**8. Conclusions**

This paper presents an approach for the assessment of solar panel cooling systems using the Visual PROMETHEE multi-criteria approach. The approach that was reported in the paper is found to be useful in ranking the choices among different alternative solar panel cooling systems using multiple performance measures. A total of nine possible alternative solar panel cooling systems were analyzed based on variations in cooling effectiveness, energy efficiency, environmental impact, durability, noise pollution, and system size, weight, and cost. Using this approach, outranking flows, partial ranking, complete ranking, the network, and the GAIA plane were obtained, with the objective being to explore the strong and weak points of each of the alternative solar panel cooling systems. The obtained results enabled the identification of groups of performance measures expressing similar preferences. For example, thermosiphon cooling and nanomaterial fluid cooling systems are preferred for their economic, ergonomic, and environmental measures. Meanwhile, thermosiphons with a clay pot cooling system, water spray cooling systems, and evaporative cooling systems are preferred only to drop solar panel temperature, which is also supported by Moharram et al. [94]. These systems are preferred for solar modules installed in very hot and dry climates. On the contrary, two passive cooling approaches, i.e., finned air cooling and phase change material cooling systems, have preference over reliability, ergonomics, and electric equipment failure risk measures. In short, the contributions of this study are as follows:


As can be seen from Table 5, the outranking of nine solar panel cooling systems is A1 > A6 > A2 > A4 > A5 > A3 > A8 > A9 > A7 when equal weights are assigned to each criterion. However, it is to be noted that equal weights to all the criteria are an exaggeration, and this is just used as a reference. On the other hand, when each criterion is weighted using the entropy approach, the preference of solar panel cooling system is A1 > A6 > A2 > A4 > A9 > A8 > A5 > A7 > A3. Sometimes, certain operating requirements need a maximization of the reliability of the cooling system, and in this case, the ranking is observed to be A1 > A3 > A6 > A2 > A4 > A5 > A8 > A9 > A7. On the other hand, when the need is to focus on minimizing cost, the preference is A1 > A6 > A2 > A4 > A5 > A8 > A7 > A9 > A3. In comparison, to maximize the efficiency of the solar plant, the outrank of nine alternatives is observed to be A1 > A6 > A2 > A4 > A5 > A3 > A8 > A9 > A7, and to minimize environmental impact by minimizing CO2 emissions, the approach then suggests the preference order as A9 > A1 > A6 > A5 > A8 > A7 > A2 > A4 > A37, which shows that A9 is the best option. The overall outrank for nine alternatives is also derived as A1 > A6 > A2 > A5 > A9 > A8 > A4 > A7 > A3.

Thus, nine different solar panel cooling systems were identified, and the multi-criteria analysis tool Visual PROMETHEE was used. Six possible scenarios are examined based on the priority assigned to each performance metric. Under each situation, the best solar panel cooling strategy to the worst cooling approach has been ranked. When operational efficiency was given the most weight, finned cooling was revealed to be the best solar

panel cooling method, whereas thermosiphon cooling was the best cooling solution when the emission reduction criteria were given the most weight. The second-best method was found to be forced air cooling under equal weights, entropy weights, and 60% weightage to economic and component failure risk. The third choice is a heat pipe passive cooling system. Future research directions are set to focus on the assessment of hybrid solar panel cooling systems that are better integrated with energy management systems for improved overall performance. Comparison experiments can be executed by comparing the proposed Visual PROMETHEE approach with other MCDM methods to show its effectiveness as a future scope. One can also include performance metrics such as maintainability, technical implementation challenges, and sustainable solutions. Similarly, one can involve the development of new testing protocols and standards that can be used to assess the reliability and performance of these systems over time.

**Funding:** This research was funded by the Deputyship for Research and Innovation, Ministry of Education in Saudi Arabia, through grant number (IFKSUOR3-079-1).

**Data Availability Statement:** Data are available in the manuscript.

**Acknowledgments:** The authors extend their appreciation to the Deputyship for Research and Innovation, "Ministry of Education" in Saudi Arabia, for funding this research (IFKSUOR3-079-1).

**Conflicts of Interest:** The author declares no conflict of interest.
