SEASONAL STORAGE OF SOLAR ENERGY USING INSULATED EARTH

Abstract

An experimental investigation is presented for a seasonal earth thermal storage system. Results of operation from May 1983 to March 1985 of a full scale seasonal earth storage system are reported. The seasonal storage system under study consists of an underground insulated storage enclosing 1926 cubic meters of earth. The storage is charged by 171 square meters of flat plate solar collectors. Energy transfer to and from the storage is accomplished via a single layer of pipes installed horizontally at the storage mid-plane. The earth storage and collectors are coupled to water source heat pumps which provide space heating for a building of 5000 square meters of floor area. This system is located in Hatfield, Massachusetts, USA. This was a retrofit into an existing building. Construction required no special equipment or techniques. After full charging, the earth storage reaches a temperature of approximately 50°C. The use of seasonal storage resulted in a 136% increase in solar fraction compared to conventional storage during the month of December, and a 97% increase in January. These results indicate that successful seasonal solar energy storage and recovery can be achieved with a system of scale and design used in this experiment.