Are smart glasses with switchable optical properties the future greenhouse covers for high value crops?

Summary

Within the public-private collaboration project Smart Materials, electrochromic glasses (EC glass, able to instantaneously switch light intensity or scattering) were evaluated on their potential for production of high value ornamental crops that are assumed to benefit from relatively low sunlight levels. Growers use shading screens or temporary coatings on glass during the summer, which react slowly to changing outside light conditions. EC glass allows timely light intensity control and therefore more constant light conditions. Experiments were carried out with pot Anthurium and Schefflera. Research questions were: Is EC glass able to control light intensity to a constant level with changing outside sunlight conditions? Does this improve crop growth and quality? The light levels were well controlled under EC glass. As a result, the plants were exposed to a higher light sum attained by more constant light, less peaks on sunny days and more light on clouded days. However, this did not translate into faster growth, more flowers nor better plant quality. The achieved light control advantage by the EC glass was counteracted by the thermal radiation behavior of the glass: light was absorbed, which lead to high glass temperatures, thus high leaf temperatures. That lead to stomata closure and lower photosynthesis efficiency during sunny periods. More research is needed to evaluate the potential of smart glasses as greenhouse covers for high value crops.