Performance of geothermal single well for intermittent heating

Abstract

Single well geothermal heating (SWGH) can widely be used all around the world, no matter if there are rich hot water reservoirs. However, its promotion is limited due to long payback period. To reduce the payback period, the intermittent operation mode is proposed in terms of the commercial buildings. An experimental test for continuous heating is firstly carried out, and the extracted thermal output is 448.49 kW with the static payback period of 7.17 years. A mathematical model is then developed in order to simulate the performance of intermittent operation. The simulated results show that the extracted thermal output for intermittent operation is always greater than that for continuous operation due to having the heat recovery period. The extracted thermal output is respectively 619.12 and 587.51 kW in the first and the tenth heating season at the fixed injection temperature and velocity. The extracted thermal output can keep stable if changing the injection temperature and velocity, and thus the imbalance of the extracted thermal output among different heating seasons can be adjusted. The static payback time for intermittent operation is reduced to 5.16 years compared to continuous operation, which will speed up the spreading and application of SWGH technology.