Liquid Air in the energy and transport systems
Opportunities for industry and innovation in the UK
Royal Academy of Engineering & Centre for Low Carbon Futures Liquid Air conference, May 9th 2013
To see the individual presentation slides, please click here.
Professor Richard Williams, Pro Vice chancellor, University of Birmingham
Professor Richard Williams launched the discussion by reviewing the three challenges facing UK energy policy in the UK: decarbonisation, security of supply and the cost of energy. So far, the aim has been to decarbonise electricity and the grid, however, the UK depends on nuclear power and coal to produce electricity and, with coal mines closing, we need to look at alternatives. In terms of security of supply, there is the ongoing concern around over-dependence on gas. Rising energy costs have increased energy poverty, and public tolerance more generally is wearing thin.
Professor Richard Williams suggested that the question to be considered now is where energy storage fits in with these challenges. Some key issues to be addressed were summarized. It was concluded that energy storage is a somewhat forgotten but vital part of the energy network and that we need to look at engineering solutions that are scalable and can be delivered sooner rather than later.
Morning Session 1: Power Applications
The first session was introduced by Professor Nigel Brandon, from Imperial College, who pointed out that liquid air, as an energy vector, has to compete with other technologies and so we must explore the attributes and challenges of this technology and the collective paths to see it forward.
Liquid Air Energy Storage
Dr Rob Morgan, University of Brighton
Dr Rob Morgan suggested that there could be 10GW of new storage capacity available in the UK. He set out to answer the question: does liquid air offer a practical, cost effective solution for grid scale storage?
With thermal recycling, the efficiency of the Liquid Air Energy Storage process can be up to 60%, which is less than pumped hydro but in line with expected market requirements. It is also an efficient way of converting low-grade waste heat into power. The technology is put together from standard components and main components are available at scale. In terms of the economics, for a 20MW plant, the costs can be driven down to £995 per kW as more plants are built. If we make the plants bigger (200MW), however, costs can be pushed down as far as ~£500 per kW.
Integration with industrial processes
Professor Yulong Ding, University of Leeds
Professor Yulong Ding started the discussion on different technologies available for storing energy and identified that many advanced energy storage technologies are below Technology Readiness Level (TRL) 5, whereas Liquid Air Energy Storage has advanced to TRL 7. He then focused on the integration of cryogenic energy storage (CES) technology with industrial processes:
- Integration of CES with solar thermal power generation could give a net power output significantly higher than the summation of a solar only system or a CES only system
- Integration of Cryogenic Energy Storage (CES) with peak shaving natural gas power plants could significantly increase the power generation efficiency (about 70%) with CO2 fully captured. The integrated system has a potential to increase the peak shaving capacity by 100% if retrofitted to an existing plant. For a given peak-shaving capacity, the integrated system only requires half of the size and hence a significant reduction in the capital investment.
- Integrating with CES with nuclear power plants could significantly increase the efficiency, provide backup power, and substantially increase the peak shaving capacity. However, safety is very important in the nuclear industry and any new ideas need many years to be approved.
Energy storage and the grid – market opportunity and policy requirements
Anthony Price, Electricity Storage Network
Anthony Price highlighted that everywhere we look we now see wind turbines, solar panels and other changes in the power systems. Low carbon generation technologies have many advantages but increased use of renewable generations provide a fluctuating supply of electricity and this needs to be controlled. . Domestic electricity energy demand is increasing, as is the daily power peak. Power flows on the network are changing with some consumers generating power and sending it back onto the network.
Many large power stations are being closed, and some of the gap is being filled by onshore and offshore wind.
At the moment, one form of balancing is provided by short-term operating reserves, which provide up to 4 hours output when required. In 2020 wind generation in GB might be 4 times its current level, so increasing the expected requirement for Short term operating reserve. This service could be provided by liquid air technologies.
Mr Price noted that there are four tools for system balancing - flexible generation, demand side response, storage and interconnectors. In terms of storage, if liquid air can be deployed rapidly, it will have significant advantages over other technologies in providing balancing services. However, the power industry is operated by private companies and without the right signals for investment, the construction and deployment of new projects becomes difficult as investors expect a return on their investment, comparable to other projects of similar risk.
In order to determine a target for storage, a starting point is to consider that there are 22GW of renewables projects planned to be commissioned by 2020 and if we estimated that 10% of this capacity should be matched against storage, then we have the necessity for 2GW of storage. Liquid air could play a part in providing this storage capacity but we changes in the business model and changes in policy are needed in order to drive it forward.
Chair – Nigel Brandon
Rob Morgan, Anthony Price, Yulong Ding
A key conclusion from the panel was that all storage technologies will have a part to play. Each technology has particular characteristics that make them suitable for particular uses. For example, there are economic and geographic constraints to some technologies. There is a role for batteries at a domestic or community level but liquid air could be useful for sizes above that. Other characteristics are also important such as:
- Can you switch it off?
- How long can it operate?
- What are the lifetime costs
- What are the through-life costs?
Further research is required in the longer term to explore issues with efficiency, integration and optimization of the system. One of the crucial points, in particular, is looking at increasing the efficiency of the liquefaction process. Very little research has been does on this in the West and US, but there is research from China and Japan that suggests significant improvement of the efficiency of liquefaction could be achieved.
Morning Session 2: Transport
Professor Neville Jackson, Ricardo
Professor Neville Jackson, of Ricardo, introduced the session on the transport applications by defining liquid air as a disruptive innovation. Unlike evolutionary or radical innovations, a disruptive innovation can have a significant impact on a market and on the economic activity in that market.
Why is having a tank of cold liquid interesting for mobile applications?
Professor Colin Garner, University of Loughborough
Professor Colin Garner set out to address the basic principles behind the use of liquid air as an energy source for mobile applications. If a unit containing liquid nitrogen at 77 K and a pressure of 1 bar was warmed to ambient temperature (300 K), the liquid nitrogen would expand in volume by 700 times to a gaseous state. Using a preliminary isochoric process (constant volume) to warm the liquid nitrogen, it is possible to develop a very high pressure rise and generate work by letting the highly pressurised liquid expand (in a reciprocating engine or turbine). Including an outside heat source in the expansion process would enable the LN2 to expand isothermally and hence maximise the energy output.
Professor Garner identified that storage of liquid air is relatively simple. Firstly, it can be contained at 77K which is an easier temperature to maintain than that required for liquid hydrogen. Secondly, liquid air and liquid nitrogen can be maintained at atmospheric pressure and the large size of the molecules lowers the risk of a leakage of the gas. Liquefied natural gas (LNG) is routinely transported around the world, and increasingly used as a transport fuel, so storage practices are already well known and established. Moreover, the quick re-fuelling rate of liquid nitrogen gives it an advantage over conventional batteries which charge at a slow rate and are plagued by thermal barriers. Liquid air would therefore be a competitive alternative to conventional batteries.
From a low grade source of heat at ~393K (~100 oC), conventional heat recovery systems have a sink temperature of only ~293 K (~20 oC), and therefore a low maximum potential to produce work with a best possible yield of ~21%; however, since a liquid air engine has a much lower initial working fluid temperature (~77 K) it has a much higher maximum potential to produce work of 3 to 4 times this value.
Professor Garner concluded that liquid air could lead to radical new engine architectures.
What might you do with a tank of cold?
Dr Andy Atkins, Ricardo UK
Dr Andy Atkins identified several ideal applications where liquid air might be pertinent. Liquid air has an energy density comparable to mid-range batteries, such as NiMH or LiIon, and a power density dependent on the engine design. The tunable nature of this meant that, for some applications, this would make a liquid air engine a preferred solution.
In terms of the engine design itself, the 2 stroke Dearman Engine is likely to be based on internal combustion engine design principles, but behaves like an internal-boiling steam engine. The current rate of expansion of the liquid nitrogen observed in tests is approaching the expansion rate of a naturally aspirated gasoline engine.
Dr Atkins stressed the need to select appropriate technology for the application; taking into account the packaging of the technology, economics, energy needs and power needs.
Will it save you money and reduce emissions?
Nick Owen, E4tech
Nick Owen began by identifying the key attributes that differentiate a liquid air-engine from competing technology. The characteristics unique to a liquid air engine include; the ability to use a low grade or ambient source of heat (<100°C), zero emissions produced at point of use and relatively safety. It can also be produced using common resources and processes so that it could be cheaper if it were made at the same volume of an internal combustion engine, has a fair carbon footprint with the potential for improvement if surplus off peak renewable energy was used. However, a liquid air engine has a relatively high consumption of “fuel” by weight compared to an internal combustion engine.
The three potential markets for a liquid air engine are:
- Zero emission propulsion markets: including urban transport, transport in industrial environment, inland waterway vessels, airport transport. Incumbent solutions include battery electric and fuel cell solutions however, both have a significant payback period. Liquid air could provide lower capital costs than an electric vehicle and compete with the lifecycle CO2 emissions of both incumbent technologies if LN2 is sourced effectively.
- Short and long-haul surface markets: including trucks, rail locomotives and shipping. Incumbent waste heat recovery solutions include turbo compounding and use of the organic Rankine cycle. A Dearman engine used as a waste heat recovery device, or a split cycle liquid air engine with on-board regenerative liquefaction could both lower the fuel consumption and CO2 by up to 30%. Moreover, a liquid air engine could have an attractive payback period of less than 3 years.
- Refrigerated transport market. Existing units are driven by an internal combustion engine but liquid air could provide both the energy for the vehicle and the cold for refrigeration. Simple systems offer over 60% CO2 benefit with potential to improve CO2 emissions by >80% if an air engine is used.
Chair – Neville Jackson
Colin Garner, Andy Atkins, Nick Owen
In the question and answer session audience members asked for clarification of the use of liquid air versus the use of liquid nitrogen as the two vectors were used interchangeably throughout the talks. The panel noted that nitrogen is one of the key components of air so the two vectors are similar however, liquid nitrogen is used in discussions at the moment as it is in mainstream use by the industrial gases industry and therefore, easy to access. Liquid air would be a longer term solution.
Members of the audience raised key questions such whether liquid air or nitrogen stored in tanks would boil off. The panel noted that boil off will occur, however, the rate depends on the level of insulation, size and volume of the tank as well as how long it is being stored. The panel added that this problem is not exclusive to liquid nitrogen or liquid air and would affect any gas in a liquid state however, it is well managed by the existing industrial gas industry.
The audience also questioned whether taxing fossil fuel was necessary to support novel energy vectors such as liquid air. The panel concluded that fossil fuels are the lowest cost and best energy source from a density perspective however, they are not sustainable and therefore tax is necessary to give sustainable innovations such as liquid air a chance to be competitive.
The audience asked about the safety effects of a liquid air tank rupture. The panel responded that liquid air is non-combustible and would evaporate in a rupture without significant hazard in an outdoor situation. Moreover, the liquid air or liquid nitrogen itself could be used to suppress any fire created from other sources in the case of a collision.
The competitive advantage of the UK in producing liquid air technology was raised by members of the audience. The panel agreed that the fact that innovators of liquid air, Highview Power Storage, the Dearman Engine Company and Ricardo, were all based in the UK was not an accident. Moreover, the UK has a strong academic base and a proven history of mechanical engineering and the use of cryogenics. For the UK to stay at the forefront there will need to be alignment of skilled people and support from the government and investors. Panel members later added that from a patent perspective the UK is very solid.
Building the LN2 Highway
Steve Cooper, Spiritus Consulting
Steve Cooper presented on the existing support for a liquid air infrastructure. Mr Cooper began by noting that the worldwide gas industry has significant growth projected over the next 5 years (~7% CAGR). The UK has slow volume growth but solid pricing performance. The main UK players are BOC, Messer, Air Products and Air Liquide who currently serve gas demand for steel manufacturers, metallurgy, electronics, chemicals, refining, pulp and paper and food industries. Mr Cooper identified that production is focused around these main industrial conurbations supplying 4200 tonnes per day of Pipeline Nitrogen and 3800 tonnes per day of Liquid Nitrogen amongst other gases. Mr Cooper suggested that there could be theoretical excess liquid production capacity of ~40%. The liquid nitrogen network is already well established with almost 6,000 storage tanks installed on customer sites and deliveries by ~400 tankers The existing network of industrial gas plants is spread out throughout the UK and close to major highway routes, enabling efficient distribution throughout the country.
Mr Cooper also pointed out that the industrial gases industry uses mature and reliable technology with plant availability of ~99.5% with plant overhauls every 5 years and intrusive maintenance only once every 15 years. Liquid air plants would use this exact same technology and could be located on the spare land of existing gas facilities, which have the necessary grid connections in place and the experienced staff on hand.
Given the existing infrastructure, a new tank can be installed on a customer’s site within 2 weeks.
Refueling systems for hydrogen have already been designed despite the fact that hydrogen is a more difficult substance to handle. Using this experience, a liquid nitrogen refueling infrastructure could also be rolled out.
Mr Cooper concurred with previous speakers that liquid nitrogen is relatively safe and certainly less hazardous than other fuels such as petrol. The two main hazards are; 1) The cryogenic temperatures, however, harm can be minimized by using the double wall insulated vessels and personal protection currently employed in the industry, 2) Asphyxiation, which can be managed by avoiding installations near confined spaces use of oxygen monitors and comprehensive training Both hazards are commonly managed in the industry. Moreover, the European Industrial Gases Association (EIGA) and British Compressed Gases Association (BCGA) both have developed internationally recognized codes of practice for handling liquid nitrogen.
Afternoon Session: Markets
David Strahan, Editor
The afternoon session was chaired by David Strahan, the editor of the liquid air report.
William Holt, University of Strathclyde
William Holt researched how liquid air technologies could be useful in Scotland.Scotland’s target is for the equivalent of 100% of Scottish consumption of electricity to come from renewables by 2020 and for Scotland to be generating twice its needs; half the electricity it generates is intended to be exported.
Scotland has a decentralized nature of supply, which makes liquid air technologies attractive, as they are not geographically constrained.
The government of Scotland has recognised that energy storage is vital but currently
- Pumped hydro – Expansion of installed capacity is unlikely based on the economics
- Compressed air – no caverns for storage reservoirs and it requires fossil fuels
- Batteries – the scale does not meet the needs
- Hydrogen fuel cells – great theoretical potential but still experiencing economic, scale and cost issues
William suggested that liquid air has proven processes, no geographic constraints and existing supply chain capacity within Scotland.
Using a ratio of 1:3.5 storage capacity to intermittent generation capacity (a rationale used in previous reports from EU countries to support wind deployment – see Scotland case study for more detail), he concluded that in order to achieve Scotland’s 2020 target for renewable energy generation, 3 GW of storage would be required; this could be 32 x100 MW LAES plants.
There is a £5.7bn programme for network upgrades by 2020 and with the Scottish commitment to renewable generation, there is a recognised need for economic energy storage capacity at sufficient scale and as soon as possible.
For more detail, please refer to the Scotland case study.
Liquid air and LNG – the value of cold
Dr Phil Carter, National Grid Grain LNG Limited
National Grid Grain LNG, Highview and Costain are bidding for a DECC grant to build a demonstration project of a fully integrated liquid air energy storage plant of up to 6MW hosted on National Grid’s Grain LNG site. The plant would have 5 hours of operation, making it the largest demonstration of new energy storage technology in the UK. The project has been shortlisted to the final feasibility stage and a decision is expected in June.
The LNG terminal on the Isle of Grain is the 8th largest in the world and the UK was the 3rd largest importer of LNG in 2011. National Grid Grain LNG has energy warehousing, cryogenic experience and LNG terminals worldwide may provide export potential opportunities for UK’s energy storage know how. Isle of Grain is an energy hub, with two CCGTs, an aviation fuel facility, BritNed 1,000MW interconnector, etc and importantly Grain LNG is linked to E.On’s power station by a heat pipe providing Grain LNG with low grade hot water to create one of the largest CHP schemes in Europe.
LAES integrates with the Grain LNG plant by using the cold from the LNG to assist refrigeration and the heat from the heat pipe in driving the turbine. The advantage is that LAES is not dependent upon geological features and can be built where required with normal equipment including hot and cold stores if necessary.
Can liquid air be part of the solution abroad - German market
Tim Evison, Messer Group
Tim Evison commented on the attractiveness of LAES in Germany. Messer is known for innovation, and being family owned, they consider longer time frames and the next generation. They recognize that there will be a need for solutions in the future that we don’t have today.
The German energy plan is based on high levels of renewables, energy efficiency and imports/exports. The report for the second half of March, found that Germany had problems in ensuring grid stability and had to take action on 38 occasions. Germany is pushing the limits of what is possible with respect to renewables, which form 23% of electricity today. Germany is phasing out nuclear power by 2020 and instead using cheap nuclear energy imports from France whilst at the same time dumping wind energy on Poland and Czech Republic.
Germany procured several expensive studies that claimed that renewable power can be used to meet Germany’s energy requirements but what is needed is energy storage. The cryogens, the tanks and ancillaries are ready in Germany except the turbine at the end so it seems that there is no reason not to consider deploying LAES to provide the much needed energy storage for the future.
At the moment, Pumped hydro energy in Germany is enough for only 6 hours. If there is no wind for 3 days, 300 times as much pumped hydro facility would be required. The technology is a very interesting alternative and support for demonstration projects in Germany would surely be forthcoming.
To conclude, LAES does have a part to play in energy storage in Germany, however industry, energy sector, university and government partnerships are needed to take it forward.
For more information, please see the Messer Case Study.
German coverage of the conference can be found on Messer’s website.
LAES – the potential for application in industry
Steve Saunders, Arup
Steve Saunders of Arup began by identifying the key problem LAES seeks to address; surplus generation on the grid relative to demand. Mr Saunders added that LAES could fill a gap in the energy storage market for 10 – 100MW solutions and is not geographically constrained like Compressed Air Energy Storage or Pumped Hydro, the two incumbent grid scale solutions. Mr Saunders also pointed to the relatively low capital cost of the liquid air technologies and the fact that it is based on mature technologies.
The fact that the technology can also recover waste heat and cold makes it a particularly exciting vector. Many of the clients that Arup serve have large energy demands that peak during certain times. Along with knowledge of the systems to be deployed systems may also have waste heat or excess cold that has to be managed. The potential to recover some of this ‘waste’ energy to help offset imported electricity costs make this an interesting cost model that warrants further investigation.
However, Mr Saunders concluded that Liquid Air Energy Storage must be scalable to maximise the potential benefits and the challenge to the industry is to make is cost efficient at smaller scales to match the varied demand by Clients.
For more information, please see the Arup Case Study.
The global value chain – harnessing the opportunity?
John Leggate, Quintal Partners
John Leggate claimes that Highview Power Storage and the Dearman Engine have the potential to be “world class opportunities”. That said, liquid air technologies in general are capital intensive infrastructure plays and would collaboration between government, and financial and strategic investors to bring this big idea to a viable commercial reality.
Mr Leggate noted that in the past we have had energy solutions reach hype and then fall out of favour; examples include Nuclear Fusion in the 1960s and the Hydrogen Economy of the 1980s and potentially carbon capture and storage – therefore is it reasonable to propose the “Nitrogen Economy” as a new solution to the problems of finite resources and carbon footprint? Nitrogen might work because of the alignment of market pull and relative ease of implementation. Mr Leggate noted that there is clear demand pull with the increasing volume of renewables on the grid, the emergence of the renewable heat agenda, the need for storage and the growth of the “cold chain”. Moreover, there could be relative ease of implementation given that nitrogen is environmentally in tune, fully scalable to grid requirements and the thermodynamics of the process are well understood, if the economics can be made to work in a sustainable way.
Mr Leggate added a new dimension to the day’s discussion of early adoption sectors by looking at it from an investors’ perspective. In terms of power storage; back-up power generation for data centres, mines and continuous manufacturing as well as renewable heat recovery for coking plants and process plants were seen as the first markets for liquid air. In transportation, Mr Leggate agreed with other speakers in identifying refrigerated vehicles, delivery vans and refit buses as the primary markets for liquid air.
Mr Leggate called for a two pronged approach going forward; further discussion into the specific role of liquid air in these markets and build market confidence by building prototypes such as a 20MW Liquid Air Power Storage facility and a running engine. Once this is in place there will be new questions to answer; specifically who in the UK will pay and support liquid air technology to be a reality and, if not in the UK, then we need to look beyond.
And finally with respect to the value chain and value extraction opportunities from the “Nitrogen Economy”, these will fall into the following categories: a) intellectual property/ licensing rights; b) consultancy; c) process and engineering design; d) global sourcing and supply chain logistics; e) project management – including construction and commissioning; f) ongoing operations and upgrades and g) project financing. The extent to which the UK will lead on any specific sub sector will depend upon which technologies are adopted and commercialized, in which countries and at what pace.
The extent to which the UK will earn a material economic rent will be contingent on having a truly competitive offering in the global market place and having in place all of the requisite intellectual property rights. Within this, the UK needs to demonstrate to the world that the UK itself has deployed the technology, with significant commercial scale demonstration projects.
Nigel Brandon, Neville Jackson, Richard Williams
Professor Brandon summarized two salient points from the day’s discussion; firstly that there is no pressing need for storage today, however, it will become an important part of our energy future and therefore, we should invest in laying down the ground work now so that it will be mature and de-risked when it is most needed. Secondly, Professor Brandon urged the audience to make liquid air a fixture on the academic and research agenda so as to help bring skilled people on board.
Professor Jackson concluded that there are no silver bullets in transport but that liquid air could play a role in solving some of our problems in this sector. The challenges liquid air faces are the same as all disruptive technologies; the first market is not obvious, it doesn’t have a proven track record and the thermodynamics are difficult to understand. Professor Jackson noted that with LNG a likely permanent energy fixture of the future, we must now begin to address how we can transfer the knowledge and hardware of this sector to liquid air.
Professor Williams was keen to stress the importance of the Liquid Air Conference in bringing together such a diverse array of sectors and backgrounds. The conference should act as a launching point to raise aspirations and look at liquid air in more detail. The Liquid Air Energy Network will provide the support for collaborations and development going forward. Professor Williams added that some of the conclusions from the day’s presentations had been conservative (impact on economy, targets for stored energy capacity) and suggested that the future of liquid air could go beyond the scope identified at the conference.
Key points raised by the floor were the need for further scientific research into liquid air as an energy vector, key challenges faced by the business model such as ownership and development going forwards. Moreover, one member of the floor noted that progress is already being made in terms of government support with a new TSB grant in the pipeline to support integration into energy systems and harvesting low-grade heat to provide power.