Some CHP Options for Wood-Fired Fuel Cells

The possibility of integrating biomass gasifiers withfuel cells has already been explored and shown to offer amethod for using renewable energy to generate electricity at asmall scale. A preliminary study of applying such a system foruse in an isolated community and for several selected buildingshas been made and the results of these studies reported earlier.In this study wood gasification integrated with fuelcell (WGIFC) systems in CHP configurations for five buildingsystems with different energy demand profiles, are assessed.These are a hospital, a hotel, a leisure centre, a multi-residentialcommunity and a university hall of residence. Heat andelectricity use profiles for typical examples of these buildingswere obtained and the WGIFC system scaled to the powerdemand. Detailed technical, environmental and economicanalyses of each version are made, using the ECLIPSE processsimulation package. Various factors influencing the economicviability of each application are examined and a sensitivityanalysis for each system produced.The WGIFC system was modelled for two differenttypes of fuel cell, the Molten Carbonate and the PhosphoricAcid. In each case an oxygen-fired gasification system isproposed, in order to eliminate the need for a methanereformer.Technical, environmental and economic analyses of eachversion were made, using ECLIPSE. Since fuel cell lifetimesare not yet precisely known, economics for a range of fuel celllifetimes have been produced.While the wood-fired Phosphoric Acid Fuel Cell(WFPAFC) system was found to have low electrical efficiency(13 – 16%), the wood-fired Molten Carbonate Fuel Cell(WFMCFC) system was found to be quite efficient forelectricity generation (24 to 27%). Much of the waste heatcould be recovered for the WFPAFC, so that the overallefficiency was 64 to 67%, and some waste heat, but potentiallyof higher grade, could be recovered by the WFMCFC to givean overall energy efficiency of 60 to 63%. The capital costs ofboth systems are still expected to be very high, but theexamination of wood fuel prices, fuel cell costs, fuel celllifetime and waste heat selling prices on the break-even sellingprice for electricity, as well as comparative sensitivity analyses,can help identify which other factors would have the mainimpacts on the system economics.