Wang et al. / J Zhejiang Univ SCIENCE B 2006 7(4):279-282 279 Journal of Zhejiang University SCIENCE B ISSN 1673-1581 (Print); ISSN 1862-1783 (Online) www.zju.edu.cn/jzus; www.springerlink.com E-mail:
[email protected] Performance of underground heat storage system in a double-film-covered greenhouse* WANG Yong-wei1, LIANG Xi-feng2 (1Department of Biosystem Engineering, Zhejiang University, Hangzhou 310029, China) 2 ( School of Mechanical and Electrical Engineering, China Jiliang University, Hangzhou 310018, China) E-mail:
[email protected];
[email protected] Received Aug. 31, 2005; revision accepted Nov. 13, 2005 Abstract: An underground heat storage system in a double-film-covered greenhouse and an adjacent greenhouse without the heat storage system were designed on the basis of plant physiology to reduce the energy consumption in greenhouses. The results indicated that the floor temperature was respectively 5.2 °C, 4.6 °C and 2.0 °C higher than that of the soil in the adjacent reference greenhouse after heat storage in a clear, cloudy and overcast sky in winter. Results showed that the temperature and humidity were feasible for plant growth in the heat saving greenhouse. Key words: Greenhouse, Underground heat storage system, Performance of heat storage, Energy saving doi:10.1631/jzus.2006.B0279 Document code: A CLC number: S62 INTRODUCTION Temperature is one of the most important greenhouse climate variables influencing the growth, crop production and product quality of plants. It is a challenge to improve the economic potential by controlling ambient air and soil temperature in greenhouses. However, protected horticulture is an industry with high energy consumption. The UN reported that energy consumption for heating greenhouses amounted to 35% of the production cost (Pan et al., 1999). In Europe the energy used for heating and cooling of greenhouse represents approximately 1.5% of the total energy consumption (Santamouris et al., 1995; 1996). It is obvious that the cost for heating greenhouses in winter is one of the primary components of the production cost limiting the development and economic potential of protected agriculture. The underground heat storage system in greenhouses can store much solar energy underground and * Project (No. 20050912) supported by the Education Department of Zhejiang Province, China retrieve it from the floor when needed. This was applied for conditioning greenhouses and livestock buildings with favorable effects on energy saving (Baxter, 1992). However, the storage unit in the existing underground heat storage systems in greenhouses was insulated on the sides and the top but not on the base, so the efficiency of the heat storage system was very low. The poor performance was mainly