Automotive

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

Another zero-emissions powerpl...
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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."

49 comments
Paul Hutchinson
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?
Zesbinder Sody
Cool
RJB
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.
David Wedge
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.
Techjunkie88
@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).
Slowburn
re; Paul Hutchinson Buy a good thermos and see how long it will keep your coffee hot. same principal.
razif
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.
Dany Ehrenbrink
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...
Ken Waldron
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.
Toeknee
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. Toe-Knee