The sprawling hills of California’s Altamont Pass are covered in thousands of wind turbines nearly three decades old. But many of those aging models are coming down as wind developers replace them with a smaller number of giant, more powerful turbines.

For Rick Koebbe, the switch spells opportunity.

Koebbe, president of PowerWorks, runs a sort of wind-turbine hospital from a manufacturing facility in the San Francisco Bay Area. The firm takes old, 100-kilowatt models that would otherwise head to the scrap yard and replaces their well-worn screws, gears, bearings and generators with gleaming new parts. The steel towers and blades are generally still in good shape, so they stay put. Koebbe said his second-hand turbines are an attractive bargain—they sell for as little as half the price of a fresh-off-the-assembly-line model.

“There are very few people doing this,” he said.

PowerWorks is part of a niche global market that is emerging for used turbines. While earlier attempts by U.S. companies to sell the models at home have waned, demand appears to be picking up in developing countries and island nations—places where wind power costs far less than electricity from imported fossil fuels, but where ponying up millions of dollars for today’s massive wind turbines doesn’t make sense.

Vestas, the world’s largest turbine maker, is tapping the market itself. Last fall, it launched an initiative called Wind for Prosperity to refurbish older, smaller turbines from Europe and sell them cheaply to communities with limited or no access to electricity. Vestas is piloting the model with a dozen places in Kenya, and it is optimistic that the second-hand turbine market can be a moneymaker for the company. “Making profits is the most important thing here,” Morten Albaek, a senior vice president for Vestas Wind Systems A/S, said in remarks for a panel about the initiative last month.

PowerWorks first started refurbishing turbines about two years ago. The California company owns and operates nearly 1,000 wind turbines and sells the clean power to electric utilities. As it began taking down older turbines—either because of their tired condition or because a utility contract ended—PowerWorks sent the models to the warehouse for a facelift.

So far, PowerWorks has sold 20 refurbished models to farmers in Nevada, where a special state tax incentive makes it cheaper to own the smaller turbines. But with that incentive winding down, and with few other states offering similar breaks, Koebbe said the company is setting its sights abroad. PowerWorks has marketed its used turbines all across the globe and is close to securing the sale of several units in multiple countries, which he declined to name.

“We’re still really getting started into it. It takes a while to develop a market,” Koebbe said.

The California Wind ‘Gold Rush’

A 100-kilowatt turbine can power roughly 20 American homes on average, and a new model costs as much as $350,000, according to the American Wind Energy Association (AWEA), the main industry group.

The turbines first appeared en masse in the United States in the late 1970s, after the federal government approved special incentives for renewable energy following the 1973 oil crisis. Additional state enticements in California created what many have likened to a Gold Rush-type wind boom in the Altamont Pass, a 50,000-acre swath of cattle ranching land.

The initial rush soon died down, however, and it wasn’t until 2005 when the technology and economics were right for a second wave of U.S. wind power development. Today more than 45,000 turbines are installed across the country, and most of them are far taller and less dense—making them a less damaging obstacle to migratory birds—and more powerful than the earlier models. Together the turbines can generate more than 61,000 megawatts of wind energy—enough to power roughly 15.3 million American homes.

In the late 2000s, many of the older, 100-kilowatt models in the Altamont Pass started coming down as developers opted for better and bigger, less densely grouped models —and to reduce bird fatalities.

The mountainous area is a key migratory corridor and home to many birds of prey. Over the years, the tightly packed clusters of smaller turbines have killed tens of thousands of birds and bats. In 2010, the state of California required NextEra Energy, the developer with the largest share of turbines in the area, to replace 2,400 older models with about 100 new ones by 2015. Each new turbine will generate up to 23 times more wind power than its predecessor and stand nearly four times taller.

Many of the Altamont Pass turbines have gone or will go straight to the scrap heap. Initially, a handful of tiny new businesses started snapping up some of the older models for cheap to rebuild and resell to small-scale developers.

Walt Wunder, president of Aeronautica Windpower in Plymouth, Mass., said his company was among that group. The company started refurbishing the California turbines in 2008. It saw “decent demand,” mainly from the agricultural sector, but only a “very tight profit line.” Not helping matters was the fact that the bulk of federal incentives driving U.S. wind installations today apply only to new turbines—not second-hand models.

About a year and a half later, Aeronautica Windpower began building and marketing new mid-scale wind turbines, and dropped the refurbishment business altogether. Since then, the company has received—and declined—just two requests for refurbished turbines. Still, like Koebbe, Wunder said he does see demand picking up internationally, especially in countries with feed-in tariffs, a program that pays clean energy operators a fixed price for the electricity they feed back to the grid. “There is a market for it” abroad, Wunder said.

Emily Williams, who leads AWEA’s operations and maintenance working group, said it could be decades before another second-hand market crops up for the bigger wind turbines being installed today. Wind projects are typically designed to last between two and three decades. “The bulk of the machines are newer and will be around for quite a few years,” she said.