Calculation method of photovoltaic power station power generation, theoretical annual power generation = annual average total solar radiation * total battery area * photoelectric conversion efficiency. However, due to the influence of various factors, the actual power generation of photovoltaic power stations is not that much. Actual annual power generation = theoretical annual power generation * actual power generation efficiency. So what factors affect the power generation of photovoltaic power plants?

1.1. Solar radiation amount

Solar cell modules are devices that convert solar energy into electrical energy. The intensity of light radiation directly affects the amount of power generated. Solar radiation data in various regions can be obtained through the NASA meteorological data query website, or with the help of photovoltaic design software such as PV-SYS and RETScreen.

1.2. Inclination angle of solar cell modules

The data obtained from the weather station is generally the amount of solar radiation on the horizontal plane, which is converted into the amount of radiation on the inclined surface of the photovoltaic array, so that the power generation of the photovoltaic system can be calculated. The optimal tilt angle is related to the latitude of the project location. The approximate experience values are as follows:

A. Latitude 0°~25°, tilt angle equal to latitude

B. Latitude 26°~40°, inclination equal to latitude plus 5°~10°

C. Latitude 41°~55°, inclination equal to latitude plus 10°~15°

1.3. Conversion efficiency of solar cell modules

1.4. System losses. Like all products, during the 25-year life cycle of a photovoltaic power station, the component efficiency and electrical component performance will gradually decrease, and the power generation will decrease year by year. In addition to these natural aging factors, there are also quality issues of components and inverters, circuit layout, dust, series and parallel losses, cable losses and other factors.

In the financial model of a general photovoltaic power station, the system power generation will decrease by about 5% in three years, and the power generation will decrease to 80% after 20 years.

1.4.1 Combination loss

Any series connection will cause current loss due to the current difference of the components; parallel connection will cause voltage loss due to the voltage difference of the components; and the combined loss can reach more than 8%, and the China Engineering Construction Standardization Association standard stipulates that it is less than 10%.

Therefore, in order to reduce portfolio losses, attention should be paid to:

1) Components with consistent current should be strictly selected and connected in series before installation in the power station.

2) The attenuation characteristics of the components are as consistent as possible.

1.4.2 Dust blocking

Among all the factors that affect the overall power generation capacity of photovoltaic power stations, dust is the number one killer. The main impacts of dust on photovoltaic power stations are: by blocking the light reaching the components, thereby affecting the power generation; affecting heat dissipation, thus affecting the conversion efficiency; acidic and alkaline dust is deposited on the surface of the components for a long time, corroding the panel surface and causing the panel surface to be rough and uneven. It is conducive to further accumulation of dust and increases the diffuse reflection of sunlight. Therefore, the components need to be wiped and cleaned from time to time.

At this stage, there are three main methods for cleaning photovoltaic power stations: sprinklers, manual cleaning, and robots.

1.4.3 Temperature characteristics

When the temperature rises by 1°C, crystalline silicon solar cells: the maximum output power drops by 0.04%, the open circuit voltage drops by 0.04% (-2mv/°C), and the short circuit current increases by 0.04%. In order to reduce the impact of temperature on power generation, components should be maintained with good ventilation conditions.

1.4.4 Line and transformer losses

The line loss of the system's DC and AC circuits must be controlled within 5%. For this reason, the design must use wires with good electrical conductivity, and the wires need to have sufficient diameter. During system maintenance, special attention should be paid to whether the connectors and terminals are secure.

1.4.5 Inverter efficiency

Since the inverter has inductors, transformers and power devices such as IGBT and MOSFET, it will generate losses during operation. Generally, the efficiency of string inverters is 97-98%, the efficiency of centralized inverters is 98%, and the efficiency of transformers is 99%.

1.4.6 Shadow and snow occlusion

In distributed power stations, if there are tall buildings around, they will cast shadows on the components and should be avoided as much as possible during design. According to the circuit principle, when components are connected in series, the current is determined by the smallest component. Therefore, if there is a shadow on one component, it will affect the power generation of this component. When there is snow on the components, it will also affect power generation and must be removed as soon as possible.