The capability of the WITT Wave Energy Converter to generate megawatts of offshore power at a competitive LCOE

4c4caf34-1e5b-49fc-a280-666f4f56ea80

Closed

EPSRC
EPSRC
EPSRC
EPSRC
EPSRC

£428,005

May 4, 2015

Aug. 31, 2016

The potential for harnessing significant amounts of clean renewable energy from ocean waves is vast. Commitments made
by the UK government and others to tackle climate change require an expansion in development and deployment of
renewable technologies and it is widely recognised that ocean wave energy will play an important role in meeting future
targets for the reduction of carbon emissions. Whilst significant advances have been made over the last 35 years in
developing new ideas aimed towards producing robust and economically viable wave energy converters (WECs) there
remains no clear consensus on future direction of design and operation of WECs.
In addition to supporting existing concepts, it is important that promising new ideas for wave energy conversion continue to
be explored. It is widely accepted that there are two key elements to a successful WEC design. First, the design should be
driven by fundamental theoretical principles of wave energy absorption as these ultimately determine the capacity for
power conversion. Second, prospective designs must take account of the significant engineering challenges that arise
when operating in harsh marine environments.
In a recent paper "A submerged cylinder wave energy converter" Crowley, Porter & Evans, Journal of Fluid Mechanics,
2013, vol 716, (hereafter CPE) advocated a WEC design which sought to address these two demands. In particular, the
design was assumed to use an internal power take-off system consisting of a pendulum rotating on a horizontal axis whose rotation was damped to produce power. Such a design benefits by its isolation from the marine environment, mechanically
robust by relying on few moving parts and free from end-stop problems associated with over-excitation of the device. A
combination of theoretical and numerical results demonstrated that the device of CPE extracts significant power over a
broad range of energy-dense wave periods. Indeed, a mean capture factor more than double any existing WEC of its type
was predicted.
The WITT developed by WITT Limited under whom this TSB grant is being led is closely related to the device conceived in
the work of CPE. Instead of a linear device working in surge/pitch modes of motion enclosed within a long cylinder, the
WITT is a device designed for use in buoys. It not only converts power in surge and pitch modes but also in sway and roll.
The WITT has been developed by specialists in gear transmission systems and has been shown to have high efficiency in
conversion of kinetic to electric power. It is scalable and robust.
The project being led by WITT includes partners specialising in mooring systems and marine deployment, power take-off
design and manufacture and experimental methods including wave tank testing.
In Bristol, the project will develop a theoretical model for the operation of the WITT WEC device as a spherical buoy either
floating or submerged, to include effect of the mooring lines, the device and its interaction with a model sea state and the
internal power take-off system. The work will be based on the earlier work of CPE, with changes implementated to account
for the revised converter geometry, mooring line configuration and power take-off system. After verification tests have been
completed, an optimisation method will be applied to determine parameters for optimal power conversion for WITT devices
over a range of physical scales.
The work will develop in tandem with other partners on the project, in particular in developing the optimal mooring system
and through the validation of theoretical predictions by the experimental work performed in Southampton.
The successful completion of this project will result in a set of experimentally-validated theoretical results for a WEC design
with the potential to be developed a larger scale and eventually to full scale commercialisation.

Potential Impact:
The academic aspect of this work is in developing a greater understanding of the system dynamics (mechanical and
hydrodynamic) and performance optimisation of a wave energy converter design which incorporates the disruptive,
patented and internationally awarded technology - The WITT. This work is vital in designing and operating the technology
to its full potential, yielding the greatest operational performance and supporting the consortium in order for them to achieve
their commercial aspirations.
Who will benefit from the research?
1. The work will be of key interest to (theoretical and experimental) researchers in engineering (mechanical, naval
architecture, renewable
energy and dynamics).
2. Equipment suppliers to the maritime sector.
3. The wider engineering sector, who may benefit from such a device.
How will they benefit from this research?
1. The lead company, project partners and their suppliers will potentially benefit from increased sales and increased added
value to their products.
2. Policy makers, through the development of quantitative results on the performance of wave energy conversion systems.
3. The broad thrust of new knowledge and academic thinking will also increase the two Universities relevance to a greater
number of businesses focused on energy harvesting. This in turn will potentially increase its volume of consultancy and
applied research interactions not
only in the UK, but also across the EU and beyond. Increased interaction with a greater number of industry players also
continues to increase the attractiveness of the Universities in this proposal (Southampton and Bristol) for future students,
which is now a critical
driver in an increasingly competitive market place resulting from increased tuition fees.