5 July 2022 with results

Pagina 1

SOLAR AND BIOMASS POWER PRODUCTION AY 2021-22 5th July 2022 Prof. Giampaolo Manzolini Time: 1h 30 min 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 can 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 is NOT ALLOWED to use material other than this (e.g. books, clipboard etc.). 6) Not all the provided inputs are necessary for the problem solving Exercise 1 (15 points) Consider a CSP plant based on Linear Fresnel technology. The characteristics of the solar field are reported in the following table. Number of mirrors 100 Mirror width 15 cm Mirror lenght 100 m optical efficiency 0.58 DNI 950 W/m2 Question a) Please determine the thermal efficiency of the receiver knowing that the solar salts mass flowrate is equal to 1.9 kg/s, the inlet and outlet temperatures are equal to 290°C and 550°C and the molten salts have an average cp equal to 1.5 kJ/kgK (4 points). Question b) Please determine the CR concentration ratio knowing that the heat transfer coefficient is equal to 5 W/m2 K, the emissivity to 0.15, the effect of the glass envelope can be neglected, and the average tem- perature difference between HTF and external tube wall is 30°C (Stefan-Boltzmann constant equal to 5,67 x…