Of all the different kinds of renewable energy, wind might be both the easiest to manage and the most frustrating. Turbines are relatively cheap and easy to build and deploy, but wind is a fickle mistress, and an idle turbine is barely fit for birds to poop on. Solution? Send the turbine to the wind instead.
The 130 pound, 28 foot wide wind turbine in the picture above (called Wing 7) is probably not like any wind turbine you've ever seen. Most notably, it's not a giant white tower plugged into the ground. Instead, it's more of a helicopter, able to take off vertically and fly several thousand feet straight up, tethered to the ground by a power cable. When the craft finds an altitude with a steady wind, it uses its tail to rotate 90 degrees, and the wing provides enough lift to keep the system aloft (like a kite). Meanwhile, the propellers are free to function as wind turbines, sending electricity back down to the ground through the tether.
Wing 7 may seem small compared to more traditional wind turbines, but it's able to produce a respectable 20 kilowatts with just 22 mph worth of wind. And since the winds aloft tend to be much more reliable than winds at ground level, it's a much more consistent source. Wing 7 is modular and movable, and just needs a flatbed truck for deployment and to act as a base station. To land, the Wing simply transitions back to vertical, and it gets winched down to the ground.
With this proof-of-concept ready to go thanks to funding from ARPA-E, the next step is to embiggen Wing 7 to a much larger version capable of producing a megawatt, which could see commercial deployment by 2015.