Conventional air conditioning systems apply an evaporation-condensation cycle in order to cool the humid air and thus remove the water content from the air stream. The condensation process which is carried on by a compressor utilizes a significant amount of energy. An alternative to this procedure is moisture absorption by chemical materials known as desiccants. The desiccation process is reversible by heating the desiccant substances called as regeneration. The absorption-regeneration cycle consumes less energy than evaporation-compression cycle. Solid desiccant materials can be packed in or impregnated on corrugated sheets within a wheel or a cartridge to act more convenient in an air conditioning system. The solid desiccant wheel rotates regularly in this system while a part of it is absorbing humidity from countercurrent humid air stream and the other part is regenerating against heat stream.

Thermal energy exploited from solar heater panels has been recently assisted in a desiccant wheel air conditioning demonstration project in Kish Island, Persian Gulf, Iran. “This demonstration unit was completed in late 2008 and successfully tested afterwards” said Pejman Izadkhast, M.E., the project manager, “simple solar water heating panels by total surface of 48m² were utilized to supply required heat for solid desiccant regeneration. The hot water moves through a water-to-air heat exchanger and supplies the hot air stream for desiccant regeneration”. Interior air conditioning in very humid climate Kish Island located in southern Iran is a subject of great interest because the large number of inhabitants and passengers in this outstanding tourism spot creates a high energy demand for air conditioning which in turn imposes a great load to the independent power grid in the island. The long sunny hours in Kish Island (about 3100 hours per year) makes it attractive for exploitation of solar energy.

This project was implemented in order to evaluate the performance of solar thermal assisted solid desiccant air drying system in practical conditions of Kish Island’s environment and its influence on energy saving. The nominal capacity of this demonstration unit is 5RT (60,000Btu/hr or 17.58kW) and employs primary heat exchanger, air humidifier, rotary desiccant wheel, regenerative heat exchanger, hot water tank, water pump, solar collectors, secondary heat exchanger, evaporator, condenser, supply fan and regeneration fan. The process flow chart has been demonstrated in the following figure:

Performance monitoring of demonstration system during summer 2009 revealed some 32% reduce in electricity consumption comparing to conventional home air conditioners” declared Pejman Izadkhast, our next step is to compare its performance with absorptive chillers.

The next figure demonstrates the 3D configuration of system.

The project was collaboratively supported by New Energies Organization of Iran (SUNA) and Niroo Research Institute (NRI) which performed investigations, conceptual and detailed designs, procurement, assembling, installations and test operations. Installation of this demonstration plant was carried on in administrative building of Kish Island’s Water and Power Organization. The following picture shows the completed system.