A fully-variable transmission designed to survive

As the demand grows for ever larger wind turbines, gearbox technology struggles to keep pace with the torque demands placed upon the transmission and the increasingly stringent demands of grid operators.

Digital Displacement® technology has been demonstrated at 1.5MW and 7MW scales, providing a fully variable transmission designed to cope with the off-shore environment with a 25 year service life.

In April 2014, Artemis’s parent company Mitsubishi Heavy Industries (MHI) joined up with the pioneering Danish company Vestas to form a new joint venture company dedicated to offshore wind turbines – MHI Vestas Offshore Wind. Artemis is proud to be part of this exciting development.

HydraulicsWorking with MHI, Artemis has now progressively scaled Digital Displacement® technology to the stage where it’s ready to challenge wind-turbine gearbox and direct-drive transmissions on cost, performance and scaleability.

Because of their legendary toughness and unrivalled power to weight ratios, high-pressure oil-hydraulic machines have long been considered for this job. However, until the development of  Digital Displacement® technology, the low part-load efficiencies of conventional hydraulics have blocked access to the wind market.

The use of two generators further enhances system efficiency, by allowing unrequired capacity to be taken offline in low and moderate winds. Because of the inherently balanced load distribution and pressure limiting nature of hydraulic machines, the transmission is extremely robust. The DDP and the DDMs are built in modular fashion and most components can be swapped out from within the nacelle using the internal crane.

In 2011 Artemis successfully tested a prototype 1.6 MW wind-turbine transmission on the purpose-built energy-recirculating test-rig (shown above) which is able to simulate variable wind conditions.  This project, which built upon earlier work supported by Carbon Trust, was part financed by DECC (Department of Energy and Climate Change).

Artemis is now working with Mitsubishi on the detailed design of multi-megawatt class wind-transmissions for offshore application. This stage of the work is supported by the Technology Strategy Board (TSB).

Since the beginning of 2013, the first Digital Displacement® transmission to be installed in a wind turbine has been operating in a retrofitted 2.4 MW MWT100 wind-turbine at Mitsubishi’s in-house test-site in Yokohama.

The first 7 MW transmission has been installed for testing and evaluation at Scottish and Southern Energy’s Hunterston offshore wind turbine test facility, on the Ayrshire coast near to Glasgow.

The second 7 MW transmission will be incorporated into a floating wind-turbine off the coast of Fukushima. This is part of the ambitious FORWARD ‘floating offshore wind farm demonstration project’.

Please follow one of these links to download a brochure on the Artemis Digital Displacement® Wind-Turbine Transmission or a brochure on the Mitsubishi-led, TSB-supported Efficient Offshore Wind Programme.

Hunterston 2014-12-29-08-00
Site view near office

Many of the ideas behind the Artemis wind-turbine transmission were published in1984 in a seminal paper by Stephen Salter and Matthew Rea. Please follow this link if you would like to read Hydraulics for Wind.