Pterosail is a small start-up company that has designed a unique vehicle: it's a custom-made recumbent trike that incorporates a sail and an electric-assist motor. The sailing system can be used in two ways: to fully power the trike, or in conjunction with pedaling. Additionally, the sailing system can convert wind energy into electrical energy to be stored into two 24-volt deep cycle marine batteries. This stored electrical power can then be used to power a small electric-assist motor. The vehicle is 50-state street-legal — basically, it can be used wherever bikes can be legally used.
The Pterosail can achieve speeds upwards of 40 miles per hour. The designers say the next generation Pterosail will have more sail area and be capable of even higher speeds. They say that the single-seat version needs about 8-10 mph of wind to start moving, while the tandem needs about 10-12 mph. This is going from a complete stop to actual sailing without pedaling. Generally, the wind is mostly used to "assist" in combination with pedaling.