Abstract
Under harsh weather conditions, closed transplant production systems (CTPS) are currently used to produce high quality transplants under artificial lighting. More than 70% of the electric energy consumed in the CTPS is for lighting. This article presents a simulation study to examine the possibility of using an alternative closed solar house, with radiation filtering roof, for transplant production in hot sunny regions to replace the artificial lighting in the CTPS with sunlight. The sidewalls of the house were insulated as in the CTPS and the roof was transparent, and made from polycarbonate hollow-channeled structure. There was a liquid radiation filter (LRF) (1.5% CuSO4-water solution) flowing in a closed loop through the roof channels to absorb the solar heat load (i.e., the near infra-red radiation, NIR: 700-2500 nm) and transmit the photosynthetically active radiation (PAR: 400-700 nm) for plant growth. The LRF inlet temperature was assumed to be 25 degrees C to prevent vapor condensation on the inner surface of the cover. The evapo-transpired water vapor was removed immediately to maintain the relative humidity inside the house at 70%. The results proved that this technique can offer an appropriate air temperature inside the house less than outside air temperature by around 8-10 degrees C in hot summer days, and the integrated electric energy consumption during the production period was estimated to be around 43% of the CTPS consumption.