Mary Claire McCarthy
Windlift’s mission is to create energy for a sustainable civilization.
Many engineers, visionaries and engineers are working towards similar goals, but few are doing so with airborne wind energy (AWE). A rapid transition to renewable energy is critical for avoiding the most severe greenhouse gas emissions projections–that much we know. AWE could significantly shift the winds in humanity’s favor.
AWE is a next-generation wind energy technology that harnesses stronger, more persistent winds with significantly reduced materials to create a highly mobile, energy-dense and autonomous system. Here at Windlift, we’re creating our own AWE system, the Airborne Power Generator (APG). But before we dive into what makes our technology unique, I want to start from the beginning. What is AWE exactly? How does it work?
What is Airborne Wind Energy?
AWE was first imagined in the oil crisis of the late 1970s by Miles Loyd, an engineer at Lawrence Livermore National Laboratory in the United States. Loyd first studied a phenomenon that kite-fliers have known for centuries. A kite that moves across the wind, or perpendicular, pulls much harder than a stationary kite with the wind behind it. He calculated that a kite flown in fast loops across the wind (cross-wind flight) can produce enough lift to support itself and enough to generate additional power—hundreds of times more power than a kite in static flight.
At the time, the price of input materials was too high to compete with decreasing oil prices. But in the last decade, interest has skyrocketed as AWE has developed from a pool of conceptual ideas and first small-scale experiments into a vibrant field of R&D. This research has produced a diverse range of technologies that can produce power outputs of several hundred kilowatts. Today, over $500 million has been invested in AWE globally from over 50 research institutes and startups. In addition, the U.S. government recently indicated its growing interest; the FY21 Senate Appropriations Bill included a specific call out for research into AWE and $125 million a year for wind energy research.
Loyd’s ideas are the basis for the airborne wind energy we see today. AWE technology converts wind energy into electricity with autonomous tethered flying devices. There are two primary methods for generating electricity amongst AWE systems. These include fly-generation (‘fly-gen’) and ground-generation (‘ground-gen’). Fly-gen systems fly crosswind to produce electricity on the craft itself. Onboard motors convert wind energy into mechanical energy. Airborne wind generators then convert the mechanical energy into electrical energy (electricity) and send it down a conductive tether to the ground for further use. Alternatively, ground-gen systems generate electricity from the ground using a yo-yo technique. The airframe pulls on the tether, causing it to unwind from a drum on the ground, driving a generator that produces electricity. Once the tether unwinds completely, it is reeled back in, and the process starts over again.
What makes AWE unique?
These unmanned aerial vehicles (UAV) are a breeze compared to traditional wind energy technology! Conventional wind turbines work by spinning massive, wing-like blades atop a rigid tower that is, on average, 300-feet tall. While these systems are an essential part of the U.S. energy mix, their size limits mobility. Wind turbines take months to install and are permanently embedded in a single location. Their size also increases other factors like capital costs, installation costs and maintenance complexities.
On the other hand, AWE systems are not attached to a tower and base. They fly free on a tether — all while generating more power per amount of materials (weight)! The Windlift APG uses only 5% of the materials compared to conventional wind turbines. Yes, you read that right—only 5%! You’re probably wondering how a significantly smaller system can produce comparable power. The answer largely lies in the system’s lightweight and flight pattern. AWE technology sweeps through a larger cross-section of the sky, allowing a modestly sized airfoil to extract larger amounts of energy compared to ground turbines. At a wingspan comparable in length to a wind turbine blade, an AWE system can sweep a larger region of the sky to access nearly 20 times more energy! The airfoil flies crosswind in a circle or figure-eight pattern at many times the wind’s speed.
Fewer materials & stronger winds.
In addition, AWE systems access higher-altitude winds with less material. Consequently, AWE systems can provide a higher capacity factor (the energy the system can produce) at lower costs. Peer-reviewed papers estimate AWE could reduce the cost of wind energy tenfold. AWE technology packs a serious punch. For example, producing 6X the amount of energy per pound compared to conventional wind turbines!
These two elements, taken together, make for a lightweight, agile and energy-dense system unrestricted by geophysiology—mountains, offshore wind farms, off-the-grid farms — you name it. AWE systems deliver power no matter how remote or diverse. The Windlift APG delivers power when and where you need it most.