Power generation from a solar photovoltaic (PV) project peaks in summer and dips during winter as the solar radiation intensity in winter is relatively low.

The major effects on the operation of solar power projects in winter are:

Low temperature

In cold weather, the ambient temperature drops and to below freezing point in some areas. Since the equipment in a solar PV project, such as solar panels, inverters, data collectors, and batteries, have a certain operating temperature range, the regular operation may be affected when the temperature is lower than the operating range temperature of the equipment. This should be considered when choosing the installation site and design of the system.

Recommendation

Equipment should be used in areas with temperatures within the equipment’s working limits. Items such as energy storage batteries, household PV inverters, and data collectors could be installed indoors or in a cold-proof environment.

Low temperature affects the Voc voltage of the PV system

Low temperature will cause the open-circuit voltage (Voc) of PV strings to increase. If the initial design of the system has not fully considered the effect of temperature, the string Voc under low-temperature conditions could exceed the maximum allowable input voltage of the inverter, which will likely cause damage.

Consider an example of a 20 kW (maximum DC input voltage of 1100V) grid-tied PV system where 52 475W PV panels are used. Assuming that the lowest temperature in the area during the day is -15°C, the Voc is as per the following table:

Note: This PV panel’s open-circuit voltage temperature coefficient is -0.28%/℃. The value of this coefficient is different for different brands of PV panels.

Recommendation 

In the preliminary design of a PV project, it is necessary to fully consider the Voc of the PV string in extremely low temperatures.  Reserve sufficient margin to prevent the DC overvoltage in the winter from causing damage to the inverter. If the system has an “OV-DC alarm, it is necessary to immediately turn off the DC switch of the inverter and reduce the number of solar panels of the PV string.

Shading 

In winter, the angle of sunlight is narrower, and shadows are longer. Therefore, the PV array is more prone to shadow occlusion, which significantly affects the power generation of the PV system.

Recommendation

Cleaning the solar panel surface is advised to avoid dirt accumulation in winter.  It is also recommended to trim the overhanging trees to prevent shadows and remove furniture (in case of smaller residential installations) causing shadows if possible.

Snow cover

Another major problem in PV project operations in winter is snow accumulation. Snow covering the solar panel will reduce the solar radiation received by the panel and directly reduce the power generation. Moreover, the long-term uneven irradiation of the components may also cause more significant hidden dangers due to the hot spot effect.

In addition, snow cover is also a significant test for the structural design of the entire PV system due to its weight. Severe snow accumulation can even cause the PV array to collapse, causing equipment damage and personal injury, and property losses. 

Recommendation

Clear snow from panels in good time

When a PV plant accumulates snow, it needs to be cleaned quickly to prevent excessive snow accumulation from forming into ice, making it heavy and difficult to clean. Soft materials must be used for cleaning without scratching the glass and not stepping on the PV panel.

Snow must be removed from solar panels and equipment such as inverters and power distribution cabinets. For example, timely clearing of snow from the cooling air outlet of the inverter will prevent the surface of the inverter and the external cooling fan from icing.

Adapt design and installation to local conditions

In areas with frequent snowfall, the inclination angle of the solar panel must be increased within the optimal range recommended. Keeping within the limits of effective power generation, it is also convenient for snow on the surface of the solar panel to slide down on its own.

When installing, there has to be a reasonable distance between the bottom of the solar panel and the ground to prevent snow from accumulating at the bottom. In addition, it is recommended that solar panels be installed horizontally in areas where it snows frequently. Compared with vertical installations, this solution can ensure enough space between the bottom of the solar panel and the ground to avoid snow stacking. Due to the structural characteristics of a solar panel, adopting horizontal installation is conducive to reducing the loss of power generation.

It is also recommended to install the inverter in a place where snow can be avoided, such as under the solar panel array bracket or indoors. If the inverter is installed in an open area, it is recommended to add a baffle to prevent excessive snow from blocking the cooling air duct of the inverter or adding extra weight to cause the inverter to fall and be damaged.

Online operation and maintenance

The severe cold, wind, and snow in winter can cause difficulties in maintaining a PV project. So, in addition to the operation and maintenance activities such as snow removal and equipment replacement, most of the PV project inspection and operation and maintenance work is recommended to be remotely implemented through the Solis intelligent monitoring platform, SolisCloud.

Summary 

In addition to the adequate protection measures of warm and cold protection, a photovoltaic power station must be maintained, keeping the panels clean and clear of shadowing.  If snow falls, it must be cleared swiftly to avoid potential damage and loss of power.  When designing a new solar PV system, considering local conditions and weather patterns and taking adequate measures will ensure that power is maintained during harsh winters.

This article is sponsored by solar inverter manufacturer Ginlong Technologies.

 

Image Credit: Solis