A versatile solar system for environmental control in greenhouses

A versatile solar greenhouse for the production of a range of out-of-season protected crops has been developed and tested. In this system the solar energy collection and storage unit (solar cell) is separated from a walk-through plastic tunnel by means of a mobile curtain allowing a) ventilation of the greenhouse without affecting the efficiency of solar radiation collection and b) the storage of solar heat to the late hours of the night, only after greenhouse air temperatures drop below a threshold level typical for each crop species. Two prototypes were tested. In the first prototype the walk-through tunnel had an east-west orientation and one solar unit was placed on the south facing side. The second prototype had a north-south orientation and the solar cells were placed on both the east and the west facing sides. The results demonstrated that the first prototype was not suitable for production of trailed winter melons because of shading effects of the southern rows over the northern rows. The systems can be fully automated or it can be hand operated. Trials carried out during the winter of 1995 have demonstrated the efficacy of this new system.