Offshore wind design

Lifespan – designed for a long versatile life, not short-term gains

There are interesting parallels between the servitisation concept now being used increasingly to add long-term value in industry and our flexible engineering design approach that optimises the full-lifespan of a new wind farms.

( Text content written by Twenty6 for Diego Cocco, LIC Energy )

Planning early for a prosperous life

Design for life extension (LE) is a concept that is moving rapidly into the offshore wind industry lexicon. However, its full implications are not always easy to see.

For example, the term doesn’t automatically mean that you have to extend the life of renewable energy assets working in a tough offshore environment. But it does open up new opportunities to streamline all aspects of design that we now know can cause costly future problems.

Importantly, it also introduces a much more strategic approach to whole lifecycle costs, maintainability and retrofitting needs; the real meaning of a robust design and the value of quality.

Data open up incremental gains

Design for LE capitalises on the fact that evolving monitoring and operational data analysis technologies are making it increasingly possible to identify wide revenue gaps between the theoretical life of a structure and the real stresses, strains, and fatigue damage it may have suffered in service.

The point I would like to make is that going a step further still, this is also an ideal opportunity for us to systematically eliminate critical life-driving details at the earliest design stage and move towards a more rewarding, sleek design philosophy.

One implication of this is that automatic decommissioning for structural reasons is no longer an inevitability for assets that still hold a high intrinsic value.

Of mice and men –  and wind turbines

As with the human body, science and technology are now turning what used to be regarded as the twilight-years of aging offshore wind farms structures into extremely cost-effective, productive periods of operation. This is mainly because original designers tend to be very conservative with their calculations and left plenty of spare fat on the carcass that we can exploit now.

At the very least, expensive assets can be fully-optimised to meet changing conditions. The watchword is versatility.

One upshot is that it is now feasible to design out the potential week spots that might otherwise have high long-term O&M costs, even if this means slightly higher costs in the early stages today.

For example, welded details known to be vulnerable to corrosion or mechanical stress can be revised to increase their structural strength and improve their accessibility for inspection and repair/retrofit. What this may compromise on short-term gain, particularly in a slight penalty on the use of steel, is more than made up for in terms of through-life savings.

Spoilt for choice?

In short, we are learning how a little extra but efficient effort put in today can result in a more rational design with long-term benefits, including less onerous and more efficient O&M requirements in the years ahead.

The sleek design philosophy offers options and future choices to extend safe and profitable operation at a point when many owners are most likely to welcome the additional power and revenue-generating capacity for relatively little extra retrofitting outlay.

From the operator’s perspective

Because design for LE is able to help rationalise maintenance and monitoring at the end of each operational year, engineers know precisely how structures are performing. This gives offshore wind farm operators three very clear bottom-line benefits: –

  • Reassurance that the best retrofitting decisions can be made at the end of asset life, or earlier

  • Minimised vulnerability to environmental loads that can affect structural integrity

  • Because of a more robust and rational design, the number of critical design details is minimised

Sensitive sensoring

Under the conventional model, extending the sensoring of wind turbine generator foundations to integrate an increasingly high number of details also increases the complexity of remote monitoring systems. Data post-processing and interpretation becomes more difficult and impractical.

One of the beauties of design for LE is that structures can be designed deliberately for easy monitoring, leading in turn to more rational, tailored and optimised maintenance programmes.