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Solar photovoltaic cell array installation points and maintenance difficulties analysis
- Apr 12, 2018 -

Solar cell array installation points

█ Azimuth angle of solar cell array installation

The azimuth angle of the solar cell array is the angle between the vertical plane of the square and the south direction (set the negative angle to the east and the positive angle to the west). Normally in the northern hemisphere, when the square is facing south (ie, the angle between the vertical plane of the square and the south is 0°), the solar battery power generation is the largest. When deviating from the south (northern hemisphere) by 30°, the power output of the square matrix will decrease by about 10% to 15%; when deviating from the south (northern hemisphere) by 60°, the power output of the square matrix will decrease by about 20% to 30%. . However, in the clear summer, the maximum time of solar radiation energy is after noon, so when the orientation of the square is slightly westward, the maximum generating power can be obtained in the afternoon.

In different seasons, the time of peak daily radiation at each azimuth is different. The orientation of the solar cell array is slightly eastward or westward, with the largest amount of power generated. The arrangement place of the square matrix is subject to many conditions. If the azimuth angle is to be adjusted so that the peak time of the load coincides with the peak power generation time in the day, the following formula can be referred to.

Azimuth = (peak hour of the load in a day (24-hour clock) -12) × 15 + (longitude -116)

█ The tilt angle of the solar cell array installation

The square array of solar cells is usually placed facing the equator, and there is a certain inclination angle with respect to the ground plane, that is, the angle between the square plane of the solar cell and the horizontal ground. For fixed-cell solar arrays with uniform load throughout the year, if the radiation volume of the designed slope is small, it means that more solar cells are needed to ensure the power supply to the users; if the amount of solar radiation received by the solar cell phalanx is different in each month Large, it means that a lot of batteries are needed to guarantee the electricity supply in the month when the solar radiation is low. These will increase the cost of the entire system. Therefore, determining the optimal inclination of the solar array is an indispensable part of the wind-solar hybrid power generation system.

In the design, it is hoped that the best tilt angle of the solar cell array will be obtained when the average annual power generation is maximum. The best tilt angle in a year is related to the local geographic latitude. When the latitude is high, the corresponding tilt angle is also large. . However, as with the azimuth angle, restrictions on the slope of the snowfall (slope is greater than 50% to 60%) must also be considered in the design.

For slopes where the snow falls, even if the amount of electricity generated during the snow-covered period is small and the total annual power generation also increases, for positive south (with azimuth angle of 0°), the tilt angle is from horizontal (with a tilt angle of 0° degrees). When the gradual transition to the optimal angle of inclination begins, the daily amount of radiation continues to increase until it reaches a maximum value, and then the amount of radiation is continuously reduced by increasing the angle of inclination. In particular, after the inclination angle is greater than 50° to 60°, the daily radiation amount decreases sharply until the final vertical placement, the power generation amount drops to the minimum. For situations where the azimuth is not 0°, the value of the daily amount of radiation on the slope is generally low, and the value of the maximum daily radiation is near the tilt angle close to the horizontal plane.

For the selection of the solar cell array angle, comprehensive consideration should be taken in conjunction with the following requirements:

1) Continuity. The total amount of solar radiation in a year is generally continuous, most of which are monotonously elevating, and individual ones have a few ups and downs, but generally do not fluctuate drastically.

2) Uniformity. Select dip angle, it is best to make the daily average amount of radiation received on the surface of the square array more uniform throughout the year, so as not to receive too much radiation in the summer, causing waste; and the amount of radiation received in the winter is too small, causing the battery to over discharge and even damage, Reduce system life, affect system power supply stability.

3) Greatness. When choosing the dip angle, it is necessary not only to obtain the maximum amount of radiation for the month with the smallest amount of radiation on the surface of the solar cell array, but also to take into account the annual average daily radiation amount not to be too small.

At the same time, specific analysis is required for specific situations. For example, some special loads (irrigation pumps, chillers, etc.) consume more power in summer, and the value of the solar cell array tilt angle should make solar cell arrays receive more radiation in summer than winter. A more approximate method can be used to determine the solar cell array tilt angle. Generally, in southern China, the inclination angle of the solar array may increase by 10° to 15° from the local latitude. In northern areas, the inclination may increase by 5° to 10° more than the local latitude. When the latitude is large, the angle of increase may be smaller. In the Qinghai-Tibet Plateau, the dip angle should not be too large and can be roughly equal to the local latitude. At the same time, in order to facilitate the design and installation of the solar cell array support, the array tilt is often taken as an integer.

The above is the relationship between the azimuth angle, the tilt angle and the power generation amount. For a specific design, the azimuth angle and the tilt angle of a certain solar cell array should be further integrated with the actual situation. For a fixed photovoltaic system, once the installation is completed, the solar cell array tilt angle and the azimuthal angle of the solar cell array cannot be changed. With the photovoltaic system installed with the tracking device, the solar cell array can follow the movement of the sun, so that the solar cell is always facing the sun, increasing the amount of solar radiation received by the solar cell array. However, currently there are relatively few tracking devices used in photovoltaic systems because the tracking devices are more complex, the initial cost and maintenance cost are higher, and the benefit of installing the tracking device to obtain additional solar radiation cannot offset the cost required to install the system.