Solar Trackers Information
Figure 1: With solar trackers, optimal sun exposure can be maintained regardless of time of day or seasonality. Source: Pixabay
For components that rely on solar exposure to perform as expected, solar trackers keep these components in line with the sun throughout the day and the time of year. The Earth’s rotation causes the sun to traverse the sky, changing the incidence of sunlight at any given position. Additionally, the Earth tilts on its axis throughout the year, which further changes the angle of incidence. With solar trackers, optimal sun exposure can be maintained regardless of time of day or seasonality.
Theory of Operation
Solar trackers maximize the output of solar panels and other solar equipment by maintaining proper orientation between the panel and the sun. Solar panels and related devices are most effective when the panel is completely perpendicular, or normal, to the angle of the light rays shining onto the panel. Solar panels produce more energy when this angle is optimized.
Figure 2: Angle of incidence. Source: Public domain
Due to the rotation of the Earth and the tilt of the Earth’s axis, the sun appears to move throughout the sky. This change in the sun’s position also changes the angles of the rays of light as they shine onto the Earth. These angles change not only throughout the day but throughout the year as well.
Figure 3: Analemma, solar position at the same time each day, explains why earliest sunset and latest sunrise is at different dates. Source: Daniel Rüdisser/ CC BY 4.0
Because the position of the sun in the sky is changing, solar trackers are required to constantly adjust the position and angle of the solar panel to optimize the angle of incidence. Solar trackers track the sun and move the solar panel in one or two axes so that the solar panel catches more light and produces more energy.
Solar trackers typically use one or more sensors, such as light sensors or GPS receivers, to determine the sun's position. The sensors then send signals to a control system, which moves the solar panels accordingly. The control system may use motors, gears, or other mechanisms to adjust the angle of the solar panels in one or two axes. Some solar trackers use a combination of sensors and algorithms to predict the sun's position based on the time of day and the location of the solar panel array.
This combination of sensors, drives, and solar panels results in much more power output than a static setup. Dual-axis solar tracking systems can produce as much as 30% to 45% more energy than a similar-sized static solar panel system.
Figure 4: Geonica SEMS-PV Station including solar irradiance sensors and meteorological sensors in a Photovoltaic Solar Plant. Source: Geonica/CC BY-SA 4.0
Specifications
Solar trackers have become much more widespread as the cost to add them to solar installations has fallen. Key specifications to look for when comparing solar trackers include:
Number of Axes
The most common type of solar tracker is the single-axis version. Single-axis trackers track the sun as it traverses from east to west. Dual-axis solar trackers allow the panels to also track the sun as the Earth’s tilt changes throughout the year. Dual-axis installations require higher mounting heights due to the greater number of angles the panels must move through. The range of angles that a tracker can rotate through is another important characteristic.
Motor Control
For single-axis solar trackers, motor control can be either centralized or decentralized. Centralized motors can operate many rows of panels through linkages and racking. Decentralized trackers operate independently and can be easier to maintain due to the independence of each system, but at a higher cost.
Durability
Exposed to the elements, solar trackers must be able to withstand rain, solar exposure, wind, and high temperatures. Excessive maintenance from low durability can keep solar trackers from making economic sense.
Communication System
Some solar tracking systems have communication capabilities that allow for remote monitoring and control. These systems can enhance the flexibility and functionality of solar installations.
Height Requirements
Because solar trackers must be able to move the solar panels around in space, solar trackers will typically have a minimum height requirement. Installations below this height requirement will have less functionality and risk damaging the solar panels.
Power Consumption
Solar trackers themselves consume power to operate. Understanding the power requirements ensure that the solar panel installation is still able to operate as designed.
Figure 5: Solar panels. Source: Pixabay
Types
Solar trackers come in two main varieties: single-axis and dual-axis.
Single-axis Horizontal
These trackers move the solar panel in a single axis (east to west) and have a horizontal orientation. They are the most common type of solar tracker and can increase energy output by 25% to 35% compared to a fixed solar panel.
Single-axis Vertical
These trackers move the solar panel in a single axis (north to south) and have a vertical orientation. They are used primarily in high-latitude regions where the sun's path is more vertical and can increase energy output by 20% to 30%.
Dual-axis
A combination of the two prior types of solar trackers, these trackers move the solar panel in two axes (east to west and north to south) and have a more complex design. They can increase energy output by up to 45% compared to a fixed solar panel and are used primarily in areas with high solar radiation to maximize output.
Figure 6: Solar trackers can use algorithms to predict the best position for the panels or can use sensors to actively measure the best orientation for the panels. Source: Ra Boe/CC BY-SA 3.0
Features
Solar trackers have greatly advanced in recent years, adding much more functionality than older models. Some of the most important features to look for include:
Tracking Method
Solar trackers can use algorithms to predict the best position for the panels or can use sensors to actively measure the best orientation for the panels. Sensors used in solar trackers can be optical or electronic and ensure that the solar panels are positioned in the best orientation for maximum energy output.
Motor Power
Motors for solar trackers can be both electric and hydraulic. Electric motors are common and can be maintained and replaced easily. Hydraulic motors are less common but can be found on larger installations.
Panel Size
Solar trackers are designed to hold different quantities of solar panels. Larger solar trackers can hold more panels but may require more space in order to move the panels around.
Adjustability
To hold different quantities and sizes of solar panels, solar trackers must be adjustable. Adjustability for how the solar tracker is mounted also helps the system trackers to be easier to deploy.
Figure 7: Solar trackers are fairly simple to manufacture. Source: Parucom/CC BY-SA 4.0
Manufacture
Solar trackers are fairly simple to manufacture and consist of three main assemblies: the frame, the control system, and the motor or actuator.
Solar trackers must hold a heavy load and have to resist wind loads that can push against the solar panels. The frame is typically constructed from steel, aluminum, or composite materials. These materials are cut, machined, welded, and bolted together to form the shape of the frame.
Attached to the frame is the motor or actuator. The frame must be able to rotate on one or two axes throughout the designed angle range. The electric or hydraulic actuators are used to move the frame throughout the angle range. To make the solar tracker intelligent, the sensors and control system are added on to be able to track the sun. The control system will generate the commands to control the electric motor or hydraulic actuator.
Once the solar tracker is fully assembled, the system must be calibrated and tested. The calibration ensures that the physical solar tracker moves just as the control system intends for it to move.
Figure 8: Solar panels installed in residential installations can benefit from using solar trackers. Source: Parucom/CC BY-SA 4.0
Applications
Because the Earth rotates about the sun, solar trackers increase the output for any solar installation. Any application where solar power is generated will receive higher outputs with a solar tracker. Specific applications for solar trackers include:
Residential Installations
Solar panels installed in residential installations can benefit from using solar trackers. Because residents typically want to install as few panels as required. Solar trackers help to boost the output, allowing fewer solar panels to be required.
Solar Power Plants
Solar trackers are often used in large-scale solar power plants, where they can be mounted on single-axis or dual-axis tracking systems. These power plants may be located in remote or sunny areas, where they can generate significant amounts of electricity for the grid.
Commercial and Industrial Installations
Large-scale solar energy systems used in commercial and industrial settings can also benefit from solar trackers. These systems may include rooftop installations, ground-mounted systems, or solar canopies.
Agriculture and Farming
Solar trackers can also be used in agriculture and farming applications, such as greenhouse farming or irrigation systems. They can help reduce energy costs and increase crop yields by optimizing energy output.
Water Treatment Facilities
Solar trackers can be used in water treatment facilities to power pumps and other equipment. They can help reduce energy costs and increase efficiency in water treatment processes.
Figure 9: Horizontal single axis trackers solar Installation near Winters, California. Source: Public domain
Standards
Solar trackers play an important role and require strict adherence to safety and reliability. Common standards that apply to solar trackers include:
- International Electrotechnical Commission (IEC) 62817
- Underwriters Laboratories (UL) 3703
- Underwriters Laboratories (UL) 2703
- National Fire Protection Association (NFPA)
These standards specify the requirements and test methods for solar trackers, including safety requirements and performance characteristics. Other topics covered by these standards include wind loads, mechanical design, control systems, and electrical safety.