24 June 2014

TEMPERATURE STRATISFACTION OF CIRCULAR BOREHOLE THERMAL ENERGY STORAGES


Circular borehole field geometries are sometimes preferred when designing
borehole thermal energy storage systems, including controlled radial temperature gradients from the center and across the borehole field. A numerical model has been described in this paper in order to study the influence of connecting boreholes in radial zones with different thermal loads. The studied geometry consists of 3 concentric rings having 6, 12, and 18 boreholes, and the boundary condition at the wall of all boreholes can be flexibly changed. In this case, a realistic quasi-uniform temperature condition, observed using distributed
temperature measurements, was applied at the borehole wall, giving a temperature gradient of 1 K from bottom to top in all boreholes. The boreholes are thermally connected with each other. Thermally connecting the boreholes is one of the alternatives of the Superposition Borehole Model (SBM). A few control strategies for using the circular borehole field are
studied, both for balanced and unbalanced thermal load cases.