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Not only reduce the power generation! Discussion of the impact of shadow occlusion on photovoltaic power generation

View: 5682021/09/04  

According to calculations, the slight shade of trees and wires in the photovoltaic system can cause the power generation of the power station to be reduced by about 20-30%!

At present, the construction of photovoltaic power plants on the roofs of rural households and industrial and commercial buildings has become a popular trend. The amount of photovoltaic power generation directly affects the final profit, and shadow shading is one of the most common problems affecting power generation.

PV shadow shading should not be underestimated

So, how big is the impact of shadow occlusion on power generation? In many rooftop photovoltaic power stations, many owners often cannot completely avoid shadows for the one-time installation of photovoltaic power plants, because owners feel that the area covered by shadows is not anyway. Large, the impact should not be great, but in fact, people often overlook the power of small-scale shadows. According to calculations, the slight shade of trees and wires in the photovoltaic system can cause the power generation of the power station to be reduced by about 20-30%! Under certain conditions, some of the cells in the photovoltaic system will be blocked by other surrounding objects, causing local shadows, which will cause some batteries to heat up, resulting in the so-called "hot spot" phenomenon. If the shadow effect is not eliminated and persists for a long time, when the hot spot effect reaches a certain level, the solder joints on the module will melt and destroy the grid line, which will lead to the scrap of the entire solar cell module. Obviously, the shading seriously affects the service life of the junction box and the battery panel, and at the same time seriously affects the power generation and reduces the owner's income.

A relatively common photovoltaic shadow shading source

1. Wires, guardrails

Although the construction scope of photovoltaic power stations is fixed, the surrounding environment of the power station is diverse. Even a very professional system design company will ignore the invisible shielding of wires and power station guardrails.

2. Fixed buildings

There are two types of buildings here: first, the existing building shelter before the construction of the power station; second, the building shelter built the day after tomorrow.

3. Plants near the photovoltaic power station

When the photovoltaic power station was built, there were no plants nearby, but later, new plants will grow, and these plants will play a role in sheltering the power station.

4.Bird droppings and dust

Photovoltaic modules are often built on the roof and the ground. For photovoltaic power stations placed outdoors, it is easier to attract dust. When the modules are covered with a layer of dust, don’t underestimate this layer of dust. It will also affect the power generation of photovoltaic modules. It is very large, and photovoltaic modules will also become a place for birds to "play". Bird feces and scattered bird feathers become frequent visitors on photovoltaic modules.

5. Sun-dried peppers, sun-dried sweet potatoes, etc.

Previously, some people posted on the Internet that a user was drying hot peppers and sweet potatoes on photovoltaic modules, which has become a hot topic in the industry. Although this "funny act" has facilitated the lives of ordinary people, it has brought serious harm to photovoltaic power plants.

How to avoid photovoltaic shadow occlusion

1. Pay attention to shadow analysis before power station construction

Before the construction of the photovoltaic power station, it is necessary to do the preliminary survey work to determine whether the surrounding high-voltage lines, railings, vegetation, and existing buildings (planned buildings should also be anticipated) will be blocked. Find a way to eliminate the blocking and change the installation location. . It is necessary to fully consider the growth year of the plant in the survey and installation, and consider whether the shade and branches and leaves cause shelter. If there is shelter, it can be felled. In addition, the difference in topography should take into account whether the component north-south and east-west components cause shadow occlusion; different sub-array heights of the same row of square arrays cause occlusion; at the same time, the shadows between floors should also be considered.

2. Do a good job of cleaning the surface of photovoltaic modules

The shadow occlusion is mainly due to the influence of bird droppings, dust, shade, etc., so first of all, we can choose a suitable location to install the photovoltaic module, and try not to install the module in the shaded place. If it is unavoidable, choose a suitable one. The placement of components can reduce the impact of shadows caused by occlusion. In daily operation and maintenance, pay attention to the cleaning of photovoltaic modules, and timely clean up dust and other foreign objects.

3. Avoid man-made occlusion

Some people always think about what they can do for the power station, such as installing fences and setting up bird repellent poles in order to drive away the birds. This is a kind and positive action, but there is a counter-effect of "superfluous". Others lack knowledge of how to maintain and operate photovoltaic power station. Wrong practices such as drying clothes and vegetables on photovoltaic modules, these behaviors will invisibly bring shelter to the power station.

4. Choose a multi-channel MPPT inverter

Considering the system itself, the realization of multi-channel MPPT will reduce the influence of shadow occlusion. For example, the micro-inverter photovoltaic system is a fully parallel design circuit, and each module has an independent MPPT, which can achieve the maximum power output, so that shadows, dust, and leaves partially block the battery panels, and no longer have the short board effect. The mismatch problems caused by the different shades, orientations and angles of the components greatly increase the power generation. But based on this type of system, each solar panel is equipped with an inverter, and the cost is also relatively high. It can only be said that based on on-site conditions and basic calculations, if the cost budget allows, using this system can avoid on-site restrictions and bring higher power generation efficiency and benefits, that is a good choice.

It is easy to build a photovoltaic power station, but the shading problem cannot be underestimated. If the photovoltaic power station can achieve the expected benefits, these shading problems must be paid attention to early. Only in this way, can the photovoltaic power station truly become a "money cow" for the user ,instead of  a "vase" in the user's home.

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