Dynamic model of a small scale concentrating solar cooker with rock bed heat storage

Abstract

This study presents a dynamic model for a concen-trating solar energy collector with an integrated rockbed heat storage system. The model is based onnumerical integration of a set of conservation equa-tions for mass, momentum and energy of the heatcarrier, the rock pebbles and the walls. The heatcarrier is compressible air. Numerical solutions areimplemented based on implicit time integrationwithout iterations. Stability problems at large timesteps do not occur but the accuracy is reduced. Themodel predicts pressure, velocity, density and tem-peratures of the fluid, rock bed and wall in time andalong the bed. The model is validated with experi-mental results in a laboratory setting on tempera-ture profiles during charging and discharging of rockbed heat storage. The intention is that the modelshall serve as a computational tool for upscaling ofair based concentrating solar energy systems withrock bed heat storage units.