Organic Rankine cycle power plants fueled with biomass as topping cycles in cogeneration scheme have been operated in Central Europe since 2000. These plants are usually situated nearby villages whose thermal and electrical energy demands are satisfied by the cogeneration plant in a distrit heating configuration. In this paper a technical and economical feasibility assessment of these plants is presented. Energy performance is analyzed for four typical organic fluids (two silicone oils, toluene and isopentane), all of them in subcritical and supercritical cycles with and without recuperator. Optimization of heat exchanger size is included in technical analysis. As bussiness model an Energy Service Company operation is assumed, selling thermal and electrical energy to a nearby village at competitive prices regarding the market in Spain. No subsidies are considered in electricity sale, so the Spanish average pool market price is considered. Size of the plant, cost of biomass and yearly operation time have been considered in economical analysis. From the technical analysis hexamethyldisiloxane (HMDSO) in recuperative cycles results the best choice in both subcritical and supercritical layouts, regarding its global behavior (harmful, reliability, . . . ). The economical assessment shows a lower profitability with supercritical cycles because of the fact that the increase in electrical efficiency implies the decrease of the useful heat, which is the main economical income to the cash flow. Size of the plant can be combined with fuel costs to achieve similar profitability (i.e. 1 MWe plant fueled with biomass purchased at 5.5 e/MWhth gives similar internal rate of return than 2 MWe plant fueled with biomass purchased at 15.5 e/MWhth). Yearly operation time varies from 2,750 hours (2 MWe plant fueled with biomass purchased at 5.5 e/MWhth) to 5,500 hours (1 MWe plant fueled with biomass purchased at 15.5 e/MWhth) to achieve internal rate of return of 5% with subcritical recuperative plants.
Directores: J.I. Linares, E. Arenas.
Autor: Maria Uris
Lugar: Aula de Seminarios

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