Efficient food production

[james_davis_nicoll]

I was noodling around on soc.history.what-if and made a calculation I'd never bothered with before: if a human needs enough food to produce N Watts, how many square meters are required to intercept that much sunlight? OF course I was too lazy to actually look up insolation for various latitudes but the BOTEC I committed seemed to show that it should be a few square meters.

Even Fairbanks, Alaska, gets from 90 to 350 watts/m^2. Say your mark 1 human needs at least 100 watts worth of food to keep functioning [1]: They'd need about one square meter dedicated to collecting solar powers, asssuming no losses. The entire population of North America should require a few hundred to a thousand square kilometers of converters to power themselves. Even a factor of ten losses should mean that we'd need about 300 square kilometers to feed all of Canada, assuming the lowest insolation in Alaska is what we have to work with, and about 3000 square kilometers to feed all of the USA. That's a square less than 20 kilometers on an edge for Canada and a bit over 50 kilometers on an edge for the USA. Feeding the entire planet should require about 60,000 square kilometers or a square about 250 km on an edge (or less, if we pick someplace sunnier than Fairbanks to grow food).

Clearly modern methods of coverting solar (and fossil) energy into human energy are criminally inefficient.


1: Googling says "at least 2500 kilocalories" per day so call it 4000 to be safe. That works out to about 50 watts, which I will double just because.

Comments

[liveavatar.livejournal.com]

At first I misread this as "how many square meters [of human] are required to intercept that much sunlight," and yes, I know that's not what you really meant.

But until I figured that out I was having a grand time imagining a lot of people who went around fat and naked as a statement of low energy consumption (or as a statement that they could only afford their Guaranteed Solar Income).

Yrs in the name of stfnal life through incorrect assumptions,
Liveavatar

Not Fat

[james-nicoll.livejournal.com]

Fat = volume. You want to maximize area to volume, so you'd end up extended in two dimensions and reduced in another. Like a leaf, say, or those ribbon-like organisms in the ediacaran.

Re: Not Fat

[liveavatar.livejournal.com]

Hmn, I guess it depends on how efficient the energy absorption mechanism is, and on the individual's metabolism.

Heck, if we're engineering people enough that they can absorb their calories via sunlight in the first place, then we can engineer them with photosynthetic ribbon-hair or dreadlocks. Or photosynthetic tails. (See H. Allen Smith's The Age of the Tail.) Or webbing between the fingers that can take advantage of hydropower (read: swimming)

In the case of energy-dreads, baldness would become more than an aesthetic problem. But if we've gone that far, I doubt baldness would require more than an afternoon in a bioplastic surgeons' outpatient chair.

[sunshaker.livejournal.com]

Are you suggesting that we Gene-Mod humans so that they are green and can eat dirt to make food? How much energy would be produced that way? Would it be worth it?