Charging of a heat storage coupled with a low-cost small-scale solar parabolic trough for cooking purposes

Two charging experiments of a solar heat storage are presented. The heat storage is coupled with a self-circulating solar parabolic trough filled with thermal oil (Duratherm 630). The absorber tube is not insulated in the first test, and insulated with a glass tube during the second test (the air layer insulating the absorber is 7 mm thick, enclosed between two glass cylinders). An electronic system tracks the sun during the experiments. The storage is mainly oil-based but contains a significant part of nitrate salts in order to store energy with latent heat (melting temperatures: 210-220 degrees C). The salts are contained in eight aluminum cylinders. The cylinders are connected to a top plate and the assembly is immersed into a container where the oil circulates. The objective is to store heat at high temperatures for cooking purposes (boiling water and frying). The results show that at low temperatures, the absorber without insulation is much more effective. But when the storage temperature approaches 200 degrees C, the glass tube becomes an advantage and a necessity for the further heat collection at higher temperatures. Above 200 degrees C, it becomes difficult to collect without insulation around the receiver. (C) 2013 Elsevier Ltd. All rights reserved.