Solar tracking systems or trackers are devices used for orienting PV systems toward the sun to maximize the amount of energy collected throughout daylight hours. Solar trackers help to improve overall system performance and economic payback.
Tracking technology enables solar modules to remain in the best position to collect energy from the sun, thereby increasing the electricity production compared to modules that are installed at a fixed position.
According to Andy Kerr writer and owner of the conservation organization, The Larch Company, a PV system’s output can be increased up to 40% by using a tracking system, as it maintains a consistent direct exposure between sunlight and the module.
Although fixing modules at an optimum angle can improve efficiency compared to panels that are mounted flat, trackers often deliver the ultimate efficiency. By sensing the position of the sun, most trackers can adjust horizontally and vertically throughout the season. By constantly aligning with the orientation of the sun, the system will often deliver better performance. To take advantage of this increase in performance many utility-based installations utilize this technology.
There are two basic types of tracker system – Single-Axis Trackers and Double-Axis Trackers
Single-axis trackers simply rotate about one axis, azimuthally moving from east to west while double-axis trackers rotate both east to west and vertically over the course of a day. David Appleyard, Chief Editor of the Renewable Energy World Magazine states that single-axis trackers can increase system performance by between 27%–32% and double-axis trackers can increase system performance by between 35%–40% when compared to fixed panels.
Although double-axis trackers have more output, manufacturers of single-axis state that the return on investment from these systems is not justified because of additional equipment, installation, permitting and on-going maintenance costs. Since double-axis systems are more complex and contain more moving parts, the risk of malfunction is also higher.
There are also active trackers and passive trackers. Active trackers are the ones that use motors, gear trains or hydraulics to move the module. These are very precise trackers but they also consume energy. Passive trackers use a low boiling point compressed fluid to move the system. These systems do not consume any energy as they are powered by solar heat creating gas pressure in the system. These are however, less precise than active trackers.
There is also a type of tracking actuator that responds to the motion of the earth relative to the sun. This system uses a mechanical geared system that rotates the module at an equal speed in the opposite direction. Thus the system will complete one revolution in a day.
Advantages & Disadvantages
In specific applications, tracking systems have proven to be an economic option that can result in enhanced system performance. Support measures like feed-in tariffs that reward PV produces per kilowatt-hour conveyed to the grid and the previously high prices of silicon-based PV modules were underlying factors that drove investment in tracking technology.
However, for a tracker to be an economic advantage, the energy harvested by the system should result in an economic performance benefit greater than the added cost of the tracking system, installation and ongoing maintenance. In addition, tracking systems require more space to enable axis movement and avoid shading one another as they move across the axis, often resulting in less system density and reducing overall installation output.
Average operating life for tracking systems are approximately twenty years with higher operations and maintenance cost, compared to the fixed systems. Over a twenty year period, operations and maintenance costs alone have significant impact overall financial performance over the life of the system.
With the reduction of silicon based PV panel costs and with investors continually looking to maximize their return on investment, the economics of continued growth in the tracking systems market segment is uncertain. Installing trackers requires higher capital costs and ongoing operations and maintenance.
Despite these drawbacks, one cannot ignore the production gains of installing tracking technology. Falling prices of silicon-based modules in response to expanded production also means less overall system cost involved in installing trackers.
In summary, tracking systems have their place. Given needs of the project and investors, and other factors such as land cost and deployment density, each project offers a unique opportunity to design a solution that will deliver the optimal solution.