Solar Energy Per Square Foot In Temperate Zone?

[(PeteCresswell)]

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?

 

[vaughn]

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

Go here:
http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/

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

Vaughn

 

[Martin Riddle]

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?

The amount of wattage that strikes 1 square meter is about 800w.
Solar cell efficiency is about 15-20%.
Wiring and inverter losses (grid tie) is another 10%.

So worst case, 160w*0.70= 112w per square meter.

2000^2ft = 185^2m

185 * 112 = 20720watts

Now, you figure out the actual numbers with real parts.
Figuring spacing and mounting issues it is closer to 15000w

For your location, you need to look up the insolation, or rather the
number of average hours of sun per day.

now you have watt hours.

Cheers

 

[RamRod Sword of Baal]

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?

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
$23,000, I have an idea they had to cough up about 14 grand out of their own
pocket

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.

 

[sno]

Go here:
http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/

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

Vaughn

Most of what I have heard/read from those who have really made a study
of it, is that until panels come down to around 1.00 per watt they are
not economical...of course if you live away from power lines and you
would have to pay for a line to be run to your house, at present prices
they may be....also rebates from government may be enough to bring the
price down...

It is my understanding that Germany has a law that requires the power
companies to pay for electricity from solar panels. at the same rate
they charge for electricity....for this reason they are installing
solar panels on a lot of roofs...so they are probably economical there
at todays prices.....also remember the price is not just the panels...

As others have mentioned a normal roof can produce enough electricity to
run a house....even in the northern states...especially if the house is
well insulated...and attention is paid to usage...

hope helps...have fun....sno



--
Correct Scientific Terminology:
Hypothesis - a guess as to why or how something occurs
Theory - a hypothesis that has been checked by enough experiments
to be generally assumed to be true.
Law - a hypothesis that has been checked by enough experiments
in enough different ways that it is assumed to be truer then a theory.
Note: nothing is proven in science, things are assumed to be true.

 

[(PeteCresswell)]

Per Martin Riddle:

The amount of wattage that strikes 1 square meter is about 800w.
Solar cell efficiency is about 15-20%.
Wiring and inverter losses (grid tie) is another 10%.

So worst case, 160w*0.70= 112w per square meter.

2000^2ft = 185^2m

185 * 112 = 20720watts

Seems like my 'joker-in-the-deck' is at least possible then -
unless some basic law(s) of physics preclude higher efficiencies.

Double that efficiency and you've got 4kw possible....

Seems like I read about a project somewhere (in Europe?)
dedicated to exploring something like "The two-kilowatt
lifestyle" where everybody on the planet lives a reasonable life
on a total (sustainable?) energy consumption of two
kilowatts/hour/24-7.

 

[bw]

Per Martin Riddle:

Seems like my 'joker-in-the-deck' is at least possible then -
unless some basic law(s) of physics preclude higher efficiencies.

Double that efficiency and you've got 4kw possible....

Seems like I read about a project somewhere (in Europe?)
dedicated to exploring something like "The two-kilowatt
lifestyle" where everybody on the planet lives a reasonable life
on a total (sustainable?) energy consumption of two
kilowatts/hour/24-7.

You don't specifiy your current consumption. Common value for that is over
10 kWh per day.
http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/serve.cgi
Shows you will get about 3 kWh/m2 per day of solar in December and January.
You will need 10 square meters of panels to convert solar input to the same
value electrical.
You will never recover the cost of the panels if you live outside the
southwest USA, unless the cost of your electrical power from the grid starts
to get close to one dollar per kWh.

 

[(PeteCresswell)]

Per bw:

Shows you will get about 3 kWh/m2 per day of solar in December and January.
You will need 10 square meters of panels to convert solar input to the same
value electrical.
You will never recover the cost of the panels if you live outside the
southwest USA, unless the cost of your electrical power from the grid starts
to get close to one dollar per kWh.

Understood.

I was thinking in terms of what hope there might be globally for
the future - and it sounds to me like if somebody comes up with
really-cheap, really-efficient photovoltaics there's some hope
there of making a significant dent in the energy situation.

The operative word, of course is "If".... but at least it sounds
like the energy per square meter is there.