Integration of wave and offshore wind energies

Wave energy has the potential to generate 70 TWhr
annually, approximately 20% of the UK energy
requirement. The technology for the mechanical
conversion of wave motion to electrical energy has
been developed over the past forty years, however the
electrical integration with the power network is less
advanced. One potential solution is to consider the
positioning of wave energy converters close to
offshore wind farms to take advantage of the electrical
infrastructures of the wind farm in terms of the
collection network and shore connection. Power
electronic systems are required to enable the
connection of multiple wave energy converters to form
a system and then integrate this with the electrical
system of the wind farm.
Wave energy conversion offers a series of unique
challenges for the power electronics in comparison to
those found in wind turbines. The most significant
being the very high peak-to-average ratio and the short
timespan cyclic nature of the generated power. This
short timescale variation in the power level places
significant challenges in the synchronisation of the
generated power and the grid connection. The
proposed solution to this is the development of a novel
transformer less power take off system that can be
incorporated into an individual wave energy
converter, that can operate at medium voltage DC
(typically, plus/minus10 kV) that is low weight and low volume,
enabling them to be integrated into an individual
floating wave energy converter.
The converter will be developed using wide bandgap
semiconductor devices, which offer significant
performance advantages over conventional power
electronics technologies and open up a range of novel
topologies that are ideally suited to this application.
The MVDC power from the individual wave converters
will be series connected to form a string, with a
collection point located at a wind turbine. The DC
nature of the power enables the integration of wave
energy converters to form strings to a common
collection point that will be located at the wind turbine
and take advantage of the existing physical and
electrical infrastructure. The DC energy can then be
inverted at the wind turbine to match the power
generated by the wind and enable grid connection.
The integration of the electrical power from the string
of wave energy converters with the existing wind
power collection network will be simulated using OPAL-RT/RTDS systems to simulate the real-time grid
response to the short-term cyclic power variations
from the wave energy converters. The existence of a
real-time simulation platform provides an opportunity
for hardware-in-the-loop testing of the prototype
converter coupled with an exemplar offshore wind
collection network. It will also provide the means for
evaluating control algorithms for ensuring continuous
grid code compliance from the coupled wave-wind
energy system. This novel approach to the integration
of wave power with existing offshore infrastructure
opens up new opportunities in the development and
integration of wave energy at a larger scale.
Methodology
The project will utilise a range of computer simulation
tools, including SPICE and PLECS, to study the
fundamental operation of power converters to
optimise the topology, understand the challenges of
the short term transients in power and voltage that are
unique to wave energy and explore the challenges of
integration at a grid connect level. The findings from
the simulations will be used to construct and optimise
a demonstrator unit in the laboratory, which will then
be connected to the real time simulation system (OPAL
RT) to understand the interaction with the power grid.
Analysis of the operation will be undertaken using
MatLab.

The Aura CDT will produce offshore wind specialists with a multi-disciplinary perspective, and will equip them with key skills that are essential to meet the future sector challenges. They will be highly employable due to their training being embedded in real-world challenges with the potential to become future leaders. As such, they will drive the UK forward in offshore wind development and manufacturing. They will become ambassadors for cross-disciplinary thinking in renewables and mentors to their colleagues. With its strong industrial partnership, this CDT is ideally placed to produce high impact research papers, patents and spin-outs, with support from the Universities' dedicated business development teams. All of this will contribute to the continued strong growth of the offshore wind sector in the UK, creating more jobs and added value to the UK economy. Recent estimates suggest that, to meet national energy targets, developers need >4,000 offshore wind turbines, worth £120 billion, over the next decade.

Alongside the clear benefits to the economy, this CDT will sustain and enhance the UK as a hub of expertise in this rapidly increasing area. The UK has made crucial commitments to develop low carbon energy by 2050 and this will require an estimated ~£400m UK RDI spend per year by 2032. Whilst the increase in R&D is welcome, this target will be unsustainable without the right people to support the development of alternative technologies. It is estimated that 27,000 skilled jobs, including in research, will need to be generated in the OSW sector. Of these, ~2,000 are estimated to require HE Level 7-8 qualifications. This CDT will directly answer the higher-level leadership skills shortage, enabling the UK to not only meet these targets but lead the way internationally in the renewables revolution.

Industry and policy stakeholders will benefit through-
a) Providing challenges for the students to work through which will result in solutions to pressing and long-term industry challenges
b) Knowledge exchange with the students and the academics
c) New lines of investigation/ revenue/ process improvement
d) Two-way access to skills/ equipment and training
e) A skilled, challenge focused workforce
Society will benefit through-
a) Offshore wind energy that is lower cost, more secure and more environmentally friendly, with a lower impact on precious marine eco-systems.
b) Engineers with new skillsets and perspectives that can understand environmental constraints
c) Skilled workforce who are mindful of the environmental and ethical impact
d) Graduates that understand and value equality, diversity and inclusion

The research projects undertaken by the Aura CDT students will focus on projects with a strong impact. The 6 themes have all been chosen after extensive industrial consultation and engagement that accelerated after the formation of the wider Aura initiative in 2016. The collaborative approach which has shaped this proposal will be continued and enhanced through the life of the CDT to ensure that it remains aligned to industry priorities.

The interdisciplinary nature of the OSW industry means that there are a wide range of stakeholders including large and small companies who are active at different stages of OSW farm development. These industry players will help ensure the training and experience provided in the CDT addresses the range of challenges that the industry faces.