What are the solar tracking bracket selection criteria?
Publish Time：2022-09-05
Sources：
The most fundamental difference between different installation methods is the difference in power generation they bring. Of course, the initial investment and operation and maintenance costs will also vary.
solar tracking bracket
1. The increase in power generation brought by different photovoltaic tracking brackets
Compared with the fixed installation with the optimal tilt angle, the power generation of horizontal single-axis tracking is increased by 17%~30%, the power generation of single-axis tracking with a tilt of 5° is increased by 21%~35%, and the power generation of dual-axis tracking is increased. 35%~43%. However, under different latitudes, the power generation rate of various operation modes is obviously different. There are roughly a few rules:
1) Best inclination fixing bracket
In low latitudes, because the optimal inclination angle is small, the increase in power generation is very small (for example, at 8°, it is almost constant); in high latitude areas, the optimal inclination angle is large, and the power generation increases significantly (such as at 50°C). °, an increase of about 25%).
2) Flat uniaxial tracking bracket
This mode of operation tracks the change in the incident angle of the sun within a day, and its rate of increase in power generation is significantly better in low-latitude regions than in high-latitude regions. It is generally believed that this operation mode is more suitable for use in areas with a latitude lower than 30°, and it can increase the power generation by 20%-30% compared with the optimal inclination fixed bracket. Of course, in high latitude regions, the relative "method 1" can also be improved by nearly 20%.
3) Oblique uniaxial tracking bracket
This mode of operation clearly combines the advantages of the "Optimum Inclination Fixed Bracket" and the "Flat Single Axis Tracking Bracket". Just as "Best Tilt Fixed" is not suitable for low latitudes, this operating mode does not perform much better in low latitudes than "Flat Single Axis Tracking Stand". Therefore, it is more suitable for high latitude regions. In this way, the forces on the support structures (brackets, rotating shafts) on both sides of the array must be different. Since the optimal inclination angle in high latitudes is large, if the "optimal inclination angle of the single axis" is adopted, the unbalanced force on both sides will be very large. Therefore, a smaller inclination angle is generally adopted in the project.
4) Dual axis tracking bracket
Since the change of the incident angle of the sun within a day and a year is tracked, the improvement of power generation in this way is obviously the highest.
5) Fixed adjustable bracket
This mode of operation is to adjust the inclination angle of the bracket according to the change of the incident angle of the sun within a year, so as to achieve an increase in power generation. It has become more popular since last year, and will be highlighted below.
Second, the application of different solar tracking brackets
No matter how you compare, tracking mounts are better than fixed solar mounts, so why is fixed photovoltaic mounts still everyone's favorite way to operate?
First, initial investment, land occupation, operation and maintenance costs
Whether it is the investment of solar photovoltaic brackets, the occupation of the same installed capacity, or the operation and maintenance costs, the following rules are followed:
Dual-axis tracking type > Oblique single-axis tracking type > Flat single-axis tracking type > Fixed and adjustable type > Optimal tilt angle fixed type
For example, a 10MW project is considered based on the average full power generation hours of 1300h in 25 years. If the investment increases by 0.1 yuan/W, it will be cost-effective to increase the net income (income from the increase in annual power generation - operation and maintenance costs) by about 100,000 yuan ( According to the electricity price of 0.95 yuan/kWh, the power generation can be increased by about 0.81%, and the income of 100,000 yuan can be obtained). For example, the investment of the flat single-axis tracking bracket increases by about 1 yuan/W, and the annual net income needs to increase by 1 million in the future. Even considering the operation and maintenance costs of hundreds of thousands of dollars a year, it is still cost-effective.
Second, the failure rate and tracking accuracy
The high failure rate of solar tracking brackets is a common feedback problem. The existing photovoltaic power stations in my country are mainly located in the northwest, where the wind and sand are large, and the damage to the tracking axis is particularly large. Once a failure occurs, let alone the increase in power generation, even the basic power generation cannot be guaranteed! In addition to the failure rate, the tracking accuracy is not ideal, especially for dual-axis tracking. Therefore, the increase in power generation will be lower than originally expected.
3. Solar fixed adjustable bracket
The reason why the "fixed adjustable bracket" is singled out is purely because this method has been popular since last year. At present, there are about 4 kinds of fixed and adjustable brackets on the market. According to the feedback from the operation and maintenance personnel of the power station: the adjustment of the inclination angle is a very tiring task, and everyone is reluctant to adjust it, resulting in a lower than expected value of power generation. But how the fixed adjustable failure rate has not received feedback yet.
2. Site conditions suitable for the use of tracking brackets
Tracking installations do increase power generation. However, not everywhere a tracked stand works well. What kind of conditions are suitable for the use of tracking brackets?
1. Areas with a high "direct exposure ratio"
The "direct light ratio" is a very important parameter when conducting solar resource analysis.
Direct ratio = direct radiation on the horizontal plane: direct radiation on the horizontal plane
Tracking solar brackets, as the name suggests, is to track the incident angle of sunlight through the brackets, and try to make the sunlight perpendicular to the photovoltaic modules. Tracking only makes sense where there is a large proportion of direct radiation.
Another parameter related to the direct radiation ratio is the "direct normal radiation", or DNI for short, which is the direct radiation that is always perpendicular to the direction of solar incidence. Where the direct irradiation ratio is large, the DNI will also be relatively large. The following table shows the direct shot ratio and DNI of the 8 leader bases.
In areas with a high direct radiation ratio, the DNI value is higher than the total radiation on the horizontal plane, and dual-axis tracking is used, and the power generation will be greatly improved; in places with a low direct radiation ratio, dual-axis tracking will not work well. Compared with the fixed power generation rate, the double-axis tracking type has a good correlation with the direct radiation of the project site, and the correlation coefficient reaches 0.96. Therefore, it is important to pay attention to the direct sunlight ratio of the project site before deciding whether to adopt the tracking type.
2. "Lower Latitude" Regions
1 The improvement effect of power generation
Latitude has a great influence on the improvement of tracking power generation. In low latitude areas, flat uniaxial will have better effect; in high latitude areas, flat uniaxial effect is not obvious, and oblique uniaxial solar mounts or dual-axis tracking mounts are required.
2 area
In high latitude areas, the installation method of the flat single-axis tracking bracket is adopted, and the floor area is slightly increased; but the use of inclined single-axis and dual-axis tracking type will greatly increase the floor area. In the area of 40°N latitude, the floor space of the inclined uniaxial tracking bracket is almost twice that of the fixed type. In high-latitude areas with tight land use and high land costs, it is not suitable to use inclined single-axis and dual-axis tracking.
3 Summary
According to the above analysis, for projects in high latitude areas, from the perspective of increasing power generation, oblique single-axis and dual-axis tracking should be adopted; but from the perspective of floor space, oblique single-axis and dual-axis tracking will greatly increase the floor space. area.
In view of the above reasons, it is a relatively good solution to use flat single-axis tracking in low-latitude areas; in high-latitude areas, when land costs are relatively cheap, oblique single-axis and dual-axis tracking can be considered.
3. Cost-effectiveness analysis
Tracking can indeed increase power generation, but it will also increase project investment and operation and maintenance costs. Compared with the fixed type, the cost increase of the tracking type is mainly reflected in three aspects: 1) the cost of the bracket is increased, 2) the floor space is increased, and 3) the operation and maintenance cost is increased.
1 Operation and maintenance costs
1) Compared with the fixed photovoltaic support, the height of the tracking photovoltaic support is higher, the cleaning and maintenance are more difficult, and the cost will increase;
2) The tracking system leads to high self-consumption;
3) The failure rate of the tracking system is relatively high.
2 area
As mentioned above, using the tracking installation method will greatly increase the floor area, which will increase the land cost of the project.
3 cost-effective analysis
Taking a project of 10,000 kW in the second-class electricity price area (electricity price of 0.88 yuan/kWh) as an example, assuming that the average annual full power generation hours of the optimal fixed inclination angle is 1200h, the use of flat single-axis tracking power generation increases by 15%, and the use of dual-axis Tracking power generation increased by 25%. It is assumed that the follow-up operation and maintenance costs do not increase.
4. Comprehensive analysis
As far as the usage conditions of the tracking installation method are concerned:
In places with high direct irradiation ratio, the use of tracking type will greatly increase the power generation of the project;
Flat single-axis tracking is suitable for low latitude areas, and oblique single-axis or dual-axis tracking is suitable for high latitude areas.
In terms of value for money:
In areas with good solar energy resources and high power generation, that is, areas with high total annual radiation, the cost-effectiveness of tracking photovoltaic mount will be higher.
1. The increase in power generation brought by different photovoltaic tracking brackets
Compared with the fixed installation with the optimal tilt angle, the power generation of horizontal single-axis tracking is increased by 17%~30%, the power generation of single-axis tracking with a tilt of 5° is increased by 21%~35%, and the power generation of dual-axis tracking is increased. 35%~43%. However, under different latitudes, the power generation rate of various operation modes is obviously different. There are roughly a few rules:
1) Best inclination fixing bracket
In low latitudes, because the optimal inclination angle is small, the increase in power generation is very small (for example, at 8°, it is almost constant); in high latitude areas, the optimal inclination angle is large, and the power generation increases significantly (such as at 50°C). °, an increase of about 25%).
2) Flat uniaxial tracking bracket
This mode of operation tracks the change in the incident angle of the sun within a day, and its rate of increase in power generation is significantly better in low-latitude regions than in high-latitude regions. It is generally believed that this operation mode is more suitable for use in areas with a latitude lower than 30°, and it can increase the power generation by 20%-30% compared with the optimal inclination fixed bracket. Of course, in high latitude regions, the relative "method 1" can also be improved by nearly 20%.
3) Oblique uniaxial tracking bracket
This mode of operation clearly combines the advantages of the "Optimum Inclination Fixed Bracket" and the "Flat Single Axis Tracking Bracket". Just as "Best Tilt Fixed" is not suitable for low latitudes, this operating mode does not perform much better in low latitudes than "Flat Single Axis Tracking Stand". Therefore, it is more suitable for high latitude regions. In this way, the forces on the support structures (brackets, rotating shafts) on both sides of the array must be different. Since the optimal inclination angle in high latitudes is large, if the "optimal inclination angle of the single axis" is adopted, the unbalanced force on both sides will be very large. Therefore, a smaller inclination angle is generally adopted in the project.
4) Dual axis tracking bracket
Since the change of the incident angle of the sun within a day and a year is tracked, the improvement of power generation in this way is obviously the highest.
5) Fixed adjustable bracket
This mode of operation is to adjust the inclination angle of the bracket according to the change of the incident angle of the sun within a year, so as to achieve an increase in power generation. It has become more popular since last year, and will be highlighted below.
Second, the application of different solar tracking brackets
No matter how you compare, tracking mounts are better than fixed solar mounts, so why is fixed photovoltaic mounts still everyone's favorite way to operate?
First, initial investment, land occupation, operation and maintenance costs
Whether it is the investment of solar photovoltaic brackets, the occupation of the same installed capacity, or the operation and maintenance costs, the following rules are followed:
Dual-axis tracking type > Oblique single-axis tracking type > Flat single-axis tracking type > Fixed and adjustable type > Optimal tilt angle fixed type
For example, a 10MW project is considered based on the average full power generation hours of 1300h in 25 years. If the investment increases by 0.1 yuan/W, it will be cost-effective to increase the net income (income from the increase in annual power generation - operation and maintenance costs) by about 100,000 yuan ( According to the electricity price of 0.95 yuan/kWh, the power generation can be increased by about 0.81%, and the income of 100,000 yuan can be obtained). For example, the investment of the flat single-axis tracking bracket increases by about 1 yuan/W, and the annual net income needs to increase by 1 million in the future. Even considering the operation and maintenance costs of hundreds of thousands of dollars a year, it is still cost-effective.
Second, the failure rate and tracking accuracy
The high failure rate of solar tracking brackets is a common feedback problem. The existing photovoltaic power stations in my country are mainly located in the northwest, where the wind and sand are large, and the damage to the tracking axis is particularly large. Once a failure occurs, let alone the increase in power generation, even the basic power generation cannot be guaranteed! In addition to the failure rate, the tracking accuracy is not ideal, especially for dual-axis tracking. Therefore, the increase in power generation will be lower than originally expected.
3. Solar fixed adjustable bracket
The reason why the "fixed adjustable bracket" is singled out is purely because this method has been popular since last year. At present, there are about 4 kinds of fixed and adjustable brackets on the market. According to the feedback from the operation and maintenance personnel of the power station: the adjustment of the inclination angle is a very tiring task, and everyone is reluctant to adjust it, resulting in a lower than expected value of power generation. But how the fixed adjustable failure rate has not received feedback yet.
2. Site conditions suitable for the use of tracking brackets
Tracking installations do increase power generation. However, not everywhere a tracked stand works well. What kind of conditions are suitable for the use of tracking brackets?
1. Areas with a high "direct exposure ratio"
The "direct light ratio" is a very important parameter when conducting solar resource analysis.
Direct ratio = direct radiation on the horizontal plane: direct radiation on the horizontal plane
Tracking solar brackets, as the name suggests, is to track the incident angle of sunlight through the brackets, and try to make the sunlight perpendicular to the photovoltaic modules. Tracking only makes sense where there is a large proportion of direct radiation.
Another parameter related to the direct radiation ratio is the "direct normal radiation", or DNI for short, which is the direct radiation that is always perpendicular to the direction of solar incidence. Where the direct irradiation ratio is large, the DNI will also be relatively large. The following table shows the direct shot ratio and DNI of the 8 leader bases.
In areas with a high direct radiation ratio, the DNI value is higher than the total radiation on the horizontal plane, and dual-axis tracking is used, and the power generation will be greatly improved; in places with a low direct radiation ratio, dual-axis tracking will not work well. Compared with the fixed power generation rate, the double-axis tracking type has a good correlation with the direct radiation of the project site, and the correlation coefficient reaches 0.96. Therefore, it is important to pay attention to the direct sunlight ratio of the project site before deciding whether to adopt the tracking type.
2. "Lower Latitude" Regions
1 The improvement effect of power generation
Latitude has a great influence on the improvement of tracking power generation. In low latitude areas, flat uniaxial will have better effect; in high latitude areas, flat uniaxial effect is not obvious, and oblique uniaxial solar mounts or dual-axis tracking mounts are required.
2 area
In high latitude areas, the installation method of the flat single-axis tracking bracket is adopted, and the floor area is slightly increased; but the use of inclined single-axis and dual-axis tracking type will greatly increase the floor area. In the area of 40°N latitude, the floor space of the inclined uniaxial tracking bracket is almost twice that of the fixed type. In high-latitude areas with tight land use and high land costs, it is not suitable to use inclined single-axis and dual-axis tracking.
3 Summary
According to the above analysis, for projects in high latitude areas, from the perspective of increasing power generation, oblique single-axis and dual-axis tracking should be adopted; but from the perspective of floor space, oblique single-axis and dual-axis tracking will greatly increase the floor space. area.
In view of the above reasons, it is a relatively good solution to use flat single-axis tracking in low-latitude areas; in high-latitude areas, when land costs are relatively cheap, oblique single-axis and dual-axis tracking can be considered.
3. Cost-effectiveness analysis
Tracking can indeed increase power generation, but it will also increase project investment and operation and maintenance costs. Compared with the fixed type, the cost increase of the tracking type is mainly reflected in three aspects: 1) the cost of the bracket is increased, 2) the floor space is increased, and 3) the operation and maintenance cost is increased.
1 Operation and maintenance costs
1) Compared with the fixed photovoltaic support, the height of the tracking photovoltaic support is higher, the cleaning and maintenance are more difficult, and the cost will increase;
2) The tracking system leads to high self-consumption;
3) The failure rate of the tracking system is relatively high.
2 area
As mentioned above, using the tracking installation method will greatly increase the floor area, which will increase the land cost of the project.
3 cost-effective analysis
Taking a project of 10,000 kW in the second-class electricity price area (electricity price of 0.88 yuan/kWh) as an example, assuming that the average annual full power generation hours of the optimal fixed inclination angle is 1200h, the use of flat single-axis tracking power generation increases by 15%, and the use of dual-axis Tracking power generation increased by 25%. It is assumed that the follow-up operation and maintenance costs do not increase.
4. Comprehensive analysis
As far as the usage conditions of the tracking installation method are concerned:
In places with high direct irradiation ratio, the use of tracking type will greatly increase the power generation of the project;
Flat single-axis tracking is suitable for low latitude areas, and oblique single-axis or dual-axis tracking is suitable for high latitude areas.
In terms of value for money:
In areas with good solar energy resources and high power generation, that is, areas with high total annual radiation, the cost-effectiveness of tracking photovoltaic mount will be higher.