A NEW CONTENDER FOR ENERGY STORAGE XX A NEW CONTENDER FOR ENERGY STORAGE Energy storage has long been a challenge for those in the renewable energy field – what happens to unused energy generated by solar or wind power for example? A new system of storing it as liquid air could provide answers. Dominic Joyeux discussed how the system works with Highview Power’s Dr Javier Cavada, CEO and President, and Gareth Brett, Chief Technology Officer, as well as Professor Yulong Ding, Director of the Birmingham Centre for Energy Storage. In years to come, 2018 may storage plant’, Ingenia 76). be seen as the year renewable The plant has a capacity of energy came of age. At the five megawatts and can store beginning of the year, UK 15 megawatt hours (MWh) of government data showed that, electricity, which is enough to for the first time, the 29% of power about 5,000 homes for electricity produced by wind and around three hours. solar was more than the total produced by nuclear (21%). The increase means that low carbon STORAGE energy sources now account CONTENDERS for over half of all electricity The main energy storage generated. providers are pumped However, a long-running hydroelectric – 95% of global challenge has been how to capacity – and lithium-ion store energy at times when batteries, which have been the there could be shortfalls caused fastest growing and account for by the wind not blowing or most of the rest of the world’s the sun not shining. UK energy energy storage. However, storage enterprise, Highview although pumped hydro has a Power, is going some way to long lifecycle of between 40 and solve this problem. In 2018, it 50 years and very large storage opened the world’s first grid- capacity, its main drawback scale cryogenic (liquid air) is geographical, requiring the energy storage plant in Bury correct topography and two The 15MWh cryogenic energy storage demonstration plant at Bury commissioned in 2018 © Highview Power (‘World’s first liquid air energy large reservoirs, the building of 30 INGENIA INGENIA ISSUE 78 MARCH 2019 31 A NEW CONTENDER FOR ENERGY STORAGE XX UTILISING THE CLAUDE CYCLE Invented in 1902, the Claude Cycle has enabled production of industrial quantities of liquid nitrogen, oxygen and argon. It developed and improved the Hampson-Linde cycle, patented seven years before, which had introduced regenerative cooling and enabled the low temperatures required to liquefy gases. The main drawback with the Linde method had been the loss of temperature at the end of the expansion process. Georges Claude developed a cycle that used a turbo-expander to expand gas to lower temperatures for more efficient cooling. A turbo-expander operates in the same way as a turbine, expanding high-pressure gas so that it becomes lower in pressure and temperature and power can be recovered. Turbo-expander is used when its primary purpose is to cool gas, while turbine is used when the purpose is to recover power. Highview Power’s system has adapted both the Claude and Linde cycles. Its charging process involves the compressing of air to ~12 bar, before it is cleaned and compressed further to about ~60 bar. The air is then fed into the top of the heat exchanger in the system’s ‘cold box’, where it is cooled to around -100°C. At this energy store where the liquid that gathers the compression point, some of the air is then bled off and expanded through a air is held in an insulated tank heat generated during air turbo-expander to cool it down further. at low pressure, and a power- liquefaction and is used for The remaining air that was not bled off continues through recovery unit where re-gasified increasing air temperature prior the heat exchanger. When it gets to about -180°C, it is expanded liquid air is used to drive a to expansion in the turbine. A process diagram showing the three stages of the producing, storing and recovering liquid air for generating power turbine and generate electricity. The second is a propriety cold © Highview Power through a Joules-Thompson (JT) valve. It is at saturation point after it has finished expanding and a large portion of it condenses into Ambient air is taken from the store that captures waste cold which can impact heavily on the responder when needed, Dearman and power researcher The company partnered with its liquid phase. The remainder is a very cold gas. surrounding environment then from the regasification of liquid environment. batteries have relatively short Toby Peters founded Highview Professor Yulong Ding, who The liquid and the gas enter a phase separator, which reduces using electricity it is cleaned, air while power is recovered In 2017, the potential of lifecycles (between five and ten and tested the concept at the in 2014 was appointed as the the pressure, along with the air from the turbo-expander. Here, dried and refrigerated through and later delivers the cold into lithium-ion batteries captured the years), they degrade and they University of Leeds. In 2011, Highview Power/Royal Academy the liquid drops out and is sent to tanks, while the gas returns a series of compression and the liquefier to reduce power headlines when Elon Musk made have a realistic economic limit of the engine part of the business of Engineering Research through the heat exchanger to the top of the system, cooling expansion stages until the air consumption – these measures a $50 million bet on Twitter that about four hours for harnessing subsequently branched off Chair in energy storage at the the incoming air along the way. Once it emerges from the heat liquefies – this process is based close the thermal loop for Tesla could build a 120 MWh large amounts of power. to form the Dearman Engine University of Birmingham to exchanger, a compressor recycles it and returns it to ~60 bar on a modified version of the cryogenic energy storage [see battery storage in South Australia Highview Power’s cryogenic Company and has since found further develop the cryogenic before it rejoins the input air and forms a semi-closed loop. Claude Cycle and can convert Cold storage technology and in under 100 days – if not, then storage solution ticks many applications with transport energy storage technology, Some of Highview’s patents cover the capturing of high- 700 litres of ambient air into one materials]. the company would charge boxes including sustainability, refrigeration units and other alongside other thermally based grade cold and recycling it into the liquefier, an important litre of liquid air [see Utilising the The separation of the nothing for its construction. cost, effectiveness and the fact cool-power projects. concepts). He had worked with step that doubles the efficiency of the liquefier and makes it Claude Cycle]. power, storage and recovery The state had been crippled by that it has a small footprint and In 2006, Gareth Brett, an Highview since 2005 and had economically viable. The liquefied air – air turns components provides flexibility power shortages and took him can be sited anywhere. The only electrical engineer with a seen the potential for energy to liquid when refrigerated to in the system’s design. up on his wager. Tesla delivered box it had not marked until now background in utilities and storage at very large scale. From a sufficiently low temperature Because power and energy are in 60 days and the result is the was usedemonstration at large banking, joined Highview and 2006 to 2007, Professor Ding (~-196°C at atmospheric independent of each other, largest battery storage facility scale. Now, with plans to begin fundraised for a pilot plant. worked with Highview to invent pressure) – is kept in insulated requirements can be tailored in the world, which supports building two large cryogenic In 2009 he became CEO. By and file patents for cryogenic tanks (acting as giant thermoses) so that clients can decide how and stabilises existing electricity energy storage plants in 2019, 2011, the world’s first liquid air energy storage and generation. at low pressure, which function much of a tank they want to fill, supplies in the state. that is set to be ticked too. pilot installation was installed Professor Ding’s work help as energy stores. When how much energy to store and However, although lithium- in Slough and connected to develop the world’s first research power is required, liquid air then how quickly it needs to be ion batteries seem to be the the grid with the help of a £1.1 centre for cryogenic energy is withdrawn from the tanks, emptied. This modularisation main contender for solving CLEAN COLD million grant from the then storage at the University of pumped to high pressure, of the process enables different the renewable energy storage BEGINNINGS Department for Energy and Birmingham. reheated and then expanded. configurations and solutions to conundrum, they do have Highview Power has created a Climate Change. The plant had The resulting high-pressure gas suit each customer. drawbacks. Lithium is relatively whole new industry – clean cold. a 350-kilowatt charge with two is then used to drive expansion rare and its supply is controlled, Co-founder Peter Dearman had and a half megawatt hours of HOW IT WORKS turbine generators to generate in effect, by a handful of mining an idea to build a reciprocating storage. Now the technical fine- The cryogenic energy storage electricity. No fuel is burnt in DEMONSTRATION companies. Cobalt, which is engine that was effectively tuning of the cryogenic storage system consists of three main the process, which results in the PLANT Diagram showing how Highview’s pilot plant uses the Claude Cycle.