 The overhead of regulation (whether before the generator via gear reduction or after generation by electrical means) is high in proportion to the naturally-derived energy available.New generator designs such as the asynchronous or induction singly-fed generator, the doubly-fed generator, or the brushless wound-rotor doubly-fed generator are seeing success in variable speed constant frequency applications, such as wind turbines or other renewable energy technologies.These systems thus offer cost, reliability and efficiency benefits in certain use cases.