Alternative Power sources - Re: Home Solar System Cost??

Author

Re: Home Solar System Cost??

nicksanspam@ece.villanova.edu

2005-07-19, 11:25 pm

BobG <bobgardner@aol.com> wrote:

quote:

>The payback for several thousands of dollars at a dollar or less per
>day is over 10 years no matter how many times I tweak the spreadsheet.
>It aint a money makin investment.

Sounds like you are talking about PVs vs sunspaces for house heating,
which can be 100X cheaper per peak watt. I'll be giving a talk to that
effect and PE Drew Gillett and PhD Rich Komp and I will likely be giving
a workshop on "Solar Heating and Natural Cooling" at the PA Renewable
Energy Festival on 9/24/05 in Kempton, PA, 15 miles west of Allentown
and 10 miles north of Reading. See

http://www.PAenergyfest.com

Nick

San Francisco

2005-07-24, 9:05 pm

>
> Sounds like you are talking about PVs vs sunspaces for house heating,
> which can be 100X cheaper per peak watt. I'll be giving a talk to that
> effect and PE Drew Gillett and PhD Rich Komp and I will likely be giving
> a workshop on "Solar Heating and Natural Cooling" at the PA Renewable
> Energy Festival on 9/24/05 in Kempton, PA, 15 miles west of Allentown
> and 10 miles north of Reading. See
>

this is very misleading and erroneous

sun spaces can help some in winter, but they also hurt to a degree in
summer, an overall gain due to overhangs, but a slight one

and giving figures like "100X cheaper" makes you look ridiculous and silly

the only solutions that have shown much promise of any great savings are
some of the interactive ones, such as a computer controlled roof that
changes it's color from black to white with the seasons.

but no combination of design technologies can make your power bill 100X
cheaper, or even 10X cheaper

you don't help our green cause by spouting silliness

S.F.

pjm@see_my_sig_for_address.com

2005-07-24, 9:05 pm

On Tue, 19 Jul 2005 21:58:36 -0400, "San Francisco" <sf@sf.com> wrote:

>
>
>this is very misleading and erroneous
>
>sun spaces can help some in winter, but they also hurt to a degree in
>summer, an overall gain due to overhangs, but a slight one
>
>and giving figures like "100X cheaper" makes you look ridiculous and silly

Like the rest of his pompous bullshit.

>
>the only solutions that have shown much promise of any great savings are
>some of the interactive ones, such as a computer controlled roof that
>changes it's color from black to white with the seasons.
>
>but no combination of design technologies can make your power bill 100X
>cheaper, or even 10X cheaper
>
>you don't help our green cause by spouting silliness
>
>
>S.F.
>
>

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nicksanspam@ece.villanova.edu

2005-07-24, 9:05 pm

San Francisco <sf@sf.com> wrote:

http://www.PAenergyfest.com
[color=darkred]
>this is very misleading and erroneous

A 4-year layer of poly film costs 5 cents per square foot and collects
about 225 Btu/h-ft^2 (66 W/ft^2.) That's $0.05/66 = $0.00076 per peak
watt... $4/$0.00076 = 5275 times cheaper than $4/pW PVs.

>sun spaces can help some in winter, but they also hurt to a degree in
>summer, an overall gain due to overhangs, but a slight one

A sunspace can help a LOT in wintertime. Ever heard of the Barra system?

>and giving figures like "100X cheaper" makes you look ridiculous and silly

It might be more accurate to say "5275X cheaper" :-)

>the only solutions that have shown much promise of any great savings are
>some of the interactive ones, such as a computer controlled roof that
>changes it's color from black to white with the seasons.

I disagree. Ever heard of John Hait, Norman Saunders, Harry Thomason, or
John Christopher (and his 98% solar-heated CSI building in New Hampshire)?

>but no combination of design technologies can make your power bill 100X
>cheaper, or even 10X cheaper

A large wire loop under a power line might help.

>you don't help our green cause by spouting silliness

You might enjoy our workshop.

Nick

Gary

2005-07-24, 9:05 pm

San Francisco wrote:
>
>
> this is very misleading and erroneous
>
> sun spaces can help some in winter, but they also hurt to a degree in
> summer, an overall gain due to overhangs, but a slight one
>
> and giving figures like "100X cheaper" makes you look ridiculous and silly
>
> the only solutions that have shown much promise of any great savings are
> some of the interactive ones, such as a computer controlled roof that
> changes it's color from black to white with the seasons.
>
> but no combination of design technologies can make your power bill 100X
> cheaper, or even 10X cheaper
>
> you don't help our green cause by spouting silliness
>
>
> S.F.
>
>
>
I'm not that familiar with sunspaces, but for simple solar thermal
heating systems that use conventional solar collectors, the 100X
difference in the cost per peak watt seems in the ball park to me:

PV systems cost around $10 per peak watt. That is, a 1KW system costs
around $10000, where 1 KW means it generates it generates 1KW in full
(1000 watt/m^2) sun.

There are lots of ordinary solar thermal space and water heating
systems designs that come in between $30 and $100 per sqmeter of
collector area. If you evaluate the cost of these systems per peak
watt (as PV systems are evaluated), then the cost per peak watt is around:

Cost per peak watt = ($80/m^2)/(1000w/m^2)(0.6efic) = 0.13 $/peak watt

Thats a ratio of $10/$0.13 = 75X, and you could certainly do better
than this with some systems.

Gary

www.BuildItSolar.com
gary@BuildItSolar.com
"Build It Yourself" Solar Projects

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Anthony Matonak

2005-07-24, 9:05 pm

nicksanspam@ece.villanova.edu wrote:
> San Francisco <sf@sf.com> wrote:
>
>
>
> A 4-year layer of poly film costs 5 cents per square foot and collects
> about 225 Btu/h-ft^2 (66 W/ft^2.) That's $0.05/66 = $0.00076 per peak
> watt... $4/$0.00076 = 5275 times cheaper than $4/pW PVs.

If you're going to compare a 4-year option to a 50+ year option
then I think you should also factor in the number of times it
needs to be replaced and installation labor. This means the least
it'll cost (disregarding labor) is $0.05/66*50/4 = .0095 and
$4/$0.0095 = 421 times cheaper. Let's say labor doubles's your
costs as it needs to be done every few years and it's now at
some 210 times cheaper. If you use something a little more durable
(more expensive) than poly film then conceivably it's even less
cost effective.

Anthony

Derek Broughton

2005-07-24, 9:05 pm

nicksanspam@ece.villanova.edu wrote:

> BobG <bobgardner@aol.com> wrote:
>
>
> Sounds like you are talking about PVs vs sunspaces for house heating,
> which can be 100X cheaper per peak watt.

Absolutely. PV isn't the way to generate your electricity if you have
practically _any_ alternatives. otoh, passive solar heating - when
designed into a new building - is free, and even solar hot water has a
reasonable amortization.
--
derek

Derek Broughton

2005-07-24, 9:05 pm

San Francisco wrote:

>
> this is very misleading and erroneous
>
> sun spaces can help some in winter, but they also hurt to a degree in
> summer, an overall gain due to overhangs, but a slight one

BS. When properly designed, they don't cause a problem in summer either.
And it isn't the overhangs, it's the angle of incidence.

> and giving figures like "100X cheaper" makes you look ridiculous and silly

Work it out. Electricity: 10c/kWh (at a minimum), Gas: less, but still
costly, Solar: free. 100x cheaper is easy to accomplish. Passive solar
heating doesn't have to cost a dime. That's not to say that your fuel
saving will be 100X cheaper - it means that the portion of your heating
supplied by solar is cheaper. The best designed passive solar homes I've
seen still supply about 30% of their heat with an alternate source.

> the only solutions that have shown much promise of any great savings are
> some of the interactive ones, such as a computer controlled roof that
> changes it's color from black to white with the seasons.

LOL. Another high-tech waste of money. My friend, Don Roscoe, has been
designing solar heated homes for 3 decades now, and he hasn't had
overheating problems since the very early days.
--
derek

nicksanspam@ece.villanova.edu

2005-07-24, 9:05 pm

Anthony Matonak <anthonym40@nothing.like.comcast.net> wrote:

>
>If you're going to compare a 4-year option to a 50+ year option
>then I think you should also factor in the number of times it
>needs to be replaced and installation labor. This means the least
>it'll cost (disregarding labor) is $0.05/66*50/4 = .0095 and
>$4/$0.0095 = 421 times cheaper. Let's say labor doubles's your
>costs as it needs to be done every few years and it's now at
>some 210 times cheaper.

Gee, only 210 times cheaper :-) Labor is about 0.01 cents/ft^2, according
to greenhouse supplier Stuppy. Greenhouse poly film comes in huge rolls,
eg 40'x150', so it's easy to replace, on a calm day.

>If you use something a little more durable (more expensive) than poly film
>then conceivably it's even less cost effective.

Possibly. Polycarbonate costs about $2/ft^2 and lasts about 20 years.
OTOH, it's clear like glass. Other factors include adding potentially
valuable floorspace to a house. And I only counted solar gain vs
simultaneous loss, which might be half the gain.

news@pointerstop.ca wrote:

http://www.PAenergyfest.com
[color=darkred]
[color=darkred]
[color=darkred]
>BS. When properly designed, they don't cause a problem in summer either.
>And it isn't the overhangs, it's the angle of incidence.

Ventilation and shading (eg shadecloth or awnings or grapes) can also help.
And there would be an insulated wall between the low-thermal mass sunspace
and the house, so it wouldn't add much heat to the house in summertime.

[color=darkred]
>Work it out. Electricity: 10c/kWh (at a minimum), Gas: less, but still
>costly, Solar: free. 100x cheaper is easy to accomplish. Passive solar
>heating doesn't have to cost a dime. That's not to say that your fuel
>saving will be 100X cheaper - it means that the portion of your heating
>supplied by solar is cheaper. The best designed passive solar homes I've
>seen still supply about 30% of their heat with an alternate source.

Keep looking. Check out the Barra system, or look up John Christopher's CSI
building (heated with 98% solar power and 2% fan power)in New Hampshire.
Most "solar houses" are designed with faulty rules of thumb, vs engineered.
PE Norman Saunders has been designing houses that are close to 100% solar-
heated in cold cloudy New England since 1946. They have long track records
with digital data loggers. He's an EE by training, and also invented a very
early 5-bit computer :-)

Cloudy days are like coin flips. If a house can only store 1 day's worth
of heat (beyond the reach of most "solar houses"), it can be at most 50%
solar heated... 2 days allows 75% max; 3, 88%, 4 94%, and 5, 97%.

Nick

Derek Broughton

2005-07-24, 9:05 pm

nicksanspam@ece.villanova.edu wrote:

> news@pointerstop.ca wrote:
>
>
> Keep looking. Check out the Barra system, or look up John Christopher's
> CSI building (heated with 98% solar power and 2% fan power)in New
> Hampshire. Most "solar houses" are designed with faulty rules of thumb, vs
> engineered. PE Norman Saunders has been designing houses that are close to
> 100% solar- heated in cold cloudy New England since 1946. They have long
> track records with digital data loggers.

No doubt. Don's houses were originally built with those same rules of
thumb. He's a civil engineer and architect, but he's not allowed to join
the architectural profession because he actually gets his hands dirty and
_builds_ houses. He also sells to people who want to build big - and
overheated - houses. They definitely don't need an extra heat source to
stay frost-free, but they need extra heat to keep them over 20C.
>
> Cloudy days are like coin flips. If a house can only store 1 day's worth
> of heat (beyond the reach of most "solar houses"), it can be at most 50%
> solar heated... 2 days allows 75% max; 3, 88%, 4 94%, and 5, 97%.

And same for cooling. As Don points out, modern houses have enough thermal
mass to store about two weeks of heat, it's just a matter of getting the
heat into that mass.
--
derek

nicksanspam@ece.villanova.edu

2005-07-24, 9:05 pm

Derek Broughton <news@pointerstop.ca> wrote:

>...modern houses have enough thermal mass to store about two weeks of heat,
>it's just a matter of getting the heat into that mass.

And keeping it in. With enough insulation, we could store two weeks of heat
in a pinhead.

Nick

Derek Broughton

2005-07-24, 9:05 pm

nicksanspam@ece.villanova.edu wrote:

> Derek Broughton <news@pointerstop.ca> wrote:
>
>
> And keeping it in. With enough insulation, we could store two weeks of
> heat in a pinhead.

LOL. I suppose you're right, but concrete easily stores a couple of weeks
of heat without needing overlarge amounts of insulation (we use 6" slabs
over 3" styrofoam). You'd need a whole lot more insulation than that to
store it in a pin-head :-)
--
derek

John P Bengi

2005-07-24, 9:05 pm

You need a much higher temperature.

Now the whole neighbourhood can see your house glow, through the insulation.

"Derek Broughton" <news@pointerstop.ca> wrote in message
news:k675r2-j5l.ln1@othello.pointerstop.ca...
> nicksanspam@ece.villanova.edu wrote:
>
>
> LOL. I suppose you're right, but concrete easily stores a couple of weeks
> of heat without needing overlarge amounts of insulation (we use 6" slabs
> over 3" styrofoam). You'd need a whole lot more insulation than that to
> store it in a pin-head :-)
> --
> derek

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