| Liquid Nitrogen Economy |
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Typically, the demise of the petroleum-age is presented as a catastrophic collapse. The Liquid Nitrogen Economy is a proposal to initiate an energy diversification, an alternative to the typical collapse scenario. DESCRIPTION Currently, most road vehicles are powered by Internal Combustion Engine s burning Fossil Fuel . If transportation is to be sustainable over the long term, the fuel must be replaced by something else produced by Renewable Energy . The replacement should not be thought of as an energy source; it is a means of transferring and concentrating energy, a "currency". Liquid nitrogen is generated by Cryogenic or Stirling Engine coolers that liquefy the main component of air, nitrogen (N2). The cooler can be powered by renewable generated electricity or through direct mechanical work from a Hydro or Wind Turbine s. Liquid nitrogen is distributed and stored in Insulated Containers . The insulation reduces heat flow into the stored nitrogen. Heat from the surrounding environment boils the liquid. Reducing inflowing heat reduces the loss of liquid nitrogen in storage. The requirements of storage prevent the use of pipelines as a means of transport. Since long-distance pipelines would be costly due the insulation requirements, it would be costly to use distant energy sources for production of liquid nitrogen. Petroleum reserves are typically a vast distance from consumption but can be transferred at ambient temperatures. Liquid nitrogen consumption is in essence production in reverse. The Stirling engine or cryogenic heat engine offers a way to power vehicles and a means to generate electricity. Liquid nitrogen can also serve as a direct coolant for Refrigerators , Electrical Equipment and Air Conditioning units. The consumption of liquid nitrogen is in effect boiling and returning the Nitrogen to the Atmosphere . POLITICAL ARGUMENT The adaptability of thermal-engines and a diverse means of production is likely to lead to the diversification, localization and stability of the energy market. Possible energy diversification includes the Hydrogen Economy , Solar and Biofuel alternatives. The dependence on the petroleum economy has a significant global influence. Petroleum reserves represent political and monetary power. Considerable effort is focused on managing a stable supply, shaping global politics. The environmental impact from the Carbon Dioxide discharge is currently unsustainable. Alternatives are a matter of necessity. CRITICISMS The approach has been criticized on the following grounds, which can also be seen as the engineering challenges that must be overcome. Cost of production Liquid nitrogen production is an energy-intensive process. Currently practical refrigeration plants producing a few tons/day of liquid nitrogen at about 50% of Carnot Efficiency J. Franz, C. A. Ordonez, A. Carlos, ''Cryogenic Heat Engines Made Using Electrocaloric Capacitors'', American Physical Society, Texas Section Fall Meeting, October 4-6, 2001 Fort Worth, Texas Meeting ID: TSF01, abstract #EC.009, 10/2001.. Energy density of liquid nitrogen Liquid nitrogen as an energy store has a low energy density. Liquid hydrocarbon fuels by comparison have a high energy density. A high energy density makes the logistics of transport and storage more convenient. Convenience is an important factor in consumer acceptance. The convenient storage of petroleum fuels combined with its low cost has lead to an unrivalled success. The maximum energy density that can be realised from liquid nitrogen at atmospheric pressure is 213 Watts-hours per kilogram(W-hr/kg). This compares with about 3,000 w-hr/kg for a gasoline Combustion Engine running at 28% thermal efficiency, 14 times the density of liquid nitrogen used at the Carnot efficiency C. Knowlen, A.T. Mattick, A.P. Bruckner and A. Hertzberg, "High Efficiency Conversion Systems for Liquid Nitrogen Automobiles" , Society of Automotive Engineers Inc, 1988.. For an isothermal expansion engine to have a range comparable to an internal combustion engine, a 350 litre onboard storage vessel is required . Add to that the fact the container would need to be insulated. A practical volume, but a noticeable increase over the typical 50 litre gasoline tank. The addition of more complex power cycles would reduce this requirement and help enable frost free operation. Frost formation Unlike internal combustion engines, using a cryogenic fuel require heat exchangers to warm and cool the working fluid. In a humid environment, frost formation will prevent heat flow and thus represents an engineering challenge. To prevent frost build up, multiple working fluids can be used. This adds topping cycles to ensure the heat exchanger does not fall below freezing. Additional heat exchangers, weight, complexity, efficiency loss, and expense, would be required to enable frost free operation . SEE ALSO
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