To build a photovoltaic power station, in order to obtain a higher power generation, it is necessary to shield some factors affecting photovoltaic power generation, or to eliminate or reduce its impact, and try to maximize the amount of power generation to improve economic efficiency.
First, the amount of solar radiation
The level of solar radiation has a decisive influence on the amount of electricity generated. Therefore, the construction of photovoltaic power plants should first choose photovoltaic power plants in areas with large solar radiation.
A solar cell module is a device that converts solar energy into electrical energy, and the intensity of the light radiation directly affects the amount of power generated. Solar radiation data for each region can be obtained through the NASA Meteorological Data Enquiry website.
It can also be obtained with the help of photovoltaic design software such as PV-SYS, RETScreen.
Second, the arrangement direction of photovoltaic modules
In the design, the vertical arrangement is arranged in a lateral direction, which can significantly increase the amount of power generation.
In the design of photovoltaic power plants, there are two design schemes for the placement of photovoltaic modules: lateral arrangement and vertical arrangement. This "one horizontal and one vertical" arrangement of photovoltaic modules has too much impact on power generation!
Third, the impact of array spacing
Increasing the array spacing can significantly increase the amount of power generated.
Array spacing is a very important parameter during plant design. In order to reduce the floor space, the spacing between the arrays is often too small, even if it is designed according to the specifications. The main reason is that the actual effect of the sun shadow caused by the photovoltaic modules between the PV power plant design and the actual power generation is not considered. In the morning and evening, the photovoltaic modules will inevitably have occlusion, resulting in loss of power generation.
Fourth, the photovoltaic module adds bypass diode
Hot spot effect: The solar cell component that is shielded in a series branch will be used as a load to consume the energy generated by other illuminated solar cell components. The shaded solar cell component will heat up at this time. This is the hot spot effect. .
This effect can seriously damage the solar cell. Part of the energy generated by a solar cell with light may be consumed by the obscured battery. In order to prevent the solar cell from being damaged by the hot spot effect, it is preferable to connect a bypass diode between the positive and negative terminals of the solar cell module to prevent the energy generated by the illumination component from being consumed by the shielded component. Therefore, the function of the bypass diode is: when the hot spot effect of the battery chip can not generate electricity, it acts as a bypass, so that the current generated by other battery cells flows out from the diode, so that the solar power generation system continues to generate electricity, not because of a certain battery. There is a problem with the chip and the power generation circuit is unreasonable.
Fifth, the tilt angle of the solar cell module
Allowing photovoltaic modules to absorb solar radiation as much as possible is a factor that must be considered in ensuring the amount of electricity generated by photovoltaic power plants. Therefore, the solar mounting structure support tilt angle of the photovoltaic module has a great influence on the amount of power generation.
The data obtained from the weather station is generally the amount of solar radiation on the horizontal plane, which is converted into the radiation amount of the inclined surface of the photovoltaic array to calculate the power generation of the photovoltaic system. The optimum tilt angle is related to the latitude of the project location.
The empirical data under normal circumstances are as follows:
a) Latitude 0°～25°, the inclination angle is equal to the latitude
b) latitude 26°～40°, inclination equal to latitude plus 5°～10°
c) latitude 41°～55°, inclination equal to latitude plus 10°～15°
Sixth, the conversion efficiency of solar photovoltaic modules
The quality of solar photovoltaic modules is mixed. Do not purchase cheap PV modules due to greed and cheapness, resulting in loss of power generation due to small losses.
Seven, system loss
1) Long-term effects of natural aging on power generation
The natural aging of the equipment has a long-term impact on the amount of power generation. It has been dragging down the power generation in the life-cycle power station. In the life cycle of the PV power plant for 25 years, the component efficiency and the component performance of the electrical equipment will gradually decrease. It is decreasing year by year.
2) The long-term impact of equipment procurement quality.
For the quality problems of photovoltaic modules, inverters, cables, etc., the construction of photovoltaic power plants should consider the cost of life and benefits, save time during construction, the loss during the operation period will be greater, and the reduction in power generation revenue will be greater.
3) System layout, circuit layout, dust, series and parallel loss, cable loss and other factors.
In the case of series connection, the current will be lost due to the difference of the current of the components; the parallel will cause voltage loss due to the voltage difference of the components; and the combined loss can reach more than 8%, and the standard of China Engineering Construction Standardization Association is less than 10%.
Therefore, in order to reduce the combination loss, we should pay attention to:
a) The components with the same current should be selected in series before the installation of the power station.
b) The attenuation characteristics of the components are as uniform as possible.
In the financial model of photovoltaic power plants, the system's power generation is generally reduced by about 5% in three years. After 20 years, the power generation is reduced to 80%. If this part of the loss can be reduced, it will be a huge benefit.
Eight, occlusion loss
1) Dust blocking
During the operation period, dust is the biggest killer among all the factors that affect the overall power generation capacity of PV power plants.
The main effects of dust photovoltaic power plants are: the light reaching the components through the shielding, thus affecting the power generation; affecting the heat dissipation, thereby affecting the conversion efficiency; the acid-alkaline dust is deposited on the surface of the component for a long time, causing the surface to be rough and uneven. Conducive to the further accumulation of dust, while increasing the diffuse reflection of sunlight.
2) Shadow, snow cover
According to the circuit principle, when the components are connected in series, the current is determined by the least one block, so if there is a shadow, it will affect the power generation of this component.
In a distributed power station, if there are tall buildings around, it will cause shadows on the components, and should be avoided when designing.
When there is snow on the components, it will also affect power generation and must be removed as soon as possible.
Therefore, the components need to be wiped and cleaned irregularly. When maintaining the photovoltaic power station, according to the construction layout of the photovoltaic power station, the three cleaning methods of sprinkler, manual cleaning and robot are mainly considered. Timely cleaning and letting PV modules “clean” every day are the primary considerations for increasing power generation, especially during the operation period. It is important to establish a regular cleaning mechanism.
9. The effect of temperature on power generation
Photovoltaic modules have certain temperature requirements when generating electricity. This is the temperature characteristics of photovoltaic modules.
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 rises by 0.04%.
In order to reduce the effect of temperature on power generation, the components should be kept well ventilated.
X. Line and transformer losses
The line loss of the DC and AC circuits of the system should be controlled within 5%. To this end, it is designed to use conductive wires with sufficient diameter. Pay special attention to the connectors and the terminals when the system is being maintained.
XI, inverter efficiency
Inverters generate losses due to inductors, transformers, and power devices such as IGBTs and MOSFETs. The general string inverter efficiency is 97-98%, the centralized inverter efficiency is 98%, and the transformer efficiency is 99%.