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Making a wire-free future

July 9, 2014 in Electric Vehicles, EV charging, EV News

WiTricity’s wireless charging technology is coming soon to mobile devices, electric cars, and more.

This diagram shows how WiTricity Corp.'s highly resonant coupling works. When a highly resonant transmitting copper coil, connected to an AC power source (top, left), is tuned to the same frequency as a highly resonant receiving copper coil (bottom, left), the two coils exchange energy efficiently over distances via the magnetic field (right).  Courtesy of WiTricity Corp.

This diagram shows how WiTricity Corp.’s highly resonant coupling works. When a highly resonant transmitting copper coil, connected to an AC power source (top, left), is tuned to the same frequency as a highly resonant receiving copper coil (bottom, left), the two coils exchange energy efficiently over distances via the magnetic field (right).
Courtesy of WiTricity Corp.

By Rob Matheson, MIT

More than a century ago, engineer and inventor Nikola Tesla proposed a global system of wireless transmission of electricity — or wireless power. But one key obstacle to realizing this ambitious vision has always been the inefficiency of transferring power over long distances.

Near the end of the last decade, however, a team of MIT researchers led by Professor of Physics Marin Soljacic took definitive steps toward more practical wireless charging. First, in 2007, the team wirelessly lit a 60-watt light bulb from eight feet away using two large copper coils, with similarly tuned resonant frequencies, that transferred energy from one to the other over the magnetic field. Then, in 2010, they shrunk the coils down and significantly increased the efficiency of the system, noting future applications in consumer products.

WiTricity Corp. recently unveiled a design for a smartphone and wireless charger powered by its technology. The charger can charge two phones simultaneously, and can be placed on top of a table or mounted underneath a table or desk. Courtesy of WiTricity Corp.

WiTricity Corp. recently unveiled a design for a smartphone and wireless charger powered by its technology. The charger can charge two phones simultaneously, and can be placed on top of a table or mounted underneath a table or desk.
Courtesy of WiTricity Corp.

Now, this “wireless electricity” (or “WiTricity”) technology — licensed through the researchers’ startup, WiTricity Corp. — is coming to mobile devices, electric vehicles, and potentially a host of other applications.

The aim is to forge toward a “wire-free world,” says Soljacic. Primarily, this means consumers need not carry wires and power bricks. But it could also lead to benefits such as smaller batteries and less hardware — which would lower costs for manufacturers and consumers.

“It’s probably a dream of any professor at MIT to help change the world for a better place,” says Soljacic, a WiTricity co-founder who now serves on its board of directors. “We believe wireless charging has a potential to do that.”

He is not alone. Last month, WiTricity signed a licensing agreement with Intel to integrate WiTricity technology into computing devices powered by Intel. Back in December, Toyota licensed WiTricity technology for a future line of electric cars. Several more publicized and unpublicized companies have recently joined in the licensing parade for this technology, including Thoratec for their implantable ventricular assisting devices, and TDK for wireless electric vehicle-charging systems. There’s even talk of a helmet powered wirelessly via backpack, specifically for military applications.

At present, WiTricity technology charges devices at around 6 to 12 inches with roughly 95 percent efficiency — 12 watts for mobile devices and up to 6.6 kilowatts for cars. But, with growing research and development, the company is increasing distance, scale, and efficiency. It’s also developed repeaters: passive devices that extend the distance of the power transfer. These can be developed into a wide variety of shapes and can be embedded in a carpet to “hop” the power across a room.

Stronger coupling

Similar wireless charging technologies have been around for some time. For instance, traditional induction charging, which uses an electromagnetic field to transfer energy between two coils, is used in transformers and wireless toothbrushes. In the past two years, there’s also been an increase in wireless cell phone charging pads based on induction.

“These work well, but only over very short distances, so they’re nearly touching,” Soljacic says. “They become dramatically inefficient when the distance increases.”

Lasers can also move energy between two points, such as two satellites. But this requires an uninterrupted, continuous path between the transmitter and the receiver, which “is obviously not ideal for consumer products,” Soljacic says.

WiTricity’s system of transmitters and receivers with magnetic coils, on the other hand, “efficiently transfers power over longer distances,” says CEO Alex Gruzen ’84, SM ’86. “It can also charge through materials such as wood or granite, allow freedom to move the devices around, and charge several devices at once.”

To make the system more efficient, WiTricity tunes the coils to find a strong electromagnetic highly resonant coupling. This is similar to a tuning fork vibrating when exposed to a sound of the right frequency, or a radio antenna tuning into a single station out of hundreds.

The concept took shape in early 2000s, when Soljacic awoke at 3 a.m. to the beeping of his cell phone running out of battery life. Frustrated, and standing half awake, he contemplated ways to harness power from all around to charge the phone.

At the time, he was working on various photonics projects — lasers, solar cells, and optical fiber — that all involved a phenomenon called resonant coupling. “The underlying physics could be easily applied to power transfer,” he says.

A new category of magnetic resonance

Seeing use for consumer devices, Soljacic and a team of five MIT researchers — including physics professors Peter Fisher and John Joannopoulos — published a proof-of-concept experiment in Science in 2007, and founded WiTricity that same year.

In the experiment, the researchers used two copper coils, about two feet across, each a self-resonant system. One transmitting coil was connected to an AC power supply, while another connected to a 60-watt light bulb.

The transmitter emanated a magnetic field, oscillating at megahertz frequencies, which the receiver matched, ensuring a strong coupling between the units and weak interaction with the rest of the environment, including nonmetallic materials — and humans. In fact, they demonstrated that they could light the bulb, at roughly 45 percent efficiency, with all six researchers standing in between the two coils.

Gruzen uses the following analogy: A room is packed with 100 wine glasses, each filled with a different level of wine to ensure a different resonant frequency. “If an opera singer belts out a note inside that room, the glass with the corresponding frequency accumulates enough energy to shatter, but none of the other glasses will resonate enough to break,” he says.

A 2010 paper published in Applied Physics Letters by Soljacic and colleagues made another breakthrough: They found that when adding more receiver coils, power transfer efficiency climbs by more than 10 percent. In that experiment, they used larger transmitting coils, but receiving coils that were only a foot across, resulting in a power output of 50 watts from several feet away.

“This enabled the development of a whole new category of magnetic resonance,” Gruzen says. From there, the company focused on finding the optimum design of the coils and electrical control systems for commercial applications.

Wireless charging: An expectation

These days, Gruzen sees wireless charging as analogous to the evolution of a similar technology — WiFi — that he witnessed in the early 2000s as senior vice president of global notebook business at Hewlett Packard.

At the time, WiFi capabilities were rarely implemented into laptops; this didn’t change until companies began bringing wireless Internet access into hotel lobbies, libraries, airports, and other public places.

Now, having established a standard for wireless charging of consumer devices with the A4WP (Alliance for Wireless Power) known as Rezence, WiTricity aims to be the driving force behind wireless charging. Soon, Gruzen says, it will be an expectation — much like WiFi.

“You can have a charging surface wherever you go — from a kitchen counter to your workplace to airport lounge and hotel lobbies,” he says. “In this future, you’re not worried about carrying cords. Casual access to topping off power in your devices just becomes an expected thing. This is where we’re going.”

With an expected rise of wireless charging, one promising future application Soljacic sees is in medical devices — especially implanted ventricular assist devices (or “heart pumps”) that support blood flow. Currently, a patient who has experienced a heart attack or weakening of the heart has wires running from the implant to a charger — which means risk for infection.

“In our case, a patient could lie on the bed and, while he or she is sleeping, our technology could charge the device from a distance,” Soljacic says. “We expect to have much more of these embedded electronic devices in people over the next decade or so.”

This article is a repost, credit: MIT.

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High-flying turbine produces more power

May 15, 2014 in Environment, EV News, Greentech, Wind

MIT alumni develop airborne wind turbine that floats 1,000 feet aloft to capture stronger, steadier winds.

The Buoyant Air Turbine (or BAT), developed by Altaeros Energies, uses an inflatable shell to float 1,000 to 2,000 feet above ground, where winds blow five to eight times stronger, and more consistently, than winds at tower level.  Courtesy of Altaeros Energies

The Buoyant Air Turbine (or BAT), developed by Altaeros Energies, uses an inflatable shell to float 1,000 to 2,000 feet above ground, where winds blow five to eight times stronger, and more consistently, than winds at tower level.
Courtesy of Altaeros Energies

By Rob Matheson, MIT

For Altaeros Energies, a startup launched out of MIT, the sky’s the limit when it comes to wind power.

Founded by alumni Ben Glass ’08, SM ’10 and Adam Rein MBA ’10, Altaeros has developed the world’s first commercial airborne wind turbine, which uses a helium-filled shell to float as high as a skyscraper and capture the stronger, steadier winds available at that altitude.

Proven to produce double the energy of similarly sized tower-mounted turbines, the system, called Buoyant Air Turbine (or BAT), is now readying for commercial deployment in rural Alaska.

Surrounded by a circular, 35-foot-long inflatable shell made of the same heavy-duty fabric used in blimps and sails, the BAT hovers 1,000 to 2,000 feet above ground, where winds blow five to eight times stronger, as well as more consistently, than winds at tower level (roughly 100 to 300 feet).

Three tethers connect the BAT to a rotating ground station, automatically adjusting its altitude to obtain the strongest possible winds. Power generated by the turbine travels down one of the tethers to the ground station before being passed along to microgrids.

“Think of it as a reverse crane,” says Glass, who invented the core BAT technology. “A crane has a nice stationary component, and an upper platform that rotates in order to suspend things down. We’re doing the same thing, but suspending things up.”

Next year, the BAT will test its ability to power microgrids at a site south of Fairbanks, Alaska, in an 18-month trial funded by the Alaska Energy Authority. People in rural Alaska rely on gas and diesel generators for power, paying upward of $1 per kilowatt-hour for electricity. The BAT, which has a capacity of 30 kilowatts, aims to drop that kilowatt-hour cost down to roughly 18 cents, the co-founders say.

But despite its efficiency, the BAT is not designed to replace conventional tower-mounted turbines, Rein says. Instead, its purpose is to bring wind power to remote, off-grid areas where towers aren’t practically or economically feasible.

Conventional turbine construction, for instance, requires tons of concrete and the use of cranes, which can be difficult to maneuver around certain sites. The modular BAT, Rein says, packs into two midsize shipping containers for transport “and can just be inflated out and self-lift into the air for installation.”

Target sites include areas where large diesel generators provide power — such as military bases and industrial sites — as well as island and rural communities in Hawaii, northern Canada, India, Brazil, and parts of Australia. The BAT could also provide power to places blacked out by natural disasters, as well as at amusement parks, festivals, and sports venues.

“It’s really about expanding wind energy to all those places on the fringes where it doesn’t really work today, and expanding the amount of wind power that’s able to be deployed globally,” Rein says.

Aerostat innovation

Much of the BAT’s innovation lies in its complete autonomy, Glass says. Such aerostats usually require full-time ground crews to deploy, land, and adjust. But the BAT automatically adjusts to optimal wind speeds and self-docks in case of emergencies, eliminating the need for manual labor.

“When winds are low, typically we want to go as high as possible — because, generally speaking, the higher you are, the stronger the winds,” Glass explains. “But if winds get too high, above the maximum [capacity] of the turbine, there’s no reason to operate in those very strong winds, so we can bring it down, where it operates at rated power, but is not subject to very strong winds.”

To guide its positioning, the BAT is equipped with anemometers installed in the airborne unit and ground station. When the anemometers detect optimal wind speed, a custom algorithm adjusts the system’s tethers to extend or contract, while the base rotates into the wind. In rare instances, when wind conditions are optimal on the ground, the system will self-dock, but continue rotating.

Designed to handle winds of more than 100 mph, the system is unaffected by rain or snow. However, should the weather get too inclement, or should a tether break loose, the BAT’s secondary grounding tether — which protects the system’s electronics from lightning strikes — will self-dock.

Because the BAT is an advanced aerostat platform, Glass says, customers can use it to lift additional “payloads,” such as weather monitoring and surveillance equipment.

But perhaps the most logical added “payload,” Glass says, is Wi-Fi technology: “If you have a remote village, for instance,” he says, “you can put a Wi-Fi unit up, outside the village, and you’re much higher than you’d get with a traditional tower. That would allow you to cover six to eight times the area you would with a tower.”

Prototype to product

Glass first conceived of the BAT while working at MIT toward his master’s degree in aeronautics and astronautics. Harboring an interest in wind turbine design, and knowing that traditional towers could never reach high-altitude winds, he designed the BAT in his free time, receiving technical guidance from Institute Professor Sheila Widnall and other faculty.

Soon, he’d bring his concept to 15.366 (Energy Ventures), a class at the MIT Sloan School of Management where engineering, policy, and business students build startups around clean tech ideas. At the time, Rein, who had done independent research on clean energy, was an MBA student and teacher’s assistant for the class who helped Glass flesh out an initial business model.

The duo — along with Harvard University grad student Alain Goubau and investor Alex Rohde, then an Alfred P. Sloan Fellow — soon formed Altaeros. They solicited advice from seasoned entrepreneurs at MIT’s Venture Mentoring Service (VMS) — “our first advisory board,” Rein says — who steered the startup toward rapid prototyping by using low-cost, off-the-shelf materials.

For their first power-producing prototype, they bought a small, reliable wind-turbine rotor, “and cut off some metal in the back that was dead weight and built a composite nacelle to hold our custom electronics and control systems,” Rein says.

In 2012, Altaeros, after just two years of refining, proved the BAT’s efficiency at 300 feet above ground at a former Air Force base in Maine, where the company still assembles and tests the system. They did so again last August, at 500 feet in 45-mph winds.

Altaeros remains headquartered in cleantech incubator Greentown Labs (which Rein co-founded), in Somerville, Mass. — where its first rotor is proudly displayed near the entrance, along with enlarged photos of the first trial run. At Greentown, employees engage in computer modeling and design, build electronics and circuit boards, develop algorithms, and test winches and cables.

Looking back, Glass credits his undergraduate years on MIT’s Solar Electrical Vehicle Team — a student organization that builds and races solar cars for competition — with giving him the experience and motivation to bring the BAT from concept to reality.

“Just being able to see a project from design and analysis stage through building, testing, and operating was valuable,” he says. “It’s also something that helped in leading a technical team at Altaeros, to essentially do the same thing on a bigger scale.”

For now, Altaeros is focused on finalizing the commercial product for Alaska and, eventually, deploying the technology worldwide. “To take the system from concept to actual prototype has been exciting,” Glass says. “But the next step is making the prototype a commercial product and really seeing its real-world performance.”

This article is a repost, credit: MIT.