ENERGY 20250714

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ENERGY SYSTEM FOR SUSTAINABLE ENGINEERING EXAM 14.07.2025 First part: Theory (no access to any supporting material) – 1 h Second part: numerical exercise (access to written supporting material) – 1.15h FIRST PART: THEORY QUESTIONS MULTIPLE CHOICE QUESTIONS: 20 points, true or false, correct 1 point, incorrect -0,5 point, missing 0 points In a gas fired steam generator (α = air/fuel ratio): T F The PM emission is lower if the boiler is fueled with biomass rather than natural gas The boiler efficiency is higher if the stack temperature decreases The boiler efficiency can be higher than 100% The boiler efficiency is higher if the % of O2 in the flue gas increases In a cooled gas turbine, the difference between the COT and the TIT is T F Due to the dilution air flow rate in the combustor Due to the overall cooling flow of the entire turbine Due to the first stage (stator + rotor) total cooling flow Influenced by the expansion in the first nozzle In a photovoltaic cell: T F The photons with energy > band gap pass through the cell as if it was transparent Both the direct and diffused radiation can be exploited The conversion efficiency increases if the temperature increases The max electrical efficiency is achieved by multi-junction cells In a photovoltaic plant: T F EOH can reach 2500/3000 h/year EOH increases if the photovoltaic plant is coupled with batteries In the north hemisphere, the panels orientation is always better if it south The most used cells are single or multi crystalline silicon cells If biomass is used as fuel for combustion: T F The PM emission is due to unburnt carbon The bigger PM can be abated with the use of cyclone systems With FGD we use ammonia/urea QUESTION 1 (5 points): Draw and comment the plant configuration and the heat -electricity (Qu-Eel)…