[Tfug] OT: Big Oil? Windows Vista!

[Ronald Sutherland]

The monocrystalline panels I tried make a peak power output of 80W when
pointed straight at the sun, so no insolation effects, at least if I under
stand that correct. If I assumed 1000 watts/m^2 during that peak (duplicated
on many clear days) then I can add up the area of silicon and get an
efficiency, I recall something like 14%, but when I add up the full area of
the panel (it has unused space) I get about 8%. I did not think there are
any big PV based systems doing any where near 20% conversion (that is light
in to DC out, never mind any inverter losses to get AC), but it looks like
I'm wrong.

http://en.wikipedia.org/wiki/Solar_cell

That Springerville generating station with 34,980 modules (MST-43) each is
26" x 48"
1248 in^2 = 0.805 m^2

34980 * 0.805 = 28158 m^2 off pv area or 28,158,000 W at 1000 W/m^2

if we discount 20% for insolation effects we have (they are at an angle so
not sure on this)
22,527,000 W of solar radiation hitting the pv
the pv is rated at 4,590 kW DC
so the efficiency is 20% ???? wow that is much better
than I would have thought possible.

Kramer Junction solar power plants are steam turbine Rankine cycle not
Brayton. Oil is pumped into the solar absorbers at the focal point of the
parabolic trough (371 deg C) and then back to the boiler to make steam (at
night CH4 is burned to make steam).

The carnot engine is the ideal, in other words no heat engine can do better
(although reusing waste heat is possible). So the best possible heat engine
could get 51.3% out of a heat difference of 371C and 40.5C.

http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/carnot.html

There is a lot of room for improving heat engines. Also Solar cells have an
important place but I don't think we should lose sight of the fact that they
cost so much energy to make.


On Sat, May 31, 2008 at 11:11 AM, johngalt1 <johngalt1 at uswest.net> wrote:

> That explanation is spot on.  Thank you.
>
> I challenge anyone to substantially refute the assertions or
> facts contained in the previous message.
>
> It is interesting that 20 percent is cited as the efficiency
> in conversion of insolation
> http://en.wikipedia.org/wiki/Insolation
> to DC electricity via photovoltaic panels. I note this
> because that is the same efficiency as the world's largest
> solar electric plants...
> http://en.wikipedia.org/wiki/SEGS
> http://www.fplenergy.com/portfolio/contents/segs_viii.shtml
> ...with Brayton cycle heat engines employing
> sophisticated turbomachinery and heat transfer methods.
> http://www.flagsol.com/SEGS_tech.htm
> http://www.p2pays.org/ref/22/21026.pdf
>
> Unfortunately, what this means is that most of the solar
> power collected is wasted.
> There is no evil, villianous oil company to blame on that
> one... The reason for that is simple applied physics.
>
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