1. How is the annual power generation standard method of photovoltaic power plants calculated?

Calculation formula: Ep=HA×PAZ×K÷G, where:

Ep: on-grid power generation (kW h);

HA: total annual solar radiation on the horizontal plane (kW·h/m2);

PAZ: system installed capacity (kW);

G: Standard test condition irradiance, 1000W/m2;

K: The comprehensive efficiency coefficient is a correction coefficient after considering the influence of various factors, including:

(1) PV module temperature correction coefficient;

(2) Correction coefficients for the tilt angle and azimuth of the photovoltaic array;

(3) The stability of equipment operation and the availability of photovoltaic systems;

(4) Light utilization rate;

(5) Inverter efficiency;

(6) Loss of collector line and step-up transformer;

(7) Correction factor for surface contamination of photovoltaic modules;

(8) PV module power attenuation correction factor, etc.

This calculation method is the most comprehensive, but it is a challenge for non-senior photovoltaic practitioners to select an appropriate comprehensive efficiency coefficient. Generally speaking, according to the actual situation of the project, the value of K is between 75%-85%.

Calculation formula: Ep=HA×S×K1×K2, where:

HA: total solar radiation on the inclined plane (kW·h/m2);

S: is the total area of ​​the module (m2);

K1: module conversion efficiency, generally calculated according to the declared value of the module factory;

K2: Overall system efficiency.

The comprehensive efficiency coefficient K2 is a correction coefficient after considering the influence of various factors, including:

(1) Plant electricity, line loss, etc.

The loss of AC and DC distribution rooms and transmission lines accounts for about 3% of the total power generation, and the corresponding reduction and correction factor is taken as 97%.

(2) Inverter efficiency loss

The inverter efficiency is generally 95%~98%.

(3) Operating temperature loss of photovoltaic modules

As the temperature of PV modules increases, their efficiency decreases. Generally speaking, for every 1 degree increase in operating temperature of crystalline silicon photovoltaic modules, the power decreases by about 0.4%.

(4) Loss of other factors

In addition to the above factors, other uncertain factors that affect the power generation of photovoltaic power plants include the loss of unusable solar radiation, the reduction of the maximum power point tracking accuracy, and the grid consumption. The corresponding reduction and correction factor is generally taken as 95. %.

This calculation method is a variation of the first method, and is suitable for projects with inclined angle installation, as long as the inclined surface irradiance is obtained (or converted according to the horizontal irradiance: inclined surface irradiance = horizontal surface irradiance/cosA) , more accurate data can be calculated.

Calculation formula: Ep=H×P×K1, where:

P: system installation capacity (kW);

H: local standard sunshine hours (h);

K1: The overall efficiency of the system (value 75%~85%).

This calculation method is also a variation formula of the first method, which is simple and convenient, and can calculate the daily average power generation, which is very practical. This method requires the estimator to know the local meteorological conditions.

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