Cloudy, rainy, humid, and dewy weather has an adverse impact on the performances of solar panels. Cleaning of the panels, optimization of the tilt angles, and selection of solar panel systems which can provide waterproof and moisture-resistant properties are the various ways to counter this effect.
Cloud Cover
Among such influencing factors in humid weather for the efficiency of solar panels is cloud cover. The intensity of the light reaching the ground would be directly pre-set according to the thickness and type of clouds. The thick cumulonimbus clouds cut down drastically the direct sunlight, tumbling the solar panel power output. Furthermore, on a fully overcast condition, the energy output from the panels is about 20% of what it would have been if the weather was sunny. Geographic location also plays a very important factor in this. In regions near the equator, though cloudiness is very high, sunlight remains strong, and the scattering effect of clouds allows the solar system to keep working. In more northern latitude areas, especially during winter, both cloud cover and shorter daylight hours further decrease power generation.
While it may be true that cloud cover actually reduces the amount of direct sunlight on the panels, there is just no dismissing the capability of clouds to scatter light. Sometimes, scattered light enhances the uniformity of light distribution. Although such light has lower energy, some solar panels—especially thin-film solar panels—are sensitive at low light and hence offer some levels of efficiency under such scattered lights. The panels are mounted so that their angle is adjusted for catching more scattered light, and more efficient photovoltaic conversion technology is used to maximize the power output under conditions of cloudy weather.
Besides that, cloud cover is usually dynamic and can even allow short breaks of sunshine, colloquially known as "sun breaks." These short spurts of high irradiance may momentarily raise the efficiencies of panels. Thus, in designs meant for locations with frequent humid weather, considerations must extend beyond just the average ambient light level to taking fullest advantage of transient upsurges in sunlight flexibility to increase total energy generation.
Rainy Days
Rainy weather is not just that it reduces the efficiency of solar panels by blocking sunlight with cloud cover; rain directly influences the performance of the solar panels. During rainfall, water droplets may stick to the panel surface and reduce the light penetration. In the case of heavy rain, droplets of water block sunlight or even completely cover the surface of the panels, bringing the power output close to zero. The instantaneous power generation of the solar system under these conditions will plunge.
There is, however, another positive side to rain. Solar panels exposed to air for a long period are likely to accumulate dust, pollen, and other air pollutants. These prevent sunlight from entering the panel and reduce efficiency. Rain, especially heavy rain, may clean the panel surface, washing off accumulated dust to restore the transparency of the panel. Indeed, some field studies have shown that panel efficiency does have a tendency to rise temporarily following rain, quite directly related to the cleaning effect of the rain. This could turn out to be important for those panels installed in highly dusty or highly polluting regions due to the reduction in frequency for manual cleaning and attendant costs.
The frequent raining seasons lead to equipment aging and the processes of rust, which are related to staying in humid conditions of metal connectors and supports. In the design of a system, it is relevant to apply corrosion-resistant materials and encapsulation techniques of high quality in order to reduce the long-term negative impact of rain on the system. Besides, for those watery-prone flat installment methods, optimization of the tilt angle is suggested in some areas where the amount of rainfall is heavy to avoid long-time staying water drops on the surface to block the light.
Humidity Levels
Although not widely known, humidity is one of the most prevalent causes of efficiency loss in solar panels. In areas where humidity is experienced, the water content in the air scatters and absorbs light. Consequently, the amount of light reaching the panels is reduced. For instance, the rate of light transmitted could decrease by 1% to 2% with every increase of 10% in the humidity of the air. This is notably evident in tropical regions, and the effect lowers the photovoltaic conversion efficiency of the panels directly.
Humidity is not the only cause that affects light transmission, but it also has many side effects on the materials of the solar panel. High humidity hastens the aging process within the internal parts, especially for low-quality or poorly sealed panels, where moisture may infiltrate the internal circuits, creating short circuits or other electrical failures. In highly humid areas, the encapsulation process for solar panels becomes more difficult. Advanced solar panels tend to use such encapsulation materials as high-quality EVA and PVB, which boast excellent resistance to moisture and are capable of protecting the interior of the panel against moisture effectively.
High humidity generally goes with lower temperatures, and the drop in temperature could even favor certain types of panels. On the contrary, photovoltaic panels have depressed conversion efficiency at high operating temperatures. Consequently, at the relatively low operating temperature conditions under humid weather, a certain type of solar panel can be more efficient, such as panels of monocrystalline silicon type. However, normally the negative effect of humidity on light transmission offsets the efficiency gains from lower temperatures; thus, generally speaking, humid weather is still considered to be one factor that negatively influences the power generation of solar systems.
Dew Formation
Dew can only form under high humidity conditions, especially at night, when a thin water film layer develops on the surface of solar panels. When the air temperature falls below the dew point, the condensed water vapor forms droplets on the panel surface. In such cases, these block light transmission through the panel temporarily, especially during the early morning when the sun first appears. Panel efficiency thus goes low since some areas of the panel will be covered by dew.
Since the action of dew is temporary, it does have a significant impact on the operating condition of solar panels within that particular period. In cases when water droplets cover the panel surface, they behave like small prisms, where refraction and scattering of light occur and prevent effective entry into the panels. This phenomenon is very noticeable early in the morning when the sun is just beginning to intensify, but before dew has evaporated, the efficiencies may remain at lower levels.
Dew formation can be minimized with the design of a proper tilt angle because dew easily slides off or evaporates faster in panels sited under tilt than on horizontal ones, which minimizes its stay on the panel surface. More recently, hydrophobic coatings of panel glass have been found capable of reducing water adhesion on the surface and thus mitigate the shading problem caused by dew. Optimized design and technical measures mitigate the effects of dew on the solar panels; thus, the latter will bounce back to their normal efficiency much faster in the morning.
Panel Cleaning
Panel cleaning becomes a serious affair in the humid weather period. While it is true that rainwater may partly clean the panel surface, cleaning becomes more difficult for panels in high humidity and frequent rainfall environments. The humid environment provides favorable conditions for mold, algae, and moss to grow. These biological contaminants are capable of sticking to the panel surface, reducing its transmission rate of light and hence the efficiency of power generation.
Over time, the biological films that settle on the panel surface increasingly block out light into the panels, particularly around shaded or moist corners. Even though natural rainfall does a good job of washing off light dust and dirt, it does not clean off these stubborn biological contaminants. As such, cleaning by hand is quite necessary, especially in places with highly humid climatic conditions. At least two complete cleanings in a year are very much recommended to ensure panels have high light transmission.
In such cleaning of panels, the use of non-corrosive cleaners with soft brushes is advisable to prevent damage to the panel surface protection layer. Some new materials for solar panels boast anti-fouling and antibacterial surface coatings, which could effectively minimize mold and algae adhesion, hence reducing cleaning frequency. In highly humid regions, the use of glass surface panels with self-cleaning functions can go a long way in enhancing ease towards the maintenance of the panels, hence reducing the cost of manual cleaning with system downtimes.
Energy Output
Under such conditions, humid weather produces a highly unqualified effect on the energy output of the solar panel. By nature, the solar radiation is hugely reduced when received through a synergistic effect of clouds, rain, and high humidity that contributes to an abrupt decrease in power generation capability. Field data from various regions indicate that continuous rainy days may reduce solar system power output by over 60%, hence an unprecedented stress on energy supply, particularly in regions or households highly dependent on solar energy.
Designing a solar system should, therefore, put into consideration the type of panels, the angle of installation, and how the storage will be configured to minimal humid weather effect on energy output. Energy Storage Systems can store surplus power generated in sunny days for use during cloudy or rainy days hence ensuring a steady power supply. Moreover, some modern photovoltaic technologies work rather well in low light conditions, and picking such panel types can considerably raise the general output of energy in humid weather conditions.
System maintenance and monitoring will also help to assure energy output. Real-time monitoring of the power generation from solar panels enables timely detection of the impact on the performance of the system due to humid weather and appropriate action. Records of the longtime data help analyze the specific influence of the humid weather and allow adjustment in the settings and operations of the system to optimize the performance of power generation.
Maintenance Tips
In humid weather, it puts special demands on solar panel maintenance, especially under continuous rain and high humidity. The regular maintenance is necessary to guarantee the normal operation of the system and prolong the service life of it. First, regular check cleanliness is the key to the maintenance of panels. Under high humidity, dust and mold are easy to attach to the panel surface and affect the transmission of light. It produces high-efficiency power whose effectiveness can be sustained through cleaning using water and non-corrosive cleansers.
Again, maintenance pertains to the connectors and brackets. In humid weather, metal supports and connectors corrode and rust. The problem is more serious in solar systems mounted in coastal areas since a combination of salt and moisture quickens the deterioration in the metal portions. This naturally means that supports should be made from corrosion-resistant materials and checked periodically for stability, in order to ensure the stability and safety of the system in bad weather conditions.