Abstract
Abstract. Chinese Solar Greenhouses (CSG) rely solely on solar radiation for heating to achieve energy savings. However their land utilization efficiency is only 30% to 48%. A new type of solar greenhouse was designed where an active heat storage-release system (AHS) was added to replace the north wall and the greenhouse ridge was north-south oriented. In this way, the spacing between greenhouses can be shortened and the land utilization efficiency can be increased up to 91%. To further improve the thermal performance of the new type of greenhouse, a heat pump (HP) was incorporated in the AHS system to form a new design defined as AHS-HP. The HP was used to regulate the water temperature in three storage tanks that served as the heat reservoir for the AHS system. By regulating the water temperatures, the heat collection and releasing can be done more efficiently than without HP. Two new types of greenhouses located in Beijing, one with AHS-HP (experimental greenhouse) and one without (reference greenhouse), were compared in terms of indoor air temperature, relative humidity (RH), and electricity consumption. Nighttime air temperature in the experimental greenhouse was increased from 2°C to 4.5°C, on average, compared with the reference greenhouse. The coefficient of performance (COP) of the HP was 4.8 to 6.3 during the daytime and 3.1 to 4.9 at night. The COP of the AHS-HP system was 3.2. The average daily electricity consumption of the AHS-HP is 0.04 kWh m-2 day-1. The low cost AHS-HP has the potential to be applied in solar greenhouses if it is properly designed and operated.
Published Version
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