Power cables may well be invisible once they are laid, but their reputation is all-too evident when it comes to offshore wind — and not in a good way. There are several reasons why cabling is widely perceived as the ‘problem child’ in the sector.
Scott Macknocher, general manager of UK engineering, design and technology company Enventi, points out that the problems offshore wind is having with cable installation are worse than might be expected, given that cabling is an established activity in other sectors, with well-known challenges and risks.
However, he acknowledges that the circumstances are different. "Our analysis appears to show that the majority of problems lie in the design of cable interfaces and the operating methodologies that are specific to offshore wind," he says. According to Macknocher, part of the problem is the mindset that has developed over the recent past, whereby recurrent problems surrounding cables have been accepted to such an extent that they are now seen as the norm.
"We don’t think these problems are particularly difficult to overcome, but there seems to be a resistance to change, possibly explained by the belief that the cost of cable installation only represents around 2-3% of project capital expenditure," he adds.
In practice, as Enventi’s analysis shows, the direct cost of cable installation is closer to 5% of the total and can rise to as much as 8% when indirect but related costs are factored in.
According to Jatin Sharma, partner at offshore insurance specialist GCube, cable management and installation is a regular contributor to the cost overruns and schedule delays that lead to claims in the offshore wind sector.
Sharma says that changes in approach are needed. Offshore wind is under political pressure to achieve significant cost reductions and wean itself off the hefty subsidies it currently relies on over the course of the next five years. "And yet we are looking at 20-25% overruns, amounting to perhaps one to two-and-a-half years."
Part of the problem, he says, is the interdependency of the supply chain and reliance on just a few major cable suppliers. But he also points the finger at an excessive emphasis on saving money and doing the job at the lowest possible cost. "This has been the case with a lot of new entrants trying to take a role, and we have seen some cable contractors go bust as a result. The cost focus also undermined procurement strategy."
The installation phase would benefit from cable contractors being more involved in the design phase of projects, where they could give valuable input, Sharma says. But this is not happening often enough.
It is also worrying that lessons are not being learned quickly across borders. "Germany is playing catch-up with offshore wind, but is now repeating the mistakes made by the UK, Denmark and the Netherlands," Sharma says.
An obligation on developers to source a certain amount of equipment and services from companies located in the same country as the project — the so-called local content requirement — can be a powerful ally of offshore wind by creating jobs for a local workforce and drumming up business for local companies. But it also represents its Achilles’ heel when it comes to cabling. At times, Sharma observes, local contractors that do not have the appropriate offshore experience are being used, just because they are German.
Lack of experience
All observers agree that inexperience is a key factor when problems arise. There seems to be a direct correlation between inexperienced contractors, newly built cable-laying vessels with new crews, and cable failures. A similar link between local content requirements and project failures has also been noted. Most failures occur at the installation phase, although there are also some serial cable-quality issues.
Enventi’s Macknocher sees problems along the whole project chain, starting with contracting philosophies and continuing with cable-laying deadlines, that are underpinned by the unsuitability of some contractors to undertake large-scale projects. But many of the cabling difficulties being experienced fall outside the control of the installer and relate to poor upfront design based on an inadequate grasp of operational know-how.
Enventi has identified five major problems that result from poor project design at the outset. For a start, the interfaces between cables and related infrastructure —mainly turbines — are not well designed, and second, utilities tend to make contracts based on civil-contracting principles rather than a tried and tested offshore approach.
The third problem is the frequent unsuitability of contractors,which lack relevant experience or a full suite of burial equipment; this is often compounded by arbitrary requirements specified by clients with little consideration for what is realistic or achievable. Finally, a basic lack of understanding of cable installation operations completes the problematic picture.
Despite these factors, Enventi’s supply-versus-demand analysis does not show any significant constraints on inter-array cable installation up to 2020, says Macknocher. But export and interconnector cable installation may experience difficulties in coping with demand in the short term, he cautions.
With cables playing such a pivotal role in any offshore wind development, Enventi is taking a cautious view of the sector’s ability to deliver the likely pipeline of planned projects.
While the European Wind Energy Association estimates 40GW of offshore installations can be delivered by 2020, Enventi’s own 2020 European deployment forecast now stands at 26-27GW. That breaks down as 13GW in UK waters, 9GW in Germany and 5GW elsewhere.
The UK government believes there is potential for 40GW of offshore wind by 2030, and is aiming for 18GW by 2020.But Macknocher brands these targets "completely unrealistic given the challenges of Round 3 projects".
Naturally, the challenges facing offshore wind development go beyond the ‘Achilles’ heel’ of cables and cable installation. But there is little doubt that if there are no breakthroughs on cost, reliability and supply in this least-visible part of offshore wind projects, the sector’s ambitious plans for 2020, in Europe and beyond, could be compromised.