What are Solar Trackers and How do Various Solar Trackers Work?
Fixed solar panels capture only a portion of the optimum energy from sunlight because the sun is not at the most efficient angle to the solar panels for most of the day. A way to ensure solar panels always directly face available sunlight is to use solar trackers.
A solar tracker is a mechanical device that tracks the position of the sun throughout the day by rotating or tilting an array of solar panels so as to capture maximum amount of solar energy. Consequently, solar panels equipped with solar trackers provide higher system output compared to fixed-tilt ground-mounted solar power systems.
Fun fact: The first solar tracking systems were installed on the solar panels of orbiting satellites.
On the other hand, a solar tracker system will likely cost more upfront than a fixed solar panel system. This is because a solar tracker is a more complex technology with more components.
The real question is: are solar trackers worth the investment? Read on to find out.
When you choose the right type of solar tracker for your project, higher energy efficiency offsets the initial higher costs. While certain solar trackers are most used in large commercial installations, there are types of solar trackers for residential and smaller-scale commercial use. Some argue that it is cheaper to install more solar panels to get better energy production; however, if you have limited rooftop space or real estate and that isn't possible or practical, a solar tracker system may be your best solution.
Solar power generates some 4% of the world's electricity, which may not seem like much. However, it is likely to increase as renewable solar power is seen as a way to combat climate change, with an expectation that 20% of the world's energy needs to be met by solar power by 2050. Wider adoption of solar trackers can play an instrumental role in attaining that goal, as solar trackers have much higher energy output than fixed solar systems because of their sun-tracking technology.
Solar trackers are either passive or active, which describes the mechanical system that tilts the solar panels.
Solar tracking systems are furthered classified as single- and dual-axis solar trackers. The sun moves across the sky from east to west, and solar trackers on single-axis systems rotate about a single point, turning either in unison, panel row by section or section by section. Dual-axis solar trackers rotate on both the X and Y axes, ensuring that solar panels follow the exact position of the sun all day, all year, resulting in the highest energy production.
In this article, you can learn about:
● How solar power and solar panels work
● How solar trackers increase solar panel output
● The way passive and active trackers differ
● Single-axis solar trackers and where they are used
● Dual-axis solar trackers and how they add increased efficiency
In addition, we also take a look at the:
● Advantages of solar trackers
● Future of solar tracker systems
How solar power and solar panels work
Solar power is generated one of two ways:
● Solar panels comprising a series of small photovoltaic cells, typically made of silicon, convert sunlight into electricity. As the solar panel generates an electric current, the energy flows through a series of wires to an inverter to convert direct current (DC) into the alternating current (AC) that lights and electrical appliances use.
● Concentrated solar power systems that use lenses or mirrors to concentrate sunlight heat conventional steam-driven turbines that create electricity.
Solar trackers could be included in both types of solar power systems; however, concentrated solar power is used for large power plants, while solar panels are installed for residential and commercial use. Our discussion here focuses on solar trackers used in solar panel systems.
How solar trackers increase solar panel output
Solar trackers increase solar panel output – single-axis solar trackers by up to 30% according to the National Renewable Energy Laboratory (NREL), while dual-axis solar trackers 50% to 70%, compared to same-sized fixed solar installations. This is a result of a rotating motion of the solar arrays which makes the panels follow the sun and collect more of its energy. Most single-axis tracking systems are set at a latitude angle, which means that they tilt in one direction to follow the sun and stay as close to facing the sun as possible. Dual-axis trackers, on the other hand, move on both east-west and north-south axes, which ensures maximum solar energy collection by keeping the solar panels perpendicular to the sun’s rays.
Increasing the output of solar panels reduces the number of solar panels needed for an installation to achieve the desired energy goal. For example, a solar tracker system with 1000 watts capacity has, under the right conditions, the same output as a fixed rooftop solar power system with 1450 watts capacity.
Consequently, by providing more energy per square foot, solar trackers require less installation space. Where space for a solar panel system is limited, solar trackers are an ideal choice.
Passive and active solar trackers
Solar trackers are either passive or active.
Passive solar trackers, an old technology that is seldom used today, use a liquid with a low boiling point. The liquid evaporates as it is exposed to solar radiation, causing an imbalance that tilts the solar panel towards the direction of the sun as it travels westward. As the sun moves back to the east and the sun rays lower, the solar panels cool and the evaporate returns to liquid form, thereby tilting back the solar panel.
Active solar trackers have a drive core with motors or hydraulic cylinders linked to either sensors that react to light from the sun or an algorithm-based tracking system which uses pre-programmed data like GPS coordinates of the sun's position which move the array with the solar panels towards the sunlight.
While active solar trackers are more complex and more expensive, they are far more reliable and popular than the older-technology passive solar trackers.
Single-axis solar trackers
Single-axis solar tracker solutions are increasingly the system of choice for utility-scale projects. According to Berkeley Lab, single-axis tracking systems accounted for 70% of utility-scale solar installations completed in 2018, leaving only 30% to fixed ground-mounted solar.
Single-axis solar trackers were originally intended to function like Venetian blinds, with solar panel rows moving in time together throughout the day. With consideration being given to tracking software for uneven light, strong wind conditions, and row and horizon shading, panel rows are now designed to compensate for diffused light, adverse weather, and row and horizon shading.
There are two types of single-axis solar trackers: centralized and decentralized. Centralized or distributed solar trackers use a single motor to drive a driveline between rows that move an entire panel group. Decentralized systems use one motor for each tracking row.
There are also single-axis solar trackers with motors on every rack set, allowing adjustment of the rows adjusted during installation and, in some cases, to track independently of neighboring modules.
Bifacial panels, which offer dual-sided solar production, are utilized by various racking systems and tracking algorithms to increase power output. Other single-axis trackers are built to accommodate modules in a two-in-portrait orientation.
A single-axis solar tracker with linked rows typically doesn't work as well on steep, undulating topographies where grading may be required. Certain models, however, can now compensate for uneven surfaces.
On cloud-covered days, direct sunlight doesn't reach the Earth's surface with strong beams — it is absorbed as diffused light — which implies a panel facing directly at the sun won't necessarily have the most output. Such events may indicate that solar panels are hung horizontally to capture the most diffused light.
When the weather is windy, solar trackers are programmed to stow the solar panel rows flat, which is their safest position. Modern solar trackers can compensate for heavier winds and, in some situations, system-level monitors can tell which panel rows are unaffected by wind conditions and allow them to continue moving.
There are a few maintenance challenges of single-axis solar tracker installations. Cleaning the solar panels and keeping the grass short underneath to prevent shading poses the same sort of maintenance requirement for solar trackers as for fixed ground-mount systems. For large utility-scale installations, manually cutting the grass under the solar panels is a labor intensive and expensive endeavor. Bringing in grazing animals for grass control is an emerging solution. Other maintenance needs of single-axis solar tracking systems are greasing their moving components annually and replace broken or underperforming panels as needed.
Dual-axis trackers
Because the rotational angle of the Earth around the sun is not the same all year, a dual-axis tracking system that is able to follow the exact and unique position of the sun 365 days has a greater energy yield than its single-axis counterpart. A dual-axis solar tracker generates 30 to 45 percent more energy than a same-sized single-axis solar tracking system, making it the most efficient solar power system of today.
Dual-axis solar trackers, sometimes known as two-axis solar trackers, are mounted on top of a single pole with a tracking technology that provides the increased range of motion and the precise sun-tracking of the installed panels. Dual-axis solar trackers often sit low, just a few feet off the ground, which makes fencing around the installation necessary.
Elevated dual-axis solar trackers, however, carry their solar arrays atop a 20 feet pole, and with their high ground clearance, are optimal for projects where continued use of the grounds below is an important consideration. No fencing is necessary around these 30-foot mechanical sunflowers which makes them ideal for farms, parking lots, fields, school yards, etc.
Cleaning the panels of dual-axis solar trackers that sit low to the ground and cutting the grass underneath means a significant maintenance task just like in the case of single-axis solar trackers. Elevated dual-axis trackers, however, are free from such challenges. Ground level dust and grime does not collect on the panels because of their elevated position and the grass can easily be cut with any type and size of lawnmower.
Tip: Discover more about dual-axis solar trackers and elevated solar tracking systems.
Advantages of solar trackers
There are more than enough advantages that make solar trackers worthy of consideration.
While solar trackers are not cheap, neither are solar panels. In fact, solar panel prices are rising due to both increasing demand as well as supply chain issues arising during the pandemic. The increased efficiency of solar trackers allows you to reduce the number of solar panels needed for producing the desired amount of energy.
The increased efficiency of solar trackers could help reduce overall energy costs as well. Not only are you drawing less power from the utility's electrical grid, and consequently lowering your energy bill, but you can also take advantage of time of use billing. This is a practice where many utilities charge more during certain times of day of peak usage. By switching to solar power during those times, and at times when a solar tracker derives the most energy output, you can further reduce your utility bill.
As a business, you can also offset rising solar tracker installation costs by taking advantage of the various tax credits and utility incentives offered by federal, state, and local governments.
Consumers in warmer climates use more electricity to cool during the summer than to heat in the winter; solar trackers take fuller advantage of longer summer days and longer sunlight by increasing energy production. In colder climates, where higher energy expenditure occurs during the winter with less sunlight, solar trackers make the most use of available sun, reducing the need for additional solar panels.
The future looks bright for solar trackers
Tracking system manufacturers have been making great improvements to their systems in recent years, including the development of monitoring software for preventative maintenance and improved angles for higher energy yield. Installers continue to advance tracking technology to maximizing the output of solar panel installations.
Stracker Solar is a leader and pioneer in the solar industry.
Find out more about the Stracker – the unique, elevated dual-axis solar tracker that can produce maximum solar energy with the smallest footprint.
As the solar power industry continues to grow and mature, cost-efficiencies and technological improvements grow and mature as well. If there isn't sufficient room for the number of solar panels required by a fixed rooftop or ground-mounted system to meet your energy goal, solar trackers can make the project feasible and profitable.
Arguably, installing solar trackers can also significantly increase property value (especially in case of elevated dual-axis solar trackers that allow full use of the grounds below the panels) while also contributing to local electrical infrastructure and power sustainability.
As with any major investment, research into individual circumstances, location and budget is required to help weigh the pros and cons of a solar panel system in general and whether solar trackers are worth the initial extra investment in your case. The recommended route is always to consult a reputable and experienced solar company and let them design and quote the solar power system that would best meet your energy goals.
If you're in Oregon or Northern California and are looking to install a future-proof solar power system for your business, contact us for expert help in designing and implementing your new solar solution.