Liquid Air Engine

[brian eiland]

Dearman Engine runs on liquid air

A new zero-emissions engine capable of competing commercially with hydrogen fuel cells and battery electric systems appeared on the radar yesterday when respected British engineering consultancy Ricardo validated Dearman engine technology and its commercial potential. The Dearman engine operates by injecting cryogenic (liquid) air into ambient heat inside the engine to produce high pressure gas that drives the engine - the exhaust emits cold air. It's cheaper to build than battery electric or fuel cell technology, with excellent energy density, fast refuelling and no range anxiety.

Think of the Dearman engine as an internal combustion engine without a spark plug, with cryogenic liquid air injected instead of petroleum. There is no combustion, but because the air is stored at cryogenic temperatures (sub minus 160 degrees Celsius), ambient temperatures can superheat it and return it to gaseous form, causing a rapid expansion of gases.

When the piston is at the top of the cylinder, some heat exchange fluid is admitted to the engine cylinder. Immediately after this a small quantity of cryogenic liquid is sprayed into the cylinder; it comes into contact with the ambient (but in relative terms to the cryogenic temperatures, super hot) heat exchange fluid and boils very rapidly, building up pressure and pushing the piston down.

At the bottom of the stroke the exhaust valve opens and the returning piston pushes the heat exchange fluid and air out of the engine where the heat exchange fluid is recovered and the cold air exhausted. At the top of the stroke a new cycle begins.

Using cryogenic liquids as the energy carrier makes a lot of sense, most importantly because the energy density of liquid air compares favourably to the only two current technologies (Nitrogen and batteries) in contention for powering the zero-emission engines that will be used in subsequent generation automobiles, ships, forklifts, motorcycles, buses, trucks, mining equipment, through to certain classes of gensets.

Convenience (aka very fast re-fuelling times) is likely to be the other big selling point in comparison with the other zero emission technologies.

Air is superabundant and cryogenic liquids are already produced and distributed in huge volumes in all countries, making the necessary supporting infrastructure for Dearman engine introduction inexpensive.

Liquid air is a low-risk energy source - it is stored at low pressure and has no combustion risk. Whatsmore, the insulated tank used for is storage is cheaper to produce than re-enforced high-pressure vessels and the marginal cost of additional energy storage is very low - just increase the tank size.

On top of all of that, there are number of other technologies servicing different scales of applications that are being developed that could all use the same energy vector (cryogenic liquid) and share the infrastructure. Last but not least, none of the proposed technologies require scarce materials.

http://www.gizmag.com/dearman-zero-emissions-engine/21201/

Ricardo and Dearman are now working together to bring the technology "closer towards commercial maturity.

[rasorinc]

This sounds like very good news. Wish they would post a picture of the engine.

[Tim B]

Unless I'm much mistaken, this is the exact opposite theory to the condensing steam engine. In fact, the thermodynamics follows that of any gas engine, but now with a state-change included. So yes, it will work very nicely.

Of course, I don't see a lot of liquid air around, so when you take the compression or cooling process into account, it might not look so clean. The two storage options (ie. high-pressure ambient temperature vs low-pressure low temperature) each have their own problems as well. It will be interesting to see what (if anything) happens.

Tim B.

[gonzo]

The zero emmission claims always fail to mention the emmissions created to make liquid air, hydrogen or whatever they use.

[Yellowjacket]

As Gonzo noted, it takes a huge amount of energy to create liquid air. Not only do you have to compress the heck out of it, which creates heat, which you not only don't recover, you waste, but you have to use energy to cool it even more to liquify it.

If you look at how much work it takes to compress gas, if you can't use the heat generated during compression (like you do with a conventional piston or turbine engine), you are going to be terribly inefficient from a total energy usage standpoint.

Then there are losses in storage.

Then when you start to expand it, everything gets really cold, so water condenses on everything. Then you have to keep the cylinders warm, which uses more energy to pump air across the cylinders....

While you can probably store energy that way and compared to a battery, the energy storage per pound might not be bad, you've gotta have a place (like mine or an explosives factory) where you can't use any other kinds of engines for it to make any sense.

If you consider the total cost of the energy, is going to be terribly expensive.

[Mr Efficiency]

I don't understand the need for the injection of the heat exchange fluid, wouldn't the cylinder walls be warm enough if a conventional water circulation through the block and a radiator were used ? Working in reverse to the normal heat exchange, of course.

[Petros]

this would be a very dangerous "fuel" to carry in any vehicle, super high compressed liquid air? if the tank ruptures, everyone within about 30 ft of it is dead. The potential energy of it is not chemical but rather from the compression, which means if the compression is lost (like in an accident) it is all released at once.

It is not so green either, you are not counting the energy it takes to compress the air. this is not too different from the compressed air engines used on those little plastic cars they use in India. The only advantage they have is there is little/no emissions where the car is used, so they can be used inside large factories, subways or heavily congested areas where air pollutions is a serious problem. And the creation of the compressed air (or liquid air) is done somewhere else, but it takes just as much if not more energy to create it. The liquid air is just more energy dense than compressed air, so the containment vessel is smaller for any given amount of energy.

[Mr Efficiency]

Petros, this was in the opening post, I can't speak to how accurate the claims are, though.
"Liquid air is a low-risk energy source - it is stored at low pressure and has no combustion risk. Whatsmore, the insulated tank used for is storage is cheaper to produce than re-enforced high-pressure vessels and the marginal cost of additional energy storage is very low - just increase the tank size."

[P Flados]

"Liquid air" is mostly liquid nitrogen with some liquid oxygen. Huge cost to create, storage is usually low pressure thermally insulated tanks that slowly bleed off to stay cold. Other than the risk of handling cryo stuff this is not terribly risky.

Cryo plants are very very costly and results in an overall cycle that has terrible efficiency regardless of how well the "engine" performs.

Only if you build cryo plants that generate the "liquid air" on wind power or some other "free" energy source would this have a chance of being worth anything. Scaling something like this up for widespread use would be a "fat chance".

[P Flados]

Originally Posted by Mr Efficiency

I don't understand the need for the injection of the heat exchange fluid, wouldn't the cylinder walls be warm enough if a conventional water circulation through the block and a radiator were used ? Working in reverse to the normal heat exchange, of course.

Vaporization of cryo fluids absorbs lots of heat. If you put a lot of fins on the outside of the cylinder, transfer of heat via the air is possible, but you are very limited. If the cylinder gets below freezing, any humidity in the air will build up a layer of frost. This reduces overall heat transfer, makes surfaces colder and accelerates the frost buildup. Soon you have a great big chunk of frosted over non-functional junk.

Combining cryo air injection with combustion would allow you to provide the heat of vaporization efficiently and allow you to get a lot of air in the combustion chamber without a turbo. Simple expanding of cryo with some other "fluid" does not make sense. Concept would be ok for a combustion engine, but lousy when the complete cycle is considered (see previous post)

[Mr Efficiency]

Originally Posted by P Flados

Vaporization of cryo fluids absorbs lots of heat. If you put a lot of fins on the outside of the cylinder, transfer of heat via the air is possible, but you are very limited. If the cylinder gets below freezing, any humidity in the air will build up a layer of frost. This reduces overall heat transfer, makes surfaces colder and accelerates the frost buildup. Soon you have a great big chunk of frosted over non-functional junk.

Combining cryo air injection with combustion would allow you to provide the heat of vaporization efficiently and allow you to get a lot of air in the combustion chamber without a turbo. Simple expanding of cryo with some other "fluid" does not make sense. Concept would be ok for a combustion engine, but lousy when the complete cycle is considered (see previous post)

If the process of producing the liquid air is so inefficient and energy intensive, ( I know "nuffink" about it really ) compared to the output when used in the engine, the obvious question is would be why they be bothered developing it ? Seems pointless.

[Yellowjacket]

The objective of a lot of these "odball" engines and cycles is to get better energy storage, in terms of energy stored to weight, than batteries. While this appears to do that, batteries are much more efficient in terms of charge/discharge efficiency than something like this, and batteries aren't that good in terms of storage efficiency.

Batteries have a miserable power to weight when compared to any fuel, and this approach does too. The huge amounts of energy lost due to heat in the compression process really dooms this kind of energy storage system.

As noted nothing is free, this is a heat engine, it just uses a cold sink. The idea of burning the liquid air to supply that heat is a good idea, but trying to get a fire lit in a combustion chamber that cold would be a trick.

If you were doing burning, it would be the same thing as a conventional engine, except that you moved the compression process to another facility, lost a lot of heat, and then performed the combustion process later... Not efficient at all.

[Mr Efficiency]

I know dry ice ain't cheap !

[P Flados]

Originally Posted by Mr Efficiency

If the process of producing the liquid air is so inefficient and energy intensive, ( I know "nuffink" about it really ) compared to the output when used in the engine, the obvious question is would be why they be bothered developing it ? Seems pointless.

The objective is usually to generate some hype and then con some investors. The fact that they hide the flaw is usually just the same as the deceptions in more obvious rip offs.

As I noted before, there is a potential. This goes with a combination of cheap raw energy (wind, snow melt hydro, geothermal) and the storage discussed by yellowjacket. The fact that there was no discussion of the cryo production has me thinking more "scam" than "innovation".

[brian eiland]

Originally Posted by P Flados

The objective is usually to generate some hype and then con some investors. The fact that they hide the flaw is usually just the same as the deceptions in more obvious rip offs.

As I noted before, there is a potential. This goes with a combination of cheap raw energy (wind, snow melt hydro, geothermal) and the storage discussed by yellowjacket. The fact that there was no discussion of the cryo production has me thinking more "scam" than "innovation".

Originally Posted by brian eiland

Ricardo and Dearman are now working together to bring the technology "closer towards commercial maturity.

The people at Ricardo aren't into scams:

Ricardo is a leading global provider of product innovation, engineering solutions, clean technology and strategic consulting. Through our advanced and well-equipped technical facilities in North America, Europe and Asia we serve a wide and balanced customer base including the market-leading brands across a range of industrial sectors, as well as government agencies and national and international regulatory authorities. We are a public company quoted on the London Stock Exchange and a constituent of the FTSE techMark 100 index.


Since Ricardo was founded nearly a century ago, the company has been renowned for its track record of highly successful research-led product innovation and development expertise. With our internally funded research activity and proven ability to attract the best of international scientific and engineering talent, Ricardo has been able to maintain its technical edge, which has provided us – and our customers – with crucial first mover advantage in highly competitive markets.

I'm sure they have done some preliminary research into this technology before allowing their name to be associated with it.

Brian