In the past, I’ve discussed some of the major threats to hydrogen cars in the future car marketplace. Such threats include electric vehicles, biofuel vehicles, solar cars and compressed air vehicles. And, liquid nitrogen (LN2) cars must also be added to the list.
The air we breathe is made up of 78-percent nitrogen, 21-percent oxygen and 1-percent of other gases. This means that if liquid nitrogen is used for fuel and released back into the environment, it also becomes a zero emissions alternative.
Just as the compression, liquefaction and cryogenic storage of hydrogen takes a great deal of energy for use in a vehicle such as the BMW Hydrogen 7 luxury automobile, so does this same process for nitrogen also take a lot of energy for use as a power source for vehicles. But, unlike hydrogen, nitrogen has primarily been used in turbine-type engines instead of internal combustion engines (ICE) or fuel cell vehicles.
On the safety side, nitrogen is mostly an inert gas that does not have the combustion properties of other gases such as hydrogen or oxygen. The compressed liquid nitrogen for turbine engines is heated using the ambient heat of the vehicle and as it expands, this turns the turbine, which supplies power to the wheels of the vehicle.
In 2000, the University of Washington created the LN2000, which was a converted mail delivery van that ran on liquid nitrogen. The 1984 Grumman-Olson Kubvan had a 15-hp, 5-cylinder air motor plus a preheater to deal with the nitrogen. The project has since been abandoned due to lack of funding.
In 1997, the University of North Texas (UNT) developed the CooLN2Car, which also ran off of cryogenic liquid nitrogen using an isothermal expansion engine. As of October 2006, the UNT Nitrogen Car Project was still moving forward according to the university as researchers are busy building a second-generation nitrogen-powered vehicle.
While the theory of a nitrogen economy does have many parallels with that of a hydrogen economy, there are also some serious shortcomings involved in using cryogenic nitrogen over other alternative fuels. The energy is takes to produce liquid nitrogen, its low energy density and its inertness can be seen as drawbacks compared to hydrogen, which is more flexible in its uses.
Hydrogen can be liquefied like nitrogen and used to turn a turbine, but it can also be used in a compressed gaseous state and burn inside an internal combustion engine or power a fuel cell as well. But, let’s not throw nitrogen cars out completely as they may have their uses in the future especially when a high degree of safety is necessary such as for trucks hauling flammable materials, or mining cars or other circumstances where a vehicle should not be able to start a greater fire in its surroundings.
The more alternative fuel options we have going forward the more likely it will be that one day soon, fossil fuels will be thing of the past and we will have moved on to more environmentally-friendly vehicles. That won’t be such a bad day now will it?