Deployment predictions for floating offshore wind continue to soar. By 2050, DNV predicts floating offshore wind will generate 264 GW or 15% of all offshore wind energy
On the O&M side of things, based on evidence generated from a series of industry engagements, BVG Associates estimates the operators of a future 1-GW floating windfarm with 70 turbines would need to plan for at least seven major component exchanges per annum, in early post-warranty years.
At a cost of millions of euros per tow-back, this means the practice of towing back to port is not scalable.
When floating turbines need a major component exchange, we have only two options: we either service the turbines onsite or tow them back to port.
Let’s examine both scenarios a bit more closely.
Onsite crane floating-to-floating, no matter how it’s configured, would require dangling heavy components on a wire – a practice loaded with high risk and safety concerns.
Tow-back (tow-to-port or tow-to-shore) is the only option we have today. At a cost of millions of euros per tow (actual cost + loss in AEP), coupled with projected volumes, O&M service budgets based on tow-back are poised to go through the roof.
Despite there being only a handful of floating offshore wind turbines in operation today, we have already seen several major component exchanges requiring a tow-back. Nothing wrong with this – it’s the only option we have.
Apart from the obvious logistical issues and port availability, perhaps the most challenging effect of the tow-back practice is considerable downtime and commensurate loss in energy production.
The extraordinary rise in cost – and loss of income – associated with this approach boggles the mind.
While I certainly feel the pain of those dealing with unplanned wind turbine failure, all of this does beg the question: why on earth would tow-back be considered a viable option for the future?
Will the turbines of tomorrow require substantially fewer major component exchanges? Perhaps, but I wouldn’t count on it. Turbine reliability may be improving, but there is always a trade-off between reliability and cost.
The dream of reliability and commodity pricing for wind turbines is, in fact, just a dream.
Given the cost and enormous volumes projected for floating wind, the industry would be well-served to sharpen its focus on installation and O&M technology advances designed with floating wind in mind.
Now is the time to put promising onsite solutions through their paces – before the jump to industrial scale.
Note: BVG Associates estimate the failure rates of major components including blades, generators and drive train is in the order of 11% per wind turbine (approximately 2% per MW) per annum in the first five years post-warranty for first generation offshore turbines in the North Sea (installed and operating by 2020).
Taking a conservative view that modern turbine technology (15-MW scale) improves the per-MW failure rate by keeping the per turbine rates constant, then a future 1-GW floating windfarm of 70 turbines would plan for at least seven major component exchanges per annum in those early post-warranty years. This does not include complications that may be introduced by the floating foundations themselves.
*Julian Brown is board chair at SENSEWind
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