Abstract:
Abstract: Efficient utilization of solar energy is one of the important topics of structural optimization design of solar-greenhouse. And it is significant to the applied researches in this field and particularly to greenhouse energy conservation. Chinese solar greenhouse achieved high efficiency of energy expenditure in the practice. Solar greenhouse played a huge role in the agriculture production particularly in winter in northern China. However, solar greenhouse basically has two major problems. One problem is energy imbalance in the indoor greenhouse between daytime and nighttime. Solar greenhouse has to be ventilated due to the high indoor temperature in the daytime. And it has to be heated at night to protect vegetable from frost damage. According to statistical analysis, the losses to agricultural production brought by freezing injury are almost the sum losses by other stress. At the same time it also limits the efficient utilization of solar greenhouse. This paper introduces new types of solar-greenhouses. The innovation structure is the active energy-storage solar-greenhouse which can active storage heat during the daytime. Theoretical analysis was carried out on the indoor temperature and the regenerative properties of soil-air heat transfer of the active energy-storage solar-greenhouse in this paper. Comparing with the 9m-span normal solar-greenhouse with fixed back-wall, the active energy-storage solar-greenhouse has higher indoor temperature and temperature indicators have improved greatly. Under such experiment condition the active energy-storage solar-greenhouse is more efficient in utilization of solar energy and raising temperature. The indoor temperature in the greenhouse with active thermal storage technology has a great enhancement comparing with the normal type at clear and cloudy day. The mean indoor temperature increased by 1.8 to 2.8℃ in the active thermal-storage back wall solar-greenhouse within Nocturnal period (16:00-09:00) on Jan 15, 2014 (clear day). The average mean indoor temperature increased by 2.2℃. The mean indoor temperature increased by 1.6 to 4.2℃ in the active thermal-storage back wall solar-greenhouse within Nocturnal period (16:00-09:00) on Feb 12, 2014 (cloudy day). The average mean indoor temperature increased by 2.2℃. The average mean indoor temperature increased by 1.0℃ within Nocturnal period (16:00-09:00) on Feb 5, 2014 (snowy day). Synthesized every indexes, the solar-greenhouse with the active thermal-storage back wall may be the most economic structure; it can improve the thermal performance better than the solar-greenhouse with normal back-wall solar-greenhouse with the same height-span ratio. Comparing with normal type, the mean indoor temperature increases is 1.8℃ in the greenhouse with active thermal storage type at this experiment condition. This paper provides the theoretic foundation and experiment results on the efficient utilization of thermal storage and the improvement of greenhouse structure management. A detailed analysis is made for the ISO-surface of 20℃ of the active thermal-storage back wall in the paper. The results show that the effective range of the ventilation length varied from approximately 10m to 15m, while the air channel over 15m in the active thermal storage back-wall has little effect on energy storage performance. The optimum length of the air channel is 15m. The fit curve of the CFD simulation model is identical with the test curve. According to indoor daytime thermal analysis based on an indoor average temperature, this paper presents the influence coefficient of active daytime thermal storage technology and analyzes the significance and skill of solar energy utilization in the design of new solar-greenhouse structure. And it provides the theoretic foundation and experiment results on the efficient utilization of Solar Energy and the improvement of greenhouse structure management.