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ENERGY CONVERSION A 2020-21 Note: you can keep this text for self-evaluation at the end of the exam; in case you withdraw, you shall return it. Exam 01/02/2021 Please, write your person code and surname-name on the sheets you hand in. Exercise 1 (10 points) The micro gas turbine named AE-T100 by Ansaldo Energia is tested with natural gas as well as with blends of natural gas and hydrogen. The micro gas turbine when operating with natural gas is characterized by: • net electric power output: 100 kW • net electric efficiency (with respect to LHV): 30% • turbine inlet temperature: 950 °C • turbine outlet temperature: 645 °C • recuperator percent pressure drop per side: 7% • shaft rotational speed: 70000 rpm Hydrogen (LHV of 120 MJ/kg and HHV of 142 MJ/kg) is generated at a rate of 0.15 g/s by an electrolyzer absorbing an electric power of 45 kW. Hydrogen is stored in a tank at 3.0 MPa. During the tests with blends, hydrogen is added to natural gas and the turbine inlet temperature raises, while the shaft is controlled electronically at constant speed. Please: i. motivate clearly the solution procedure and highlight neatly the assumptions (1 point); ii. sketch the overall plant process diagram, including the electrolysis process, and the gas turbine cycle T-s diagram (2 points); iii. calculate the mass flow rate of breathed air as well as the combustor inlet temperature (2.5 points); iv. compute the thermal power dissipated by the electrolyzer (2.5 points); v. comment without computing how the turbine outlet temperature varies during the tests with hydrogen (2 points). Exercise 2 (12 points) Consider a power plant comprising a natural gas-fired boiler and an organic Rankine cycle. The power cycle is a saturated non-recuperated cycle that is designed in a cogenerative…