As we all know, the photovoltaic power plant power generation method is calculated as 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 stations is not so much, the actual annual power generation = Theoretical annual power generation * Actual power generation efficiency. Here are the top ten factors that affect the power generation of photovoltaic power plants.
1, the amount of solar radiation
In the case of a certain solar cell component conversion efficiency, the photovoltaic system's power generation is determined by the solar radiation intensity.
Photovoltaic system uses only about 10% of solar radiation energy efficiency (solar cell efficiency, component loss, dust loss, inverter loss control, line loss, battery efficiency)
The power generation of photovoltaic power plants is directly related to the amount of solar radiation. The radiation intensity and spectral characteristics of the sun change with the weather conditions.
2, the solar cell assembly tilt angle
The principle of direct separation of the total amount of solar radiation and solar radiation on the inclined surface can be obtained: the total amount of solar radiation Ht on the inclined surface is composed of direct solar radiation amount Hbt sky-scattering amount Hdt and ground-reflected radiation amount Hrt.
Ht=Hbt+Hdt+Hrt
3, the efficiency of solar modules
Since the beginning of this century, China's solar photovoltaic industry has entered a period of rapid development, and the efficiency of solar cells continues to increase. With the help of nanotechnology, the conversion rate of silicon materials in the future can reach 35%, 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 materials has always been an important factor restricting the further development of the entire industry. The classical theoretical limit for silicon conversion is 29%. The record created in the laboratory is 25%, and this technology is being put into the industry.
The laboratory has been able to extract high-purity silicon directly from silica without converting it to metallic silicon, from which silicon can be extracted. This will reduce intermediate links and improve efficiency.
The combination of the third-generation nanotechnology and the existing technology can increase the conversion rate of silicon materials to more than 35%. If large-scale commercial production is introduced, the cost of solar power generation will be greatly reduced. Fortunately, such technology "has already been completed in the laboratory and is waiting for the process of industrialization."
4, combined loss
Anything connected in series 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%. The standard of China Engineering Construction Standardization Association is less than 10%.
note:
(1) In order to reduce the combined losses, the components with the same current should be strictly selected 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 regulations, the maximum output power of the solar cell components 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 drops by 0.04%, the open circuit voltage drops by 0.04% (-2mv/°C), and the short-circuit current increases by 0.04%. In order to avoid the effect of temperature on power generation, good ventilation of the components should be maintained.
6, dust loss
Dust loss at the power station may reach 6%! Components need to be wiped regularly.
7, MPPT tracking
Maximum output power tracking (MPPT) From the perspective of solar cell applications, the so-called application is the tracking of the maximum output power point of a solar cell. The MPPT function of the grid-tied system is completed in the inverter. It was recently studied to put it in a DC combiner box.
8, line loss
The line loss of the system's DC and AC circuits must be controlled within 5%. For this reason, it is designed to use conductive wires with good conductivity. The wires need to have a sufficient diameter. Construction does not allow cutting corners. During system maintenance, special attention should be paid to the connection of the external plug-in terminals and the terminal blocks.
9, controller, inverter efficiency
The charge and discharge circuit pressure drop of the controller must not exceed 5% of the system voltage. The efficiency of grid-connected inverters is currently greater than 95%, but this is conditional.
10, the efficiency of the battery (independent system)
The 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 has not yet attracted everyone's attention. The efficiency of lead-acid batteries is 80%; the efficiency of lithium-bismuth-phosphate batteries is more than 90%.
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