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POWER PRODUCTION FROM RENEWABLE ENERGY AY 2018-19 4th February 2019 Prof. Silva Time: 1,5 hours Instructions for the examination: 1) Clearly indicate your name on all the sheets you will deliver. 2) The score refers to exercises done in a comprehensive manner with exact numerical results. Numerical results correct but not accompa- nied by explanations will not be taken into account. The final score will be normalized according to the average results. 3) Answer briefly and clearly only to the asked questions. Calculations and explanations which do not respond to the questions will not be considered for evaluation even if correct. 4) Talking with colleagues and / or cheating will cause the cancellation of the exam. 5) All the needed data for the resolution of exercises lies on this paper. It’s NOT ALLOWED to use material other than this (e.g. books, clipboard etc.) Exercise 1 (16 points) Consider a direct steam cycle with total condensation (Tcond=40°C) fed by a liquid dominant geothermal source having a temperature of 200°C and enthalpy of 2100 kJ/kg. Before entering the turbine the geothermal fluid is heated up to 400°C (enthalpy 3255.7 kJ/kg) by means of a biomass boiler in order to obtain a mechanical power at the turbine shaft of 30 MW (total auxiliary consumption of the cycle 2 MW, organic-electric efficiency of the steam turbine 96%) . Considering a second law efficiency of the cycle equal to 44%, evaluated with respect to a constant temperature heat source at the maximum steam temperature, an ambient temperature of 15°C and a reinjection temperature equal to that of condensation, (i) determine the mass flow rate of the geothermal source (2 points). The biomass boiler is fed by wood chips having a relative humidity of 35% and LHV dry basis of 18 MJ/kg…