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Geothermal vs Solar Power

lgw (121541) writes | more than 2 years ago

User Journal 1

Here are the basic numbers on aailable geothermal vs solar power (since this has come up in discussion more than once).

The surface area of the Earth is about 5.1 x 10^14 m^2. The cross sectional area is about 1.3 x 10^14 m^2 (one quarter of the surface area, of course).

Here are the basic numbers on aailable geothermal vs solar power (since this has come up in discussion more than once).

The surface area of the Earth is about 5.1 x 10^14 m^2. The cross sectional area is about 1.3 x 10^14 m^2 (one quarter of the surface area, of course).

Per this paper found as a cite on wikipedia, the total heat flow out from the Earth's interior is 4.42 x 10^13 W, or 0.0867 W/m^2. Of course, the available power is much less because it's only the subsurface-surface temperature difference that's available.

Total solar irradience is 1361 W/m^2 by NASA's latest estimate (so about 1.7 x 10^17 W across the entire cross section), or about 1000 W/m^2 on the surface at noon on a cloudless day. Averaged over the day-night cycle (surface area vs cross-section, so 250 W/m^2), and taking clouds into account that's about 180 W/m^2 (I can't find a solid source on that yet, but it looks close).

So, total solar power flow is about 4000 times as large as total geothermal flow. I'm not quite sure how to estimate the (ideal) available power as a percentage of the total geothermal power flow, but if we use a WAG of 50%, then the available power from solar is also about 4000 times per square meter more than geothermal - significantly more if we average solar power only across populated latitudes.

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1 comment

More harm than good? (1)

sznupi (719324) | more than 2 years ago | (#37356230)

While such numbers are technically correct (well, probably, I don't feel a need to recheck them), they possibly oversimplify the issue to the point of being harmful.

There are worse and better places for both geothermal and solar. I can think of a few which are fabulous for one, but quite poor for the other. There's no reason for them to not coexist (especially since they have different characteristics, geothermal being very suitable for base load for example), choosing one which is more suitable for the place ...or even both (or more)

PS. Plus, that total solar irradience drives the atmosphere and essentially the whole planetary biosphere, on which we also greatly depend - though, admittedly, we already use more than is available... [wikipedia.org] (temporarily thanks to the fossil fuels, which simply store past solar energy collected by the biosphere - last I've heard, we now use ~3 million years worth of production in 1 year - and when spoiling future hectares)
...and overall, we don't seem to care too much about borgifying the planet (say, covering most of it in some infrastructure, eventually) - after all, we already cause - almost casually, almost without blinking an eye (except for what comes from some rare "tree huggers") - what will be possibly the most rapid extinction in geological record (~half of all species gone by 2100, massive volcanism or asteroids apparently struggled to achieve such rates)
Of course, the last laugh might still be on us... [wikipedia.org]
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