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Solar Energy Per Square Foot In Temperate Zone?

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Posted by (PeteCresswell) on September 21, 2009, 12:13 am

It's always been in the back of my mind that one of the jokers in
the energy-shortage deck is the prospect of somebody coming up
with some really-cheap, really-efficient means of converting sun
to electricity.

But; engineering question, I guess; how much power is actually
available on, say, a 2,000 square foot roof in, say Pennsylvania?

i.e. Is there enough solar energy falling on that roof to make a
significant dent in electric consumption if the efficiency of the
photovoltaics is sufficient?    

Or are the numbers just not there no matter what?

Posted by Bruce Richmond on September 21, 2009, 12:48 am

If you covered the roof and had batteries to take you through the
night it should take care of all your needs.

Posted by RamRod Sword of Baal on September 21, 2009, 2:06 am

Then Bruce wrote
If you covered the roof and had batteries to take you through the
night it should take care of all your needs.


Of course then you would have to find enough money to buy the PV panels; the
batteries; the inverter, plus the installation costs.

Then you would have to meet the ongoing maintenance costs like replacing the
very expensive batteries every few years.


Friends of mine live in a isolated country area where there is no mains
electricity, they went solar, the actual cost was around $AUS 23,000. The
equipment will run their lights, fridge and TV, They have an electric
washing machine but they tell ne they can only use it when there is bright
sunshine outside.

They did get a Government rebate so their actual cost was less than the
$3,000, I have an idea they had to cough up about 14 grand out of their own

There is no way they can run any high drain equipment from they solar
equipment like air conditioning or heating.

I have a system that is not solar, just 4 x 6 volt T 105  batteries, a 40
amp battery charger and a 2.5 KW 240 volt inverter.

It gets little use and the batteries although were kept charged packed up in
4 years.

They cost around $AUS 800.00 for the 4 (About $US 700.00)

Yes, I know these batteries are cheaper in the USA.

Posted by Bruce Richmond on September 21, 2009, 4:21 am


Did you miss the part about "somebody coming up with some really-
cheap, really-efficient means of converting sun to electricity."?

OK I'll grant you that batteries are not particularly cheap, but there
are other ways as well.  If you are on the grid you can just feed the
power into the grid during the day and draw from it at night.  Many
states require electric utilities to offer net metering.  So with the
roof covered all you would have to pay the utility would be the basic
connect charge.

There is another thread in this group discussing this site that offers
panels for $.98 per watt.


Another link in that thread provides this analysis.


"he predicts, could drop below $ a watt next year, and to 50 cents a
watt in 2011."

The cost of power from the grid is climbing and may climb quickly if a
carbon tax is pushed through.  And the grid has become less reliable.
If you could put 15 KW of PV on the roof for cheap and use net
metering it could save you some money.  And a small bank of batteries
could provide emergency power in the event of a night time power
outage.  Where they wouldn't be getting drained at all except for
during power failures they should last much longer than if cycled
every day.

Posted by vaughn on September 21, 2009, 1:10 am

Go here:

Select "horizontal flat plate".  Use your own assumption for PV panel


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