Investigation of Greenhouse Solar Dryer in Passive Mode

In the present craze for developing solar energy-based utility systems, several research studies have been carried out on greenhouse solar crop drying system. This area of exploration is attaining a higher interest as most of the researcher’s main objective is to obtain a system, which could provide the highest average temperature inside the greenhouse dryer and curtail the drying time. Moreover, discovering new and more economical forms of a heat storage system is also of great interest. Keeping this in mind, a greenhouse solar dryer (GSD) with an even roof pattern and passive mode has been developed and is tested under different design modifications inside the dryer. Combinations of an insulating north wall (outer part), reflecting north wall (inner part), and insulation at the base (lower part) with (i) black PVC sheet at the base (Set 1) (ii) reflecting mirror at the base (Set 2) and (iii) black-painted plywood at south face and base (Set 3) are used for design modification of the dryer. Each set has been tested for two days, from 10 a.m. to 4 p.m. It has been found that ‘the system’ with black-painted wood at the base and south face is more suitable for drying than the other two systems. The inside greenhouse air temperature is found to be maximum in the case of Set 3 configurations. The maximum temperature of greenhouse air achieved is 73.8 °C with the Set 3 configuration, which is approximately 7.15 and 35.15% higher than Set 1 and Set 2, respectively. A maximum base temperature of 76.1 °C is obtained at the base for Set 3, which is almost 14.09 and 18.72% higher than Set 1 and Set 2. The coefficient of performance (COP) value has been found to be maximum for Set 3 with a value reaching 0.94.