Advanced Optical Materials for Sunlight Control in Greenhouses

The increasing demand for efficiently growing vegetation in greenhouses requires continual improvement of the control of the growth environment experienced by the plants. The single most important factor in maximizing the crop's growth is the quantity, quality, and geometrical distribution of radiation intercepted at every moment. Few available greenhouse coverings are capable of responding to changes in sunlight conditions by themselves, limiting the grower's control: they must use additional technologies, including screens, artificial lighting, heating, and cooling. This review considers existing efforts in providing adaptable greenhouse covering systems and advanced optical materials for controlling the color, intensity, and/or distribution of sunlight transmitted into greenhouse-like structures by describing existing static materials and their responsive equivalents. This work also offers speculation on potential applications of other light-control elements, mostly designed for use in the urban environment that can be adapted for greenhouse use in the future.