Early PV tracking systems did not always hit the mark. But recent developments in tracking technology are helping to bring about genuine improvements in efficiency.
Josefin Berg sums up the tracking system challenge with an observation from the field. “In Spain you can see trackers pointing in different directions,” says the IHS Emerging Energy Research Europe solar power advisory analyst.
Since even sunny Spain only boasts one source of solar irradiation, if panels are facing towards different parts of the sky that means someone’s tracker is not working, and someone is not getting the full return on their PV investment.
And the irony is their investment will have been higher because of the tracker that is costing them money. “You get a 20% to 30% additional yield if it works well,” Berg says.
But, she adds: “If you install a tracking system the cost can increase, depending on the model, somewhere between 10% and 30%. You have to make your calculations pretty clear.”
Craig Stevens, president of the analyst firm Solarbuzz, confirms this. “The issue here is reliability and cost, including land cost,” he says. “The economics are a function both of the cell type and source, and the tracking system performance and cost.”
Furthermore, tracking systems only really make sense in latitudes where the sun is strong enough to make it worth following. That is why developers did not care much for such systems while the market was dominated by Germany.
Thin film modules located anywhere South of Berlin are dependent on trackers for a decent ROI, so their future in thin film is deeply engraved into the market’s future plans. First Solar understands this fact and recently acquired a US tracker firm for close to $40m earlier this year and is currently deploying single axis trackers at one of its solar ranches.
Berg says: “The standard is no tracking, because, on one hand, you have all the rooftop systems, and if you look at ground-based systems, because Germany is such a large market and does not have the solar resources to justify a tracking system.”
That is probably why Spain, with better solar irradiation, bore the brunt of the nascent tracking industry’s early research and development efforts.
“Trackers got a bad name in the early days because people put them together in the field,” admits Tim Keating, vice president of marketing and field operations at CPV manufacturer Skyline Solar. Now, though, trackers go through rigorous testing and “tracking is hotting up.”
In Italy, for example, there is a sound financial incentive to invest in tracking systems. Following the country’s 4th Conto Energia law in May, permits are only being granted to PV plants on agricultural land if they do not exceed 1 MW per installation.
As a result, explains Berg: “You see a lot of 0.99 MW plants going up. If you add tracking you get the return of a 1.2 MW system without having to worry about the permit.”
With the government generally scaling back incentives for PV, however, the Italian market alone is unlikely to be a major force for tracking research and development.
Evolution of tracking
“The evolution of tracking will be driven by the US, North Africa and maybe India,” says Berg. “There are still a lot of improvements to be made.”
Some major trends are becoming apparent, however, and perhaps not least because of the growing importance of technologies, such as CPV, which requires tracking as standard, and the efforts of leading players such as Amonix, DEGERenergie, Mecasolar, Sunseeker and Soitec.
For example, says Keating: “What I have seen is that the requirement for single-axis trackers is going to continue to balloon, and for dual-axis trackers it is going to go down, because the extra cost does not pay off. Typically it can cost four times as much.”
Jenny Chase, manager of the solar insight team at Bloomberg New Energy Finance, echoes this: “Single axis tracking is becoming more popular because you get 80% of the benefit for half the effort.”
Also, she says: “Improvements are happening in control software and control motors.”
There is still a split in opinion over whether directional systems should be based on optical sensors or computer algorithms, although, Chase says: “For something like CPV you probably want sensors; otherwise, if the ground shifts you are in trouble.
“For flat-plate PV, it’s not so important, so it would probably depend on what’s cheaper.”
Because of all these advances, she says, tracking is now “generally considered to be more economically worthwhile. It’s not rocket science.”
As an example of what tracking can achieve, Keating points out that Skyline Solar’s tracker-based CPV systems have a performance of up to 55% better than that of flat-plate systems.
“In the case of Skyline, because we are following the light you really have to get it lined up,” he says. “We use a single-axis tracker and a trough to get highly reliable tracking.”
The best bit, Keating says, is: “We think we can get our system down to the same price as a fixed tilt system, purely through clever design.”
But while price remains the big bugbear for tracking, it will not be for long, says Chase: “What will make it more competitive is that the European large-scale PV market is going to die—so manufacturers will have to push into markets that pay less.”