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

Where the Actionin Fuel Cells is TodayAllied SignalVolvoBallardDaimlerChryslerDetroit EdisonDuPontShellFordGeneral MotorsHondaMazdaGeorgetown UniversityCase Western Reserve UniversityLos Alamos National LaboratoryMotorolaPenn State UniversityPrinceton UniversityRolls-RoyceArgonne National LaboratorySanyoDAISSiemensBritish GasPlug PowerUniversity of MichiganTexas A&M UniversityARCOEpyxInternational Fuel CellsH-PowerEnergy PartnersHydrogen BurnerW.L. GoreA.D. LittleInstitute of Gas TechnologyVairexElectrochemGinerJet Propulsion LaboratoryToyotaUniversity of CaliforniaExxonWestinghouseRenault3MNissanBMWPSA Peugeot CitroënTexacoUniversity of FloridaTokyo Electric Power(This is just a partial list)HydrogenAnode (-)OxygenCarnot Cycle vs. Fuel CellsThe theoretical thermodynamic derivation of Carnot Cycle showsthat even under ideal conditions, a heat engine cannot convert allthe heat energy supplied to it into mechanical energy; some of theheat energy is rejected. In an internal combustion engine, the engineaccepts heat from a source at a high temperature (T 1 ), converts part ofthe energy into mechanical work and rejects the remainder to a heatsink at a low temperature (T 2 ). The greater the temperature differencebetween source and sink, the greater the efficiency,Maximum Efficiency = (T 1 – T 2 ) / T 1where the temperatures T 1 and T 2 are given in degrees Kelvin.Because fuel cells convert chemical energy directly to electrical energy,this process does not involve conversion of heat to mechanical energy.Therefore, fuel cell efficiencies can exceed the Carnot limit even whenoperating at relatively low temperatures, for example, 80°C.The Very BasicsCatalystElectronsProtonsCathode (+)WaterMembrane/Electrolyte• A fuel cell is an electrochemical energyconversion device. It is two to threetimes more efficient than an internalcombustion engine in converting fuelto power.• A fuel cell produces electricity, water,and heat using fuel and oxygen in theair.• Water is the only emission whenhydrogen is the fuel.As hydrogen flows into the fuel cell onthe anode side, a platinum catalyst facilitatesthe separation of the hydrogen gasinto electrons and protons (hydrogen ions). The hydrogen ions passthrough the membrane (the center of the fuel cell) and, again with thehelp of a platinum catalyst, combine with oxygen and electrons on thecathode side, producing water. The electrons, which cannot passthrough the membrane, flow from the anode to the cathode through anexternal circuit containing a motor or other electric load, which consumesthe power generated by the cell.The voltage from one single cell is about 0.7 volts – just about enoughfor a light bulb – much less a car. When the cells are stacked in series,the operating voltage increases to 0.7 volts multiplied by the numberof cells stacked.This document, and more, is available for download at Martin's Marine Engineering Page - www.dieselduck.net