Research on energy-saving operating characteristics of water storage groundwater source heat pump heating system in plant factory
【Abstract】The groundwater source heat pump has high efficiency and environmental protection in greenhouse temperature control. The operating energy consumption could be further reduced if the water storage technology was combined. The energy-saving operating characteristics of a water storage groundwater source heat pump heating system was studied, with the natural light plant factory in Shanghai as an example. The total area was 21 000 m2, of which the heating area was 5 880 m2. The heating system included a groundwater heat exchange system, a heat pump unit, an air conditioning unit, and an energy storage system. Considering the change in electricity price and the change in heat load over time, intermittent operation was adopted for the heating system. At the time of power trough, the heat pump unit was fully open and the energy was stored in the tank while heating. At the peak of power, the heat pump unit was stopped and the system made full use of the heat storage tank for heating. At the time of the level section, reasonable regulation was carried out according to the stored energy of the hot water storage tank and the plant heat load demanded. The typical operating week, February 8–15 in 2017, was selected from the winter heating months. The operation data in the typical week were recorded and analyzed. The outdoor temperature, solar radiation intensity, indoor temperature, indoor relative humidity, and COP (ratio of heat supply to power consumption) of the heat pump were all tested every 5 min in the typical week. The result showed that in winter, the groundwater source heat pump with the energy storage tank heating system could better maintain the indoor temperature at 17 °C–26 °C. The indoor temperature was relatively low at night, but it could meet the growth demand of the crop in winter. The influence of solar radiation was large, and the indoor temperature was basically above 22 °C, even 28 °C. The indoor relative humidity was always 60%–88%, which could avoid indoor high temperature with high humidity. When the system was in stable operation, the heat pump unit COP (coefficient of performance) was about 4.2. February 9, 2017 was selected from the typical week. On the typical day, it was cloudy and the temperature was below 4 °C throughout the day; the solar radiation intensity was 0–160 W/m2 and the average solar radiation intensity was 62 W/m2. The total power consumption of the system was 10 142.71 MJ, and the COP of the system was 3.17. It was further explained for the system characteristics of high efficiency and good stability. Compared with the non-storage ground source heat pump system, the groundwater source heat pump with water energy storage system saved 30.34% of the cost on the typical day. The significant economic benefit of the test system was shown. During the continuous heating period in winter, for the test heating system, the primary energy utilization coefficient was 0.99. Compared with the cold water unit and coal-fired boiler supporting system and chiller and gas boiler supporting system, the energy-saving rate was respectively 81.05% and 74.83%. Different energy heating cost was compared. For the operating cost, the coal, gas, and fuel methods were 1.25, 2.93, and 5.08 times that of the test heating system. For the CO2 emission, it was 2.32, 1.19, and 0.88 times that of the test heating system. Practice showed that the groundwater source heat pump with water energy storage system had good economic and environmental benefits, which could not only reduce the operating costs, but also make full use of geothermal energy and be beneficial to energy conservation.
【Keywords】 thermal energy; pumps; energy saving; natural light plant factory; groundwater source heat pump; water storage; heating system;
(Translated by LIU T)
 Qu YX, Zhang LH, Fang ZH, et al. The study and design on ground water heat pumps [J]. Renewable Energy Resouce, 2002 (6): 11–14 (in Chinese with English abstract).
 Wang JQ. Development and Experimental Study of Water Source Heat Pump Temperature Control Greenhouse [D]. Zhengzhou: Henan Agricultural University, 2003 (in Chinese).
 Van Ooteghem R J C. Optimal Control Design for a Solar Greenhouse [D]. Wageningen: Wageningen University, 2007
 Chai L, Ma C, Ni J. Performance evaluation of ground source heat pump system for greenhouse heating in northern China [J]. Biosystems Engineering, 2012, 111 (1): 107–117.
 Wang JQ, Zhang BL. Experiment of water hea pump in greenhouse heating [J]. Chinese Agricultural Science Bulletin, 2005, 21 (6): 415–419 (in Chinese with English abstract).
 Andrew Chiasson, Design P E. Installation of a new down hole heat exchanger for direct use space heating [R]. Ghc Bulletin, 2005: 20–24.
 Fang H, Yang QC, Wang N, et al. Geothermal technology and its applications in protected agriculture [J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of CSAE), 2008, 24 (10): 286–290 (in Chinese with English abstract).
 Tian FG, He R, Sun TF, et al. Water source heat pump applied to thermoregulation of greenhouse [J]. Northern Horticulture, 2008 (12): 91–93 (in Chinese with English abstract).
 Fang H, Yang QC, Sun J. Application of ground-source heat pump and floor heating system to greenhouse heating in winter [J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of CSAE), 2008, 24 (12): 145–149 (in Chinese with English abstract).
 Chai LH, Ma CW, Zhang XH, et al. Experimental investigation and performance analysis on ground source heat pump system for greenhouse cooling [J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2008, 24 (12): 150–154 (in Chinese with English abstract).
 Zhao JC, Zhang HT, An AM, et al. 地下水地源热泵与水蓄能设计实例的经济分析 [C] // 2006 academic annual conference of HVACR, Hefei, 2006 (in Chinese).
 Chai LL, Ma CW, Zhang Y, et al. Energy consumption and economic analysis of ground source heat pump used in greenhouse in Beijing [J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2010, 26 (3): 249–254 (in Chinese with English abstract).
 Cao WL, Cheng X. Beneficial analysis of the application of water source heat pump in sunlight greenhouse [J]. Agriculture Science & Technology Equipment, 2010 (4): 38–39.
 Chai LL, Ma CW, Yuan XY, et al. Performance analysis on ground source heat pump cooling system based on energy research [J]. Transactions of The Chinese Society for Agricultural Machinery, 2009, 40 (2): 146–150 (in Chinese with English abstract).
 Mehmet Esen, Tahsin Yuksel. Experimental evaluation of using various renewable energy sources for heating a greenhouse [J]. Energy and Buildings, 2013, 65: 340–351.
 Chai LL, Ma CW. Performance and carbon emission analysis on glass-covering greenhouse heating with ground source heat pump technology [J]. Transactions of the Chinese Society for Agricultural Machinery, 2012, 43 (1): 185–191 (in Chinese with English abstract).
 Sun WT, Zhang Y, Yang QC, et al. Thermodynamic analysis of active heat storage-release associated with heat pump heating system in greenhouse [J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2014, 30 (14): 179–188 (in Chinese with English abstract).
 Bartzanas T, Tchamitchian M, Kittas C. Influence of the heating method on greenhouse microclimate and energy consumption [J]. Biosystems Engineering, 2005, 91 (4): 487–499.
 Cai J. Research on Water-source Heat Pump Control System of Greenhouse based on CFD [D]. Hangzhou: Zhejiang University of Technology, 2010 (in Chinese with English abstract).
 Wu ML, Chen YF, Li Q, et al. Frequency transformation and its validation of ground source heat pump system based on grey prediction [J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2016, 32 (16): 183–187 (in Chinese with English abstract).
 Qian K, Zhang Q. Economic analysis of ground-source heat pump combined with water energy storage system [J]. Refrigeration and Air-conditioning, 2013, 13 (7): 96–102 (in Chinese with English abstract).
 Li C, Yu YF. Design and research on optimum distribution of the system of ground source heat pump and energy storage [J]. Power & Energy, 2011, 32 (5): 413–417 (in Chinese with English abstract).
 Sun XJ, Shi HX, Chen HZ, et al. Ground source heat pump with storage system of the plant factory [J]. Energy Conservation Technology, 2015, 33 (2): 125–130 (in Chinese with English abstract).
 Lu H. Study on Ground-Source Heat Pump Combined with Water Storage Air-Conditioning System [D]. Jinan: Shandong University of Architecture, 2012 (in Chinese with English abstract).
 Qi YS, Yue YL, Liu TY. Application analysis of combined ground-source heat pump and water energy storage systems [J]. Heating Ventilating & Air Conditioning. 2010, 40 (5): 94–97 (in Chinese with English abstract).
 Zuo R, Jiang LL, Gao W, et al. Application of geothermal technology in greenhouse heating [J]. Journal of Anhui Agricultural Sciences, 2009, 37 (13): 6139–6140 (in Chinese with English abstract).
 Edward Foulds, Muditha Abeysekera, Wu Jianzhong. Modelling and analysis of a ground source heat pump combined with a PV-T and earth energy storage system [J]. Energy Procedia, 2017, 142: 886–891.
 Emanuele Bonamente, Andrea Aquino, Franco Cotana. APCM thermal storage for ground-source heat pumps: Simulating the system performance via CFD approach [J]. Energy Procedia, 2016, 101: 1079–1086.
 Hüseyin Benli. Energetic performance analysis of a ground-source heat pump system with latent heat storage for a greenhouse heating [J]Energy Conversion and Management, 2011, 52 (1): 581–589.
 Hu T, Zhou Q, Xiao RZ, et al. An online optimal operation control of ground source heat pump system with water heat storage [J]. Acta Energiae Solaris Sinica, 2018, 39 (2): 496–503 (in Chinese with English abstract).
 LüYQ, Fu YZ. Experimental research of performance for refrigation intermittent operation in summer of GSHP system [J]. Acta Energiae Solaris Sinica, 2018, 39 (2): 453–460 (in Chinese with English abstract).
 Li Huai, Xu Wei, Yu Zhen, et al. Discussion of a combined solar thermal and ground source heat pump system operation strategy for office heating [J]. Energy and Buildings, 2018, 162: 42–53.
 Yang Weibo, Zhang Heng, Liang Xingfu. Experimental performance evaluation and parametric study of a solar-ground source heat pump system operated in heating modes [J]. Energy, 2018, 149: 173–189.
 LüJunxin, Wei Zhang, Zhang Jiaqi. Running and economy performance analysis of ground source heat pump with thermal energy storage devices [J]. Energy and Buildings, 2016, 127: 1108–1116.
 Liu Z, Qin CK. Gas consumption of greenhouse heating in Shanghai [J]. Chengshi Ranqi, 2016 (10): 9–14 (in Chinese with English abstract).