The Application of Solar Energy in Thermally Driven Desiccant Evaporative Cooling System

Cooling is needed in many agricultural applications. It would be very nice if air-conditioning can be acquired without paying for energy. In this study, hot water provided by solar water heater was used to drive an adsorption-evaporative chiller. In other words, the sun, which is free, becomes the energy for air-conditioning.

A silicon-gel wheel was utilized to adsorb water vapor and release it when it rotated to regeneration section. The incoming air was dehumidified by the silicon-gel wheel and the dried air was humidified by ultrasonic foggers. The humidifying process brings the evaporative cooling. The leaving air was required to approach saturation as close as possible to achieve the maximum cooling. An air-to-air plate heat exchanger was installed to move some heat from the air after contacting the dehumidifying wheel to the air about to regenerate the wheel. Since the residual heat on the silicon-gel may be transported to the conditioned space and deduct the cooling effect, it was a novel design the have a cooling section between the regeneration and dehumidifying sections. The system was actually built and run with solar water heater. Also, the system ever worked in a small room inside a plant factory to test the cooling effects.

It was found that the addition of cooling section was useful to further decrease the outlet temperature by about 0.5 ℃. The current configuration exhibits a total cooling ability of 5.6 ℃. The operational parameters, such as air flow rates, hot water temperature, and section ratios, were optimized. A design flow for a system of this kind was suggested. It seems like that the system has the potential to cool greenhouse under severe sunshine and make some non-season produce being able to grow.