As early U.S. renewable energy projects age and new greenfield projects face rising capital costs and growing permitting and interconnection challenges, a renewed focus on renewable repowering projects has emerged.
Repowering projects replace dated renewable energy equipment with modern, more powerful equipment, which increases the output and extends the life of established renewable energy sites. This can take the form of full repowering, which completely decommissions original equipment and replaces it with modern equipment, or partial repowering, which replaces only components of the preexisting equipment.
There is typically little opposition to renewable repowering projects from a land use perspective as they utilize previously developed sites. Additionally, interconnection challenges faced by greenfield development are often avoided in renewable repowering projects because the grid connection already exists.
Wind Generation Repowering
Wind turbines typically have a lifespan of 20-25 years, and the earliest U.S. wind projects are approaching their end of life. Today’s wind turbine technology far outpaces the capacity and efficiency of those that were used to build the earliest projects in the U.S. On average, wind turbines installed in the U.S. in 2023 had 375% more power capacity (MWs) than wind turbines installed 25 years earlier in 1998.
Full repowering projects that replace outdated turbines with modern turbines can significantly improve the productivity of existing sites. Typically, fewer wind turbines can be installed in a repowering project than were installed in the preexisting project because the modern turbines are larger and require more space, but the improvements in output often outweigh the reduction in number of turbines. In other words, developers can get more power out of fewer turbines through full repowering.
Full or partial repowering is also being considered for wind projects that are not necessarily at their end of life but are nevertheless significantly outperformed by modern technology. Due to these technological improvements coupled with depreciation of existing equipment over time, it is estimated that repowering can add 10-20% more capacity to projects built only 12 years ago.
Wind generation repowering projects can also have cost savings over traditional greenfield development projects because certain infrastructure from the original project, like roads and interconnection facilities, can be reused. Partial repowering projects can see even greater cost savings than full repowering projects as they do not involve the full decommission of existing turbines.
Repowering projects replace dated renewable energy equipment with modern, more powerful equipment, which increases the output and extends the life of established renewable energy sites.
Solar PV Generation Repowering
The typical lifespan of a solar photovoltaic (PV) module is 30-35 years, with most manufacturers providing performance warranties of around 25 years. Most of the oldest solar projects are still effective since large-scale PV deployment in the U.S. only gained significant momentum around 2010. Full solar PV repowering projects have not taken off to the same degree as wind repowering projects have.
In addition, solar PV technology is improving but has not seen the same drastic increases in power output that wind turbines have in the years since major renewable development started. Solar PV repowering does not offer the same levels of increased project capacity as wind repowering does.
However, while solar modules are still effective on aging projects, other equipment failures are occurring. Primarily, early inverters sometimes fail after around 10-15 years. Inverters are essential components of a solar PV project that convert direct current electricity generated by the solar panel to alternating current electricity that is usable by the U.S. grid. Solar modules cannot be fully utilized without fully functioning inverters, so partial repowering projects that replace failed inverters are becoming common. It’s expected that 10% of the total current installed capacity of U.S. solar projects will likely need inverter replacements over the next 5 years.
Replacing old inverters with modern inverters offers opportunities to increase energy output in other ways, too. Battery Energy Storage System (BESS) technology has advanced rapidly in the years since solar development took off. Installing BESS alongside solar PV is common in modern projects because BESS can be used to better match electricity supply from a solar PV site with peak demand. Installing BESS alongside inverter replacement is appealing to developers, and inverters and BESS can often be installed concurrently.
Renewable Repowering Processes
The design codes, standards, and requirements of the Authorities Having Jurisdiction (AHJ) for the renewable repowering project location have often changed since the development and construction of the preexisting project. Developers of renewable repowering projects must analyze and meet updated requirements such as noise, viewshed, or setback requirements.
Developers will initiate permitting and approval processes with the AHJs for the repowering project design. Full renewable repowering projects can undergo similar approval processes to greenfield development, but for partial repowering, permitting timeframes and costs are often lower than greenfield development as this process does not involve full redesign. For both full and partial renewable repowering processes though, interconnection approvals tend to be much simpler and more affordable than greenfield development because the grid connection already exists.
Developers will conduct conditional assessments of existing infrastructure including the generators, foundations, interconnection equipment, roads, and civil infrastructure to determine what equipment can be reused and what will be replaced and/or upgraded. The existing site conditions will be evaluated and integrated into engineering designs for the renewable repowering project. Engineering design can include developing decommissioning plans for the existing site, running energy production models of the site with modern renewable technology, designing a new site layout, designing foundation reinforcements, leveraging existing interconnection infrastructure, integrating new electric redundant measures, etc.
Once AHJ approval is granted, the equipment to be replaced will be decommissioned and properly recycled or disposed of and the repowering equipment will be installed and commissioned.
Overall, renewable repowering projects will likely play an important role as the U.S. renewable industry matures, enabling developers to cost effectively increase generation capacity, extend asset life, and reduce permitting and interconnection hurdles.
Contact Rachel Stukenborg, 804.340.7053, for more information about GAI’s renewable power generation support, part of a range of GAI’s comprehensive engineering, environmental, and cultural resources services for power and energy projects
Rachel Stukenborg, NABCEP Photovoltaic Associate™ advances renewable energy initiatives by supporting preliminary site design and energy production modeling for solar energy and energy storage projects. She performs engineering calculations, prepares project drawings, generates contract documents and specifications, and completes engineering reports, as well as providing supplying technical support for contractors during project construction.
