posted on Jan, 15 2005 @ 11:22 PM
wyrde one says:
"New Photovoltaic panels are 300% more efficient than models from 3 years ago."
When I was in the systems engineering department of Solavolt International in the late 1980's, our standard MSVM4010 PV modules were about 11 percent
Going to the websites, the typical home PV module, according to DOE, is about 12 to 15 percent -- hardly a 300 percent increase in efficiency since
fifteen years ago.
Now it's true that Spectrolab (a Boeing subsidiary) has produced PV cells with an efficiency of 34 percent, but they are not widely available, and
are extremely expensive.
And finally, think about this. Even if we had a hundred percent efficiency cells, a module would produce 1 kW/M^2 under "full sun"
conditions, which is summer noon in the Sonoran Desert.
Now I live smack dab in the middle of the desert, and a typical summer day is 5.3 hr of full sun, with winter providing 4.6 hr. That means, under
summer conditions here in Mesa, my "perfect" module (which doesn't exist) would produce 5.3 kW-hr, which will run stuff, but not enough to run the
stuff in a typical suburban house, like air conditioning, a vacuum cleaner, a stove, an iron or even a hair dryer.
But wait, there's more!
Most of our electricity usage is when we're home, which is usually at night,w hen there isn't any sun. This means your PV array will have to
twice as big as you originally thought, so that you can produce your daylight electricity and produce energy to store up in your batteries,
which will, by the way, double your cost.
And the most cost-effective batteries troday are still lead-acid batteries which cannot be discharged more than about 30%/cycle or they'll
crap out in a big hurry. So you have to have between three and four times the nominal number of batteries (based on their AH rating) to provide you
with electricity through the night.
And those lead acid batteries, even if you take care of them, have to be replaced every five years at a very large cost, and the main components of
such batteries, are, of course. lead and H2SO4 -- hardly neat stuff to stick in your landfill!
And we haven't talked yet about designing in system autonomy to provide for those four or five days of rainy weather, and the work that you, Mister
Typical Homeowner, will have to do to be your own Electric Utility General Manager and Technical Lead.
I've designed a lot of small scale remote/rural PV systems, and have even travelled to Central America to help install them. I love PV and
would love to see it fly.
But it can't; it's simply not cost-effective (yet) to compete with the major grid providers. I'm afreaid that PV will be little more than a niche
player for the foreseeable future.