Energy-saving procedures for thermal and luminous environment controls in plastic greenhouses: A review

World food production is facing great demand due to environmental degradation and population pressure. Plastic greenhouses with the advantage of convenience and economy are widely distributed all over the world to maintain agricultural productivity. Indoor luminous and thermal environments are crucial for crop growth in plastic greenhouses but also require a high amount of energy. Therefore, this paper comprehensively summarizes the current low-energy-consumption strategies to control the luminous and thermal environment of plastic greenhouses and provides a reference for the development of modern plastic greenhouses. Firstly, the formation process of the indoor luminous and thermal environment was theoretically analyzed. Then, the regulation strategies for indoor luminous environments were summarized. The optical properties of the covering material should ensure adequate photosynthetically active radiation transmittance to meet the indoor luminous demand throughout the year. Also, passive and active heating strategies in cold weather, as well as main cooling measures in hot weather, were discussed. The study revealed that current active strategies suffer from high energy consumption, low energy efficiency, and poor economics. Therefore, utilizing renewable energy sources is essential for greenhouse development. Though water conservation is always a major issue, integrating traditional evaporative cooling with radiative cooling shows great potential. This paper outlines state-of-the-art research on greenhouse thermal and luminous environments and points out the existing challenges that could provide important guidance for future studies.