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The next major innovation in wind power might not involve big, white turbines dotting the countryside. KQED QUEST reports on research being done on "tethered airfoils" that could capture wind energy more efficiently that earthbound turbines. This report is part of the NewsHour's Connect series of quality public media reporting.
We look at new technology used to harness powerful winds located high above the earth into usable energy.
Our report was produced by Christopher Bauer for the science program 'Quest,' which airs on KQED San Francisco. The story is narrated by Andrea Kissack.
It is part of the series 'NewsHour Connect,' which showcases public media reporting from around the nation.
On a windswept tarmac at the former Naval Air Station in Alameda, California, an inventive group of scientists and engineers is testing the concept of a new clean energy technology.
With a changing climate and mounting energy challenges, the race is on to develop viable sources of alternative energy.
Carnegie Institution of Global Ecology: There are not very many options for providing low-carbon power at the scale of civilization. To solve this problem, we need a real revolution in our system of energy development.
Now some people are hoping a solution can be pulled out of the sky. Ken Caldeira is a climate scientist at the Carnegie Institution of Global Ecology at Stanford University.
We need huge amounts of power, and the things that can provide huge amounts of power include fossil fuels, like coal, oil and gas; nuclear power; solar power and wind. Wind is relatively affordable, but there's controversy about whether wind on the surface of the planet can provide enough energy to really power civilization.
With the right conditions, modern wind turbines are able to harness power quite well.
The force of the wind spins a turbine or a propeller, which turns a drive train, converting kinetic energy into mechanical power. That energy is then sent to generators, which convert and send it out as electricity.
But as simple as this technology seems, wind energy still only accounts for 2.8 percent of our nation's electricity.
The problem with wind is that wind is intermittent. It blows sometimes and not other times. The basic forces that drive the winds are differential heating, right? So if one place is hotter, and then another place, that tends to generate winds.
And because of the weird physics on a rotating Earth around the mid-latitudes, where you have the transition from the tropical air to the arctic air is where you get these powerful jet streams. As you go down in the atmosphere from the jet streams, the winds get weaker and weaker and more and more variable.
Winds are stronger and more consistent the higher up you go. So in order to collect the most energy, wind turbines are mounted on tall towers, up to 100 feet above the ground.
Now a number of private companies, some supported by the U.S. Department of Energy, are working to figure out how to capture power from even higher altitudes.
Launch in three — one, two, three, launch.
One company, Makani Power, is taking inspiration from an unlikely source.
CORWIN HARDHAM, CEO, MAKANI POWER:
The wing that we fly around is actually, by definition, a kite. So it's a tethered airfoil. Makani's technology is very similar to a conventional wind turbine. And, in fact, the physics and the principles behind it are exactly the same.
So if you look at a conventional turbine, the traditional tower with three blades coming off of it, and you look at that blade, the tip of the wind turbine blade is the most effective part of the blade. What we do is we take only that tip.
So if you imagine a tip flying around in circles on a wind turbine, and then imagine erasing away the rest of the wind turbine, except for one tip of one blade, and that looks just like what our wing looks like, except for we take that wing, and then we attach is to the ground with a flexible tether. And that means that we're able to fly higher than conventional wind turbines.
It also means that we're able to sweep through circles which are much larger than the circles of a conventional turbine. Higher up means the air is more consistently at a higher speed, so there's more energy in the air. We can capture more energy with less wind. And that just means that you're able to generate more energy more of the time.
Theoretically, tethered wings could fly thousands of feet high, be more than 100 feet long and consistently generate more than twice as much electricity as conventional wind turbines. But for now, Makani engineers are test-flying smaller prototypes at average altitudes of around 500 feet.
Makani is currently developing Wing 7. Wing 7 is the culmination of all of our different prototypes and, moreover, it is also the first scale mockup of what we expect our megawatt-class device to look like.
From Wing 7, we expect to build several 500-kilowatt prototypes. It'll be the first large-scale device that is also capable of flying for long periods of time. Following that, we expect to build a megawatt-class device, and that'll be our first product. And we expect that product to be fully (ph) tested, to have been flown for more than a year and be ready for production at the end of 2015.
OK, I'm restarting data acquisition. I'm starting motors now. It's spinning up.
DAMON VANDER LIND, SYSTEM DESIGN, MAKANI POWER:
And this is the Wing 7 prototype at Makani Power. It's a small-scale prototype of an airborne wind turbine.
The way it works is the wing here flies just like the tip of a blade of a wind turbine, and it propels these generators around in a circle, and moves them through the air very quickly, so that these smaller propellers can generate power, which is then shipped back to the ground over the tether.
This is the avionics, and what it does is it looks at all the sensor data coming in, and it decides what the wing should do. We take all this stuff and we put it together and use some very smart algorithms to decide what's the best thing we can do to be safe, and, number two, optimize power output.
The future of this, I see a lot of these things offshore, generating power out of sight, so we don't have to worry about them. So that's the goal.
It may seem pie in the sky, but companies like Google have backed up the potential of this technology with investment dollars. And many energy experts are betting some sort airborne wind power will soon get off the ground.
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