Trackers thaw solar freeze

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Installing a single-axis solar tracker is now no more than five percent more expensive than a fixed tilt system, yet the increase in energy generated is about 25%, producing a 20% gain just by following the sun. The many advantages brought by tracker technology mean that solar PV can now be installed at locations with less than optimal weather conditions. “We have many installations in cold climates and we see those numbers increase monthly,” says Dan Shugar, CEO of NEXTracker, based in Fremont, California.

Morning and afternoon gains

A key part of the economic advantage of a tracker is cost avoidance during utility rate peak periods, particularly with time-of-use (TOU) rates in effect. This ability leverages the value of the tracker during these higher-cost periods, cropping the total utility bill. “An advantage of the tracker system is its period of production, and the shape of its homogeneous daily power production curve,” notes Laurent Sarrade, Product Management Director at Exosun, based in Martillac, France. “Production is stable throughout the day with a maximum output 80% of the day,contrary to the classic Gaussian-shaped curve of a fixed-tilt installation, which includes a power peak at midday.” The Exotrack HZ also allows the capture of more sunlight when the sun is low in the sky, thus producing power earlier in the morning and later into the evening. “This results in 58% more energy output during those periods, a major benefit for our clients,” Sarrade observes.
Others agree: “NEXTracker’s single-axis tracker offers a better match to utility load, time of use multipliers, and customer peaks. NEXTracker’s +/- 60 degree rotation (versus a standard tracker rotation of +/- 45 degrees) is what enables these benefits, due to further broadening of the shoulder of the generation profile,” says Shugar.

Similar footprint

Compared with early tracker designs, where extra space was required to avoid self-shading problems, modern trackers are on a par with fixed-tilt installations in terms of land footprint. “NEXTracker’s system generates more electricity in roughly the same amount of space needed for fixed-tilt systems, making them ideal for optimizing land use,” says Shugar. Since tracker arrays are being designed in smaller modular layouts, the technology can also be adopted for terrain with challenging slopes or obstacles.

O&M costs higher for trackers

According to a recent study by French tracker manufacturer Exosun, the operation and maintenance costs associated with trackers may be 10% to 20% higher than with fixed arrays. However, their estimate is based on only five years of portfolio operation, so a longer-term study will tell more. Since annual O&M costs are less than one percent of capital expenditures for installation, this slight additional cost is readily absorbed within the 20% energy gain the technology presents.
Exosun notes that their tracker has 510 electromechanical items to maintain in a typical 100 MW installation, but that their systems also have few failures: The availability level of the company’s Exotrax HZ is 99.98%, they say. Exosun not only offers full O&M training for customers – the company offers complete O&M as a service. As such, a tracker company that also provides O&M has a high stake in balancing optimal O&M and optimal generation. “Tracking performance and reliability, as well as easy maintenance are critical success factors to make PV tracker projects even more profitable,” notes Sarrade.

Lower tracker costs, faster ROI

The tracker energy gain also has the effect of reducing the levelized cost of energy (LCOE), while increasing the investment rate of return (IRR) and improving other financial cost perspectives. “We see LCOE for most tracker projects as 15% lower than a fixed tilt,” says Shugar. The IRR and ROI improvements may seem less dramatic, but can be critical to a decision on installing a tracker. “Owners usually enjoy several percentage points on IRR as well. As a result, trackers have become the de facto standard for large power plants,” Shugar confirms.
Higher IRR also makes commercial and industrial adoption of trackers a far more likely prospect. “The main result of the economic boost from trackers is that if IRR was 9% without tracking, then with tracking, it goes up to 11%”, Bill Gross, Founder and CEO of Edisun Microgrids, of Pasadena, California observes. “We can get up into the mid-teens of leveraged IRR, making trackers a cost effective use of investment capital, and opening up the tracker option to a lot of companies that can’t make that return from their normal business now”, he adds. “This will make trackers attractive to a lot more businesses soon, perhaps even sleepy ones,” he anticipates.
Similarly, while PPA or lease terms for fixed-tilt solar may have seemed too long for some C&I customers to tolerate, a shorter purchase term might make a deal work, such as “if payback (ROI) was 12 years, and now it’s 10 years, because of the additional energy generation,” Gross adds. Edisun recently launched a dual-axis tracker for the commercial and industrial flat roof segment; officials at the company have been involved in single-axis tracker development in the past. Dual-axis trackers can yield up to 15% more energy than xAdvertisementa single-axis tracker, at a cost increase over single-axis trackers that is a fraction of the additional energy gain.

Geographic market expands with lower costs

Most of the geographic focus of the solar tracker industry to date has been confined to regions of the world where insolation is at around 2,000 kWh per square meter. This correlates with the dark orange areas on a standard annual global insolation map (see map above right). Now that the 20% superior tracker performance and total economics have been well proven, customers in areas where insolation is up to 20% lower might choose a tracker in order to lower their energy cost. Areas of the global map ranging from light orange down to dark yellow, for example, represent the potential market where trackers could soon be viable, in the portion of the world with at least 1,600 kWh per square meter of insolation.
Thus, as well as from Sub-Saharan Africa, the Middle East, much of Australia, Chile and Mexico, where insolation is 2,000 kWh or above, there appears to be an equal portion of the globe with at least 1,600 kWh of insolation.
At San Antonio, Texas-based Sun Action Trackers (SAT), Ronald Hardin, the company’s Business Development Manager says, “I’ve seen single-axis production increases over fixed from 12% to 25%, depending on where the system is installed.” Other tracker makers are experiencing the same sort of geographic market opening. “We’re experiencing a lot of demand in colder, snowy climates and the Southeast where trackers have long been dismissed”, notes Shugar. “With additional competition as the added cost for trackers (over fixed-tilt) continues to go down, they are making lots of sense beyond the Southwest.” SAT, too, has seen increasing demand across new isobar thresholds. “We have many clients as far north as Canada that have been ordering both single and dual-axis trackers. Since trackers are a decision driven by developers and owners. we rely on them to make an educated decision that best fits their situation,” notes Hardin.
Because the ROI on a tracker can be up to 20% faster, hosts located in a lower insolation area may be able to justify a tracker installation more easily than a fixed-tilt solar installation, which might take too many years to pay back from a financial viewpoint.

Sensing technology aids performance

One capability of some tracker designs is real-time alignment of the table toward the brightest point in the sky. “Our PST-1AX6 follows the sun at its highest point of irradiance, regardless of the weather, to provide the highest possible level of energy production,” says Hardin. “On a sunny day, real-time orientation is perpendicular to the sun at any time of the day, capturing the maximum power, which increases energy production. Unlike astronomical tracking, this real time sensing technology does not waste energy,” he notes. While astronomical algorithms predict the optimal orientation for full sun, obscuring factors like clouds can affect what an optimal angle may be.
The bonus diffused light capture can be critical to performance. “On a partially cloudy day, the clouds create diffused light, but there is also a direct beam component. Due to the contribution from diffused light, the optimal position of the tracker is not always directly facing the sun,” Hardin explains. “An astronomical tracker will continuously move in line with its predetermined programming and not take any of the above into consideration. The benefit of real-time light tracking is unbeatable and ideal for energy production”.

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