[ExI] Comment for Scientific American

[Keith Henson]

On Mon, Oct 5, 2015 at 5:00 AM,  John Clark <johnkclark at gmail.com> wrote:

> I don't see solar power satellites providing energy cheaper than fossil
> fuel anytime in the immediate future, to me even terrestrial solar and wind
> seem too dilute and intermittent to compete with coal economically.

The dilute factor isn't as much of a problem in space where you don't
have to support the concentrating surface against gravity and wind.

But if power satellites can't proved energy cheaper than any other
source (except hydro which limited) then they just won't happen.

> The only fuels I can think of that
> have a chance to beat coal in both the short term and the long are Uranium
> and Thorium. In the case of Thorium by long term I mean billions of years,

I am slightly curious how you computed this.  Even without growth, I
have never seen estimates for how long thorium will last that exceed a
few centuries.

Not that it makes a lot of difference.  Whatever we turn into over the
next 5-10 decades can solve their own problems.

Keith