[lloeki]

> Same for solar if pea counting, but solar is really endless until the end of the solar system

Imagine you wrap the Earth inside a sphere of perfectly efficient solar panels, that would be energetically troublesome! Every bit of solar panel we lay removes a bit of that overall energy flux; the question is then how much can we afford without detrimental impact.

Essentially we dampen tides with these devices. Windmills are slowing the wind. How much can we afford before it has an actual detrimental effect?

Also, pedantically, "renewable" is a fun word.

The question of "renewable" is whether the energy/matter somehow gets back in some way... Of course there's entropy and such.

Say you cut wood (CHO) and burn it. If you grow enough wood it'd recapture H2O+CO2 and you have a nice endless loop (plus entropy). That would presumably be renewable.

In that sense (again, pedantically):

- nuclear (and so the sun) is not renewable: reversing U/Pu/whatever fission is a teeny bit out of our league so someday the supply will dry out. Fusion as we do it (and the sun too, being main sequence) is H->He and we don't exactly know how we could reverse that so someday the supply will dry out.

- fossil fuel is renewable... on a geological timescale, which is not really practical; we can't exactly grow big enough forests and bury them for millions of years to get fuel back. So someday the supply of humans surviving will dry out.

- tides/wind is not renewable: we get mechanical energy but don't return it to the original place (or maybe extremely indirectly in the form of heat)

So it's all named backwards!

Or really there's no renewable... Essentially it all pans out because the Earth is not a closed system, there's loss in every transformation but it's balanced by the energy influx from our nearby star.

So I guess the "renewable" thing is not really, it's more like "capturing energy from an astoundingly immense and complex system in a way that doesn't throw it in a runaway catastrophe one way or another before the sun exits its main sequence".

[IanCal]

I think you're assuming renewable means infinite.

> - nuclear

Nuclear isn't renewable, but there's a huge amount of it and it doens't have the same problems.

> (and so the sun) is not renewable:

The energy we get from it is. It's not a fixed resource that we're depleting. When we burn all the coal, it's gone. Tomorrow there will be more sunlight. We're not cutting chunks off of the sun to get energy for solar.

> - fossil fuel is renewable... on a geological timescale,

Only some of them, and only if we change the definition of renewable. Coal is there because there weren't fungi that could break down lignin at the time.

> Imagine you wrap the Earth inside a sphere of perfectly efficient solar panels, that would be energetically troublesome! Every bit of solar panel we lay removes a bit of that overall energy flux; the question is then how much can we afford without detrimental impact.

We could probably benefit significantly with reducing the energy flux right now.

[lloeki]

> I think you're assuming renewable means infinite.

No, for the purpose of this dumb exercise of mine, I mean the resource we use for energy production is replenishable.

> It's not a fixed resource that we're depleting.

What I mean is that the Sun is going to exhaust its H supply. We just happen to harvest part of its output, but it's depleting itself whether we harvest it or not, so we might as well do it :shrug:.

So at our scale it looks like infinite but in the strictest sense it's a consumable that does not replenish.

Fundamentally that makes it not different from nuclear fuel (whether heavy fissile ones or hydrogen if we manage fusion someday) which as you mention are in ample supply, yet we consider them to not be renewable while the sun would be? The only difference is a) the Sun is (much) bigger thus will last (much) longer and b) we delegate fuel logistics and fusion reaction to the sun.

But then again, trees are not really renewable, they got to get energy from somewhere to grow... IOW they're essentially CHO-based solar batteries.

As I said, I was not trying to make any point, just being extremely pedantic about semantics for fun ;)

> the definition of renewable

> A renewable resource (also known as a flow resource) is a natural resource which will replenish to replace the portion depleted by usage and consumption, either through natural reproduction or other recurring processes in a finite amount of time in a human time scale. When the recovery rate of resources is unlikely to ever exceed a human time scale, these are called perpetual resources

https://en.wikipedia.org/wiki/Renewable_resource

Essentially the definition is focused on resource when it's really about time (esp. our extremely small time scale vs stellar scale). The resource in reality doesn't replenish, rather it's so huge that we can consider our usage of it well below rounding error. IOW from our very small "rounding error" human point of view it might as well be considered infinite.

[IanCal]

We could push it further and say there's no renewable source possible - at least until the multivac finally gets the answer.

> The resource in reality doesn't replenish

Sunlight does. Wind does. A water wheel in a river is renewable power. Solar panels producing power today don't make tomorrow darker.