Experimental Study on Performance Enhancement of a Photovoltaic Module Incorporated with CPU Heat Pipe—A 5E Analysis

As is already known, solar photovoltaic (PV) technology is a widely accepted technology for power generation worldwide. However, it is scientifically proven that its power output decreases with an increase in the temperature of the PV module. Such an important issue is controlled by adopting a number of cooling mechanisms for the PV module. The present experimental study assesses the effect of a fanless CPU heat pipe on the performance of a PV module. The experiment was conducted in June in real weather conditions in Yekaterinburg, Russian Federation. The comparative analysis of two PV panels (i.e., cooled, and uncooled) based on the electrical energy, exergy performance, economic, embodied energy and energy payback (5E) for the two systems is presented and discussed. The key results from the study are that the average temperature reduction from the cooling process is 6.72 °C. The average power for the cooled panel is 11.39 W against 9.73 W for the uncooled PV panel; this represents an increase of 1.66 W for the cooled module. Moreover, the average improvements in the electrical efficiency, and embodied energy recorded for a cooled PV panel 2.98%, and 438.52 kWh, respectively. Furthermore, the calculations of the levelized cost of energy (LCE) for the cooled PV panel indicate that it can range from 0.277–0.964 USD/kWh, while that for the uncooled PV panel also ranges from 0.205–0.698 USD/kWh based on the number of days of operation of the plant.


Introduction
Fossil fuels have been the major source of energy generation for a very long time now globally [1][2][3][4]. These fossil fuels have become an environmental concern, due to the negative effect they have on the environment [5][6][7][8]. Therefore, the demand for clean and renewable energy (RE) sources has in recent years increased around the world to help reduce the usage of fossil fuels [9][10][11]. Solar photovoltaic technology is one of the reachable, clean, and viable RE options that is broadly acceptable around the globe [12][13][14]. Solar PV generates electricity by converting solar energy directly into electrical energy, where solar radiation is available. Solar PV technology is noiseless during its operation and needs little maintenance [15,16]. Although solar PV technology is the most viable technology globally, the major disadvantage of PV is that as the cell temperature increases, its electrical efficiency also decreases [17][18][19][20]. Therefore, to maintain an appropriate electrical efficiency of the PV to cool the temperature of the PV module. Moreover, this study was performed in real weather conditions in Yekaterinburg, Russian Federation located at latitude: 56.841 • N, longitude: 60.64 • E. The outdoor experiment comprised a modified PV panel with CPU heat pipes at its rear side (i.e., a cooled panel), and a PV panel without any modifications (i.e., an uncooled panel). Parameters such as temperature distribution, and energy, exergy, embodied energy, economic and energy payback (5E) analysis for the two modules are presented and discussed in the paper.

Materials and Methods
This section presents the working principle of a fanless heat pipe CPU sink, and the construction of an experimental test rig. It also contains the mathematical relations used for the calculation of the various parameters. The two modules used for the experiment (i.e., cooled and uncooled) have a capacity of 30 W each with a length of 950 mm and a width of 450 mm.

Heat Pipe Theory and Operation
The most essential technology that helps in the cooling of electrical equipment is air conditioning [51]. There were three main ways to cool electronic equipment in the past: (1) passive air cooling, which dissipates heat by forcing air to flow using fans; (2) forced air cooling, which dissipates heat by forcing coolants such as water to pass [52]; and (3) forced liquid cooling, which dissipates heat by forcing coolants such as water to pass [52]. Forced convection, which involved directly connecting a fan to a heat sink, was the traditional method for dissipating heat from desktop computers. Heat sinks with plate fins are particularly useful in cooling electronic equipment because of their advantages, such as simple machining, simple structure, and cheaper cost [53]. Heat flux for the CPU has increased dramatically as a result of the reduced CPU size and increased power found in modern computers [54]. Limits on the size of heat sinks and fans, as well as the noise level associated with increasing fan speed, have been enforced. As a result, there has been an increasing demand for better cooling solutions that are compatible with today's CPU requirements. Two-phase cooling systems, such as the heat pipe and the thermosyphon, have emerged as viable heat transfer devices as alternatives to traditional heat sinks, with effective thermal conductivity over 200 times that of copper [55].
To overcome pressure drops within the heat pipe, the highest capillary pressure must be higher than the sum of all the pressure drops inside the heat pipe; hence, the primary condition for heat pipe operation is as follows: where ∆P c denotes the maximal capillary force within the wick structure, and ∆P 1 denotes the pressure drop required to return the liquid from the condenser to the evaporation section. ∆P v is the pressure drop required to transfer vapour from the evaporation to the condenser section, and ∆P g is the pressure drop induced by a difference in gravitational potential energy (which can be positive, negative, or zero depending on the heat pipe orientation and direction) R With reference to Figure 1 [56], the basic processes of heat pipe operation are as follows: 1.
The evaporation of the working fluid is enabled by the heat added at the evaporator portion by conduction through the wall of the heat pipe.

2.
Movement of vapor from the evaporator section to the condenser section occurs; this is influenced by the vapour pressure drop occasioned by the working fluid evaporation.

3.
In the condenser part, the vapour condenses, releasing its latent heat of evaporation.

4.
The liquid moves back to the evaporator section from the condenser section through the wick using capillary force and liquid pressure drop. 1. The evaporation of the working fluid is enabled by the heat added at the evaporator portion by conduction through the wall of the heat pipe. 2. Movement of vapor from the evaporator section to the condenser section occurs; this is influenced by the vapour pressure drop occasioned by the working fluid evaporation. 3. In the condenser part, the vapour condenses, releasing its latent heat of evaporation. 4. The liquid moves back to the evaporator section from the condenser section through the wick using capillary force and liquid pressure drop.
In the horizontal direction if φ = 0 then the Equation (5) will be modified to Equation (6) as shown below Here, μl, μv, signify liquid and vapor viscosity, & are liquid and vapor density, & are wick and vapor cross-sectional areas, respectively. Furthermore, , , K, , ℎ , , ∅, signify gravity, vapor distance, wick permeability, effective length, heat of vaporization of liquid, surface tension, angle to the pipe in the horizontal direction, and effective radius of the pores of the wick, respectively [57]. The liquid pressure, vapour pressure, and capillary pressure drops can be calculated from Equations (2)-(5) [57].
In the horizontal direction if ϕ = 0 then the Equation (5) will be modified to Equation (6) as shown below Here, µ l , µ v, signify liquid and vapor viscosity, ρ 1 & ρ v are liquid and vapor density, A w & A v are wick and vapor cross-sectional areas, respectively. Furthermore, g, D v , K, L e f f , h f g , σ 1 , ∅, r e f f signify gravity, vapor distance, wick permeability, effective length, heat of vaporization of liquid, surface tension, angle to the pipe in the horizontal direction, and effective radius of the pores of the wick, respectively [57].

Construction of Experimental Test-Rig
The construction of the experimental test-rig is shown in Figure 2. It includes a 60 mm × 40 mm × 10 mm Al sheet on which the fanless heat pipe sinks supplied by the Semoic company, China [58] were mounted for the cooled PV panel. The HY-170 thermal paste (grease) is applied between the back of the module and the aluminum sheet to increase the thermal conductivity between them [59]. A universal silicone gel was also used between the PV panels and Al sheet to hold them firmly [59]. A total of four fanless heat pipe sinks were mounted on the top of the Al sheet with the help of a 450 mm × 30 mm connecting rod at the back of a PV as shown in Figure 2. In addition, three sets of K-type thermocouples with a temperature range between −270 • C and 1260 • C with a resolution of 0.75% were also used to measure the temperature of the panels with the help of a 4-Channel SD Logger 88598 (World wise testing service Co. Ltd., Taipei, Taiwan) [60]. The thermocouples were manufactured by the REOTEMP instrument cooperation [61]. In order to perform further experimental works, a rectangular basin with a length and width of 950 mm × 450 mm × 350 mm was used to host the water and the integrated fanless heat pipe. In addition, a TM-207 solar pyranometer (Tenmars Electonics co. Ltd., Taipei, Taiwan) [62] was used to measure the solar radiation on the day of the experiment. A clamp meter (RS components, UK) [63] was employed to record the voltage and current of the two PV panels and a digital anemometer was employed to measure the wind speed during the experiment. The specifications of the four fanless heat pipes are presented in Table 1. The image of one of the fanless heat pipe sinks that was used for the present study is shown in Figure 3. mm × 40 mm × 10 mm Al sheet on which the fanless heat pipe sinks supplied by the Semoic company, China [58] were mounted for the cooled PV panel. The HY-170 thermal paste (grease) is applied between the back of the module and the aluminum sheet to increase the thermal conductivity between them [59]. A universal silicone gel was also used between the PV panels and Al sheet to hold them firmly [59]. A total of four fanless heat pipe sinks were mounted on the top of the Al sheet with the help of a 450 mm ×30 mm connecting rod at the back of a PV as shown in Figure 2Error! Reference source not found.. In addition, three sets of K-type thermocouples with a temperature range between −270 °C and 1260 °C with a resolution of 0.75% were also used to measure the temperature of the panels with the help of a 4-Channel SD Logger 88598 (World wise testing service Co. Ltd., Taipei, Taiwan) [60]. The thermocouples were manufactured by the REOTEMP instrument cooperation [61]. In order to perform further experimental works, a rectangular basin with a length and width of 950 mm × 450 mm × 350 mm was used to host the water and the integrated fanless heat pipe. In addition, a TM-207 solar pyranometer (Tenmars Electonics co. Ltd., Taipei, Taiwan) [62] was used to measure the solar radiation on the day of the experiment. A clamp meter (RS components, UK) [63] was employed to record the voltage and current of the two PV panels and a digital anemometer was employed to measure the wind speed during the experiment. The specifications of the four fanless heat pipes are presented in Table 1. The image of one of the fanless heat pipe sinks that was used for the present study is shown in Figure 3.   A picture of the set-up for the experiment and the schematic representation of the experiment are presented in Figure 4.

Energy Analysis
According to the first law of thermodynamics, the efficiency of solar PV panels is affected by the ambient temperature as well as the module temperature. Therefore, the energy efficiency of a PV panel is defined as the ratio of power output to the power input of a PV panel as shown below [30,59,65,66].
where and represent the current ampere and voltage, respectively.
where G is the global solar irradiation (W/m 2 ), and A is the module area (m 2 ); the area of the module is 0.4275 m 2 used in the study [65]. Therefore, the energy efficiency ( ) of the PV module is calculated as follows

Energy Analysis
According to the first law of thermodynamics, the efficiency of solar PV panels is affected by the ambient temperature as well as the module temperature. Therefore, the energy efficiency of a PV panel is defined as the ratio of power output to the power input of a PV panel as shown below [30,59,65,66]. where I mp and V mp represent the current ampere and voltage, respectively.
where G is the global solar irradiation (W/m 2 ), and A is the module area (m 2 ); the area of the module is 0.4275 m 2 used in the study [65]. Therefore, the energy efficiency (η energy ) of the PV module is calculated as follows [30,59,66]; The V oc is known as opencircuit voltage, I sc and FF are the short-circuit voltage and fill factor, respectively.
An increase in the PV cell temperature decreases both the open-circuit voltage and the FF while the short-circuit current increases but only slightly. Therefore, the net effect will result in a linear relation, as shown in Equation (10) [66].
The solar coefficient is usually taken as zero or neglected and as a result Equation (10) reduces to Equation (11).
Finally, the improvement in cooled PV can be computed by using Equation (12) [67].
where, η T re f is the efficiency at STC taken as 15% in the current study β re f presents the temperature coefficient, and the value is 0.004/K, γ is the solar radiation coefficient, and the value is 0.12 [66,68]. Using PV syst software (developed by PV SOL, Satigny, Switzerland), the effects of cell temperature on the characteristics of a 30 W generic poly PV module are shown in Figures 5 and 6.
where, is the efficiency at STC taken as 15% in the current study presents the temperature coefficient, and the value is 0.004/K, is the solar radiation coefficient, and the value is 0.12 [66,68]

Exergy Analysis
According to the second law of thermodynamics, the exergy balance for a PV syst can be represented mathematically as presented in Equation (13) [32,69,70].
where . Σ x out is the exergy outlet rate, and . Σ x in is the exergy inlet rate. The exergy inlet from the sun can be computed using Equation (14) [71] .
where T amb is the ambient temperature on the day of the experiment, which was measured using the GM 1362-EN-01 thermometer; T Sun is assumed to be 5770 K for the study, G is the solar insulation (W/m 2 ), A is the area of the module [72]. The output exergy is defined as [73]: .
Finally, the exergy efficiency for the PV system is defined as follows [74]: where T cell (K) is the surface temperature of the PV module, h c is the convective heat transfer coefficient (W/m 2 -K) and it is calculated by using the wind speed given in Equation (17) [75].

Economic Analysis
The economics of the cooled and uncooled modules were done using the levelized cost of energy (LCE) metric. According to other studies, LCE is a fundamental metric that is used in the calculation of the cost of renewable and non-renewable energy projects. The main objective of LCE in the current work is that it will determine whether to move further with the project or as a means to compare different energy-producing projects. Mathematically, LCE is expressed in Equations (18)-(23) [76][77][78].

Energy Payback Time (EPBT)
The EPBT can be explained as the required time within which the energy savings recompense the invested energy. The invested energy in this case refers to the embodied energy E in which can be defined as the entire spent energy in the course of the manufacturing of a system over the whole lifecycle. One of the main indicators in identifying the sustainability of a certain RE power plant over other technologies is the EPBT. It can be estimated using Equation (24) [32].

Uncertainty Analysis and Experiment Measurement Assessments
In this section, the uncertainties associated with the experimental work are estimated. The following devices were used to record the various data from the experimental work: a pyranometer, a thermocouple, a clamp meter, a thermometer, and a digital anemometer. The standard uncertainty F z can be estimated using Equation (25) [79,80].
Where, Y z is the accuracy of the devices used in the experiment and that can be obtained from the manufacturer's data sheet. Therefore, the uncertainty X(b) can be achieved using Equation (26). Table 2 represents the range, accuracy, and uncertainty of the devices. The total uncertainty error achieved for the present experiment is 3.97%.

Results and Discussion
In this section, the obtained results from the experiment such as weather characteristics, thermal analysis, electrical improvement, economic, and energy payback time analysis are presented and discussed.

Weather Characteristics of the Experimental Period
The details of the weather on the day of the experiment are presented in this section. The solar radiation, ambient temperature, humidity, and wind speed are recorded from morning 08:30 h to 16

Performance of FanLess CPU Heat Sink on the PV Panels
In this section, we discussed the thermal and electrical performance of the two P panels.

Effect of Temperature on PV Panels
The PV temperature is a significant parameter for PV panels; it plays a fundament role in identifying the system's performance. This study used two panels, one modifie PV panel with a fanless heat sink and another PV panel for comparison. Three K-typ thermocouples were used at different locations on each PV panel, giving readings ever 30 min. The temperature profile of the two tested PV panels is shown in Figure 9. Th reduction in temperature is also presented in Figure 9. From Figure 9, as the day start the temperature of the cooled and uncooled PV panels increased until it hit its peak valu

Performance of FanLess CPU Heat Sink on the PV Panels
In this section, we discussed the thermal and electrical performance of the two PV panels.

Effect of Temperature on PV Panels
The PV temperature is a significant parameter for PV panels; it plays a fundamental role in identifying the system's performance. This study used two panels, one modified PV panel with a fanless heat sink and another PV panel for comparison. Three K-type thermocouples were used at different locations on each PV panel, giving readings every 30 min. The temperature profile of the two tested PV panels is shown in Figure 9. The reduction in temperature is also presented in Figure 9. From Figure 9, as the day starts, the temperature of the cooled and uncooled PV panels increased until it hit its peak value at 13:30 h. The maximum temperature for the cooled panel during the experiment is found to be 50.26 • C against 60.19 • C for the uncooled panel. The average temperature reduction achieved between the cooled and referenced modules at the end of the experiment was found to be 6.72 • C. This reduction is relatively significant, especially when this process does not require electric power to cool the PV module; it also requires very little water for the cooling process and therefore can be employed in areas with water scarcity.
The thermal image profiles for both PV panels were recorded around 11:30 am on the day of the experiment. The findings from the thermographic images are presented in Figures 10 and 11. The results from the thermal image show that the temperature of the cooled module ranges between 20-30 • C, that of the referenced module ranges between 31-35 • C. The positive impact of the cooling approach adopted is clearly shown in the thermal images. This confirms the earlier results obtained through the use of the thermocouples.
at 13:30 h. The maximum temperature for the cooled panel during the experiment is found to be 50.26 °C against 60.19 °C for the uncooled panel. The average temperature reduction achieved between the cooled and referenced modules at the end of the experiment was found to be 6.72 °C. This reduction is relatively significant, especially when this process does not require electric power to cool the PV module; it also requires very little water for the cooling process and therefore can be employed in areas with water scarcity. The thermal image profiles for both PV panels were recorded around 11:30 am on the day of the experiment. The findings from the thermographic images are presented in Figures 10 and 11. The results from the thermal image show that the temperature of the cooled module ranges between 20-30 °C, that of the referenced module ranges between 31-35 °C. The positive impact of the cooling approach adopted is clearly shown in the thermal images. This confirms the earlier results obtained through the use of the thermocouples.   The thermal image profiles for both PV panels were recorded around 11:30 am on the day of the experiment. The findings from the thermographic images are presented in Figures 10 and 11. The results from the thermal image show that the temperature of the cooled module ranges between 20-30 °C, that of the referenced module ranges between 31-35 °C. The positive impact of the cooling approach adopted is clearly shown in the thermal images. This confirms the earlier results obtained through the use of the thermocouples.

Electrical Performance of a PV Panel
The voltage and current results for the cooled and uncooled panel are illustrated in Figure 12. According to the data, the maximum voltage achieved for the modified PV panel is 18.99 V, recorded at 12:00 h. Whereas, for the uncooled solar PV panel, its max-

Electrical Performance of a PV Panel
The voltage and current results for the cooled and uncooled panel are illustrated in Figure 12. According to the data, the maximum voltage achieved for the modified PV panel is 18.99 V, recorded at 12:00 h. Whereas, for the uncooled solar PV panel, its maximum voltage was recorded around 11:30 h. However, there is a voltage drop for the un-cooled panel as a result of its relatively high temperature. The average voltage for the cooled and the uncooled PV panels during the experiment was 18.36 V and 17.01 V. It shows that the temperature negatively influences the voltage of the uncooled panel. Figure 13 explains the power output of the tested system during the day of the experiment. The total power output of the PV panels increases as the day progresses; the power output from both panels increases with time thanks to solar insulation until midday. The trend of the power output, however, starts decreasing after midday due to the increasing panel temperatures and reduction in the intensity of solar radiation. The results revealed that the average power of the cooled PV panel is 11.39 W, as against 9.73 W for the module.

Electrical Performance of a PV Panel
The voltage and current results for the cooled and uncooled panel are illustrated in Figure 12. According to the data, the maximum voltage achieved for the modified PV panel is 18.99 V, recorded at 12:00 h. Whereas, for the uncooled solar PV panel, its maximum voltage was recorded around 11:30 h. However, there is a voltage drop for the un-cooled panel as a result of its relatively high temperature. The average voltage for the cooled and the uncooled PV panels during the experiment was 18.36 V and 17.01 V. It shows that the temperature negatively influences the voltage of the uncooled panel. Figure 13 explains the power output of the tested system during the day of the experiment. The total power output of the PV panels increases as the day progresses; the power output from both panels increases with time thanks to solar insulation until midday. The trend of the power output, however, starts decreasing after midday due to the increasing panel temperatures and reduction in the intensity of solar radiation. The results revealed that the average power of the cooled PV panel is 11.39 W, as against 9.73 W for the module.

Electrical Efficiency
The electrical efficiency of the conventional PV panels (uncooled) over modified PV panels (cooled panel) is presented in Figure 14. According to the obtained results, the electrical efficiency for both PV panels experiences a downward trend from the start of the experiment until after 13:30 h due to the increasing temperature of the PV modules during that period. The trend, however, reversed after 13:30 h when both the ambient temperature and the PV module's temperature began to decrease. The average electrical efficiency recorded for the period of the experiment for the cooled PV panel is 14.05%,

Electrical Efficiency
The electrical efficiency of the conventional PV panels (uncooled) over modified PV panels (cooled panel) is presented in Figure 14. According to the obtained results, the electrical efficiency for both PV panels experiences a downward trend from the start of the experiment until after 13:30 h due to the increasing temperature of the PV modules during that period. The trend, however, reversed after 13:30 h when both the ambient temperature and the PV module's temperature began to decrease. The average electrical efficiency recorded for the period of the experiment for the cooled PV panel is 14.05%, against 13.65% for an uncooled PV Panel. The average improvement in electrical efficiency is about 2.98%. The present proposed approach is compared with other published literature as shown in Table 3. It is clear from the literature presented in Table 2 that the current study is either better in terms of results or equal to other forms of cooling methods proposed by other studies. Figure 13. Temperature dependence power output of both PV panels.

Electrical Efficiency
The electrical efficiency of the conventional PV panels (uncooled) over modified PV panels (cooled panel) is presented in Figure 14. According to the obtained results, the electrical efficiency for both PV panels experiences a downward trend from the start of the experiment until after 13:30 h due to the increasing temperature of the PV modules during that period. The trend, however, reversed after 13:30 h when both the ambient temperature and the PV module's temperature began to decrease. The average electrical efficiency recorded for the period of the experiment for the cooled PV panel is 14.05%, against 13.65% for an uncooled PV Panel. The average improvement in electrical efficiency is about 2.98%. The present proposed approach is compared with other published literature as shown in Table 3. It is clear from the literature presented in Table 2 that the current study is either better in terms of results or equal to other forms of cooling methods proposed by other studies.

Exergy Efficiency
The exergy efficiency results achieved from the cooled and uncooled PV panels are presented in Figure 15. A PV system's exergy efficiency is adversely affected by its power output. It can therefore be seen from the results that the profile for the exergy efficiency for the two modules follows the same trend as that of the electrical efficiency. Due to the increase in PV module temperature, the exergy efficiencies declined from the beginning of the experiment until after 13:30 pm, before it started rising again. The exergy of the cooled remained higher at all times during the experiment which suggests that the proposed cooling method is able to keep the temperature of the PV module under control. Consequently, the average exergy efficiencies for cooled PV and uncooled panels are 7.88% and 4.54%, respectively. From the results, it is evident that the modified PV panel recorded relatively high exergy efficiency.

•
Average difference in temperature is 10 °C.

Exergy Efficiency
The exergy efficiency results achieved from the cooled and uncooled presented in Figure 15. A PV system's exergy efficiency is adversely affected output. It can therefore be seen from the results that the profile for the exe for the two modules follows the same trend as that of the electrical efficien increase in PV module temperature, the exergy efficiencies declined from of the experiment until after 13:30 pm, before it started rising again. The cooled remained higher at all times during the experiment which suggests posed cooling method is able to keep the temperature of the PV module u Consequently, the average exergy efficiencies for cooled PV and uncool 7.88% and 4.54%, respectively. From the results, it is evident that the modi recorded relatively high exergy efficiency.   Table 4 depicts the cost of the various items used for the construction of the PV panels. Table 5 depicts the estimated LCE of a PV plant. The experiment was performed in the Russian Federation, where there are poor climatic conditions. Therefore, we assumed two scenarios to calculate the LCE. In the first scenario, the effective period for Russian conditions starts from May to the middle of August, which is about 105 days a year; this is the period with the best weather conditions in the area where the experiment is conducted. The second scenario i.e., 365 days, assumes that the entire year experienced good weather conditions for the generation of electrical energy from the PV module. Furthermore, it is also assumed for the purposes of this estimation that the PV modules worked effectively for a period of 10 h daily. Through the experiment, it was found that the power generated by the cooled PV panel is 11.39 W against 9.73 W by the uncooled panel. For the purposes of this calculation, it is also assumed in this study that equal power is generated throughout the year. This means a total electricity of 11.95 kWh and 10.216 kWh would be generated by the cooled and uncooled modules, respectively, for scenario 1. Using the data provided in Tables 5 and 6, the LCE of the cooled and uncooled modules are estimated to be 0.96 USD/kWh and 0.61 USD/kWh. The power that would be generated for the entire year (i.e., 365 days) for the cooled PV panel is 41.5735 kWh, and for the uncooled panel is 35.5145 kWh. The results suggest that for the 365 days, the LCE of the cooled PV panel is 0.277 USD/kWh and 0.206 USD/kWh for the uncooled panel.

Energy Payback Time
The embodied energy computations achieved for the cooled and uncooled PV panels are presented in Table 6. Due to the extra materials used in the cooling of the cooled PV, its embodied energy is found to be greater than that of the uncooled PV. The embodied energy for the cooled and uncooled modules were found to be 438.53 kWh and 427.50 kWh, respectively. The estimated result show that the EPBT (energy base) for the cooled PV panel is 10.54 Year against 12. 16 Year for the uncooled PV panel. Based on the EPBT results, it can be seen that the embodied energy for the extra materials used for the cooling process affected the EPBT years for the cooled module. It therefore suggests that appropriate mechanisms have to be put in place to reduce the embodied energies of the various materials used for the construction. Manufacturers need to produce materials with lower embodied energy.

Conclusions
In this study, the fanless heat pipe sink was employed for thermal management of a PV system. The main objective of this study was to evaluate the effectiveness of using a fanless heat pipe sink to cool and enhance the performance of a PV module. The electrical energy, exergy, economics, embodied energy and the energy paybacks of two PV modules (i.e., cooled and uncooled) were evaluated. From the present research, the following significant conclusions have been drawn from the experiment: The proposed cooling mechanism for reducing the PV panel temperature proved to be adequate. The LCE acquired for the present experiment is a bit higher for the cooled panel because of the extra cost associated with the materials used for its construction. Therefore, we recommend that manufacturers produce materials for the market with lower embodied energy due to the development of advanced technologies.