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|Title: ||On the configuration of arrays of floating wave energy converters|
|Authors: ||Child, Benjamin Frederick Martin|
|Supervisor(s): ||Venugopal, Vengatesan|
|Issue Date: ||22-Nov-2011|
|Publisher: ||The University of Edinburgh|
|Abstract: ||In this thesis, certain issues relating to a number of wave energy absorbers operating in
the same vicinity are investigated. Specifically, arrangements of the devices within such
an array are sought, such that beneficial hydrodynamic interference between members
is exploited and unwanted effects mitigated.
Arrays of `point absorber' devices as well as converters with multiple closely spaced floats are modelled and a frequency domain hydrodynamic solution derived. This is
implemented as efficient computer code, capable of producing the full linear wave theory
solution to any desired degree of accuracy. Furthermore, the results are verified against
output from the boundary element code WAMIT.
Initially, detailed analysis of an isolated absorber is conducted, with motion
responses, forces, power output and velocity potentials at the free surface computed
for a range of different device specifications. Elementary examples of arrays are then
used to demonstrate the influence of factors such as device separation, wave heading
angle, number of devices and array configuration upon collective performance.
Subsequently, the power output from an array of five devices is optimised with
respect to its layout, using two different routines. The first is a new heuristic
approach, named the Parabolic Intersection (PI) method, that efficiently creates array
con figurations using only basic computations. The second is a Genetic Algorithm (GA)
with a novel `crossover' operator. Each method is applied to maximise the output at a
given regular wave frequency and direction under two different power take-off regimes
and also to minimise power in a third, cautionary example. The resulting arrays are
then analysed and the optimisation procedures themselves evaluated.
Finally, the effects of irregular seas on array interactions are investigated. The
configurations that were optimised for regular wave climates are assessed in a range of
irregular sea-states. The GA is then used once more to create optimal array layouts for
each of these seas. The characteristics of the arrays are subsequently examined and the
influence of certain spectral parameters on the optimal solutions considered.
The optimisation procedures were both found to be effective, with the GA marginally
outperforming the PI method in all cases. Significant positive and negative modifications
to the power output were observed in the arrays optimised in regular waves, although the
effects weakened when the same arrays were subjected to irregular sea-states. However,
arrays optimised specifically in irregular seas exhibited differences in net power output
equivalent to over half that produced from the same number of devices in isolation.|
|Sponsor(s): ||SuperGen Marine Consortium|
Engineering and Physical Sciences Research Council (EPSRC)
|Keywords: ||wave energy|
|Appears in Collections:||Engineering thesis and dissertation collection|
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