A photovoltaic solar tracker is a mechanical device to rotate PV panels to achieve an optimal angle concerning the sun's rays.
The greater the perpendicular alignment with the sun's rays, the greater the efficiency. For this reason, installing solar panels with a photovoltaic tracker improves the performance of the electrical energy output.
PV modules mounted on a tracker system are usually arranged in a single panel. In this way, the number of photovoltaic trackers in solar installations can be reduced.
These types of systems are also used in solar thermal power plants. In this case, the solar light follower panel is oriented to reflect all the solar radiation at one point and heat the heat transfer fluid.
There are three types of solar trackers:
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Manual trackers are ground-mount structures that a physical person can manipulate to change the solar panels' tilt.
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Active trackers rotate PV panels with the help of an external power supply.
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Passive trackers solar systems rotate solar panels without any external energy source.
Advantages and disadvantages of solar tracking system
Solar projects with a tracker entail the following advantages and disadvantages:
Solar trackers disadvantages
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The appearance of mechanical problems due to wear and tear over time.
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Electronic mechanisms and sensors are exposed to harsh weather conditions for at least 20 years and will likely need to be replaced.
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Major maintenance of this type of solar energy facility.
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The initial solar installation cost is higher, although it will be compensated by getting a higher solar power performance.
Solar trackers advantages:
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Solar cells have a lower sensitivity of the photovoltaic effect to dust deposited on the surface, thanks to the better angle of incidence of the Sun's radiation.
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The electricity production is higher due to the better performance of the solar panels.
Manual solar trackers
Manual trackers require someone to physically adjust the panels at different times during the day to track the sun.
This system is not always practical as you need someone to constantly monitor the sun and change the position of the solar panel system. However, it simplifies the structure - thus, it is cheaper - and it allows us to increase the productivity of our solar power system.
Active trackers
Active trackers rely on hydraulic motors or cylinders to change position. The active tracker motors will move the photovoltaic panels to face the sun. While this is more convenient than manual crawlers, the engine moving parts could easily break. This situation could lead to higher maintenance costs over the system's life.
The energy needed can also be supplied by the same PV system.
From there, solar trackers can be further classified based on the direction they are moving. A solar tracker can be:
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Single axis tracker
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Dual axis tracker
Single axis solar tracker
There are four types of single-axis tracking systems which differ slightly in their strategies :
X-axis trackers
Tilt followers are the simplest to make. The photovoltaic panels face south and rotate around the east-west axis.
The solar panel is raised or lowered (usually manually twice a year) towards the horizon so that the angle to the ground is the most optimal depending on the season.
Y axis trackers
Y-axis trackers aim to follow the sun across the sky on their daily journey at any time of the year.
In this case, the axis of rotation is north-south, while the height of the Sun above the horizon is ignored. These trackers are particularly suitable for low-latitude countries, where the sun's path is, on average, wider during the year.
Z axis trackers
Azimuth solar trackers have one degree of freedom with a zenith - nadir axis. To achieve this, the panel is mounted on a servo-assisted swivel base, flush with the ground. The resulting increase in electricity production is close to 25%.
Polar axis trackers
Polar axis trackers move on a single axis tilted relative to the ground and nearly parallel to the earth's axis of rotation. This axis is similar to where the sun traces its path in the sky.
Therefore, this rotation system manages to keep the panel perpendicular to the Sun throughout the day. In addition, it provides the maximum efficiency that can be obtained with a single axis of rotation.
Dual axis trackers
The most sophisticated solar trackers have two degrees of freedom so that they can rotate around two axes.
A two-axis photovoltaic tracker aims to perfectly align the orthogonal photovoltaic panels with the radiation in real-time. The cheapest way is by mounting one follower attached to another.
With these solar trackers, electricity production increases up to 40% compared to fixed panels.
Passive solar trackers
Passive trackers can also track the sun’s radiation, but they do not need any external power supply in this case.
The energy to drive passive trackers comes from the Sun. They contain a liquid with a low boiling point that solar radiation converts into gas, causing an expansion. Therefore, the liquid expansion exerts a force, and the tilt system becomes unbalanced.
This imbalance causes the panels to tilt in the direction of the sun's rays.
The actuators are positioned strategically so that they expand differentially depending on the place where we want to exert the force.
On this site, see a comparison between active and passive solar trackers.
