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The University of Southampton

Optimising marine cable design to maximise power transfer from wind farms

Published: 20 May 2021
Marine High Voltage Cables
Marine High Voltage Cables transfer energy from wind farms to land

Pioneering research and consultancy at the University of Southampton is optimising the design of high voltage underwater cables that deliver renewable energy to our shores.

A multidisciplinary team, including experts in Civil, Maritime and Environmental Engineering, are driving findings that will maximise power transfer and save money in the delivery of future energy. 

The research could also lead to a much better understanding of how climate change may be affecting ocean bottom temperatures and, in turn, biological and geochemical processes at the seabed – which are critical to the health of the oceans. 

The projects came about thanks to introductions organised by the Southampton Marine and Maritime Institute (SMMI)

Marine High Voltage Cables (MHVCs) are buried under seabeds around the world. MHVCs for a typical 1 gigawatt windfarm cost about £400 million to design and install, with operation and maintenance costs of several millions of pounds every year. 

Professor Justin Dix, of Ocean and Earth Science (OES), explains: “MHVCs primarily operate two ways. Either transferring power between one country and another, for example, hydroelectric power from Norway to Denmark or nuclear power from France to England, or to bring power from our proliferation of windfarms to land. As we explore other sources of renewable energy like tidal power and wave power, the power will need to be brought to land in the most efficient manner. 

“If you can better understand the environment the cables are in, and therefore effectively model how heat dissipates away from the cables, you can optimise cables and reduce costs significantly.” 

Southampton researchers were the first to establish that cables under the sea floor disperse heat through a combination of convection and conduction, and that the ratio of one to the other is determined by a combination of the permeability and thermal conductivity of the sea bed. 

Professor Tim Henstock, of OES, says: “Properly understanding these processes allows us to modify conventional ratings approaches to be more applicable to the marine environment.” 

Professor David White, of the School of Engineering, adds: “We are developing a better understanding of not only how to measure how these parameters, which vary in space and through time, but also how they are altered by the different cable burial processes – via jetting, trenching, ploughing or even cutting with a huge rock-saw.” 

Historical research has also been repurposed, with the application of 3D Chirp for post-installation cable burial surveys. 

3D Chirp is a high-resolution acoustic system that was developed by some members of the group and colleagues from the Institute of Sound and Vibration Research in a project led by Professor Jon Bull, from OES, in the early 2000s. The system is capable of tracking cable routes in three-dimensions and providing critical data input for cable operation. 

The system is now operated commercially through a company called Sand Geophysics, set up by a group of OES alumni, and is not only being used for cable detection but also for seeking out unexploded ordnance and other man-made objects ahead of the construction of offshore infrastructure. 

Looking to the future, the research is also taking a different turn – to understand temperatures at the bottom of the ocean. 

Professor Dix says: “The cables strongly record the seasonal variation in ocean bottom temperatures. We think we can back-calculate ocean bottom temperatures from the catalogue of data we have from the last few decades. Ocean bottom temperature is one of the least studied ocean parameters on the planet.” 

Read the full article in the latest edition of Re:action, the University’s research and enterprise magazine.

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