Wind energy plays an important role in the transition to a carbon-neutral, sustainable energy system and is rapidly expanding. So it is a good time to ask how much wind energy there actually is, whether we get close to the limits anytime soon, and why the efficiency of wind energy must decline when used at larger scales. These are basic science questions: How, and why, does the atmosphere actually generate motion, how much does it generate, and how much of it can at most be used? These questions I address in a review paper just published in which I show that it does not take much physics to answer these.Continue reading “Why does wind energy become less efficient when used at larger scales? Basic physics explains this effect, starting with a very limited ability of the atmosphere to generate wind energy from radiation, as described in my new review just published.”
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From time to time I get e-mails asking me about what our work on wind energy limits implies for the German transition to sustainable energy. With the substantial expansion of wind power in Germany over the last decade, are we getting close to the limits of wind energy that the atmosphere can provide? I looked at the latest ERA-5 weather data product to get answers, and instead of just e-mailing answers, I wrote this blogpost as well to share the insights.Continue reading “How close is German wind energy use to its limit? A quick check using climate data shows that it currently represents a few percent of the maximum, but may get quite close to its limits by 2050.”
Corona has impeded everything in 2020 including researchers’ involvement in scientific conferences. However, innovation and the internet made it possible to contribute to large and much anticipated conferences like the AGU Fall Meeting ‘20. Thus, 2 of our PhD researchers, Annu Panwar and Jonathan Minz, presented their scientific results, keeping the spirit of science communication alive, despite tough times.Continue reading “AGU Fall Meeting 2020: A brief summary of our contributions and takeways”
Trees and plants moderate the Earth’s surface temperature. Generally, the cooling effect of vegetation is mainly attributed to the process of evapotranspiration. In our paper just published in HESS, we used observations to unravel the importance of evaporative cooling for short vegetation and forest in shaping diurnal variations in temperatures and found that, actually, it is not only evaporation that keeps the forests cool.Continue reading “Which factors make forests cooler: Evaporation or their high aerodynamic conductance? Our paper just published in HESS suggests that it is the latter.”
Wind energy has seen a tremendous increase over the last decades, a trend that is likely to continue into the future with the transition towards a sustainable energy system. Yet, each wind turbine removes energy from the atmosphere, so the more wind turbines there are within a region, the more wind speeds should decline, making each turbine less efficient. This effect has clearly been shown by atmospheric simulation models (e.g., in our previous work), but this effect has typically not been accounted for in regional to continental wind energy resource estimates and energy scenarios for the future. The effect sounds complicated, so what should be done?Continue reading “More wind turbines should lead to less wind and less efficient wind turbines, but how to account for this? We showed that our simple spreadsheet KEBA model is about as good as complex WRF simulations to describe this effect.”
My former postdoc, Maik Renner, just got his paper published in the Journal of Hydrometeorology, in which he evaluated the performance of common land surface models at the diurnal time scale using FluxNet observations. The evaluation was based on a simple concept that we developed in my group: that solar radiation is the main driver of the diurnal variation of variables that characterize the land-atmosphere system. This sounds trivial. Of course solar radiation is the dominant driver, so what novel insights can be gained from this view? Continue reading “Solar radiation is the main cause for diurnal variations on land. Looking at this slightly differently than how it is normally done helps to better understand observations and evaluate models of the land surface”
Photosynthesis is the process which powers life on Earth. It takes the energy contained in sunlight, uses carbon dioxide, and generates chemical energy that is stored in form of sugars and similar compounds that fuel the activity of the biosphere, including us humans. And just as any other Earth system process, in doing so it follows the laws of thermodynamics. But does thermodynamics also restrict the efficiency by which photosynthesis can use sunlight?
I have an opening for a Postdoc position available in my group that is rather flexible and provides a lot of freedom because it is unattached to any research project (it is the succession of my co-worker Maik Renner, who advanced to a permanent position elsewhere). I would like the research to broadly focus on advancing the application of thermodynamics and optimality principles to Earth system science, but the concrete topic is up to you. So if you are curious to learn more about thermodynamics and how to apply it, I’d like you to think about a topic and apply! The formal details are provided on our homepage here. Continue reading “Are you looking for a stimulating Postdoc opportunity? Our group has a position open, applying thermodynamics and optimality to Earth system science.”
Global warming, the increase in near-surface temperature due to the enhanced greenhouse effect at global scale, has clearly been reflected in observations over the last 50 years. However, the severities of warming in different regions and different period differs a lot. Scientists have considered many factors which may contribute to shape the temperature trends. For example, our ESD paper explained the stronger temperature trends over land compared to oceans by the different ways by which the diurnal variation in solar radiation is buffered on land and ocean. Here we introduce another simple but significant factor, sunny and rainy days. Continue reading “Does global warming behave the same on rainy and sunny days? No, it doesn’t, and our new JGR paper explains why.”
Winds over the ocean typically have higher wind speeds, resulting in high efficiencies of wind turbines and making this an attractive environment for generating a lot of renewable energy. But how efficient are turbines going to be when offshore wind farms become larger and larger? Continue reading “More offshore wind energy is likely to reduce turbine efficiencies, but still a lot of renewable energy can be generated. This is what a new @AgoraEW study shows to which we contributed.”