Energy Transfer for Offshore Wind Energy

Offshore wind energy has been demonstrated as a viable technology for the decarbonisation of UK power, however there are significant challenges in the transmission of this energy to shore. One of the significant challenges of floating wind power is the dynamic cabling, where mechanical stresses on the electrical connection can result in fatigue and early dielectric failure. Currently, issues in the electical cabling results in 47% of failures and this is expected to
increase as larger wind turbines are installed further apart, further from shore and in deeper water, all of which increase the forces applied to the cable. The project is to investigate three potential technology solutions for the realisation of a collection network between off-shore wind turbines and a centralised collection point that will enable a reduction in the installation cost of an offshore wind farm. This will facilitate the creation of larger scale wind farms
offshore, enabling the deployment of higher power generators.
The research hypotheses to be investigated are:
1. Understanding the move to higher voltages in the interconnect, including the move to MVDC or low frequency AC. This has the potential to reduce the mass of copper required in the cable, offering increased flexibility of the interconnecting cable and the possibility of floating cables.
2. Understanding the potential use of superconducting cables in electrical systems, where the switching frequency of power electronic converters is present. The AC losses from the ripple currents in the DC power at kHz is not known, the move to superconducting cables supports the move to higher voltages and lower frequencies, giving greater flexibility in system design.
3. Wireless power transfer has been demonstrated over short and medium range applications, such as car charging. Whilst the current demonstrations do not presently meet the efficiency of a hardwired system, the significant reduction in installation costs and the removal of a significant failure mechanism. This is the first consideration of wireless power transfer at the proposed power levels and distances, offering an opportunity for a significant research contribution.
The proposed PhD project will consider the potential solutions to the hypotheses above and compare these to the existing flexible AC cable solution that is used for offshore wind farms. Small scale laboratory demonstrators will be used to validate the mathematical modelling of the different potential solutions in the second year, using the experimental facilities available in the Department of Engineering. The validated models will the be used to
identify the optimum power transfer system for use in offshore wind networks, in terms of the efficiency, capital expenditure and reliability, which will be inferred from mathematical foundations and physics of failure data from the literature.
The later stages of the project will be to implement the optimum solution in a laboratory based multi-kW power transfer system. This stage of the project has the potential to link to other Aura funded PhDs at Durham, including the MVDC wave energy integration project and to use simulated wind turbine facilities. This will ensure that the power provided to the transfer system is representative of a real system, including voltage transients caused by switching of devices, ensuring relevance of the data to the wind community. The testing has the potential to include support from the Hardware In Loop capability in the University, that can mimic the behaviour of the collection network and wider distribution grid.

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.