Research On The Control Strategy Of Solar-ground Source Heat Pump System

Solar ground-source heat pump system utilized both solar energy and shallow geothermal energy is a high efficiency,energy saving and environmentally friendly way of renewable energy utilization.In each stage,different load demand and well temperature may affect the system's actual operation performance.System operation with fixed parameters can not be well matched with the construction load in different stage,so the system can not be implemented in the optimal efficiency.In this paper,the parameters of the system in each stage was adjusted in order to realize the goal of meeting load demand,energy saving,high efficient operation and long-term stability of the system.Taking the operating characteristics of the system as the breakthrough point,the operating results of the system are studied.The relationship between the COP,the well group temperature and the load size under the fixed parameters is analyzed.The variation law under the variable parameters of HP cooling capacity,HP heating capacity,HP power,COPHP,COP system with the pump frequency and HP set point is studied.The heat storage characteristics of the non-heating season in different stage are analyzed and the parameters adjustment scheme is given according to special circumstance.The influence of different starting temperature and HP2 heat pump set point on the operating results under the heating season of the SAGSHP system is described,and the parameter adjustment scheme to SAGSHP is discussed.On the basis of TRNSYS,the model parameters,the external file,control logic,module connection and structure adjustment of solar ground-source heat pump system model are modified,so the relative error of the system simulation results and the experimental values are maintained at 10%.On the basis of the calibration model the operating results of the system under more operating conditions are discussed.The simulation results are used to obtain the optimal operating parameters of the system,and the full year control strategy of the whole system is obtained.The results of the simulation of the system under normal mode and control strategy show that: compared to normal mode,under the control strategy,the system can realize indoor building matching with HP capacity,which improves the COPHP,increases the thermal collector and thermal storage in non-heating season and the solar direct heating quantity proportion of SAGSHP in heating season,the system can save 6.2% energy and 7.6% electricity every year with the load demand.The results of system simulation model run for a decade under the normal mode and control strategy show that: running under the control strategy,the system contributes to the stability of GSHP ground temperature,provides conditions for HP1 running efficiently in cooling season and heating season,helps to improve the ground temperature of SAGSHP system,and also makes it more effective for HP2 to run efficiently.