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How to clean photovoltaic panels in winter

2020-01-13

The following is an analysis of why the power generation of photovoltaic power stations in winter will decrease from several aspects
First, the winter sunshine time is shortened, and the surface solar radiation is weakened
Taking Shijiazhuang as an example, its latitude and longitude are: 38.03 north latitude and 114.48 east longitude
 
According to the most authoritative NASA website in the United States, we enter the latitude and longitude of Shijiazhuang area, and we can query the following data:
 
The data on the NASA website is at least a 10-year average, and solar radiation is a 22-year average. The last average of 4.28 in the table above can be used as the peak sunshine time in Shijiazhuang. From the above, it can be clearly seen that the sunshine time and surface solar radiation in November, December and January are far below the average.
 
Haze and dust
 
Due to the dry weather, heating, and environmental pollution, the northern winter air is more dusty than other seasons, especially the winter haze weather is relatively increased. Airborne suspended objects will absorb and reflect solar energy, resulting in a significant reduction in the sunlight received on the surface of the module. If the haze weather lasts for a long time, the long-term accumulation of particles may cause a lot of heating of the module, causing a hot spot phenomenon, which may threaten the life of the module or cause a fire in severe cases. as shown in picture 2:
 
Figure 2 A user power station in Wucheng District, Shijiazhuang
 
Solar panels are the core part of a solar power system and the most valuable part of a solar power system. The quality or cost of solar panels will directly determine the quality and cost of the entire system. The theoretical power generation efficiency of solar panels is 25%, and the actual power generation efficiency is 23%. After pollution, the power generation efficiency is reduced to 17-18%. Therefore, the cleanliness of the battery panel has a great impact on power generation efficiency and benefits, and it is impossible to solve the cleaning problem.
 
Solar photovoltaic panel cleaning steps:
 
1. Observe and analyze the photovoltaic panel construction environment, use reasonable photovoltaic panel cleaning equipment and tools, and specify a cleaning plan.
2. Rinse or brush photovoltaic panels to remove surface dirt.
3. Wash the photovoltaic panel with water.
 
Third, snow on photovoltaic panel components
 
Snow covers the modules, and only a small amount of solar energy shines through the snow to the photovoltaic modules, which will affect the photovoltaic power generation.
 
(1) Small suggestions for installing photovoltaic power stations in snowy areas:
 
a, Large-angle installation of photovoltaic panels
 
Install the solar panel at a large angle within the optimal inclination range. This can reduce the snow accumulation speed and avoid the trouble of clearing snow from time to time.
 
b. Keep some distance from the ground during installation
 
When the snow does not slide anymore, it accumulates at the bottom, so that it slowly accumulates to cover the entire assembly.
 
(2) If the photovoltaic power station is maintained after snow:
 
a. It is generally recommended not to wait for the snow to be too thick before cleaning to prevent the components from freezing.
 
b. Do not use hot water to cast photovoltaic panels. Uneven hot and cold will seriously damage the photovoltaic panels.
 
c. You can use soft items to push the snow down. Be careful not to scratch the glass, as this will reduce the amount of light transmission. (Using a tennis ball to bounce gently on a sloping photovoltaic board to make the snow fall would be a good method)
 
d. The module has a certain load-bearing capacity, but it cannot be cleaned by stepping on the module. This will cause the module to crack or damage, and affect the life of the module.
 
e. Snow removal must be clean. Do not underestimate the strip of snow. The blocked part will cause the overall photovoltaic panel to fail, causing a significant reduction in power generation efficiency.
 
Fourth, the reliability of inverters in cold areas
 
As the core component of photovoltaic system, the inverter should be able to work normally in low temperature environment. Therefore, when customers choose the inverter, the reliability guarantee should be an important basis. In a low temperature environment, common faults of the inverter are:
 
1. The inverter cannot be started: In normal operation, the inverter will generate heat due to internal heating, so there is generally no low temperature effect. However, at the beginning of startup, the internal temperature of the inverter is the same as the ambient temperature, and some inverters may not start. .
 
Failed to report the fault and cannot be connected to the grid for power generation: The inverter has a temperature sensor. If the temperature sensor is not selected properly, some temperature sensors will not work at low temperatures, or the measurement error is large, which will cause a false alarm. For the measurement offset that may occur in the measurement IC at low temperature, it is necessary to actively adjust and calibrate the offset to ensure that the inverter is safely connected to the grid in a low temperature environment. It is also necessary to simulate the on-site low temperature, and perform startup operation tests and stress experiments to ensure Inverter reliability.
 
2. Components or parts are damaged: At extremely low temperatures at night, the temperature of the components of the inverter is a test. In order to ensure that the inverter can adapt to various extreme weather environments, the use of reliable quality components will change. Is crucial.
 
Growatt30-50K models use environmental conditions of the main components.
 
Selection of PV input terminals and LCD screens for key components
 
PV terminal and breather valve passed -40 ~ 85 degree high and low temperature impact test, -40 degree low temperature storage test
 
Five, the low temperature performance of components
 
The voltage of a component changes with temperature. The coefficient of this change is called the voltage temperature coefficient. The specific value is about -0.35% / ° C, which means that for every 1 degree Celsius decrease (rise) in temperature, the voltage rises (decreases) by 0.35% of the reference voltage. One of the standard operating conditions of the module is that the temperature changes at 25 ° C, and the voltage of the corresponding component string will change. Therefore, during the design of the power station, the voltage change range must be calculated based on the local minimum / maximum temperature. Open-circuit power stations cannot exceed the maximum voltage limit of the inverter.
Photovoltaic panel assembly cleaning tool
Summary
 
In winter, the amount of electricity generated by photovoltaic power stations is reduced, so it is not necessary to be nervous. This is normal. However, in winter, pay attention to the maintenance and maintenance of the power station, and pay attention to the use of special photovoltaic panel cleaning tools to deal with dust and snow, so as not to wear out when cleaning the photovoltaic panel. When selecting an inverter, use an inverter with a low temperature function. Pay attention to the voltage temperature coefficient when designing the string.