The desiccant air conditioning system has multiple advantages (e.g., no use of ozone-depleting refrigerants, highly efficient moisture control, easy regenerative integration) over traditional vapor-compression refrigeration systems, thus increasingly attracting more research interest. Recently, several studies have been conducted that primarily aimed to enhance the overall performance of desiccant air conditioners by innovating new desiccant materials, innovating new system configurations and improving system designs and controls, and integrating different hybrid energy sub-systems technologies. Therefore, this paper provides a comprehensive review of the studies mentioned earlier. The present comprehensive review dealt with several axes: first, an overview of the importance of using desiccant air conditioners and their operations, and performance indicators. Second, a summary statement for desiccant materials that includes: the new innovative desiccant materials and the most important composite desiccant materials. Third, detailed information on the newest innovative designs and configurations of desiccant air conditioning systems and their control systems. Fourth, a detailed statement on the most important hybrid energy sub-systems technologies integrated with desiccant air conditioners. Based on the latest developments in desiccant air conditioning systems, this study presents discussions of urgent issues and recommendations for future work that can help focus necessary efforts to find solutions to critical and pending problems, which lead to further improvements in the overall performance of desiccant air conditioners.

The present study aims to develop an innovative hybrid system powered by solar energy to dry plants and produce pure water, suitable for remote regions that suffer from power problems and the problem of lack of pure drinking water. This was done by integrating a two-stage dryer unit with modified solar still with an air injection system and external condenser to dry plants as well as produce pure water. The integration of the modified solar still and external condenser with the two-stage dryer unit aims to increase the rates of pure water productivity, by injecting the hot humid air that leaves the drying unit into the modified solar still. The performance of the developed and innovative hybrid system was studied theoretically, and the mathematical models were validated using the previously published experimental results. The results presented that, the suggested two stages of the dryer with reheating represent an excellent design that improved the mass of water that was removed from the products by 72.65% as compared to only the first stage of the dryer unit. The proposed innovative developed hybrid system can be produced cumulative pure water with a rate reaching 49.94 liter/day, with an improvement of 592.65% as compared to only modified solar still with air injection. Also, the proposed innovative developed hybrid system represents a good choice which improved the gain output ratio by 177.93% on average as compared to only a two-stage dryer unit with reheating.

The present study aims to innovate small hybrid desalination plants suitable for remote regions working with higher productivity and lower cost of the produced fresh water. To achieve this idea, the small RO desalination plant was combined with the solar still, as well as this innovative hybrid desalination system was combined with the photovoltaic/thermal panel and the evacuated tube solar collector as preheating units to heat the water before it entered the proposed innovative small hybrid desalination plant. To illustrate the characterized of the proposed innovative small hybrid desalination plant, the performance of an innovative small hybrid desalination plant was compared to the conventional small RO desalination plant experimentally under the climate conditions of Tanta city, Egypt. The results presented that the annual permeate water that can be produced from the conventional small RO desalination plant without modification reached 173.74 m3/year, but for the proposed innovative small hybrid desalination plant the annual permeate water that can be produced will be increased to 352.59 m3/year, with an improvement of 102.94%. Also, the economic analysis presented that the cost of permeate water produced from the conventional RO plant without modification reached 0.915 $/m3. But the permeate water cost produced from an innovative small hybrid desalination plant will be reduced to 0.8178 $/m3, saving 10.62%.