Performance Research On The Hybrid Solar-Ground Heat Pump And Seasonal Energy Storage System Under The Typical Climate Conditions

Energy and environment have become the major problems in the social development.With the development and progress of society,the demand for heating in our country is increasing.But heating by clean energy such as solar energy and geothermal energy is an effectively approach to China’s energy shortage and environment pollution problems.This paper composed a hybrid solar-ground heat pump and seasonal energy storage system for large-scale buildings,and a simulation model was built in typical climate condition.Compared the annual simulation results and the predecessor’s experiment results to ensure the feasibility of simulation analysis.Based on this,the simulated results in Shanghai was analyzed and optimized.Finally,the applicability of the system in hot summer and cold winter regions,cold regions and severe cold regions in China was comparatively studied.Firstly,the principles and operation modes of a hybrid solar-ground heat pump and seasonal energy storage system was composed.The system includes four main subsystems:the solar collecting subsystem,the underground heat storage subsystem,the centralized heating subsystem and the large-scale buildings.The operation modes were determined by the heating requirement and climate characteristics,including the heat storage mode and three heating mode.Then,a energy storage and heating model of the hybrid solar-ground heat pump and seasonal energy storage system was established based on the TRNSYS software,and reasonable parameters were selected based on the relevant specifications and standards for solar energy and ground source heat pump.The simulated seasonal solar energy storage results were compared with the actual experiments results.The comparison results showed that the simulation results were basically consistent with the results of the measured system.Therefore,the TRNSYS model is considered reasonable.Then analyzed the characteristics of the TRNSYS simulation results of the solar-ground heat pump and seasonal energy storage system in Shanghai area.The results of the analysis showed that when the the heat storage season start time is April,the temperature of the heat storage soil was increased by28.9°C.The annual storage energy of the system was 3136.8 GJ,and the average heat storage rate of the storage soil was 79.4%.The system solar fraction was 35%and the annual coefficient of performance was 3.82.Based on the results,changed the start time of the heat storage season and obtained best starting month for the heat storage season was April.Then,by optimized the area of the collectors and the volume of the storage soil volume to promote the solar faction.The the optimized ratio of the collector area to the annual thermal load was 3.0 m~2/MWh,and the optimized ratio of the storage soil volume to the area of the collectors was 6.5 m~3/m~2.Finally,simulated the hybrid solar-ground heat pump and seasonal energy storage system under different climatic conditions under the same heating area and the results were analyzed and compared.Shenyang,Beijing and Shanghai were selected as the representative cities in the severe cold regions,cold regions and hot summer and cold winter regions,respectively.The simulated results showed that the annual average annual collector efficiency in Shanghai,Beijing and Shenyang were from high to low;the temperature of the storage soil increased 34.6℃,33.0℃and 34.5℃,respectively;the storage energy were 2723.2 GJ,2764.1 GJ,3325.0 GJ,respectively;and the average heat storage rate were 75.15%,75.30%,77.34%,respectively,the lower the initial temperature of the storage soil,the higher the heat storage rate,the better the heat storage performance.And the annual coefficiency of performence were 4.0,3.5 and 3.2,respectively.The hybrid solar-ground heat pump and seasonal enegy storage system is also applicable in cold regions and severe cold regions and has a good energy conservation effects.Then optimized the system in severe cold regions and cold regions respectively.The optimized ratio of the collector area to the annual heating load in severe cold regions was 4.0 m~2/MWh,and the optimized ratio of the storage volume to the collector area was 4.0 m~3/m~2,the optimized solar fraction was 21.2%.The optimized ratio of the collector area to the annual heating load in cold regions was 4.0 m~2/MWh,and the optimized ratio of the storage volume to the collector area was 4.0m~3/m~2,the optimized solar fraction in cold regions was 35.8%.