I’m pleased to share relevant solar content with you, my passion and profession here at OneRoof Energy. This is the third of a three-part series covering how different aspects of weather, such as snow and clouds, impact solar PV system performance. Today we’ll discuss the impacts of temperature and wind on system performance – Chris K.
When you think of solar energy you probably are thinking about how sunlight hits a solar PV system and converts that sunlight to electricity. That’s primarily how a system works, but there are other things that influence how well the system is performing.
Take temperature and wind. They can influence system performance when they fluctuate from one “extreme” to the other and change how the system functions.
Solar PV systems at their basic component are electrical circuits. So a solar PV system is subject to the same laws of physics as any other electrical circuit. The system’s current flows as sunlight hits the solar panels. However, the behavior of the electrical circuit in terms of voltage, resistance and current are governed by other effects, like local air temperature and wind speed.
Local air temperature means the temperature of the air directly around the panels of the system. That can change how the solar PV system’s voltage will function. Since solar cells – the physical material within a solar panel that converts sunlight into electricity – are under glass, they are well insulated. As a result, they have higher temperatures than the environment immediately around the panel. In most cases, solar cells operate at a temperature about 25 degrees Celsius warmer than the ambient air. Temperature and voltage have an inverse relationship meaning the higher the temperature, the lower the operating voltage. Lower operating voltages cause lower module (and overall) system efficiency. Translation: your solar PV system won’t operate as well at higher temperatures.
Here is a good general rule:
Between 80 degrees Celsius and 90 degrees Celsius: a module loses 0.5percent efficiency per degree Celsius rise in temperature1.
At OneRoof Energy, we take into account changes in air temperature when we develop our system performance models. We do that by looking at historical weather conditions that include average, maximum and minimum air temperatures for the area. ORE models include these values when predicting the system performance, allowing us the ability to adjust the expected output of a system based on air temperature.
Besides temperature, wind speed also affects your PV system performance. It does this two ways: electrical – by affecting the temperature (and voltage) and mechanically – by impacting the physical system on your rooftop.
Since wind speed influences air temperature, it is a piggy-back factor of how temperature can affect a solar PV system. In other words, at higher wind speeds, the air temperature could decrease and so does the solar cell operating temperature. That means that wind can help a solar PV system perform more efficiently To harvest the positive influence of wind on solar cell operation temperature, ORE will install systems at heights elevated above the surface of the roof (at approximately 3-6 inches above it). This allows for wind to flow between the surface of the solar panels and the roof, reducing the operating temperature of the solar cells. This helps us ensure maximum module and solar PV system efficiency for your system.
Wind speed, including wind gusts, can have physical impacts on solar PV systems. For example, if a solar PV system was not installed with the correct mounting equipment (e.g. rails, attachments, fasteners, etc.) and there are high wind gusts, then the system could be damaged. If the damage is significant, the electrical operation of the system could be affected. In a worst-case scenario, the solar panels could be dislodged from the mounting equipment or the roof due to high winds. The system would lose electrical contact, and be inoperable.
To ensure that PV systems are mechanically secure, ORE uses historical weather models to account for the different wind speeds at a particular location. We use a configurator tool that provides recommended mounting equipment that can sustain the maximum wind speeds and help prevent physical damage to the system. We check the quality of the installation throughout the process to make certain the correct equipment and installation practices are used.
I hope you enjoyed this three-part weather series and I look forward to posting future blogs on solar energy!
1. Solar Energy International, “Photovoltaics: Design & Installation Manual”, New Society Publishers, Copyright 2006.
