The electric warship VII - the reality

The electric warship VII - the reality

Commander GT Little, Royal Navy Eng(Hons), MSc, MCGI, psc(j), Royal Navy, Commander SS Young, MSc, CEng, MIMechE, Royal Navy, and Commander JM Newell, BSc, MSc, CEng, FIMarEST, Royal Navy

Integrated electric propulsion (IEP) is an everyday reality as the power system solution for naval platforms, embracing recent advances in enabling technologies to deliver cost- effective, survivable, power-dense solutions in a variety of applications. Founded on the Marine Engineering Development Strategy (MEDS) and supported by significant progress in the commercial marine sector, the defence community has embraced the potential of IEP and is now looking at more advanced integrated full electric propulsion (IFEP) solutions for future platforms. This paper follows on from the earlier series of ‘Hodge-Mattick’ electric warship papers and the ‘Newell-Young’ paper Beyond Electric Ship, and in doing so looks to put the United Kingdom Ministry of Defence’s (MoD) programmes and strategies into context, review the issues surrounding the introduction of IEP and provide an update on progress towards achieving the electric warship.

AUTHORS’ BIOGRAPHIES Commander John Newell, Royal Navy, joined the Royal Navy as Commander Graeme Little, Royal Navy, joined the Royal Navy an artificer apprentice in 1976 and joined BRNC Dartmouth on in 1984 as a marine engineer officer. On completion of his basic promotion in 1978. On completion of his degree at RNEC training in 1985 he joined Royal Naval Engineering College Manadon and initial training as a marine engineer he served as the (RNEC) Manadon to study for a first degree in marine engineering. Deputy Marine Engineer Officer in HMS Sirius. He subsequently Following successful professional training he joined HMS took a MSc in electrical marine engineering and served in the MoD Birmingham in 1990 as the Deputy Marine Engineer Officer. He as the project officer for pollution control equipment. He then subsequently read for an MSc in electrical marine engineering at served as the Marine Engineer Officer in HMS Boxer before RNEC Manadon followed in 1994 by an appointment to the Ship undertaking the French Staff Course in Paris. On return to the UK Support Agency as the project officer responsible for electric he spent 15 months with the Joint Planning Staff precursor to the propulsion systems. On promotion to Lieutenant Commander in Permanent Joint Headquarters (PJHQ) before becoming one of 1996 he joined HMS Sutherland as the Marine Engineer Officer. the appointers. He was promoted to Commander in 1997 and Following Staff Course, he was promoted to Commander in was appointed as the head of the Electrical Power Distribution 2000 and was appointed to the Warship Support Agency as the and Propulsion Systems specialist group within the Ship Support head of the Electrical Power and Propulsion Systems specialist Agency in March 1998. Commander Newell joined HMS Albion group where he is now serving. as Senior Naval Officer and Marine Engineer Officer in January 2001. Commander Stuart Young, Royal Navy, joined the Royal Navy in 1977 and completed undergraduate and post-graduate training at the Royal Naval Engineering College in Plymouth. He has INTRODUCTION undertaken a number of appointments at sea, including Marine n recent years a variety of papers, seminars and conferences Engineer Officer of HMS Norfolk, the Royal Navy’s first CODLAG have sought to provide detail and promote discussion on frigate. Shore appointments have included project officer for the the diverse range of issues that make up the electric warship procurement of Warship Machinery Operator and Maintainer concept. The same period has also seen a huge amount of Trainers, lecturer at the Royal Naval Engineering College and progressI in enabling technologies that have made integrated Marine Engineering Liaison Officer with the United States Navy, electric propulsion the system of choice for many new naval based in Washington DC. He is currently the Electric Ship ships. This paper looks to review the MoD’s Marine Engineering Programme Manager within the UK’s Defence Procurement Development Strategy (MEDS), examining its role within the Agency. framework of the Equipment Pillar of the Royal Naval Strategic

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Plan and the Smart Acquisition Initiative. Recent progress and Fig 3 looks to put the various system configurations into successes will be reviewed along with a look at the enabling context. technologies and the ‘road map’ for managing the successful introduction of such technologies. The aim of the paper is to THE MARINE ENGINEERING provide the wider naval marine community with clarity of the DEVELOPMENT STRATEGY MoD’s programme and to invite debate for marine systems of the The current strategy future. The first Marine Engineering Development Strategy was Perhaps by way of an overview it is worth reviewing the trends endorsed in 1996. It aimed to achieve significant life cycle cost in power and propulsion systems in recent years, noting that the reductions, whilst meeting naval requirements, by exploiting reality of electric propulsion was successfully introduced in 1920 world-wide industrial and commercial developments. Only if in HMS Adventure and has seen widespread use in the submarine naval requirements could not be met would development of community. specific equipment be funded. It envisaged achieving this through In the last decade of the 20th century, the Type 23 frigate the development and introduction of advanced-cycle gas tur- demonstrated the benefits that an electric architecture can bring bines within an integrated full electric propulsion architecture to bear with the hybrid power distribution and propulsion system and the electrification of auxiliaries. Development of industry known as Combined Diesel Electric and Gas (CODLAG). partnering and international co-operation opportunities was Building on the success of the Type 23 and the step change in encouraged. technology driven by the commercial sector, electric propulsion is Much has been achieved. Since 1996 every major ship the reality as we enter the 21st century, with two Auxiliary Oilers ordered for the Royal Navy has had an integrated electric (AO) and two Landing Platform Docks (LPD) shortly to enter propulsion system. The selection of IEP for the T45 means that service. Both classes have integrated electric propulsion and bring life cycle cost benefits will now be achieved earlier than envis- turnkey commercial solutions to satisfy a naval application. An aged in 1996. The electric ship technology demonstrator is artist’s impression of the LPD(R) is at Fig 1 together with an outline expected to start testing in spring 2002. This builds on the T45 schematic of the power generation and propulsion system at Fig 2. concept and introduces new power conversion systems and Hard on the heels will be the replacement survey vessels, advanced energy storage concepts to accrue further LCC ben- Type 45 destroyer and the Advanced Landing Ship Logistics, all efits with high system integrity, particularly under damage or embracing electric propulsion. The Type 45 solution is driven by fault conditions. the requirement for a power dense system with reduced whole The Marine Engineering Development Programme (MEDP) is life costs and challenging signature targets. The goal has been more than just electric ship, it covers all marine engineering met by exploiting the commercial market and incorporating the technologies where MoD-funded work is needed to ensure that United States’ integrated power system (IPS)-derived advanced new technologies meet the requirements of future ships. Work induction motor (AIM) development and the WR21 ICR gas either recently completed or currently on-going includes. turbine. ● Integrated waste management. ● Fire-fighting systems. WHY ELECTRIC PROPULSION AND ● Upper deck systems. WHAT IS IT? ● Improved roll-stabilisation. Electric propulsion brings together efficiency, flexibility, ● Composite pressure vessels. ● survivability and, perhaps most importantly, reductions in cost Non-thermal plasma for Nox/particulate removal for die- of ownership. Captured simply, reduced numbers of prime sel exhausts. movers, integrated systems, flexibility in layout and proven ● Fuel cross-flow micro-filtration. commercial precedent make it a credible solution to the require- ● Electrical actuation of hydrodynamic control surfaces. ment. Electric propulsion systems fall into three broad categories, The Equipment Pillar namely hybrid, integrated (IEP) and integrated full (IFEP). The The Marine Engineering Development Strategy does not terms electric ship and electric warship are also used. They can be exist in isolation and its pursuit over the next two to three years defined as follows: is a key element of the Equipment Pillar of the Royal Naval ● Hybrid - similar to the T23 frigate, where mechanical drive Strategic Plan. The Equipment Pillar outlines the Navy’s con- and electric drive systems are combined. cerns regarding reliability, manning levels and through-life ● IEP - where a common power source is utilised for both costs of current equipment and indicates how these could be ship services and propulsion system, with the propulsion improved by: being purely electric. T45, AO and LPD(R) are examples. ● Exploiting the concept of smart acquisition, closely align- ● IFEP - takes the IEP concept further by incorporating advanced power electronics and energy storage into the ing needs of through-life fighting power with specifiers architecture to give further cost and operational benefits. and designers of equipment, focusing on ease of opera- ● Electric ship - incorporates advanced prime movers and tion, maintenance, reliability and longevity, efficient man- widespread electrification of auxiliaries into the IFEP ning and operating costs. architecture. ● Seeking innovative ways of monitoring and employing ● Electric warship - where novel high-power weapons and trends in technology, especially encouraging potential for sensors are incorporated to take advantage of the high non-warfighting technology to improve conduct of rou- system powers available. tine business.

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THE DRIVERS FOR CHANGE teams within the UK’s Warship Support Agency) can advise on Technology the risks associated with attaining the required capability. Thus a Technical progress over the last five years has been far more dialogue needs to be established between all the relevant rapid than envisaged in 1996. The step change to integrated stakeholders. power architectures, with all the ensuing benefits, has now been taken. Future development will be more evolutionary rather than Environmental revolutionary, and the benefits will be obtained through equip- Royal Navy ships are required to operate world-wide and must ment, rather than system development. therefore comply with all applicable environmental legislation. Development of the first ICR gas turbine (the WR21) has Indeed, the long life-cycle of warships means that the design must been completed and the engine system selected as the primary anticipate future requirements. Commercial waste treatment power source in the T45. Propulsion motor technology has technologies may be applicable to the naval requirement but allowed a power-dense advanced induction motor to be selected would need to be made significantly more compact to facilitate for the T45. Many manufacturers around the world are now installation on a surface warship or submarine. Furthermore, developing permanent magnet motors of various topologies, warships are required to stay at sea for far longer periods and shore and major breakthroughs have recently been achieved in super- support facilities for disposal of waste stored onboard may not be conducting motor technology. Semiconductor development available. The goal of achieving a zero-emission warship, across continues unabated, as predicted, and further major advances the operational profile, remains. are expected over the next few years. In many areas, commercial The environmental impact of ships throughout their life cycle shipping has embraced future technologies earlier than navies; must also be assessed and minimised. This requires examination podded drives are an excellent example of an equipment now in of environmental impact during build, in-service maintenance widespread commercial use whilst still under assessment by the and on disposal. Within the automotive industry the manufactur- major navies. Fuel cell development, driven by automotive er’s responsibilities are clear cut and increasing. Similar trends can requirements, is progressing rapidly and to the extent that off- be expected in other fields, including marine. the-shelf solutions may be available within the foreseeable The future availability of fossil fuels must also be considered. future. The choice of fuel, and its production, transportation Fossil fuels are predicted to remain in significant use for 40 years and storage remains a major issue. or more. However, cost will increase through this time frame and As a result, further MoD-funded development — except to at some point it will become more cost-effective to use an address shock or signature issues and other specific naval issues alternative. The Royal Navy will be governed by commercial — is probably unnecessary but technology assessment in order to trends in this respect but needs to monitor trends closely and ascertain suitability is very important. This assessment is best initiate development to ensure that warships can operate within conducted through the medium of the proposed Ministry-led the wider future fuel economy. Marine Engineering Centre of Excellence, utilising the available expertise to make strategic decisions that have the full backing of Operational both MoD and industry. These achievements and a re-assessment The operational capabilities required from future warships of trends need to be reflected in any revised development strategy. continue to develop. Specific capabilities of future power and auxiliary systems will, of course, vary but there will be a number Smart Acquisition - The new environment of requirements that are generic. These include: Smart Acquisition was introduced within the Ministry of ● Increasing power density, to minimise impact on overall Defence in 1999 and adds clarity to the acquisition process which ship design. was not available to the original strategy in 1996. It refined the ● Extended range, requiring highly efficient power systems. concept of capability-led requirements and defined a new acqui- ● High availability. sition cycle, with clear decision points and therefore clear win- ● Low manning. dows in which technologies needed to be sufficiently mature in ● Increased stealth and improved signature control. order to be selected as candidate solutions. It defined incremental acquisition and technology insertion. More investment during A STRATEGY FOR THE 21ST CENTURY the early project stages is encouraged is order to reduce risk, and Taking these factors into account, the following strategy for close liaison with industry is regarded as essential. Although the marine engineering development in support of the Royal Navy’s original strategy anticipated many aspects of smart acquisition, future capability requirements is proposed: the revised strategy needs to stress further how marine engineer- ● Maintain awareness of technology and its capabilities by ing development fits into the smart acquisition framework. monitoring and assessing technology innovation and industrial capabilities and trends whilst maintaining the Risk Electric Ship Programme Office as a focal point for the Risk management is a key tool in the acquisition process. In monitoring of industrial and commercial technology trends the assessment phase the user’s requirements will be developed and utilising the Marine Engineering Centre of Excellence into the more detailed system requirements. At each stage the risk for the dissemination and assessment of applicable tech- associated with attaining the requirements will be assessed. The nologies. technology development and demonstration within the MEDP is ● Identify the warship acquisition risks which can be miti- a primary means of mitigating this risk. In addition the technology gated through marine engineering system solutions. specialists within the proposed Marine Engineering Centre of ● Develop mitigation strategies that satisfy the prime con- Excellence (primarily the Marine Equipment Integrated Projects tractor (or potential prime contractor), satisfy the DEC

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and Warship IPT and are within our ability to fund and ing considerations of signature, survivability and shock. The manage to completion within required time-scales. spectrum of hullforms is bounded by the larger carrier-based ● Build on success of original MEDS and the electric ship hullform (steel is cheap and air is free solution - although this concept, with emphasis on facilitation of incremental is not an entirely valid statement) and the exacting require- acquisition and technology insertion through the use of ments of a submarine platform. The middle ground occupied open systems. by the destroyer and frigate, whether multi- or monohull, ● Maintain focus on LCC reductions through equipment completes the picture. This is not the entire picture as IFEP is development within the IFEP architecture, technology also relevant to smaller vessels, but the requirements that set trends, including fuel cells, podded drives and smart the main contenders apart is installed power which is signifi- systems, and integration of high-power weapons and cantly greater than those anticipated for minor war vessels. The sensors. huge benefit of the IFEP solution is that premised on the ● Take into account external influences, including increas- currently-accepted range of hullforms possible for warships ing environmental legislation and trends in future fuels. driven by naval architecture and weapon and sensor solutions, ● Gain effective pull-through into service by ensuring that the IFEP concept can be designed to fit. This will not go sufficient de-risking is undertaken, results of de-risking are unchallenged as the required bounds of power density from available for those who need it (whilst protecting IPR) and both gravimetric and volumetric perspectives are placed under industrial capability to deliver solutions is maintained, considerable pressure and the demands for increases in both particularly through competition. are made. ● Maximise value-for-money through international Power system architecture. At the heart of the ‘power co-operation. station’ is the system architecture, on which the solution will hang; in the case of IFEP a number of options are still Thus the aim of the Marine Engineering Development Strategy presented as viable. The traditional architecture of a ring is: distribution with centralised switchboards and electrical To achieve the required capability whilst generating ongo- distribution centres (EDCs) offers, in most part, a good ing reductions in life-cycle costs, through the leveraging of baseline solution against which other ‘more novel’ solu- technology to mitigate the associated warship acquisition tions can be gauged. Novel approaches to EDC architectures risks. provide inherent flexibility and system redundancy with further enhancement possible using change-over switches THE ELECTRIC WARSHIP - EXPOSED and uninterruptible power supplies (UPS). Looking at a As discussed previously, the all-electric ship embodies the slightly more novel approach leads us to the much courted IFEP concept with the additional enablers of advanced-cycle gas ‘zonal concept’, whereby the distribution system, together turbines and wider electrification of auxiliaries. with all the supporting systems, is zoned with at least two It is however the IFEP architecture and possible solutions methods of supplying energy within a zone. Central to this which offer the most exciting possibilities; in terms of oper- architecture is a zonal power supply unit (ZPSU) and zonal ability, capability and reduced cost of ownership. The frame- energy storage unit (ZESU). Extremely attractive, the zonal work that is IFEP is founded on a number of enabling sub- concept infers increased survivability and operability but systems; high power generation, high power distribution, not without an element of technology and integration risk; energy storage and conversion, low power distribution, auto- a decision that will be informed by the MoD’s energy mation systems and propulsion systems. Within these base- storage philosophy. line sub-systems a bespoke architecture can be produced, an Energy storage. A wide range of technologies exist to support example of which is at Fig 4. a profusion of possible requirements; indeed it is this that The overall concept for the baseline architecture is one supports the need for a platform, if not pan-platform, energy of flexibility of design solution with a range of technologies storage philosophy. The requirements range from the equipment- able to meet the demands of the system. It is these tech- based UPS, commonly found in weapons and sensors, through nologies which have been the focus of MEDP and the sub-system requirements such as steering, to the most onerous marine engineering community and will form the basis of demands of propulsive ride-through, more of which later. Again, the next section. Before reviewing the technologies it is this issue is far from concluded and cannot be viewed in isolation, worth highlighting the importance of a generic baseline as together with architecture and the ZPSU/ZESU debate, this solution in the context of understanding and maximising needs a much broader focus. Assessment of technologies will be the synergy between various platform architectures; a key based on demonstration in the ESTD and the MoD’s energy theme in realising the potential of IFEP. Given a generic storage strategy. baseline allows system level design assessments to be made Operability. Often described as the panacea for the platform together with supporting a technology development focus. systems, IFEP and its variants, provides a huge step forward in It must, however, be remembered that at the system and flexibility of operation and system survivability, to name but two. sub-system level a number of themes need to be understood However, a note of caution - realising the full potential of the plant if the system is to be optimised effectively, these include: can only be achieved if it is fully understood and not, as some hullform; power system architecture; energy storage; oper- protagonists suggest, left to ‘come out in the wash’ as more is ability; user demands; and, field effects. understood and experience gained. Operability is a key strand and Hullform. The hullform solution drives the IFEP solution, must be understood at the earliest point in the design process. primarily from a power density perspective but with support- Central to the operability debate is the issue of single generator

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operation (SGO), a subject which has attracted a huge amount of power-dense, efficient and environmentally-sound solution to interest, notably from the operating community. The technical the problem of installed power. Coupled with conventional community has not helped themselves on this one as the term generator technologies, the high power generation capability, SGO conjures up all sorts of issues in the minds of the operators. vested currently in the WR21 GTA and the ACL GTA looks to However they have now been articulated clearly and it has been provide the surface platforms with the bulk of their power well demonstrated, with some clarity, that SGO does not result in into the late part of the 21st century. Technology focus for the reduced system availability when balanced against the ship han- future is reliant on established construction techniques with dling constraints, operational state and provision of energy stor- possible trends to super-conducting and permanent magnet age. The concept of minimum generator operation (MGO) em- technology. Before moving away from generation it is worthy braces SGO fully and is perhaps a far more relevant description of of note to raise the issue of fuel cells. The jury is still out and the operating procedures. the MoD focus has, at best, until recently been uncoordinated. User demands. As wider electrification becomes a reality the Whilst the short term possibilities are limited, advances in fuel demands on the power system increase, this is best illustrated as storage and cell technology will undoubtedly make fuel cells a we focus on the possible next generation of weapons and sensors, future attractive low power energy source. Industry is develop- or indeed those of aircraft launch and recovery. The user demands ing the fuel cell as a clean and efficient source of energy. Future need to be understood from the outset if the design solution is to work may concentrate on the use of alternative fuels (eg be flexible enough to accommodate technology insertion and, methanol or hydrogen) and its safe storage and handling in a indeed, the capacity to support demands from the outset. Not just shipboard environment. This work will be driven by the need confined to weapon systems and sensors, the implication of to identify an alternative to conventional fossil fuels by the increased electrification of auxiliary systems needs to be under- middle of the 21st century. stood and quantified. High power distribution, The ac/dc debate is still far Field effects. Subject to much recent focus for both in- from resolved, indeed which way we fall will primarily be service and newbuild projects, the effects of electromagnetic driven by the industrial focus and the level of risk. The ac/dc fields have been raised as an area of concern for hybrid and IEP subject is as emotive as ever and the decision point is fast installations, from signature and safety perspectives. Whilst approaching. Switchgear and cables cannot be readily di- the issue cannot be dismissed out of hand it equally must not vorced from this debate and will play a key role in the be made too much of, and a number of approaches are in hand solution. Switchgear rated for the perceived IFEP architectures to manage this effectively. From a safety perspective, measure- is on the limits of its capability and a number of options such ments are being taken on current classes and it is planned to as the hybrid switch and novel breakers are being assessed for carry out similar trials onboard LPD(R) and AO as they enter their applicability to marine systems. Related to this are the service. Any potential further problems can be reduced signifi- issues of switchboard design and a possible trend away from cantly by up front design and focus on shielding and installa- centralised to, perhaps, distributed switching and thereafter, tion. The issue of signatures is being assessed but cannot be perhaps, embedded protection - one step at a time possibly, discussed in this paper. but this is an area that we must progress as the exacting The generic baseline and system framework allows for a more protection and switching requirements increase. The last holistic approach to system and platform design, primarily from issue within this area is that of cables, and whilst we are a technology insertion perspective - an important point as the confident that the issues of EM fields, buildability and shock platform visions of the future begin to move into and out of focus! can be managed with existing technology, we need to look at Outwith these system design issues, it must be recognised that a how we might embrace busbars or more novel systems for the range of enabling technologies are central to IFEP, a number of future. At present all such systems are prohibitively expen- which, together with the review of risks are outlined in the next sive for the gains in ease of build and similar. section. Energy storage and conversion, Noting the profusion of possible solutions to meet the varied demands on energy storage, Framing the technology it is difficult to progress any one technology without having As mentioned previously, the key thread must be under- articulated the architecture and energy storage philosophy. In standing and managing the risk, both from equipment and general terms, the industrial base is making the enabling technol- platform perspectives. To articulate the technical risk requires ogy available, it is how we grasp this technology for the naval a formal risk review across the enabling technologies, the marine environment that presents the greatest challenge. Return- outcome of which will provide generic and platform-specific ing briefly to ESTD, flywheel technology and a regenerative fuel risk assessments across the technology, thereby framing the cell are being assessed for power system suitability at the zonal and technology issues and underpinning future development. Fig bulk levels of power. 5 captures the high-level technology enablers within which the Low power distribution, Not wishing to open the ac/dc analysis will be undertaken. debate or indeed repeat the high-power discussion, this section is Before reviewing the technologies it is worth reiterating the best left looked at from a system perspective. System issues are central themes for MEDS and AES; power density, risk, whole-life very much architecture-dependent and we must be aware of the costs, efficiency, environment and survivability. These criteria importance of the transversal issue with the high-power system. frame the focus on technology of power generation, high power Current solutions include transformed supplies but the technol- distribution, energy storage and distribution, and low power ogy is ‘here and now’ for bi-directional static power converters and distribution. perhaps presents a viable solution for platform incremental acqui- Power generation, Gas turbines are established as the sition.

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SWITCHGEAR - THE DC CHALLENGE - A by the propulsion motor (PM) system and the transmission/ FOCUS propulsor system. Comprising a drive and motor, power density Not a focus for previous electric warship papers, switchgear is and signature direct these technologies which have seen a huge however worthy of mention as a key enabling technology, particu- amount of industrial and government effort in recent years. The larly for a potential dc distribution system where the interruption advanced induction motor (AIM) is currently the preferred solu- of fault currents is more onerous than for comparable ac systems. tion, and is shown at Fig 7, but the industry pack of chasing The reason for this is simply that an ac circuit breaker can interrupt technologies is focused on taking PM system developments to at or around current zero whereas a dc breaker must create a meet the demands of pods, low displacement and novel hullform current zero either by forcing the current to zero by controlling the applications. Whether it will be a derivative of the AIM, a arc voltage or, creating a current zero by commutating the current permanent magnet machine or indeed a super-conducting ma- around an opening contact. In addition the dc circuit breaker chine, is a long way from being resolved, indeed the MoD is design is driven by the arc energy that can be dissipated, mindful actively pursuing a PM strategy to assess where best to focus its that a dc breaker will be much larger than its equivalent rated ac efforts and, perhaps more importantly, its money! Again industry counterpart, and the need to minimise the rise of fault current. is actively pursuing and solving the technical issues surrounding The technology solutions to these problems are high-speed air the novel PM technologies and this looks to be an area of circuit breakers and hybrid breakers. significant industry-led work in the near term. In support of this, Air circuit breakers. The mechanism during a fault is the power electronic devices and system developments continue control of the arc within the arc chute whereby an increased apace and a number of maturing PM system combinations now resistance of an established arc reduces the circuit current so that feature advanced pulsed width modulated (PWM) converters. the arc cannot be maintained by the circuit voltage and the current The three technology areas - conventional, permanent magnet is reduced to zero. The control of the arc is achieved by natural and superconducting - all offer high power density (volumetric electromagnetic and thermal forces assisted by a magnetic field; and gravimetric) efficient solutions. Whilst the technologies are technology which is well established. Currently available at up to all at varying stages of maturity, the key is that they would all seem 3kV, 8kA with a breaking capacity of 60kA, the move to voltages to have a role to play in the next generation of warships, albeit not in excess of 5.6kV for the electric warship application will need all technologies are suited to all applications. Fig 8 looks to development, but the more onerous rating is containable within provide a snapshot of motor technology to put each of the current technology. contender technologies into perspective. Hybrid circuit breakers. Combining a fast mechanical switch Of course Fig 8 is only half of the story, particularly the power and power electronics, hybrid circuit breakers utilise either zero densities, and the motor technologies cannot be compared in current or zero voltage switching, both of which are illustrated at isolation; any longer term assessment will need to include the Fig 6 and described below. converter and auxiliaries and this is the subject of the MoD’s Zero current switching. The mechanical switch carries the propulsion motor strategy. load current until a short circuit is detected whereby the switch Platform management systems (PMS). These have long opens, the power electronic switch is then triggered and a been the key to achieving manpower savings, and work is underway resonant current is established in the L-C network with a reverse on how to specify systems, in performance requirements terms, current flow at the mechanical switch. The voltage across the which support the operating and manning philosophies of the capacitor rises and the varistor begins to conduct, which dissi- future navy. This work will be further enhanced by developments pates the inductive energy within the circuit and the current drops in smart systems, which will be able to identify failures and to zero. damage, and reconfigure themselves automatically without op- Zero voltage switching. The mechanical and power electronic erator intervention. switches are triggered simultaneously but the time constants of the mechanical switch allows a parallel conducting path to be DELIVERING CAPABILITY established within the power electronics. As the mechanical Returning to the theme of strategy and how this and the switch opens, the arc voltage shifts the current flow fully to the technology can be embraced and engaged as platform system parallel power electronics path. The commutation provided by solutions, Fig 9 puts forward a roadmap for technology within the the power electronics then extinguishes the arc and with the framework of capability, requirement and timescales. These bounds electronic switch turned off with the mechanical switch open, the are extremely pertinent to the longer term focus of the electric remaining energy is dissipated within the varistor. warship concept and system design and technology integration Issues. The hybrid breakers provide improved current limit- for future platforms. The key thread throughout is risk and how ing overfast-acting air circuit breakers with a significant reduction, it is identified, owned and managed by the various stakeholders; almost elimination, of arcing. The hybrid variants are very similar notably the MoD, the prime contractors’ offices (PCOs), system but the trade-off is between the bulky resonant circuit required in integrators and equipment suppliers the balance of which needs the zero current switch compared to the need for switchgear to be developed if the capability is to be delivered. development. The technology has been implemented in proto- Mindful of the common thread of risk, the roadmap looks to type designs but no production arrangements have been taken capture the main themes and how the stakeholders need to be forward. In a marine application the constraints are the mechani- integrated and relevant to ensure that the obvious synergy is cal and power electronic switches, with current limiting only exploited. Within the bounds of the roadmap, here are a few achievable at the planned ratings if the mechanical opening force thoughts. Procurement of future platforms is now focused on and time to open are in the order of 35kN and 1.6 milliseconds1. delivering capability by the most cost-effective means, with the Propulsion systems. A huge subject area, broadly captured key themes being that of ‘requirements engineering’ and risk

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aversion - basically PCOs are tasked to deliver a capability to time the facility to be used for shore integration testing (SIT) for and cost, and they are not paid enough to embrace additional risk. Type 45 systems once the majority of ESTD testing has It is in the management of the dichotomy of risk aversion and the been completed. introduction of technology in which the MoD can be most One of the key issues for ESTD is how it will be utilised beyond effective with the combination of MEDP, partnerships with the current testing programme to manage technology insertion industry and collaboration. It is the MoD’s informed customer and incremental system design; this presents a unique opportu- status and ability to identify and mitigate risk that underpins nity for the wider naval power system stakeholders to be engaged much of the Smart Procurement Initiative - notably the balance of in this important programme. COTs, development of commercial solutions and bespoke naval development. How then against such a background can it be THE REALITY - AN INSIDE VIEW ensured that the work being undertaken within the MEDP This section will look at the all electric warship from the reality programme is not nugatory and that our future ships fully of a practitioner’s perspective with the emphasis on operating embrace IFEP? The answer is, in principle, easy to identify; in challenges related in the most part to LPD(R) experiences but practice it is much harder to implement. Fundamentally it is equally applicable to the wider concept. The single line diagram imperative that the risks are captured from technical, programme at Fig 2 should be used to support references to the LPD(R) and platform perspectives so that a coherent risk register is system. maintained - this functionality is vested with the Electric Ship There are several key features that will make electrical propul- Programme Office, thereafter the key is how to translate the risk sion a success or a failure in warships. We must of course adopt process into design, development and technology insertion. In a safe system of work but with many examples available from making this transition it is essential that PCOs and the wider industry, the merchant marine and of course the Royal Fleet industrial base are ‘onboard’. The drivers here, in addition to Auxiliary (RFA), this is a well-trodden path. More crucially we those of risk management, are the need to reduce cost of owner- must differentiate between an all electric ship and an all electric ship with effective support packages, the emphasis towards warship in that we take these latter platforms into operational commercial off the shelf equipments, and the trend away from theatres where we can expect some damage, even if minor, and we naval standards towards best practice, wherever that may be cannot afford to take away propulsion or electrical services from vested. The AO, LPD(R) and Type 45 have been provided as the command. This leads to a focus on operation, fire-fighting and almost turnkey solutions, thereby minimising risk and therefore damage control, equipment design, onboard organisation and cost. As system and equipment trends move away from the training, all of which are discussed below: commercial sector, the overriding issue must be ‘partnership’ and this is the area in which the MoD can bring a huge amount of Safe system of work and compartment access experience and knowledge to bear. A key focus for technology A safe system of work to include Health and Safety and other insertion and de-risking is the Electric Ship Technology Demon- statutory requirements is essential if the system is to be operated strator (ESTD). safely, noting the requirement to have established procedures for maintenance and operation by naval and civilian personnel. ELECTRIC SHIP TECHNOLOGY Wherever possible standard RN practice has been adopted but DEMONSTRATOR high voltage requires additional precautions including hazard The ESTD is a joint programme between the UK and France markings for compartments, hazard signage, restricted access which looks to de-risk IFEP technology so that it becomes an procedures and CCTV monitoring of all compartments desig- attractive option for future ship propulsion system prime contrac- nated HV. Routines are required both by contractors and visitors tors. The schematic of ESTD is at Fig 10. Broadly speaking it with restricted access regulations controlled by either a ‘day pass’ includes a half ship set of equipment with representative power or ‘contractors pass’. Contractors requiring access to HV com- generation and distribution systems linked by two static power partments will need to be briefed on the hazards and will require converters. The 20 MW propulsion motor drives a dynamic four- a limitation of access prior to unescorted access/work in these quadrant load, enabling the system to be demonstrated through- spaces. None of these issues is insurmountable but they need to out the complete operating envelope. The zonal distribution feature in the baseline design for an IFEP solution as the presence system, and inclusion of both zonal and bulk energy storage of HV will limit access and require control procedures. complete the picture. The supporting aims of ESTD are: ● To identify and de-risk IFEP system integration issues, System operation and manning of HV spaces including system stability, fault identification and protec- The HV system will be operated via the platform management tion and harmonic distortion levels. system (PMS). For the LPD(R) system, the normal practice will be ● To validate equipment and system software models to to run continuously in parallel, de-isolated with the minimum reduce or eliminate need for shore testing of future war number of generators required (minimum generator operation ship power/propulsion systems. (MGO) leading to single generator operation (SGO)) at State 3. At ● To generate ILS data. State 1, all generators may be required but the system will remain ● To assess signature issues. de-isolated. ● To inform future platform baseline designs and provide Because of the late change to electric propulsion during the supporting evidence for technology pull-through. design phase of the LPD contract, some HV equipment built to ● To support the development of power and propulsion IP23 is located in main machinery spaces. This means that the requirements for future warships. spaces concerned need to be disconnected from the live system ● Inclusion of some T45-specific equipment will also allow before any water-based extinguishers can be used to tackle a fire

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or before any attempt is made to control a flood. System discon- clear indication at the compartment entrance, and possibly on the nection procedures for the isolation of the HV system in the event equipment, as to whether high voltage equipment is still live. of fire/floods need careful consideration to ensure that the appro- Normal re-entry into any space requires the fire-fighting team priate action is taken without endangering personnel and maxim- to be protected behind a water wall. Whilst this may remain ising availability of the propulsion system to the command. sensible during peacetime operations, it probably is not if we wish Likewise, careful thought must be given when operating in SGO to protect the HV system from water ingress and maintain mode to ensure that a total electrical failure (TLF) does not occur propulsion to the command at State 1. if the affected compartment contains the only running prime Fig 11 summarises the range of fire and flood scenarios. mover. It is also possible to lose main motor excitation if isolations are carried out in the incorrect sequence. A series of hard-wired Equipment design trips allow rapid disconnection of the HV system. The selection of IP ratings for equipment must take into due The PMS system consists of a Pentium-based PC system consideration the siting and possible consequences of fire-fight- communicating via a dual redundant ethernet with battery- ing and flooding taking place in the immediate vicinity. We backed power supplies. This reversionary power source is located cannot afford to evacuate a space and abandon the prime movers in the forward switchboard and could perhaps be split into zoned or other equipment contained within. The number of systems power supplies to make the system more resilient to action adjacent to HV equipment should be minimised and, where damage in upgrades or future platforms. unavoidable, pipework should be continuous. CO2 injection Manning of machinery spaces at State 1 should not be unduly ports on HV equipment will not be fitted; rather compartment or affected by the possible hazards of exposure to HV (we have for a equipment fire suppression systems should be installed. long time manned magazines), but should be primarily driven by the operational gains of manning secondary or local machinery Onboard organisation and qualifications control positions as well as the ability to carry out immediate first The organisation to be employed for the ‘day to day’ opera- aid action. This approach must also be balanced against the tion/maintenance of the HV system is shown at Fig 12. availability of manpower and the increased risk of exposure to injury from action damage within a large machinery space. Hence Training HV compartments will not be manned at State 3 but will be at There is the requirement for the provision of a training/joining State 1. The mobile party (the cavalry!) needs to be best located video for the education of the ship’s company not involved in the to cover all main machinery spaces; particularly any unmanned at day-to-day working of HV equipment. This video may also have State 1. They need good communications and a high degree of to be made available to potential contractors to also make them individual protection. aware of the potential hazards. Training organisations such as FOST will be required to input proposed training scenarios and Fire-fighting and damage control also they will have to be informed of any limitations that HV may The recommended fire-fighting approach is to always place on proposed training (eg charged hoses, training smoke, maintain a continuous aggressive attack using appropriate etc). FOST currently use exercise smoke during operational sea first aid fire-fighting appliances. Should high voltage equip- training and this may have an impact on HV installations. ment within the compartment be correctly protected by correctly IP-rated enclosures, then AFFF and HPSW hoses High voltage policy may be used without restriction, although the inherent The preceding paragraphs highlight a number of themes for dangers of unprotected lower voltage systems must also be high voltage systems, all of which will be captured in the MLS1- taken into account. Should the compartment become unten- sponsored HV Policy Document. The document looks to provide able it should be evacuated and closed down prior to using the wider naval marine power system community with guidance the fixed suppression system. The process of closing down on the specification, design, installation, test and operation of HV and isolating the compartment should be initiated as early as power systems in warships together with the wider issues of reasonably possible with the available manpower. training and infrastructure. In the longer term it is hoped to How then to first aid fire-fight in HV compartments? The incorporate the policy guidelines within the requirements docu- suggested solution is to replace AFFF extinguishers and hose reels mentation for future platforms, notably on all safety-related issues

with portable CO2 and dry powder extinguishers to maintain the but in the near term the plan is to issue the document for ‘buy in’ aggressive attack without isolating equipment, although compart- from the wider naval power system community. ment isolation prior to initial attack on the fire could also be considered. Kill Cards will indicate HV compartments and also THE CHALLENGES compartments through which HV cables pass, and how to isolate Notwithstanding the specific technical issues mentioned, a power to these cables. There is however no need to isolate spaces number of other challenges also face the effective implementation

prior to CO2 drench although direct injection of CO2 onto HV of IFEP. Whilst not exhaustive, the Top ‘X’ challenges includes equipment is not supported. integration, electrical standards, equipment strategies, maintain- Electrical isolations for fire-fighting and the use of foam blankets ing innovation whilst minimising risk, embracing automation and will depend on the IP rating of high voltage equipment which system analysis. The following takes each of these issues in turn. should be a minimum of IP55 for a compartment below the Integration. The integration of the complex IFEP architecture waterline and/or with fluid systems running through it (low voltage is a significant challenge to system and equipment designers and systems must also be considered). The ability to isolate equipment an area which needs the requisite focus at all stages of the design from outside the compartment is essential and there should be a process. Integration issues include system stability, operability,

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compatibility - notably EMC, physical issues and system transver- the platform solution can meet the demands, primarily in terms sals. Experience has shown that the transversals issue is the most of power requirements and possible requirements for pulsed difficult to manage as boundaries are established between systems energy. Manning, support and similar strategies do, however, and sub-systems; the management of which needs system level exist but it is essential that coherency is maintained between co-ordination. On the theme of integration, the physical integra- them. tion and buildability of solutions is extremely important and must Automation. Central to the platform system solution, the be a significant focus during the design process. platform management system (PMS) and its derivatives provide Electrical standards. Existing power system standards are the operability and functionality of the system - the main concern not sufficiently robust to support IFEP and IEP architectures. however is that of integration. PMS needs to be embraced at the Fundamentally, standards reflect conventional systems and are outset and become an integral part of the design solution. Often not sufficiently flexible to be adapted to suit novel systems. In seen as the ‘cure all’ for system functionality and integration, it is support of this a review is being undertaken to propose a policy important that it is not left to pick up the design deficiencies from for IEP and IFEP systems covering issues as diverse as power the system and equipment integration. system standards, safety, Design constraints and working prac- System analysis. As the focus moves away from platform tices. This is even more relevant in view of the high voltage shore test facilities, a function of cost and time, the emphasis on implications. The MoD’s HV Policy Document will look to alternative mechanisms to assess system and equipment perform- provide the framework for naval marine power system standards. ance has come to the fore. The spectrum of activities in support Equipment strategies. Building on the themes of risk, the of the analysis is bounded by full scale test and simulation overarching MEDS and its implementation through the centre of balanced with prototyping and equipment tests. The trend to- marine engineering excellence, equipment and system strate- wards simulation is worthy of note, with both MoD and industry gies are essential to the electric warship aspirations. A number embracing it to balance equipment and system development. The of strategies are being written which look to draw together the strength of this approach is flexibility and cost, and the ability to requirements, platform risks, timescales and industry focus to model at component, equipment, sub-system and system levels. produce the supporting justification for equipment develop- Already naval marine power system modelling has produced a ment, the outcome of which will inform development and the modelling blockset to assess system and sub-system issues in a wider stakeholding community. Within DOpsE, a Directorate of ‘fuel to thrust’ approach, the outline schematic for which is at Fig the Warship Support Agency, system strategies are being pro- 13. The functionality of the models allows assessment of dynamic duced to support medium (10 year) and long (25 year) term performance, system transients, external impacts and bounds of visions, which look to provide a coherent focus across the operation. Validation of models remains a key theme along with marine engineering community embracing the MEDP and ele- the issue of models containing proprietary information, which ments of both the Corporate (CRP) and Applied (ARP) Research must be resolved if the goals are to be realised. The simulation Programmes. vision is to maintain a database of models for all power systems Innovation. Innovation will always be constrained by risk and equipment, with all new systems and equipment being and the desire to minimise any impact on the performance, delivered with a validated model - wishful thinking, perhaps, but cost and acquisition timescales of a future warship. However, essential if we are to realise the full potential of simulation. without innovation, technology will stagnate and the future Royal Navy will face increasing support costs and degrading SUMMARY performance and capability compared to other, more adven- The last year has seen a huge amount of activity in both the turous, navies. A balance must therefore be struck. This can be electric ship and electric warship arenas, notably with the reality achieved through establishing a thorough appreciation of of the electric warship and the coming of age of the integrated future technologies and their assessment, through the MEDP electric propulsion concept in the guise of LPD(R) and Type 45. and the expert eye of the Marine Engineering Centre of In support of these vessels and within the framework of smart Excellence. The risks associated with innovation can then be acquisition, the marine engineering development plan has sought fully quantified, and effective, focused risk-mitigation put in to maintain momentum and relevance with a number of notable place. As a result the likelihood of the pull-through of innova- successes, primarily that of ESTD. The emphasis is now, as ever, tive technologies into service by the warship prime contractor on cost-effective capability for the marine engineering solution and it is hoped that this paper has gone some way to demonstrate will be enhanced. how the MoD is looking to take this forward in partnership with Wider strategy. The marine engineering aspects are focused, industry with the focus very much towards incremental acquisi- but the lack of coherent strategies or, in some cases, coherency tion and technology insertion. between strategies in the wider naval service creates difficulties. Notably, the lack of a weapon engineering equivalent to MEDS REFERENCES remains a concern and it is imperative that the future require- 1.EA Technology Report 5435, HV DC Switchgear Feasibility ments of combat systems are identified as a priority to ensure that Study dated 3 Jul 01.

© Controller, Her Majesty’s Stationery Office, London 2001. © British Crown Copyright 2001/MoD. Published with the permission of the Controller of Her Britannic Majesty’s Stationery Office.

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Fig 1: The reality of the electric ship

Fig 3: The usual suspects

Fig 4: Baseline architecture or marker in the sand

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Fig 2: LPD(R); the single line diagram

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Fig 5: Framing the technology

Fig 6: The hybrid switch schematic

Fig 7: The advanced induction motor

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Fig 8: Motor development compared

Fig 9: A technology roadmap

Fig 10: ESTD schematic

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Fig 11: Fire and flood scenarios and responses

PERSONNEL TRAINING

Authorising Authority (FOSF ashore) HVA Authorising Engineer (MEO-May have nominated deputies) MCQ +AP+local assessment Authorised Persons AP+local assessment Competent Person (CP) Video + detailed briefing HV Aware (Remainder of ship's company) Video + briefing MEOOW1 As CP

Fig 12: Onboard organisation

Fig 13: IEP Model; the software realisation

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