With the launch of a new report highlighting the potential of liquid air as an energy storage technology, there are bold predictions about energy security and prospects for UK industry.

Its proponents claim that liquid air could strengthen energy security, open a global market worth tens of billions of pounds, and potentially boost the revenues of the industrial gases business in the process.

So what is the liquid air concept and what are the projections of the report published today?

Put simply, liquid air is the product of taking air and cooling it to around -196C using standard industrial equipment, creating a liquid that can be stored in an unpressurised vessel and later regasified to drive a piston engine or turbine.

With 700 litres of ambient air becoming around one litre of liquid air, when heat is reintroduced to liquid air it boils, regasifies, and expands 700 times in volume. It is this expansion that can be used to power an engine or turbine.

The main potential applications of this are cited as electricity storage, transport and the recovery of waste heat.

Since the boiling point of liquid air (-196C) is far below ambient temperatures, the environment can provide all the heat needed to make liquid air boil. However, the low boiling point also means the expansion process can be boosted by the addition of low grade waste heat (up to +100C), which other technologies would find difficult to exploit and which significantly improves the energy return.

There are myriad sources of low grade waste heat throughout the economy, from power stations to factories to vehicle engines.

 

What is the potential?

According to today’s report, entitled ‘Liquid Air in the energy and transport systems: Opportunities for industry and innovation in the UK’, liquid air offers a wealth of possibilities.

It raises the possibility of zero-emission Liquid Air city cars filling up at roadside forecourts and highlights the opportunity for a nationwide network of Liquid Air energy storage plants.

Such a network could, it is claimed, develop into a business worth at least £1bn per year by 2050 and create 22,000 jobs in the grid electricity storage sector alone - and the UK Government has recognised this as a major growth opportunity for British industry.

“Liquid air has the potential to open a global market worth tens of billions of pounds,” said John Hayes, MP as Minister of State for the Department of Energy & Climate Change last year.

According to the report, liquid air could, in the short term:

· Strengthen UK energy security: a single gasometer-style tank of liquid air could make good the loss of 5GW of wind power for three hours - equivalent to almost 10% of the UK’s peak electricity needs – and help to protect British homes from black-outs.

· Reduce diesel consumption in buses or freight vehicles by 25% using a liquid air Dearman engine/diesel hybrid

· Cut emissions from refrigeration on food lorries by 80%

It also raises the possibility of zero-emission Liquid Air city cars filling up at roadside forecourts at a fraction of current fuel costs and with lower lifecycle vehicle emissions than either electric or hydrogen-powered vehicles.

With so-called ‘wrong-time’ energy from renewable generation a growing challenge to the electricity grid, and a real demand for affordable large-scale energy storage solutions both in the UK and abroad, the report highlights the opportunity for a nationwide network of Liquid Air energy storage plants that are charged by surplus energy at night - feeding the energy back into the system when it is needed most during the day.

Added revenues?

The industrial gases industry has been producing liquid nitrogen and liquid oxygen – the main components of liquid air – for over a century.

Cryogenic gases have a wide range of applications including steel-making, food processing, medicine and superconducting technologies. The properties of liquid nitrogen and liquid air are similar, so it is felt that a cryogenic energy vector could be provided by either.

Aside from the experience and expertise that it could provide to the liquid air network, it is projected that a ‘nitrogen economy’ could inject added revenues to the gases industry in the future as it makes use of a surplus product.

The gases industry has surplus liquid nitrogen production because there is four times as much nitrogen as oxygen in the atmosphere, but much less demand for it commercially. Currently there is an estimated 8500 tonnes per day of off-peak gaseous nitrogen available for liquefaction which, if harnessed and used as transport fuel, would be enough to power the equivalent of 6.5 million car kilometers daily.

 

More information

Today’s report is published by the Centre for Low Carbon Futures.

Contributors include Arup, Ricardo, Messer Group, and academics from the Universities of Leeds, Birmingham, Strathclyde, Brighton, Queen Mary and Imperial College.

The report can be downloaded from www.liquidair.org.uk.