Performance predictions of one-way energy capture by an oscillating water column device in Faroese waters

Here we investigate the performance of an
experimentally tested model-scale oscillating water column
(OWC) device, modified to only exploit half of the wave
cycle. To do this we integrate a passive valve system into
the OWC chamber which ensures a free connection to the
atmosphere either on the up- or the down-stroke, but sends
the flow through the orifice plate representing the full-scale
air turbine, on the other half-cycle. The performance of the
experimental model is evaluated from the absorbed power
of the OWC chamber. The absorbed power is computed
from the measured pressure drop across an orifice plate
and the internal surface elevation inside the chamber.
Perhaps surprisingly, the device can absorb more energy
near resonance when exploiting only half of the cycle than
when the full cycle is exploited. Since a one-way turbine
is typically much more efficient than a Wells, impulse,
bi-radial, or other self-rectifying turbine, this suggests a
significant potential gain in overall efficiency from wave
to wire. The obtained performance characteristics of the
model-scale device are extrapolated to a proposed full-scale
device size, and its performance is evaluated in Faroese
waters. The performance of the proposed full-scale device
is presented in terms of the annual absorbed power.