Constant exposure of a photovoltaic (PV) panel to sunlight causes it to overheat and, consequently, its rated efficiency decreases leading to a drop in its generated power. In this study, a PV panel was tested under standard test conditions in a halogen lamp solar simulator at different solar irradiance values. The PV panel was then fitted with heat dissipating fins and measured under identical test parameters; thereafter, repurposed materials such as high-density polyethylene (HDPE) and plastic bags were, separately, added to the PV panel with fitted heat-extraction fins and the performance was evaluated again. Passively cooling the PV panel with fins and repurposed materials resulted in a 22.7% drop in the PV panel’s temperature, while an 11.6% increase in power output occurred at 1000 W m-2. Utilizing repurposed waste materials in PV cooling improves a panel’s efficiency and saves the environment from the ecological effects of dumping these materials.
Photovoltaic (PV) cells’ efficiency for converting sunlight into electricity is low, and it drops even more as the cells are heated when exposed to a great deal of solar irradiance. There is an approximately 0.25% and 0.5% drop in efficiency for amorphous and crystalline silicon cells, respectively, for every 1°C increase in the cells’ temperature [
PV cooling has been widely researched [
PCMs have been extensively investigated as heat-extraction additive components to PV panels yielding favorable outcomes in increasing the relative efficiency by reducing the PV panels’ surface temperatures [
State-of-the-art PV passive cooling reviews [
The disposal of plastic creates plenty of negative environmental impacts. Despite the fact that plastic is a durable material, it poses a considerable threat to the environment as it decomposes slowly and its incineration could lead to the emission of poisonous gases into the atmosphere. In addition to that, producing plastic proved to have a harmful effect on the environment as a large number of pollutants, together with enormous amounts of fossil fuels, are needed during the production process. Recycling is not always a viable option in many parts of the world; therefore, reducing the nonbiodegradable waste and using it for PV cooling can be beneficial to both the environment and to the efficiency and output power of PV panels. Renewable energy generation combined with environmental protection support the new trend of sustainable cities’ design [
The overheating problem in PV panels will be experimentally investigated. A PV panel will be prepared according to the test requirements; it will be tested under laboratory conditions. Halogen lights will be set to the required intensity, and the PV panel’s front and back temperatures will be monitored. The temperature will be recorded after ensuring that a steady state was reached.
Heat loss from the PV panel is important for the fins’ design. To estimate the heat loss from the PV panel, a mathematical model will be proposed and solved analytically. The following assumptions were considered:
Steady state, one-dimensional problem in the direction of flow. Thus, the temperatures of the glass cover, solar cells, and plates vary only in the direction of working fluid flow The capacity effects of the glass cover, solar cells, and back plate have been neglected
The convection coefficients are a mixture of both forced and free convections. They differ in velocity, air temperature, and geometry of the PV panel. In this research, not much attention was paid to forced convection. On the contrary, free convection is the main focus of attention. Free convection coefficients are derived from the base of a heated inclined plate for the entire range of Rayleigh numbers that were assigned to the Nusselt number (Nu). All equations were provided by [
As for the tilted panels, the net heat, which is dissipated through radiation, was among the panel, the sky, and the ground and was given by the following:
The degree of heat transfer could be escalated through expanding the surface where convection takes place. This can be achieved through the application of fins, which stretch from end to end on the backside of the PV panel. The fin material’s thermal conductivity could have a considerable impact on the circulation of temperature across the fin. Ideally, the fin material should possess a high level of thermal conductivity in order to diminish the variations in temperatures from top to bottom.
The fins’ configurations were selected based on a few parameters such as weight, space, and cost. On one hand, fins can have simple designs such as rectangular, triangular, parabolic, annular, and pin shapes. On the other hand, fins’ design can be complicated such as spiral shapes. In this study, rectangular fins were selected from three known and easy-to-install configurations. These configurations were (i) rectangular fins, (ii) parabolic fins, and (iii) pin fins. Table
Fin efficiency based on design type.
Design | Efficiency ( |
---|---|
Rectangular fin | 84% |
Parabolic fin | 78.4% |
Pin fin | 81.5% |
The rectangular fin shape allows airflow in one direction only; if the air blows from a transverse direction, the fin will create high drag on the panel and will negatively affect the heat transfer. To overcome the flow direction problem, a perforated fin was used. Perforations in the rectangular fin allow the air to flow in all directions and reduce the amount of material used in the fin, thus making it lighter in weight. Perforated, lighter-weight fins are cheaper and exert less stress on the panel.
The perforated fin is shown in Figure
A perforated fin that was attached to the backside of a PV panel to act as a heat sink and to reduce the PV panel’s temperature.
The fin’s heat transfer rate was assessed using the
Fins were utilized to boost the heat transfer from a particular surface by expanding the surface area. Nevertheless, the fins installed were resistant to heat transfer through conduction from the designated surface. Therefore, any increase in the heat transfer rate could not be guaranteed. To address this issue, fin efficacy,
Calculations of the fins’ effectiveness.
Area of PV panel | 0.156 m2 |
Ambient temperature | 25°C |
Heat convection coefficient ( |
3.06 W m-2 K-1 |
Length of the fin ( |
0.15 m |
Width of the fin ( |
0.31 m |
Thickness of fin ( |
0.001 m |
Material’s thermal conductivity ( |
237 W m-1 K-1 |
Number of fins | 21 |
Finned area | 1.56 m2 |
Unfinned area | 0.15 m2 |
Heat rate from the finned area ( |
110.8 W |
Heat rate from the unfinned area ( |
10.117 W |
Backside temperature of PV panel | 47°C |
Fin’s cross-sectional area ( |
0.00031 m2 |
The effectiveness of fin ( |
11.455 |
The efficiency of the fin ( |
84.2% |
There were many factors considered when selecting the fins’ material to guarantee maximum heat conduction through the fins. Those factors involved weight, thermal conductivity, and cost. Table
Merits and demerits of common fins’ materials.
Advantages | Disadvantages | |
---|---|---|
Aluminium | Relatively lightweight material ( |
Relatively high cost |
Copper | A high thermal conductivity of 401 W m-1 K-1 |
Relatively heavyweight material ( |
Iron | Low cost | Relatively low thermal conductivity |
The experimental investigation aimed at evaluating the PV panel after having been fitted with heat-extraction fins and later with fins and repurposed materials, as illustrated in Figure
Schematic of a PV panel fitted with repurposed materials and fins.
A locally designed solar simulator, shown in Figure
(a) Solar simulator, (b) PV panel used, (c) backside of the PV panel with paste for fin installation, (d) installed perforated aluminium fins, and (e) PV analyser.
A 30 W PV panel, shown in Figure
The PVA-1000 PV Analyser Kit is a 1000-volt
The ambient temperature, as well as the PV panel’s temperature, was measured through the application of a Type K thermocouple (SE029) exposed junction and a 0.2 mm PTFE insulated twisted pair conductor. The thermocouples were positioned on the item’s surface to measure its temperature. Consequently, the measured temperature was a mixture of the surface and the ambient temperatures. The measurements of the thermocouples were automatically recorded via a Pico Technology Environment Quad Temperature Converter together with a Pico Technology Environment DataLogger. The distribution of thermocouples is shown in Table
Distribution of thermocouples.
Thermocouple | Location |
---|---|
A | Ambient temperature |
B, C | Backside temperature |
D, E | Surface temperature |
F | Frame temperature |
J | Fin temperature |
K | Repurposed materials temperature |
All measurements were conducted in a laboratory setting to mimic the behaviour of the sun on a typical day; when the sun rises, its irradiance is low and when it is at its hottest, its irradiance reaches its peak and then starts to decrease until it diminishes. Hence, the PV panel was placed under the solar simulator with 500 W m-2 irradiance to simulate solar radiation in the morning (8 a.m.). The solar simulator’s temperature started to rise gradually, and as it became stable, the irradiance of the solar simulator was adjusted to 750 W m-2, late morning (10 a.m.). Similarly, when the temperature was stable once again, the irradiance was adjusted to 1000 W m-2, noon (12 p.m.). Once the temperature reached a steady state, the irradiance was adjusted back to 750 W m-2, afternoon (2 p.m.). Finally, irradiance was dropped to 500 W m-2, late afternoon (4 p.m.). All tests were conducted under identical conditions and no wind speed.
The surface temperature and the output power of the PV panel measurements were recorded at different trials and consistently resulted in similar outcomes. The PV panel’s surface temperature increased with the rise in solar irradiance until it reached a steady maximum of 106°C at 1000 W m-2. As expected, the PV panel’s output power increased with the increase in solar irradiance. Figure
Measurement of the PV panel at three different solar irradiances to simulate morning, late morning, noon, afternoon, and late afternoon (a) surface temperatures of three trials and (b) average surface temperature and average output power.
The PV panel was fitted with perforated aluminium fins as illustrated in Figure
Additives to the PV panel between its backside and the installed fins: (a) HDPE grain wraps and (b) folded plastic bags.
The results in Figure
Comparison of results for the as-is PV panel and the PV panel modified using fins, fins+HDPE, and fins+PBs for (a) a PV panel’s surface temperature and (b) a PV panel’s output power.
The certainty and reproducibility analyses were considered. The maximal difference in temperature measurements between the tests was 1.7°C, and the relative error between them was 1.6%. As a result, no corrections were required to determine the fins’ effects on temperature. The maximum error for the measured PV panel was 2.4% with a maximum relative uncertainty of 0.32.
The efficiency was calculated according to equation (
Measure efficiencies of the PV panel with no fins, fins, fins+HDPE, and fins+PBs.
The PV panels’ conversion of solar radiation into electricity decreases with the rise in the panels’ temperature. Therefore, it is important to cool PV panels to maintain their rated conversion efficiencies. In this study, a hybrid passive cooling system was proposed that consisted of aluminium heat-extraction fins along with repurposed materials, i.e., HDPE and plastic bags. Recycling is not always an option, so repurposing certain materials can reduce nonbiodegradable waste and cool down PV panels.
The results obtained showed that modifying a PV panel with fins and repurposed materials reduced the temperature of the panel and increased its efficiency. Different solar irradiance values using a solar simulator, in a controlled laboratory setting, were utilized to mimic the sun’s behaviour on a typical day. The highest temperature drop of 23.7°C at 1000 W m-2 was observed when the PV panel was cooled with fitted fins and HDPE grain wraps. The highest output power was attained at 1000 W m-2 when the PV panel was cooled with fitted fins and folded plastic bags showing a rise of 11.6%. Lastly, the highest efficiency increase was recorded at 1000 W m-2 when fitted fins and folded plastic bags were used to cool down the PV panel; all those values were compared to the PV panel’s measurements prior to making cooling modifications.
Passively cooling PV panels can effectively reduce their temperatures and enhance their thermal and electrical performance. Using repurposed materials that can otherwise be harmful to the environment if thrown away reduces the cost of raw cooling materials; at the same time passive cooling requires no energy input for the cooling process. The main drawbacks to the utilization of this repurposed material-based system are the collection of those materials before disposal and the possible labour cost of installation. However, if those disadvantages are addressed, the new PV panel cooling system could prove to be an important step in maintaining the rated efficiency and reducing negative environmental impact.
Surface area of PV panel (m2)
Cross-sectional area of fin (m2)
Cross-sectional area of the fin at the base (m2)
PV panel’s maximum efficiency
Fin’s effectiveness
PV panel emissivity
Ground emissivity
Incident solar irradiance (W m-2)
Conventional heat transfer coefficient around the fin (W m-2 K-1)
Heat convection coefficient of the front of the PV panel (W m-2 K-1)
Heat convection coefficient of the back of the PV panel (W m-2 K-1)
High-density polyethylene
Fin material’s thermal conductivity (W m-2 K-1)
Fin’s length (m)
Fin parameter (m)
PV panel’s maximum power output (W)
Photovoltaic
Phase change material
PV panel’s tilt angle (°)
Heat dissipation through convection (W)
Fin’s heat transfer rate rule
Heat dissipation through radiation (W)
Ambient temperature (K)
Fin’s base temperature (K)
Ground temperature (K)
Room temperature (K)
PV panel temperature (K)
Effective sky temperature (K)
Stefan-Boltzmann’s constant (5.67 × 10-8 W m-2 K-4).
The measured data used to support the findings of this study are included within the article.
The authors declare that there is no conflict of interest regarding the publication of this paper.