Ammonia could be used as fuel. Image: Wikipedia user Ben MillsEnlarge Photo
John Fleming and Tim Maxwell at Texas Tech University are developing a system to produce ammonia that can be installed in filling stations.
What are the benefits?
Rather than using hydrogen to power fuel cells and the associated high-pressure storage problems associated with this, Fleming and Maxwell would use water to produce hydrogen from electrolysis, and this is then combined with nitrogen from the air to produce ammonia.
The ammonia itself would then be burned in an internal combustion engine, but the burning process only releases water vapor and nitrogen, rather than the unburned hydrocarbons and other pollutants that internal combustion is normally associated with.
In theory, the ammonia is also simple and cheap to produce - enough so that it could be sold at 20 cents per gallon. Hydrogen and nitrogen are compressed at high pressure, and the mixture is then fed into a chamber containing an iron oxide catalyst, which creates ammonia. The mixture is then decompressed and cooled, then cooled again to a liquid form that can be collected and transported.
What are the downsides?
One of the stronger arguments against hydrogen as a fuel for either internal combustion or in a fuel cell is that although the gas is abundant, it's not particularly easy to extract.
Electrolysis tends to use more energy in producing hydrogen than you get from the resulting gas so it's an inefficient process. This means there's a net inefficiency before you even begin to produce the ammonia. Fleming and Maxwell claim to have avoided this scenario.
Like our other favorite liquid, oil, an ammonia spill could also be hazardous to the environment, particularly aquatic life, so particular caution would be needed to avoid environmental disasters.
The pair are working on an engine that would run purely on ammonia, known as the Linear Electric Internal Combustion engine. Burning an air and ammonia mixture moves a piston backwards and forwards, the reciprocal motion drives a generator, and the electricity produced is used to drive the car.
It's all very exciting, but for the time being we remain unconvinced.
We've seen so many different ideas for car propulsion come and go and we still use only a handful of proven, tried and tested methods. We look forward to seeing a working prototype vehicle from Maxwell and Fleming to prove us wrong...