Liquid air 'offers energy storage hope'

Electricity pylon and wind turbines (Image: PA) Renewable power generation, such as wind turbines, can produce electricity when it is not in demand

Related Stories

Turning air into liquid may offer a solution to one of the great challenges in engineering - how to store energy.

The Institution of Mechanical Engineers says liquid air can compete with batteries and hydrogen to store excess energy generated from renewables.

IMechE says "wrong-time" electricity generated by wind farms at night can be used to chill air to a cryogenic state at a distant location.

When demand increases, the liquid air can be warmed to drive a turbine.

Engineers say the process to produce "right-time" electricity can achieve an efficiency of up to 70%.

IMechE is holding a conference today to discuss new ideas on how using "cryo-power" can benefit the low-carbon economy.

The technology was originally developed by Peter Dearman, a garage inventor in Hertfordshire, to power vehicles.

A new firm, Highview Power Storage, was created to transfer Mr Dearman's technology to a system that can store energy to be used on the power grid.

The process, part-funded by the government, has now been trialled for two years at the back of a power station in Slough, Berkshire.

More than hot air The results have attracted the admiration of IMechE officials.

Mr Dearman uses his garage as a laboratory

"I get half a dozen people a week trying to persuade me they have a brilliant invention," head of energy Tim Fox told BBC News.

"In this case, it is a very clever application that really does look like a potential solution to a really great challenge that faces us as we increase the amount of intermittent power from renewables."

Dr Fox urged the government to provide incentives in its forthcoming electricity legislation for firms to store energy on a commercial scale with this and other technologies.

IMechE says the simplicity and elegance of the Highview process is appealing, especially as it addresses not just the problem of storage but also the separate problem of waste industrial heat.

The process follows a number of stages:

  1. "Wrong-time electricity" is used to take in air, remove the CO2 and water vapour, which would otherwise freeze solid
  2. the remaining air, mostly nitrogen, is chilled to -190C (-310F) and turns to liquid - this provides a compact storage medium that can later draw energy in the form of heat from the environment
  3. the liquid air is held in a giant vacuum flask until it is needed
  4. when demand for power rises, the liquid is warmed to ambient temperature. As it vapourises, the expanding gas drives a turbine to produce electricity - no combustion is involved

IMechE says this process is only 25% efficient but it is massively improved by co-siting the cryo-generator next to an industrial plant or power station producing low-grade heat that is currently vented and being released into the atmosphere.

The heat can be used to boost the thermal expansion of the liquid air.

More energy is saved by taking the waste cool air when the air has finished chilling, and passing it through three tanks containing gravel.

The gravel remains cool until it is needed to restart the air-chilling process.

Delivering durability

Highview believes that, produced at scale, their kits could be up to 70% efficient, and IMechE agrees this figure is realistic.

"Batteries can get 80% efficiency so this isn't as good in that respect," explains Dr Fox.

"But we do not have a battery industry in the UK and we do have plenty of respected engineers to produce a technology like this.

"What's more, it uses standard industrial components - which reduces commercial risk; it will last for decades and it can be fixed with a spanner."

In the future, it is expected that batteries currently used in electric cars may play a part in household energy storage.

But Richard Smith, head of energy strategy for National Grid, told BBC News that other sorts of storage would be increasingly important in coming decades and should be incentivised to commercial scale by government.

He said: "Storage is one of four tools we have to balance supply and demand, including thermal flexing (switching on and off gas-fired power stations); interconnections, and demand-side management. Ultimately it will be down to economics."

Mr Dearman, who also invented the MicroVent resuscitation device used in ambulances, told BBC News he was delighted at the success of his ideas.

He said he believed his liquid air engine would prevail against other storage technologies because it did not rely on potentially scarce materials for batteries. "I have been working on this off and on for close on 50 years," he told BBC News.

"I started when I was a teenager because I thought there wouldn't be enough raw materials in the world for everyone to have a car. There had to be a different way. Then somehow I came up with the idea of storing energy in cold.

"It's hard to put into words to see what's happening with my ideas today."

John Scott, from the Institution of Engineering and Technology (IET), added: "At present, pumped-hydro storage is the only practical bulk storage medium in the British grid.

"However, locations are very restricted," he told BBC News. "In the future, if new storage technologies can be deployed at a lower cost than alternatives, it would benefit the power system."

A spokesman for the Department of Energy and Climate Change (Decc) said it would shortly launch a scheme to incentivise innovation in energy storage. Other grants are available from Ofgem.

Follow Roger Harrabin on Twitter: @RogerHarrabin


More on This Story

Related Stories

The BBC is not responsible for the content of external Internet sites


This entry is now closed for comments

Jump to comments pagination
  • rate this

    Comment number 439.

    I have just worked out why the BBC has asked for comments.

    They wanted to know who the easily led, impressionable posters are.

    No doubt they will soon be receiving direct mail scams advising them to buy snake oil to cure all their ailments.

    Some people will believe anything.

  • rate this

    Comment number 438.

    The energy required to chill the nitrogen to -190C and turn it into a liquid will make the process very inefficient.

  • rate this

    Comment number 437.


    You should tell the Institution of Mechanical Engineers that they're ALL wrong...

  • rate this

    Comment number 436.

    397. @Typical_English_No8 What has that got to do with securing the UK's future energy supply? This article is about the discovery of a new, low-tech, cheap way of effectively storing electricity. It's amazing how any article about energy on the BBC seems to draw out every pseudo-scientific whacknut debating concepts that they understand poorly and that are irrelevant. Well done, Dearman!

  • rate this

    Comment number 435.

    Presumably if everyone moves over to electric cars then these would be charged overnight - reducing the amount of 'wrong time' electricity?

  • rate this

    Comment number 434.

    You can mark this down as much as you like but the scheme is still hare brained.

    Check out:

    The part to note is efficiency.

    Mark this down but don't expect any energy savings from this route.
    Merely free lunches for those on the gravy train.

    Truth hurts.
    Life is like that.

  • rate this

    Comment number 433.

    430 ConnorMacLeod : You are probably right, I am no expert. I just believe in the future of renewable energy and am dreaming about having Solar Panels on my roof, hooked into the grid and earning credits for use the next day while I am sleeping
    I have designed a "Solar Building" for homeowners that have badly oriented roofs and am hoping and wishing for the GOP to get out of the way of renewable's

  • rate this

    Comment number 432.

    "Sidney Monroe
    If AGW did not rely on guesswork one of the computer models would have made an accurate prediction by now"

    Since you demand that every prediction, even those with strong caveats and uncertainties, be met every time before you are satisfied, whereas the sceptics can be as inaccurate as they like, you set a very high requirement. But then you never give citations for your claims.

  • rate this

    Comment number 431.

    I sincerely hope that the CO2 that is removed from the air isn't returned to the atmosphere.

  • rate this

    Comment number 430.

    423.Looney Limey
    420 IsthistheAnswer

    I don't think you're looking at the economics. Scaling down is generally much more expensive and hence impractical from a cost/benefit viewpoint.
    Besides - would YOU want a tank of liquid air at minus 200 degrees C in your basement ?
    Very dangerous - if there's a fire in your house it would be big BA-DA BOOM !

  • rate this

    Comment number 429.

    @20. Ian Savell
    The only issue in my mind is, what is the ratio of liquid storage to energy storage? A few thousand cu.m. of liquid air could be quite a hazard. Underground storage?
    I do not see why it is a great hazard. Nitrogen is not combustible. The only dangers are cold burns or explosions if pressurized. In both cases the liquid turns to gas and returns to the atmosphere harmlessly.

  • rate this

    Comment number 428.

    Am I missing something? Why not in times of high wind and low demand, divert the electricity directly into storage batteries? Of course there is the problem of space for them, but that is also the case with liquid air storage. This way there is no need to use, (waste) some of the energy in the conversion processes.

  • rate this

    Comment number 427.

    I have this big windmill that winds up a big rubber band when the wind blows. When the wind stops blowing the rubber band unwinds turning the windmill into a fan, which blows into a turbine to produce electricity. If I introduce a ratchet I can stop the rubber band unwinding until I let it.

    Or I could get the band to drive a generator directly... or the wind could do it.

    Problems, problems!

  • rate this

    Comment number 426.

    The unpredictability is solved by connecting to the grid and getting credits for what is not used. Downside is that if the lines go down & you do not have energy stored you will be out as well. That's how they have it in U$A, but as time goes by and the GOP get stomped the renewable industry in USA will be let loose and then things will change
    This freezing storage is a great idea
    Don't knock it!

  • rate this

    Comment number 425.

    @ 118 Sorry, you've completely got the wrong end of the stick with that one..... Why on earth would you need "miles of pipework"?? You only need to use the spare generating capacity of the turbines/renewable source, NOT the air around them. Oddly enough there's air near power stations too! So you simply use the spare capacity to liquefy air at the point of storage, NOT the point of generation.

  • rate this

    Comment number 424.

    Monopolistic energy companies hava to find new technologies, new way of doing things to keep their hegemony on the world economy. They don't care if these technologies are too expensive or bad for the environment. Russian scientist claim that there is no end to gas-oil resources. As long as there is magma, there will be gas-oil...

  • rate this

    Comment number 423.

    420 IsthistheAnswer : Too many people have forgotten about the millions of homes that can get solar panels on their roofs or a side building
    You are spot on there lad about scaling this down for storage during day for the night's use, U$A homeowners can also connect to the grid, put in what is not used and get credits if only the GOP & Big Oil would get out of the way and stop blocking everything!

  • rate this

    Comment number 422.

    Seems like a very plausible relatively low-tech way of storing energy. As it is only storing electricity that is produced excess to demand at any one time, it can only be a win-win situation, even if it is not very efficient.

    The problem with renewable sources of energy like wind and solar has always been their unpredictability. This is a step towards solving that.

  • rate this

    Comment number 421.

    327.Frank Lund
    Why not remove the CO2 when it's liquid part way through the cooling process?

    You'd have a hard job. CO2 sublimes (changes directly from gas to solid) with no liquid phase inbetween. It only becomes liquid at pressures greater than 5.1 atmospheres. You'd have to pressurise the mix, which would take a lot of energy. Drunken Hobo is correct...

  • rate this

    Comment number 420.

    This looks far safer than cracking hydrogen off water and storing, but an alternative all the same. If this could be scaled DOWN not UP then it could be possible to have home based systems using solar during the day to draw on it at night. may not replace your total needs. but would reduce your demand on the grid...


Page 6 of 27


More Science & Environment stories



Try our new site and tell us what you think. Learn more
Take me there

Copyright © 2015 BBC. The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.