# Review of Dew Point Evaporative Cooling Technology for Air Conditioning Applications
## 5 Discussion and Summary
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**System** & **Region** & **Experiment** & **Numerical** & **Performance** & **Reference** \\ \hline \multirow{3}{*}{(A) DPIEC} & \multirow{3}{*}{Arab Gulf cities} & \multirow{3}{*}{no} & \multirow{3}{*}{yes} & \(\varepsilon^{\text{tWB}}\!=135\%\) & \multirow{3}{*}{[29]} \\  & & & & & \(\varepsilon^{\text{tDP}}=100\%\) & \\  & & & & \(\text{COP}_{el}^{\text{max}}=20\) & \\ \hline \multirow{3}{*}{(A) DPIEC} & e.g., Riyadh, & & & \(\overline{\varepsilon}^{\text{tDP}}=44\%\) & \multirow{3}{*}{[36]} \\  & South Arabia & & & \(\text{COP}_{el}^{\text{max}}=60\) & \\ \hline \multirow{3}{*}{(B) DPIEC (with heat and  mass exchanger)} & e.g., Riyadh, & & & \(\varepsilon^{\text{tWB}}=115\%\) & \multirow{3}{*}{[28]} \\  & South Arabia & & & \(\varepsilon^{\text{tDP}}=68\%\) & \\  & & & & \(\text{COP}_{el}^{\text{max}}=50\) & \\ \hline \multirow{3}{*}{(B) DPIEC and  hydronic radiative cooling} & \multirow{3}{*}{Kuwait} & \multirow{3}{*}{no} & \multirow{3}{*}{yes} & \(\overline{53.4\%\text{ reduction of }}\) & \multirow{3}{*}{[48]} \\  & & & & & electrical energy \\ \hline \multirow{3}{*}{(B) DPIEC and  vapor compression system} & \multirow{3}{*}{China} & \multirow{3}{*}{no} & \multirow{3}{*}{yes} & \(\overline{42.5\%\text{ to }64.0\%\text{ of }}\) & \multirow{3}{*}{[49]} \\  & & & & energy savings & \\ \hline \multirow{3}{*}{(C1) Solar desiccant cooling system} & \multirow{3}{*}{Martos, Spain} & \multirow{3}{*}{yes} & \multirow{3}{*}{no} & \multirow{3}{*}{SCOP = 2.0} & \multirow{3}{*}{[64]} \\  & & & & & SCOP = 2.1 \\ \hline \multirow{3}{*}{(C2) Solid desiccant cooling system} & \multirow{3}{*}{e.g., Tunis} & \multirow{3}{*}{no} & \multirow{3}{*}{yes} & \(\overline{\text{SCOP}}=2.1\) & \multirow{3}{*}{[53]} \\  & & & & energy savings & \\ \cline{1-1}  & & & & \(\text{41.9\%}\) & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Studies of systems using DPIEC in hot and dry. From the literature review, it can be concluded that despite intensive research and development in the field of evaporative cooling, scientists will face some challenges:  
* Arrangement of the structure and geometry of the channels in terms of optimal water distribution and even air distribution. * Improvement of water distribution systems with an emphasis on developing research into dedicated materials for evaporative indirect exchangers. * It is necessary to simplify the system construction as much as possible: sorption systems with evaporative cooling are complicated compared to compressor systems and have large dimensions, therefore they are expensive in terms of investment. * No research on indirect room evaporative exchangers--decentralized systems. * Conducting further research on increasing the thermal COP. * Determining the thermal COP from the actual cooling capacity of the supply air (in relation to the parameters of the internal air), not from the cooling capacity of a device that cools the outdoor air to the supply air parameters. * The high COP of sorption systems allows for creation of an alternative cooling system while COP is high; with a heat source such as a solar collector, it requires smaller dimensions. This results in lower investment costs and greater system application possibilities. Conceptualization, A.P. and W.W.; formal analysis, A.P. ; investigation, A.P. ; writing--original draft preparation, A.P. and W.W.; writing--review and editing, W.W.; visualization, A.P. ; funding acquisition, A.P. All authors have read and agreed to the published version of the manuscript. This research was funded by Polish National Centre for Research and Development, program Lider X, agreement number U/0180/666/2019.