Wind farms often produce less power when they age past the 10-year mark because the loss of federal tax credits halts maintenance – a finding that could shift policymakers’ plans for climate policy, according to a new study from Lawrence Berkeley National Laboratory.
The research, published in the journal Joule last week, is the first comprehensive account of how wind turbines across the United States degrade over time, according to researchers. Wind made up close to 8% of the nation’s power last year, when it overtook hydropower as the largest generator of renewable electricity.
The lab found that after the first 10 years of operation, wind turbines tended to experience an “abrupt decline” in performance, which continued as time went on. They produced less electricity than possible given wind conditions at a specific site.
The sudden drop-off suggested that the plants’ operators were doing something different: Since they could no longer profit from the decadelong production tax credit (PTC), companies were doing less to protect against wear and tear, having apparently decided it no longer made good financial sense, according to the paper.
After 17 years, the lost energy was equivalent to taking away 1 out of every 10 turbines in a wind farm, said Dev Millstein, a scientist at LBNL and co-author of the study.
The finding could lead some policymakers to reconsider how they value wind in the future, researchers said.
“A lot of times, the degradation of wind plants’ performance over time gets ignored,” said Millstein. “If you’re making decisions for a 20-year lifetime, it starts to matter – or if you’re estimating the cost of a project.”
Under pressure from emissions reduction laws, power companies in many states are elevating wind’s role in their long-term plans for sourcing electricity. And utility regulators, grid operators and other officials tasked with protecting grid reliability are in some cases banking heavily on wind power. In New England and the Mid-Atlantic, for example, several states have effectively ended new gas pipelines in hopes that a future fleet of giant offshore wind turbines will fill in the blank.
“The main use of these results are to help get accurate projections of how much energy wind plants are going to provide over their lifetime,” Millstein said. “That’s beneficial to the industry and to long-term planners because you’re not misrepresenting the amount of energy your plant might generate.”
Wind farm operators have a number of life-prolonging maintenance options at their disposal, including software updates, component replacements and subtler measures that protect blades from erosion.
Even after the 10-year PTC period elapsed and companies discontinued those kinds of activities, though, the U.S. fleet continued to perform fairly well compared with those of other countries, noted Millstein.
Newer wind turbines, or those built after 2008, have also proved more resilient during their first decade of life. Longer blades have allowed turbines to operate at full capacity under less windy conditions.
However, those might also see a drop-off in performance after a decade, said Millstein. “Hopefully, we get to do the research in a few years, once we have data,” he said.
“But my hypothesis would be that we’ll see some of the same behavior, where they lose some of the performance,” he added.
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