While you don’t hear much talk about “liquid nitrogen vehicles”, you may have heard the phrase “liquid nitrogen economy.” It’s kind of a confusing phrase.

What “economy” refers to here is not about a system of money to be used, a system of producing and distributing wealth but, rather, refers to the potential of a different fuel system (e.g. liquid nitrogen, hydrogen, vegetable oil, solar power) to replace fossil fuels in our economy.

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Proponents of this hypothetical system believe that liquid nitrogen fuel, rather than hydrogen, is the most viable alternative to our current system of energy and transport, which is based on petroleum.

Why do proponents believe this? Because the air we breathe is made up of 78% nitrogen, while hydrogen itself is not an energy source but, rather, an energy carrier. Therefore, energy must be expended to get the energy from hydrogen.

Not only that, but hydrogen must be compressed or liquefied to be used as a fuel. It turns out that, after all the energy required to do this, 80% of the energy created is wasted, which is not a practical use of energy.

Unfortunately, even though nitrogen is everywhere, there are a number of significant downsides in turning to liquid nitrogen as our primary energy source as well.

Producing liquid nitrogen is also an energy-intensive process. Also, because liquid nitrogen has low energy density, a lot more of it has to be created, transported and stored compared to petroleum, or even hydrogen.

Since liquid nitrogen must be kept in a cryogenic state, heat exchangers have to be used to both warm and cool the liquid nitrogen, depending on the climate. To keep an engine frost free requires more equipment, more weight, and loss of energy.

Then there’s the safety issue. Should a nitrogen car be kept in a poorly ventilated space and, as can happen, the nitrogen leaks off, it could prove fatal.

There are many alternative fuels being researched and developed, and someday one will be found to replace petroleum. Whether it will be liquid petroleum or some other fuel source remains to be seen.