The optimal is not always the best
Life cycle impacts of near-optimal energy systems
A. De Tomás Pascual (Universitat Autònoma de Barcelona)
Laura Pérez-Sánchez (Universitat Autònoma de Barcelona)
M. Sierra Montoya (Universitat Autònoma de Barcelona, TU Delft - Energy and Industry)
F. Lombardi (TU Delft - Energy and Industry)
Stefan Pfenninger-Lee (TU Delft - Energy and Industry)
Inês Campos (Universidade de Lisboa)
Cristina Madrid (Universitat Autònoma de Barcelona)
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Abstract
Energy system optimization models (ESOMs) can be used to guide long-term energy transitions but often overlook environmental impacts and the diversity of solutions close to the cost-optimal one. Here, we combine an ESOM using Modelling to Generate Alternatives (MGA) with Life Cycle Assessment (LCA) to evaluate 260 near-optimal and technologically diverse carbon-neutral energy system designs for Portugal in 2050 across five environmental indicators: climate change, land use, water use, ecotoxicity, and materials. Using the Calliope energy modelling framework and ENBIOS for environmental assessment, we find that system designs whose cost is within 10 % of the minimum feasible cost provide up to 50 % lower environmental impacts. Our results reveal a trade-off between technological diversity and environmental performance, showing that while diversity enhances resilience, this may come with a significant increase in environmental drawbacks. Solar photovoltaic and battery technologies dominate the environmental impacts, particularly in water consumption and critical material use. This study shows that traditional cost-optimal energy system designs may not be environmentally optimal. Exploring near-optimal alternatives reveals lower-impact solutions and supports more inclusive planning for energy transitions.
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