A Comparison of Fixed-Tilt Racking and Single-Axis Trackers for Large Solar Projects
Have you ever wanted a detailed summary of the pros and cons of fixed-tilt solar racking and solar trackers?
In this article, we will highlight differences between fixed-tilt racking systems and solar trackers from all aspects including design, cost, and feasibility. How to determine which racking system works best for your site? Is there enough space to install the system? What are the ongoing maintenance requirements for each? Let’s dive right into the details beginning with the cost.
Revenue: increased generation from the solar PV tracker
Comparing efficiency between fixed-tilt racking systems versus single-axis trackers
Simply put, a single-axis tracker allows for more direct sunlight, producing more energy than a fixed-tilt rack. This makes the single-axis tracker more effective at absorbing energy as the system can track the sun’s movements throughout the day. Trackers increase the production of a site by roughly 15% to 25%, compared to fixed-tilt systems1. Multiple variables influence this measurement such as the amount of sun exposure, climate conditions, land costs, installation and maintenance fees, number of panels, etc. However, when comparing the two systems, the single-axis tracker is optimized to produce more energy, leading to a higher financial rate of return.
Solar Racking Costs of Fixed versus Trackers: System, Construction, and Maintenance
While production increases with single-axis tracker systems can be significant, all the additional costs of installing and maintaining a tracker should also be considered. For example, we know that capital costs for fixed-tilt systems are generally lower than that of a solar tracker, but so is their overall performance. As a result, when combining both the fixed costs and variable costs into a single measurement, the LCOE for a single-axis tracking system, in many cases, will be lower than the fixed-tilt system.
As mentioned, the absolute cost for fixed-tilt racking systems tends to run lower than single-axis trackers. A 2020 price benchmark from National Renewable Energy Laboratory (NREL) listed the average price in U.S. dollars for the fixed-tilt utility-scale system at $0.94/WDC and the single-axis tracker at $1.01/WDC[1]. For a 7.5 MWDC sized system, that could mean a difference of $525,000 for the installed costs.
You might notice that there are fewer long-term operational costs for fixed-tilt racking systems because they have no moving parts of the tracker system and don’t require the associated electronics and drivetrain. Both types of systems require regular maintenance. This includes vegetation management, snow removal, and cleaning requirements[2]. Single-axis tracking systems, however, require additional specialized professional maintenance, which tends to drive the cost up.
Vegetation maintenance for solar energy systems
The vegetation must be regularly trimmed for both kinds of systems as they may cause shading, or with single-axis trackers specifically, may interfere with their drivetrain. Vegetation maintenance includes mowing, trimming, and tree removal, and is calculated by cost per acre of the site area. In some cases, the cost can be ameliorated with the optimized design of the equipment and planting only low-growth vegetation. This would ensure that there is enough clearance between the panels for the mowing equipment to access. For snowy regions, snow removal needs to be added to the maintenance routine. Snow removal from the panels, the alleys, and access roads are also necessary for fixed-tilt racking but extremely critical for trackers, as this prevents the mechanical drive from becoming damaged from heavy snowbanks.
Cleaning and maintenance costs for fixed-tilt versus single-axis tracker
Cleaning at regular intervals or conditioned-based may help to maintain the energy output of the PV array and may prevent localized hot-spot failures. There may be a fixed fee and then a per-unit area cost for labor and materials. On the downside, annual losses can range from 4.3% to 7.5% from soiling. However, in areas with heavy sources of dust, pollen, and or bird droppings, you may see the costs leaning towards the higher side.
Single-axis trackers require additional maintenance for the moving parts and the associated system to remain effective. These items include electrical, controls, rack and actuator, monitoring, and battery replacement. For example, frequent checks of the UPS backup power system must be completed to ensure the system is operational in the case there is a power outage. Snow depth censors and wind censors should also be checked to make sure they are in good functioning condition. Any malfunctioning on these parts could result in the solar tracker failing.
Opting for single-axis trackers means you will need more space
Another variable to consider is how much land is being used. Single-axis trackers tend to take up more space because the rows are typically placed further apart to avoid shading. However, being spaced apart means more land area is being used up, thereby driving up land costs for developers. On average, fixed-tilt systems will require four to five acres per MW and a single-axis tracking system will use about four to seven acres per MW3.
The good news is that even with the additional maintenance and space for single-axis solar trackers, it’s likely you will need fewer panels to meet your solar power demands. So, you can maximize your energy production but might see higher installation and maintenance costs.
Solar Racking System Design
Fixed-tilt systems are ideal for challenging topographies
As cities and states begin to adopt renewable energy as a measure to combat climate change, some solar projects will be developed on sites that aren’t considered ideal for installation. For example, these include sites with rolling hills or slopes, obstructions such as trees, or other challenging geotechnical conditions. In these scenarios, fixed-tilt mounting systems perform the best in varying topographies, as they can be installed on challenging slopes and rolling terrains.
Loose soil, rocks, buried organics, and other obstructions can all add to the complexity of installing a solar system’s foundation. For fixed-tilt systems, the foundation is easily optimized and well-suited for these complex geotechnical conditions, withstanding even the harshest weather conditions.
Solar tracking systems perform well in less challenging conditions
While solar tracking systems can yield a higher return on energy production, their foundation design has to account for the additional loads. Single-axis trackers tend to succeed best where soil conditions and topographies are less challenging. Generally, terrain that is relatively flat is ideal for single-axis tracker systems. These considerations should be evaluated along with production modeling to ensure the best project outcome.
Shading affects solar panel performance
Finally, one last item to consider is shading. When designing the solar project, panel spacing should be taken into consideration. With the single-axis tracker system, you will need sufficient space in between the solar arrays to prevent the panels from shading one another. This can slow down energy absorption. Furthermore, you need more square footage when planning to install a single-axis tracker site to achieve the same installed DC capacity that a fixed system would provide.
Assessing your return on investment of your solar racking and mounting system
In short, fixed-tilt systems, although they require less installation and maintenance fees, produce less energy over time. Alternatively, single-axis trackers are able to produce more energy but require higher maintenance and installation costs, and a larger area to install. When developing larger solar sites, it’s important to evaluate these factors thoroughly to ensure the suitability of the system to the site, as well as to assess which system makes the best return on investment.
If you have any questions, please contact Sales Director at Polar Racking.
Phone: 416-860-6722
Email: sales@polarracking.com
References
1 S.P.W. (2018, February 19). Fixed-tilt vs. tracker: Why a one-size-fits-all approach can limit solar production. Retrieved November 4, 2021, from https://www.solarpowerworldonline.com/2018/02/fixed-tilt-vs-tracker-one-size-fits-approach-can-limit-solar-production/
2 Rowley, A. (2021, August 29). Fixed Racking vs. Tracker for Commercial Solar Projects. Retrieved November 3, 2021, from https://www.solarfeeds.com/mag/fixed-racking-vs-tracker-for-commercial-solar-projects/#What_Are_Solar_Trackers
3 S. (2012, November 28). Solar Balance-of-System: To Track or Not to Track, Part I. Retrieved November 4, 2021, from https://www.greentechmedia.com/articles/read/solar-balance-of-system-to-track-or-not-to-track-part-i
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