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: China's PV potential with pollution-free 1960s surface radiation

Historic (1960 – 2015) capacity factors (red) and SO2 (blue) and black carbon (black) emissions in China as a percentage of peak emissions in 1994 and 2005 respectively. Thin lines are annual, thick lines 5-year moving mean values. Adapted from Sweerts, Pfenninger, Yang, Folini, van der Zwaan and Wild (2019).

Using solar radiation data from 119 stations across China we show that photovoltaic electricity potential decreased on average by 11–15% between 1960 and 2015. Given the observed relation between surface radiation and emissions of sulphur dioxide and black carbon, reducing air pollution should let surface radiation increase. Reverting back to 1960s radiation levels could yield a 12–13% increase in China's solar electricity generation. → Sweerts, Pfenninger, Yang, Folini, van der Zwaan and Wild (2019), Nature Energy.

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

  • Home-made or imported: On the possibility for renewable electricity autarky on all scales in Europe. Tim Tröndle, Stefan Pfenninger, Johan Lilliestam. (2019). Energy Strategy Reviews. doi: 10.1016/j.esr.2019.100388
  • The dragon awakens: Will China save or conquer concentrating solar power?. Johan Lilliestam, Lana Ollier, Stefan Pfenninger. (2019). AIP Conference Proceedings. doi: 10.1063/1.5117648
  • Estimation of losses in solar energy production from air pollution in China since 1960 using surface radiation data. Bart Sweerts, Stefan Pfenninger, Su Yang, Doris Folini, Bob van der Zwaan, Martin Wild. (2019). Nature Energy. doi: 10.1038/s41560-019-0412-4

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