Many people know that the calculation method of photovoltaic power plant power generation is theoretical annual power generation = annual average total solar radiation * total battery area * photoelectric conversion efficiency. However, due to the influence of various factors, the power generation of photovoltaic power plants is actually not that much, and the actual annual power generation = theoretical annual power generation * actual power generation efficiency. So how many factors affect the power generation of photovoltaic power plants?
1. Solar radiation
In the case of a certain conversion efficiency of solar cell components, the power generation of the photovoltaic system is determined by the intensity of the sun's radiation. The solar radiation intensity and spectral characteristics change with the meteorological conditions.
2. The inclination angle of the solar cell module
For the total solar radiation on the inclined plane and the straight-divergent separation principle of solar radiation, the total solar radiation Ht on the inclined plane is composed of the direct solar radiation Hbt sky scattering Hdt and the ground reflected radiation Hrt.
Ht=Hbt+Hdt+Hrt
3. Efficiency of solar cell modules
As we all know, silicon is the mainstream material of solar photovoltaic cells, so its conversion rate has always been an important factor restricting the further development of the entire industry. At present, the conversion rate of silicon materials has been successfully increased to more than 35% in the laboratory, which is bound to greatly reduce the cost of solar power generation.
4. 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; while 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, attention should be paid to:
1) The components with the same current should be strictly selected in series before the power station is installed.
2) The attenuation characteristics of the components are as consistent as possible. According to the national standard GB/T--9535, the maximum output power of the solar cell module is tested after the test under the specified conditions, and its attenuation must not exceed 8%. 3: Isolation diodes are sometimes necessary.
5. Temperature characteristics
When the temperature rises by 1°C, the crystalline silicon solar cell: the maximum output power decreases by 0.04%, the open circuit voltage decreases by 0.04% (-2mv/°C), and the short-circuit current increases by 0.04%. In order to avoid the influence of temperature on power generation, the components should be well ventilated.
6. Dust loss
Dust in the power station can cause losses of up to 6%! Therefore, the components need to be wiped frequently.
7. Maximum output power tracking (MPPT)
From the perspective of solar cell application, the so-called application is the tracking of the maximum output power point of the solar cell. The MPPT function of the grid-connected system is completed in the inverter.
8. Line loss
The line loss of the DC and AC circuits of the system should be controlled within 5%. For this reason, wires with good electrical conductivity should be used in the design, and the wires need to have a sufficient diameter. Construction does not allow cutting corners. During system maintenance, special attention should be paid to whether the connectors and terminals are firm.
9. Battery efficiency (independent system)
An independent photovoltaic system needs to use a battery, and the charging and discharging efficiency of the battery directly affects the efficiency of the system, that is, it will affect the power generation of the independent system. Generally speaking, the efficiency of lead-acid batteries is about 80%; the efficiency of lithium phosphate batteries is more than 90%.
10. Efficiency of controller and photovoltaic inverter
The voltage drop of the charging and discharging circuit of the controller shall not exceed 5% of the system voltage. The efficiency of grid-connected photovoltaic inverters is currently greater than 95%, but this is conditional.