Tracking systems are already innovative. They track the sun rather than keeping solar panels in a fixed position. Many single-axis trackers claim at least a 25% performance gain over fixed-tilt systems, and developers still think there is room for improvement. A number of brands are exploring ways to improve backtracking (adjusting panel orientation to limit row-to-row shading at various times of the day) and accept more diffused light when cloud cover may prevent a direct sunlight path to the panels. These small tweaks would only increase energy gain by another few percentage points, but every bit is a bonus for traditional tracking companies and their customers.
“It’s nice to see innovation coming out of a company that [makes a sophisticated racking system],” said Dustin Shively, director of engineering at Clēnera, a U.S. solar developer that has installed many tracking systems. “It would be easy for them to say they want to make a modest margin and that’s enough. But it’s always, ‘How can we make things better and how can we optimize?’”
Shively is specifically referencing NEXTracker, a decentralized tracker manufacturer that holds the largest share of the global tracking market. The company released its TrueCapture self-adjusting tracker control system in July 2017 that claims another 2 to 6% energy gain through continuous optimization of individual rows of panels in response to site features and weather conditions. Clēnera was one of the first large-scale solar developers to implement the new technology on its tracking installations.
“The single-axis tracker algorithm has been unchained since the 1990s. You know where the sun rises and what tracking profile you should have,” Shively said. “NEXTracker thought it was better to manipulate each row instead of using one profile across the whole site. Let’s move rows independently to avoid shading on rolling terrain. With diffused light scenarios, when it’s cloudy, you don’t want to point at the sun, you want to point flat. It’s not an obvious solution, but it turned out to be true. That’s another method [NEXTracker] employed to change the single-axis algorithm to make more energy.”
NEXTracker is not the first company to test out different backtracking algorithms to adapt to uneven terrains, but it was the first to make a big play into capturing more diffused light. Greg Beardsworth, director of product management at NEXTracker, said finding ways to squeeze out more energy during low-light conditions was an interesting task.
“You’ve got cloud cover or haze or even pollution—enough of your irradiance is scattered and there’s not a direct beam coming from the sun,” he said. “On a perfectly overcast day with no sun peeking through, your best energy production would be perfectly flat, so the panel sees as much of the sky as possible for diffused light.”
NEXTracker’s TrueCapture system’s ability to recognize low light conditions and adjust panels to a better angle will even prove beneficial to thin-film projects, which already perform better than c-Si in low light. A small “computer” is connected at each row and wirelessly links with the tracking site’s main controller. Since each of NEXTracker’s rows are self-powered by one motor, they can act independently and adjust as needed. TrueCapture is currently being used on new projects and can be added to older projects too.
“It’s really exciting to come in with basically a software layer and a few extra instruments for detecting the diffused light conditions and be able to get this additional energy value out of existing sites,” Beardsworth said.
Read more at Solar Power World.