Another zero-emissions powerplant emerges - the Dearman Engine runs on liquid air


January 24, 2012

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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.

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


Well, this is just about perfect! The hotter the world gets, the more efficient my car will be. Global warming for better fuel economy. Don\'t you love it?

Facebook User

Do I need a really cold freezer in my car to use this?.. or is the tank so efficient at insulation, that it can keep the gas at minus 160 degrees?

Paul Hutchinson


Zesbinder Sody

As with Electric Vehicles, these devices are only \"emission free\" at the point of use.

Somewhere energy (probably producing emissions) is required to manufacture the liquid air.

7 out of 10 - Must try harder.


7 out of 10 is generous, all we need now is an infrastructure that can supply liquid air all over the world and we are sorted! How excellent is the energy density when you factor in all the energy required to manufacture/transport/store/distribute liquid air? And it is really only a compressed air engine just like the ones in the biscuit factories in Reading 100 years ago. Great idea, but not a solution to anything.

David Wedge

@RJB - was going to ask a similar question - what is the energy cost of the full cycle? And what would be the proposed energy source for the creation of liquid air? I\'d presume though that this could easily be an electrical and renewable source, so I think you are being a bit harsh. My other question is that the graph shows the Dearman Engine to have a lot less energy density than Li-ion, which is not what it says in the text.

(Your comment re EVs ignores the greater efficiency of electric motors over internal combustion, so even if a fossil fuel source is used for the electricity they are still better than petrol/diesel in overall emmissions).


re; Paul Hutchinson

Buy a good thermos and see how long it will keep your coffee hot. same principal.


The early stage we still need current technology to produce liquid air. As it improve, all engine including electric generator could run using this engine. I wonder, will this technology flourishing the common market without the giant petroleum interferent? I doubt.


BRILLIANT! And a \"gas station\" could compress air to a liquid on site making transport of the liquid air unnecessary.

Wonder what the range would be for a volume comparable to a twenty gallon tank of gasoline?


It will need a giant flame to thaw out the rock hard ice that will continually envelope the engine.

vidyadhara buddhiraju

The terms used in this article seem to reflect commerical understanding only, no understanding for the technical efficiency of things the real concern should be with. It very short sighted to say that cryogenic liquids are produced allready all over the country and then forgetting to mention that this does not make up a distribustion network for customers. \"No range axiety\" is laughable as trust or lack of anxiety comes from the availability and reliability of the distribution network and has nothing to do with the cars energy supply as such. You would have range axiety if there was a petrol station every 1000 miles and your car is said by the manufacturer to be good for 1200 miles, but A) the manufacturer got this number from an artifical stadardized test that he is required to do by law and has nothing to do with reality as such and B) is then slightly polished for marketing purposes. Furthermore tank meter would show the tank to be empty at the 975 miles mark eventhough the tank holds another gallon and you are likely to reach your target as long as the road is not uphill .... the over simplification is mind boggling. - however - I can see that this technology has potential, a few issues though ... where does the heat come from to heat the car in the winter ? what impact have wheather conditions on the engine performance ? what range of liquits can be used ? what temperatures do they need to stay in in order to be liquid ? what happens when the tank takes a hit in an accident and the liquid is spilled ? And finally, what sources for this liquid/s do exsist ? liquid air is certainly an option but best only used when produced by access wind energy systems that have been developed in the UK as well ... Many questions left to answer ... time will tell if the issues can be overcome...

Dany Ehrenbrink

Hmm, so where does the heat exchange fluid get its heat from? Must require a pretty big heat exchanger somewhere else. Anyone done the math on how big and efficient that exchanger needs to be? There is a very large amount of energy required to change air states. How well would this engine run in say, Canada in February/March? And where is the heat coming from to keep the passengers comfortable? Of course air conditioning wouldn\'t be a problem? :) Would also have to make sure absolutely no water got into the engine.

Ken Waldron

Think about what it is hinting at replacing and you will find out that the cycle environmental costs are a lot less than using batteries and the production and disposal costs that the it entails.

The issue with me is how good will it be in cars and trucks in terms of power (torque) and range (What is a typical car\'s tank hold and how far does it take me vs the albeit limited range of the battery powered alternative.

The bonus is the lack of exotic and rare metals required and the conventional approach.

I am looking forward to reading more about this as I am not sure how good it is yet.



Do not be so quick to find the flaws in this system. I have thought much about using compressed air as a fuel source for the future. In the future we need some sort of low cost, environmentally friendly, synthetically produced energy carrier. I had previously thought it would be the fuel of the universe, hydrogen, but compressed air does not have the potential, explosive danger of hydrogen however hydrogen, especially with a fuel cell for in-car electricity production, has a high power to weight density which puts it on the same level as compressed air. Remember this is for the future, where renewable energy powers the world.

Yusuf Khan

One of those \"great potential\" ideas, not likely to go very far. For example, how do you keep the liquid air in your car\'s fuel tank supercool? Surely, as the tank temperature moves closer to ambient, the liquid air would begin to expand. A release valve on the tank would be necessary to compensate for the expansion. So you lose \"fuel\" even when the vehicle is idle. Insulating a tank to the point of just slowing down this process would be costly and would increase overall vehicle mass - decreasing efficiency. Or the tank could be built to withstand extreme pressure, resulting in more weight. The description above sadly lacks many technical details.

This might be a suitable replacement for short range gas powered vehicles, such as forklifts. Provided that the vehicles never stray too far from the supercool fuel source, and the capital cost is not greater than an existing system.

And, like hydrogen, supercool air is not a primary energy source, only an energy carrier. Fossil or nuclear would most likely provide the primary energy, at least for the forseeable future.

Conor Brannigan

This system needs a sterling cycle engine in the heat exchanger and the hotter that you can get the gas before releasing it the better.


What kind of mileage could a typical car get in say miles per cu ft of propellant?


I am not convinced that heating the cryogenic liquid in the engine is best. A flash boiler pneumatic system might work better. I would also want rooftop solar-thermal collector and a grantedly complicated brake system that holds the liquid cooled disk stationary and spines the pads would be a nice touch.

ps. Don\'t leave the cursor on the post comment box and reach blindly for the mouse.


I hope that this engine does not emit nanoparticles. That is what is about to kill the internal combustion engine and humans

Stewart Mitchell

I am me too concerned about the heat exchange around the engine: how much heat do you need to create an acceptable energy difference? Will the engine work at -20 degrees? How much energy will be lost in heating the heat exchange fluid? How much energy will be lost in heating the interior? I can see that working in hot countries, but not in colder countries where most of the time the occupants of the cars need heat.

Also, even if the \"fuel\" tank is well insulated, there will be lost air. How much time does it take to empty the tank? What if you do not use the car for a week and you have to be towed to the next fuel station cause you don\'t have cryogenic air anymore? And forget carrying the cold air in a portable tank like we do now with gasoline. Much too cold.

A quick search lead me to a wikipedia article (no sources, take that as it is) that says the thing was already done in 1902. They tell about doing 64 km at 19 km/hr while using 68 liters of cold air... Not very efficient, but technologies have evolved a lot since that time.

This idea sounds like pie in the sky to me. The energy required to chill air to that low temperature will be expensive. Then there is the issue of being forced to either maintain that low temperature or vent the product and waste it. The so-called engine to handle this would really be more like a transmission in that it would simply take stored energy to power the car. Jim Sadler

I don\'t think that the thermodynamics are on our side here. The heat of vaporization of liquid air is about 200 kJ/kg. The heat of combustion of gasoline is 47000 kJ/kg, 235x higher.

If my car get 360 miles per tank, an equivalent Dearman engine would have a range of less than 2 miles. Sounds good for the golf course, but not enough for a commute--unless you have an on-board gasoline-fueled compressor to make air while you are driving!


It runs on coal, which burns at a power plant upwind from your house. Well, at least it\'s a change from the usual HOT air these dreamers spout.

Captain Obvious

And, when that supercooled air expands to standard atmospheric pressure doesn\'t Charles\' Law expect it to cool even further? What does that say for operation in humid areas? I know steam will flash to like 1700x the volume, but we\'re not dealing with water here. Just wondering...


re; Conor Brannigan

There is a lot of cheep, light, and efficient insulation out there. I would use a vacuum bottle glued into place with AB foam.


re; Kradak

In your ICE it is expanding a gas, this boils a liquid. Your numbers are way off.


Most all these \"O\" emission concepts go against the \"already-in-progress\" search for oil and natural gas that is being steam-rolled by our consumptive economy of scale, our demand, and the oil corporations that have our foot on their throttle. But like a martial artist that uses others energy to gain control- lets go with it! If we are compressing air to to the pressures necessary to liquify it, why not use that same energy to compress the abundance of natural gas (CNG methane) as an efficient TEMPORARY more efficient transition technology that is already useable in current IC engines. Next, At about 3500 PSI, we could use this (already proven safe compared to liquid gasoline)compressed gas technology as the pressure to run (one of many currently built efficient) air driven motors. The exhaust of this compressed gas \"air motor\" is still pure methane (now at STP) that gas can be burned in an auxiliary on-board IC engine- thus extending vehicle range by a large percentage. Next technology phased in- would be to convert the methane catalyticilly into electricity for the most efficient use of that fossil fuel- as its byproducts are now only water vapor and free electrons (+ small amount of pure carbon that will be used in the nano-scale building materials of the future as well as purify everything we eat). Silicon Valley is running now catalyst methane-to electricity technology to run their brick-and-mortar operations.. The future will be a variety of technical transition to meet the scale of energy needs, and become more efficient as we go. Each will have its place in time, and is a valuable part of the whole picture. I do not see any single panacea. All have worthy merit. Great stuff!


Mark the words: combustion to produce energy (read: electricity) will be over by 2020 ! However efficient could be, it is a dead end.

Let\'s concentrzte our energy to produce electricity with zero emission, then we can utilize engines (I mean: motors:) to produce work, be it transport or other...

Just my two cents..


Now I\'m not against experimentation at all, but we need to keep things like this in perspective. We have various laws of physics and chemistry and they just can\'t be ignored without dire consequences ensuing. To promote stuff like this as \"just around the corner, all we need is a little bit more money to perfect it\" is disingenuous at best. There was a guy who was making irrational claims about his VaporDyne engine in the 60s and 70s, and it never worked out. He made a prototype of the engine, but it wasn\'t nearly as efficient as he claimed it to be. He didn\'t understand that horsepower was a combination of torque and speed, so it\'s impossible to increase Hp while decreasing RPM, as he claimed this vapor engine could do. When people are not fully educated in the laws of physics, like my dad,unfortunately, they come up with weird ideas about some device that they think will work a certain way just because they IMAGINE it will work that way. Not without a healthy dose of magic occurring it won\'t. So they keep on trying to tweak it here and there, hoping that next week they\'ll have it figured out and they never will because they\'re ignoring the basic laws that cannot be worked around. If that was able to be done, we\'d have folding up cars like in the Jetsons.


Expanded Viewpoint

do you ever think how a deoderant can keeps it\'s propellent liquid or a oxy accetalene tank does the same thing - that solves the storage question. have you ever seen a forklift with a big propane tank on the back - considered safe as anything else. And last rant, I work in a factory enviroment and air is the most efficient way to make things move up and down etc.

Steve Rock

hello. trying to compare the combustion force between maximizing super boiling water and electrically ignited gasoline may require a new plumb altitude rising crankshaft.


The mechanics of this engine / power source are interesting. The way that I read the article, this sounds similar to a two stroke cycle (power / exhaust), so it will give twice as much power for the same size capacity engine as a four stroke (approximately).

I\'d assume that there would only be a simple exhaust with no cat or other emissions controls required, perhaps just a muffler to reduce the noise. Similarly, there would be no need for a cooling system for the engine, so it could be air (heated ? / cooled?), although the heat exchange system may be similar in nature (ie to heat up the engine, rather than cool it down).

No emissions control systems, (no harmful emissions!), the air conditioning is not using ozone depleting gases, no / little fuel being used, no cooling system(?), so it could be a lot simpler as a power source.

Put a turbine or two into the exhaust to recover some more energy to power the heat exchange, electrics etc. Or, use a concept similar to a turbocharger to heat up the engine block (ie currently a turbo needs an intercooler to cool down the air intake on an ICE, why not use this effect as a heater for the engine block with the existing cooling system on an engine, and just exhaust the heated air into the existing exhaust, without going through the engine itself).

There has also been some work done on air recovery devices (exhaust air recovery for air compressors), so one of the turbines could be used to recover some of the air and recompress it to extend range (makes the engine more complex though).

One issue that I wouldn\'t mind some more detail on - when the engine isn\'t in power mode (eg \'throttle\' closed), the engine is still connected to the transmission and will be spinning; what is going into and out of the engine, as I assume that we are talking about only injecting the cryogenic fluid, not mixing it with air. In the mode that I talk about, is standard air being introduced or how is this situation being dealt with?


I told you - they are going to sell us an air soon :)

Vladimir Popov

LOL - yeah - first, they tax us for breathing out, now they\'re selling us air as well!

This idea\'s dead before it begins though. Nobody\'s going to be happy about: A) Their tank of gas evaporating when unused for a few days, and B) Instantaneous death in minor accidents

Extreme cold is just as bad as extreme heat. Both/either, for example, is used in surgery to deliberatly kill things (eg: warts).

In case nobody\'s noticed, the fun police no longer allow anything that might ever hurt anyone. If we were not already doing it, the very idea of movoing around fast with combustible liquids in tanks would never be approved today. Or smoking. Or alcohol. Good ideas are literally against the law this century. Heck - if you take the insane patent system into account, pretty much everything is against the law...


razif, gotta agree, look at what GM did to the mass transit system mid last century in Los Angeles USA bought it, broke it and came out with the slogan see the world today in your Chevrolet

Bill Bennett

You wouldn\'t even need a \"Gas Station\" with this type of technology. It would be similar to Honda\'s Natural gas cars, where you can have a refueling station installed in your own garage! You just need an air compressor which would continuously compress air into a liquid, and store it in some kind of container in your own garage. I\'m sure there will be safety features in case of an accident. After all, air is not as combustible as, say, gasoline or hydrogen or natural gas.


Most gases behave closely enough to the ideal gas law that we can apply those principles here. PV=nRT. The main problem is that the ideal gas law is only useful for gases at low pressure and high temperature. The reason for this is because the ideal gas law assumes that the gas molecules have no volume and no attractive forces (relatively negligible). This isn\'t true at high pressures because the molecules are forced closer together which causes the relative volume and attractive forces to have an effect. Johannes van der Waals accounted for these with P = (nRT)/(V-nb) - ([n^2]a)/(V^2). Regardless of which equation we choose, we can see that pressure (P) has an inverse relationship with temperature (T). Thus, the pressure needed to liquidize air (nitrogen/oxygen) will also keep it at a certain temperature.


This is very interesting: I never thought about current ICE engine actually do NOT rely at all on combustion gas TEMPERATURE! Actually, high temperatures reached by gas causes TROUBLE, and we have indeed to an heater to dissipate the exceeding heat! What really powers an ICE is just the expansion of the gas, which is DUE to temperature increase, which is due to petrol/air mix getting burnt.

So, the question is: how much pressure can cool air produce when passing from -170°C to 23°C? Is it enough to power a vehicle?

Second question: can air be kept liquid just by pressure, or does it require also cooling?

Luca Sentini

You don\'t liquify a gas solely by compressing it. You cool it under moderate pressure. There\'s a very commonly used technology that takes CO2 as a gas at ambient temperature and about 200 psi, cools it in an insulated vessel to -70C using commonly available refrigeration equipment and stores it as a liquid at this pressure. It\'s used in cooling systems for thermal cycling and testing. Likeqwise, liquid nitrogen and liquid CO2 are commonly stored in dewars (insulated tanks) at very low pressures. They are vented constantly as the liquid warms, but the loss of gas is really negligible compared to the volume of liquid in the tank. So, home production of liquid air is certainly feasable for moderate expense. The energy to run the compressor and cooler would come from the power grid or local solar or other renewable source.

Capn Mike

re; christopher

A. Properly insulated you will loose less than one percent per day without active cooling.

B. to get instant death the fuel tank would have to burst like a balloon, not dribble like a Pinto\'s after an accident.

You seem to be an officer in good standing in the Fun Police.


This has more potential in industry - like forklifts that now run on propane - generally indoors.

Boiling point for liquid air is minus 319 degrees F - and in answer to the question posed regarding the temperature of the heat exchange fluid see:

The article is correct that cryogenic fluids are generally available, but I don\'t see this as practical for individual autos, but might work for fleet use.

Mike Siesel

Using natural gas to compress the oxygen is the way to go. The heat generated in that activity can also be harvested for other purposes and for general heating purposes.


cool! now we just need to get pv cells on people\'s roofs so they can make their own fuel for household and transport use!


Compressed air motors have been around for a long time. I wonder what break through makes them a good motor for a car? Is it the new extra long air hoses or is it all the people smoking dope here? A few of you have your feet on the ground the rest of just keep puffing away, might try just clean air for change.


Linking 2 points mentioned before, could any leakage from the tank be used to power either a battery for on-board electronics, a pre heater for the heat exchange fluid (ready for next use) or a cooling system? (i.e. the more leakage the at any time the more the system is cooled) their would be some overall loss but it would effectively feed back to reduce this regardless of external temperature,

Weather the system its self would work is well beyond my level or physics/engineering, but some of the side issues raised sound relatively easy to tackle, ANY new fuel will have an initial logistics problem. In this case the potential for home fuel generation and/or an on board compressor that could be plugged in, would mean it was less restricted until the new distribution new work was in place. And if local large scale generation was possible (a fuel station generating its own compressed air) this would again simplify the issue.

On the \"would it run in winter\", even -20 is 140 degrees warmer than the -160 or less that\'s being discussed here. Yes it would need some adaptation and might be limited in these environments, but the same applies to traditional fossil fuel engines.

Nathaniel Simpson

re; sinan

Not unless the green fascists get out of the way of nuclear power.


I see very little innovation here, the engine runs on the same principal as an air drill or any other compressed air motor, so no innovation there.

And then compressing gas into a liquid is nothing new.

you cannot claim ZERO emission unless you have cracked the issue of how to rapidly cool the air without emissions, that is the only area of this that could be labelled a true innovation and it is being totally ignored.

Electricity is currently the closest thing to possible zero emission power using solar, wind or hydro for initial generation.

I for one hope that we find a solution to no longer needing fossil fuels soon, but hate it when the world wastes its time on scam artists who only sell a small portion of the picture, This is NOT a ZERO emission alternative, according to the information you provide, please state otherwise or revise your title and STOP spreading miss information.


Come to this a little late.... I was looking at using Liquid Oxygen for powering an ICE eliminating the dreaded NOx (which causes most of the visible pollution from combustion.)

I laugh at many of the comments as they are very funny... The tooing-and-froing provides great entertainment.

Ok Liquid Air, why not use it in the engine, and add petrol to the process, making benefit of the expansion of the air, and adding combustion to produce the usable power, think of it as super-supercharging.... There may be a benefit as the engine will be able to outsource the compression phase to the power grid at higher efficiency in a distributed point of sale network.

Or another step, fill up on Liquid Oxygen (Locally produced from Grid Power) and Liquid Petrol (or Gas) at the Filler point (station, garage or whatever), eliminate Nitrogen, allowing ultra-lean-burning engines, (the limitation on lean burn isn't "technology" but the increased production of NOx at high temperatures.... ok need technology) now we can run ICE's (including (properly matched to load) turbines) at Much higher efficiencies due to thermodynamic increases in efficiency as the temperature increases.... The materials problems with high temperatures have largely been overcome (for a price, we will need mono-crystalline titanium or ceramic poppet valves / power turbine wheels), but that is no real issue, is it)....

(As a side note, people think that turbines are terribly inefficient, but that is only because they must be operated at a very narrow rated power for decent efficiency, remembering that we no-longer need to have a compressor (thereby losing the compression load) if there is liquid Oxygen available, only a power turbine... and a car is better run as a "hybrid" series electric anyhow... ...)

If we still need to add MASS to the engine for expansion water injection would allow this to be accomplished with low dissolved Nitrogen the NOx problem will still be minimised... As the water goes supercritical in the combustion chamber that will allow more than enough expansion..

damn.. We know that most people's daily commute (the world over) can be done on electric power, and that is with existing batteries, so an ICE is only needed to generate mean power output to act as a range-extender or battery charger... While the grid charger the car overnight...

WE know none of these Ideas will be worth a damn until big P and A decide that they have enough value from their existing investments...

For increased efficiency catch the train / bus (a full train has a good efficiency, while normal train occupancy (average) is worse than everyone driving a Range-Rover..... (I prefer to ride a bike, if a bus would do, I can usually get there quicker on a bicycle.) lol... End of rant.


This is a truly promising engine. It can help solve the problem of storing excess electricity produced by wind generators, solar panels, wave generators, etc. at th wrong time. The electricity which produced at a time when it is not needed, e.g nighttime, can be used to freeze air into liquid. This can be used to power cars, buses, trains and why not, generators to produce electricity when it is needed. e.g. daytime. Last year, within the activities of The Joint Group of professional Civil and Mechanical Engineers, (members of I.C.E. and I.Mech.E. UK), I gave a very successful lecture titled "Gas as fuel for motor vehicles". In this lecture I mostly referred to LPG (liquid petroleum gas) and both CNG (compressed natural gas) and LNG (liquefied natural gas) powered vehicles and explained the various engines available, which use gas as fuel. Gas only engines, Dual-Fuel engines (petrol-gas) or (diesel-gas) were described in detail. Also the conversions available for existing engines, the conversion process, safety measures, etc. I have been invited to repeat the lecture next year for different group. I suppose I must include also the Dearman engine. After all air is a gas too.

A. Simonis
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