ES220719 practical test

Page 1

POWER PRODUCTION FROM RENEWABLE ENERGY AY 2021-22 19th July 2022 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 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 (15 points) A geothermal source has the following characteristics at the outlet of the well: temperature 180 °C, enthalpy 1050 kJ/kg. CASE A Consider a single flash direct steam cycle cogenerative plant, based on a cooling tower condenser with a condensation pressure of 0.075 bar. The flash pressure is 3.3 bar. Design the lay -out of the plant (i) with all the components ( 1 point), considering that the cogenerative heat exchanger is fed by the separated liquid from the flash chamber. Neglecting the presence of non-condensable gases and considering a reinjection temperature of 50°C , calculate (ii) the mass flow rate of the geothermal fluid that should be extracted from the well to obtain a net electric power output of 8 MW, knowing that the electric power consumption of all the auxiliary components of the steam cycle is 440 kW, and that the isentropic efficiency and the organic -electric efficiency of the turbogenerator are respectively equal to 80% and 93 % (4 points). Then determine (iii) the vapor fraction at the outlet of the steam turbine (1 point) and (iv) the net electrical…