The sweet spot for hydraulic drivetrains: Midsized turbines

摘要

Hydraulic drives once held great promise for utility scale wind turbines because they allowed getting rid of the troublesome gearbox, a giant step toward greater reliability. The cost of power is one deciding factor, so few large hydraulic drives were built. One exception, Mitsubishi's Sea Angel in Japan, is slated for launch this year. But there are good reasons to give hydraulic drives a closer second look. "For instance, there is some compressibility in the fluid that prevents shock loading to the generator," says University of Minnesota and Mechanical Engineering Professor Kim Stelson. "And hydraulics equipment is lighter than the conventional equipment it replaces. Also, control is somewhat simplified. Controls in a conventional turbine are based on torque, a quantity that can be difficult to measure, although it can be approximated with current. But in a hydraulic transmission you measure it with pressure from the pump and that is more convenient." Also, costly power inverters could be eliminated.