Solar radiation manipulations and their role in greenhouse claddings: Fluorescent solar concentrators, photoselective and other materials

Since only Photosynthetic Active Radiation (PAR) is valuable for plants, modifications of solar radiation which enters greenhouse interior space can provide several advantages. These modifications can be achieved by using specific kinds of cladding materials. The present paper refers to some claddings such as those which modify Red/Far-red (R/FR), Blue/Red (B/R), Blue/Far-red (B/FR) ratios; fluorescence solar concentrators; passive optical means; desalination roofs; anti-condensation materials; covers which diffuse sunlight and other. The authors of the present investigation, present representative studies from the literature and make criticism on each cladding category. The results reveal that there are some types of covers which have the potential to provide benefits to the greenhouse, provided these are used in a cost-effective way and several critical factors are taken into account. Moreover, the development of energy efficient greenhouses and the application of renewable energy technologies such as solar energy systems are important issues. Finally, some additional considerations regarding cladding degradation, greenhouse microclimate in conjunction with the covers etc., provide a more complete overview of the studied issues.