# Review of Dew Point Evaporative Cooling Technology for Air Conditioning Applications
## 4 Dew Point Evaporative Coolers Research
### System Applications
#### 4.4.2 Desiccant Systems
[53] determined an annual energy consumption of a hybrid system (composed of desiccant wheel and indirect evaporative cooler), in comparison to direct expansion conventional system. The hybrid system shows a significant energy saving, up to 46.8%, which was shown in simulations results. [PERSON] et al. [54] studied a liquid desiccant dehumidifier cooperating with a regenerative indirect evaporative cooler. Energy for the regeneration process was tapped from solar collectors. The results showed that the optimal extraction for this system ratio is 0.3. Depending on inlet air conditions, this system achieves an energy saving ratio from 22.4% to 53.2%. [PERSON] et al. [55] proposed a hybrid membrane, liquid desiccant dehumidification, and dew point evaporative cooling system. It consists of a cross-flow membrane liquid desiccant dehumidifier and a counterflow dew point evaporative cooler. They published the experiment results and developed a mathematical model of the system. [PERSON] et al. [56] investigated the performance of a two-stage solar desiccant air-conditioning systems equipped with dew point indirect evaporative coolers (DPIEC) for hot and humid climates. They used multistage dehumidification with two desiccant wheels and cooling processes with air-to-air and DPIEC to improve the average system COP which reached 1.77 during electricity load peak hours. They found out that it is possible to minimize required solar heating during midday at noon. [PERSON] et al. [57] experimentally analyzed a solar-assisted solid desiccant cooling system integrated with one DPIEC exchanger. The analysis of the system was performed for different days of the summer season. The COP of this system varies between 0.65 and 1.17. [PERSON] et al. [53] focused on determining mainly the annual electricity consumption and seasonal coefficient of performance of a hybrid air conditioning system with a desiccant wheel and indirect evaporative cooler for 6 climate zones. The simulation results show that the system analyzed shows significant energy savings up to 46.8%, compared to a typical direct expansion system. Due to the fact that sorption systems achieve low COPs, the researchers are constantly looking for opportunities to increase the efficiency of desiccant systems. In the field of desiccant cooling systems, the benefits of removing the heat of adsorption were noted. Lit  
Figure 5: Typical solar desiccant cooling system scheme [8]. erature studies show that it can be performed by cooling the air before the dehumidification process (see Figure 6) [58] or by cooling the desiccant [59]. [PERSON] et al. [60] developed the performance of a silica gel/polymer composite desicant wheel regenerated by the heat released from the heat pump. They proposed a desiccant air conditioning system with the evaporator before the desicant wheel, to provide the initial dehumidification and pre-cooling of the ambient air. The results show that under the same conditions, a composite desiccant in a heat pump system outperformed the silica-gel-based system by 130% and consumed less power than traditional desiccant systems. [PERSON] et al. [61] studied the design and analyzed the performance of a novel tube-in-shell internally water-cooled desiccant wheel. Experiments were performed in order to validate the mathematical model. The results show that isothermal performance of the desicant wheel can be achieved. Moreover, the improvement of a dehumidification process is significant, equaling 48% as compared with a conventional adiabatic desiccant wheel using a super-absorbent polymer as the desiccant material in a desiccant wheel. [PERSON] and [PERSON] [62] presented an air conditioning system integrated with a desiccant wheel and high-temperature chilled water from a natural cold source. They developed the mathematical model of the system, while system components were validated experimentally. The system shows more efficient energy performance than a conventional solar desiccant wheel air conditioning system in high, moderate, and low humidity climate conditions.