Editor’s Note: EarthTechling is proud to repost this article courtesy of Do The Math. Author credit goes to Tom Murphy, an associate professor of physics at University of California, San Diego.
For me, the most delightful turn of events in the ultimate nerd-song “Particle Man” by They Might Be Giants, is that after introducing (in order of complexity) particle-man, triangle-man, universe-man, and person-man—and learning that triangle-man naturally beats particle-man in a match up—we pit person-man against triangle-man to discover that triangle wins—again. In this post, we’ll pit solar against wind and see who wins.
I will take my usual approach and estimate what I can—as opposed to researching the results of detailed studies. It’s part of the process of personal mastery of the big-picture issues, while also providing a sanity-check. In exploring useful reactions to the loomingpeak oil crisis (or pick your favorite rationale for weaning ourselves from fossil fuels), an appropriate strategy is to assess ballpark capacities of the various options. Some will prove to be orders-of-magnitude more prodigious than we need, others will be marginal, and many will show themselves to be woefully inadequate to match the required scale. So the goal is to perform this crude sorting process into abundant, useful, and waste of time.
Earth’s Energy Budget
Since many of the options I will discuss in the coming weeks ultimately derive from the Sun, it is useful to throw up an energy budget.
Of the 1370 W/m² incident on the upper atmosphere from the Sun, 30% is reflected straight away without pausing long enough to say hello. About 20% is absorbed in the atmosphere and clouds, and 50% gets absorbed at ground level. Note that 7% of the energy budget goes into conduction and rising air (separate phenomena; the latter relating to wind). Virtually no heat is able to conduct through the thick atmosphere, so really this figure is all about convection, or moving air.
For comparison, the energy consumption (conversion) rate of the human race is about 13 TW (13 trillion Watts), which works out to an average of about 2,000 W per person on the globe (Americans are 10 kW). We can also divide by the area of the globe to get a power density of 0.025 W per square meter, or 0.09 W/m² if we just count land area.