Building photovoltaics on the roof, of course, is to maximize the use of roof resources, and how to completely avoid shadows has become an important issue. Many owners and installers feel that the shadow shielding area is not large, and the impact should be small. In fact, we all underestimate the power of small-scale shadow shielding.
According to calculations, the slight shade of trees and wires in the photovoltaic system can cause the power generation to be reduced by about 20-30%!
What is the hot spot effect?
During long-term use, solar cell modules will inevitably fall on shelters such as bird droppings, dust, and fallen leaves (and may also be sheltered by trees, other buildings, etc.), and these shelters will form shadows on the solar cell modules.
Due to the existence of partial shadows, the current and voltage of some cells in the solar cell module have changed. As a result, the product of the local current and voltage of the solar cell modules increases, thereby generating a local temperature rise in these cell modules. At this time, the shaded part of the series branch will be used as a load to consume the energy generated by other unshaded solar cells, so the shaded part will heat up at this time, which is the hot spot effect.
The more common photovoltaic shadow shading sources
1. Wires, guardrails
Although the construction scope of photovoltaic power plants is fixed, the environment around 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 buildings that already existed before the construction of the power station; second, the buildings 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 would grow, and these plants would shade the power station.
4. Bird droppings and dust
Photovoltaic modules are often built on the roof and on 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, and 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.
How to Avoid PV Shading
1. Pay attention to the shadow analysis before the construction of the power station
Before the construction of the photovoltaic power station, it is necessary to do a preliminary investigation to determine whether the surrounding high-voltage lines, railings, vegetation, and existing buildings (planned buildings should be expected early) will be blocked. Find a way to eliminate the blockage 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, branches and leaves cause occlusion, and if there is occlusion, it can be cut down.
There are also topographical differences that need to be taken into account whether the north-south and east-west components cause shadow occlusion; the same row of square arrays with different sub-array heights cause occlusion; at the same time, the shadows between floors should also be considered.
2. Clean the surface of photovoltaic modules
Shadow occlusion is mainly due to the influence of bird droppings, dust, tree shade, etc. First, we can choose a suitable location to install photovoltaic modules, and try not to install modules in sheltered places. If it is unavoidable, choose a suitable The placement of components can reduce the impact of occlusion caused by shadows. In daily operation and maintenance, pay attention to the cleaning of photovoltaic modules, and promptly remove foreign objects such as dust deposits.
3. Avoid man-made occlusion
Some people always think about what they can do for the power station, such as installing fences and erecting bird repelling poles to drive away birds. This is a kind and positive move, but it has the reactionary effect of "superfluous", and some people lack photovoltaic operation. Dimensional knowledge, wrong practices such as drying clothes and vegetables in photovoltaic modules, these behaviors will invisibly bring shelter to the power station.