Tuesday 30 October, 2012. The Green Piece.
When we talk of ‘alternative fuel’ vehicles, we usually mean battery electric or hydrogen fuel cell or maybe biofuel-powered, but there is one alternative that might prove to be a more practical alternative-liquid air.
It’s not a new idea but one has been traditionally sidelined in favour of hydrogen because of the need to incorporate expensive and heavy, high pressure heat exchangers to re-gasify the liquid air or liquid nitrogen quickly.
But one UK firm, Dearman Engine Company is changing all that. It is something that only came to my attention through an article in The Economist (see story), but the company’s simple approach to a costly problem has long since caught the eye of academia and industry (I know I’ve been slow on this one).
The Dearman Engine Company as featured on the BBC
Garden shed solution
The Dearman Engine Company, established by Peter Dearman, a man who describes himself as a ‘garden shed inventor’ now counts the University of Leeds, the University of Brighton, BDO, Ricardo, Queen Mary University of London, Science & Technology Facilities and Loughborough University among its supporters. But what makes its technology so special and eye-catching?
Instead of using expensive heaters to heat the liquid fuel, the Dearman engine injects a mix of water and antifreeze (methanol) into the cylinder as the liquid air is drawn in, causing it to heat and expand rapidly—thereby forcing the piston down inside the cylinder and driving the engine. It is a lot cheaper and more efficient and more compact than using heat exchangers.
A liquid air car of this nature boasts many of the advantages combustion car; it’s quick to refuel, capital costs are around the same, maintenance and life expectancy are also comparable. While the process of turning liquid air back to a gas may not be as energy-packed as burning fossil fuels, its energy density is equal to that of advanced lithium ion batteries.
It could even be more affordable to own than an electric car, because of it doesn’t need expensive, heavy batteries. And because its manner of propulsion doesn’t result in waste heat, there is no need for heat-resistive parts, making it cheaper to kit out.
Tested and approved
Ricardo has already subjected the Dearman’s technology to a feasibility study concluding that “the technology is likely to compete with hydrogen fuel cell and battery electric systems in zero emission applications.”
So what next? A demonstration engine is scheduled to go into testing during mid 2013 and a proof-of-concept model has already been lab tested, proving to be more efficient than any previously built design for a liquid air engine. The engine’s inventor has already driven a car with an early prototype liquid air engine at more than 30mph.
Using liquid air, which largely consists of nitrogen, has other advantages too. Its only only tailpipe emission is cold air. Billions of litres of liquid air are used in each for a variety of industrial and medical purpose so exploring its use in the clean energy sector is a natural next step.
According to The Economis’ article, pure liquid nitrogen could be even better than liquid air, being denser than liquid air, it can store more energy per unit volume and therefore give a car greater range per tankful than air. Liquid nitrogen is a by-product of the industrial process for making liquid oxygen and because there is four times as much nitrogen as oxygen in air, there is inevitably plenty of the stuff. In the US that means that liquid nitrogen sells for a tenth of the price of milk.
Company video from the Dearman Engine Company
Liquid air or nitrogen fuels are also easier to store than their rival hydrogen, which is typically compressed for use in vehicles. As long as a tank is well insulated, liquid air can be stored at atmospheric pressure for a long time. Because liquid air boils at anything warmer than -196 C, it is quickly turned back to gas and will work in countries with extreme cold nearly as well as hotter countries.
Liquid air is not flammable either, unlike petrol and diesel and is classed as lower hazard than these fossil fuels as well as hydrogen and battery chemicals.
The technology could be used not just to power cars but also to store what is called ‘wrong time’ energy and help the energy sector make better use of renewables. Intermittent energy supplied from sources such as wind turbines and solar panels can be used to liquefy air, effectively storing the energy until it is needed.
While commercialisation may be a long way of, it looks like liquid air and the Dearman Engine Company could be one to watch in the near future.
Faye has been writing about cars and environmental issues since 2007. A suspected eco-warrior working on the corporate inside, Faye mainly likes the weird, quirky vehicles that show a distinct environmental advantage. Her ideal car has enough room to fit a bale of hay in the boot. When not working, she likes nothing better than to head out on her bicycle and explore the countryside.
Nitro-Turbodyne
Our company has developed a method that is more powerful than the method described in this article, much more efficient, and does not require water, antifreeze or any other medium to produce power for autos, lorries, generators, boats or remote locations. Our motor has only 1 moving part and is maintenance-free; does not require lubrication, cooling or anything other than liquid nitrogen to run indefinitely.
November 03, 2012