Demonstration and optimization of a solar district heating system with ground source heat pumps

Experimental and theoretical investigations have been carried out on the first large scale solar assisted ground source heat pump (SAGSHP) for heating and cooling of a village in the outskirts of Beijing. Long term performances of the system without and with solar heating were monitored. A TRNSYS model of the SAGSHP system was developed and validated against the measured data. Based on a parametrical investigation using the model, an optimized solution was proposed. It is shown that adding a domestic hot water system to the original SAGSHP system will not only help to secure thermal balance of the ground but also reduces primary energy consumption for hot water by 70%. The system COP increases by 9.4% from 2.42 to 2.65 and the annual overall operating cost decreases from 892,000 CNY to 794,000 CNY with only a small increase in equipment cost. Under the premise of ensuring thermal balance of the ground, there is an optimal match between the size of the ground heat storage, the collector area and the tank volume. Experience and lessons learned from the project are conducive to successful implementation of similar projects in the future.