Floating offshore wind turbines have the potential to be the next big breakthrough in renewable energy but they present significant technical challenges.

First, the benefits. Floating on water deeper than 60 metres provides a way of harnessing unused wind resource (approximately 80% of the world’s offshore wind is in areas where bottom-fixing turbines to the seabed is not economical). The high speed of winds further out at sea and potential to select optimal generation sites should increase offshore wind generation capacity and efficiency. Factor in larger turbines (and potentially many more of them) and the economics of floating offshore wind start to look good.

But higher wind speeds and further distances from shore also mean a harsher, more remote environment. Recent research by the University of Plymouth finds that the “survivability and reliability” of floating offshore wind turbines is one of the “major challenges of the technology”. That includes not only factors such as turbine fatigue and corrosion from salt water, but also new challenges such as the possibility of moorings breaking and collisions or beaching of turbines as a result, and the need to maintain turbines at greater distances.

The maintenance of cables carrying power to the mainland is also a key issue as these will be much longer and more expensive. So remote cable monitoring systems such as condition monitoring technology are expected to play an important role in making floating offshore wind a success.

Dr Andrew Dodds, interim chief executive at Megger, explains more: “When you look at some of the new concepts for floating wind farms, there is a set of problems for cables due to tidal flows. The cables are really in quite an unpleasant environment.

“There are tidal shifts, and flows which push sand, dirt and gravel against the cables, and clearly there is flexing. If cables are not installed to a certain standard they will suffer many problems.”

Part of the solution could be permanent installations of condition monitoring sensors that allow defects in floating offshore wind cables to be identified and repaired before they cause problems. Indeed, Megger is working on trials of technology which would allow detection of partial discharge and predictive maintenance of offshore wind inter-array cables of two to four kilometres in length.

Megger has also invested in Synaptec, a spin-out from the University of Strathclyde, that uses sensors to enable monitoring of cable junctions and terminations in offshore wind installations, providing real-time, high-quality data.

“The idea is to give much more insight into cable health for any pending failures,” explains Dodds. “The work is at an early stage, but I see us having solutions for permanent partial discharge monitoring in the future.”