Analysis of deep borehole heat exchanger with horizontal branch wells for building heating

Abstract

The development and application of enhanced geothermal system and hydrothermal system are constrained due to high cost and high risk of induced seismicity or heavily reliance on hot water reservoir. Deep borehole heat exchanger (DBHE) technology is independent of hot water reservoir and hydraulic fracturing; however, the poor thermal conductivity of rocks limits its performance improvement. To deal with these problems, a novel technology for acquiring geothermal energy using DBHE with horizontal branch wells (DBHE-HBW) is proposed here. It is found that DBHE-HBW has better performance than DBHE and, under the condition of nearly equal total cross-sectional area of well tube, the smaller the horizontal well tube diameter, the greater the thermal output and the shorter the payback period of DBHE-HBW. Therefore, DBHE-HBW can be recommended for large-scale application in building heating sector.