There aren't too many old, inefficient solar panels in the U.S. Even the oldest panels continue to produce nearly as much energy as when they were first installed, according to Brian Ross, vice president for renewable energy at the Great Plains Institute, a nonpartisan energy and environment think tank.
Yet Ross and other experts agree that the owners of older solar farms are approaching a decision point about the maintenance and potential upgrade of their projects. But it’s not the panels that are driving the trend — it's the inverters that convert energy from the panels into AC power for the grid.
Many older inverters haven't lived up to their expected lifespans, with most beginning to fail around the 10-15 year mark, according to Levent Gun, CEO of Ampt, a solar power conversion product manufacturer. To make matters more challenging, most of the manufacturers of these inverters — the companies that were supposed to maintain them and guarantee their performance over time — have gone out of business, Gun said.
“These projects were designed for 20-25 year lifespans, and it's a well known fact that the first and second generation inverters have a 15-year average lifespan,” said Daniel Liu, who heads research on asset performance benchmarking, cost analysis and valuations at Wood Mackenzie. Like it or not, he said, “the market is going to have to repair a lot of inverters over the next ten years.”
According to projections by Wood Mackenzie, some 23 GW of U.S. solar — residential, commercial and utility-scale — will approach that 15 year benchmark in the next five years. And given the complexity of switching out inverters on some of these early solar installations, some solar equipment dealers recommend knocking out a host of potential upgrades all at once: replacing old panels and wiring with new equipment to maximize efficiencies, or even installing batteries for a solar+storage facility while you're at it.
But this emergence of what could become the solar equivalent of repowering aging generating units could tax aspects of the industry's already strained supply chain, and experts at the tail end of that chain say it could be especially difficult to dispose of the panels that may be removed and replaced during these inverter-inspired upgrades.
The number of U.S. solar projects that will require inverter upgrades in the next few years may not be particularly large by itself, but it won't be inconsequential, either. An average of 4.5 GW of solar projects will need new inverters every year for the next five years; that's nearly half of the capacity installed in the U.S. some years, Liu said.
As a supplier of inverters, Gun estimated that Ampt has replaced inverters on between 1-1.5 gigawatts of solar projects in the first half of the year, which represents less than 10% of the company's current business.
But Gun expects that could change in the near future, based on the growing number and size of solar projects aged ten years or older. And it's not just inverter failure that's driving demand, he said — repowering is also an increasingly popular option when existing modules are damaged by severe weather, which has grown more frequent. Within the next three to five years, he said, he expects repowering will represent a sizable chunk of Ampt's business.
“Now this is becoming a bigger problem, and we feel that repowering is going to start picking up,” he said. “It's been going at a steady pace [since the company did its first large solar repowering project in Canada in 2016], but now we are seeing more and more demand.”
Whether there will be enough inverters to fulfill all these orders is another question, Liu said. The U.S. will need about 74 GW of new inverters every single year through 2031 for new solar projects. U.S. manufacturing capacity for inverters is expected to hit 100 GW toward the end of that time frame, Liu said, but for the immediate future, adding another 4-5 GW of demand could create some difficulties.
“It's not going to be disastrous,” he said, “but there will be competition between repowering and new build, and new build is likely going to win.”
The battery upsell
Unexpected equipment repairs are never convenient. But in this case, Gun said, they can also represent an opportunity — and not just for an equipment supplier and installer like Ampt, but for the project owners as well.
Because of advances in inverter technology, it will be difficult for older solar farms to find one-to-one replacements for their original inverters, he explained. Modern inverters like those provided by Ampt generally handle more voltage than earlier generations of the technology, which in some cases means the capacity of the farm itself could expand, either by capturing more power from existing modules, or by upgrading and expanding the project.
But in order to take advantage of this opportunity in today's market, you need batteries. Interconnection challenges limit a developer’s ability to add new capacity to the grid, and even existing output is being curtailed in some markets. Batteries, quite conveniently, can be installed during an inverter replacement — often by the same contractors, Gun said.
Ampt has yet to add batteries to one of its repowering projects, Gun said, but customers have expressed interest and he anticipates it will be done in the future.
Multiple solar developers and project operators did not respond to requests for comment on this story.
The future of repowering
Even with the growing age of the solar fleet, repowering may not play out in the solar sector the way it has in the wind industry, Liu said. Wind project components tend to wear out at roughly the same time, giving rise to the opportunity to upgrade and replace the bulk of the project hardware all at once. Solar, at least so far, hasn't seen the same phenomena, suggesting solar repowering could be more piecemeal in nature.
Similarly, solar hasn't experienced the same sort of exponential improvements in technology and efficiency that drive the repowering phenomenon in wind, Ross said. In the wind industry, repowering is primarily driven by economics — advances in engineering significantly increased the maximum rotor size and turbine height, and project developers could bring in far more revenue by upgrading to the latest technology. Solar modules just haven't seen efficiency gains of the same magnitude, so there's less incentive to replace modules before the end of their warrantied life, he said.
And once they reach that end-of-life, Ross said, solar farms could face another hurdle: many are located on land with permits that require that land to return to a previous use such as farming once the solar facility reaches the end of its projected life. For some projects, that could mean decommissioning rather than repowering after panels begin to fail.
To be fair, Ross thinks this last scenario is likely to remain an outlier: once a solar farm goes onto a piece of property, he said, it's likely to remain a solar farm. At least for the foreseeable future, the most valuable thing about that site is its interconnection agreement — developers aren't likely to readily give up access to the grid. And most communities, Ross believes, can be persuaded to keep solar farms around. From his perspective as a trained land use planner, solar farms are much easier to decommission and convert to other purposes than, say, a big box store. So there is little risk to adjacent communities in extending time-bound permits for solar farms.
But whether aging solar farms are repowered and upgraded all at once or over time, there is one issue that does remain largely unaddressed, Ross said: the U.S. doesn't currently have the capacity to dispose of or recycle all the old panels coming off its first generation of solar farms.
End of life planning
AJ Orben, vice president of We Recycle Solar, didn't really plan to get involved in repowering projects. But in the last few years, the rising tide of old inverters has benefited his line of work as the number of panels coming off repowered projects has increased.
Most of the panels Orben removes from these sites have little to no defects and potentially years of useful life ahead of them. That's allowed We Recycle Solar to refurbish and sell the panels from these projects into markets where brand-new solar panels remain cost prohibitive.
But now that supply chains have begun to normalize, demand for refurbished panels, and therefore the price Orben can command, has dropped. And the cost of breaking panels into their component parts is greater than the value of the materials they contain. Keeping millions of solar panels — many of which may still have useful life left in them — from ending up in landfills will likely require a change in policy, Orben said.
So while some solar farms have begun to age, serious consideration of what it will mean to dispose of the gigawatts of panels that solar developers and policy makers hope to deploy in the coming decades has only just begun. Current talk of repowering, it seems, more closely resembles a midlife crisis than end-of-life planning.
Correction: This story has been updated to provide a more accurate description of Ampt.