Energy System with Enzyme Decomposition for a Fuel-Cell Electric Vehicle

摘要

Fuel without carbon is essential effective in preventing global warming by carbon dioxide. Hydrogen has no carbon and can be made also from the resources such as nuclear energy or renewable energies. However hydrogen is lack of portability for automobiles because of its difficulty in liquefying. Ammonia also has an advantage in terms of global warming because of carbon-free fuel. A hydrogen generation system fueled with ammonia from urea for a fuel-cell electric vehicle is described in this paper. In ammonia, the handling must be careful of safety specifically because toxicity of ammonia affects a human body and a fuel cell. On the other hand, urea can be easily changed into ammonia and dealt with safety. The license for handling of urea is unnecessary, and there are also achievements as a NO_x reducing agent for diesel engines. The authors have proposed urea as a hydrogen carrier via ammonia. Urea is white, odorless, harmless and broadly used with moisturizers such as cosmetics, medical supplies, manure, etc., as familiar applications. Urea of 20 kg can be estimated to operate a fuel cell of 1.2 kW for about 47 hours. Urease was used as an enzyme to produce ammonia from urea for reforming at low temperatures. The experimental results have shown about 64 times of ammonia generation by the urease at 60°C. The optimum temperatures and the optimum pH have been also investigated in the experiments. The authors would like to develop the new energy generation system for fuel-cell electric vehicles.