Sunday, May 11, 2008

Solar power

Rand Simberg has an interesting article on solar power
being generated by a new technique by a company called
Sunrgi. I have some doubts, here's what i commented:

my bet is that the sunrgi system is vaporware.

I took a solar installation class about 7 years ago and someone in the class asked why concentrators weren't used to focus sunlight on the pv panels. The instructor said that the thermal characteristic of solar cells gives higher resistance at higher temperatures, and you really want to do everything you can during the design phase to keep the array cool.
I think this would be a low efficiency pv with some solar thermal mixed in. Since they specifically mention their cooling system extends cell life, they are probably (rightly) worried that the higher temp will degrade the cells. The economics of pv depends on the panels lasting 30 years, if you have to disassemble an array with a bunch of lenses on top every 5 years and replace the modules, it's not going to be cheap. [pv cost/hr = (equipment + installation)/ (# of hours the system will work) + maintenance] (it works like an oil well, you spend $20k to build a system, it give you 5 hours of full power per day for 30 years]. eg, for a 2KW pv that cost $20k over 30 years = $.18/kWh.

of course I hope their product is perfect and I can stick a 4 kw plant in my backyard in 5 years for $30k.


The main problems with PV are still the same ones that it has always
had, it is really expensive to generate a lot of electricity and it's really expensive to store electricity. If you want 500 watts available 24 hours you can do that
for $10000, but if you want 4000 watts available 24 hours, then you
need to cover a lot of space with pv, and store it somewhere. As the
batteries scale up, things get expensive. It's too expensive to run A/C with PV.

The best way to do solar power is look at the loads first, use gas for
thermal loads, use fluorescents for lighting and get rid of thief loads
like instant on tv's and vcrs. Turn off everything at the power strip
when not in use. Now that you've improved things by 5%, tackle the
real problem, which is Air conditioning. If you live in the mountains
or in the northeast, you're done, size the panels for your reduced electric
load and use a line-tie system. If you're in the southeast, look at a
groundcoupled heatpump, or go back to the ceiling fans on the front
porch technique.

What is really going to drive this revolution is extremely high power costs.
People aren't like oil companies that see an 8% return as good deal, people
want instant certain payback, and that will only happen when pv is cheaper
than oil with a repayment cost in just a couple of years, not 22. Plug in hybrids
will be another driver, when people can use a huge battery pack and charge it
from the roof, that'll make things change.

If the price of oil can stay high for another 5 years, then the US will be radically
different at the end of that time power-wise. The more likely outcome will be
that the economy will continue to slow, we'll stop buying plastic chinese crap, then
they'll slow down, and the price of oil will head back to 12 dollars, resetting the
system again at 1980.

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