The Oil Drum

Hemisphere-centricity aside, he's right. The "total solar flux" argument is the last refuge of the cornered cornucopian. It's a will o' the wisp that blows away at the first breath of common sense.

My statement can be easily cut by a factor of one thousand, because once we start to change Earth's albedo by more than 0.1% or so, the absorbed heat causes global warming directly. Let me show you why that is so:

Currently (2001) it is estimated that we use 4.26 × 10^20J of energy annually. That is roughly 13,500GW of continuous power, most of which is waste heat, of course. Solar radiation on the surface is approx. 1kW/m^2. The exposed side of the planet has an effective area of pi*r^2 = 1.34e14m^2. Thus the power of solar radiation hitting Earth's (completely cloudless) surface is roughly 130,000,000GW and above the atmosphere it is 50% more. 1W/m^2 is the magnitude of the radiative forcing from trapped IR radiation in the atmosphere (energy that has not been used by us at all) that causes global warming. This equals roughly 132,000GW of heating power. These are all orders of magnitude, in reality there is cloud cover etc. which is seriously complicating things.

Thanks to the energy conservation law it does not matter where the heat that causes global warming comes from. It can be trapped IR or it can be heat created by fusion power, to the planet it is all the same. It follows that ANY power generation method will have similar effects on the surface because the only way to get rid of it is by radiation into space! The limit of how much energy we can use in total before we start heating the planet directly (rather than by changing the atmospheric IR scattering) is therefor only one order of magnitude beyond the amount of energy we use already. And since future solar cells will have roughly 40% efficiency (going beyond three junctions seems a waste) and since the thermal efficiency of other power generation methods is also 40%, useful power vs. process it is a wash. I made the assumption here that the radiators are at sea level... you could always put the power plants on stilts above the atmosphere and then avoid the 60% penalty or install the solar panels in space and use them to shade the planet etc., but I am trying to discuss 21st century technology here, not 23rd century stuff.

So if we really wanted to use energy beyond the 1W/m^2 limit (which is on the order of maybe 100,000GW), we would need to start installing planetary air conditioning. It can be done, but we are talking terra-forming or at least terra-controlling technologies here... something I won't speculate about right now.

You see... the point is that solar energy can easily cover what we need right now and then some. But beyond what can be done with solar energy, there is very little room for anything else without really heroic efforts.

"Now exactly what were you trying to say again before the bus of reality ran over your pipedream?"

I was trying to say that I have done my homework. Please, please inform yourself.

Or. . . how many solar panels would it take to run a factory that makes solar panels?

"Only" a few hundred thousand square km with current technology...