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| Coefficient of performance of solar heat pump water heater with energy storage |
| 1.School of Energy and Mechanical Engineering, Nanjing Normal University, Nanjing, Jiangsu 210042, China; 2.School of Energy and Environment, Southeast University, Nanjing, Jiangsu 210008, China) |
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Abstract To solve the problem that solar heat pump water heater was prone to be affected by weather, a novel water heater integrated with collection, storage and evaporation was proposed. The principle, characteristics, operating modes and structure of the collector-storage-evaporator system were investigated. Using phase change material of decanoic acid to store solar radiation in sunny days as low-temperature source, hot water was produced at night or in continuous rainy days. Thermal efficiency of heat pump system was increased significantly, and the operating unstableness of the heat pump system caused by interval solar energy was also solved. Experiments under different conditions and operating modes in spring were conducted, and the coefficient of performance (COP) of the system was analyzed. The results indicate that COP of this novel solar heat pump water heater with energy storage is higher than that of ordinary solar heat pump water heater at the same weather condition. The average COP of this system is 7.56 with maximum of 8.9 for average solar radiation of 592 W·m-2. COP can also reach 6.4 even at night,which means that weather has slight influence on COP.
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2011, Vol. 32 
