Light and temperature performance of energy-saving solar greenhouse assembled with color plate

Abstract: The Chinese energy-saving solar greenhouse (CESG) is a special type of greenhouse without heating system, originated in Anshan, Liaoning province. In China, during the mid-1980s, the CESG was composed of the front house roof (for lighting), north wall, east-west gable, back roof (for heat storage and heat preservation), and outside heat preservation covering materials. The applied area of CESG in China reached 928 thousand hm2 by 2012，which has completely resolved the problem on the year-round vegetable supply, especially in winter in north China. However, the CESG also faces many problems such as uneven distribution of light and temperature in greenhouse, difficulties to achieve automatic control of outside heat preservation covering materials, poor ability of rainproof, snow-proof, wind-proof and fire-proof, and destruction of lots of arable land for greenhouse construction of earth wall and brick wall.To resolve the above problems, a new type of energy-saving solar greenhouse assembled with heat preservation color plate (CPSG) was developed in Lingyuan (latitude 41?20'N, longitude 119?31'E), Liaoning province, China from 2010 to 2012. The light and temperature performances were studied from January to March, 2013.The CPSG was the large scale arched structure with a span of 12 m, a ridge height of 5.5m, a length of 65m, a front roof lighting angle of 41.5°, a front roof covering materials of polyolefin film. The skeleton structure was semi-circular arc, which slide to opening or closing the heat preservation covering materials of rock wool color plate outside, and to move the opening or closing of the rock wool color plate east gable (in the morning) and west gable (in the afternoon) respectively. As a result, the CPSG not only resolved the problem of rain-proof, snow-proof, wind-proof and fire-proof for Chinese traditional solar greenhouse, but also brought about the accurate operation of outside heat preservation color plate. Furthermore, this type of greenhouse adopted water-recycle heat storage-release system (WHSS) and air-underground heat exchange storage-release system(AHESS). WHSS is running 5.5h/d on sunny day and the solar energy storage capacity is 1200kJ/m2 (greenhouse area), which made the greenhouse temperature increase 7-8℃ in winter night. At the same time, solar energy accumulation for AHESS is 221kJ/m2, which shows that two heat storage-release systems may replace the heat storage-release function of earth wall and brick wall, and then to lay the foundation for assembled construction of the CESG. Compared with the traditional Liaoshen Ⅲ type solar greenhouse, CPSG increases 5.3% of the lighting quantity by enhancing 16.3° in the front roof lighting angle. When the outside nighttime air temperature was -25.8℃, the nighttime air temperature in the CPSG reaches more than 13℃ with an increase of 2.3-3.5℃, the temperature difference between inside and outside reaches 39.1℃. In addition, the CPSG has larger cultivation space, better lighting quantity, more rapid warming up, and more even distribution of light and temperature in the north-south direction or the east-west direction, resulting in a unanimous plant growth. In summary, the study shows that new type of CPSG integrates the advantages of the large multi-span greenhouse and Chinese traditional solar greenhouse, heightens the efficiency of light energy utilization, reduces the labor intensity, realizes the accurate control of heat preservation covering materials, will provide a new effective way for automation and modernization of solar greenhouse in China.