Performance experiment on lighting and thermal storage in tilting roof solar-greenhouse

Abstract: The arch roof structure has been widely used in designing solar-greenhouse to efficiently utilize solar energy. The arc structure of solar-greenhouse roof in solar-greenhouse lighting was investigated in this study. The experiment results indicated that the light penetration is essentially same for different arch roof structures under the same ratio of rise to span. The patterns of arch structure and the light transmittance performance were further investigated inside the solar-greenhouse. The linear roof had better performance under the same height-span ratio. We designed a tilting roof solar-greenhouse based on the theoretical analysis. The inclination angle of roof could be adjusted for different demands of daylight under different climate conditions. Its structure is simple, economical and efficient. All studies in this paper are mainly aimed at what is called a "solar-greenhouse with active day lighting technology".This paper describes three types of solar-greenhouses: one innovation structure with the tilting roof solar-greenhouse, and two normal structures with fixed roof angle and 8m-span and 9m-span solar-greenhouse, respectively. Compared to the normal solar-greenhouse with fixed roof angle, the tilting roof solar-greenhouse has new form roof with adjustable tilt angle. The dip angle of the tilting roof-greenhouse's lighting surface can be adjusted based on different solar altitudes. The dip angle of the tilting roof-greenhouse's lighting surface is increased if the solar altitude is decreased. In this paper different experimental data was analyzed using the lighting analysis method. The temperature and the solar irradiance changing rate indoors and outdoors of solar-greenhouse were used to develop a new structural model of high-performance greenhouse.The tilting roof solar-greenhouse is more efficient in utilization of solar energy and raising temperature. Illumination and indoor temperature in the greenhouse with active tilting roof technology has a great enhancement compared with normal structure. The average increasing rate of lighting performance was 41.75%, e.g. 69.55W/m2 in the tilting roof solar-greenhouse during 09:00 am-16:00 pm. The solar-greenhouse with adjustable tilt angle was the most economic structure based on synthesized indexes. This structure increased the day-lighting performance by 25.05%, e.g.38.99 w/m2, compared with the solar-greenhouse with fixed roof angle and with the same height-span ratio. Compared with the normal type with fixed roof angle, the mean indoor temperature increased is 3.1℃ in the greenhouse with active tilting roof at the heat preservation period.This paper also discusses the influence coefficient of active day lighting technology, analysis the significance and skill of solar energy utilization in the design of new solar-greenhouse structure according to indoor day lighting analysis of indoor average temperatures. It is expected that experiment results and analysis will support the efficient utilization of Solar Energy and the improvement of greenhouse structure management.