Malcom "Mal" Reynolds wrote:

Giggle. Those who think we can run this country - or a significant
part of it - off of sunbeams (or windmills) are disturbed.

Don't get me wrong, these alternatives do have their use, mainly in
helping liberals feel good.

It's interesting to note that the Dutch long ago switched from
windmills to electric pumps. So much for THAT idea.

and just exactly how many new power plants have they built in the
last 30 years?

I don't know. Sufficiently many, I presume.




As for PVs, the amount of the sun's radiation falling on the earth
is about 1350 watts / sq meter. At the equator. At noon. With no
clouds.

Assuming a PV collector running at 50% efficiency (ha!) and
adjusting for latitude, 12 hours of darkness, clouds, etc., it would
take a solar collector farm the size of the Los Angeles basin (~1200
sq miles) to provide 55GW of power just for California*. Can you
imagine the cost to construct 1200 sq miles of anything? Let alone
maintenance.

but really you only need to replace the equivalent of a power plant
here and there and there are plenty of office buildings in LA and
elsewhere where you could cover the roof with significant amounts of
PV that would power a percentage of the building plus provide cooling
in the form of shade AND then provide electricity on the 175 days a
year that the office building isn't being used


You make a good point; electricity for an office building is severely
curtailed at night. So, let's figure it out.

Last week, the first "skyscraper" to be built outside of downtown Houston
was blown up. Using it as an example, let's do some math.

The building was 20 stories and comprised 500,000 sq ft. That's 25,000 sq ft
per floor and, presumably, the roof. That's a bit more than 2300 sq meters.
If the building was at the equator, it would receive almost 800,000 watts of
radiation from the sun. Adjusting for latitude (-30%) and efficiency of the
solar collectors (~30% tops), we get total usable energy of about 167,000
watts. Cloud cover - an unknown - would diminish the value further.*

A modern building will draw on the order of 1.5 million watts (6MW for 2
million sq ft).

So, then, a back-of-the-envelope calculation indicates the the roof of our
departed building could reduce its energy requirements by 11%. But at an
installation cost of $4.00/watt, we're in the neighborhood of $650,000.00.
Saving $0.15/kwh contrasted with the opportunity cost of 650 thou (earned
interest), I doubt the project would EVER pay for itself.

But it would make liberals "feel" better.

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* Using the average insolation values for Texas, the amount of energy is 4
kwh/m^2.