The first generation of Canadian wind farms are on the edge of reaching their original serviceable life, leaving Independent Power Producers (IPPs) with an important decision to make on their next steps. Built, in most cases, to meet the lifetime needs of specific production agreements, these wind turbines are producing valuable and more-required-than-ever energy resources for communities across the country.
It’s a decision that must be carefully considered and prepared in advance, with economic, social, and environmental impacts at stake. Not to mention consideration of the alternative, the energy resources supplying the grid that would replace the power generation if the wind farm was to shut down.
The current landscape
In the earliest days of wind farms, it was common that PPAs (Power Purchase Agreements) were made for 20 years. It was, therefore, logical to align the engineering design life to support this timeline.
The first Canadian wind farm was established in 1993, a 52-turbine installation located in Pincher Creek, Alberta. In the years and decades that followed, every other Canadian province had wind farms built and generally connected to the local utility energy grid. So far, few wind farms have been repowered or have a PPA extension. Since a big push in wind power development occurred in the early 2000s, the question about what to do next is timely.
When properly designed, which is most of the time the case, wind farms can withstand extreme wind events and huge storm with a sufficient margin of safety for its entire lifetime. However, there are still unexpected natural events that have led to turbine failure. For example, a lightning strike can disable the intricate electrical components within the turbine, causing the unit to malfunction or even to set off on fire. Not to mention that bad designs have, on rare occasions, lead to failure and even to turbine collapse.
That said, where proper design and maintenance regimes have been implemented, the original 20-year timelines have stood up, allowing producers to meet the demands outlined in the original PPAs. A poor maintenance record rarely shuts the turbine down completely, but could significantly reduce its output, reducing the project profitability.
Evaluating an existing system
Fatigue is the feeling we experience after a long day. Each action we take slowly depletes our energy reserves, and when all added together, we end up feeling exhausted. Mechanical and structural components of a wind turbine behave quite the same. The wind blows in all directions, at varying speed and intensity, there are gusts and turbulences. Each wind event creates a small amount of deterioration on the blades, the drivetrain, the rotor, the tower, and the foundation. There are methodologies that allow us to calculate the deterioration created by every anticipated wind event. This per event deterioration is extremely small, but when we add all of the events together, the sum is determined. The resulting valuation determines how much life a given turbine, and its individual components, has left. This is fatigue calculation.
By conducting this evaluation, in alignment with the latest industry codes, standards and applicable practices, at or near the end of the farm’s engineered lifespan, it is determined how soon components will begin to malfunction, the scaled deterioration of the farm’s production, and the cost of rehabilitation or replacement at different timing benchmarks.
Wind turbines are evaluated as part of the regular system for maintenance along with rigorous site inspections. Experienced technicians or engineers could identify early deterioration and would be able to inform on the upcoming expenses associated with the turbine sometime without the needs for fatigue calculations. However, one item would still always remain uninspected, for the most part of it: the buried foundation.
Foundation engineers have always looked at the leaning tower of Pisa with a bit of fear. Scrutiny, and analysis of the foundations, should be the starting points of a decision-making process. It would be a huge red flag if the foundation analysis showed the foundation could not withstand more than it already has.
In the last few decades, the industry has evolved significantly. The codes, standards, practices and methodologies applicable now significantly differ from what they were twenty years ago. The importance of an up-to-date analysis on the foundations couldn’t be more justified.
Following the analysis, there are several ways to collect in-situ data from the foundations. That could be initially by doing visual inspection, coring, or NDT (non-destructive testing) on the concrete surfaces. It could also be by implementing a more robust SHM (structural health monitoring) program, involving instrumentations of the towers, and the foundations.
Using the Information to evaluate service life
Once the inspections and analyses are complete, the technical information could then be compiled and added to existing project information (economic, political, financial incentives) to fully appreciate the value of, at least, three potential options: leave the system as is and continue to run it, refurbish the system, or completely replace the system. Not to mention the end of life of the wind farm.
It is expected that the initial investment in a windfarm will already have been paid after 20 years of operation. If the life of the system can be extended without doing much, it’s a lot of direct profit a producer and its co-owners can make.
A refurbishment can still present a significant financial opportunity for the owner. While some components may need to be replaced, the extension of service life this replacement creates can generate a positive economic return. There have been significant upgrades in turbine technology since the first generation of wind farms were built, so there is an economic case that could be made for repowering a system, replacing the turbines with or without keeping the tower or the foundations. That can depend on whether the towers and/or foundations need to be replaced, but the opportunity is still there. Some jurisdictions also offer fiscal incentives for replacing turbine technology, which can also strengthen the financial opportunity.
In any case, the return on investment the engineering studies will bring to the projects could be significant. The studies would also be required to convince all project stakeholders (owner, lender, insurer, utilities, community) that, whatever the path followed, the project is safe and does not represent a higher risk than any other wind farm.
The environmental cost of decommissioning
One of the challenges with older clean energy technologies is ensuring they have a minimal impact on the environment when components are no longer in use.
According to a fact sheet created by the Canadian Renewable Energy Association, approximately 85-90 per cent of turbine components can be recycled. Steel, copper, and concrete used in the windfarm can be recycled efficiently, as these types of products already have an established demand.
Separating the fibers, epoxy, and other functional components used in the blades is not always an option, but there are several sustainable, end-of-life repurposing strategies for wind turbine blades made of composite materials.
There is not much demand for recycled fiberglass, given that the raw materials are so inexpensive, nor is there much supply, as most wind turbine blades have not yet reached their end of primary use in Canada. But various recycling methods do exist currently, such as grinding pieces down to various sizes for use as filler material in concrete. In some cases, wind turbine blades have been re-used for a variety of structures such as car ports, pedestrian bridges and play structures.
Organizations like WindEurope are working with researchers from around the world to discover new ways to utilize all windfarm components, helping to increase the volume of materials that can be recycled or upcycled once a turbine or farm has been decommissioned. There is also the SADC of Matane with the collaboration of Université de Sherbrooke that works on a R&D project to, eventually, fully integrate blade fibre residues in concrete and have a financially viable process for doing so.
Regardless of the next steps taken, it’s important to start the next part of the journey in the right way. Make sure to have experts on board who can advise you on what is technically feasible and of all of the regulatory and industry practices that are necessary to continue to operate, for decommissioning, rehabilitating, or rebuilding the windfarm.
Manuel Plamondon-Ratte is the national market lead, wind & renewable structural engineer for WSP in Canada.
Note: This article originally appeared in the Summer 2024 edition of Environment Journal. To see that version, click here.
