# Selection of a Photovoltaic Panel Cooling Technique Using Multi-Criteria Decision Analysis
## 2 Methods and Criteria
### Ergonomics  
The interaction of the equipment with the movement of manpower is the ergonomic factor. As the PV industry is expanding with mega-size installations along with large-scale equipment for cooling and other maintenance requirements, it becomes increasingly important to the installation process. Cooling systems which are too complicated in arrangement and which require a complex piping network that can obstruct human movement are ergonomically unacceptable. Incorporating ergonomics into the design process offers benefits beyond worker safety such as marketability [43]. In this regard, each of the above cooling systems is arranged according to their complexity of arrangement from the best option to worst option in Table 4 below.  
From the above Table 4, it is evident that fin cooling has a minimum ergonomic impact as they do not involve the use of pipes or ducts and are closely fitted within the back of the panel. In the case of forced convection fan cooling, small fans are attached to the bottom of the panels in addition to the fins that drive the air away from the heat zone. Phase change material cooling involves a separate chamber at the bottom of the panel which makes them heavy and voluminous, and hence, they are ranked three. Thermosiphon cooling  
\begin{table}
\begin{tabular}{l c} \hline
**Cooling Method** & **Ergonomic Ranking** \\ \hline Aluminum fins & 1 \\ \hline Forced convection fan cooling & 2 \\ \hline Phase change material & 3 \\ \hline Thermosiphon cooling & 4 \\ \hline Heat pipe cooling & 5 \\ \hline Thermosiphon with clay pot cooling & 6 \\ \hline Water spraying & 7 \\ \hline Evaporative cooling & 8 \\ \hline \end{tabular}
\end{table}
Table 4: Ranking of cooling methods based on ergonomic acceptability.  
involves piping which may be rectangular or circular in cross-section with an arrangement for dumping the heat with fins or for other end uses as in the case of photovoltaic thermal systems. The extra projections from the panel can cause hindrance to the movement of personnel. Similarly, clay pots connected with thermosiphon systems need additional support structures and protection against breakage. Water sprays involve pumping mechanisms along with piping systems for distributing the water to spray nozzles. Water treatment mechanisms are also required in order to prevent deposits due to impure water. Evaporative cooling requires water treatment mechanisms and fans to drive air for the evaporation of moisture. Therefore, evaporative cooling methods create a maximum obstruction to the layout because of simultaneous water and air handling systems.  
Table 5 gives the consolidated attributes of the different options. Efficiency enhancement depends on the climatic region as well as on whether it is summer or winter. Two climatic regions as per the Koppen climate classification, namely, the arid desert weather condition (BWh) and continental cold and dry conditions (Dwa) are considered in this study [44]. Temperatures attained by the panel in the summer and winter are calculated using Equation (5). It is to be noted that winter conditions in the Dwa climate region do not require cooling because of very low average winter temperatures. There are eight evaluation criteria including the four types of climate-based efficiency enhancement criteria. C1, C2, C3 and C4 represent the percentage of efficiency enhancements under BWh summer, BWh winter, Dwa summer and Dwa winter conditions. C5, C6, C7 and C8 represent the reliability, cost, emission factor and ergonomics, respectively.