| Ground Source Heat Pump has been used more and more commonly in the world forits high efficiency and environmental benefit. However, in the areas of hot summer&coldwinter, the cooling load is usually much larger than the heating load, and application of thetraditional ground source heat pump will increase the ground’s temperature, this will tendto the decrease of the system efficiency. To solve this problem, a supplemental heatrejecter, such as cooling tower or shallow pond or water cooler and so on, can be used inthe ground source heat pump. That is the so called hybrid ground source heat pump system.In this study, the hybrid ground source heat pump system use the cooling tower as asupplemental heat rejecter.In the hybrid ground source heat pump system, the cooling tower may be connectedin series or parallel with the ground heat exchanger, and the system performances could bedifferent. In this paper, we choose an office building in Wuhan to simulate the twodifferent form of hybrid ground source heat pump based on TRNSYS. In the parallelsystem, the time based method was used as the control strategy, and in the series systemwe used the temperature difference based control strategy. The simulation result show thatthe performance of the parallel system is better than the series connection.The ground heat exchanger and cooling tower could be run separately in the parallelsystem, Intermittent operation between ground heat exchanger and cooling tower isbenefit for the ground temperature to recovery. We considered how the length ofintermittent operation time affects the system performance. Simulation results show thatthe shorter of intermittent operation time, the less energy consumption and higherefficiency of the heat pump in the cooling season, and the lower efficiency of the heatpump in the heating season, and the ground temperature is lower with the shorter ofintermittent operation time.Analysis the cooling load and meteorological parameter in Wuhan, we found that, inthe beginning and end of the cooling season, the cooling load is small, and the wet bulbtemperature is low. In this time, use cooling tower as the only cooling source could notonly increase the efficiency of the cooling tower, but also to retain the cooling capacity of the ground heat exchanger. In the middle of the cooling season, the load is larger, the timebased method was used to control the system, the cooling capacity of the ground heatexchanger could be worked. The simulation result showed that, the operation methodwhich considering the characteristics of the cooling load could save more energy byincreasing the heat pump’s efficiency, and in this control strategy, the ground temperaturecould recovery well. |
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