ES220620 practical test

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POWER PRODUCTION FROM RENEWABLE ENERGY AY 2021-22 20th June 2022 Prof. Silva Time: 1,5 hours Instructions for the examination: 1) Clearly indicate your name on all the files you will deliver. 2) The score refers to exercises done in a comprehensive manner with exact numerical results. Numerical results correct but not accompanied by explanations will not be taken into account. The final score can be normalized according to the average results. 3) Talking with colleagues and / or cheating will cause the cancellation of the exam. 4) All the needed data for the resolution of exercises lies on this paper. It is NOT ALLOWED to use material other than this (e.g. books, clipboard etc.). Exercise 1 (16 points) A geothermal source has the following characteristics at the outlet of the well: pressure 15 bar, vapor fraction 85%, mass flowrate 13 kg/s. Draw the power plant lay -out in a configuration without the atmospheric vessel (1 point) and determine the net power output (4 points), considering a condensing pressure of 0.09 bar and assuming a steam turbine isentropic efficiency of 87% and a generator organic-electric efficiency of 97.5%. Calculate the net electric efficiency considering a minimum reinjection temperature of 40°C and an overall auxiliary consumption of 440 kW (2 points). In order to increase the power output, the geothermal fluid is further heated to 410°C in a biomass boiler (series configuration and neglecting pressure drops, biomass is oak described in the table below). The biomass boiler consists of an evaporator, a super-heater and a regenerative air pre-heater fed by the exhaust gases. Deter- mine the biomass flowrate on as received basis (consider ∆h evaporation,water = 2450 kJ/kg) assuming an overall plant efficiency (geothermal+biomass) equal to 24.4%…