Analysis of thermal well storage for solar collector—heat pump systems

The storage of solar heat in the earth beneath a building, using closed circuit heat storage wells with a solar collector and water-to-air heat pump, is analyzed. ‘Closed circuit’ means that the water is circulated only between the collector, well, and heat pump, not between the well and the soil. An iterative steady state simulation of annual performance is demonstrated, using equations which were developed for the heat flow rates to and from the well and for the heat storage in the soil surrounding the well. Design and cost analysis examples are solved.Thermal wells are one means to provide large (seasonal) heat storage capacity for retrofit solar installations at relatively low cost and without added space requirements.