Evaluation of Snow Removal Effect of Photovoltaic Power Plants Based on Hyperspectral Technology

The Dalad Top-Runner Photovoltaic Power Station is located in Dalad Banner, Inner Mongolia, in a mid-latitude region around 40 degrees north latitude. Winter temperatures are low and snowfall is frequent. Accumulated snow reflects sunlight, and ice easily forms on the tempered glass surface of the photovoltaic panels beneath the snow, which is difficult to melt quickly, blocking sunlight and severely impacting power generation efficiency. A reasonable and economical method for rapid snow melting and removal not only helps increase the power generation of the photovoltaic power station and reduces operation and maintenance workload and costs, but also has significant application value.

Common snow removal solutions for photovoltaic power plants

1. Manual snow removal
Under normal circumstances, photovoltaic power plants can only rely on specialized personnel to push snow down using soft materials. This method is inefficient and consumes a lot of manpower and resources, especially when dealing with complex terrain or modules that are high off the ground. Currently, most photovoltaic power plants still use the most traditional method of manually clearing snow.

2. Robot snow removal

Commonly used self-propelled photovoltaic cleaning robots are suitable for large photovoltaic power plants, but they are expensive and not suitable for small photovoltaic power plants. Furthermore, their stability in low-temperature environments needs further verification.

3. Automatic snow removal by the tracking bracket

Adjusting the battery modules to their maximum tilt angle during snowfall facilitates snow sliding and effectively reduces snow accumulation on the module surface. Once the snow has cleared, the battery modules are returned to their normal angle. However, this approach is only suitable for tracking bracket systems such as horizontal single-axis, inclined single-axis, and dual-axis tracking; it is difficult to implement with fixed brackets.

4. Snow removal advantages of double-glass bifacial modules

After snowfall, the ground surface is covered with snow, increasing its ability to reflect sunlight. This increases the reflectivity of the back of the modules, enhancing their power generation capacity. The back of the double-glass bifacial photovoltaic (PV) module can continue to generate electricity through photoelectric conversion via diffuse reflection from the snow on the ground. The heat released during this conversion process also rapidly melts the snow on the front of the module, forming a water layer. This reduces friction between the snow and the module, and gravity allows the snow to slide off, minimizing the area and duration of snow cover on the front of the module. It is estimated that the snow on the front of the double-glass bifacial PV module can be cleared in approximately 1-3 hours. The snow removal effect is even better when used in conjunction with a tracking bracket snow removal system.

Common snow removal solutions for photovoltaic power plants

5. Snow melting technology based on the electrothermal principle of photovoltaic module PN junction

When a photovoltaic module is used as a load and a positive voltage is applied to its positive and negative terminals, a unidirectional current will be generated due to the PN junction structure inside the module. This working principle is similar to that of a light-emitting diode (LED). Due to the energy level difference of the PN junction and the resistance of the semiconductor region, when electrons pass through, energy is generated in the semiconductor region inside the photovoltaic module and converted into heat, thus raising the module temperature and acting as a snow-melting agent.

However, in areas with low ambient temperatures, since photovoltaic modules are installed outdoors and the backsheets of photovoltaic modules dissipate heat quickly, the temperature increase using the PN junction electrothermal principle is very limited. Therefore, this solution has no significant effect on snow melting and has certain limitations. In addition, an external bias power supply is required, with one power supply configured for every 1 to 2 strings. This means that a large-capacity power station would need to be equipped with multiple units, resulting in high investment costs and limited application.

6. Arrangement of heating cables

The heating cable's inner core consists of cold and hot wires, while the outer layer comprises an insulation layer, grounding layer, shielding layer, and outer sheath. When energized, the hot wires heat up and operate within a temperature range of 40–60°C. Buried within the filler layer, the heating cable transfers heat to the receiving body through heat conduction (convection) and far-infrared radiation (8-13µm). Distributed photovoltaic power stations can be installed around photovoltaic modules, gutters, and downpipes. When snow accumulates, the heating mode is activated to quickly melt the snow, but the investment cost is relatively high.

The Dalat Phase II project uses double-glass bifacial photovoltaic panels with a tracking bracket system for snow removal, which can significantly improve snow removal speed and increase power generation efficiency by about 15%.

△ Figure 1 Comparison of the extent and snow cover of the first and second phases of Dalat

△ Figure 2 Comparison of photovoltaic panel reflectivity in Dalate Phase I/Phase II (reflectivity increased by 10,000 times)

△ Figure 3 Comparison of reflectivity of photovoltaic panels after snow melting in Dalate Phase I and Phase II (reflectivity increased by 10,000 times)

CAS Xiguang Aerospace - Snow Cover Monitoring

By using hyperspectral satellites to continuously monitor the Dalate photovoltaic power station, we obtained image data taken during periods of snow cover and snowlessness, and performed atmospheric corrections to calculate the average reflectance of the first and second phases of the project.

Figure 1 visually illustrates the project area, allowing for easy identification of snow cover. Phase I project shows significantly more snow cover, while Phase II project exhibits no noticeable snow accumulation. Figure 2 illustrates the average reflectivity difference between Phase I and Phase II projects under snow cover. Phase I shows significantly higher reflectivity than Phase II, with a peak reflectivity increase of approximately 11.8% in the 450-850nm wavelength range, indicating higher snow cover. This higher reflectivity leads to energy loss and a decrease in power generation efficiency. Figure 3 compares the reflectivity of Phase I and Phase II after snow melts, showing that the reflectivity of both phases essentially returns to similar levels after the snow melts.

Research Conclusions and Applications

The difference in reflectivity between the first and second phases of the project verified that the new double-sided double-glass photovoltaic modules used in the second phase, combined with the tracking bracket system, have a better snow removal effect.

Combination Photovoltaic panel dust monitoring based on hyperspectral remote sensingThis indicates that hyperspectral remote sensing technology has certain application value in large-scale photovoltaic panel condition monitoring under various environments.