Calculation method of power generation of photovoltaic power station,theoretical annual power generation=annual average total solar radiation*total area of battery*photoelectric conversion efficiency.However,due to the influence of various factors,the power generation of photovoltaic power station is not so much in fact.The actual annual power generation=theoretical annual power generation*actual power generation efficiency.
So what are the factors that affect the power generation of photovoltaic power plants?The following is my daily design and construction experience,to tell you some basic knowledge of distributed power generation.
1.1 solar radiation
Solar cell module is a device that converts solar energy into electric energy.The intensity of light radiation directly affects the power generation.
The solar radiation data of each region can be obtained through the NASA meteorological data query website,or through photovoltaic design software such as pv-sys and retscreen.
1.2 tilt angle of solar cell module
The data obtained from the meteorological station is generally the solar radiation on the horizontal plane,which can be converted into the radiation on the inclined plane of the photovoltaic array to calculate the power generation of the photovoltaic system.The optimum inclination is related to the latitude of the project site.The approximate empirical values are as follows:
A.latitude 0°~25°,inclination angle equal to latitude
B.latitude 26°-40°,and the inclination is equal to latitude plus 5°-10°
C.latitude 41°-55°,and the inclination is equal to latitude plus 10°-15°
1.3 conversion efficiency of solar cell module
Solar cell module is composed of high efficiency crystalline silicon solar cell,ultra white toughened glass,EVA,transparent TPT back plate and aluminum alloy frame,with glass transmittance loss and circuit loss.
1.4 system loss
Like all products,in the 25 year life cycle of photovoltaic power plants,the efficiency of components and the performance of electrical components will gradually reduce,and the power generation will decrease year by year.In addition to these natural aging factors,there are also quality problems of components and inverters,line layout,dust,series and parallel losses,cable losses and other factors.
1.4.1 combined loss
In case of series connection,the current loss will be caused by the current difference of components;in case of parallel connection,the voltage loss will be caused by the voltage difference of components;and the combined loss can reach more than 8%,which is less than 10%according to the standard of China Engineering Construction Standardization Association.
Therefore,in order to reduce portfolio loss,we should pay attention to:
1)components with the same current shall be strictly selected for series connection before the installation of the power station.
2)attenuation characteristics of components shall be consistent as much as possible.
1.4.2 dust cover
Among all the factors that affect the overall power generation capacity of photovoltaic power plants,dust is the first killer.
The influence of dust photovoltaic on the power station is mainly as follows:to reach the light of the module through shielding,so as to affect the power generation;to affect the heat dissipation,so as to affect the conversion efficiency;the acid-base dust is deposited on the surface of the module for a long time,which erodes the surface of the panel and causes the rough surface,which is conducive to the further accumulation of dust,and at the same time increases the diffuse reflection of sunlight.Therefore,components need to be wiped and cleaned irregularly.
At present,the cleaning of photovoltaic power station mainly includes three ways:sprinkler,manual cleaning and robot.
1.4.3 temperature characteristics
When the temperature increases by 1℃,the maximum output power of crystalline silicon solar cell decreases by 0.04%,the open circuit voltage decreases by 0.04%(-2mV/℃),and the short circuit current increases by 0.04%.In order to reduce the influence of temperature on power generation,good ventilation conditions of components should be maintained.
1.4.4 loss of line and transformer
The line loss of DC and AC circuits of the system shall be controlled within 5%.Therefore,the conductor with good conductivity should be used in the design,and the conductor should have enough diameter.During system maintenance,pay special attention to whether the connector and terminal are firm.
1.4.5 inverter efficiency
Because the inverter has inductor,transformer,IGBT,MOSFET and other power devices,it will produce loss in operation.Generally,the efficiency of series inverter is 97-98%,that of centralized inverter is 98%,and that of transformer is 99%.
1.4.6 shadow and snow cover
In distributed power plant,if there are tall buildings around,it will cause shadow to components,so it should be avoided in design.According to the circuit principle,when the components are connected in series,the current is determined by the least one,so if there is a shadow,it will affect the generating power of this component.
When there is snow on the components,it will also affect the power generation and must be cleaned as soon as possible.