Operating Results of a Thermocline Thermal Energy Storage Included in a Parabolic Trough Mini Power Plant

摘要

A thermocline thermal energy storage tank consists in using one single tank to store sensible heat. At almost any time, three zones coexist in the tank: a hot fluid zone at the top, a cold fluid zone at the bottom, and an intermediate zone called thermocline. Filling the tank with solid materials enables to reduce cost and to maintain the thermal stratification during stand-by periods. The present paper deals with a 230 kWh experimental thermocline tank that is included into a 150 kWth parabolic trough mini power plant. The heat transfer fluid is a non-pressurized synthetic oil (dibenzyltoluene) that flows through alumina spheres in the storage tank. The solid materials are contained into baskets in order to facilitate their removing and replacement. Thermocouples measure temperature along the center of the cylinder and along its radius. It is therefore possible to study the thermocline behavior thanks to the measured temperature profiles. A typical charge, a typical discharge and a stand-by process are presented and storage performances are discussed. The behavior of the tank in a dynamic system is also considered, by analyzing a typical day of solar production and storage of the energy surplus.