Repowering of PV Systems Notes

Repowering of PV Systems

Introduction

• Repowering is gaining attention due to the aging of PV fleets, although most of the US fleet is still young (70% less than seven years old).
• The concept originated in the wind industry, where capacity doubled or tripled frequently, making turbine replacement worthwhile.
• In PV, repowering involves replacing older modules with newer, more efficient ones.
• The decision to repower is complex, with various interpretations and motivations.
• Economic recovery, driven by underperformance or reliability issues, is a primary driver.
• Repowering can range from module replacement to a complete system overhaul, including inverters.

Challenges and Barriers

• Repowering is costly and challenging due to re-engineering requirements.
• Coordination with racking, cabling, and utilities is crucial for successful repowering.
• Inverter Issues: Voltage mismatches exist between older (600V) and newer (1000V, 1500V) inverters.
• Reliability: Issues like backsheet failures (e.g., 2011-2014 backsheets) are major causes.
• Tracker Problems: Two-axis trackers often malfunction and require repowering.
• Module Size Changes: Changes in module size complicate the process.
• Contractual and Legal Aspects: Renegotiating contracts is often necessary and undesirable.
• Land Lease Agreements: Changes in land area usage due to more efficient modules can conflict with landowners.
• Interconnection Permits: Modifying the interconnection permit can be time-consuming and difficult.
• Cost: Repowering is 10-30% more expensive than greenfield projects (new sites).
• Tax Credits (ITC): Uncertainty exists regarding the applicability of tax credits to repowering projects.

Repowering Process

• Trigger: Typically, a reliability issue or underperformance. Owners may also consider it after hearing about new, efficient modules.
• Preliminary Feasibility: Performance team and data analysts conduct site inspections and technical engineering reviews to create a budget ballpark.
• Detailed Engineering: If economically viable (due to reliability, fines for not fulfilling PPA contracts, or warranty benefits), the project proceeds to 3% design and full engineering, followed by execution.

Financial Metrics for Evaluation

• LCOE (Levelized Cost of Energy): Commonly used in the field, but not ideal for repowering.
• Net Present Value (NPV): A more suitable metric that considers inflation and the time value of money.
  • NPV accounts for future value adjustments based on time and risk.
• Payback Time: Another metric considered by stakeholders.

Decommissioning and Costs

• Repowering involves decommissioning aspects, such as removing modules and inverters.
• The further the decommissioning goes (e.g., removing racking and cabling), the more expensive it becomes.
• Decommissioning Cost: Approximately 0.25/watt. Installation costs can be two to three times higher.
• Recycling: Can offset some costs but also represents an additional expense related to social license to operate and environmental responsibility.
• Re-engineering costs: typically a percent overhead.

Case Study: Commercial Building (e.g., Walgreens)

• Scenario: A commercial building owner needs to repair their roof and is considering options for their PV system.
  • Option A: Decommission the system.
  • Option B: Reinstall the existing system.
  • Option C: Repower with newer, more efficient modules (and either sell or recycle the old modules).
• Modeling: Using the System Advisor Model (SAM) to compare the options.
  • Decommissioning results in a negative NPV due to the cost of decommissioning.
  • Reinstalling involves the cost of removing and reinstalling the system.
  • Repowering includes the costs of removing the old system, purchasing and installing the new system, and module disposal.
• Results Highlight: Reinstalling yields a shorter payback period.
• Module Disposal: Recycling or reselling modules doesn't significantly impact the overall financial outcome.

Sensitivity Analysis

• NPV is highly sensitive to utility rates.
  • Repowering may not be economically viable in areas with low utility rates (e.g., Colorado) but can be in areas with high rates (e.g., California).

Residential Systems

• If an older system has more than five years of remaining life, it may be best to keep it.
• Increasing system size often leads to repowering.

Module Reuse and Justice

• Donating or reselling used modules is common, but the economic advantages for the recipient are questionable.
• Meeting an installation cost of less than 1.4/watt with reused modules is challenging.
• Sustainability aspects should be considered.

Conclusion

• As the PV market matures, the question shifts from whether to repower to how to do it responsibly.
• Current economic models do not adequately value recycling.
• Reselling modules seems worthwhile but depends on finding buyers and at the right price.