Difference between revisions of "Muscle power versus modern consumption"

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'''How much power can humans, and other animals, generate, and how much do we consume?'''
'''How much power can humans, and other animals, generate, and how much do we consume?'''
This [[Hans Free Electric Bicycle|static pedal-powered generator]] ''(above)'' produces 120{{sp}}Watts from moderately energetic pedalling.
Energy guru [https://www.sciencemag.org/news/2018/03/meet-vaclav-smil-man-who-has-quietly-shaped-how-world-thinks-about-energy Vaclav Smil]<ref>
Energy guru [https://www.sciencemag.org/news/2018/03/meet-vaclav-smil-man-who-has-quietly-shaped-how-world-thinks-about-energy Vaclav Smil]<ref>

Revision as of 13:49, 2 August 2020

How much power can humans, and other animals, generate, and how much do we consume?

This static pedal-powered generator (above) produces 120 Watts from moderately energetic pedalling.

Energy guru Vaclav Smil[1] claims that trained individuals can generate 4 or even 5 KW of work for a few seconds, and almost 2 KW equivalent in sustained running.[2]

Generating electricity via a bicycle-style generator is obviously different from running and practical experiment finds that an Olympic cyclist struggles to generate enough power to run a 700 W toaster for a couple of minutes:

One horsepower is defined as 745 Watts, and good horses can sustain 700—800 W of work power, so they could easily run a toaster. Oxen, by comparison, may be capable of only around 300 W for smaller animals.[3]

How much power do we use?

How does this compare with the amounts of power we are accustomed to using as part of a first-world lifestyle? Toasters are amongst the more power-hungry machines we use, along with others that produce heat such as kettles, dishwashers, washing machines, and space heaters of course. Mobile phones, tablets and laptops, and modern energy-efficient LED lights use relatively little, although a dozen halogen downlighters draw almost as much as a toaster.

BBC TV's "Bang Goes The Theory" conducted a practical demonstration, showing how much electricity we use (and abuse!) without even thinking about it. This massive experiment attempted to power a house for an entire day solely through human pedal power, while the unsuspecting family inside went about their normal Sunday routine:

Spoiler: here's what happened when one of the family used their electric shower:

Electric showers are the most power-hungry electrical appliances we use in our homes, but anyone with a gas "combi" boiler uses three times as much energy (from gas) whenever they run a hot tap to fill a bath, or when the central heating is running on a cold day.

Of course we don't run showers, or have the central heating on full blast, all day every day, but in the UK our average consumption of energy for all purposes – heating, hot water, transport, industry, agriculture, etc – is similar to running an electric shower 24*7, 365 days a year.[4]

That's like having scores of cyclists pedalling flat out (or a team of dozens of horses doing the same amount of work) constantly, day and night, year in, year out.

Footnotes and references

  1. See also "Meet Vaclav Smil, the man who has quietly shaped how the world thinks about energy" by Paul Voosen, in AAAS Science magazine, on 21 Mar 2018, [article]
  2. "Energy - A Beginner's Guide" by Vaclav Smil, Oneworld Publications, 2006 - 2017, ISBN 978-1-78607-133-0, page 71
  3. Smil, op cit, page 81
  4. In Sustainable Energy Without The Hot Air David MacKay estimates the typical UK citizen's total energy consumption as 195 KWh/day which is equivalent to 8.125 KW (195 divided by 24). Electric showers like the one in the Bang Goes The Theory programme are rated at 8.5 KW. The average American consumes just over 10 KW.