Energy Balance and Thermal Evolution Analysis of Heat Transfer Fluids of Stirling Engine and Boiler at Focal Point of a Parabolic Solar Concentrator

Abstract

: A solar concentrator is a technology that converts direct solar radiation into heat. The parabolic concentrator is the best technology for producing electricity from solar energy, because of its high electrical efficiency, about 41%. This technique is the least mature due to the difficulties related to the storage of produced energy. This work concerns a system of two heat receivers, placed at the focus of the parabolic reflector. These two receivers are a boiler and a Stirling engine. The boiler is intended to heat a thermal fluid that will be stored while Stirling engine will produce electricity directly. We studied the thermal balance and the evolution of the temperature of thermal fluids of Stirling engine and the boiler installed at focal point of reflector. The concentrator used is a parabola with surface of 12.6 m². The simulations were carried out in the vicinity of direct radiation measured at 1 pm o'clock local time. The temperature recorded at the focal point varies from 30°C to 900°C for a duration of 80 seconds; when the direct radiation is about 900W/m². This temperature increases from 30°C to 1050°C, for an operating time of 120s. The average temperature of the three fluids in the receiver (permanent fluid in the boiler, heat transfer fluid to be stored, and thermal fluid of Stirling engine) increases from 30°C to over 400°C in less than 1500s. These thermal fluids at this temperature make it possible to operate turbine through the thermal storage system and Stirling engine, to produce electricity.