[ExI] Comment for Scientific American

John Clark johnkclark at gmail.com
Mon Oct 5 23:01:37 UTC 2015

On Mon, Oct 5, 2015  Keith Henson <hkeithhenson at gmail.com> wrote:

>> 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.

​I agree, space would help a little at solving the dilution problem, but it
would make the power distribution problem much worse.  ​

>> ​>​
>> 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.

Thorium is much more common than Uranium, in fact it's almost twice as
common as Tin
​,  ​
Thorium has only one isotope and
​ unlike Uranium ​
a Thorium reactor can
 100% of it.

f at random you picked one cubic meter of rock anywhere
 the Earth's crust you would find about 12 grams of
Thorium in it
if placed i
​t in​
a Thorium reactor
12 grams would produce the energy equivalent of 37 tons of coal, enough to
power one person's western middle class lifestyle for about a decade. One
ton of
horium contains as much energy as 3 million tons of coal
​ U S
Geological Survey's latest estimate says that
one company, Thorium Energy Inc, has 915,000 tons of
Thorium reserves in Idaho and Montana. That alone could replace coal for
about 450 years, and that's just from the claims that one company has in 2
states. And Norway has as much Thorium as the entire USA, and Australia
about twice as much, and India has about 3 times as much.

It would only take 2000 tons of Thorium to equal the energy in 6 billion
tons of coal that the world uses each year. There is 120 TRILLION tons of
Thorium in the earth's
crust and if the world needs 10 times as much energy as we get from just
coal then we will run out of Thorium in the crust
 this planet in 6 billion years.
​ ​
And we've already discovered Thorium deposits on the Moon and Mars.

​ John K Clark​
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