Experimental analysis and optimization of the air-cooled solar panel

Abstract

Keywords: Exergy; Fins; MINITAB; Optimization; RSM; Solar Panel

Introduction

Environmental problems and economic crises of fossil fuels search the alternative methods for energy production. Solar energy is one of the best ways to convert it into electrical energy. The solar panels show its importance by directly converting solar energy into useful electrical energy. The solar panel is formed by the parallel and series combination of the solar cells. The solar cell is formed by the P-N junction in which holes and electrons cross the depletion layer by absorbing the solar energy. However, the number of factors affect the performance of the solar panel of which some factors are external and internal. The external factors are uncontrollable by the human being but the internal factors can be controlled and modified to hike the solar panel’s performance [1]. The higher surface temperature of the solar cell enhanced the thermal resistance of the depletion layer and slowed down the speed of the electrons, so the performance of the PV module was lacking. However, a number of design have been investigated to cool the solar panel, the purpose is to avoid over heating and sustain the performance. A number of cooling methods like active [2, 3, 4], passive [5, 6, 7], nanoparticles [8, 9, 10] and PCM combined with other cooling [11, 12, 13] fluids have been used. Active cooling requires an external energy source to pump the water and air. The active cooling enhances the heat transfer coefficient and turbulence due to that it has large ability to cool the solar cell. It included the forced air, forced water, and PV/T system. In the active cooling method, the net power produced by the photovoltaic module is obtained by deducting the pump or blower power from the solar panel output power. The passive cooling method requires no additional prime mover; it’s based on fully natural circulation. The heat pipe, natural air, and water circulations are considered to be passive cooling approaches in which heat transfer is lower leading to poor performance at higher temperatures. The main advantage of passive cooling is its lower cost due to negligible variable cost. It improved the productivity of solar panel very little due to natural circulation. The Phase Change Material (PCM) works well for performance enhancement of the solar panel by absorbing maximum heat trapped inside it. In the primary heating process, PCM material starts to heat with melting and absorbs a part of sensible heat. In secondary heating, the phase change of PCM material starts which absorbs the latent heat. Due to the heat absorption from the PV cell during day time, the PV cells cooled and produced more power. The cycle is reversed at night time, at the time of the absence of the Sun, which cools down the solar panel, and PCM material reaches in initial state. PCM cooling gets popularity due to its large absorption capacity, low cost, and chemical stability. The selection of the PCM material depends on the maximum, and minimum temperature of the solar panel and atmospheric temperature. Based on these temperature ranges, the PCM material properties selected, the main PCM material properties are namely thermal, physical, kinetic, chemical, economic,

and environmental listed in [14]. Rok et al. [15] performed an experimental and numerical simulation on the performance improvement of the 250 W solar panel using PCM cooling. The RT28HC is used as a PCM material for the cooling of solar panel. The experimental results depicted that PCM material reduced the surface temperature of solar panel by 35.6°C as compared to without cooled solar panel. Rajvikram et al. [16] enhanced the thermal conductance of PCM by using the aluminum sheet as a thermal conductivity enhancer. The test has been conducted for three months. The outcomes of the study indicated that if PCM material with an aluminium sheet attached at the back of the solar panel, the average efficiency enhanced to be 24.4% with an ordinary decline in the temperature of the 10.35°C. Yahya et al. [11] investigated the multi-layered PCM material in solar panel temperature reduction. The approach involves integrating PCM with metallic PCM attached at the back end of the solar panel. The ANSYS FLUENT software has been used for determining the solidification and melting phase. This cooling system enhanced the PV module performance by 35.8% compared to the panel without cooling at the ambient temperature of 40°C and solar flux of 1000 W/m2. Fatih et al. (2020) studied the performance of the phase change material, thermoelectric, and aluminium fins on the solar panel cooling. The outcomes of the study saw that the aluminium fins produced the maximum power and the PCM and TEM generated the lowest power. The PCM material worked as the insulator due to the lesser thermal conductivity of the PCM material. Mais et al. [17] experimented to determine the cooling effect of the RT 35 (PCM) on solar panel. The outcomes of the study show that the 16°C temperature has been reduced by using PCM but If the rectangular fins have been used as the thermal conductivity enhancer then further 2°C temperature drop was again achieved. Rajvikram et al. [18] investigated the PCM, fins, and water for the cooling of the solar panel. The outcomes of the study depicted that in two consecutive days reading, the power output enhanced to 8.12% and 9.39% higher than without cooled solar panel. The temperature measurement of the cooled and without cooled solar panel were lower than the 50°C and 70°C. The thermoelectric cooling, worked on the principle of the Peltier Effect requires no cooling fluids, only electric energy is required to cool the solar panel. In this cooling, a cold and hot heat source has been generated in which heat flow occurs from lower to higher temperatures. The amount of cooling provided by this technique is lower than the active cooling but more than the passive cooling. The active cooling technique with forced air cooling, required little design change and feasible to fit fan and blower with the solar panel. A number of researchers published the work on active air cooling. In the below section active air cooling on solar panels is given concisely. Teo et al. [2] explored the effect of air cooling on the power output of the solar panel, and results were compared with those without a cooled solar panel. The results indicated that

the overall temperature reduced by this approach was 30°C, and efficiency improvement recorded to be 4%. Golzari et al. [19] experimentally investigated, the effect of air cooling channel on the performance of the solar panel. The results showed, that solar panel temperature was reduced by 5°C and efficiency improvement of the solar panel was recorded to be 2.6%. Elminshawy et al. [20] performed the experimentation on solar panel cooling by geothermal air cooling. It reduced the solar panel temperature by 9.75°C and improved the solar panel efficiency by 22.98%. Arifin et al. [21] investigated the effect of the aluminum rectangular fin on the heat transfer rate and performance improvement of the solar panel, due to this cooling, the maximum temperature of the solar panel decreased from 85.3°C to 72.8°C. Lebbi et al. [22] investigated the effect of water and air cooling on the back and the front side of the solar panel, for water cooling drip irrigation system was used, and the fan was used for air flow. This cooling effect condensed, the module temperature by 15°C and raised the panel efficiency by 5.7%. Saleri et al. [23] used thermoelectric cooling on the rear side of the solar panel to lower the solar panel temperature and enhance efficiency. This design has been proven to reduce the solar panel temperature by 15°C and heighten the efficiency by 5.7%. Li et al. [24] investigated the influence of compressed air on the cleaning and cooling of the solar panel. The results reveal that, the efficiency improvement of the solar panel was recorded to be 33.42% by using this technique. Almuwailhi and Zeitoun [25] conducted experiments on solar panel cooling in natural convection, forced convection, and evaporative cooling, and compared the results

with those without cooled solar panel. They identified, the temperature of the solar panel lessened by 6°C in forced air cooling with efficiency improvement recorded to be 4% by use of this cooling technique. Abdullah et al. [26] conducted, a study on the air cooling on the efficiency of the solar panel. They identified, the efficiency improvement of the solar panel recorded to be 0.8% as compared to without air-cooled solar panel. Abdullah et al. (2024) [27] investigated experimentally a photovoltaic solar panel on Trombe wall for heating the room in the winter season. This system operates with the help of solar energy without supplying electricity. The experimental models have been prepared, one with DC fan and other without DC fan. The outcomes of the study revealed that the system having the DC fan has higher electrical and thermic efficiency as compared to another system. Abhijeet et al. (2024) [28] performed the energy and exergy analyses of the 380 kW power roof top photovoltaic grid-connected system. They concluded that the system generated the 732.4 kWh/year through this plant. Furthermore, results have been validated with the responses’ neural network linear, non-linear, and exponential behaviour. Amjad et al. (2025) [29] used a porous medium to cool the solar panel. They concluded that the solar panel efficiency enhanced to the level of 19% and 5.1% efficiency increased as compared to without cooled solar panel. The cooling fluids properties are responsible for desirable heat transfer and solar panel performance. On the other hand, the various researchers used the number of designs at the rear side of the solar panel. Table 1 presents the various designs of solar panel cooling, used previously so far.

Table 1. Various design of the heat sink with air cooling in solar panel S. No. Author,s Description

A cooling air duct was provided at the rear side of the solar panel.

Enhanced the efficiency 2.1% and save, the energy around 7.9%

Outcomes of the study Heat to mass transfer enhanced by 68%.

The increasing the number of fans enhanced the power output. If the one fan used then power output increased 12.93%, if the dc fan increased 2, 3 and 4, the power output increased 37.17%, 41.28% and 44.34% respectively.

Create the air channel path at the back of solar panel and used the forced air to cooled.

7.5% power output can be enhanced by use of this technology.

Reduced, the solar panel temperature around 10°C at peak sunny hours.

Cross fins heat sink fixed at the back side of the solar panel.

A heat sink of long rectangular fin fixed at the bottom side of the solar panel.

Enhanced performance at due to increased mass flow rate of air.

Long rectangular fins have been attached at the back end of the solar panel.

A heat sink of triangular fins having alternative layout fitted at the back side of the solar panel

Research Gap, Novelty and Application of the Work Table 1 displays, the several designs of heat sink produced at the rear side of the solar panel in air cooling. The air cooling is feasible requires little change in design at the rear side of the solar panel. Fins are produced on the cooling surface to enhance; the heat transfer by increasing the surface area of the cooling surface. In previous research, rectangular fins were mostly used in the study and very few researchers focused on the high-density pin fins [37]. Although, cylindrical high density pin fins can be produced in large numbers as compared to rectangular fins for making the heat sink compact. Therefore, in this study, high-density pin fins were integrated into the rear surface of a solar panel, and an optimization technique was employed to determine the optimal heat flux and air flow rate for maximizing the panel’s performance. The use of high-density pin fins significantly improves the efficiency and operational lifespan of the solar panel. Enhanced efficiency leads to increased power production and a reduction in the panel’s size, allowing for the same power output to be achieved at a lower investment cost. This work is novel and new in its simple and light weight arrangement as compared to heavy vibrating pumps required in liquid and nano-fluid cooling. Additionally, the approach of optimization and economic analysis of the solar panel cooling system is also new very little focused in the previous literature with high density pin fins. The reduced investment cost makes solar panels more accessible and appealing, particularly to farmers and economically disadvantaged communities, encouraging wider adoption to meet energy demands. Furthermore, the lower cost of solar-powered irrigation reduces farming expenses, thereby increasing farmers’ profitability. This approach addresses a critical societal challenge by promoting sustainable and cost-effective energy solutions for agriculture and beyond.

Experimental Setup

Figure 1(a) illustrates the experimental arrangement of the solar panel air-cooling system. The setup consists of two

10. Wp solar panels as presented in Table 2 in which first solar

panel is without fins and the second is with fins. The second number of solar panel consists of 196 cylindrical fins, each with an external diameter of 3 mm and fin length of 16 mm. The fins are arranged in horizontal and vertical rows with a spacing of 10 mm and 23 mm, as depicted in Figures 1(b) and 1(c). The solar panel size measures to be 323 mm in length and 217 mm in width. The experimental investigation was conducted to measure various parameters, including solar flux intensity, ambient temperature, photovoltaic (PV) module temperature, air velocity, current, and voltage generated by solar panels. The total experimental observations collected was 13 as per the requirement of Design Expert software for optimization purposes, with the corresponding data summarized in Table 3. These runs provided

a comprehensive dataset for analyzing and optimizing the performance of the solar panel cooling system. Instruments played a critical role in capturing measured data during the experiments. A pyranometer was used to measure solar flux intensity, thermocouples were employed to record surface and air temperatures, an anemometer determined air velocity, and a multimeter was utilized to measure current and voltage outputs from the solar panel. The experiments were conducted at varying discharges of the air (0.01 m3/s to 0.02 m3/s) on three consecutive dates in the months 14, 15, and 16 which gives the average reading of the months. The experimental data have been collected from the (01/01/2023 to 21/12/2023). The schematic representation of the experimental setup with instruments is given in Figure 2. Details regarding the accuracy and measurement ranges of the instruments are provided in Table 4.

Modelling Of The Solar Panel With FINS

Figure 3(a) illustrates the different layers of the solar panel along with the pin fins attached to its rear side. The material properties of each layer are detailed in Figure 3(a) and summarized in Table 5. The solar cell layer exhibits an absorptivity of 1, ensuring no heat flux passes through it; instead, heat transfer occurs from the solar cell to the lower layers of the panel due to the temperature gradient. When solar flux is incident on the panel, the solar cell reaches the highest temperature among all layers, causing heat transfer both to the upper and lower surfaces of the panel. Figure 3(b) presents the thermal resistance circuit diagram for the solar panel cooling system. Heat transfer from the solar cell occurs primarily through conduction in the top and bottom layers, with the conduction resistances of each layer represented in the diagram. At the top, heat dissipates through a combination of convection and radiation. On the bottom side, heat transfer is improved by the addition of circular pin fins and fan-forced convection. Consequently,

Figure 1. Solar panel air cooling system (a) Experimental setup (b) Rear side of experimental setup (c) Rear side of the solar panel with circular fins.

Figure 2. Schematic representation of the Experimental setup.

Table 3. Experimental data of 13 runs of the experimental observations Run

Table 4. Performance parameters of the measuring instruments Instrument

K:0-1200°C Digital Anemometer Solar Power Meter Surface contact temperature measurement

the bottom layer dissipates heat to the atmosphere through the fins and the un-finned areas of the panel›s rear surface. The total amount of heat transfers from solar cells to the atmosphere.

Where σ is the Stefan Boltzmann Constant and ε is the emissivity of the upper layer of the solar panel. The unfin surface convection and radiation thermal resistance also represented by following equations [39].

(1) QCell is the heat flow through the solar cell, Q1 is the heat flow through the top surface of the solar panel, Q2 is the heat flow through the bottom surface of the solar panel. (2) Where TC is the cell temperature, Tatm is the atmospheric temperature, R1, R2, R3, R4, R5 and R6 are the thermal resistance of the conduction of various layers of the solar panel, RConvection is the convection resistance from top surface, RRadiation is the radiation resistance from the top surface, RFin is the thermal resistance due to fins, RUnfin is the thermal resistance due to unfin surface area. The unfin rear side surface of the solar panel contributes the heat transfer by convection and radiation. So the thermal resistance of the unfin surface of the PV modules is assumed by the following relation. (3) Where RConvection unfin is the unfin surface convection resistance and RRadiation Unfin is the unfin surface radiation thermal resistance. The R1, R2, R3, R4, R5 and R6 are thermal resistance of the conduction of various layers of the solar panel. The values of these thermal are given below.

(6) Where hCb is the convection heat transfer coefficient from unfin surface and AUnfin is the unfin surface area of the solar panel. (7) Where TCb is the temperature of the base of the solar panel. The fin thermal resistance for the convection boundary is represented by the following equation. (8) Where qFin is the heat flow through the fins. (9) Where m is the constant depending on the fin length and diameter and L is the length of the fins. Where φ is the function represented by the following equation [40]. (10) Where Bie is the fin tip Biot Number, Bic is the fin base Biot Number and Bi is the fin Biot Number. (11)

Where L1, L2, L3, L4, L5, and L6 are the thickness of the several covers of the solar panel presented in Figure 3 (a). K1, K2, K3, K4, K5 and K6 are the thermal conductivity of the EVA, ATFE, EVA, PET, TAPE, and CFRP layers of the solar panel, A is the surface area of the solar panel. The convection and radiation thermal resistance of the top surface of the solar panel of material ETFE is given by the following equations. (4) Where hC is the solar panel top surface convection heat transfer coefficient. (5)

Where L is the length of the fin, k is the thermal conductivity of the fin material represented in Table 4, te is the fin tip thickness, A is the crossectional area of the fin base and p is the perimeter of the fin tip. The hc is the fin base contact conductance for aluminium it is taken as 1000 W/m2. k, h is the fin convection coefficient and he is the fin tip convection coefficient. The h and he is found by the following formula of the Nusselt Number [41]. (12) Where Re and Pr is the Reynold Number and Prandlt Number of the air. The Pr is the Prandlt Number calculated by following the formula [42].

Now heat transfer coefficient has been determined by the subsequent equation [43].

(14) where ρ, μ, and k are the density, dynamic viscosity, and thermal conductivity of the air. The Dh represents the hydraulic diameter of the pin fin. Efficiency and Exergy of the Solar Panel Figure 4 represents the various energy interactions in the control volume of the solar panel. The Wp represents the pump work, We is the solar panel electrical work, Qin is the solar energy reached on the solar panel, Qout is the energy lost in the atmosphere, and CV is the control volume. The system is considered to be a steady state with kinetic and potential energy terms of the air at the inlet and outlet are neglected. To apply the first law of thermodynamics for the Figure 4 control volume [44]. (15) Where h1 and h2 are the enthalpy of the air at the inlet and outlet section of the solar panel. mair is the mass flow rate of the air.

In equation (18), the left-hand part represents the input energy, and right-hand side first part represents the electric work output, the second part represents the heat carried by air and the third part represents the energy loss in the atmosphere. The electrical efficiency of the solar plate is given by the following relation (19) ηe is the effective efficiency of the solar panel. Now apply the exergy balance for the solar panel control volume [45] (20) Where EXin is the exergy entering the PV module, EXout called the exergy leaving the system, Ed is the exergy destruction inside the system.

Figure 4. Heat and Work Interactions within the Solar Panel’s Control Volume.

(22) (23) Where ESUN is the exergy received from the Sun and φ1 and φ2 are the inlet and outlet flow exergy. (24) Equation (22) left hand term represents the exergy supplied to the solar panel, right hand side first term represents the exergy recovered, second term shows the exergy recovered by air and third term represents the exergy loss in the atmosphere. Now exergetic efficiency of the air (25) The exergy reached on the solar panel [46]. (26) Cost Estimation of the Solar Panel The cost estimation of the modified solar panel justifies the suggested cooling techniques. The best way to compare the Levelized Cost of Energy (LCOE) of the simple solar panel and the modified solar panel. The LCOE is the ratio of the total investment in the life cycle of the solar panel to the total power production by the solar panel in its life cycle. The total investment of the project is the sum of the cost of the solar panel, material cost, manufacturing cost, maintenance, operational cost, and fixed cost. The total power production is counted in kWh with every year depreciation will be counted. So following equation has been used for the calculation of the LCOE of the system. (27)

Where I is the investment, M is the maintenance cost, F is fixed cost and E is energy produced throughout the life cycle, r is the discount rate and n is the number of years. The initial investment is the sum of the cost of the solar panel, material, and manufacturing. It is assumed by the following relation. (28) Where x is the cost of the solar panel ($/Wp), p is the power of the solar panel, ρ is the density of fin materials, v is the volume of the fins material, y is the cost of the material ($/kg), m is the manufacturing cost. The volume of the fins is given by the following equation. (29) Where d is the diameter and L is the length of the fins. Optimization Technique The optimization has been performed to know the optimum values of the input variables on which, the system of the solar panel cooling gives the maximum power output and efficiency. For which Response Surface Methodology (RSM) has been used. In year 1951 [47], RSM was used in chemical industries for improving production but recent times due to development of the various Design of Experiment (DoE) models, the RSM is used each and every field to maximize the output. The best thing with the RSM is that it easily converts the responses in terms of the explanatory variables by 2nd order model. The model accuracy has been determined based on the various error factors and validated with the actual experimental setup. In this analysis, a Central Composite Design (CCD) has been used for defining the input variables and total number of the run. The CCD based on two input variables (Solar Flux, Discharge) [48], code and coded values of the input variables are given in Table 6, the total number of the runs is 13 in which, cube points are 4, center points in the cube are 5 and axial points in the cube are 4 as shown in Figure

5. Table 3 represents the total number of experimental runs

and corresponding responses. The variable α represents the rotatibility of the matrix and it is determined by the following equation.

Table 5. Properties of the several layers of the solar panel Materials

Where k represents the number of factors. In the two factors design k = 2, then α = 1.414. In CCD design, based on the total number of the runs, the responses have been calculated and with the help of the ANOVA analysis 2nd order polynomial has been generated. The 2nd order polynomial of response variables have been represented by following equation [49]. (31) The xi and xj are the input variables and Y is the dependent variable. A0, Ai, Aii and Aij are the constant of the linear and square terms. The B represents the error or the noise in the model equation. Based on the data of the Table 3, the following model equations have been developed for the responses namely module temperature (Tm), power output (W), solar panel efficiency (ηP) and exergy efficiency (ηeX). (32) (33) (34) (35) Based on these model equations error of all the responses has been calculated and the model has been validated with experimental data. Table 7, Table 8, and Table 9 represents the error analysis of the responses. In Table 7 and Table 8, the P values of all responses are less than 0.01 showing the model is significant. Table 9 shows the values of the R2, adjusted R2, and predicted R2 values which are larger than

Results And Discussion

Module Temperature Variation with Input Variables Figure 8 shows the 3D plots of the module temperature with solar flux and air flow rate in which if the solar

Figure 7. Perturbation plot of the responses with respect to input variables.

flux increases then the module temperature increases sharply due to the supply of higher solar energy on the surface of the solar panel. The higher energy content enhanced the trapped heat inside the solar panel which will increase the solar panel temperature. On the another hand with air flow rate, the module temperature is reduced due to an increase of mass flow rate since at higher mass flow rate more heat is carried by the air which lowers the module temperature [55]. Figure 8 indicates that the module temperature is 27.6°C at the solar flux of 400 W/m2 and it increased to 67.1°C at the solar flux of 800 W/m2. The 58.9% hike in module temperature occur due to two times increasing the solar flux.

Figure 8 also shows that if the solar flux is more than 720 W/m2, the module temperature is higher than 60°C. So, at higher solar flux air flow rate should be more than

9. AM to 10 AM, the PCM material with IFW gives the

maximum efficiency, but after 10 AM to 3 PM, the water cooling at a mass flow rate of 1.5 LPM gives the maximum efficiency. In the morning between 9 AM to 10 AM, the PCM material started to melt and changes the phase, this process absorbs the latent heat and cools down the module at a desirable limit but when all PCM material melted, then it absorbs the sensible heat and lower down the cooling rate and reduce the efficiency. Although, in water cooling, always fresh water at optimum mass flow rate is supplied to the solar panel surface, which maintains the solar panel efficient at a constant level throughout the day. On the other hand, the air has low heat absorbing capacity since air cooling has lower cooling efficiency as compared to the PCM and water cooling.

Conclusion

Fossil fuels are exhaustible in nature and not economical due to hikes in price, creating the requirement of alternative fuels that are renewable and eco-friendly to the environment. Solar panel are best fitted to fill this gap since they

convert solar energy into electrical energy without creating any harmful effect in the atmosphere. The main drawback of the solar panel is the low performance at high temperatures. So, at the time of the solar panel’s working, solar cooling must be required for the sustainability of the efficiency. High solar panel efficiency reduces the initial investment so that it can be afforded by the farmers and the poor people located in rural and remote areas. This research focused on the performance improvement of the solar panel by the use of air cooling. The air cooling is chosen for the study due to its simple arrangement and noncorrosive nature. The main limitation of the study is the lower cooling effect due to the lower thermal diffusivity of the air. However, it is the most used method as a cooling medium in all fields of engineering like automobiles, electronic equipment, and the aerospace industry due to cost-effective and easy of implement. For the thermal analysis of the cooling arrangement, the system has been designed and optimized by the Response Surface Methodology, and the optimum setting of the input and output variables has been determined based on the constraints of the optimization. The percentage enhancement in the responses due to air cooling compared with the without cooled solar panel. The following are the main concluding points of this study. 1. The solar flux and the air mass flow rate are two important input variables that affect the performance of the solar panel. As the solar flux enhanced from 400 W/ m2 to 800 W/m2, the module temperature augmented from 22.9°C to 63.5°C which hamper the thermal performance from 14.4% to 10.8%. 2. Enhancing the solar flux increases the module temperature of the solar panel due to that the performance

of the solar panel decays throughout the day. The exergy analysis shows that from 400 W/m2 to 800 W/m2 increase in solar flux reduces the exergy efficiency from 15.9% to 12.0%. In the optimization process, the optimal solar flux and air discharge were found to be 403.3586 W/m2 and 0.0221 m3/s on which responses are module temperature 22.4279°C, power output 4.1196 Wp, PV module efficiency 14.41% and exergy efficiency 15.78%. At higher solar flux and high air discharge is feasible to drop down the temperature of the solar panel since increasing discharge continuously reduces the air temperature. However, at very high temperature of the solar panel, the air cooling will be ineffective in dropping the temperature of the solar panel at the optimum limit, this situation can be handled by using liquid cooling and phase change material. At 800 W/m2 solar flux if the air discharge increases from 0.01 m3/s to 0.02 m3/s, the solar panel efficiency increases from 14.7% to 15.9%. At the discharge of 0.01 m3/s, the 9.16% reduction in temperature and 3% enhancement in the power output has been recorded and if the discharge is increased to

Acknowledgment

The authors thank IFTM University›s management and vice chancellor for permitting them to conduct the study and providing the facilities they needed.

Conflict Of Interest

The Author’s declare that they have not any conflict of interest.

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