Theory and application of sustainable energy-efficient solar greenhouse in China

China has been a global leader in energy-efficient solar greenhouse technology thanks to its incredibly low energy input since its inception. This energy-efficient facility provides an important pathway for the sustainable development of agriculture. A comprehensive explanation of the design principles, development process, and production practice effects of energy-efficient solar greenhouses in China by integrating more than 40 years of research on greenhouse structure and environmental regulation was elaborated in this paper. To enhance the insulation and heat storage capabilities of first-generation energy-efficient solar greenhouse, our team proposed the idea of insulation ratio and optimized this parameter. In this greenhouse, the temperature difference between indoors and outdoors reached 25 °C, and production of vegetables for overwintering could be accomplished south of 40.5 °N. Then, a reasonable light transmittance during the minimum lighting period on the winter solstice of solar greenhouse was proposed, and the greenhouse’s thermal insulation and storage capacity were further enhanced. Consequently, a second-generation energy-efficient solar greenhouse was developed, capable of producing crops in an outdoor temperature as low as –23 °C annually. Ultimately, the third-generation energy-efficient solar greenhouse was proposed, which greatly increased the solar energy interception capacity of solar greenhouse, along with the theory and application techniques of reasonable solar energy interception. The indoor and outdoor temperature difference of this greenhouse reaches 35 °C. It has achieved the annual production of warm fruits and vegetables without heating in the 43 °N region. China’s solar greenhouse industry has grown significantly in size during the course of the aforementioned research, generating significant economic and social value.