Regulation for energy-saving operation of energy supply system in plant factory with energy-storage ground-source heat pump
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Abstract
Groundwater source heat pumps have high efficiency and environmental protection in greenhouse temperature control. Most importantly, the operating energy consumption can be further reduced if the water storage technology were combined. Although the energy storage type ground source heat pump plant factory energy supply system avoids the problems of low primary energy utilization and serious pollution in traditional fossil energy supply, it currently lacks long-term operating experience. This study takes Shanghai Chongming Natural Light Plant Factory as an example to optimize the energy-saving operation of the energy storage groundwater source heat pump energy supply system. The total area of the plant factory is 21 000 square meters, which is divided into three areas A, B and C. The 7 greenhouses in area A use an energy storage groundwater source heat pump air-conditioning system with an area of 5 880 square meters. The greenhouse uses two cylindrical concrete storage tanks, of which the volume of the thermal storage tank is 400 cubic meters and the diameter is 7.65 meters; the volume of the cold storage tank is 600 cubic meters and the diameter is 9.29 meters. The plant factory has 2 hot water wells and 2 cold water wells. In winter, water was drawn from the 2 hot water wells and passed through a convection plate heat exchanger to exchange heat with the cold water flowing from the cold water tank. The low-temperature water after the heat exchange was pumped back by pressure fill 2 cold water wells. Under typical operating conditions in winter, the output temperature of hot water wells was basically maintained at 16-20℃.The inlet water temperature of cold water wells remained stable at about 7℃, and the pumping flow of hot water wells was maintained at about 40 m3/h. According to the statistics of the operating parameters of the heat pump in the first quarter, it could be concluded that the four output water temperatures and input water temperatures of the heat pump remain stable, and the heat pump operated normally during the heating season. The power consumption of the heat pump in the first quarter was 208 559.5 kWh. Among them, the power consumption in January was 83 525.9 kWh, February was 76 673.3 kWh, and March was 48 360.3 kWh; the total heat output to the greenhouse and hot water tank was 3 542.7 GJ, of which 1 445.9 GJ was output in January and 1 258.6 GJ was output in February. In March, the heat output was 838.2 GJ; in the first quarter, the total heat pump operation was 1 322.8 h, including 557.7 h in January, 454.4 h in February, and 310.7 h in March. After research, there are three unreasonable operating conditions of the system: A. The heat pump continued to supply heat when the plant factory heat load s negative; B. The heat pump output excessive heat to the hot water storage tank; C. The heat pump was still running during peak hours. After optimization and control, to avoid the A operation, the heat pump could finally reduce the output energy by 21.55 GJ in the first quarter, which could reduce the power consumption by 1 012.50 kWh, which could save 747 yuan when converted to electricity price; to avoid the B operation, set the upper limit of hot water charge rate at 85% in the first quarter, which can reduce the output of 97.2 GJ energy under the premise of ensuring that the heat pump is fully powered by the plant factory; to avoid the C operation, to avoid the C operation, assuming that the heat pump was used during the price trough, the total output energy of the heat pump was unchanged. Transferring the heat of the heat pump 140.25 GJ in the first quarter to the parity stage output could save 5 530 yuan, and the total power at this time was 8 654.07 kWh, at this time, the total amount of electricity was 8 654.07 kWh. By optimizing the operation process of the natural light plant factory's energy supply system, energy saving and consumption reduction can be achieved, and economic operation can be achieved.
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