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POWER PRODUCTION FROM RENEWABLE ENERGY AY 2018-19 17th June 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 (17 points) A steam cycle is coupled with a biomass boiler with mass -flowrate equal to 7 kg/s and biomass composition reported below. The biomass has 50% moisture content (oak with harvest conditions) which results in a boiler efficiency equal to 68.7% on HHV bas is (hevaporation equal to 2,44 MJ/kg). Assuming that the steam cycle electric efficiency is equal to 3 6% (HHV base), what are the net electric efficiency (LHV base) and the net power output of the plant (3 points)? Determine the stack temperature and the boiler efficiency (LHV), knowing that the combustion air flowrate is 21 kg/s, thermal losses from boiler walls are equal to 1% of the fuel HHV thermal input and neglecting ashes losses. Furthermore the un-burned carbon is 1.5% (dry basis), water in the flue gases is 100% in the vapor state, and ambient temperature is 15°C. (6 points) (cp flue gases 1.11 kJ/kgK, heating value of carbon is…