A MATLAB Toolbox for Optimization of Deep Borehole Heat Exchanger Arrays

Abstract

Due to their slow thermal response arrays of borehole heat exchangers (BHE) represent suitable storage systems for seasonally fluctuating sources like solar energy. Excess heat is fed in during summer and extracted in winter. Certain requirements have to be met by such a system: the stored heat must remain in place and the working fluid must maintain an extraction temperature sufficiently high for the specific heating purpose at all times. Since drilling is the most critical cost factor, the required number of BHEs and their respective distance and length need to be optimized. For this purpose a MATLAB toolbox code was developed. It deploys a tetrahedron mesh-based finite element code, a thermal resistance and capacity model for BHE interaction and mathematical optimization techniques. It can effectively simulate and optimize a BHE heat storage system.