Theoretical Research And Practice For Solar Seasonal Storage System Based On Ground-source Heat Pump

The approach of using solar thermal energy storage based on GSHP can solve the performance deterioration of heating problems effectively. The theory for solar seasonal storage system based on Ground-source Heat Pump was improved including feasibility analysis, system design, experiment cycle prediction, TRNSYS simulation analysis, etc, which was suitable for heating-dominated building climate zones such as cold zones and severe cold zones. The practice of solar seasonal storage was carried out and supplied by a practical project.First, physical model and mathematical model of double U buried pipe were built to analyze the feasibility of solar seasonal storage system based on Ground-source Heat Pump. Matlab was used to solve the theoretical model. So, the soil temperature distribution and its fitted equation were gained. Result shows that the heat exchange capacity of the buried pipe can meet the requirements of the heat storage.Next, according to the energy bills of the GSHP system located in the new campus of Tianjin Polytechnic University in heating season of 2010, 2011 and 2012, considering several factors such as solar energy utilization, possible extreme weather and pipe heat loss and solar radiation intensity, experimental period was predicted. The real-time solar radiation intensity, the temperature of the supply and return water and the temperature of the soil in different depth was measured respectively to calculate the real-time solar radiation, the real-time storage heat in experimental period and the temperature-rise of the soil. The concept of solar energy utilization and deferred response were proposed to explain the relationship between solar radiation quantity and soil thermal storage quantity. In the experiment, total solar radiation quantity is 956991.30MJ(265830.92kWh); total soil thermal storage quantity is 480299.07MJ(133416.41kWh), which is 2.03 times more than average extraction heat quantity(65741.3kWh). The average solar energy utilization efficiency is 50.2%, which means 50.2% of solar radiation quantity converted into soil thermal storage quantity. The predictable thermal storage task was overfulfiled.Once more, TRNSYS was used to simulate the solar energy storage experiment process which can solve the problem of seasonal solar energy storage in transition season. Simulation model and the error correction model were built to eliminate the affect made by meteorological parameter and equipment heat dissipation. Result shows even though the simulation period is in transition season, the thermal storage quantity(247719.47kWh) can meet the thermal storage requirement.Last, thermal storage effect was evaluated by 4 factors, which is soil temperature, inlet and outlet temperature of evaporator, the COP(Coefficient of Performance) of the system and unit and economic and environmental evaluation. Result shows the COP of the GSHP system and the unit decreased gradually year by year without solar energy storage process. But the COP of the GSHP system and the unit rose by 3.4% and 2.4% indistinctively after the solar energy storage experiment.