Solar Radiation Transmission in Mediterranean Plastic Greenhouses

Crop bioproductivity is directly related to the available solar radiation. Therefore, optimising the solar radiation transmission is a key point for greenhouse growing in the Mediterranean area, especially during the low radiation season (autumn and winter). A typical characteristic of the Mediterranean coastal areas, where greenhouses have spread notoriously in the last decades, is the high number of clear days, when direct solar radiation prevails over diffuse radiation. A direct solar radiation transmission model (TRADINMED) for plastic multispan greenhouses of diverse roof slopes was developed and validated with scale-models and commercial greenhouses. This paper presents the results of the simulation of solar radiation transmission in the winter solstice for three different latitudes of the Mediterranean area (30 degrees N, 37 degrees N, 45 degrees N), and diverse roof slopes and orientations, in low-cost plastichouses (parral type). Roof slope, orientation and latitude induce relevant differences in the solar radiation transmission. Therefore, previous simulations can be very helpful for greenhouse design and construction.