Summary: | An investigation of the performance of a Solar Energy System using earth as a seasonal energy storage was performed. The investigation had several directions: (1) Computer modeling of building performance using a solar energy system with a conventional short-term water energy storage, and using seasonal energy storage was carried out. A computer program for building energy analysis, DOE 2.1 made by Lawrence Berkley Laboratory, was used for this purpose. The analysis predicted that a solar energy system using seasonal energy storage will outperform the system with conventional short-term energy storage by 10% in yearly energy savings. (2) Experimental investigation was carried out on a unique solar energy system designed and built for the Smith Academy Junior-Senior High School in Hatfield, Massachusetts. The results showed that earth was able to accept energy well in the Summer and early Fall and retain it till late November, giving it off to the building when requested by the control system. Problems in the first year of operation, however, caused the savings to be lower than predicted. (3) Economic analysis was carried out using simple payback and life cycle costing, assuming a discount rate of 9.1% and varying fuel inflation rates from 6% to 18%. A method for obtaining unit prices and total prices of a solar energy system of this kind was presented. The analysis showed that a simple payback and a payback based on life cycle costing were approximately equal (13 and 12.5 years respectively), for fuel inflation rate assumed at 12%. Analysis was based on a system cost to the town including a 60% grant from the State of Massachusetts. (4) Simple guidelines for design of such solar energy systems in future projects are presented. They give recommendations on the type of system suitable, the need for top and side insulation of the SETS, and the steps for design of different system components.
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