KEEPING TRACK OF

The Highview cryogenic demonstrator plant in Slough

The Tube is a complex but well-bounded system. It can independently control and manage its energy needs. In the future, it will seek to source much more of its electricity from low-carbon energy generation.

cars sharing bogies, or pivoting on each train. The concept train amount of energy that is All of the energy used by the frameworks carrying the wheel is expected to deliver a 20% recovered and recycled through Underground arrives through the sets, which reduces train weight. reduction in train weight for each regenerative braking. The National Grid, but by choosing The bogies are also much more passenger compared with the traction power supply system which generating stations the flexible – which reduce frictional most recently delivered deep operates at a relatively low electricity is sourced from, it is losses between wheels and rails tunnel trains. voltage, in the range of 630 V possible to influence the level of as the train passes around curves. London Underground is also to 890 V direct current, which emissions. London Underground These trains will also have wide seeking tenders for the supply limits the distance over which is also exploring the possibility gangways linking cars, creating and field-trial of a prototype regenerated energy can usefully of partnerships that may allow the space for more passengers unit to further increase the be transmitted to 4 miles. By generating station owners to inverting the regenerated fund the installation of new, energy, to create alternating lower emission plant, on the ENERGY STORAGE current, and transforming it strength of long-term energy to a high voltage, it can usefully supply contracts. be transmitted much further. As it upgrades its stations, The trial unit is expected to trains and signalling systems, enter service in 2014 and Transport for London (TfL), is predicted to save 0.8 GWh which is responsible for London TECHNOLOGIES each year. Underground, will look to limit The Tube is a complex but both energy use and spending. well-bounded system. It can TfL’s objective is to create “A world Unlike most manufactured margin for breakdowns and independently control and class transport system for a world Energy storage already plays an important goods and commodities, maintenance. One consequence manage its energy needs. In class city”. By using innovative role in balancing supply and demand energy, especially electricity, of having significant amounts of the future, it will seek to source engineering it aims to deliver a is not easily stored after it has intermittent much more of its electricity from transit network that remains fit across the electricity grid. With an increase been generated. The ‘stores’ of is that power stations would run low-carbon energy generation. for the 21st century. in intermittent generation, the flexibility primary energy have traditionally at capacities lower than they provided by using new forms of stored been reserves of oil, gas, currently operate at. and fissile material, with most Governments and public energy has the potential to both reduce the energy systems holding a bodies are now actively relatively small amount of considering energy storage BIOGRAPHY costs and improve the security of the overall hydroelectric power behind as a way of providing greater Kevin Payne joined the former British Rail as a trainee in 1976 system. Dr Jonathan Radcliffe looks at some dams. The result is that power flexibility for systems that London Underground is introducing air-conditioned trains on the shallower and has worked on urban and suburban rail schemes across sub-surface lines. By 2016, 40% of the Tube network will use the S-Stock Tube suppliers have usually installed will have new forms of trains, which have saloon air conditioning. These trains have the first walk- the UK. He is a Chartered Electrical Engineer and holds an MSc of the technologies being considered that generating capacity to meet generation and changing through gangway carriages on the Underground. The inside of the train is one in Engineering Safety Management. continuous length, providing improved capacity, security and passenger flow could enable future energy storage systems , with a safety patterns of demand.

26 INGENIA INGENIA ISSUE 54 MARCH 2013 27 ENERGY STORAGE SYSTEMS SOCIETY

To recover the stored energy, compressed air is discharged into a gas-fired combustion turbine. Plants in Germany and the US have already achieved outputs of up to 400 MW over 10 hours.

STORAGE STRATEGIES and opportunities could MECHANICAL store up to 14 GWh. The main it is expanded to drive the type, with vanadium dissolved Lead-acid batteries, perhaps as part of a carbon-capture provide this flexibility. These constraint to this method is the turbine, thus requiring little or in dilute sulphuric acid and the oldest commercial battery plant, allows energy to be In the UK, the government energy storage technologies The most obvious ‘mechanical’ mountainous terrain needed to no fossil fuel. Both methods, held with different valence in technology, continue to be stored, transported and used forecasts that, by 2020, the can be characterised by the technology is the pumped make it work. storing compressed air and heat, tanks. Zinc-bromine batteries developed with new materials. through multiple pathways. country will have installed (in kW or MW) output storage used in hydroelectric Compressed-air energy can give efficiencies of over 70%, have also been commercialised. As a mature technology with Though the process may turbines that can generate over a period of time (normally schemes. Pumped hydro storage (CAES), created but the need for geologically Scaling up energy storage is a relative low cost, lead-acid be relatively inefficient, as a 31 GW of electricity (18 GW hours, h) to give the total accounts for 99% of current by pumping air into a suitable underground reservoirs case of changing the size of the batteries are an option where proven technology that can offshore, 13 GW onshore). amount of energy (in kWh or energy storage with around reservoir, conventionally uses limits this technology. tank. Individual units can be space is less limited. They are decarbonise difficult sectors, it Recent signs suggest that MWh) that the store can deliver. 130 GW worldwide. This underground caverns, though Another mechanical scaled up to 6 MWh, delivered being tested on grid applications could be valuable. ministers are also keen to Energy is normally approach uses ‘off-peak’ vessels above ground can also approach to capturing over two to eight hours, with up to 20 MW. One advantage of a accelerate the take-up of converted from one form to electricity to pump water from store energy. To recover the off-peak energy is to spin long lifetimes and efficiency ‘hydrogen economy’ is that it photovoltaic solar cells and to another so that it can be stored, one reservoir to a higher one stored energy, compressed air flywheels that can store kinetic around 70%. could deliver a portable fuel have 7 to 20 GW of capacity then converted again after where it has greater potential is discharged into a gas-fired energy. Flywheels can be very One of the most widely CHEMICAL to replace hydrocarbons in installed by 2020. This means storage. For example, electricity energy. The dam releases water combustion turbine. Plants responsive, delivering large used commercial storage Chemical storage, apart from transport. Another option is that, with a total expected can produce hydrogen and to spin turbines and generate in Germany and the US have amounts of power over short technologies is the sodium- batteries, has also been brought to feed hydrogen created from installed generating capacity of store energy chemically, or it electricity as needed. Such already achieved outputs of up timescales to provide frequency sulphur battery, with 300 MW into the quest for ways of renewable electricity sources 110 GW, a significant proportion can pump water uphill into schemes recover around 70% to 400 MW over 10 hours. regulation. New materials and deployed globally. Sodium- stashing off-peak power for into the gas grid to decarbonise of our electricity will come from a reservoir, storing ‘potential’ of the energy put in. A typical Alternative approaches to magnetic levitation for bearings sulphur batteries are high- later use. Hydrogen production heating. The gas grid is itself a intermittent sources. energy. Reversing the process pumped-hydro installation has CAES also store energy from allow flywheels to store more temperature electrochemical from electrolysis of water using large and effective store, three The Department of Energy can then generate electricity. a power output from 250 MW the heat produced when a energy by spinning faster, up to devices with molten sodium and off-peak or surplus power, times the size of the power grid and Climate Change (DECC) These conversion processes to 1.5 GW, discharging its stored gas is compressed. The heat around 20,000 rpm, and have molten sulphur as electrodes. or from gasification of coal in energy terms. explained in its 2012 report UK are not perfect: a system will energy over a period of up to is held in a thermal store and lower losses, with 93% efficiency These can achieve 80% Renewable Energy Roadmap always give back less energy 10 hours, with the ability to reintroduced into the gas when in energy recovery and 20-year efficiency, with 15-year lifetimes. Update how greater use of than was used to store it, with lifetimes. Combining individual Lithium-ion (Li-ion) batteries energy storage could help the ratio being measured as units can provide up 20 MW over are a standard technology for in the takeup of renewable its ‘efficiency’. The percentage DAM 30 minutes. portable consumer devices and energy, such as wind power efficiency can be important for UPPER RESERVOIR some electric vehicles. They and solar photovoltaic (PV) reconciling the value of storage Cable and are made up of electrochemical vent shaft power, saying “Innovation in against its costs. ELECTROCHEMICAL cells, usually with lithium cobalt Electrochemical energy storage, cost-effective storage solutions We can categorise the Pumping oxide as a positive electrode and grid management could technologies used to store in the shape of the ubiquitous and carbon for the negative Surge help bring about a step-change energy, and the conversion Access chamber battery, is perhaps the most electrode. Li-ion batteries in affordability and long-term processes involved, broadly as tunnel familiar way of holding energy Generating are light, with a number of potential for solar PV in the UK in mechanical, electrochemical, in reserve. Batteries are rapidly features that can alter power/ this context.” chemical, thermal and becoming part of the armoury energy characteristics. They The electricity network must electromagnetic. Each LOWER Machine of large-scale energy storage, RESERVOIR can have 90% efficiency and a match – or ‘balance’ – supply discipline has its advocates, with Hall with a number of competing Tailrace tunnel good charging cycle life. Some and demand on a real-time researchers pursuing different technologies. Cruachan on came online in 1967 and was the first- electricity distribution networks basis. Balancing a network with approaches. Considering ever reversible pump storage hydro system to be built. It can generate 885 Redox flow batteries work by are testing Li-ion batteries, with more intermittent generation the power, energy, efficiency GWh of electricity a year and has a machine hall built within reversible reduction-oxidation, mountain. Water is pumped uphill to a high reservoir when the demand, and Scottish & Southern Energy demands the greater flexibility and physical characteristics price, for electricity is low. During hours of peak demand, when the price of using electrolytes stored as (SSE) testing a 25 kW device BYD and the State Grid Corporation of China have built the largest grid in other parts of the system that of a technology helps us to electricity is high, the stored water is released through turbines to produce liquids in two separate tanks. battery storage facility in the world. Located in Zhangbei, Hebei Province, . Unlike most other types of power station, hydroelectric power that can store 25 kWh, and UK China, the LiFePO4 battery combines 140 MW of renewable energy generation energy storage can bring. A understand how it could play a plants can be brought online almost immediately, making them suitable for The vanadium redox battery Power Networks (UKPN) one at (both wind and solar), 36 MWh of energy storage and a smart power number of technology options role in the energy system. dealing instantly with relatively large fluctuations in grid demand (VRB) is the most advanced 200 kW/200 kWh. transmission system

28 INGENIA INGENIA ISSUE 54 MARCH 2013 29 ENERGY STORAGE SYSTEMS SOCIETY

Given that heating buildings accounts for 42% of nontransport energy demand in the UK, storing heat and using it directly to provide thermal comfort in our homes is one serious option being widely considered.

times when demand is high. discuss whether liquid air could Given that heating buildings The 2012 report for the Carbon +– The principles behind using provide a credible alternative to accounts for 42% of non- Trust, Strategic Assessment of THERMAL STORAGE LT/HT Superconducting Magnet liquid air for energy storage existing fuel systems. transport energy demand in the Role and Value of Energy One way to store ‘peak energy’ for later use when demand is are straightforward: electricity At the opposite end of the the UK, storing heat and using Storage Systems in the UK Low high is to liquefy air. Highview Power Storage has developed such storage technology in the UK, building on research at the Liquid powers an air liquefaction spectrum, energy is stored as it directly to provide thermal Carbon Energy Future, found Helium/ plant with the resulting liquid, heat for a range of applications. comfort in our homes is one that with a high proportion of University of Leeds. With £1.1 million from the Department Cryogenic Helium/ for Energy and Climate Change, the company has built a Nitrogen Refrigerator Refrigerator predominantly nitrogen at Concentrated can serious option being widely renewables in the energy mix, -196 °C, stored in an insulated focus sunlight using parabolic considered. Heat can be stored storage could be more valuable 300 kW/2.5 MWh pilot plant in Slough, in partnership with container. When power mirrors to heat molten salt by raising the temperature of than previously suggested. Scottish & Southern Energy and the industrial gas company BOC. Pump is required, the liquid is during the day. The molten water, but a hot water cylinder The report explains that this is The efficiency of the system in the basic setup is relatively Cryostat re-gasified at high pressure to salt is then stored in a insulated holds just a fraction of the heat because its analysis “includes low, though Highview uses the cold exhaust gas at vaporisation drive a turbine and generate container, from which its heat a house would need to stay savings in generation capacity, to precool air for liquefaction, giving an efficiency of 50%. The A superconducting magnetic energy system (SMES) stores energy in the process can, however, benefit greatly from utilisation of magnetic field of a superconducting coil, which needs to be kept at low electricity. can be extracted at night to boil warm. Alternative thermal interconnection, transmission temperature Interest in this technology water and drive a steam turbine. storage technologies are in and distribution networks and low-grade heat at gasification, which will return 70% of the has been growing. The Royal Electricity can also be generated testing which have a higher savings in operating cost”. input electricity. Academy of Engineering and the from heat stores using heat energy density than water. In January 2013, the Rt Hon www.highview-power.com ELECTROMAGNETIC Capacitors store energy in the Centre for Low Carbon Futures pumps and heat engines – see For example, ‘phase change’ David Willetts MP, Minister of electric field between two are organising a conference to Thermal process. materials, such as paraffin, can State for Universities and Science, There are also ways of charged plates. Electrolytic store or release heat as they picked out energy storage as storing electricity itself, in double layer capacitors change from solid to liquid, one of eight “great technologies” superconducting systems, (EDLC), or supercapacitors, holding several times the for the UK, putting forward for example, or in capacitors. have porous electrodes with a amount of energy compared to £30 million “to create dedicated Their characteristics make liquid electrolyte, blurring the the same volume of water. R&D facilities to develop and them valuable for maintaining distinction between conventional test new grid-scale storage electricity supplies within capacitors and electrochemical technologies, helping the UK transmission standards. batteries. EDLCs have high power RECENT capitalise on its considerable Superconducting magnetic but low energy densities, with low DEVELOPMENTS excess energy production, saving energy storage (SMES) systems response times and good cycling There is now a large range of money and reducing the national circulate a current round a characteristics. They can be used storage technologies available carbon footprint”. superconducting circuit. For in conjunction with batteries as or in development. As well For its part, the Department the material to remain a part of hybrid storage systems for as further improving the of Energy and Climate Change is superconductor, it has to be kept electric vehicles. performance levels of each funding innovation around heat at very low temperatures with approach, there needs to be a and electricity storage, including liquefied gases, usually helium, THERMAL broader, whole energy systems, £17 million for a demonstration at a temperature of -269 °C, or, view. With this in mind, it helps plant to address grid-scale in the case of so-called high- Just as heat is an intermediary to think about the service storage and balancing needs temperature superconductors, in most conventional that the energy provides. For in the UK electricity network. with liquid nitrogen at -196 °C. approaches to electricity example, for buildings we would Research Councils UK also see Superconducting storage generation, it can also play In the UK, ITM Power has developed a 360 KW system with AEG using proton need thermal comfort, so rather energy storage as a priority exchange membrane electrolysis, in a shipping container-sized unit. The systems can deliver a high a role in energy storage. For picture shows six electrolyser units on the left-hand side, with the power than storing electricity to run a for funding, with two large power output, within a second, example, liquefied air can electronics on the right. The technology can be scaled-up with MW-sized heat pump, a solution might be projects underway to investigate models combined to provide multi-MW systems © www.itm-power.com for short periods. hold energy in reserve for to store heat. new technologies and how

30 INGENIA INGENIA ISSUE 54 MARCH 2013 31 We run one of the largest engineering ENERGY STORAGE SYSTEMS apprenticeship schemes in the UK helping people WE ARE TRAINING develop a range of skills from sheet metalworking to design engineering. As part of their three-year course, our apprentices also get to work on some MORE THAN 1,000 of the country’s most exciting engineering projects like the Astute submarine programme and the Typhoon combat aircraft. It’s this dedication that APPRENTICES led OFSTED to award us a Grade 1 for our apprentice training programme. AT ANY ONE TIME.

The UK is now in transition between an era THERMAL PROCESS where energy supply and demand have In a new approach to thermal storage, a small UK company, Isentropic, has been developing a process for storing electrical been predictable and easily managed, and energy across a thermal differential. In June 2012, the Energy Technologies Institute, a public-private partnership between a period in which they will need more active global companies and the UK government, invested £14 million management. in Isentropic. A £15.7 million project will build a 1.5 MW/6 MWh device on Western Power Distribution’s network in the Midlands. The process consists of a highly reversible heat pump/heat engine resting between insulated containers of crushed and graded mineral. On charging, argon is compressed, raising the temperature to 500 °C. After compression, this is passed slowly through the first container, heating the mineral to the gas temperature and cooling the gas to close to ambient. The gas is then passed through an expander where it is returned to its original pressure which drops they could be used in future Energy storage offers significant the temperature to -160 °C. It is then passed through the second energy networks. However, export opportunities. The container which cools the mineral within to -160 °C and warms the this is a global challenge and potential global market for gas back to near ambient temperature. The compressor is very there will be a need to engage energy storage could be much larger than the expander and work done in compression internationally. hundreds of billions of dollars. dominates the charge cycle and mechanical work (for example from Energy storage could even There is already a growing an electric motor) is thus converted into a temperature split between be a factor in the international market for storage, and even the two containers trade of energy. Opportunities if its size relative to generation As the charge proceeds, thermal fronts traverse the two mineral for development of pumped capacity were merely kept at heat stores until the end of each store is reached and the system hydro storage may be limited historic levels. is fully charged. Discharge is the reverse of the charge process in in the UK, but Norway could The UK is now in transition that compressor and expander swap functions with the work of the provide balancing power to its between an era where energy expander now being dominant and the gas flow direction being near neighbours. The largest, supply and demand have been reversed. The overall process operates with an efficiency of 75%. hydroelectric reservoir in Norway, predictable and easily managed, Isentropic is currently completing the design work for a scaled, Lake Blåsjø, stores 7.8 TWh, and a period in which they will 150 kW system as a design validation tool for the 1.5 MW network almost 1,000 times that of the need more active management. installation - see www.isentropic.co.uk UK’s largest pumped storage The technology options have to scheme at Dinorwig in Wales. be there, but so does the policy Synchronous Coupled with offshore wind, and regulation framework to Motor/Generator Argon gas and the existing transnational encourage investment. The UK collaboration to build a North is in a good position to move Sea grid, which includes the UK quickly in this field, but this will and most of the countries around depend on policy decisions Electricity in/out the North Sea, this option could based on a long-term and reduce the overall system costs of whole-systems view of our deploying renewables. energy infrastructure. Hot Store 12 bar +500 deg C

BIOGRAPHY Dr Jonathan Radcliffe was Head of the Analysis Team for the Energy Research Partnership, before taking up a position to Cold Store lead a new energy storage centre with the Centre for Low 1 bar -160 deg C Storage Engine Carbon Futures at the University of Birmingham in March 2013.

32 INGENIA REAL PRIDE. REAL ADVANTAGE.