Strategic solar module stockpiling in the EU: A scenario-based analysis of costs and benefits beyond 2030

What are the optimal levels of strategic solar module stockpiles in the European Union (EU) for achieving climate neutrality by 2050, and how might such stockpiles influence efforts to bolster domestic solar manufacturing and recycling industries? This paper addresses these questions, delving into the underexplored area of strategic reserves in renewable energy systems and offering actionable insights for policymakers to ensure stable solar PV deployment. Using an extended open-source energy system optimization model, 36 scenarios varying in energy costs, import dynamics, and economic factors were analyzed. The results indicate that stockpiling is cost-effective in only 8 scenarios, primarily under unfavorable import conditions. In scenarios with stockpiles, domestic manufacturing levels are, on average, lower and required later compared to scenarios without stockpiles. Stockpiles reduce import dependency by introducing temporal flexibility between module injection and withdrawal, effectively diversifying supply strategies. Additionally, they stabilize optimal wind capacities, underscoring their broader systemic role. The associated costs are modest, increasing by just 0.2 % in the reference scenario aligned with the latest Ten-Year Network Development Plan. Recycling and remanufacturing are not utilized in any scenario due to their higher costs compared to imports and EU manufacturing. From these findings, three policy recommendations emerge: (i) establish a strategic stockpile equivalent to three times the annual solar PV additions during the early 2030s, (ii) foster innovation in solar module recycling and remanufacturing in the meantime to build a resilient domestic industry, and (iii) monitor technological advancements to ensure the relevance and utility of stockpiled modules.