High-flying turbine produces more power 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 1000 to 2000 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 innovationMuch 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 productGlass 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.