Governments around the world are reviewing the design of their energy markets, focusing on incorporating more renewables, in particular wind energy, that can add value to markets and economies.
This market transformation is what has accelerated the growth of offshore wind around the world, and the industry continues to grow. New markets in Latin America, Asia and Africa join the existing industry giants of China, the US, Europe, India and Brazil. As a result of this momentum, wind energy is now one of the cheapest forms of electricity and energy in many markets. Within these developments there is increasing emphasis being placed on offshore wind. Indeed, by 2023, offshore wind energy is expected to account for one quarter of world wind generation.
However, for all the positives of this growth, there are important safety considerations that are vital to the future success of offshore wind that to date have been kept on the margins of discussions.
The offshore wind industry is still a relatively new industry and like with other great sources of energy and electricity, there are risk factors involved. In particular, wind farms depend on the cables that deliver power back to shore and handle communications between turbines. Damage to these subsea cables is a huge risk to offshore wind farms. The renewable energy market needs to take subsea cable vulnerability seriously in order to ensure the success of the wind farm industry in future years.
Understanding subsea cable threats
The threats to subsea cables are varied, including cables being struck by boats and anchors, loss of burial and the breakdown of cables through flashover and arcing.
A significant threat is posed by shipping activity. In water depths less than 200 metres, typical around many offshore farms, an estimated 70% of all cable faults are caused by boating, fishing and anchoring activities. Cables can be easily snagged by fishing trawlers and nets. Large anchors being dragged through the sea bed can damage cables.
Loss of burial is another key issue. Burying cables protects against many external threats, but in many subsea areas burying cables is impossible – such as coral reefs. This can make cables vulnerable to stress and fatigue or other damage caused by the environment. Even where cables are buried, sea bed currents can expose cables and cause internal faults.
Subsea cables are also at risk from flashover or arcing, which can cause internal burning of the cables. These sorts of internal faults are particularly problematic as they aren’t always obvious to operators. Moreover, it’s difficult to send operators to monitor cable faults. Cables can be miles offshore and it is difficult to get down to the sea bed.
Therefore, what can be done to resolve this issue?
Subsea cable monitoring with DAS
It’s impossible to prevent underwater currents and the damage they can cause. However, it is possible to monitor cables more accurately and offer more proactive maintenance. Currently, subsea cable route surveying is the only option, but this is expensive, time intensive, and doesn’t provide continuous real-time monitoring.
DAS is the clear solution for this issue. By providing a way to monitor entire offshore and subsea cable networks, faults can be detected remotely. DAS can detect disturbances and pinpoint the exact location of the fault – allowing operators to respond decisively and minimise downtime and repair costs. This is clearly better than only finding out about an issue when significant problems occur.
Without monitoring technologies such as DAS, it is very difficult for operators to assess the integrity of offshore subsea cables. As the market for offshore wind farms continues to grow, solutions like DAS need to become an integral part of operations. Doing so will, in turn, protect renewable energy assets around the world.