陕西关中地区地热能丰富,利用中深层地热结合水源热泵形成的能量梯级利用系统,是中深层地热高效利用的重要方式.本文以杨凌农业示范园能源站中深层地热水+水源热泵的热量梯级利用系统为例,介绍了系统工作原理并建立了系统仿真模型,以中深层地热取热效率分析了该热量梯级利用系统性能并与直接利用板式换热器的取热系统进行了对比,并对系统经济性进行了评估.研究结果表明,与直接利用板式换热器的取热系统相比,该热量梯级利用系统取热功率提高了2.5～3倍,取热效率提高了 40％～50％;在满足供热量的条件下,较低的供回水温度更有利于系统的高效经济运行;此外,增大热泵容量还可以进一步提高取热效率,但随着热泵容量的增加其性能系数(Coefficient of performance,COP)降低明显,单位热成本(Levelized cost of heat,LCOH)降低速率减缓,本文中热泵容量大于120 kW时,继续增大热泵容量对系统经济性的改善效果不再显著.
Study on the Optimization of Cascade Heating System of Middle-deep Geothermal Coupled Water Source Heat Pump in Winter
The Guanzhong area of Shaanxi is rich in geothermal energy.The energy cascade utilization system formed by using the middle-deep geothermal energy combined with water source heat pumps is an important way to efficiently utilize the middle-deep geothermal energy.Taking the energy cascade utilization system of deep geothermal water and water source heat pumps in Yangling Agricultural Demonstration Park Energy Station as an example,this paper introduced the working principle of the system,and established a system simulation model.The performance of the energy cascade utilization system was analyzed using the heat extraction efficiency of mid-deep geothermal water and the simulation results were compared with the heat extraction system using the plate heat exchanger directly.In addition,the system economics were evaluated.The research results show that compared with the heat extraction system that directly utilizes the plate heat exchanger,the heat extraction power of the energy cascade utilization system is increased by 2.5-3 times,and the heat extraction efficiency is increased by 40％-50％.While meeting the supply temperature,the lower supply and return water temperature is more conducive to the efficient and economical operation of the system.In addition,increasing the heat pump capacity can further improve the heat extraction efficiency.However,with the increase of heat pump capacity,the coefficient of performance(COP)decreases significantly,and the rate of Levelized cost of heat(LCOH)decrease slows down.In this paper,when the heat pump capacity is greater than 120 kW,the improvement effect of increasing the heat pump capacity on the system economy is no longer significant.
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