The two types of wind farm repowering are full repowering and partial repowering. Full wind farm repowering is when the aging wind turbines are decommissioned and removed and replaced with newer, larger, and more efficient wind turbines at the same site. Partial repowering involves keeping the existing wind turbine and replacing key components to improve power capacity, reliability, and extend the lifespan. Wind turbine lifespans range from 20 to 25 years, and as they age, capacity is reduced as mechanical parts deteriorate. Innovations in wind turbine technology drastically increase the output of power, which makes repowering an aging fleet enticing.  

Benefits of Wind Farm Repowering

When comparing to new projects, repowering requires significantly less investment. Repowering projects utilize the existing infrastructure, including roads and substations, resulting in lower installation costs. Repowered wind turbines receive warranty renewals from OEMs, which extends the coverage period for the turbine. The wind farm owner could receive significant tax incentives based on the timing of the project. Most importantly, newer wind turbine technology increases the amount of renewable energy produced as well as providing better power quality and reliability to the electrical grid.

Considerations for Repowering

While there are many benefits to repowering, a number of considerations need to be taken into account and addressed before the project can move forward. Here are a few to consider.

1. Changes in National or Local Laws and Jurisdictions

Projects being considered for repowering were initially developed 20 years ago, and the project will be subject to any changes in laws and regulations affecting local and regional jurisdictions. A thorough review of current requirements and restrictions in local jurisdictions is needed to ensure the repowering plans are in compliance with current laws and understand any potential cost impacts or timeline delays that could result from legal changes.

2. Environmental and Permitting Factors

The location and ownership of the wind project property will dictate what agencies will have the right to exercise jurisdiction over the project. This can include a number of federal, state, county, water authorities, and the Bureau of Indian Affairs. On a federal level, both the Federal Aviation Administration (FAA) and the Department of Defense (DOD) maintain jurisdictional requirements for wind projects. The size of the turbines may also impact the permitting process. Larger turbines take up more space and could require additional compliance steps and approvals.

3. Contract Structure of Real Property Agreements

A complete review of the original project site control documents will identify if there are any restricting or limiting factors or real property tax and assessment implications that could impact the project.

4. Power Purchase Agreements (PPAs)

PPA terms for wind projects typically have a duration between 15 to 20 years. When considering repowering, evaluation of the economic impact from decommissioning the wind turbines early versus running the turbines through the entire PPA term is needed. If the wind farm repowering project requires a new project design with the decommissioning of the existing turbines, it is a good time to negotiate and develop new PPAs.  

5. Hybrid Technologies

Projects for wind can now incorporate solar and/or battery storage to increase energy generation on the site and improve the dependability and efficiency. Because of the variability of wind power, battery storage will enable wind farms to store energy when winds are strong and provide that stored energy when winds are low, delivering stable energy to the grid. As battery storage becomes more widespread, it will be a factor to consider during repowering projects.

6. Site and Structure Review

A comprehensive review of the site and turbines needs to be completed for both full and partial repowering project. A rigorous evaluation of the structural integrity and capacity of the existing foundations will establish if they are suitable for repowering. For the overall site, determine if any updates or expansions are needed for the current infrastructure to accommodate new, larger turbines. Consideration should also be given to adding or upgrading systems to protect the new or repowered wind turbines ranging from monitoring software to fire suppression systems.

For a partial repower, other factors will need to be considered. The towers must be in good condition, properly maintained, and free of any damage or past failures. An evaluation needs to be completed on all components that will remain and assess any potential issues with combining new and existing components. Complete a review of the possible effects of wear and fatigue damage on components that are not planned to be replaced. Keeping or reusing components can provide significant cost savings, but issues of compatibility and other potential risk factors need to be identified including fire risks

Conclusion

Full and partial wind farm repowering provides project owners the ability to generate more energy, extend the life of the projects, and provide more reliable power to the grid. It is essential to understand and weigh all the factors that can impact a repowering project to find the most benefits. Repowering old wind turbines with new components or replacing older turbines with fewer new turbines ultimately both increase the amount of energy that can be generated from a given wind farm.

 

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