As we all know, 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, but due to various reasons, the actual power generation of photovoltaic power plants is not so much, the actual annual power generation = theoretical annual power generation * actual power generation efficiency. Let's analyze the top ten factors that affect the power generation of photovoltaic power plants!
1. The amount of solar radiation
When the conversion efficiency of the solar cell element is constant, the power generation of the photovoltaic system is determined by the radiation intensity of the sun.
The utilization efficiency of solar radiation energy by photovoltaic system is only about 10% (solar cell efficiency, component combination loss, dust loss, control inverter loss, line loss, battery efficiency)
The power generation of photovoltaic power plants is directly related to the amount of solar radiation, and the solar radiation intensity and spectral characteristics change with the meteorological conditions.
2. The tilt angle of the solar cell module
For the total amount of solar radiation on the inclined plane and the principle of direct-scattering separation of solar radiation, the total amount of solar radiation Ht on the inclined plane is composed of the direct solar radiation amount Hbt sky scattering amount Hdt and the ground reflected radiation amount Hrt.
Ht=Hbt+Hdt+Hrt
3. The efficiency of solar cell modules
Since the beginning of this century, my country's solar photovoltaic has entered a period of rapid development, and the efficiency of solar cells has been continuously improved. With the help of nanotechnology, the conversion rate of silicon materials will reach 35% in the future, which will become a "revolution" in solar power generation technology. Sexual breakthrough".
The mainstream material of solar photovoltaic cells is silicon, so the conversion rate of silicon material has always been an important factor restricting the further development of the entire industry. The classical theoretical limit for the conversion of silicon materials is 29%. The record set in the laboratory is 25%, and this technology is being put into industry.
Labs can already extract high-purity silicon directly from silica without converting it to metallic silicon and then extracting silicon from it. This can reduce intermediate links and improve efficiency.
Combining the third-generation nanotechnology with the existing technology can increase the conversion rate of silicon materials to more than 35%. If it is put into large-scale commercial production, it will greatly reduce the cost of solar power generation. The good news is that such a technology "has been completed in the laboratory and is waiting for the process of industrialization".
4. Combined loss
Any series connection will cause current loss due to the current difference of the components;
Any parallel connection will cause voltage loss due to the voltage difference of the components;
The combined loss can reach more than 8%, and the standard of China Engineering Construction Standardization Association stipulates that it is less than 10%.
Notice:
(1) In order to reduce the combined loss, the components with the same current should be strictly selected in series before the installation of the power station.
(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 element is tested after testing under the specified conditions, and its attenuation shall not exceed 8%
(3) Blocking diodes are sometimes necessary.
5. Temperature characteristics
When the temperature rises by 1℃, the crystalline silicon solar cell: the maximum output power 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 avoid the influence of temperature on power generation, the elements should be well ventilated.
6. Dust loss
Dust losses in power stations can reach 6%! Components need to be wiped frequently.
7. MPPT tracking
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. Recently, some researches put it in the DC combiner box.
8. Line loss
The line loss of the DC and AC circuits of the system should be controlled within 5%. For this reason, a wire with good electrical conductivity should be used in the design, and the wire needs to have a sufficient diameter. Construction is not allowed to cut corners. During system maintenance, special attention should be paid to whether the plug-in program is connected and whether the wiring terminals are firm.
9. Controller and inverter efficiency
The voltage drop of the charging and discharging circuits of the controller shall not exceed 5% of the system voltage. The efficiency of grid-connected inverters is currently greater than 95%, but this is conditional.
10. Battery efficiency (independent system)
An independent photovoltaic system needs to use a battery. The charging and discharging efficiency of the battery directly affects the efficiency of the system, that is, it affects the power generation of the independent system, but this point has not yet attracted everyone's attention. The efficiency of lead-acid battery is 80%; the efficiency of lithium phosphate battery is more than 90%.