# Analysis of Thermomechanical Stresses of a Photovoltaic Panel Using a Passive System of Cooling
## 1 Introduction  
One of the principal problems that the world is dealing with is the need for clean energy, thus, satisfying the energy demand around the world, and diminishing green house gases. [PERSON] et al. [1] mentioned that by the year 2030 there will be an increase in energy demand of up to 33%. Due to this, a photovoltaic system is a powerful key for resolving this problem. The performance of the Photovoltaic System (PVS) is based on solar irradiation, environment temperature, and so on. Taking into account the case of Mexico, the irradiance is considered to be from 5.6 to 6.1 kW/m\({}^{2}\) per day and stable, but the environmental temperature is variable and cannot be considered stable [2]. The temperature oscillates in a range between 10 \({}^{\circ}\)C and 26 \({}^{\circ}\)C in zones where average humidity reaches up to 95% and overall rainfall is from 100 to 4000 mm. This phenomenon causes different performance in the PVS across Mexico. Consequently, the energy conversion in the PVS in different climates and different parts of the world is about 70 to 80% of its nominal potential [3, 4]. Mexico is experimenting with a huge increase in their use of PVSs, but the few systems installed generate about 60 to 70% of their design potential [5, 6], under the international average. In a study carried out by [PERSON] and [PERSON] [7], it was mentioned that the supply of electric energy is one of the most important requirements to take into account right away. The increase in the operational temperature of a solar cell causes a significant reduction in its efficiency of 0.4-0.5% per degree Celsius [1, 8]. It is important to keep the lowest possible operating temperature in order to increase the output power and decrease the gradient temperature in its back panel [4]. The production of electricity by this type of method depends on determined physical properties such as solar radiation, heat losses, material technology and the photovoltaic panel's operational temperature [9], and only about 20% of irradiance received is converted to electricity [10]. Extensive research efforts have been carried out for this purpose. [PERSON] et al. [11] carried out an investigation with passive heat sink, which could decrease the operational temperature by up to 7 \({}^{\circ}\)C. A method proposed to do this is by putting fins on the back panel; their main function is to reduce the temperature gradient as much as possible [12; 13; 14]. It is important to keep in mind that a fracture could occur on the panel back due to a rise in thermal stresses within the module because of the temperature [15; 16]. The temperature could also induce micro cracks [17] and, thus, the integral structure has to be studied to assure its safe operation, taking into account the guidelines IEC 6215 [18; 19]. Figure 1 depicts the methodology used to decrease the operational temperature. First of all, a conventional panel was chosen in order to obtain the thermal distribution, then a comparison of the geometry of rectangular and triangular fins was evaluated, taking into account the boundary conditions. Thus, a geometry was selected to find out the best fin configuration for both cases, through thermal and structural results. The methodology described in Figure 1 was used to design the geometry, evaluate and validate the mechanical behavior and, finally, obtain the optimal design. Figure 2 depicts the mesh independence. When elements reach an average of 25,000 elements, they begin to stabilize and are optimal for both cases, in their thermal and structural analysis. Figure 1: Flow chart which depicts the methodology used for decreasing the operational temperature in a solar panel. The aim of this study was to register the stress of the electric contact subject to thermal loads and compare the traditional and the proposed heatsink, which increase the contact area of heat transfer and thus reduce the operational temperature. The use of aluminium fins can have a considerable impact on the lifetime and efficiency of the PV panel.