Thermal performance of ground as an inexpensive solar collector and storage system

This paper presents an analysis of the performance of an inexpensive integrated solar collector and storage system. The flow of fluid and heat capacity of the storage material in the container is considered simultaneously and an evaluation is made for the resulting outlet fluid temperature for various flow rates and materials by solving the Fourier heat conduction equation with appropriate boundary conditions in different regions. This evaluation, combined with energy balance considerations, yields an expression for the transient rate at which heat can be retrieved—by keeping flow rate constant. Numerical calculations, corresponding to a typical winter day in Delhi have been carried out. The heat retrieval efficiencies are of the order of 50-25%. A phase difference of about 12–18 h is obtained between the maxima of solair temperature and outlet water temperature. The efficiency of the system increases with flow rate and decreases with depth of plane of heat retrieval. Concrete is found to be the best inexpensive sensible heat storage material out of those materials considered.