[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
​use​
 100% of it.

​I​
f at random you picked one cubic meter of rock anywhere
​on​
 the Earth's crust you would find about 12 grams of
​
Thorium in it
​,
if placed i
​t in​
a Thorium reactor
​
those
​
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
​T​
horium contains as much energy as 3 million tons of coal
​,​
​
and
​t​
h
​​
e
​ U S
Geological Survey's latest estimate says that
​
just
​
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
​of​
 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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