Research On Ground Source Heat Pump-solar Heating System With Heat Supply From Heating Network Return Wate

The growth rate of heating demand for residents in China far exceeds the speed of the municipal heating network planning and construction and the issue of building energy supply has become increasingly serious.To address this problem,solar energy and ground source heat pumps have been developed as new energy sources,and the relevant technologies are already mature.Lowering the temperature of the heating network return water can greatly benefit waste heat recovery and also improve the energy utilization rate of the thermal power plant.The ground source heat pump-solar heating system designed in this article aims to increase the heating capacity of the municipal heating network,alleviate the soil thermal imbalance caused by the long-term operation of the ground source heat pump,and accelerate the energy structure reform by lowering the temperature of the heating network return water through supplementary heating using the ground source heat pump and solar energy.Using the DeST energy consumption analysis software,this article calculated the cumulative heat load of a five-story office building with a heating area of 3814m~2 is 306203k W·h and the maximum heat load of the building to be 242 k W.Load characteristic analysis revealed that the load was in the valley range from 11:00-18:00,and in the peak range from19:00 to 7:00 the next day.In addition,simulations showed that the coefficient of performance of the heat pump unit decreased as the unit load decreased when the unit load rate was below25%.Solar energy can effectively reduce system power consumption when it accounts for 25%of the building load.To make the hot water supply and heating system more efficient and energy-saving,this article designs two heating systems based on the different roles played by solar energy in winter.The multi-heat source heating system with solar energy cascade utilization opens the solar independent heating mode when the water tank temperature reaches the heating temperature,and supplies heat to the buried pipes when the water tank temperature is below the heating temperature.The ground-source heat pump-solar energy heating system with hot water supply and heating system only uses solar energy for heating.Simulation results show that the solar energy utilization rate of the solar energy cascade utilization system reaches 53%,but the continuous low water tank temperature severely limits the opening of the solar independent heating mode,and the soil temperature decreases by 0.80℃at the end of the heating season.The solar energy utilization rate of the ground-source heat pump-solar energy heating system with hot water supply and heating system is 34%,and the solar independent heating time exceeds 600 hours.At the end of the heating season,the soil temperature only decreases by0.16℃,and the heating season power consumption is reduced by 13930k W·h,compared to the solar energy cascade utilization system.The study shows that the ground-source heat pump-solar energy heating system with hot water supply and heating system is more suitable for heating buildings based on the climate characteristics of Zhengzhou area.The simulation results show that by supplementing the heat to the buried pipes through the hot water from the district heating network,the inlet temperature of the unit evaporator is increased to above 14°C,and the COP of the system reaches 4.15.Compared with the solar-parallel and solar-series ground source heat pump systems,the system energy efficiency ratio is improved by 5%and 14%,respectively.By optimizing the influencing parameters of the system’s operating performance,it was found that when the tilt angle of the collector is between 30°and 45°,the design flow rate of the collector per unit area is 21 L/m~2,and the volume of the water tank is 80 L/m~2,the total heat collection of the collector is highest and the solar heating time is longest.When the area of the solar collector is 300 m~2,the overall energy efficiency of the system is high,and the system efficiency does not increase significantly with further increases in collector area,while the initial investment of the system becomes increasingly higher.Designing the solar collector area to account for 40%of the building load results in good system energy efficiency and economic performance.