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

It is the development trend of renewable energy utilization way to carry out a variety of energy combination of complementary advantages,and the use of hybrid solar ground-source heat pump system(HSGSHPS)is one of effective models of energy saving and emission reduction.The underground soil of ground source heat pump system is the mass for heat release and heat storage.The soil temperature directly influence the energy consumption of the unit and system performance,and even the success or the failure of the system.Ground source heat pump system design and actual operation may differ greatly.Thr monitoried data for building energy consumption of the actual operation of the combination of HSGSHPS was analysed during the operation time in 2012.5-2016.3.This paper provided different optimization ideas for the operation of the subsequent HSGSHPS,including ground-source heat pump system(GSHPS)operation parameters adjustment,solar assisted GSHPS(SAGSHPS)auxiliary operation optimization and SAGSHPS straight for parameter adjustment,etc.The research of geothermal control strategy is carried out by the comparison of test and numerical simulation.Accoording to the tests conductected in the cooling season and the heating season in 2015,the preliminarily conclusions: Firstly,in the heating condition,reasonable reducing the heat pump set temperature or pump frequency,reducing the heat and slow down the declining rate of ground temperature can improve the coefficient of performance(COP)of GSHPS under the precondition of meeting the indoor load;while in cooling conditions,a reasonable increasing refrigeration pump set temperature or lower frequency,reducing the heat and restrain the rising rate of ground temperature can also increase the COP of GSHPS.Secondly,the COP of HSGSHPS increases with the increasing of auxiliary runtime of SAGSHPS under the “intermittent operation and supplementary heating” measures.Finally,a reasonable reducting of the working temperature of a heat collector or the direct supply temperature and to improve the proportion for direct heating time made the soil temperature recovery on time,on which can improve the COP of SAGSHPS.Based on the dynamic software TRNSYS,a simulation model,HSGSHPS,which was verified against the experimental data.So that the deviation between the simulation results of GSHPS and SAGSHPS subsystems and the test results is within 10%.The simulation was developed at different given system operation parameters and operation modes.The control strategy of HSGSHPS was also improved in different stages of geothermal energy through the analysis of simulation results and the preliminary regularity trials.The long-term operation simulation prediction for control strategy and normal mode of HSGSHPS were analyzed respectively in the system operating mode.The results show that the group of borehole heat exchanger(BHE)temperature changes smoothly under the HSGSHPS combined control strategy.The soil temperature is 15.10? in the first years,and the temperature is about 15.80 ? after 10 years of operation time,which was ensured the BHE temperature balance.Meanwhile,the paper also solved the problem of low heat storage efficiency of SAGSHPS in the later period of non-heating supply caused by the temperature close to the heat storage saturation temperature.