Passive solar energy utilization: A review of envelope material selection for Chinese solar greenhouses

Chinese solar greenhouses (CSGs) passively utilize solar energy to heat the building for crop production during the winter. The envelope materials are critical to effective solar energy utilization through solar radiation capture, solar energy storage and solar heat conservation. This paper reviews envelope material selections, especially material improvement and development trends of CSG south roof films, thermal insulation covers, north wall materials and north roof materials for maximizing solar energy utilization. Many studies have analyzed the effects of the CSG films and north wall materials on the indoor thermal characteristics. The CSG film selection studies have evaluated the effects of the sun ray transmittance, indoor air temperature and inside crop growth while north wall material studies have analyzed new layered north wall materials in both warm areas and severe cold regions in the winter. Envelope material selection for CSGs in non-cultivated desert regions has also been considered. This paper also reviews issues concerning envelope material selection and gives suggestions for future CSG designs. The CSG material selections for different climate regions in China can serve as references for solar greenhouse designs in other regions of the world with similar climates for efficient solar energy utilization.