Investigation on geothermal water reservoir development and utilization with variable temperature regulation: A case study of China.

• Heating mode is considered in numerical simulation and multi-objective optimization. • Regulated systems consume 50% less water and 25% more electricity than unregulated systems do. • The regulated systems have low construction cost with stable operation. • The regulated geothermal heating system could be applied in other regions. Geothermal heating technology is an important technique for alleviation of energy crisis and environmental pollution. A numerical simulation and multi-objective optimisation for geothermal heating systems are conducted considering factors such as the heating load, heating modes, and region characteristics. Heating modes play a vital role in the utilization of geothermal reservoirs. It is found that regulated geothermal heating system can postpone the formation of thermal breakthroughs and shrink radius of the cold front. It's also indicated that well spacing and production rate are the two main factors affecting the production performance and emission reduction of geothermal heating systems. Construction investment of geothermal wells and the annual water consumption of regulated geothermal heating system decreases by up to 30% and 60%, comparing with unregulated geothermal heating system, although electricity costs increase by 5% to 25%. Multi-objective optimized heating system parameters for Qingfeng project in China are achieved. The best regulated geothermal heating system with well spacing of 295 m and production rate of 100 m3/h generates the highest efficiencies in terms of heat production, emission reduction, and economic performance. The mathematical model and multi-objective optimization model can provide references for utilization of geothermal heating technology in other places with similar conditions. [ABSTRACT FROM AUTHOR]