THOUGHT LEADERSHIP

Breathing new life into Australia’s aging wind farms

The wind industry, well-established in Europe for decades, took baby steps onto Australian soil in the late 1980s and 1990s. By the early 2000s, Australia’s new wind industry was ready to take off. Given that wind farms usually have a design life of anywhere between 15 and 30 years, our earliest wind farms are now reaching retirement age. The industry therefore faces a new set of challenges. Can these older wind farms continue to serve their important role in Australia’s clean energy transition or are they at their end of life?

So far, few wind farms in Australia have been decommissioned, dismantled and removed from the land. With many of our older wind farms sited to capture the best wind resources, there’s every reason to try to continue using these sites to harness wind energy.

One option is to squeeze more years out of the wind farm through effective maintenance and supportive analysis to ensure it is safe to do so while accepting that there may be increasingly frequent outages and increased maintenance costs to keep the wind turbines in service. However, although operation beyond the nominal life of a wind turbine is theoretically feasible, old wind turbines can’t keep spinning forever and will need to be stopped at some stage.

Other options for aging wind farms are refurbishment of some parts of the turbines, or full ‘repowering’ with completely new machines. This could also include a full redesign to accommodate larger turbines or to incorporate solar or battery energy storage systems.

An example of rejuvenation

Small grids may be some of the first to need to consider what to do about old wind farms. As an example, Hydro Tasmania’s Huxley Hill Wind Farm on King Island has three 250 kW wind turbines that were installed in 1998, and two 850 kW wind turbines that were installed in 2003.

For Huxley Hill Wind Farm, the King Island electricity load has not changed much over time, and offsetting diesel using renewable energy continues to make perfect sense.

For this site, the owner opted for a like-for-like replacement of nacelles (generator, gearbox, yaw system) of the Nordex 3 x N29 250 kW and potentially for the 2 x Vestas V52 850 kW wind turbines. This decision was partly about the good economics and sustainability of reusing existing infrastructure, and also because wind turbines of this size continue to suit the project so well.

When the wind farm was constructed 20+ years ago, the installed wind turbines were considered modern, large wind turbines. These days, the same suppliers do not offer anything less than 2 MW in capacity, with rotor diameters greater than 110 m. The lack of availability of what are now considered smaller wind turbines (say 1 MW) poses challenges for some small projects. At the scale of less than 1 MW, there are now few proven wind turbine options. At an even smaller scale (<100 kW), solar PV now dominates.

When any existing infrastructure is to be retained to support life extension of old wind turbines, such as at Huxley Hill, it’s crucial to confirm that it is still suitable and safe. This can include various techniques and activities, including:

• physical inspection by technicians and engineers
• excavation of the foundation backfill cover to reveal the tower-foundation joint and inspect corrosion and remediation
• surveying the tower and blade condition using drones
• surveying the tower verticality
• surveying the thickness of tower sections
• ultrasonic testing of bolts
• eddy current testing of welds to detect any flaws
• reviewing data from the turbines to refresh understanding of the actual wind regime, reassess fatigue loads and estimate remaining life.

Another important consideration when rejuvenating older wind farms is to consider the potential for adding solar or battery energy storage. With solar now more viable than when Huxley Hill Wind Farm was conceived, a 1.5 MW solar farm has been added to augment the wind generation.

Starting over with full repowering

Because the Australian wind industry is still relatively young, there is not yet an established practice or precedents for full repowering. However, in Europe, hundreds of wind farms have been repowered, often massively increasing output by using fewer but much larger modern turbines.

Repowering at around 25 years seems the most likely timeframe for most Australian wind farms – but few have yet reached this age. Ultimately, market factors will determine when repowering provides the best financial return.

Even though we’re still just on the brink of Australia’s repowering journey, it’s never too early to start considering the complexities and implications and assessing all options.

Repowering won’t be simple or quick. The development process for repowering NEM-connected wind farms is likely to be just as challenging as developing a new wind farm on a greenfield site.

The concept of ‘repowering’ involves a range of options for replacing old wind turbines and associated footings and electrical balance of plant with new, but it’s unlikely that much of the existing infrastructure and balance of plant will be able to retained if larger, modern turbines are selected. The layout of the wind farm is also likely to need revision to accommodate longer blades.

Planning approvals need to start just as early, as should the process of renegotiating with hosts, neighbours and communities. People may be concerned about the impacts of much taller turbines and the logistical issues of getting them to the site, as well as arrangements for the dismantling, removal and disposal of the superseded technology and infrastructure.

Repowering with bigger and more powerful turbines is also likely to involve re-permitting and negotiating a new grid connection agreement – neither of which are certain, given the cumulative impacts that may have emerged over time and any changes to rules and regulations since the wind farm was first developed.

By planning early for repowering, developers can get ahead on these issues as well as on condition assessment of the assets, decommissioning plans for old turbines, new studies that might be needed (such as bird monitoring), and new wind measurements for taller, modern wind turbines, perhaps using modern wind measurement technology such as lidar.

While some repowered wind farms will very likely incorporate new battery energy storage systems (BESS), they are less likely to deploy large-scale solar as a default, given that many of the best original wind sites in Australia are coastal or hilly, particular those in the south of the country. Nevertheless, the potential for co-located renewable generation, storage and loads is worth exploring. 

Don’t wait for trouble – start planning now

We suggest that wind farm owners take action now to deepen their understanding of the condition and present value of their assets, and explore the full range of short-term and long-term options available through a feasibility and options study. After all, in such a dynamic market and technology landscape, and with the potential for aging assets to deteriorate or fail, decisions about end of life may need to be made earlier than expected.

About the author

Andrew Wright is Entura’s Senior Principal, Renewables and Energy Storage. He has more than 20 years of experience in the renewable energy sector spanning resource assessment, site identification, equipment selection (wind and solar), development of technical documentation and contractual agreements, operational assessments and owner’s/lender’s engineering services. Andrew has worked closely with Entura’s key clients and wind farm operators on operational projects, including analysing wind turbine performance data to identify reasons for wind farm underperformance and for estimates of long-term energy output. He has an in-depth understanding of the energy industry in Australia, while his international consulting experience includes New Zealand, China, India, Bhutan, Sri Lanka, the Philippines and Micronesia.

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26 February, 2024