Ex 2 GEOTHERMAL BINARY POWER PLANT Text

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GEOTHERMAL BINARY POWER PLANT Power Production from Renewable Energy – A.Y. 2020/21 Prof. Paolo Silva – Ing. Dario Alfani A geothermal well produces a flow rate of 1000 t/h of liquid water (vapor quality x=0) at a temperature of 170°C. The proposed energy conversion system is a saturated cycle using iso-pentane as working fluid (chemical formula C5H12; in FluidProp 3.0 use “freeStanMix; isopentane”). 1) First, consider a closed Rankine cycle, condensed with water from a cooling tower, given the following data: - Inlet temperature of the cooling water to the condenser Twat,in = 18°C - Temperature increase of the water in the condenser Tcond = 8°C - Sub-cooling ∆T of the fluid at economizer outlet Tsub-cool = 3°C - Evaporator exchange area Aeva = 1300 m2 - Overall heat transfer coefficient of the evaporator Ueva = 900 Wm-2K-1 - Overall heat transfer coefficient of the economizer Ueco = 800 Wm-2K-1 - Overall heat transfer coefficient of the condenser Ucond = 500 Wm-2K-1 - Condensation temperature Tcond = 30°C - Minimum reinjection temperature to the geothermal well Treinj  70°C - Turbine isentropic efficiency ηis-T = 80% - Electrical generator mechanical-electrical efficiency ηmel-g = 95% - Pump hydraulic efficiency ηhyd-p = 70% - Pump mechanical-electrical efficiency ηmel-p = 90% - Relative pressure loss (∆p/p) in the economizer (p/pin)eco = 0.2 - Absolute pressure loss in the condenser (cooling water side) pcond = 2 bar - Other cycle pressure losses negligible It is required to: a) Determine the evaporation pressure that optimizes the plant net power output. b) Calculate the cycle electrical efficiency, the overall plant efficiency and the second law efficiency for the optimal pressure value found in a). c) Report in a table the values of mass flow rate,…