Shockley-Queisser and the limits to converting sunlight into electricity

Ground-mount solar panels in Jurupa Valley, CA. Image by US Department of Energy (US government work).

Commercially available solar panels now routinely convert 20% of the energy contained in sunlight into electricity, a truly remarkable feat of science and engineering, considering that it is theoretically impossible for silicon-based solar cells to be more than 32% efficient. This upper bound, known as the Shockley-Queisser Limit, was first calculated by the eponymous scientists (who actually gave 30% as their original limit) in the Journal of Applied Physics in 1961 [1] (see also updates by Rühle [2]).

Whether 100 or 100,000, it’s consuming the fossil fuels extracted by these companies that ultimately drives climate change

The Takeaways

  • The famous 71% figure comes from tracing fossil fuels to the companies that extracted the raw fuel, ignoring all the downstream companies, governments, and individuals that actually use these fuels
  • Viewed from the perspective of fossil fuel consumption, global warming emissions are generated by myriad actors, with households the final common driver of the overwhelming majority of climate altering emissions
  • Transitioning away from fossil fuels requires a revolution in how economies and households use energy, and it is largely irrelevant that 100 companies extract the majority of fossil fuels
  • The 100 companies/71% figure is mainly used to discourage meaningful change…

And how many would you save by going meatless one day a week?

The bottom line. (But there’s still more good stuff below!)

Vegetarian, vegan, plant-based, etc. diets seem much more mainstream in the media these days, and meat substitutes are no longer just a bad joke, and yet the typical American eater is the greatest carnivore in all the world, with Americans consuming more meat and other animal products (per capita) than any other country. And meat consumption continues to climb, reaching record highs every year for the last five years, though this year the coronavirus may yet put a small dent in this trend.

So, just how much meat does the average American consume? Fortunately, the USDA provides plenty of data

The epidemiologic picture has improved, but student case rates remain quite high, and ASU’s zip code is now at the epicenter of the Arizona epidemic; future case counts at ASU are highly uncertain

Final Update, Sep. 10, 2020: ASU has confirmed elsewhere that it is indeed reporting active cases, but will now includes cumulative cases from August 1, 2020 to (presumably) the date of the most recent update. Historical data has not been provided. From Sep. 9 on, new cases and percent positives will presumably be possible to calculate, but no reliable analysis can be performed on the historical data as previous cumulative case counts remain unknown.

Update Sep. 7, 2020: ASU’s data disclosure today, reporting “807 total known positives” in the student body, down from 957 four days priors, shows that the…

While the numbers are presented as benign, a closer look shows an unfolding disaster

Academic Caveat: The following analysis and findings have not been peer-reviewed. All opinions are solely those of the author.

An update on more recent numbers can be found here, but the original text of this article will remain unaltered.

First: The Takeaways

  • Under public pressure, Arizona State University disclosed limited COVID-19 case data on August 25 and August 28, 2020. However, the presentation was highly misleading, and a re-analysis of what is available suggests a rapidly spreading epidemic that is hitting students living on campus especially hard.
  • ASU highlighted an estimate of the effective reproduction number, Rt, as 0.87 for Arizona as a…

Discards, biofuels, meat, and opportunities for change

Ethanol Plant in Crawford, Iowa. Photo by Kurt Haubrich, https://www.flickr.com/photos/kphaubrich/26321507383/. CC BY-ND 2.0 license (https://creativecommons.org/licenses/by-nd/2.0/legalcode)

Overview and effective waste in the food system

The ongoing COVID-19 pandemic has reshaped the patterns of American life in unprecedented ways and with stunning rapidity, resulting in many unintended, but not unwelcome, environmental benefits, as skies clear and animals venture into newly empty spaces [1]. …

Steffen Eikenberry

Academic with a background in medicine, mathematics, and engineering (MD,PhD). Interested in agriculture and how consumption drives global environmental change.

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