In recent years, China in Xinjiang, Qinghai, Inner Mongolia and other provinces (regions) developed and constructed a large number of huge-scale photovoltaic power generation bases, in addition to the western part of Jilin, the Tibetan Plateau, the Sichuan Basin and other regions, but also actively planning to build the corresponding photovoltaic base, many of these bases are located in the desert, the Gobi, or more arid areas.
Some people can not help but ask, in the arid desert and surrounding areas to build photovoltaic power generation base, where the wind and sand are generally larger, the solar panels are easy to fall on the dust, if these dust is not cleaned up in a timely manner, will inevitably seriously reduce the efficiency of the solar panels of power generation, how do we do it?
If there is dust on the surface of PV module, it is easy to cause two main aspects.
1.Blocking sunlight and reducing power generation
By reducing the transmittance of the glass on the surface of the PV module, the amount of solar radiation irradiated to the surface of the battery is reduced.
2.Obstructing the external heat dissipation of PV modules
Easily lead to changes in the form of heat transfer on the surface of the product, the dust absorbs solar radiation and converts it into its own heat energy, hindering the external heat dissipation of the cover glass of the PV module.
Dust is one of the most significant problems affecting the performance ratio of PV power plants, as shown in the following:
- The effect of dust on the amount of solar radiation
Dust not only seriously affects the transmittance of solar radiation on the glass surface, but also causes diffuse reflection of solar radiation. According to experimental measurements, the accumulation of dust on the surface of the glass can lead to a loss of solar radiation amounting to 5%-30%. The main loss is caused by the absorption, reflection and scattering of solar radiation by the dust attached to the glass surface.
- Impact of dust calcification deposition on light transmission
Dust contains a large number of calcium and magnesium oxides, although a small amount of calcium and magnesium ions will be dissolved by the rain, but do not clean up in a timely manner, long-term adhesion to the surface of the PV module will form a certain thickness of dust and hard calcium and magnesium scale, and it is not easy to remove, which will seriously affect the power generation effect of the PV module, to a certain extent, there will be a part of the PV cell slices to produce hot spots and other problems.
- The effect of dust on the temperature of photovoltaic modules
Attached to the tempered glass surface of the dust will make part of the solar radiation is absorbed by the powder and converted to heat, thereby increasing the operating temperature of the photovoltaic module, but also easy to lead to the surface of the photovoltaic module cover insulation effect, affecting the heat dissipation of photovoltaic modules, increase the thermal temperature effect of photovoltaic modules affecting the effect of photovoltaic power generation.
Photovoltaic module is an important power generation component of the photovoltaic power generation system. Photovoltaic module photoelectric conversion efficiency is inversely proportional to the temperature, once the temperature of the photovoltaic module increases, then its conversion efficiency will be reduced, and vice versa the temperature decreases, then the photovoltaic module photovoltaic efficiency will be enhanced.
And the accumulation of dust day and month, through the role of heat transfer will lead to the PV panel internal temperature increases, reducing the PV efficiency.
In a word, if you don't clean up the glass surface dust in time, it will not only increase the temperature rise of PV module, but also affect the power generation performance of PV module, and the thickness of the accumulated dust accumulates to a certain degree, which will cause the sunlight to enter the angle of the greater the path of the sunlight in the layer of accumulated dust is longer, and it is easier to appear the phenomenon of reflection, scattering, and absorption.
For photovoltaic power plant, we should pay special attention to the impact of dust on photovoltaic power generation, which do timely sweeping, keep the surface of the photovoltaic module clean, in order to more efficient operation and maintenance of photovoltaic power plant use.
1.pay attention to photovoltaic power station cleaning time and frequency
Photovoltaic power station is working under light conditions, strong light photovoltaic power station produces high voltage, high current, if this time to clean up, it is easy to cause safety hazards. Generally speaking, the early morning or evening time will be selected for the PV power plant dust removal and other cleaning operations, because these time periods within the power plant's low efficiency, small loss of power generation, and due to the reason of the sun's illumination, you can effectively avoid the component shadow shading.
In addition, for the consideration of power generation efficiency and cleaning costs, dust removal and cleaning of PV power plants can not be too frequent, generally 2-3 times per month. If encountered similar to this dust storm weather, it is necessary to increase the cleaning frequency.
2.Avoid flushing with water directly
As dusty weather occurs in winter and spring, the temperature is low, if water is used for rinsing, it is easy to freeze on the surface of PV modules, which may cause hidden cracks and other injuries. In addition, in the water cleaning process should also avoid water directly wet to the junction box, resulting in the danger of leakage. You can use the form of spraying, but also eliminates the cumbersome manual cleaning.
3. the operator needs to pay attention to safety
Components in the cleaning should be careful not to be components and brackets of the sharp corners of the cuts and bruises. Placed outside the DC cable and components, inverter connected, with the passage of time, the cable may appear bare skin, so in the cleaning of the cable should be checked first, in order to exclude the hidden danger of leakage, and then cleaning. In addition, for PV panels installed on top of sloped roofs, it is more important to pay attention to the risk of people stepping on or sliding down when cleaning.
Cleaning Precautions for Photovoltaic Modules
1.The amount of power generated by a solar module is related to the amount of light falling on it. Modules with shaded cells produce relatively little energy, so it is vital to keep them clean. Dirt such as bird droppings, leaves, dust, etc. usually need to be cleaned.
2.Cleaning the modules should ensure that the difference between the water temperature and the module temperature is between -5℃ and 10℃.
3.PV components with oil and other difficult to clean substances, you can use conventional household glass cleaner; note that you can not use alkaline and strong acidic solvents, including hydrofluoric acid, alkali, acetone and so on.
4.For horizontally mounted modules (0° tilt angle), the cleaning frequency should be increased according to the demand, because these modules will not have the "self-cleaning" function as the modules mounted at 10° tilt angle or larger tilt angle.
5.The rear surface of the module does not normally need to be cleaned, but when cleaning is deemed necessary on the back of a double-sided module or the back of a single-sided module, all sharp objects that could cause damage or penetrate the substrate material should be avoided. Other cleaning requirements are the same as those for the front side.
6.A complete inspection of the assembly for breakage, damage, and loose joints is required prior to cleaning. Broken or damaged components present a shock hazard due to current leakage, which can be exacerbated by moisture in the components.
7.During daylight hours, the voltages and currents present in the array are sufficient to cause fatal electrocution. PV modules should be cleaned under low irradiance conditions.
8.Before cleaning, make sure that the circuit is disconnected, otherwise contact with exposed parts of energized components can lead to injury.
9.Wear suitable protective clothing (clothing, insulated gloves, etc.) when cleaning.
10.It is forbidden to immerse the components partially or completely in water or any kind of washing solution.
11.It is strictly prohibited to clean the PV modules under the meteorological conditions of wind greater than level 4, heavy rain or snow.
12.During the cleaning work of PV modules, it is strictly prohibited to step on the modules, to spray running water onto the back of the modules and the cables, and to ensure the cleanliness and dryness of the connectors to prevent electric shocks and fire hazards.
The natural environment as well as the surrounding environment will lead to the formation of pollution on the surface of the photovoltaic components, resulting in a reduction in the efficiency of the system power generation, the need for occasional local or total cleaning of photovoltaic power generation project components. And regular component personnel to the power station to carry out a full range of detailed inspection, so as to ensure that the power station's power generation, to create more economic benefits.
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