In January 2013, test operations of an innovative wind power generation facility with a hydraulic drive train began at MHI Yokohama Dockyard & Machinery Works.
The adoption of wind power has skyrocketed in recent years due to global demands for renewable energy, and MHI has now developed the world's first hydraulic drive train to use Digital Displacement® Transmission (DDT*) technology. The product was created during the development of a new hydraulic drive train system for offshore wind turbines, a project which began in September 2011 with support from the New Energy and Industrial Technology Development Organization (NEDO). This operation testing will accelerate the realization of the world's largest 7 megawatt-class wind power generation facility.
(*) Digital Displacement® Transmission is a registered trademark of MHI.

An in-depth discussion of the hydraulic drive is available in the “hydaulics \& pneumatics” website Hydrostatic Transmissions: A Power Play in Wind Turbine Design

Key points are discussed here:
- A nacelle-mounted hydraulic drivetrain could be thousands of pounds lighter than the mechanical gearboxes used today.
- Today’s off-the-shelf hydraulic components are practical for wind turbines with outputs up to about 500 kW.
- Hydraulic drivetrains would decouple torsional vibrations generated in the rotor hub from the generator and boost reliability in the bargain.

Resources: Eaton Corp., wind turbine hydraulics info

Several wind turbines could generate power to a single gound level electricity generator:

Note that the electricity generator could be switch off when no demand and replaced by an air compressor/liquefier. LN2 could be stored on site and vaporized when needed in a hydraulic turbine powering the electrical generator.