In the fifteen years since Peter Dearman first sprang his ‘garden shed’ invention on the world, its significance is growing out of all recognition. What started life as a clever way to displace fossil fuels in piston engines has spawned not only an emerging suite of zero-emission technologies that have the potential to solve several stubborn energy problems, but also an entirely new way of thinking about cooling. Liquid air is now being recognised as a powerful new energy vector that could unlock a circular ‘cold economy’, and has secured more than £100 million in funding from government, universities, industry, private investors and the EU (see footnote for further details of academic programmes).
The new system level approach has exposed cooling as a hidden link between many of this century’s biggest environmental and social challenges, and it is now becoming clear that clean cold technologies powered by liquid air could help achieve no fewer than 14 of the UN’s 17 Sustainable Development Goals. With two important UK liquid air technologies launching commercial demonstration projects this month, out of Peter’s shed we may be nearing a radical transformation of the energy system.
Peter invented his Dearman engine when he was searching for something clean to replace fossil fuels in vehicle engines and happened upon liquid nitrogen. Liquid nitrogen has a boiling point of -196C, and exposure to heat or even ambient temperatures leads to a 700-fold expansion in volume, which can be used to drive a piston. As we started to develop the engine with a team at Leeds University, it soon became clear that (i) given cryogenic liquids, like liquid nitrogen or liquid air, could also be efficiently expanded through a multi-stage turbine to drive an electricity generator, and (ii) since nitrogen is liquefied in industrial scale plants powered by electricity, the two processes could be combined to form a grid-scale energy storage device, to warehouse off-peak nuclear and wind power and displace carbon intensive generators at peak times.
At Highview, we built and tested a small scale but grid-connected Liquid Air Energy Storage (LAES) plant in Slough (now hosted at University of Birmingham) and secured £9M of grant funding to build a larger 5MW commercial demonstrator in Manchester, which starts operating this month. LAES plants could be built on a similar scale to smaller-scale pumped hydro but without the need for mountains and lakes, integrating existing equipment already widely used in the industrial gas and power generation industries and costing far less than batteries. As rapidly rising UK renewable generating capacity starts to produce periods of negative wholesale power prices increasingly often, liquid air offers a cost-competitive way of storing and making use of ‘wrong time energy’, so helping to integrate far higher levels of renewable penetration.
Liquid air not only expands when it boils, but also gives off large amounts of cold as it returns from -196 to ambient. In LAES plants, the waste cold and heat given off by the system are recycled internally to raise its efficiency. But in transport piston engines, we soon realised that the ‘waste’ cold was itself a useful product.
Because the Dearman engine produces so much cold as well as shaft power, its first application is a zero-emission transport refrigeration unit (TRU) to displace the highly polluting secondary diesel engines used to power refrigeration on lorries and trailers today. The Dearman TRU also goes into commercial trials with a leading UK supermarket this month. Follow-on applications include:
- a powerful bus air conditioning unit, which could be transformative in hot climates because it would enable the introduction of electric buses, whose range is severely depleted with the air conditioning powered from the traction battery;
- a zero-emission back-up electricity generator to displace highly polluting diesel ‘gensets’, particularly attractive to customers with heavy cooling loads such as supermarkets, data centres and office buildings;
- a diesel-liquid air ‘heat hybrid’ propulsion engine for buses and lorries, in which the two engines swap heat and cold to raise the efficiency of both and reduce diesel consumption by over 25%.
All of these applications are in development with substantial grant support from government agencies such as Innovate UK, and in collaboration with a wide range of industrial partners. Like LAES, Dearman applications re-purpose existing technologies to solve obstinate energy problems at far lower cost than ‘silver bullet’ approaches like batteries and hydrogen that have already absorbed $ billions.
The Cold Economy
Liquid air does not simply represent a collection of clever technologies, however, and is now widely recognised as a powerful new energy vector capable of storing and moving both cold and power, and of providing many different cooling and energy storage services from a single ‘tank of cold’. It is increasingly seen as the basis of a new circular ‘cold economy’ to radically reduce the environmental damage and cost of cooling.
Until recently, cooling was largely overlooked in the energy debate. This was a serious oversight, since cooling is vital for the supply of food, medicine, energy, data and comfort, yet making things cold is energy intensive and highly polluting. Existing cooling technologies consume large amounts of fossil generated electricity, and rely on HFC refrigerants that are themselves highly potent greenhouse gases. Diesel powered transport refrigeration units emit grossly disproportionate amounts of NOx and PM, the toxic pollutants that cause 3.7 million deaths worldwide each year. And one estimate suggests that in aggregate cooling causes 10% of global CO2 emissions – three times more than is attributed to aviation and shipping combined.
Demand for cooling is booming worldwide, especially in developing countries. In one extraordinary example, the IPCC has projected that the energy consumed by air conditioning worldwide could rise 33-fold to 10,000TWh by the end of the century, which is about half the total electricity consumed for all purposes in 2010. If nothing is done, even by 2030 cooling demand in developing countries will require an additional 139GW of power – more than the generating capacity of Canada – and raise greenhouse gas emissions by over 1.5 billion tonnes of CO2 per year, three times the current energy emissions of Britain or Brazil.
At the same time, however, vast amounts of cold are wasted during re-gasification of LNG at import terminals. The cold economy is a radically new approach that would recycle this and other untapped energy resources – ‘free’ cold, waste heat, renewable heat, and ‘wrong time’ energy such as wind or nuclear power produced at night when demand is low – to radically improve the efficiency of cooling, and reduce its environmental impact and cost. It would do this by converting these energy sources into a liquid air or nitrogen for use on demand. A key insight of the Cold Economy is that energy can be stored and moved as cold rather than converted into electricity and then converted again to provide cooling. The Birmingham Policy Commission on Cold reported last year that the cold economy would not only reduce emissions of CO2, NOx and PM, but could also generate annual cost savings of upwards of £40 billion worldwide.
Clean cold and global development
The dilemma raised by cooling – that it is a vital pillar of civilisation yet highly polluting – is most starkly drawn in the developing countries of the global south.
On the one hand, in most developing countries the lack of a continuous ‘cold chain’ of refrigerated warehouses and trucks contributes to high levels of post harvest food loss – the IIR estimates that if developing countries had the same level of cold chain as developed it would save 200 million tonnes of food or 14%. Food waste depresses farm incomes, raises food prices and worsens hunger. Such colossal food waste also has equally large knock-on effects: the FAO estimates that food wastage occupies a land area the size of Mexico; consumes 250 km3 of water per year, three times the volume of Lake Geneva; and accounts for 3.3 billion tonnes of carbon dioxide emissions, making it the third biggest emitter after the US and China.
On the other hand, demand for cooling is booming in fast growing giants such as China and India, driven by urbanisation and the rapid emergence of an Asian Pacific middle class – predicted to rise to 3 billion by 2030 – with a growing taste for western diets and levels of comfort. Their increasingly affluent lifestyles will be built on cooling, and if this were satisfied using conventional technologies, it would cause huge additional emissions of CO2, HFCs, nitrogen oxides (NOx) and particulate matter (PM).
By the same token, however, if the problems caused by the inadequacy of cooling infrastructure and the pollution from conventional cooling technologies are intertwined, so too are the solutions. It is becoming increasingly clear that the benefits of solving the cooling dilemma – through clean cold technologies that provide the social and economic benefits of cooling with much less environmental damage – will spread far beyond air conditioning and chilled food. In fact, I would go so far as to say that cooling is a vital hidden link between the biggest challenges facing developing countries in the first half of this century.
Those challenges were redefined last year in the UN’s Sustainable Development Goals for 2030, which not only promise to end poverty and hunger by 2030, but also set detailed targets around affordable clean energy, sustainable cities, infrastructure, climate action, decent work and economic growth, and responsible consumption. Of the 17 ‘Global Goals’ identified, clean cold technologies and the cold economy approach would have a direct impact on 14. As one example, creating a liquid air cold chain would reduce waste of food, water, land and labour; reduce food prices and hunger while raising farm incomes; and improve health by improving food safety and eliminating NOx and PM emissions from transport refrigeration.
The existence of an agreed set of global challenges is increasingly reflected in the way research funding is organised worldwide. Today government R&D spending is less likely to be allocated to individual academic disciplines, but rather to an overarching challenge, often requiring extensive inter-disciplinary collaboration. The British government adopted this approach in 2015, when it announced its overseas aid budget would be restructured to fund research tackling the challenges of the developing world. The Research Councils will disburse a new Global Challenges Research Fund of £1.5 billion over five years, and expect most of the funding to be inter-disciplinary.
The shift in research funding coincides with a dawning realisation of the importance of cooling as a critical link between major global challenges. This suggests a strong argument for establishing clean cold as an inter-disciplinary research theme worthy of every greater significant support. The rapid recent progress of liquid air and the cold economy suggests the results of such research are likely to have social and environmental impacts in developing countries far beyond the business of cooling.
The Commission on Cold recommended to Government to support the development of a system-level model of cold and integration into the energy models, for a proper understanding of the potential of the Cold Economy. As not one, but two technologies move into real-world demonstration, it is now time to act so as to better understand and unlock the potential, UK jobs and global exports as well as environment.
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Some major UK liquid air academic research projects
- T-ERA: Last November saw the launch of the Energy Research Accelerator (ERA), a major collaboration between six Midlands universities and over fifty companies to tackle some of the biggest energy challenges. ERA secured £180 million in funding from government and industry to cover three themes, one of which is thermal energy (t-ERA) – explicitly including the development of the global Cold Economy. The academic members comprise Aston University, The University of Birmingham, The University of Leicester, Loughborough University, The University of Nottingham, The University of Warwick and the British Geological Survey, and the corporate members include Cofely, Jaguar Land Rover, Highview and Dearman.
- Birmingham Centre for Cryogenic Energy Storage (BCCES): a £12 million project led by Professor Yulong Ding of the University of Birmingham, including £7 million for bespoke cold/thermal and cryogenic energy storage and engine laboratories and equipment, and £4 million for a test-bed cryogenic energy storage pilot plant, as part of the energy storage strand of the last government’s ‘8 Great Technologies’ initiative. The Centre’s themes include research into how to optimise the design, operation and integration of cryogenic energy storage systems into the grid, and fundamental research into new materials such as nano-particles that might raise the energy density of thermal energy storage.
- CryoHub: a €7 million European grant for pan-European consortium of researchers led by Professor Judith Evans, London South Bank University.The three year project will research the potential efficiency gains that might be achieved by integrating Liquid Air Energy Storage with existing cooling and heating equipment found in refrigerated warehouses and food processing plants – a good example of the Cold Economy approach. It will use large scale liquid air energy storage to absorb local intermittent renewable generation and supply it back to the grid, while simultaneously providing cooling to the cold store and reducing its peak power requirements. Project partners include universities and companies from the UK, Belgium, France, Spain and Bulgaria.