The ubiquitous accumulation of ash and the mud belt at the edge of solar panels have made the owners of industrial and commercial roof photovoltaic power plants almost crazy. It is a high-yield investment, but we can’t see the expected power generation! Obviously, it’s sunshade cooling. The temperature of the solar panel is even hotter than the roof under the scorching sun.

What happened?

Solar power generation, sunlight irradiation is very important. Solar panels without light not only can not generate electricity but also have the largest power consumption, which is the “resistance” in photovoltaic arrays.

Under normal circumstances, when the sun shines on the surface of solar cells, solar cells begin to have a strange “photovoltaic”. However, due to various reasons, there may always be some places on the surface of solar cells that do not have sunlight, or the sunlight is relatively weak.

At this time, the power generation capacity of this non-irradiated or low irradiated area will be weakened or even zero. However, all solar cells in a solar panel are connected in series. The current normally generated by the whole solar cell or the whole solar panel in other places must pass through the place with weak power generation capacity. This solar cell is like a tightened gate, which limits the normal current, becomes the resistance of the whole circuit, and is also hot and hot.

When a solar cell or an area of a solar panel cannot generate electricity normally, the current of the whole solar panel will be affected.

When the affected solar panel is connected in series with other solar panels, it becomes the resistance of the whole series array and affects the current of an array.

There are many factors affecting the normal power generation of solar cells, among which shielding is the biggest reason. There are many reasons for occlusion, such as leaves, bird droppings, shadows, and ash accumulation.

For solar panels with low installation inclination, the mud belt formed by ponding and ash deposition is the largest source of shielding, and it is also the most common and worst situation in the impact of ash deposition.

1. Formation of mud belt

The so-called low inclination means that the installation angle of the solar panel is close to the horizontal. Generally, solar panels installed below 15 degrees can be considered as typical low inclination installation.

For low inclination solar panels, the most common problem is that the rainwater on the surface of solar panels can not flow out smoothly.

Since most solar panels have aluminum frames, the aluminum frames are usually about 1.8mm higher than the front glass of the solar panel. When it rains or cleaning operation and maintenance, water will flow from the high to the low of the solar panel and flow out of the solar module over the aluminum frame at the bottom.

However, due to the height difference of 1.8mm between the aluminum frame and glass, some mud water will remain at the frame and cannot flow out.

For solar panels with an inclination of fewer than 15 degrees, the stagnant water in this part will cover about 5mm from the inner edge of the aluminum frame to the surface of the solar panel. If considering the surface tension of the stagnant water on the surface of the aluminum frame, the coverage distance is about 8mm.

As there is often ash on the surface of solar modules, the ash will be washed by rainwater to form muddy water. Some muddy water will flow out of solar modules, and some muddy water will be blocked by aluminum frames and accumulate at the edge of solar modules.

When the rainwater is dried, the ash in the water turns into mud, which is paved on the inner side of the aluminum frame at the edge of the solar module and covered on the glass surface inside the frame, and the covering distance is the same as the above ponding.

The problem is that according to the design of the existing solar panels, the gap between the lowest row of solar cells and the edge of the aluminum frame is about 6mm.

In other words, for all solar panels installed with an inclination of fewer than 15 degrees, the mud belt formed after the accumulation of mud will block the front of the solar cell!

For the installation with an inclination of 5-10 degrees, the mud belt can cover more than half of the solar cell area! Over time, the shielding becomes more and more serious!

2. Hazards of mud belt

There are many hazards of mud belts, and the most direct and significant impact is to greatly reduce the output of power generation.

First of all, the power generation capacity of the area sheltered by the mud belt must be greatly reduced, or even no power generation at all.

Secondly, the deterioration of power generation capacity in the mud belt area directly affects the current flow of the whole solar panel and other solar cells, which becomes the resistance of the solar panel and begins to heat up.

Moreover, due to the design of solar panels, 10 solar cells are connected in a string from top to bottom along the long side, and the lowest one of the 10 solar cells is shielded by the mud belt; A solar panel has six strings of solar cells, and the bottom of each string of solar cells is blocked.

Therefore, the six solar cells shielded by the mud belt affect the current of the six strings of solar modules. It usually leads to a loss of 5% to 20% of power generation!