1. Solar energy resources
Given a fixed installed capacity, the power generation of a photovoltaic power station is determined by the intensity of solar radiation, and there is a positive correlation between solar radiation and power generation. The intensity and spectral characteristics of solar radiation vary with weather conditions.
2. Component Installation Method
The radiation from tilted surfaces varies depending on the installation angle in the same area. The radiation from tilted surfaces can be increased by adjusting the tilt angle of the solar panels (if the bracket is fixed and adjustable) or by adding tracking equipment (if the bracket is tracking type).
3. Inverter capacity ratio
Inverter capacity ratio refers to the ratio of the inverter's rated power to the capacity of the photovoltaic modules it supports.
Because the power generated by photovoltaic modules is reduced in many stages before reaching the inverter, and because inverters and transformer substations rarely operate at full capacity, the capacity of photovoltaic modules should be slightly larger than the rated capacity of the inverter. Based on experience, in areas with good solar resources, a photovoltaic module to inverter ratio of 1.2:1 is considered optimal.
4. Component serial-parallel matching
Connecting components in series will result in current loss due to the current difference between the components, while connecting them in parallel will result in voltage loss due to the voltage difference between the strings.
The CNCA/CTS00X-2014 "Technical Specification for Performance Testing and Quality Assessment of Grid-Connected Photovoltaic Power Plants" (Draft for Comments) requires that the maximum loss due to series mismatch of modules should not exceed 2%.
5. Component occlusion
Module shading includes dust, snow, weeds, trees, solar panels, and other buildings. Shading reduces the amount of radiation received by the module, affects heat dissipation, and thus causes a decrease in module output power. It may also lead to hot spots.
6. Component temperature characteristics
As the temperature of a crystalline silicon solar cell increases, the open-circuit voltage decreases. In the range of 20-100℃, the voltage of each cell decreases by approximately 2mV for every 1℃ increase in temperature; while the current increases slightly with increasing temperature. Overall, the power of a solar cell decreases with increasing temperature, with a typical power temperature coefficient of -0.35%/℃, meaning that for every 1℃ increase in cell temperature, the power decreases by 0.35%.
7. Component power degradation
Module power degradation refers to the phenomenon that the output power of a module gradually decreases as the duration of sunlight exposure increases. Module degradation is related to the characteristics of the module itself. The degradation phenomenon can be roughly divided into three categories: sudden degradation of module power caused by destructive factors; initial light-induced degradation of the module; and aging degradation of the module.
According to CNCA/CTS00X-2014 "Technical Specification for Performance Testing and Quality Assessment of Grid-Connected Photovoltaic Power Stations", the degradation rate of polycrystalline silicon modules should not exceed 2.5% within one year and 3.2% within two years; the degradation rate of monocrystalline silicon modules should not exceed 3.0% within one year and 4.2% within two years.
8. Equipment operational stability
Equipment failures and shutdowns in photovoltaic power generation systems directly impact the power plant's output. For example, if AC equipment above the inverter fails and shuts down, the resulting power loss will be enormous. Additionally, even if equipment is running, but not operating at its optimal performance level, it will still cause power loss.
9. Routine maintenance
Routine maintenance and repairs are essential for power plants, and a well-planned maintenance schedule can reduce power loss. Power plants should determine maintenance times reasonably based on their own circumstances, and at the same time, improve maintenance efficiency to minimize power generation loss due to routine maintenance and repairs.
10. Grid absorption
Due to grid absorption requirements, some regional grid dispatching systems require photovoltaic power plants to operate at limited power.
Summarize
Factors affecting the power generation of photovoltaic power plants include solar energy resources, module installation method, inverter capacity ratio, module series-parallel matching, module shading, module temperature characteristics, module power decay, equipment operation and maintenance stability, routine maintenance, and grid absorption. These factors all affect the power generation of the power plant to varying degrees.
