Steven KwokPhotovoltaic (PV) systems are traditionally installed with a fixed orientation and tilt angle, designed to optimize the power output throughout the year. As the position of the sun changes in the sky due to the tilted axis of the earth and its orbit around the sun, the solar power production of the PV system may be decreased, which is where solar tracking systems come in handy.
Solar tracking systems are an important tool designed to keep power production for PV systems at their peak year-round. These tracking systems come with different degrees of movement, driving systems and more.
In this article, you will learn the basics of solar tracking systems, their different configurations, and relevant information that will help you determine if they are the right fit for you.
What are solar trackers and how do they work? Grasping the basics
Solar trackers upgrade PV systems by granting modules the capacity to modify the direction they are facing. This is achieved by installing one or more mechanical or electro-mechanical joints that introduce movement to the base of one or more modules. A solar panel tracker can either be categorized by their driving system or degree of movement.
Conventional PV systems are installed on a fixed orientation from the azimuth and a tilt angle. The optimal configuration requires facing the modules true south or 180º from the azimuth, with a tilt angle equal to the latitude of your location.
A solar tracking system makes it possible to expose modules perpendicularly to the sun year-round and throughout the day, increasing peak power production for the whole system. Since solar trackers are more costly, they are more common in industrial and utility-scale applications than they are in residential ones.
Implementing modern technology, solar tracking systems have become more robust and technologically complex. Solar trackers now include anemometers, solar sensors, GPS units, and other sensors that integrate with Geographical Information System (GIS) software. The smart sensors can track the weather and work hand-in-hand with solar tracking software that uses machine learning to predict cloud patterns, the position of the sun in the sky, and other weather-related events.
Degree of movement on solar trackers: Single-axis vs. Dual-axis
One of the main aspects used to categorize a solar tracker is its degree of movement. Solar tracking systems usually feature a single-axis or a dual-axis system.
Tilted Single-Axis Tracker (TSAT)
One of the most commonly used and lower-cost solar trackers available is the tilted single-axis tracker (TSAT). These solar trackers may be designed for horizontal or vertical axis movement, with the particular tracker required for each PV system varying on the geographical location where the modules are installed.
The horizontal axis solar tracker modifies the tilt angle of the PV module with the east-to-west movement, keeping the orientation constant throughout the day. These solar trackers are ideal for getting the best performance out of PV systems located in low latitude or tropical regions. In these locations, the days are shorter, and the sun reaches a higher position in the sky at noon.
The vertical axis solar tracker keeps a fixed tilted angle while using a north-to-south movement for the orientation to follow the sun throughout the day. The PV systems that will get the best performance out of vertical solar trackers are the ones installed in high latitude locations, where the days last longer during summer, but the sun does not reach that high of a position in the sky.
Dual-Axis Solar Tracker
The most versatile and powerful solar tracking systems in the market feature two degrees of movement, known as dual-axis solar trackers. A dual-axis solar tracker can tilt the angle of the module with an east-to-west horizontal movement and the orientation with a north-to-south vertical movement, following the sun with the PV modules throughout the day.
A solar panel tracking system can be useful for PV systems installed anywhere around the world. These systems are precise, but they also have a considerably higher price, which is why they are mostly used in solar thermal power plants and for concentrated photovoltaics.
Interesting variations of vertical axis trackers
Visionary architects around the world, working hand-in-hand with electrical engineers, have come up with highly interesting applications for vertical axis trackers. Instead of applying the typical single-axis tracker on a PV module, some housing designs take solar tracking to the next level by rotating the whole building where the PV modules are installed.
One of the prototypes is the Gemini House created by Roland Mosl in 1991. This Austrian design for a house portrays a cylindrical house that is constantly rotating, following the sun to expose a PV installation of 150 sq. meters.
A similar concept to the Gemini House was created by the architect Ralph Disch with the creation of The Heliotrope. The Heliotrope is an elevated house featuring a rooftop-mounted PV installation constantly exposed to the sun with the vertical-axis movement of the house. This zero-energy home also includes solar thermal pipes and can generate up to five times what the family consumes.
Another interesting concept is the Revolt House proposed by the Delft team. The Revolt House is a floating home that rotates on water, that while it is not specifically designed for PV applications, it is designed to track the sun and take advantage of solar radiation to heat the home in winter and cool it during summer, however, a PV system can be installed to take advantage of the already rotating home.
Solar tracker driving systems: Manual, passive and active solar trackers
The second most important aspect used to categorize a solar panel tracker is its driving system. This is the mechanism used to move the axis to adjust the position of the module. The driving system for solar trackers may be manual, passive or active.
Manual Solar Tracker
The manual solar panel tracking system is the most basic driving system. Solar trackers featuring this driving system include one or more mechanical joints used to adjust the position of the module, the number of moving parts varies if the solar tracker has a single-axis or a dual-axis.
Passive Solar Tracker
Passive solar trackers implement a low boiling point compress gas fluid for the actuator in charge of repositioning the module as a result of the unbalanced illumination. As the compressed gas fluid receives partial sunlight, it changes its density by expanding as it boils or contracting as it cools, varying the density and re-establishing the equilibrium in the mounting system.
Active Solar Tracker
Active solar trackers implement actuators that actively modify the position of the PV module on a single-axis or dual-axis. The actuators used for the driving system in active solar trackers may include an electric motor or a mechanical system comprised of hydraulic cylinders. These systems automatically move the modules to expose them directly to the sun with real-time tracking sensors.
Where are solar tracking systems installed?
Solar tracking systems are a great tool to improve the performance of a PV system, but they are not always suited for all applications. In this section, we explain where solar tracking systems are commonly installed.
Residential applications
The most advanced solar tracking systems are not suitable for residential applications because of the high acquisition cost and maintenance costs. Another reason for solar trackers not being used in residential applications is that most of these tracking devices are designed for ground-mounted PV installations, while most home PV systems are installed on the rooftop of the home.
While it is not common, homeowners can still acquire a solar tracker kit and use it to improve the performance of the PV system at their homes. Low-cost solar trackers can improve the performance of PV modules by up to 37%, but they are more economically feasible in locations where electricity is more expensive and the additional performance can provide great savings on electricity.
Dual-axis solar trackers may require almost twice the moving parts as single-axis ones. The high number of components translates into a higher cost for the dual-axis solar trackers compared to the single-axis ones. This is why it is recommended to install horizontal single-axis trackers in low-latitude locations and vertical single-axis ones in high-latitude locations, instead of going for dual-axis trackers.
Manual trackers with their low cost are also recommended for residential applications since they can be used to adjust modules at a 15-degree angle during winter to make up for the shifted position of the sun in the sky. Passive solar trackers also have a relatively low cost, which is why they are a viable option, while active solar trackers with their high cost do not represent an economically feasible option in most cases.
Commercial & industrial applications
Commercial, industrial, and utility-scale PV systems can greatly benefit from the implementation of solar panel tracking systems. The power increase that a large-scale PV installation can gain with solar trackers goes up to 45%, which is why tracking systems are common in highly profitable solar power plants.
Installing single-axis solar trackers on a solar power plant has proven to increase power production by 25% in some studies, while others show an increased performance of 40%. Dual-axis solar trackers can take those power gains by up to 45%, but some PV power plant investors tend to opt for single-axis solar trackers because they deliver a higher profit for their lower cost.
The driving system for large-scale PV installations usually varies between passive and active ones. Manual solar trackers represent a high operational cost, being economically feasible only in developing countries with lower labor costs. Passive and active solar trackers represent a better option in developed countries, but the specific system should be determined after a detailed analysis considering the Levelized Cost of Energy (LCOE) and the profitability considering the cost of the trackers and maintenance.
Pros & cons of solar trackers
Solar trackers can have different degrees of movement and driving systems, but overall they introduce many advantages to PV systems and represent only a few disadvantages. In this section, we introduce and analyze the most important pros and cons of solar trackers.
Pros
Solar power production is maximized throughout the day
Solar trackers expose PV modules perpendicularly to the sun or as close as possible, increasing the production of solar power in a PV system. This increases solar gains and performance of the system by 20% up to 45% depending on the type of solar tracker used.
Solar trackers adapt to all types of PV systems in all locations
One of the best pros of a solar panel tracker is that they have been heavily researched and provide suitable solutions for PV systems around the world. Depending on your location and available space, you might use different tracking solutions to improve the performance of your PV system.
PV systems with limited space can improve solar gains by up to 45%
In some cases, PV system owners may have enough resources but limited space to fit a solar array. In this case, investing in a solar tracking system may prove profitable by improving solar gains by as much as 45% when using dual-axis solar trackers.
Profitability is greatly increased in large-scale ground-mounted PV systems
Small-scale PV systems feature small gains when the cost of the solar tracker system is compared against the solar gains, but the profitability becomes more noticeable in large-scale ground-mounted PV installations. Installing the right solar panel tracking system will also increase solar gains while keeping the cost to a minimum.
Integration with solar tracker software
Solar tracking software can integrate with solar trackers, analyzing future weather and climate patterns to predict the power output of the modules. Gathered weather information can also be used for other multidisciplinary research purposes related to the weather.
Cons
More expensive than fixed mounting systems
The high cost of solar trackers is one of the main disadvantages compared to fixed mounting systems. In some cases, the cost is so high that implementing solar trackers can push the ROI a few years up.
Higher need for maintenance
Aside from a higher upfront cost, solar trackers also require regular maintenance. This not only introduces an additional task to be performed on the PV system but an additional cost to the LCOE.
What is the estimated cost of solar tracking systems? Are they feasible for residential applications?
Solar trackers can feature a wide price range considering the different driving systems and degrees of movement that can be used to design the tracker. Other factors, like the number of modules allocated per tracker, the design, the quality of the materials, and the manufacturer, can affect the retail price.
The cost for a single-axis solar tracker can be estimated at around $500, while a dual-axis solar tracker can pump the price up to around $1,000. Considering these high costs for the tracking system, adding solar trackers to a PV system could increase the price by 40% up to 100%.
PV systems in the U.S. have an average Return on Investment (ROI) of 10 years. While solar trackers can increase the performance of the PV system by around 40%, they could also increase the cost by around 40% and more, keeping the ROI at 10 years or more. In this particular case, installing solar trackers for a residential application would not seem economically feasible.
An alternative option would be designing and manufacturing a more affordable solar tracker. Among the available projects, some include manufacturing a dual-axis solar tracker using an Arduino, and another one designs a custom-made low-cost solar tracker priced at a little less than $150.
Foreword: Are solar trackers the right fit for your PV system?
The economic feasibility of a solar tracker should be analyzed considering the ROI, improved performance in the power output of the system, LCOE, and operation & maintenance (O&M) cost.
For commercial, industrial and utility-scale applications, solar trackers factored into the LCOE have proven to be a right fit for the PV system, increasing the performance and profitability of the system and making the investment worth it.
For residential applications, we recommend analyzing each particular case. Some locations with high electricity costs can take advantage of a solar panel tracking system, but on a general basis, they are not recommended since retail solar trackers cost a high penny and introduce an unnecessary maintenance requirement, proving to be more costly than profitable.
Analyzing the ROI of your PV system and looking for low-cost solar trackers, including DIY projects or solar tracker kits, could end up making solar trackers a right fit for you. Implementing affordable solar trackers into a PV system with solar gains of up to 40% could end up greatly reducing the ROI by a few years and even increasing the overall value of your PV system.
