Fuel Cells - Green Power - Martin's Marine Engineering Page

Wood Coal OilNaturalGasHydrogenHydrogen As a FuelHydrogen is the most attractive fuel for fuel cells — having excellentelectrochemical reactivity, providing adequate levels of power densityin a hydrogen /air system for automobile propulsion, as well as having zeroemissions characteristics.CHC=CarbonH=HydrogenTrends in energy use: Hydrogen-to-Carbonratio increases as we become less dependenton carbon-based fuels.(Courtesy: “Wired” 10/97)Historically, the trend in energy use indicates a slow transition from fuelswith high carbon content, beginning with wood, to fuels with more hydrogen.Fossil fuels release varying quantities of carbon dioxide into theatmosphere — coal having the highest carbon content, then petroleum, andfinally natural gas — the lowest carbon dioxide emitter per thermal unit.Hydrogen obviously releases no carbon dioxide emissions when burned.Hydrogen (H 2) is the most abundant element in the universe, althoughpractically all of it is found in combination with other elements, for example,water (H 2O), or fossil fuels such as natural gas (CH 4). Therefore,hydrogen must be manufactured from either fossil fuels or water before itcan be used as a fuel. Today, approximately 95% of all hydrogen is producedby “steam reforming” of natural gas, the most energy-efficient, large-scalemethod of production. Carbon dioxide (CO 2) is a by-product of thisreaction.CH 4 + 2H 2 O ➔ 4H 2 + CO 2Hydrogen can also be produced by gasification of carbon containing materialssuch as coal — although this method also produces large amounts ofcarbon dioxide as a by-product. Electrolysis of water generates hydrogenand oxygen.H 2 O ➔ H 2 + 1/2O 2The electricity required to electrolyze the water could be generated fromeither fossil fuel combustion or from renewable sources such as hydropower,solar energy or wind energy. In the longer term, hydrogengeneration could be based on photobiological or photochemical methods.While there is an existing manufacturing, distribution, and storage infrastructureof hydrogen, it is limited. An expanded system would be required ifhydrogen fuel were to be used for automotive and utility applications.In 1809, an amateur inventorsubmitted a patent for this hydrogen car.This document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net