The optimal temperature for solar panels is typically around 25°C (77°F), which is the standard test condition (STC) temperature. However, solar panels can operate efficiently at a range of temperatures.
When temperatures rise above 25°C, the efficiency of solar panels generally decreases. This is due to the fact that higher temperatures can increase the resistance in the solar cells, leading to a reduction in their output voltage. For every degree Celsius above 25°C, a solar panel’s efficiency typically drops by about 0.3% to 0.5%, depending on the specific panel.
How Does Temperature Affect Solar Panel Efficiency?
Have you ever felt a little sluggish on a hot summer day? Well, solar panels can feel that way too, sometimes.
Although you might think that your solar power potential will only increase with every degree that temperatures rise because more sun equals more power, heat is not necessarily a solar panel’s best friend. Like many electronics (computers, phones, etc.), high temperatures can cause solar panel efficiency to drop.
When exposed to too high temperatures, the flow of electricity generating particles within each solar cell is slowed, reducing the speed at which new solar power can be produced. On the other side of the thermometer, temperatures below a solar panel’s peak operating efficiency rating can also reduce your potential electricity production.
Knowing this, if given a choice between hot summer heat or chilly winter conditions, assuming the same amount of sunlight, most solar panels prefer colder climates, producing more electricity per hour in cool weather.
As the temperature of a solar panel increases, the energy output is reduced, and thus overall power generation is negatively affected.
Why? This occurs because solar panels work by utilizing photons to ‘excite’ electrons within the semiconductor. If a solar panel is already warm, electrons within the semiconductor have, for the most part, already been excited. Thus, the overall voltage that the solar panel can generate is lowered. Moreover, the silicon that is commonly found in solar panels speeds up this process of heat building in solar panels on hot days, which doesn’t help.
As heat reduces the overall energy output of solar PV modules – it could be helpful to know just how much performance is being lost. Thankfully, this measurement can be determined through the solar panel’s temperature coefficient.
Best Temperature for Solar Panels in Celsius
The output of most solar panels is measured under Standard Test Conditions (STC). This states that a temperature of 25 degrees Celsius or 77 degrees Fahrenheit. As per the manufacturing standards, 25 °C or 77 °F temperature indicates the peak of the optimum temperature range of photovoltaic solar panels. Solar Panel efficiency is inversely proportional to the temperature of the weather. It is observed that the efficiency of a solar panel decreases by 10-25% with an increase in the temperature of the climate. The output of the voltage decreases with the increase in the temperature of a solar panel.
Each solar panel has its own heat tolerance value, which is popularly called temperature coefficient (Pmax.). This coefficient of Pmax value reflects how much your panel efficiency will drop with an increase in 1°C above 25°C (Standard Test Condition STC).
4 Tips for Maximizing Solar Panel Efficiency
- Analyze the roof before installing solar panels : The prime factor that needs to be considered at the time of installation of the solar panel is to check the condition of your roof. Inspect the structure of the roof by a construction professional for extra security. They can determine whether your roof has the right roof covering or if it needs to be replaced before the installation. They can also check whether your roof is suitable for mounting solar panels or not.
- Choose the right roof covering : Every roof covering which is available in the market might not be suitable for solar panels, but if you choose a bitumen roof membrane, you can’t go wrong. The bitumen-based roof membrane ensures additional security, and it has a very long service life. Flagon TPO is also highly suitable as a roof covering for solar panels. If opted for, you can count on a service life of 25 to 30 years because a roof covering can outweigh the life expectancy of solar panels.
- Take the orientation of your solar panels into account :Naturally, most of the sunlight will be absorbed by the system if the system is faced towards the south. Nonetheless, solar panels are still worthwhile if your roof has a different orientation. Solar panels facing 30° to the west or east still work effectively. Choose a western rather than eastern orientation for your solar panels.
- Ensure optimal performance: If you are planning to install solar panels, 30° to 35° is the optimal roof pitch. As per the predetermined principle, you can use all roof pitches between 15 and 50°, but they won’t be as efficient. As per the experts, the roof pitch will determine how the solar panels are attached.
The Relationship between Temperature, Humidity, and Solar Panel Efficiency
Temperature, humidity, and solar panel efficiency are interconnected factors that impact the overall performance of a photovoltaic system. In general, research has found that higher temperatures reduce electrical efficiency. Humidity also plays a part, with lower humidity levels leading to increased output and efficiency.
Solar Panels Generally Perform Better at Lower Temperatures
As the temperature of a PV panel increases above 25°C (77°F), its efficiency tends to decrease due to the temperature coefficient. The coefficient measures how much the output power decreases for every degree Celsius above a reference temperature (usually 25°C).
Higher temperatures cause the semiconductor materials in photovoltaic cells to become more conductive. It increases the flow of charge carriers and consequently reduces the voltage generated.
Some PV panels feature heat dissipation mechanisms to reverse the adverse effects of high temperatures. Passive cooling or enhanced ventilation are proven methods to get photovoltaic panels closer to optimal operating temperatures.
Humidity Can Have Both Positive and Negative Effects on Solar Panel Efficiency
On the one hand, high humidity levels can result in increased cloud cover and atmospheric water vapor. The clouds of humid air can scatter the sunlight or absorb it, reducing the amount of solar irradiance reaching the PV panels. Excessive humidity can also lead to the accumulation of dirt and dust on the panel surface, causing a decrease in efficiency due to reduced light absorption.
On the other hand, humidity can also keep photovoltaic panels cooler by promoting heat transfer through evaporation and condensation, potentially mitigating some of the adverse effects of high temperatures on efficiency.
How to Counteract Solar Panels Overheating
Regardless of which panels you decide to use, there will always be some energy output loss due to heat. However, there are several ways to mitigate the effects of hot temperatures on solar panels. A basic technology employed by most panel manufacturers is to use a thermally conductive substrate to house their panels, which helps vent heat away from the glass layers of the module. Solar panels are also commonly mounted a few inches above your roof, with airflow space below the actual unit, helping to move heat away from the modules.
Thin film panels are a recent market innovation with a temperature coefficient rating between -0.20 and -0.25. These panels have a distinct coefficient rating advantage over more traditional monocrystalline and polycrystalline photovoltaic panels, which have a temperature coefficient typically between -0.26 and -0.50.
However, they come with a tradeoff thin film panels generally are less efficient than their crystalline PV counterparts.
Conversely, if you live in a warm and sunny climate throughout the year, you may want to invest in higher-end solar panels that come with a lower temperature coefficient. Sunpower, Panasonic and REC manufacture solar panels with some of the lowest temperature coefficients available in the industry. If you expect that the surface temperature of your roof will climb above 25 °C for a significant portion of the year, consider getting quotes from solar installers who offer these higher-end panels.
Conclusion
The optimal temperature range for solar panels is typically between 15°C and 35°C (59°F to 95°F). However, as temperatures rise above this range, the efficiency of solar panels decreases due to the increased resistance in the photovoltaic cells.
To maintain optimal performance, it's essential to consider various cooling strategies and installation methods, such as ensuring adequate airflow, using light-colored mounting surfaces, and investing in high-quality panels with lower temperature coefficients. By doing so, you can mitigate the impact of high temperatures and maximize the energy output from your solar power system, ensuring a more consistent and reliable source of renewable energy.