For the past year, a 30-foot wide, donut-shaped helium balloon has been bobbing a thousand feet above Fairbanks, Alaska, carrying a 30-kilowatt wind turbine. The aim is simple: to generate energy from high-altitude wind currents, which are up to eight times more powerful and significantly more consistent than those at ground level.

Altaeros Energies, the MIT-affiliated startup behind the Fairbanks project, is one of more than 20 small companies worldwide now exploring high-altitude wind technologies. Altaeros’s turbine-balloons are designed for small communities in remote areas, where high energy costs make experimental alternatives economically viable. “Eliminating the costs that are associated with power installation makes this type of deployment very attractive,” says Alan Baldivieso of the Alaska Energy Authority, which invested $1.3 million in the project.

While most high-altitude wind companies are small, scrappy startups, a handful of big investors are getting involved. Top of the heap: Google, which invested $15 million in high-altitude startup Makani before acquiring the company outright in 2013. Makani, now part of the tech giant’s Google X research division, is currently testing kite-based turbines capable of delivering around 600kw. The technology is still some way from being market-ready, but Google X director Sergey Brin believes utility-scale systems will one day emerge as practical, cost-effective alternatives to ground-based wind-farms. “We don’t invest in sure things, but we don’t invest in crazy ideas, either,” he told the New Yorker.

The high-altitude sector remains chaotic: around the world, companies are testing a wide range of lighter-than-air, hard- and soft-wing technologies, and there’s no consensus about which approaches are most promising. Along with concerns over safety, durability and regulatory oversight, that uncertainty has led to a high attrition rate: numerous firms, including Canadian blimp-based turbine company Magenn, have failed or gone dormant in recent years. “It’s clear that many of the current organizations in the field were started at best with optimistic assessments issues regarding safety and aviation authority approvals,” warns IBM’s Mike Barnard.

Still, wind energy remains a major growth sector, with private investment averaging $12.2 billion over the past five years. Most of that cash is bankrolling conventional wind farms, but both utilities and wind-energy firms are watching the high-altitude sector carefully, and exploring ways to take advantage of higher-altitude wind currents. The average hub height for U.S. ground-based turbines increased from about 114 feet in 1999 to almost 328 feet in 2010, and some companies are now testing turbines that reach heights of more than 700 feet. That’s having a big impact: the trend towards taller towers recently led the Department of Energy to upgrade its estimate of total potential U.S. wind-energy resources by 40 percent.

That’s a reminder of the enormous untapped potential of high-altitude wind power, says Stanford climatologist Ken Caldiera. He estimates that globally, high-altitude wind could supply about 1,800 terawatts, or four times more than ground-based turbines. “There is more than enough energy in high-altitude winds to power all of civilization,” he told reporters.


Companies to watch

*   Google (NASDAQ: GOOG) bought high-altitude innovator Makani in 2013, after previously investing $15 million in the company. Makani now operates as part of the search giant’s Google X research division.

*  Boston’s Altaeros Energies banked $7 million in funding from SoftBank (TYO: 9984) in December, with the Japanese telecom saying the startup’s technology was well-suited to remote areas in the Asia-Pacific region.

*  North Carolina’s Windlift has been working since 2012 to develop portable high-altitude turbine systems for the Marine Corps. The company plans to open a new fundraising round later this year.

*  Holland’s Ampyx Power is seeking to raise 25 million euros from informal and institutional investors during 2015, and plans to commercialize its glider-based turbine technology by 2017.

*  Italy’s KiteGen Research is currently running a crowdfunding campaign to begin rolling out its KiteGen Stem technology, a 3MW ground-based turbine powered by circling kites.

*   DSM (AMS: DSM), the Dutch multinational materials giant, sees the high-altitude wind sector as a potential growth market for its proprietary Dyneema fabric, the durability and high tensile strength of which makes it well-suited for tethering turbines.


Ben Whitford is the US correspondent for The Ecologist. He has written for the Guardian, Newsweek, Mother Jones, Slate, and many other publications.