Comparison of Single & Dual Axis Tracker


Solar energy gets more and more popular in recent years, and the solar energy market has also grown significantly over the past decade. In 2019, the global photovoltaic installed capacity is 114.9GW, and the cumulative installed capacity has reached 627GW.

The generating capacity of photovoltaic system is not only related to the power of PV panel and operation condition, but also depends on the energy conversion efficiency. Therefore, the installation mode of PV panel array has a great influence on the efficiency of solar power generation system. But solar energy has some problems, such as low density, intermittency and constant change of light direction and intensity. Traditional solar PV plant choose mostly the fixed installation, that is, the panels are fixed at an Angle and do not change with the different  position of the sun. As a result, conversion efficiency will be seriously affected. According to estimates, if the PV panel with the angle of sunlight has 25 ° deviation, the output power of PV panel will fall about 10%, in order to solve this problem, the automatic tracker appears, in order to keep the sunlight always shining vertically on the photovoltaic panels, thus improve the photovoltaic conversion rate.

Now there are mainly two kinds of solar tracker, one is single-axis tracker and the another is dual-axis tracker. Single-axis tracker include horizontal single-axis tracking and tilt single-axis tracker. These trackers adopt an active tracking control strategy, which calculates the sun's position in the sky and controls the orientation of the PV panel. The trackers can be well adapted to the region of heavy snow or dust, and can also work reliably in the unattended photovoltaic power station.
So how to improve the PV panel conversion rate by changing the battery panel angle with the sunlight, which brings us to our topic, single axis tracker and dual axis tracker.

1. Single axis tracker
Single axis tracker, in which there is only one rotation axis, changes the position angle of the PV panel to maximize the intensity of the sunlight, thus improving the photovoltaic conversion rate.

a. Horizontal single axis tracker
The horizontal single axis tracker is mainly composed of: PV panel mount, horizontal rotating shaft, rotating driving mechanism, electric control system and central control system.
This tracking system is simple in structure, light in weight, easy to install, using mechanical linkage control, good reliability, cost-effective, modules above the bearing pedestal, which has a strong sand resistance ability, high fault identification ability, flexible reaction, compared with the traditional fixed angle installation, power generation can increase 15%-20%. Horizontal single axis tracker is suitable for areas with less than 30° latitude.

b. Tilt single axis tracker
The tilt single axis tracker is suitable for the areas with latitude above 35°. The system only needs only one set of driving device and controller to realize the automatic tracking of single array or multiple array at the same time. The unique linkage mode structure and the maintenance-free rotary bearing make it have the characteristics of reliable stability, low failure rate and low maintenance cost. Compared with the traditional fixed type, it can increase the generating capacity by 21%~35%.
Difference between horizontal and the tilt single axis tracker:
Due to its lack of inclination Angle in the south direction, the horizontal single axis tracker  has a poor reception ability when the solar altitude angle is low, which is especially obvious in high latitude areas. The power generation capacity of the horizontal single axis tracker in high latitude areas will be reduced, especially in winter, and the power generation capacity is even lower than that of the fixed support type.
The tilt single axis tracker has a certain inclined angle in the south direction, so the situation will be better than horizontal single axis tracker. But it still has its limitations, because south direction Angle, the oblique single shaft bracket as the growth of the rotation axis, the north is higher and higher off the ground, and the later can't do the post is too high, so also the tilt type can not make the axis as long as horizontal type, and can only be independent of each other, the cost and area occupied are also increased.

2. Dual axis tracker
Dual axis tracker, has the rotation axis with two directions. This allows the panels to track both the sun's azimuth and the sun's altitude. This keeps the panels perpendicular to the sunlight. The dual axis tracker moves by two rotation axes, which can track the change of azimuth and elevating angle of the sun at the same time. Theoretically, it can completely track the running track of the sun to achieve zero incidence angle. 
Dual axis tracker is suitable for areas above 35° latitude and power generation will be increased by 35-43%.

1. Horizontal single axis tracker, installation is simple, easy to expand capacity, large capacity, low cost, strong wind resistance, high economic performance, more suitable for low latitude area and high requirements on flat ground.
2. The installation capacity and tracking range of the tilt single axis tracker is affected by the environment, and also limited by the stroke of the mandrel jacking motor, good wind resistance, relatively simple installation and high cost performance. If installed on the slope, the advantages are more obvious.
3. Dual axis tracker, which has two independent power actuators, may causes trouble in equipment maintenance. The area needed is large and easily affected by the environment. Installation is relatively complex,  medium wind resistance, so the investment is relatively high. Dual axis tracker is suitable for areas with latitude above 40°. 4. Single axis tracker is easy to make linkage structure, thus reducing the cost of dynamic structure and control system. But dual axis tracker is difficult to get linked, the number of modules will be limited.
5. According to the different installation methods, the angle measured by single or dual axis tracker is also different. Dual axis tracker can measure both flip angle and pitch angle, but single axis tracker can only choose one to measure, flip angle or pitch angle.

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