Wind energy was the fastest growing power source at the starts of the 21st century, yet wind-driven mills and pumps, and nautical sails for transport, were, along with waterwheels, the first mechanical devices to power industrial production. The advantages of harnessing wind energy are obvious; it is free, clean and widely available. This unit explores the Wind as a potential source of useable energy. This study unit is just one of many that can be found on LearningSpace, part of OpenLearn, a collection of open educational resources from The Open University. Published in ePub 2.0.1 format, some feature such as audio, video and linked PDF are not supported by all ePub readers.