Rapidly transitioning to clean and sustainable energy

I am an interdisciplinary researcher in renewable energy and environmental science, heading the Sustainable Energy Systems Unit in the Climate Policy Group at ETH Zürich's Department of Environmental Systems Science. Our research is on the global transition to a 100% clean and renewable energy system, and the technical, economic and policy barriers on the way to that goal.

Research spotlight: Trade-offs between geographic scale, cost, and infrastructure requirements for fully renewable electricity in Europe

Source: Adapted from Tröndle, Marelli, Lilliestam and Pfenninger (2020).

Renewable electricity supply in Europe would be cheapest with a continent-wide optimised system where wind and solar power are deployed at the best locations. However, it is also possible to build nationally or subnationally balanced supply systems with cost penalties of 20% or less. Such a low-cost but regionally balanced electricity supply requires continental-scale balancing of renewable fluctuations and an expansion of cross-border transmission capacities, but not necessarily an overall large transmission grid. → Tröndle, Marelli, Lilliestam and Pfenninger (2020), Joule.

Open code and data

In the course of my work I created and lead development of the open-source energy system modelling tool Calliope. I am also the creator and lead developer of the Renewables.ninja platform to simulate wind and solar power plants worldwide. I am a member of the Open Energy Modelling Initiative, which promotes openness and transparency in energy system modelling, and of the Open Power System Data project, which provides a free and open data platform for power system modelling.


You can contact me by email. I am always interested to speak to enthusiastic students looking for thesis projects or research experience. Get in touch by email with a CV and some detail on your research interests.

Recent publications

  • Policy Decision Support for Renewables Deployment through Spatially Explicit Practically Optimal Alternatives. Francesco Lombardi, Bryn Pickering, Emanuela Colombo, Stefan Pfenninger. (2020). Joule. doi: 10.1016/j.joule.2020.08.002
  • Trade-Offs between Geographic Scale, Cost, and Infrastructure Requirements for Fully Renewable Electricity in Europe. Tim Tröndle, Johan Lilliestam, Stefano Marelli, Stefan Pfenninger. (2020). Joule. doi: 10.1016/j.joule.2020.07.018
  • On the Potential of “Photovoltaics + Electric Vehicles” for Deep Decarbonization of Kyoto’s Power Systems: Techno-Economic-Social Considerations. Takuro Kobashi, Takahiro Yoshida, Yoshiki Yamagata, Katsuhiko Naito, Stefan Pfenninger, Kelvin Say, Yasuhiro Takeda, Amanda Ahl, Masaru Yarime, Keishiro Hara. (2020). Applied Energy. doi: 10.1016/j.apenergy.2020.115419

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