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August 14, 2022

Nitrogen may be new eco-friendly fuel for cars

By MICHAEL YAMAKAWA | November 1, 2012

If you’re lucky and your hometown is Los Angeles, you may have seen the crimson-colored, Honda FCX Clarity or silver Mercedes-Bentz F-cell station wagons on the street as owners drive by smugly, feeling great that the only emission coming out of their car is water.

The drivers also get satisfaction from not worrying about “range anxiety,” a problem which traditionally plagues battery-powered electric car owners. Both the Honda and Mercedes models have ranges from 190 to 240 miles, which is comparable to typical petrol cars. However, after enjoying their pleasant, environmentally-friendly cruise, the drivers come back to reality with only five refueling stations located in Los Angeles.

While fuel-cell vehicles are a very effective solution to emission problems, there is a dearth of refueling facilities, due to the exorbitant cost of the production, distribution, and storage of hydrogen. To make fuel cells function, the hydrogen must be almost 100% pure, which in itself is very difficult to manage, ruling out many of the cheaper ways to make hydrogen. Furthermore, since hydrogen is the smallest molecule, it leaks through most materials, causing corrosion. This necessitates facilities to provide special linings for their tanks and pipelines. Surprisingly, hydrogen engines contribute their own share of greenhouse gases as well, since the electricity used to produce it is imported from coal-fired stations.

However, a recent breakthrough by Peter Dearman, a British engineer, has suggested a possible solution to efficient, clean motoring. He proposed an engine that utilizes liquid nitrogen.

Air was first liquefied in 1883 by compression and cooling. The process of producing liquid air yields 1.4 liters of liquid from 1000 liters of air. If liquid air is exposed to room temperature again, it suddenly boils and expands back to gas. In fact, it expands 700-fold, providing the work necessary to operate a piston engine.

On the other hand, liquefied nitrogen — which constitutes 78 percent of air — stores even more energy per unit volume, making it slightly denser than air. In other words, with the same amount of fuel, liquid nitrogen can provide energy for a longer distance than liquid air can.

Since liquid nitrogen is maintained at a cooled environment, engines do not have to manage the same high temperatures as conventional engines, allowing pieces to be produced with cheaper materials like plastic. Nitrogen engines are therefore a lot lighter than the engine of an electric vehicle, and can sell for about half the price. In fact, liquid nitrogen can sell for a tenth of the price of milk in America. Fortunately, liquid nitrogen is a by-product of the process of producing liquid oxygen, allowing facilities to capitalize on the surplus of liquid nitrogen being produced in the industry.

Dearman’s recent invention adds water and methanol — a type of antifreeze — into the cylinder, allowing liquid nitrogen to properly channel through the engine. This lets pistons compress without adding cumbersome engine parts that augment the overall price. The Institution of Mechanical Engineers in London, the leading standard-setting and registration body for engine production, is currently establishing a work group of engineers, academics, government officials, and other industry leaders to advance this technology.

It’s a good thing that Honda and Mercedes only distributed 200 and 70 models of their cars, respectively, as the future of hydrogen fuel-cell cars seem to be less and less auspicious. Who would have thought that the air we breathe could be the solution to the motoring problems that have plagued our environment and automobile industry for so long?

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