We, at Eco Green Energy, are always being consulted about the efficiency of PV modules and systems. Here, we listed some factors that affect solar PV system efficiency for your references.
It is important to note that the process of producing electricity from solar energy is not 100% efficient. Environmental factors—such as temperature, soiling, and shading—as well as losses in the electrical components, can affect the efficiency of a PV system.
(A simple PV system with 18 modules)
Temperature
Solar panel efficiency varies with temperature. High temperatures have a negative impact on performance.
As we all know, we use a standard sunlight intensity to calibrate the nominal power of PV modules indoors at 25°C.
Considering that the actual outdoor working temperature of the module is generally higher than 25°C, and the heat dissipation conditions are different. To better compare the outdoor power generation of solar modules, we introduced the concept of Nominal module operating temperature (NMOT).
According to some research, temperature affects the typical value of solar PV system efficiency loss is 0.5%/°C above 25°C.
(Eco Green Energy HELIOS PLUS 455W PV modules temperature characteristics)
Soiling
Material that accumulates on the surface of PV panels can block light from reaching the solar cells, thereby reducing the generated power. The power loss due to soiling is highly variable, depending on the type of soiling (such as dust or snow), and the frequency of cleaning times.
Dust deposited on the light-receiving surface of the module will first reduce the light transmittance of the module surface. Then, secondly, it will change the incident angle of part of the light, causing the light to spread unevenly in the glass cover.
Studies have shown that under the same conditions, the output power of a clean solar module is at least 5% higher than that of a dust-accumulating module. And the higher the dust-accumulation, the greater the decrease in the output performance of the module.
Shading
As we knew, shading is the obstruction of irradiance due to trees, buildings, terrain, and other objects in the environment. The effect of shading on the power output of a solar installation is highly variable.
For example, when one solar cell in a panel cell string is shaded, all the preceding unshaded cells can dump the energy they produce into the first shaded cell as heat. This creates a hot spot that can potentially damage the solar panel if it lasts for a long time.
Mismatch
Due to manufacturing variations, modules of the same type can have slightly different electrical characteristics. This mismatch between modules can lead to a performance loss.
Inverter Efficiency
Converting DC into AC via an inverter is typically around 96-97% efficient. Actually, inverters typically have higher efficiency when the DC input power is high. The conversion efficiency takes a big hit when the input power is much less than the inverter’s rated power.
Age
Solar panels produce less energy the older they get. Typically, the decrease in performance is assumed to be around 0.5% per year.
Besides the above factors, some other factors impact the energy production of a solar system. For example, the design and installation of the system (tilt, orientation, stringing configuration, etc.), battery Efficiency, etc.
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