Does solar power generation work on rainy days? Tips to prevent a decrease in power generation!

For those considering the introduction of solar power generation, you may be concerned about the amount of electricity generated on rainy days.

Especially in Japan, where we have the “tsuyu” (rainy season), it’s natural to wonder if electricity can still be generated even when it rains. In this article, we will explain the relationship between solar power generation and rain in detail. We will also share tips to prevent a decrease in electricity generation during bad weather, so if you’re interested, please check it out.

Does solar power generation work on rainy days?

As the name suggests, solar power generation is a method of generating electricity by collecting sunlight. So, what happens to electricity generation on rainy days? Here, we will explain whether solar power generation can still produce electricity on rainy days.

It doesn’t stop generating completely

While the amount of electricity generated on rainy days is lower compared to sunny days, it does not mean that generation stops completely.

This is because scattered light still reaches the ground even when it rains. This scattered light reaches the solar panels, allowing them to generate electricity, although not as much as on sunny days, so the output does not drop to zero.

What is the difference in electricity generation between sunny and rainy days?

As mentioned above, solar power generation does occur on rainy days. However, the amount generated is significantly lower compared to sunny days.

The reason is that rain clouds block sunlight, casting shadows on the solar panels. This reduces the amount of sunlight reaching the panels, resulting in lower electricity generation.

On rainy days, you can expect to generate about one-third to one-tenth of the electricity produced on sunny days. However, this can vary depending on the amount of cloud cover, sunlight intensity, and the performance of the panels, so please consider this as a rough estimate.

Other factors that influence electricity generation

Factors affecting the efficiency of solar panels are not limited to rain. Below are some representative factors, aside from rain, that can influence electricity generation.

Clouds and snow

Not only on rainy days, but also on cloudy or snowy days, electricity generation decreases. If the clouds are thick and very little sunlight reaches the panels, the generation will drop significantly.

In the case of snow, there are two scenarios. If snow accumulates on the panels, it becomes difficult for sunlight to reach them, making generation challenging. However, if it is sunny, the snow on the ground can reflect sunlight, potentially increasing generation efficiency.

Temperature

When thinking about solar power generation, many might assume that “it generates more electricity on hot sunny days.” However, solar panels actually have a characteristic of being “sensitive to high temperatures.”

If the temperature is too high, the panels themselves can become hot, which may lower the voltage and reduce generation efficiency.

This means that even on sunny days, if the temperature rises too high, the efficiency of electricity generation may decrease.

Conversely, in low-temperature environments like winter, the efficiency of the panels can improve, allowing for stable generation as long as there is sufficient sunlight.

Sunlight hours

Naturally, the longer the sunlight hours, the higher the efficiency of the solar panels.

You might think, “Sunlight hours are the same everywhere in Japan,” but this is not the case. Sunlight hours can vary by location. For example, there can be a difference of several hundred hours annually between the Kanto region and the Hokuriku region on the Sea of Japan.

Condition of the solar panels

If dust, bird droppings, or fallen leaves accumulate on the surface of the panels, sunlight is blocked, significantly reducing electricity generation.

Even high-performance panels can see a drastic drop in efficiency if the surface is dirty, so regular maintenance is necessary. Be especially cautious during dry periods or in arid regions, as dirt tends to accumulate more easily.

Malfunctions and deterioration

When the power generation decreases, many people focus on factors like the weather or dirt on the panels. Of course, it is quite possible that these are the reasons for the drop in power generation, but equipment failure or deterioration can also be the cause.

If deterioration or failure is the cause, even if the weather improves or the dirt on the panels is removed, the power generation will not increase, so repairs must be carried out promptly. This is especially true if some time has passed since the installation of solar power systems or if maintenance has been minimal, as failures and deterioration are more likely to occur.

Appearance of Hot Spots

When parts of a solar panel do not receive sunlight for an extended period, a phenomenon known as a hot spot occurs.

This refers to the phenomenon where areas that have not been exposed to sunlight for a while heat up, and if left unattended, it can lead to failure. Therefore, after it rains or on windy days, check to see if leaves or debris are stuck to the panels.

In recent years, panels that are less prone to hot spots have been developed, but they do not guarantee that hot spots will never occur, so regular checks are recommended.

What Benefits Does Rain Bring?

Many people might think that rain is a disadvantage for solar power generation.

Indeed, when it rains, the power generation decreases, which is a negative aspect. However, there are also positive effects of rain. One of them is the “self-cleaning effect.” Rain can wash away dirt and debris accumulated on the surface of solar panels, potentially increasing power generation efficiency.

Tips to Prevent Power Generation Decrease on Rainy Days

While rain is not necessarily a negative for solar power generation, it still leads to a decrease in power generation.

So, what can be done to minimize the drop in power generation on rainy days? Here are some representative measures.

Choose Panels with High Power Generation Efficiency

If you want to avoid a drop in power generation on rainy days, it is recommended to choose panels with high power generation efficiency.

There are various types of solar panels, but among them, panels made with monocrystalline silicon are said to generate power efficiently even on days with weak light.

Recently, panels that are “strong in rainy or cloudy weather” or “compatible with low-light power generation” have also appeared, and by choosing such panels, you can expect an increase in annual power generation.

Conduct Regular Maintenance

Even though rain can wash the panels, it does not completely prevent or remove dirt. When the panels get dirty, power generation efficiency decreases, so it is advisable to regularly hire a professional service for inspections and cleaning.

Especially in large solar systems or areas with surrounding trees, debris and leaves can accumulate more than expected, so regular maintenance is essential.

Consider the Installation Orientation of the Panels

The amount of sunlight received by solar panels varies depending on the installation angle and orientation.

In Japan, it is generally considered optimal to face south at an angle of 20 to 30 degrees, but this may not apply depending on the shape of the building or roof.

Additionally, in a string (series connection) configuration, if some panels are shaded, there is a risk that the overall power generation will decrease, so be cautious.

Methods to Cover Power Generation Decrease on Rainy Days

No matter how much effort is made, there are limits to power generation on rainy days. This is where batteries come into focus.

By utilizing batteries, surplus electricity generated on sunny days can be stored for use during rainy weather or at night. This not only reduces the amount of electricity purchased from power companies but also serves as a backup power source during disasters.

While there are additional costs associated with introducing batteries, in the long run, it can be beneficial, so please consider it.

If you are considering installing solar panels, please consult Kakeru Koumuten Co., Ltd.

Our company handles a wide range of exterior renovations, from roofing work to exterior wall work, including the installation of solar panels. We receive requests from many customers, including renovation companies and real estate agencies, who have contacted us!

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We are also happy to assist with small jobs such as partial repairs and rain gutter cleaning!

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Summary

There is a common misconception that solar power generation is “completely unusable on rainy days,” but thanks to scattered light, it is possible to generate a small amount of power. However, the amount of power generated significantly decreases, so prior preparation and design considerations are necessary.

Additionally, the amount of power generated on rainy days can vary depending on the skills of the contractor you hire, so be sure to carefully search for the right contractor.

If you are looking for a solar power installation contractor in Kanagawa Prefecture or the Tokyo area, please feel free to consult with “Kakeru Koumuten.”

Free estimates and consultations are also very welcome, so please feel free to contact us!

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For roofing, guttering, and exterior work and repairs in Kanagawa, contact Kakerukoumuten Co., Ltd..

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