Google X Readies Wind Energy Kite for Test Flights
Engineering360 News Desk | December 07, 2015Google X's plans to fly "energy kites" capable of generating electricity from wind continue, with the company reporting that it is beginning site preparation in Hawaii to conduct long-duration flights of an 84-foot prototype in 2016.
The company has negotiated with Parker Ranch, in Waimea to launch its kite from their land. However, it must still obtain a Determination of No Hazard to Air Navigation from the U.S. Federal Aviation Administration before tests may begin.
The kite, which is capable of generating 600kW of energy, has been undergoing limited testing in Alameda, Calif. The long-duration flights in Waimea will evaluate its ability to fly in a known wind corridor at altitude—around 1,100 feet—and generate the expected amounts of electricity.
While Google X's prototype more resembles a small turboprop airplane than a kite, it operates on the same aerodynamic principles as a conventional wind turbine.
600kW energy kite undergoes testing in Alameda, Calif. Image credit: Google X/Makani.The energy kite simulates the tip of a wind turbine blade, the part that makes most of the energy. Eight rotors on the kite act like propellers on a helicopter to launch it from a ground station. Once the kite is at altitude, the motors turn off and the air moving across the rotors forces them to spin, driving a generator to produce electricity, which then travels down the tether to the grid.
The tether, made of conductive wires surrounding a high-strength core, connects the kite to the ground station and transfers power and communications between the kite and ground station in both directions. The ground station holds the tether and is used as a resting place for the energy kite when not in flight.
A computer system uses GPS and other sensors along with real-time calculations to guide the kite to the flight path with the strongest and steadiest winds.
The project's approach to wind generation is premised on the notion that conventional wind turbine architecture has plateaued.
According to the company's website, such wind turbines can be installed economically only where winds routinely reach speeds of 20-28 kilometers per hour. "Less than 15% of all land around the world meets [these] criteria, meaning this existing technology in its current form cannot scale," the company says.
Google X's energy kite replaces the tons of steel associated with conventional turbines with lightweight electronics and construction materials. That allows the kite to reach the stronger winds that prevail at higher altitudes and be sited in more locations because less ground space is required.
According to the company, when wind speed doubles, available power increases eightfold. That, combined with their kites' aerodynamic design, Google says, makes them 50% more efficient at generating electricity than conventional wind turbines.
The technology is not without its skeptics. Pilots have expressed concerns over the visibility of the tethers and kites—the Waimea test site is five miles from an airport. Others worry that birds may fly into the rotors or tethers.