🚀 go-pugleaf

In <30E0AFD5.41F5@mti.sgi.com> James Salsman <jps@mti.sgi.com> writes: 
>
>John McCarthy wrote:
>> 
>> I would guess James Salsman misinterpreted or misread the
>> Exploratorium poster.
>
>Either that or everyone else is assuming that I am talking about 
>terrestrial collectors. <:-/ Sorry for my impertinance, Professor.
>
>I suspect that masering energy from Mercury orbit to a parabolic
>collector on the moon and then back to collectors on earth would 
>be more efficient than an L5 collector.  Of course, that's a ways 
>down the road.
>
>For terrestrial collectors, I revise from about five square 
>kilometers to about 100,000 (based on the up-to-date efficiency 
>and weather factors from other posters.)  That's a square 
>200 miles on each side, or about 1/20th the area of Saudi Arabia, 
>or 2/5th of Nevada.  Again, that's to serve the electrical power 
>needs of everyone on the planet, and it's all solid state, 
>zero-emission renewable (at least for the next 3 billion years)
>technology.
>
>Sincerely,
>:James Salsman

Perhaps, but Mr. Waltz is correct when he points out that it takes more
energy to make a solar cell, using current technology, than it can
return in it's entire life.  Also, the cells do not last forever.  They
are degraded by the UV exposure, weather, oxygen, etc.  The cost to
fabricate and maintain a 1000 square kilometer expanse of solar cells
would be prohibitive, let alone 100,000.  Granted that improvements in
technology may eventually let the solar cell produce a net energy gain
in it's lifetime, but still, let's be practical.