Introduction

The increasing global demand for renewable energy has underscored the importance of optimizing solar energy systems. Solar panels, particularly monocrystalline solar panels, are among the most efficient photovoltaic technologies available today. However, their performance is influenced by several factors, including environmental conditions, material properties, and substrate characteristics. The substrate, a material on which the solar panel is mounted, plays a crucial role in determining the operational temperature, power output, and overall efficiency of the panel. Understanding the effects of different substrates on these parameters is vital for improving the performance and reliability of solar energy systems.

The albedo effect influences temperature and can have significant implications for solar panel efficiency and thermal management. Albedo refers to the measure of the reflectivity of a surface or material. It is defined as the ratio of reflected solar energy to the total incoming solar radiation. Surfaces with a high albedo, like snow or white roofs, reflect more sunlight and absorb less heat, making them cooler. Conversely, surfaces with low albedo, such as asphalt or dark soil, absorb more sunlight, contributing to higher temperatures. Albedo values range from 0 (no reflection) to 1 (total reflection).

The operating temperature of a solar panel is directly linked to its efficiency. Excessive heat can reduce the power conversion efficiency of a solar panel1,2,3, making thermal management a critical factor in solar energy optimization. Similarly, the power output of a panel is sensitive to the thermal and physical properties of the mounting substrate4,5,6. By investigating how different substrates interact with monocrystalline solar panels, researchers can identify practical ways to enhance their performance, particularly in diverse climatic conditions.

Research indicates that substrates with high thermal conductivity, such as aluminium or specific composites, effectively dissipate heat, thereby reducing the operational temperature of solar panels5,7,8. Lower temperatures are associated with improved efficiency, as excessive heat can degrade photovoltaic (PV) performance. For instance, a study on flexible PV systems emphasized that substrate choice directly impacts long-term stability and efficiency, with temperature mitigation being a key benefit9,10. Other studies have highlighted how substrate materials affect power output. Substrates with reflective properties can optimize light absorption, while materials prone to overheating may cause power losses11,12,13. Advances in material science, including the use of glass and polymer substrates, have been linked to durability and performance improvements14.

These findings align with earlier work focused on thermal management in solar panels, which emphasized the importance of maintaining an optimal temperature range to prevent efficiency losses15,16,17. Experimental setups comparing different substrates consistently report efficiency gains when using thermally optimized materials18,19,20.

Table 1 compares the current study with similar work done by other researchers. This comparison highlights how the current study contributes to the existing literature.

Table 1 Related studies.
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By building on these studies, the present research aims to further explore how substrates specifically influence monocrystalline solar panels, providing practical recommendations for improving solar energy systems.

The specific objectives of this study were to:

i. determine the effect of substrates on the operating temperature of a solar panel;

ii. analyze the effect of the substrate on the power output of a solar panel; and.

iii. analyze the effect of substrates on the efficiency of a solar panel.

Methodology

The study involved experimentation which was carried out in a clean environment free from shade. Cavadini & Cook’s22 experimental design was used since there is an exchange of heat between the roof and the panel. Six set-ups containing solar panels were mounted on different roofing materials of iron sheets, tiles, wood, grass and concrete. The experiment was left to run for five days per week for six months and the data was collected in an interval of one hour.

Equipment/ apparatuses

Several apparatuses were used which include: clean and new identical solar panels, substrate materials (concrete, iron sheet, wood, grass, ground soil and roof tiles), temperature sensors; to measure temperature, solar radiation sensors to measure solar irradiance, multimeter to measure solar output voltage and output current.

The selection of iron sheets, roof tiles, concrete, wood, grass, and ground soil as substrates for studying the efficiency of a monocrystalline solar panel is justified by their prevalence in real-world installations and their diverse physical and thermal properties. Iron sheets and roof tiles represent common roofing materials with contrasting thermal conductivities, making them critical for understanding solar panel performance in urban and rural contexts. Concrete is widely used for flat rooftops, especially in urban areas, while wood reflects the needs of structures in rural and suburban settings. Grass and ground soil, as natural substrates, are significant for ground-mounted solar installations, particularly in open fields and agricultural areas. This diverse selection ensures comprehensive representation of environmental and construction contexts, improving the generalizability of the findings. It also provides practical insights for optimizing solar panel installations across various substrates and climatic conditions.

Durability considerations for substrates

Iron Sheets is susceptible to corrosion if not coated or galvanized, especially in humid or coastal regions. It can withstand heavy loads and temperature variations, making it structurally stable over long periods. Proper surface treatment and maintenance (e.g., painting or galvanization) are required to extend the lifespan and prevent corrosion-related efficiency losses.

Roof Tiles is highly durable, with a typical lifespan of 30–50 years depending on the material (e.g., ceramic or clay). Resistant to UV radiation and weathering, but prone to cracking under heavy impact or freeze–thaw cycles. Stable support for long-term installations, but cracked or broken tiles can compromise structural integrity and require periodic replacement.

Concrete has a lifespan of 50 + years with proper curing and maintenance; however, exposure to moisture, freeze–thaw cycles, and carbonation can degrade it over time. It resists most environmental stresses but can develop cracks, impacting surface stability. Concrete is a durable substrate for urban installations, but periodic inspections and repairs may be needed to maintain surface quality.

Wood is susceptible to rot, warping, and termite attacks, especially in humid or wet environments. Treated wood can last 10–20 years, depending on environmental conditions and maintenance. While cost-effective, wood requires regular treatment and protection to maintain its integrity as a solar panel substrate.

Grass is highly variable due to natural degradation, seasonal changes, and maintenance (e.g., mowing, and irrigation). The substrate can erode or lose stability over time, especially under continuous exposure to rain and wind. Long-term installations may require stabilization measures, such as planting hardy grass species or using support structures to prevent soil erosion.

Ground Soil is highly dependent on soil type, moisture content, and erosion risks. Clay-rich soils may crack during dry periods, while sandy soils are prone to shifting. Erosion from rain and wind is a significant concern, particularly in sloped installations. To maintain substrate durability, ground-mounted solar panels may require additional measures, such as gravel layers, soil stabilization, or anchoring systems.

Future work could include experimental evaluations of substrate degradation under accelerated ageing conditions to assess their performance over extended periods.

Selecting a site

For a solar panel to work well a good site is needed23. The site has the following qualities:

  1. 1.

    Sun hours: solar panels perfume under maximum sunlight24,25,.

  2. 2.

    Tilt angle: Solar panels need a maximum tilt angle for high power output26.

  3. 3.

    Shade: Shade is one of the factors that affect solar panels’ performance therefore the area should be free from tree shades cloudy shades and shades from other solar panels2728:). The experimental was setup in an area that is free from potential shading throughout the testing period.

  4. 4.

    Wind Speed: Wind speed can have both direct and indirect effects on solar panel performance24. The experiment was conducted in a location that is shielded from wind.

  5. 5.

    Dust Accumulation: Dust accumulation on the surface of the solar panel can have several negative effects: Reduced Efficiency, Thermal Effects24. The study included regular cleaning intervals.

Operational temperature limits for Monocrystalline solar panels

Monocrystalline solar panels typically have specific temperature ranges within which they can function optimally. These limits are defined by both the temperature coefficient and maximum operating temperature.

Maximum operating temperature (Tmax)

The maximum operating temperature for most monocrystalline solar panels is around 85 °C to 90 °C (185°F to 194°F)24. Exceeding this temperature can cause damage to the solar cells, leading to reduced efficiency, potential failure, or degradation of the panel’s lifespan. At these high temperatures, the materials in the panel (such as silicon) can begin to degrade, affecting the panel’s structural integrity and power output.

Temperature coefficient of power

Monocrystalline panels have a temperature coefficient of power that typically ranges from −0.3% to −0.5% per degree Celsius28. This means that for every degree Celsius increase in temperature above the standard test conditions (25 °C), the power output of the solar panel will decrease by 0.3% to 0.5%. This coefficient is an important factor in understanding how temperature variations affect panel efficiency.

Operating temperature range

Most monocrystalline panels are designed to operate efficiently within a temperature range of −40°C to + 85 °C28. However, efficiency typically decreases as the temperature rises above 25 °C, which is the standard test condition (STC) for panel performance measurements. In regions with high ambient temperatures, the actual operating temperature of the panel can be significantly higher than the ambient temperature due to the heat absorbed from sunlight and the lack of cooling mechanisms. For example, under direct sunlight, a solar panel can reach temperatures 20–30 °C higher than the surrounding air28.

Experimental setup

Cavadini & Cook’s22 experimental design was used since there is an exchange of heat between the roof and the panel. Six setups each containing a clean solar panel was placed on roofing materials with three temperature sensors attached to it. All panels were installed touching the roof surface (Picture in Appendix). The tilt angle was 00 because most people install solar panels using this design and all facing in the same direction to receive the same amount of radiation. In addition, a tilt angle of 00 helps to overcome the limitations of tilt angles such as drainage and self-cleaning challenges. While a 0° tilt angle may be practical and cost-effective for some installations, adjusting the tilt angle for specific geographic and seasonal conditions generally improves solar panel performance by maximizing sunlight absorption and minimizing heat buildup. The experiment was conducted for six months for adequate data collection, all at the same time receiving the same weather conditions. The area of the panel under the shading of the panel was measured.

Data collection

Temperature sensors (thermocouples) measured the upper and lower surfaces of each material. The back temperature of the panel was measured by using a thermocouple placed below the panel; the temperature at the front part of the panel was also measured. The readings were collected in an interval of one hour a day. The absorbance and reflectance of material properties were obtained from Shanmugam et al.29 table of material properties. The front and back temperature was used to determine the cell temperature of the panel according to Eq. (1)30:

$${T}_{cell }= \frac{{T}_{back}+{T}_{front}}{2}$$
(1)

where Tfront is the front temperature of the surface of the panel and Tback is the surface temperature at the back of the panel, Tcell is cell temperature.

The cell temperature was used to determine efficiency from Eq. (2)31:

$$\eta \, = \,\eta_{{{\text{ref}}}} (\left( {{1} - \beta } \right) \, ({\text{T}}_{{{\text{Cell}}}} - {\text{T}}_{{{\text{ref}}}}$$
(2)

Where η is efficiency at operating temperature, β is temperature coefficient of the panel, Tcell is the cell temperature and Tref is the reference temperature.

The current and voltage were measured using a multimeter which was used to calculate power output.

Statistical data analysis was carried out using the Excel package. Excel is well-suited to the scope of this research, enabling efficient and effective analysis of data related to solar panel efficiency. It provides sufficient statistical functionality to draw meaningful conclusions without the need for specialized software, making it an excellent choice for researchers in developing countries or situations with limited resources.

Results

In all setups, the surface temperatures of the material were taken in an interval of one hour for five days per week from 8:00 am to 6:00 pm for six months. The average temperature of every hour was recorded in a table for each material. The thermal and physical properties of the selected substrates are presented in Table 2. Table 3 shows the parameters of the solar panel used. Tables 4, 5, 6, 7, 8, 9 show the parameters of a solar panel when installed on the different substrates.

Table 2 Thermal and physical properties of the selected substrates.
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Table 3 Parameters of solar panel used.
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Table 4 Performance Parameters of a solar panel when installed on iron sheet.
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Table 5 Parameters of a solar panel when installed on a roof tile.
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Table 6 Parameters of a solar panel when installed on concrete.
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Table 7 Parameters of a solar panel when placed on wood.
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Table 8 Parameters of a solar panel when place on dry grass.
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Table 9 Parameters of a solar panel placed on ground soil.
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Panel temperature

In all setups, the surface temperature was seen to increase as the solar radiation increased. Also, the cell temperature was seen to increase as the surface temperature of the material increases. A graph of panel temperature against time was plotted as seen in Fig. 1. Iron sheet had the highest temperature of 79 0c followed by roof tiles at 70 0c, then concrete at 58.8 0c, then wood at 50.5 0c, then grass at 41.2 0c while ground soil had the lowest temperature of 42.3 0c. The results were further taken for correlation analysis. The correlation between cell temperature and surface temperature of each material was calculated and the results are shown in Table 10. For all results, the correlation was highly positive. Iron sheet had a correlation of 0.954, meaning that a rise in surface temperature leads to a 95.4% rise in the cell temperature, for roof tile it was 0.973, meaning that a degree rise in surface temperature leads to 97.4% in cell temperature. For concrete it was 0.964, meaning one degree rise in surface temperature leads to 96.4% in cell temperature, for wood it was 0.88, which means one degree rise in surface temperature leads to an increase of 88.4% in cell temperature, for grass it was 0.954, meaning one degree rise in surface temperature leads to 95.4% in cell temperature while for ground soil was 0.846, meaning one degree rise in surface temperature leads to 64.5% in cell temperature. The correlation between cell temperature and surface temperature was analyzed. For the iron sheet, the R-square was 0.9973, meaning that the surface temperature on the material describes 99.73% of the cell temperature. For the roof tile R- squared was 0.9329, meaning that the surface material of the roof tile describes 93.29% of cell temperature. For concrete it was 0.9782, meaning that the surface temperature on the concrete describes 97.82% of cell temperature. For wood it was 0.9881, meaning that surface temperature describes 98.81% of cell temperature. For grass it was 0.9896, meaning that the surface temperature describes 98.96% of cell temperature and ground soil was 0.9967, meaning that surface temperature describes 99.67% of cell temperature. Figures 2, 3, 4, 5, 6, 7 show the scatter graph of cell temperature against surface temperature for all the substrates. ANOVA analysis was carried out. The results show that there was a significant difference between the cell temperatures of the different substrates (Table 11). A post-ANOVA (Tukey’s) test was carried out to determine the significant difference between specific pairs of substrates. Tukey’s test provides pairwise comparisons between the mean temperatures of solar panels placed on different substrates (Table 12).

Fig. 1
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A graph of variation of cell temperature with time of different materials.

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Table 10 Results from correlation coefficients of surface temperature and cell temperature.
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Fig. 2
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Scatter graph of cell temperature against surface temperature of iron sheet.

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Fig. 3
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A scatter graph of cell temperature against surface temperature for tiled roof.

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Fig. 4
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Scatter graph of cell temperature against surface temperature for panel on concrete.

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Fig. 5
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A Scatter graph of cell temperature against surface temperature for a panel on a wood.

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Fig. 6
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A scatter graph of cell temperature against surface temperature for grass.

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Fig. 7
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A scatter graph of cell temperature against surface temperature for ground soil.

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Table 11 Results from ANOVA of solar panel temperature.
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Table 12 Results from Tukey test for solar panel temperature.
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To know the range of temperature difference between materials in the setup, a 95% confidential interval was carried out. The results are shown in Table 13. The results show that ground soil produced the lowest mean temperature while iron sheets produced the highest mean temperature.

Table 13 Results from 95% confidential interval for solar panel temperature.
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Statistical significant differences in the temperature of the solar panel cells and backs (Tcell and Tback) across substrates imply that certain materials influence the heat absorption and dissipation characteristics more effectively than others. Statistically significant differences in Tcell or Tback suggest that the choice of substrate plays an important role in managing the thermal environment of the panel. Grass and Soil show lower temperatures compared to concrete and Iron sheet, it would be advisable to install panels on cooler substrates to avoid the negative impact of excessive heat on panel performance and lifespan.

Power output

The power output of each material was calculated, and the results show that the power output of each material reduces as cell temperature increases. Figure 8 shows a graph of the variation of power out with time of different materials. The correlation analysis of power output and temperature for each material was calculated. The results show that there was a strong negative correlation, showing that an increase in temperature leads to a drop in power output as shown in Table 14. The correlation of the iron sheet was −0.821, meaning a degree rise in cell temperature leads to a drop of 82.1% in power output. Roof tile had −0.863, meaning that a degree rise in cell temperature leads to a drop of 86.3% in power output. Concrete was-0.769, meaning that one one-degree rise in cell temperature leads to a drop of 76.9% in power output. Wood was −0.818, meaning a degree rise in temperature leads to a power drop of 81.8% in power output. Grass was −0.945, meaning one one-degree rise in temperature leads to a drop of 81.8% and ground soil was −0.863, meaning that a one-degree rise in temperature leads to a power drop of 86.3%. To determine the relationship between cell temperature and power output, the results were later taken for regression analysis and R-squared values were obtained. Iron sheet had 0.7867, meaning that cell temperature determines 78.67% of power output, roof tiles had 0.9382, meaning that cell temperature determines 93.82% of power output, concrete had 0.985, meaning that cell temperature determines 98.5% of power output, wood had 0.9881, meaning that cell temperature determines 98.81% of power output, grass had 0.8983, meaning that cell temperature determines 89.83% of power output, and ground soil had 0.9708, meaning that cell temperature 97.08% of power output. Figures 9, 10, 11, 12, 13, 14 show the scatter graph of power output against panel temperature for the different substrates.

Fig. 8
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A graph showing variation of power out with time of different materials.

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Table 14 Results from correlation coefficient of cell temperature and power output.
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Fig. 9
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Scatter graph of power output against cell temperature for iron sheet.

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Fig. 10
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A scatter graph of power output against cell temperature for roof tile.

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Fig. 11
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A scatter graph of power output against for a cell temperature for a concrete.

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Fig. 12
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A Scatter graph showing power output against cell temperature for a panel placed on Wood.

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Fig. 13
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A scatter graph of power output against cell temperature for grass.

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Fig. 14
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A scatter diagram of power out against cell temperature for ground soil.

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To know whether the power output of all setups was significantly different the results were tested with ANOVA. The results show that for all setups the power output was significantly different as shown in Table 15. To determine the significant difference between the pairs of materials the results were taken for the Tukey test. The results show that there is a significant difference between some groups as shown in Table 16.

Table 15 Results from ANOVA of power output.
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Table 16 Results from Tukey test for power output.
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To know the range of power output difference between materials in the setup, a 95% confidential interval was carried out. The results are shown in Table 17. The results show that ground soil produced the highest power while iron sheets produced the lowest power.

Table 17 Results from 95% confidential interval power output.
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A statistically significant result for power output indicate that different substrates cause substantial differences in the amount of energy generated by the panels. This is important for assessing the overall energy yield of a solar installation. Certain substrates lead to lower power output, such as concrete or metal, it may be necessary to select substrates that help with temperature regulation or heat dissipation to maximize power generation. For example, panels placed on materials like grass, which might have better heat dissipation due to lower surface temperatures, could generate more power.

Efficiency

The efficiency of the material was seen to reduce as cell temperature increased. Figure 15 shows a graph of efficiency against time for different materials. The lowest efficiency was achieved at mid-day when the temperature was highest. The highest efficiency was in ground soil (21.1%), followed by grass (19.6%), followed by wood (17.95%) followed by concrete (16.2%) followed by roof tile (14.3%) and finally to iron sheet (11.5%). The results were taken for correlation analysis using the Excel package to determine the correlation between cell temperature and efficiency. The results show that there is a high negative correlation, meaning that an increase in cell temperature leads to a reduction in efficiency as shown in Table 18. The iron sheet had a correlation of −0.945 which means one degree rise in temperature leads to a reduction of 9.6% in efficiency, roof tile had −0.955, meaning one degree rise in cell temperature leads to 95.5% in efficiency, concrete had −0.936, means one degree rise in cell temperature leads to 93.6% reduction in cell temperature, the wood had −0.945, meaning one degree rise in temperature leads to a reduction of 94.5% of efficiency, the grass was −0.909, meaning one degree rise in cell temperature leads to 90.9% reduction in efficiency, while ground soil had −0.864, meaning that one degree rise in cell temperature leads to reduction of 86.4% in efficiency.

Fig. 15
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A graph of efficiency against time for different materials.

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Table 18 Result from correlation coefficient of cell temperature and efficiency of each substrate.
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The result was then taken for regression analysis using an Excel package to determine the relationship between temperature and efficiency, iron sheet had R- squared of 0.9102, meaning that cell temperature determines 91.02 efficiency, roof tiles had R- squared of 0.9561, meaning cell temperature determines 95.61% of efficiency, concrete had R- squared of 0.9885, meaning that cell temperature determines 98.855% of efficiency, wood was 0.9125 which means cell temperature determines 91.25% of efficiency, grass had 0.9967, meaning that cell temperature determines 99.67% of efficiency and ground soil was 0.9014, meaning that cell temperature determines 90 0.14% of efficiency. Figures 16, 17, 18, 19, 20, 21 show a scatter graph of efficiency against panel temperature for the different substrates.

Fig. 16
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A scatter graph of efficiency against cell temperature for a panel on iron sheet.

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Fig. 17
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A scatter graph of efficiency against cell temperature for panel placed on roof tiles.

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Fig. 18
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A Scatter graph of efficiency against cell temperature for concrete.

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Fig. 19
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A scatter graph of efficiency against cell temperature for wood.

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Fig. 20
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A scatter graph of efficiency against panel temperature for grass.

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Fig. 21
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A scatter graph of efficiency against cell temperature for ground soil.

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The ANOVA test of efficiency was carried out to determine whether the efficiency was statistically different. The p-value was less than 0.005 which means that the efficiency of all setups was statistically different as shown in Table 19. A post-ANOVA test was carried out using the Tukey test. The Tukey test in Table 20 provides pair wise comparisons of the efficiency of solar panels installed on different substrates.

Table 19 Results from ANOVA for efficiency.
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Table 20 Results from Tukey test for efficiency.
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The 95% confidential interval was carried out on efficiency to determine the range of efficiency. Ground soil had the highest efficiency while iron sheet had the lowest efficiency as shown in Table 21.

Table 21 Results from 95% confidential interval for efficiency.
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Statistical significance suggests that the choice of substrate (such as iron sheet, roof tile, or soil) has a notable impact on the efficiency (η) of the solar panel. This finding is crucial for installers when selecting the right substrate. For example, panel on concrete substrates exhibit significantly lower efficiency, it would be prudent to recommend more efficient alternatives, like grass, in environments where efficiency is a priority.

Discussion

The measured Tcell values ranging from 31.82 °C in the morning to 79.33 °C in the afternoon. If the measured Tcell exceeds 60 °C-70°C, the panel is operating under higher thermal stress, and its efficiency will start to degrade. For instance, a temperature of 79.33 °C at 1:00 PM in the study is above the optimal operational range. As temperatures exceed this range, the temperature coefficient leads to a decrease in power output. This effect can be observed in the efficiency drop (η), which is lower during midday hours in the data, correlating with higher temperatures. The back temperature provides insight into the thermal management of the panel. Higher back temperatures, such as those recorded in the afternoon (e.g., 74.82 °C), indicate potential challenges in heat dissipation. Proper ventilation or cooling mechanisms are necessary to maintain the panel’s efficiency and prevent long-term damage due to excessive heat buildup.

The experiments revealed that the temperature of the solar panel increased with solar radiation, peaking around midday before gradually declining. Among the different substrates tested, iron sheet recorded the highest temperature (79.33 °C), followed by roof tiles (70.34 °C), concrete (58.44 °C), wood (50.51 °C), grass (41.52 °C), and ground soil (40.51 °C). The higher temperatures observed in the iron sheet were due to its high thermal conductivity, low specific heat capacity, and low albedo, which allowed it to absorb and retain more solar radiation. This result aligns with previous findings by Aletba et al.19 and Shamsaei et al.20, who reported similar temperature dynamics in materials with low albedo and high thermal conductivity. Conversely, ground soil exhibited the lowest temperature, attributed to its high albedo, high specific heat capacity, and low thermal conductivity. The soil’s ability to retain moisture through transpiration also contributed to its cooler surface, thereby maintaining a lower temperature. Transpiration is the process by which plants absorb water from the soil through their roots, transport it through their stems, and then release water vapor into the atmosphere through small openings in their leaves called stomata. This process plays a key role in the water cycle and helps to cool the surrounding environment by releasing moisture into the air, which can affect the microclimate, including temperature. Grass also maintained a low temperature due to its poor thermal conductivity and effective cooling through transpiration, which is consistent with the findings of Nabil and Mansour10, who observed similar cooling effects in materials with high moisture retention properties.

The study’s findings, which show significant temperature fluctuations, suggest that the panels are operating at or near their thermal limits during peak sun hours. This means that while the panels can withstand these temperatures for short durations, sustained high temperatures can cause thermal degradation, reducing panel efficiency and lifetime. Methods like proper panel ventilation, using heat-dissipating materials, or integrating passive cooling mechanisms can mitigate the effects of high temperatures and improve long-term performance.

The power output of the solar panels decreased as the temperature increased, reaching its lowest point around midday before rising again. The iron sheet showed the lowest power output, correlating with its high surface temperature due to its high thermal conductivity and low specific heat capacity. These factors led to increased cell temperatures and subsequently lower power output. This observation aligns with studies by Ogbulezie et al.5 and Sreewirote et al.32, who also reported reduced power output in high-temperature conditions on materials with similar thermal properties. In contrast, ground soil exhibited the highest power output, attributed to its low thermal conductivity, high specific heat capacity, and effective cooling through transpiration, which kept the panel temperature lower. Grass also demonstrated high power output for similar reasons, low surface temperature due to transpiration and high albedo. The relatively uniform temperature and power output for grass and ground soil throughout the experiment are consistent with Alshawaf et al.15 findings, where materials with similar properties showed stable power output. Concrete, on the other hand, had a lower power output due to its high density, which contributed to higher surface temperatures and thus reduced efficiency. Roof tiles exhibited a moderate power output, reflecting their moderate thermal properties, while wood, with its low thermal conductivity and high albedo, resulted in a higher power output due to lower cell temperatures.

The efficiency of the solar panels decreased as the temperature increased, reaching a minimum at midday and then gradually improving as temperatures declined. Grass and ground soil provided the highest efficiency, which remained nearly constant throughout the day due to their low and stable temperatures resulting from effective cooling via transpiration. This consistent efficiency is in line with findings by Kumari et al.2 and Sharaf et al.12, who observed improved performance and efficiency of solar panels on substrates with similar cooling properties. In contrast, materials like iron sheets, roof tiles, and concrete showed lower efficiency due to their higher temperatures, which negatively impacted the performance of the solar panels. The results suggest that substrates with lower thermal conductivity, higher specific heat capacity, and effective cooling mechanisms, such as transpiration in grass and ground soil, are more conducive to maintaining high solar panel efficiency.

The cumulative energy output and irradiation data provided a comprehensive view of the actual energy production throughout the day. Substrates like concrete and roof tiles exhibited relatively stable output, but the cumulative energy yields were not as high as expected given the panel’s earlier efficiency. This highlights the significant role of temperature fluctuations and their effect on long-term energy generation. Grass and soil showed more variability in energy output, but in terms of energy conservation and thermal stability, they performed better over longer periods, especially during the late afternoon when the artificial surfaces experienced significant temperature drops and performance decline. The irradiation levels were fairly consistent across substrates in this study, similar to the findings of Mustafa et al.28, who argued that solar radiation is more significantly influenced by factors such as geographical location, season, and time of day than the substrate itself. However, it was noted that substrate reflectivity (albedo) could slightly alter the amount of radiation absorbed by the panel, with high-albedo materials reflecting more sunlight, which could result in less energy absorption by the panel, leading to a decline in performance.

Limitations of the study

While this study provides valuable insights into the effects of different substrates on the efficiency of monocrystalline solar panels, there are several limitations.

  1. 1.

    Limited Number of Substrates: The study examined only a specific set of substrates (iron sheet, roof tiles, concrete, wood, grass, and ground soil). Other materials, including various types of green roofs, synthetic substrates, or innovative cooling technologies, were not included. This limits the generalizability of the findings to a broader range of materials.

  2. 2.

    Geographical and Climatic Constraints: The study’s findings are based on experimental conditions that may not fully account for regional variations in solar radiation, temperature, humidity, and other climatic factors. Results may differ in locations with different weather patterns or in regions with extreme temperatures.

  3. 3.

    Scale of the Experiment: The experiments were conducted on a small scale, which may not fully represent real-world conditions. Larger-scale installations or long-term studies might yield different results due to factors such as variations in panel orientation, shading, and environmental conditions.

  4. 4.

    Temporal Limitations: The observations were taken at specific times of the day. Seasonal variations or long-term effects were not considered. Temperature responses and efficiency could vary with different seasons or under varying sunlight intensities over an extended period.

  5. 5.

    Assumption of Uniform Material Properties: The study assumes that the substrates’ thermal properties are uniform across their surface. In reality, material properties can vary due to factors such as wear, ageing, or heterogeneous composition, which could influence the results.

  6. 6.

    Lack of moisture content measurement in natural substrates like grass and soil: Moisture content plays a crucial role in the thermal regulation of these surfaces and could influence panel performance. Future research should integrate moisture analysis to quantify its effects and further elucidate the relationship between substrate properties and solar panel efficiency.

  7. 7.

    Lack of Consideration for Additional Factors: The study focused primarily on thermal properties and their direct impact on solar panel performance. Other factors, such as substrate maintenance, cost, environmental impact, and aesthetic considerations, were not addressed but could influence the practical applicability of the findings.

Conclusion

This study has provided valuable insights into the impact of different substrates, iron sheets, roof tiles, concrete, wood, grass, and ground soil, on the thermal and electrical performance of monocrystalline solar panels. The following are the concluding statements based on the findings of the study:

  • Natural substrates like grass and ground soil were found to maintain lower panel temperatures, improving the efficiency and longevity of monocrystalline solar panels compared to artificial substrates like iron sheets and roof tiles.

  • The study confirms that lower panel temperatures are critical for enhancing performance. Transpiration in natural substrates plays a significant role in heat dissipation, keeping panels cooler and improving efficiency during peak sunlight hours.

  • The findings suggest that natural substrates may offer long-term benefits for solar panel installations.