The story isn’t over for legacy solar: Repowering is the next era of clean energy

While solar is a relatively young industry overall, many first-generation solar arrays are already showing their age. In 2023, writes Will White, solar application specialist at Fluke, over 67GW of solar capacity turned twenty – and their aging components have led to an average 5-10% decline in lifetime performance for utility-scale solar assets.

This decline can lower the financial returns for project owners, investors, and other stakeholders.

Fortunately, in many cases, there’s a solution other than decommissioning the old solar system and building an expensive new one. By upgrading key components to newer, more efficient models, repowering utility-scale solar projects extend their lifespan while enhancing their reliability, efficiency, performance, and ROI.

Done right, repowering can transform aging solar projects by giving them a new lease on life with advanced technologies, ensuring high performance and financial returns for decades to come, and securing their role in the transition to a more sustainable and reliable energy future.

Repowered solar installations continue to deliver consistent, high-quality energy for decades to come.

The first step in repowering a utility-scale solar system involves analysing its current performance, components, and site. In some cases, replacing just a few key components can drastically improve a system’s efficiency, while other systems may benefit from a more thorough overhaul.

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To determine when it’s most cost-effective to repower a solar system, monitor:

• Energy output: Watch for a >10 percent decline from initial performance.
• Module condition: Watch for a >20 percent PV module degradation from its original efficiency.
• Repair frequency and costs: Note when it becomes difficult to source replacement parts for a component since they’re no longer being produced. This may mean it’s time to seek newer, more efficient alternatives.
• Low inverter efficiency or frequent inverter failures.
• More frequent or longer episodes of system downtime.

Common candidates for repowering include inverters, PV modules, trackers, and electrical infrastructure, all of which can lead to substantial efficiency gains and reduced downtime. For instance, new high-powered solar modules typically exceed 20% efficiency (compared to older models at 15-18%).

Adopting these high-efficiency technologies can significantly boost production for utility-scale solar arrays with thousands of modules. Advanced technologies now include tandem solar cells, which utilise multiple layers of solar materials to capture a broader spectrum of sunlight, and bifacial panels, which generate energy from both the front and rear sides – both of which help significantly increase energy production.

Energy storage provides another opportunity for older solar systems to benefit from technological developments. Integrating advanced battery storage is now the industry standard due to the grid stability and flexibility batteries contribute – and there’s no reason to limit their use to new solar installations.

Even systems that already include storage may benefit from expanding their battery capacity or updating to more modern and efficient battery technologies, which offer increased ramp control, peak load management, capacity firming, and enhanced blackout recovery capabilities. These advancements help rejuvenate aging solar installations by ensuring they meet contemporary performance standards and contribute to a more resilient energy grid.

PV modules and battery storage form just two of many opportunities for solar asset managers to improve energy production with updated components – making a thorough assessment of each component’s performance is crucial for developing an effective repowering strategy.

In addition to analysing each component, the entire site should be assessed for changes since the system's original installation. For instance, modules that once received ample sunlight may now be shaded by recently constructed buildings or tree growth. Conversely, the removal of such shade factors might have opened up areas for more modules. A holistic site assessment helps identify these areas for improvement.

After current and historical performance and site analysis, research options that can drive performance for key – but outdated – components. Don’t get bogged down trying to find one-to-one component replacements since many specific models of 20-year-old products are no longer being produced.

Instead, take advantage of this opportunity and have your team identify newer, smarter, more efficient components and technologies that align with your system’s needs. For instance, adding remote monitoring capabilities and predictive maintenance algorithms can identify potential issues before they lead to system failures.

Product research provides several opportunities to optimise the ROI of repowering. For instance, purchasing hardware near the end of the year often allows developers to take advantage of end-of-year discounts. Don’t limit your search to brand-new components; procuring newer, more affordable components in the secondary market may provide an opportunity to increase savings.

Taking advantage of available tax benefits, incentives, and rebates for equipment replacement will also help make repowering more economically beneficial. Finally, when researching components, prevent integration issues by conducting a thorough compatibility analysis between new and existing components.

Once the key components for upgrades have been determined, assess whether a modular repowering approach might work best for your system. This strategy breaks down the project into manageable phases by upgrading a few specific sections or subsystems at a time, rather than the entire system all at once.

In many cases, the flexibility of a modular approach helps maintain a more consistent energy output during the project’s implementation, while allowing developers to optimise their time and budget resources. Implementing upgrades during times of low demand, like midday, also helps limit potential disruptions caused by repowering.

Other best practices that ensure a smooth transition by minimising potential disruption and maximising uptime include:

• A detailed project schedule that includes contingency plans for potential unforeseen issues
• Advanced notice of potential service interruptions to stakeholders, along with real-time updates as needed, to mitigate any unexpected inconveniences for consumers, utility companies, and grid operators
• Temporary backup systems or alternative power sources to provide uninterrupted electricity supply during the repowering process
• Close collaboration with local regulations and authorities to obtain necessary permits and address any potential compliance issues well in advance

Clear communication between all stakeholders is key for the success of a complex project like utility-scale repowering. Define roles and responsibilities for all parties involved in the process, including contractors, suppliers, regulators, and other stakeholders.

Actively communicate repowering plans, activities, milestones, and goals with relevant stakeholders, including utility companies, grid operators, investors, and consumers. It’s especially crucial to provide advanced notice to stakeholders about potential downtime caused by repowering activities.

Once you’ve replaced the necessary equipment and have a revived, more efficient system, you can do one more thing to optimise the project’s ROI. Consider reselling the old equipment you’re replacing to authorised resellers or paying recyclers to take it off your hands. This approach allows you to recover the residual value of the items and gives the old components a new lease on life.

Utility-scale solar and storage systems are central to the clean energy transition, offering significant value well beyond their initial specifications and lifespan. Repowering these systems unlocks this vast potential, ensuring they continue to meet the evolving demands of clean energy production.

Repowering initiatives with new, innovative components will also maximise economic return for project investors, building confidence that the solar industry will help reach ambitious decarbonisation goals.

Repowering utility-scale solar installations not only addresses aging infrastructure but also catalyses the ongoing growth and advancement of the solar energy industry.