24 June 2014

Sizing and simulating geothermal bore fields using thermal response factors

This paper summarizes the state-of-the art of geothermal bore fields design and simulation using thermal response factors. In the first part of the paper, the concept of thermal response factors, also known as g-functions, is examined. It is shown that the ratio of
buried depth to borehole height should be considered as it becomes important for short boreholes. Results obtained with an analytical technique to obtain g-functions are presented and the effects of using different types of borehole wall boundary conditions are analyzed.
Then, a procedure to size bore fields based on g-functions is presented. The procedure involves iterative calculations where g-functions are evaluated as the solution proceeds. Finally, the basic equations to perform annual simulations of bore fields are presented and the concepts of temporal superposition and load aggregation are reviewed.