Artemis Digital
Displacement® Technology can help to reduce the cost
of electricity from ocean waves and tidal-currents
Pelamis prototype
at European Marine Energy Centre, photo courtesy of Dr Richard Yemm of
Pelamis Wave Power Ltd
To
reduce risk at the prototype and development stages, the designers of
wave energy systems generally use industrially proven components to
transform very large, ever-changing, bi-directional forces into
constant-speed torque in the shafts of electrical generators. These
‘power-take-off’ systems are a natural application area for
high-pressure oil-hydraulics and Digital Displacement® technology
evolved out of efforts that started around 30 years ago to design
better hydraulic machines for wave energy devices.
At any given
moment, a wave, wind or tidal-current device is statistically most
likely to be generating at below its ‘power limit’ or nameplate-rating.
At such times the efficiency of the power-take-off energy
transformation process is critical to reductions in the cost of
delivered electricity.
Digital
Displacement® technology provides the potential to create marine-energy power-take-systems
that have high part-load efficiencies, outstanding controllability,
short-term energy storage, and the possiblity of providing short-term
reverse
power-flows to improve power
capture bandwidth in
broad-spectrum sea-states.
In
2001, a UK government
report on the R&D priorities of wave energy
identified the need for hydraulic motors
that have low part-load losses. In 2006, with the
help of funding from Carbon
Trust
and in partnership with Ocean Power Delivery Ltd (now Pelamis Wave Power
Ltd) Artemis built and tested a Digital Displacement® "Efficient
Hydraulic Motor for Marine
Renewable". This was the prototype for future renewable energy
generator drive-motors and the beginnings of Artemis's direct
involvement in wave energy.
Artemis high-efficiency
generator drive-motor on test.
The bright aluminium-cased 125 kW Digital
Displacement® motor, barely visible at
knee-height, is dwarfed by the generator above it and by the
test equipment around it.
The
research and development that led to the successful demonstration
of Digital Displacement® machines took place at the University of
Edinburgh. The Edinburgh Curved Tank is the latest facility
built there for small-scale experimental wave energy work. You can find
out more about the historic wave-energy work and about some of the
research at the University into
high-pressure oil hydraulic machines if you follow this link.
