrival can be extended with consequent access problems to components can have been under development since speeds can be prescribed for the initial implications for docking slot availability. also be a disincentive to conduct proper the mid-1970s, and with progressive design or as an imposition on an already The principal idea, therefore, is to use maintenance activities. increases in instrumentation and predictive faster design of ship, given that the main updated weather forecast data and choose capabilities have become increasingly more engine’s slow running constraints are an optimal route through calmer sea areas Notwithstanding the influence of poor powerful. There is nevertheless still scope satisfied. In this latter case the propeller or areas that have the most downwind weather on fuel consumption, in a recent for the development of these methods. may also be modified or redesigned to tracks based on predictive and optimisation study centred on a ferry sailing between further enhance the propulsive efficiency methodologies. Such approaches rely Stockholm and Helsinki some 7% less fuel In addition to decision support methods, of the ship because of the lower specific on a knowledge of the ship’s calm water consumption was achieved by optimising there is the ability to sail the ship at slower thrust loading: Section 4.1. The dangers of resistance and added resistance in waves. the ship’s speed during the passage in speeds with the attendant advantage of under-powering a ship, discussed in Section These systems have been deployed in conjunction with crew training. These reductions in fuel consumed. This carries 2, must also be recognised if potentially various forms of complexity over the last savings were achieved using real-time the implication of longer voyage times as hazardous situations are to be avoided. thirty or so years to good effect. However, decision support systems to advise the well as for the accountancy notion of the the increasing sophistication of weather crew about ship operation, route planning cost of goods in transit, but in addition forecasting over that period has permitted a and navigation with the goal of optimising to the fuel savings it also has beneficial continuing enhancement of the technique. energy use and maintaining emissions to

66 Royal Academy of Engineering Future ship powering options 67 Time frame for technical development

5. Time frame for technical development

A range of ship propulsion options have perspectives within the marine and related been considered. While some are applicable industries. The actual progress will be in the short term, others are medium- and dependent on the pace of technological long-term options, due to the necessary development, commercial motivation, technical, commercial and political public perception and political acceptability. developments. Some are unlikely to come to fruition within a reasonable timescale. Appendix 10 considers the applicability of the various options discussed in this report Figure 5.1 develops a perspective on the to a range of ship types. Within these ship likely progress towards maturity of the types, both new and existing ships are propulsion methodologies as seen currently considered as well as operational practice. from the technical and research funding

Short term Medium term Long term

Diesel engine

EGR & SCR systems

Based on Humidification & water injection reciprocating Duel fuel engines engine LNG fuel

technologies Di-methyl ether

Demonstrators Second and third generation biofuels

H2 infrastructure Hydrogen

Gas turbines

Hybrid propulsion

Renewable sources for power augmentation Other propulsion Demonstrators Fuel cells for auxiliary power technologies Superconducting electric motors

H2 infrastructure Fuel cells for main propulsion

Nuclear propulsion Energy storage breakthrough Battery main propulsion

Conventional propulsors

Waterjet propulsion Hydrodynamic New hull forms & energy saving devices Figure 5.1 Potential enhancements New hull coatings phasing of different propulsion technologies MHD propulsion in time

68 Royal Academy of Engineering Future ship powering options 69 Conclusions

therefore good reason to keep machinery Short-term options: well-maintained, particularly in view of In the short term, the diesel engine is 6. Conclusions the increasing levels of complexity. In this currently the most widespread marine prime respect, demotivated crews, for whatever mover for ship propulsion. Moreover, diesel reason, are unlikely to maintain the ship at engine technology is a well-understood its peak performance: conversely, a poorly and reliable form of propulsion and auxiliary designed machinery space which has power generation technology and engine accessibility problems will militate against manufacturers have well-established proper maintenance activities, however repair and spare part networks around well the crew are motivated. the world. There is also a supply of trained engineers and their training requirements The hull and machinery insurance impact are well known and established facilities of most of the systems considered in exist for the appropriate levels of training. this report, with the exception of nuclear In the immediate future methods for The condition It is evident that to optimise the potential With regard to ship operation, it has been propulsion, is likely to be relatively reducing emission levels exist and there benefits of a propulsion option, or demonstrated that weather routing of ships low. Indeed, they are unlikely to merit are continuing programmes of research of a ship’s combination of options, in terms of between ports to avoid poor weather and specific consideration beyond insurers and development being undertaken by machinery has efficiency and minimising the impact storms, with the consequent influence on a understanding any new technology and the engine builders. At present engine on the environment, an integrated ship ship’s added resistance, has important fuel the costs associated with repairs. A caveat builders are generally confident of meeting a significant design procedure based on a systems consumption benefits. Similar benefits are to that, however, could be the market’s MARPOL Annex VI Tier 3 requirements by influence engineering approach must be employed. also realisable when ship speed is optimised previous experience with new systems combinations of primary and secondary Fundamental to this process is the proper during voyages as well as investing in which may encourage underwriters to methods. Furthermore, all grades of fuel on fuel definition of the intended ship’s operational appropriate crew training so they fully impose higher policy deductibles or self have a worldwide distribution network and consumption profile and the perceived tolerance on this understand the implications of actions they insured retentions. Cover might be modified, are readily obtainable. However, there is profile to meet future market fluctuations. may take. In this context, real-time decision or the insured forced to run a higher now some contamination of the marine fuel and emissions When this profile is combined with the support systems with the goal of optimising self-insured retention, in cases of truly supply by first-generation biofuels and this performance anticipated future daily fluctuations in energy use and minimising emissions are prototypical technology. This is because the needs to be carefully managed on board the ship operating and fuel costs, a design helpful in achieving these fuel savings. fear of costly repairs and the prototypical ships. Nevertheless, diesel engines produce space can be defined within which the ship nature of a system may prompt hull and CO2 emissions as well as NOX and SOX, system can be contemplated. Furthermore, There is the ability to invoke slower ship machinery underwriters to restrict cover in volatile organic compounds and particulate anticipated changes in environmental or speeds since this will result in reductions some way and to charge higher premiums to matter, albeit through reduction measures legal frameworks should be introduced into in fuel consumed and have beneficial reflect any new technology. Nevertheless, in reduced quantities. It should, however, be this design space definition. environmental consequences. These the transfer of a land-based technology noted that the quantity of SOX produced is slower speeds can be prescribed for the together with that experience to a marine a direct function of the amount of sulphur Within a ship system design approach, initial design or as an imposition on an environment may help in that respect. present in the fuel burnt. consideration must be given to the already faster design of ship; given that the integration of the various subsystems limitations arising from the main engine’s The adoption of alternative propulsion Natural gas is a fuel that can be used in and their relative influences upon each slow steaming constraints are satisfied. options will be dependent on the price reciprocating engines and is a known other. This should include the prime In this latter case further performance of fuels, the impact of present and technology. Service experience with mover or fundamental power source; fuel benefits can gained from redesigning or future environmental legislation and the dual-fuel and converted diesel engines, characteristics; the hull form together with modifying the propeller to accommodate likelihood of carbon tax introduction. In the albeit limited at the present time, has the challenging of any constraints imposed the resulting lower specific thrust loading. case of fuel price, recent experience has been satisfactory. Indeed, it is relatively upon it; the propulsor type and the creation Notwithstanding any benefits derived from demonstrated a trend towards increase easy to convert many existing marine of conditions to achieve the maximum slow steaming, there is an operational risk superimposed with strong fluctuations. engines to burn LNG and currently this efficiency possible; the minimisation of in fitting ships with too small engines, to However, there is debate whether the fuel is considerably cheaper than the appendage resistance and the inclusion of meet environmental design indices or other presently observed trends will be carried conventional fuels. LNG fuel, while not other appropriate energy-saving devices. criteria, as the ships may have insufficient forward into the future. Set against this free of harmful emissions, has benefits in Furthermore, hull coatings are an essential power to navigate safely in poor weather. background the propulsion options in the terms of CO2, NOX and SOX emissions given engineering consideration in achieving short-, medium- and long-term time frames that methane slip is avoided during the optimal powering, since for many ships The condition of a ship’s machinery has a can be considered. bunkering and combustion processes. In the frictional resistance is a significant significant influence on fuel consumption the worldwide context, there is a general proportion of the total ship resistance. and emissions performance. There is lack of a bunkering infrastructure at

70 Royal Academy of Engineering Future ship powering options 71 Conclusions

present, although LNG has been used to Medium- to long-term options of nuclear reactors with ready-made Batteries, by virtue of the rapidly developing Gas turbines have good effect in certain short sea and coastal Biofuels are a potential medium-term Batteries, by elements would be accomplished under technology surrounding them, offer a successfully trades. Additionally, there are now moves alternative to conventional fuels for diesel virtue of the term contracts rather than on-the-spot potential solution for ship propulsion. Full to establish larger bunkering facilities at engines, although with the first generation market. Furthermore, a significant body battery propulsion must, however, await been used in niche major international ports and some large of biofuels, biodiesel and bioethanol, some rapidly developing of experience exits in the design and safe further technical development, and even areas of the commercial ships are currently in service or issues have been experienced when used technology operation of shipboard nuclear propulsion then it is likely to be confined to the small on order to utilise LNG fuel. in marine engines. For the future, synthetic plant: particularly in the case of PWR ship market. At present the size of the marine market fuels based on branch-chain higher alcohols surrounding them, designs. The conventional methods of necessary battery pack would preclude their and represent Gas turbines have successfully been used and new types of microorganisms and algae offer a potential design, planning, building and operation use as the sole means of propulsion in all in niche areas of the marine market and are a medium- to long-term possibilities of merchant ships would, however, need but the smallest of ships undertaking short a proven high represent a proven high power density given that production volumes can satisfy solution for complete overhaul, since for a nuclear sea voyages. Nevertheless, battery-based power density propulsion technology. In particular, their the demand from the marine and other ship propulsion. propelled ship the process would be driven propulsion would be beneficial from the CO2, low weight gives considerable flexibility markets. It will, however, be necessary by a safety case and systems engineering NOX, SOX, volatile organic and particulate propulsion when locating them in a ship in the context to examine in greater detail aspects of Full battery approach. There would, however, be a emissions points of view since none occur technology of turbo-electric designs. However, the the storage, fuel handling, and impacts propulsion must, number of constraints imposed on ship during operation. Batteries in conjunction high distillate grades of fuel for aero- on health, safety and the environment. design and operation as well as on the with other modes of propulsion may offer a derivative gas turbines are expensive Di-methyl ether also shows potential as an however, await deployment of this technology, all of potential hybrid solution for the propulsion when compared to conventional marine alternative fuel, but at present there are further technical which would need resolution. These of small- to medium-sized ships. fuels and their thermal efficiencies are disadvantages which require resolution in include international nuclear regulation; lower than for slow speed diesel engines terms of lubricity and corrosion together development, design execution and planning, operation, With regard to hydrogen, compressed air of similar power. These can be enhanced, with creating a sufficient production and and even then training and retention of crews and and liquid nitrogen, these are likely to be however, in combined cycle installations supply capability. shore staff, security, public perception, long-term propulsion options. While the where the exhaust heat is used to develop it is likely to be disposal; financing the initial capital cost; latter two options are energy storage additional power. Fuel cells offer potential for ship propulsion, confined to the the setting up and the maintenance of an media, hydrogen is a fuel which generates and at the present time, encouraging infrastructure support system. Insurance no CO2 or SOX emissions to the atmosphere Renewable energy sources are free from experience has been acquired with auxiliary small ship market is a serious issue for nuclear merchant and could use land-based renewable exhaust pollutants. However, wind-based and low-power propulsion machinery. For ships, and while the insurance industry is a sources of power for its creation. Hydrogen solutions tend to be limited to propulsion marine propulsion, the high-temperature service industry, this would need resolution has a number of safety issues associated augmentation roles unless a full return to solid oxide and molten carbonate fuel cells as governments are unlikely to enter this with it and has a low energy density but is sail is contemplated in specific applications. show most promise, while for lower powers market as they do for naval ships. Within the ideal for use in fuel cells or could be burnt Wind power systems rely on the wind the low-temperature proton exchange discussion it has been seen that the concept in suitably modified reciprocating engines. strength to be effective and the use membrane fuel cells are more suited. of small modular marinised reactor plants or To be viable as a marine fuel, it would need of some systems are dependant upon Hydrogen is the easiest fuel to use in fuel molten salt reactors may attenuate many a supply infrastructure, and at present it adequate control system technology being cells but this would require a worldwide of these difficulties although not dispose of is largely untried in the marine industry installed on board the ship. Solar energy is infrastructure to be developed for supply to them. As such, it would be prudent to keep a for propulsion purposes. Clearly, should a feasible as a source of auxiliary power but ships. Methanol is a possible alternative, but watching brief on the development of these hydrogen economy evolve at some time in photovoltaic processes inherently have the use of more conventional marine fuels technologies with a view to implementation the future then it would be a marine fuel low effectiveness and require a significant would present problems and necessitate in the medium to long term. option. deck area upon which to place an array of complex onboard pre-processing to take cells. Although solar-derived power is place. Since fuel cells produce a DC electrical Superconducting electric motor technology In the case of compressed air and liquid global position and weather dependent, output, they would be better suited for has been shown to be viable in land-based nitrogen they would, again, use land-based it has been demonstrated to augment ships with hybrid or full electric systems. demonstrator applications up to 35MW, and sources of power for creation and the tank auxiliary power. since the electrical losses are low, result storage technologies are well understood. The propulsion of ships by nuclear power in a more efficient motor. Depending upon Nevertheless, the size, pressure rating and has the advantage during operation of the type of prime mover deployed, exhaust cryogenic capabilities, in the case of liquid

producing no CO2, NOX and SOX, volatile emissions will therefore be lower and if nitrogen, of the ship storage tanks would organic and particulate emissions. a coolant failure occurs, the machine can determine the amount of energy storage Additionally, the cost of uranium has run for some time after the failure. Some and hence usefulness of the concept. been relatively cheap in comparison to advantage might also accrue from the Moreover, there is an attendant blast risk conventional marine fuels and the refuelling smaller physical size of the electric machine. with high-pressure gas tanks should

72 Royal Academy of Engineering Future ship powering options 73 Conclusions

fracture initiate and, moreover, corrosion iii. In the case of ships contemplated for the If, in the future, can be an issue in salt-laden environments medium to long term, further propulsion a hydrogen with high-pressure tanks. As with hydrogen, options will present themselves including a supply infrastructure and distribution fuel cells, batteries and nuclear. The economy is network would need to be developed, former methods await technological adopteD, then recognising that air is part of the natural development but nuclear, while well- environment whereas nitrogen has to understood technically, would require hydrogen may be made. a major change to ship building, become an owning and operation infrastructure Magnetohydrodynamic propulsion is not and practices together with a suitable alternative seen as being viable in anything but the long international regulatory structure. marine fuel term for merchant ships. Renewable sources such as wind and solar option In the context of the current and future are augments to power requirements, merchant marine fleets it is considered that: assuming a return to full sail propulsion i. For existing ships reciprocating is not contemplated. If, in the future, engines with exhaust gas attenuation a hydrogen economy is adopted, then technologies are the principal option hydrogen may become an alternative together with, if so desired, fuels having marine fuel option.

less CO2 emission potential. LNG is one such fuel and together with some Underpinning these possible alternatives other future alternatives requires an is a need for further soundly based adequate bunkering infrastructure to techno-economic studies on target be developed, particularly, for deep sea emissions from ships. voyages.

ii. For presently contemplated newbuildings the scenario is broadly similar but with the option to include hybrid propulsion systems depending on the ship size and its intended duty cycle.

74 Royal Academy of Engineering Future ship powering options 75 Glossary of terms References

Andriotis et al. 2008. Andriotis, A., Gravaises, M. and Arcoumanis, C. Jakobsen 2012. S.B. Jakobsen Fuel Optimisation on 2-Stroke Engines, Acronyms Chemical substances Vortex flow and cavitation in diesel injector nozzles, 3rd Propulsion Conf., Trans IMarEST, London 2012 AIP Air independent propulsion CH4 Methane Journal of Fluid Mechanics, Vol 610, pp195–215, 2008 Lamb 1948. Lamb, J. The burning of boiler fuels in marine diesel AUV Autonomous underwater vehicle CO Carbon dioxide 2 Arcoumanis et al. 2008. Arcoumanis, C., Bae, C., Crookes, R. and engines. Trans IMarE, Vol.LX, No 1. (1948) CIMAC International Council on Combustion Engines H2 Hydrogen Kinoshita, E. The potential of di-methyl ether (DME) as an Lambert, A. 2008. Admirals. Faber & Faber. CMAL Caledonian Marine Assets Ltd H O Water 2 alternative fuel for compression-ignition engines: A review. ISBN 978-0-571-23156-0 DC Direct current NOX Oxides of nitrogen Fuel 87 (2008) pp1014–1030 Larminie and Dicks, 2000.Larminie, J. and Dicks Fuel cell systems DFDE Dual fuel diesel-electric [propulsion systems] SOX Oxides of sulphur BP 2012. Statistical Review of World Energy 2012. BP 2012 explained. Wiley, Chichester ISBN 0 471 49026 1 DME Di-methyl ether Th Thorium Bunkerworld 2012. Bunkerworld Index, 22nd October 2012 Lloyd’s Register 2011. Bio-fuel Trials on Seagoing Container Vessel. DNV Det Norske Veritas 235u uranium isotope 235 Carlton 2012. Carlton, J.S. Marine Propellers and Propulsion. Maersk-Lloyd’s Register-Shell Research Consortium SMIG dwt Deadweight [of a ship] YBCO Yttrium-Barium-Copper-Oxide Butterworth-Heinemann, 3rd Edition, 09004, Lloyd’s Register, July 2011 ECA Emission control area ISBN 978-0-08-097123-0, 2012 Lloyd’s Register. 2012. Lloyd’s Register LNG Bunkering EEDI Environmental energy design index Units Christe 1981. Christie, A.O., Hull roughness and its control. Marintech Infrastructure Study. Lloyd’s Register, London February EEOI Energy efficiency operational index bar bar [Pressure:1 bar = 0.9869 Standard Atmospheres] Conference, Shanghai, China, 1981 2012. EGR Exhaust gas recirculation C Centigrade CIMAC, 2011. Guidelines for Ignition and Combustion Quality, Loginow A.W., 1989, Stress Corrosion Cracking of Steel in Liquefied EU European Union cSt centistokes [Kinematic viscosity: 1cSt = 1m2/s] CIMAC, 2011 Ammonia Service – A Recapitulation, http://www. FAME Fatty acid methyl esters h hour Committee on Climate Change 2011. Review of UK Shipping nationalboard.org/Index.aspx?pageID=182 GT Gross tonnage Hz Hertz [Cycles/second] Emissions, November 2011. MacKay 2009. MacKay, D. -Without the Hot Air. HFO Heavy fuel oil J Joules [Energy: 1 Joule = 1 Newton.m] Cooper 2012. Cooper, Captain N. 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Fuel cells for ships: Research and Innovation, Position Paper 13, DNV Oslo, 2012. http://www.dnv.com/binaries/ 2001/2002 MOL(Japan): Environmental and Social Report LPG Liquid petroleum gas N Newton [Force: 1 N = 0.10197 kilograms force (kgf)] fuel%20cell%20pospaper%20final_tcm4-525872.pdf 2004 MARPOL marine Pollution Convention [IMO] nm Nautical mile Dundee 2007. The Uranium Sector – Primary Supply Fundamentals: Pomeroy, R.V. 2010. 250 Years of Marine Technology Development. MCFC molten carbonate fuel cell pH Logarithmic measure of acidity [pH=1 Acid; pH=12 Alkali] A Re-Examination. Dundee Securities Corporation, Proc. Lloyd’s Register Technology Days 2010. Lloyd’s MCR maximum continuous rating [of an engine] ppm parts per million August 30, 2007 Register, London MEPC marine Environmental Protection Committee [IMO] rpm revolutions per minute EC 2002-2006. European Fuel Cell and Hydrogen Projects Rice 1961. Rice, W.A. 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76 Royal Academy of Engineering Future ship powering options 77 Appendices

Appendices

Appendix 1 Appendix 2 Terms of reference Membership of the working group

The terms of reference of the Royal Academy of Engineering’s Alternative Methods of Chairman Ship Propulsion Working Group are as follows: Professor JS Carlton FREng City University London

1. To assess the future prospects of current methods of merchant ship propulsion in Members terms of environmental impacts and sustainability. Mr J Aldwinkle Anthem Corporate Finance 2. To explore the feasibility of employing alternative means of propulsion for merchant Mr J Anderson Caledonian Marine Assets ships with particular focus on nuclear power. These alternative means are to be Professor C Arcoumanis FREng City University London placed within the contexts of other existing or known potential ship powering Mr D Balston Chamber of Shipping options. Mr A Bardot International P&I Clubs 3. The working group is to comprise representatives from a range of marine and other Mr C Beall Shell Shipping Technology related and interested communities based either in the United Kingdom or abroad. Mr M Bowker Institute of Marine Engineering, Science and Technology 4. A broad range of ship types, sizes and trading patterns are to be considered. Professor R Bucknall University College London 5. The scope of the discussions are to include, but not necessarily be limited to, the Mr W Catford Surrey University technical, operational, commercial, regulatory, risk, legal, environmental, public Mr J Cheetham Lloyd’s Register acceptability, and health and safety considerations. Mr J Clench City University London

6. Publicly available reports are to be produced at appropriate stages in the work of the Mr S Clews BP Ltd working group. Mr D Davenport-Jones American Bureau of Shipping Mr M Drayton The Baltic Exchange 7. The governance of the working group is to be vested in an elected Chair and Deputy Chair in whom and through whom the terms of reference are to be implemented and Mr A Duncan Caledonian Marine Assets publications authorised in accordance with the requirements of the Royal Academy Mr M Edmondson Chubb Insurance of Engineering. Dr M El-Shanaway International Atomic Energy Authority Mr S Firth MOD(N) Submarine Operating Centre Mr D Forbes Rolls Royce plc Mr A Goldsworth Rolls Royce plc Dr A Greig University College London Rear Admiral N Guild FREng Engineering Council Mr S Hall American Bureau of Shipping Mr D Hankey BAE Systems Ms E Hauerhof City University London Mr V Jenkins Lloyd’s Register Mr C Joly Carnival CTS

78 Royal Academy of Engineering Future ship powering options 79 Appendices

Mr G Kirk IED Nottingham University Appendix 3 Mr R Lockwood Nuclear Institute Professor D MacKay FRS Chief Scientific Advisor, DECC Referee and review group Dr J Kang Samsung Heavy Industries Co Ltd Vice Admiral Sir Robert Hill KBE,FREng Safety, Reliability and Marine Consultant Mr P Nash Royal Haskoning DHV Mr B Cerup-Simonsen Maersk Maritime Technology Professor M Newby City University London Professor D Stapersma Delft University of Technology Ms P Oldham Institution of Mechanical Engineers Mr R Taylor FREng National Nuclear Laboratory Mr W Page Wärtsilä UK Ltd Mr R Vie Carnival Shipbuilding Mr SM Payne OBE, FREng Consultant (Chairman of Working Group in 2009) M J-P Roux Areva TA Dr P Sargent DECC Mr R Smart Lloyd’s Register Mr D Strawford Carnival CTS Mr M Tetley Nuclear Risk Insurers Ltd Professor S Turnock University of Southampton Mr R Vallis BAE Systems Marine Division Mr A Walker Royal Academy of Engineering Dr A Watt University of Glasgow and Strathclyde Mr G Wright MOD(N) Submarine Operating Centre Professor P Wrobel FREng University College London

80 Royal Academy of Engineering Future ship powering options 81 Appendices

Appendix 4 Appendix 5 Statement from Vice-President of the European Commission A ship systems approach SiimKallas and EU Commissioner for Climate Action Connie Hedegaard, October 2012. One starting point for a ship systems approach is Safety to consider the plant requirements and undertake Financial costs a stakeholder mapping exercise. However, the ship Market influences “Shipping is a global industry and needs global solutions to address its environmental owner is only one of a complex network of stakeholders Stakeholder requirements footprint. As a result, we are all working towards an internationally agreed global relating to the ship and its operation and their collective Technical development risks solution to decrease greenhouse gas emissions from ships. The International desires and requirements have to be relaxed such that Management understanding Maritime Organisation made a significant and highly welcome step forward in July a common perspective is reached. Capturing the views Warranty and servicing costs 2011 with the Energy Efficiency Design Index. But this measure alone – which of these bodies can be difficult, but if it is not done Legal and statutory implications is applied only to new ships from 2015 – will not be enough to ensure shipping effectively then key requirements may be missed and, Public liability and insurance costs emissions are reduced fast enough. Discussions about further global measures are if significant, there is a high probability that the ship ongoing at IMO level, but we need intermediary steps to quickly deliver emissions may be unable to effectively trade. Table A5.1 Risk factors in new propulsion developments reductions, such as energy efficiency measures also for existing ships.

The mode of operation required will determine a ship’s There are different types of risk: human risk; At EU level, we consider several options, including market-based mechanisms. specific design requirements. This will impose different technological risk; process risk and financial risk. A simple, robust and globally-feasible approach towards setting a system for requirements on the ship’s subsystems, including the Technical risk relates to the deployment of novel or monitoring, reporting and verification of emissions based on fuel consumption is prime source of power. These requirements, in turn, variations of proven technology and the consequent the necessary starting point. This will help make progress at a global level and feed will be heavily dependent upon the meta-solution, availability of the ship to undertake its commercial into the IMO process. It’s therefore our joint intention to pursue such a monitoring, including the routes and the cargos being shipped as role. Each of these risk elements has to be considered reporting and verification system in early 2013. At the same time, we will continue well as the sea states and other external factors. To separately and uncertainties associated with each risk the debate with stakeholders on which measure can successfully address the EU’s then move from a requirements specification to the category identified. greenhouse gas reduction objectives. system solution and integrate the various technologies effectively, a functional understanding of the system is Failure mode and effect analysis is frequently helpful The shipping industry itself is best placed to take the lead in delivering fast and needed. This principally separates the various functions in de-risking proposed conceptual designs, given that effective greenhouse gas emission reductions – thereby cutting cost and making the and shows the required essential flow of information it is executed competently. Failure in this context is sector fit for the future. The Commission is ready to play its part, in the EU and at between them. When complete, the intended function formally defined as an unplanned transition to a state in IMO level.” of the system can then be understood and used as a which the system either cannot perform at all or cannot framework for the ship design process, after which the properly perform its intended function: both being requirements for the various subsystems of the ship potentially dangerous. To consider a failure as a point can be defined from the functional model. To improve event which occurs at a well-defined instant of time is the understanding of the entire ship system, sensitivity frequently a serious oversimplification. Whenever there analyses can then be undertaken. is a steady degradation of performance together with an arbitrary criterion of failure, appreciable information When a departure is made from conventional modes of may be lost by studying only the time to failure. propulsion, increased attention should be paid to the However, for high-integrity systems actual failure may system reliability and, by implication, its availability. be so rare that it will not provide useful information. In Furthermore, it needs to be recognised that costs this context, Weibull lifetime modelling and Bayesian for design changes generally increase significantly statistical approaches can be helpful and from these a between each of the project stages. However, the design for reliability process can be defined. quality of data and with it increased certainty, during a design and production exercise tends to increase as the The conclusion of this process is that the solution project progresses. Therefore, in order to manage risk may appear to a ship owner to be what was originally throughout the life cycle it is necessary to identify risks, desired, but having been through a systems then quantify those risks and communicate them. engineering process ensures that it generally satisfies all stakeholder requirements. The range of risks associated with the development of novel forms of propulsion in merchant ships can be appreciated from Table A5.1.

82 Royal Academy of Engineering Future ship powering options 83 Appendices

Half Life Radioactive half life is defined as the time it takes stable, non-radioactive helium. If we originally for the amount of a radionuclide to fall to one half take 1 million atoms of tritium (3H), after 12.3 of its original value. Take for example tritium, years (half life) we would have 500,000 atoms of which has a radioactive half-life of 12.3 years radioactive tritium left, with the other 500,000 and emits a very low energy beta particle when it atoms having radioactively decayed to non- undergoes radioactive decay and transforms to radioactive helium (3He).

Appendix 6 fissionable material, does not imply that the fuel will heat and the cooling system needs high reliability. Further aspects relating to nuclear have a longer life in a reactor since other factors such as Furthermore, due to fission product activity, systems merchant ship propulsion corrosion resistance or fuel element fatigue influence and components containing fuel salt are highly life expectation. Therefore, it is likely that a standard radioactive and remote maintenance equipment is civil fuel of around 5% enrichment would be used in needed. This also applies to the off-gas and drain Fission process any merchant shipping application. Although not a tank systems. Additionally, the bare graphite used in Nuclear fission is induced when a free thermal neutron The simultaneous and progressive fission of a large CO2-producing energy source, nuclear power produces the core is susceptible to distortion and damage in is absorbed in a large atom such as 235U or 239Pu. number of atoms therefore creates a very large number waste products because following fission a number of a high neutron flux. Finally, the fuel in a molten salt Absorption of this type causes instability and can set of fission products which are highly radioactive isotopes radioactive products remain; many of which have long reactor is dispersed and this complicates the shielding up vibrations within the nucleus which cause it to of many varied and different elements, all of which, half-lives requiring a considerable period of storage requirements which are notably different to those of become distended to the point where it splits apart as soon as they are created, start to decay, giving before they cease to pose a radiological hazard. a PWR. The requirement to also thermally insulate the under mutual electrostatic repulsion of the parts. off energy and radiation in the form of beta particles hot compartments exacerbates the naval architect’s If this happens, the atom splits into fragments and (electrons) and gamma rays. The fragments go through Molten salt reactors problems. energy is released. In the case of 235U, if a free neutron several stages of decay before becoming more-or-less Molten salt reactors operate at atmospheric pressure is absorbed into an atom, the 235U is converted into stable elements. Quite soon after becoming critical and and in this way avoid accident sequences that with Ship concept design 236U which is highly unstable because of the neutron starting operation, the reactor core contains more than other types of reactor originate with low pressure. Nuclear propulsion, if applied to merchant ships, to proton ratio. Fissionable nuclei break-up occurs in 200 radioactive species (radionuclides). The molten salt reactor operates at high temperature would permit further concepts in ship design to be a number of different ways: indeed the235 U nucleus which, with appropriate generating plant, gives high contemplated. For example, because nuclear fuel may break up in some 40 or so different ways when Thus energy in the form of heat and radiation is thermal efficiency and high power to weight and size is relatively cheap, the conventional operating cost it absorbs a thermal neutron. Typically, this might be created not only by the fission chain reaction itself, but ratios. With regard to the high temperatures, there implications of high-speed operations do not apply. to split into two fragments, 140Xe and 94Sr as well as continues to be given off after the reactor is shut down is a large (≈500 ºC) margin between the operating It might, therefore, become desirable to operate a emitting two neutrons: alternatively, the split may take by the insertion of control rods which soak up neutrons temperature and the boiling point of the fuel salt, container ship at 35 knots or a tanker at 21 knots in the form of 147La and 87Br fragments plus two neutrons. and stop the chain reaction. The energy of decaying allowing time to react in the event of loss of decay contrast to the lower conventional speeds. Such a All of the fission fragments are initially radioactive and fission products is known as decay heat. heat cooling. It is inherently stable and load following, concept might save the deployment of one ship on the majority then undergo a decay process to stable with a quick response. a liner route when moving a fixed volume or weight daughter elements. For example, the 140Xe and 94Sr Fuel enrichment of cargo. Alternatively, it could give flexibility with a fragments are unstable when formed and, therefore, In PWR reactors only a small percentage of naturally There is an abundant world supply of thorium, which full complement of ships to accommodate predicted undergo beta decay. During this decay process the occurring uranium is fissionable,235 U, which implies is used in the reactor in its natural state, requiring no increasing trade volumes. A further design dimension, fragments emit an electron each after which they both that uranium has to be enriched in its 235U component. separation or pre-use processing. The earth’s crust due to the small mass and volume of fuel consumed, become stable. The emitted two or three neutrons While it is possible to achieve virtually any level of contains three times as much thorium as U238. may give scope for increased cargo deadweight which themselves, after having their speed and energy enrichment that is desired, uranium for use in civilian Moreover, the fuel salt can be contaminated so as capacity or, alternatively, provide greater flexibility in moderated, may be captured by other 235U nuclei in an programmes is generally around 5% of 235U. Levels of to confer virtually insurmountable resistance to hull design to satisfy other constraints which might not ongoing process called a chain reaction. Simultaneously enrichment of 20% or greater are subject to stringent proliferation and its use in nuclear weapons. normally be able to be relaxed. If the former of these with the formation of the emission fragments is the controls due to international safeguards and nuclear options were taken, the propeller power density might emission of gamma rays. weapons proliferation concerns and are only used After reprocessing, the wastes are predominantly become too large for an acceptable propulsion solution in specialist or military applications. Furthermore, an short-lived fission products with relatively short half- using a single screw. This might dictate that a twin or increase in enrichment level, because there is more lives. In a waste repository, safe radiation levels would triple screw option was selected and while increasing be reached in 300 years, as opposed to the tens of building costs, might have helpful steering or propulsion Decay heat thousands of years of actinides with much longer redundancy aspects. half-lives. Decay heat is the heat produced by the radioactive which will decrease to about 2% of the pre- As with many other aspects of the design process for decay of radioactive fission products after a shutdown power level within the first hour after Set against these advantages there are some a nuclear-propelled ship, the design of the control nuclear reactor has been shut down. The amount of shutdown and to 1% within the first day. Decay disadvantages of this technology. Pipes and system and the system integrity would form a central radioactive materials present in the reactor at the heat will then continue to decrease, but it will components comprising the salt systems must be feature of the safety case. Indeed, it would be a time of shutdown is dependent on the power levels decrease at a much slower rate. Decay heat will maintained above the high melting temperature of complex matter to construct a fully integrated safety at which the reactor operated and the amount of be significant weeks and even months after the the salt until emptied by draining to the drain tank. case for a ship-borne reactor plant and its supporting time spent at those power levels. Typically, the reactor is shut down, thus the need for ongoing Isolating the ship’s structure and other compartments shore infrastructure to support a nuclear powered amount of decay heat that will be present in the reactor cooling. Hence, nuclear powered ships , like from the high-temperature systems and compartments merchant ship. This is because a mobile reactor plant reactor immediately following shutdown will be nuclear power stations, require auxiliary generated is arguably the main problem facing the ship designer. needs to be able to operate independently at sea and roughly 7% of the power level that the reactor electrical power for reactor cooling or general ship Also, fuel salt drained from the reactor into the in at least two different dry-docks or ports: probably operated at prior to shutdown, services when the reactor is shut down. drain tank requires to be cooled to remove decay more if the ship undertook current commercial trading

84 Royal Academy of Engineering Future ship powering options 85 Appendices

patterns. However, to minimise complexity, duplication Nuclear safety considerations will drive different shore Operation: There would need to be some interaction used nuclear fuel they would be more demanding. of systems and cost, it would be important that the infrastructure requirements from those currently in with shore infrastructure whenever cargo is loaded or Again, these issues could be simplified if the designs of the reactor plant and shore infrastructure place for conventionally propelled merchant ships. unloaded and, more particularly, if the reactor had to advantages of a plant modular approach were adopted are coherent. In particular, a key objective for the mobile These would impact on factories, shipyards, ports be shut down for unplanned repair. The repair facilities with complex work undertaken off-ship or even offsite. reactor plant would be to minimise the nuclear safety and dockyards throughout the whole life cycle of employed would have to consider the use of high- demands placed on the shore infrastructure. the nuclear propulsion plant and, in so doing, would integrity power supplies, cooling water supplies to Decommissioning: The principle of designing reactor be a major cost driver for nuclear powered merchant remove decay heat, and the ability to handle low-level plant with decommissioning in mind should apply. Within the space available on a large merchant ship it shipping. There would be a number of life cycle radioactive discharges. The operation of nuclear- However, by the time marine plant decommissioning may be possible to include many of the support systems requirements that would need to be satisfied: powered merchant ships in ports close to centres of and disposal are likely to become issues for nuclear- that are required when a reactor is shut down for repair population will require appropriate nuclear emergency powered merchant ships, effective arrangements or refuelling. For example, alternative cooling water Design: A design assessment would be required to response plans and arrangements to be put in place for land-based nuclear plants may be in place. When systems for decay heat removal and high integrity justify the intended type of reactor plant to be used in which may, in certain quarters, have some negative these have been established they could absorb the electrical power supplies could be supplied. However, the ship. effects on public perception. Entry into navigationally relatively small contribution from the maritime domain, with a small number of shore facilities supporting a difficult port approaches would also require appropriate particularly if modular construction and deconstruction relatively large number of ships, it may be more cost- Manufacture: Special facilities would be required for assistance and emergency response arrangements. is employed. If repositories have not been established effective to install these facilities on the dockside. By the manufacture of reactor plant components, and in Indeed the operation of LPG carriers already addresses by then, the currently established plan of holding spent adopting a modular approach to nuclear plant design, the case of the reactor core these facilities would be similar issues. The use of offshore terminals might fuel in surface cooling ponds could be utilised. typical of small modular reactors, work on a complete need to be within a licensed site. The factories already form the basis of an appropriate goods distribution reactor plant module could be carried out at specialist in place for civil nuclear programmes could, however, solution but would add cost to the transportation chain. A number of dismantling options are available. The facilities offsite, thereby easing dockside nuclear safety most likely be used. Clearly, it would be desirable to use ports remote from immediate dismantling and safe storage options have requirements. Clearly, a system engineering approach the general public access and to design reactor plants been used, in part, for the Otto Hahn and Savannah is required to consider these and other issues, thereby Build and commissioning: Although aspects of to minimise dependence on shore facilities when shut respectively. Indeed, the Otto Hahn, following its ensuring an optimum design solution for both merchant conventional marine plant require clean conditions down for repairs. Additionally, within the operational successful period as a nuclear-propelled merchant ship and shore infrastructure. for assembly, the requirements for nuclear plant in framework there would be a need to introduce security ship demonstrator, went on to have a long career as a cleanliness, quality assurance, procedural control and measures to protect nuclear material on a mobile diesel-propelled cargo ship. Safety and life cycle issues inspection would be demanding. This implies fabricating platform. Radiation is a hazard to health, so the core of a nuclear as much of the reactor plant as possible in dedicated Cost models reactor, where the fission takes place, must be shielded manufacturing facilities offsite and then installing Refuelling and major maintenance and repair: Figure A6.1 shows the historical trend in uranium to prevent radiation reaching the operators and the completed modules: this again might favour integral Currently available reactor plants for merchant oxide prices, from which some volatility can be seen. general public. Furthermore, barriers must be provided reactor plant designs and small modular reactors. The ships would require refuelling at regular intervals. However, only around 52% of the cost of uranium fuel to ensure that highly radioactive particles stay within presence of nuclear fuel onsite requires facilities to be To minimise ship downtime, these periods might comprises the cost of uranium, to which enrichment the core. In a nuclear power station, the final barrier to designed to consider a range of external hazards, from be planned to coincide with routine dockings and and fabrication costs of approximately 26% and the escape of radioactive particles to the environment earthquake to aircraft impact. Furthermore, reactor major maintenance, inspection or repairs. The shore 7% respectively must be added: the balance of the is the containment building housing the nuclear plant. plant commissioning would require high-integrity infrastructure requirements would be similar to those total cost being conversion and waste processing electrical and cooling water supplies, facilities to for the build and commissioning phases, however, due and storage costs (Dundee 2007). Figure A6.2 records The escape of radioactive particles from the core handle radioactive discharges, and robust emergency to the increased radiological hazard associated with the historical trends in electricity productions costs constitutes a nuclear accident, which may be quite response arrangements. The latter requirements would small, easily contained and relatively harmless; or be simplified if the shipyard was distant from large large, as in the cases of Chernobyl and Fukushima. A centres of population. Within the shipyard, docks, tidal nuclear accident could result from core damage, such berths and cranes would also require safety cases, 140 Coal 12 as distortion or melting, as a result of failure of the and special arrangements would be needed to ensure • 120 Gas 10 systems which take away the heat from fission and the safe exit from the shipyard. Throughout the build • Nuclear 100 • 8 decay heat after shutdown. Hence the safety case for and commissioning a significant level of regulatory • Petroleum a nuclear power plant not only demonstrates that the oversight would be expected. 80 6 core can be taken critical; remain under control while 60 4 operating and safely shut down, but also demonstrates 40 2 that throughout the whole of the life of the core, 0

Uranium oxide price (USD/lb) 20

cooling systems will be available to take away both the 0

1997 1995 2001 1996 1999 1998 2007 2005 2002 2003 2006 2000 heat when it is operating and the decay when it is shut 2004 Jan 1 Jan 1 Jan 1 Jan 1 1995 2010 2005 down. 2000

Figure A6.1 Historical trends in uranium oxide prices Figure A6.2 US Electricity production costs 1995–mid 2008 [InfoMine.com] [NEI Global Energy Decisions]

86 Royal Academy of Engineering Future ship powering options 87 Appendices

from four fuel sources. Nuclear, along with coal, has a record of being the cheapest and also is subject to less Insurance Appendix 7 volatility in production costs that other fuel sources. The insurance of nuclear risks is subject to the same International atomic energy principles and Long-term users of nuclear fuels usually enter into principles as other insurance. However, the insurance requirements long-term contracts with producers at term prices and of nuclear risk is different from other insurance risks in recent years the term prices have shown significant because, however improbable, a reactivity excursion reductions against the spot prices. These contracts are or the failure to prevent overheating by removing The fundamental safety objective is to protect people 10. Protective actions to reduce existing or typically three to five years in duration and use a variety decay heat can result in core melting. This may result and the environment from harmful effects of ionising unregulated radiation risks of pricing mechanisms: fixed price contracts with in extensive plant damage and external radioactive radiation. Protective actions to reduce existing or unregulated escalation clauses linked to market indicators being but contamination if other barriers are breached. This radiation risks must be justified and optimised. one example. entrains a series of issues which can be summarised as Principles being: Requirements To achieve the fundamental safety objective there are In the marine context there are many variables involved ten principles [A7.1] which are required to be applied. The ten principles that are set out above in order to in the business and operational models underpinning • Events of potentially very high severity, but low achieve the fundamental safety objective lead, inter ship propulsion business cases. In the context of frequency. 1. Responsibility for safety alia, to the requirement for a safety assessment fuel prices as oil prices change, the cost of operating • A low number of nuclear risks having a premium in The prime responsibility for safety must rest with to be carried out. The following 24 requirements conventionally propelled vessels varies accordingly, 2010 of the order of $800M globally which is about the person or organisation responsible for facilities (A7.2), therefore, are directed towards the proper subject to the provisions of hedging arrangements, 0.04% of the total global premium. and activities that give rise to radiation risks. achievement of the safety assessment. whereas Figure A6.2 demonstrates that the electricity • There is insufficient actuarial data upon which to production cost of running a nuclear generation base an idea of the risk; there are only theoretical 2. Role of government 1. Graded approach plant has remained relatively stable over the last 12 calculations as the industry loss record is good. An effective legal and governmental framework for A graded approach shall be used in determining the to 13 years. Furthermore, the current term contract • The attendant risk of accumulation of financial safety, including an independent regulatory body, scope and level of detail of the safety assessment durations used in the land-based industries fit well with exposure. must be established and sustained. carried out in a particular state for any particular conventional marine survey and major maintenance 3. Leadership and management for safety facility or activity, consistent with the magnitude of cycles and from which similar fuel cost benefits might Effective leadership and management for safety the possible radiation risks arising from the facility or be derived. must be established and sustained in organisations activity. concerned with, and facilities and activities that give rise to, radiation risks. Overall requirements

4. Justification of facilities and activities 2. Scope of the safety assessment Facilities and activities that give rise to radiation A safety assessment shall be carried out for all risks must yield an overall benefit. applications of technology that give rise to radiation risks; that is, for all types of facilities and activities. 5. Optimisation of protection Protection must be optimised to provide the highest 3. Responsibility for the safety assessment level of safety that can be reasonably achieved. The responsibility for carrying out the safety assessment shall rest with the responsible 6. Limitation of risks to individuals legal person; that is, the person or organisation Measures for controlling radiation risks must ensure responsible for the facility or activity. that no individual bears an unacceptable risk of harm. 4. Purpose of the safety assessment The primary purpose of the safety assessment 7. Protection of present and future generations shall be to determine whether an adequate level of People and the environment, present and future, safety has been achieved for the facility or activity must be protected against radiation risks. and whether basic safety objectives and safety 8. Prevention of accidents criteria established by the designer, the operating All practical efforts must be made to prevent and organisation and the regulatory body, in compliance mitigate nuclear or radiation accidents. with the requirements for protection and safety as established in the International Basic Safety 9. Emergency preparedness and response Standards for Protection against Ionising Radiation Arrangements must be made for emergency and the Safety of Radiation Sources (A7.3), have preparedness and response for nuclear or radiation been fulfilled. incidents.

88 Royal Academy of Engineering Future ship powering options 89 Appendices

5. Preparation for the safety assessment Defence in depth and safety margins Management, use and Maintenance References for Appendix 7 The first stage of carrying out the safety of the Safety Assessment 13. Assessment of defence in depth 7.1 Fundamental Safety Principles: assessment shall be to ensure that the necessary It shall be determined in the assessment of defence 22. Use of the safety assessment Safety Fundamentals. IAEA Safety Standards Series resources, information, data, analytical tools as well in depth whether adequate provisions have been The processes by which the safety assessment No. SF-1, IAEA, Vienna, 2006. as safety criteria are identified and are available. made at each of the levels of defence in depth. is produced shall be planned, organised, applied, 7.2 Safety Assessment for Facilities and Activities. 6. Assessment of the possible radiation risks audited and reviewed. General Safety Requirements Part 4, No. GSR Part 4, The possible radiation risks associated with the Safety Analysis 23. Use of the safety assessment IAEA, Vienna, 2009. facility or activity shall be identified and assessed. 14. Scope of the safety analysis The results of the safety assessment shall be 7.3 International Basic Safety Standards for the 7. Assessment of safety functions The performance of a facility or activity in all used to specify the programme for maintenance, Protection against Ionizing Radiation and for the All safety functions associated with a facility or operational states and, as necessary, in the post- surveillance and inspection; to specify the Safety of Radiation Sources. activity shall be specified and assessed. operational phase shall be assessed in the safety procedures to be put in place for all operational IAEA Safety Series No115, IAEA, Vienna, 2006. analysis. activities significant to safety and for responding to 8. Assessment of site characteristics anticipated operational occurrences and accidents; An assessment of the site characteristics relating to 15. Deterministic and probabilistic approaches to specify the necessary competences for the the safety of the facility or activity shall be carried Both deterministic and probabilistic approaches staff involved in the facility or activity and to make out. shall be included in the safety analysis. decisions in an integrated, risk-informed approach. 9. Assessment of the provision for radiation 16. Criteria for judging safety protection Criteria for judging safety shall be defined for the 24. Maintenance of the safety assessment It shall be determined in the safety assessment for safety analysis. The safety assessment shall be periodically a facility or activity whether adequate measures are reviewed and updated. 17. Uncertainty and sensitivity analysis in place to protect people and the environment from Uncertainty and sensitivity analysis shall be harmful effects of ionising radiation. performed and taken into account in the results of 10. Assessment of engineering aspects the safety analysis and conclusions drawn from it. It shall be determined in the safety assessment 18. Use of computer codes whether a facility or activity uses, to the extent Any calculation method and computer codes used practicable, structures, systems and components of in the safety analysis shall undergo verification and robust and proven design. validation. 11. Assessment of human factors 19. Use of operating experience data Human interactions with the facility or activity Data on operational safety performance shall be shall be addressed in the safety assessment, and collected and assessed. it shall be determined whether the procedures and safety measures that are provided for all round Documentation operational activities, in particular those that are necessary for implementation of the operational 20. Documentation of the safety assessment limits and conditions, and those that are required The results and findings of the safety assessment in response to anticipated operational occurrences shall be documented. and accidents, ensure an adequate level of safety. Independent verification 12. Assessment of safety over the lifetime of a facility or activity 21. Independent verification The safety assessment shall cover all the stages in The operating organisation shall carry out an the lifetime of a facility or activity in which there are independent verification of the safety assessment possible radiation risks. before it is used by the operating organisation or submitted to the regulatory body.

90 Royal Academy of Engineering Future ship powering options 91 Appendices

Appendix 8 Appendix 9 The energy efficiency design index Calendar for main emission legislation events 2010–2020

The computation of the actual EEDI for a specific ship ship speed and capacity. It will also be seen that in both 1 July 2010 Tier II NOX limit for new engines [Global] design, for which the Index applies, is achieved through the numerator and denominator there are number 1 July 2011 US Caribbean Sea ECA adopted at IMO MEPC 62 the use of following relationship which embraces the correction factors included which adjust the value of (a) four CO2 potentially producing components in the the Index for particular circumstances. The actual EEDI 1 Jan 2012 Cap on sulphur content of fuel 4.50% to 3.50% [Global]

numerator while in the denominator is the product of is then given by: (b) 1 Aug 2012 North American ECA took effect SOX and NOX [Local]

(b) 1 Jan 2014 US Caribbean Sea ECA takes effect SOX and NOX [Local] Actual EEDI = 1 July 2015 ECA cap on sulphur content of fuel 1.00% to 0.10% [Local]

(c) M nME M nPTI nef f nef f 1 Jan 2016 Tier III NOX limit for new engines NOX ECA’s only [Local] f ( )+( )+(( f – f ) )–( f ) j ∑PME(i)CFME(i) SFCME(i) PAECFAE SFCAE* j ∑PPTI(i) ∑ ef f(i) PAEef f(i) CFAE SFCAE ∑ ef f(i) Pef f(i)CFME SFCME 1 Jan 2020(d) Cap on sulphur content of fuel 3.50% to 0.50% [Global] πj πj = l i= l = l i= l i= l i= l . . . fi CDWT .Vref fW

where: Notes

a SOX emissions are being controlled by reducing the percentage of sulphur in the fuel.

CDWT capacity is the ship’s capacity measured in nPTI is the number of power take-in systems. It is permissible to use fuel with a higher sulphur content than the local limit so long deadweight or gross tonnage at the summer is it can shown that by using some the SO content of the PAE is the ship’s auxiliary power requirements X load line. In the case of container ships this is under normal seagoing conditions. [kW] exhaust is no higher than if fuel was burnt that is within the local limit. taken as 70% of the deadweight. [tonnes]. b At Tier II until 1 Jan 2016 then Tier III. PEAeff is the auxiliary power reduction due to the use [MEPC 63/23 Annex 8]. of innovative technologies. [kW] c Subject to technical review to be concluded no later than 2013; this could be delayed. CFAE is the carbon factor for the auxiliary engine Peff is taken as 75% of the installed power for d Subject to feasibility review to be completed by 2018. fuel. [g /g ] CO2 fuel each innovative technology that contributes CFME is the carbon factor for the main engine fuel. to the ship’s propulsion. [kW]

[gCO2/gfuel] PME is the ship’s main engine installed power [kW] EEDI is the actual energy efficiency design index for PPTI is taken as 75% of the installed power for the ship. [g /tonne.nm] CO2 each power take-in system. For example, feff is a correction factor for the availability of propulsion shaft motors.[kW] innovative technologies. SFCAE is the specific fuel consumption for the f is a correction factor for the capacity of ships i auxiliary engines as given by the NOX with technical or regulatory limitations in certification. [g/kWh] capacity. SFCME is the specific fuel consumption for the main f is a correction factor for ships having specific j engines as given by the NOX certification. design features: for example, an ice breaker. [g/kWh] f is a correction factor for speed reduction due w Vref is the ship speed under ideal sea conditions to representative sea conditions. when the propeller is absorbing 75% of the M is the number of propulsion shafts possessed main propulsion engine(s) MCR when the ship by the ship. is sailing in deep water.

neff is the number of innovative technologies contained within the design.

nME is the number of main engines installed in the ship.

92 Royal Academy of Engineering Future ship powering options 93 Appendices

Appendix 10 Potential applicability of measures and options discussed

Ship type Tanker/Bulk carriers Container ships ro/Ro & ferries Cruise ships Ship type General cargo ships offshore support vessels Tugs Fishing vessels NB ES Op NB ES Op NB eS op NB ES op NB ES Op NB ES Op NB eS op NB ES op

Conventional propulsion options Conventional propulsion options

Diesel engines incl. modifications Diesel engines incl. modifications

Biofuels Biofuels

Natural gas (LNG) Natural gas (LNG)

Gas turbines Gas turbines

Other propulsion technology options Other propulsion technology options

Nuclear Nuclear

Batteries Batteries

Fuel cells Fuel cells

Renewable energy Renewable energy

Hydrogen Hydrogen

Anhydrous ammonia Anhydrous ammonia

Comp air/nitrogen Comp air/nitrogen

Hybrid propulsion Hybrid Propulsion

Further propulsion considerations Further propulsion considerations

Energy-saving devices Energy-saving devices

Hull optimisation and appendages Hull optimisation and appendages

Hull coatings Hull coatings

Hull cleaning Hull cleaning

Propeller redesign to suit Propeller redesign to suit operational profile operational profile

CRP propulsion CRP propulsion

Propeller cleaning Propeller cleaning

Superconducting electric motors Superconducting electric motors

Weather routing and voyage Weather routing and voyage planning planning

Slow steaming and/or propeller mod. Slow steaming and/or propeller mod.

Machinery condition monitoring Machinery condition monitoring

Crew training Crew training

NB New building NB New building ES Existing ship ES Existing ship Op Operational measure Op Operational measure

The above options do not take account of time frame in that some options would have a relatively long lead time; see Figure 5.1. The above options do not take account of time frame in that some options would have a relatively long lead time; see Figure 5.1. Additionally, the presence of a shaded block suggests there may be merit in considering these options for many cases of ships Additionally, the presence of a shaded block suggests there may be merit in considering these options for many cases of ships conforming to the general type. The absence of a shaded block does not necessarily imply there is no merit in the option for the conforming to the general type. The absence of a shaded block does not necessarily imply there is no merit in the option for the class of ship since many variants, including operational profiles, exists within ship types. class of ship since many variants, including operational profiles, exists within ship types.

94 Royal Academy of Engineering Future ship powering options 95 96 Royal Academy of Engineering Future ship powering options 97 As the UK’s national academy for engineering, we bring The Academy’s work programmes for 2011 to 2015 are together the most successful and talented engineers driven by four strategic challenges: from across the engineering sectors for a shared purpose: Drive faster and more balanced economic growth to advance and promote excellence in engineering. We provide analysis and policy support to promote the Foster better education and skills UK’s role as a great place from which to do business. Lead the profession We take a lead on engineering education and we invest in the UK’s world class research base to underpin Promote engineering at the heart of society innovation. We work to improve public awareness and understanding of engineering. We are a national Academy with a global outlook.

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