ES210719 theoretical test

Page 1

POWER PRODUCTION FROM RENEWABLE ENERGY AY 2020-21 19th July 2021 Prof. Silva Time: 1 hour Instructions for the examination: 1) Clearly indicate your name on all the sheets you will deliver. 2) Give a synthetic and clear answer to as many questions as possible. The final score will be normalized according to the average results. 3) Talk with colleagues and / or cheating will cause the cancellation of the exam. 1. Consider a three-bladed, horizontal-axis wind turbine with a rotor diameter of 110 m coupled to a full scale converter. Analyze the behavior of the turbine in the following conditions: cut- in, nominal condition, cut-off. For each point indicate the wind speed and the expected/cal- culated values of Cp, tip speed ratio (λtip), rotational speed and electrical power output (assume reasonable values for the main parameters). Qualitatively plot the points on a graph (preferably using a multi-scale Y axis) versus wind speed. 2. Explain the concepts of ‘Energy pay-back time’ and “Energy Return On Investment” for a renewable energy plant and identify the main items that have to be considered for their definition. If possible, give some examples of different renewable technologies. 3a. For Energy and Mechanical Engineering students: Describe the main losses of a crys- talline silicon PV cell inserted in a module, starting from the theoretical efficiency of the p-n junction (efficiency that considers only the fundamental loss of a PV cell). 3b. For Management Engineering students: describe the various investigation techn iques that can be adopted to assess the feasibility of a geothermal exploitation. 4a. For Energy Engineering students: Discuss the effect of a 7 -8 equivalent hours storage capacity on the LCOE for a modern CSP power plant. 4b. For Mechanical and…