solar powered motor

[John M]

I'm a newbie with electronics, but I am looking at powering a 12V 4A fan
with an 85W solar panel like this one:

http://www.ul-solar.com/product_p/stp085p-tls.htm

I believe I would need a device like this to condition the power source:

http://shop.ata.org.au/cart.php?target=product&product_id=16327&category_id=251

Should I be concerned about exceeding the fan amp rating or am I being too
optimistic?

Thanks,
John M
Houston, TX



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[John M]

Oopsies, that should say "120V 60Hz 4A fan motor"

"John M" <jmcculloch@academicplanet.com> wrote in message
news:itjudp$1rd6$1@adenine.netfront.net...

I'm a newbie with electronics, but I am looking at powering a 12V 4A fan
with an 85W solar panel like this one:

http://www.ul-solar.com/product_p/stp085p-tls.htm

I believe I would need a device like this to condition the power source:

http://shop.ata.org.au/cart.php?target=product&product_id=16327&category_id=251

Should I be concerned about exceeding the fan amp rating or am I being too
optimistic?

Thanks,
John M
Houston, TX


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news@netfront.net ---

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[Jon Kirwan]

On Sat, 18 Jun 2011 23:37:19 -0500, "John M"
<jmcculloch@academicplanet.com> wrote:

I'm a newbie with electronics, but I am looking at powering a 12V 4A fan
with an 85W solar panel like this one:

http://www.ul-solar.com/product_p/stp085p-tls.htm

I believe I would need a device like this to condition the power source:

http://shop.ata.org.au/cart.php?target=product&product_id=16327&category_id=251

Should I be concerned about exceeding the fan amp rating or am I being too
optimistic?

I gathered from your later post that this is a 120VAC, 4A
fan. That's 4*120 or about 500 watts, total. It's certain
you will need more than one 85 watt solar panel to run it.
Also, solar panels are usually DC and have a rated output
voltage and current at some expected solar irradiance and
incidence to the panel. If they are rated 85 watts, it may
be that this is only in optimal conditions at the equator,
with no clouds or dust, and assuming 1000W/m^2 of sun. In
Texas, maybe 30N of the equator, you can expect somewhat less
as the cosine(30) is about 87%. And that's at high noon. So
you may need to "derate" the numbers to make certain you buy
enough panel area.

So, taking a look at the panel you linked. It shows "Power
at STC" of 85W. What is STC? Well, it's that 1000W/m^2 I
just mentioned above. The sun puts out about 1364 W/m^2 at
Earth's distance from the sun. The Earth reflects away about
30% of that, leaving about 960 W/m^2. At the equator when
the sun is directly overhead. Well, that's not going to
happen in Texas, hot as it may seem sometimes. You need to
derate the panel. You can probably call up your local power
company and get better figures for your area, but you can
make some rough estimates. At noon, you might expect about
85% of 85 watts or about 72 watts. But figuring over some
useful time during the day, you should expect even less.
More, if the panel runs hot (and it will), the rating gets
worse as panels deliver -80mV/C, above 25C. Call it 60 watts
as a realistic figure for now. On good days. That tells you
that you will need 9 or maybe even 10 of them to run the
motor.

You will need a converter (inverter) of some kind. However,
the one you linked, I think, may be described on this page in
more detail:

http://www.suburbia.com.au/~mickgg/minimax/minimax.htm
http://www.suburbia.com.au/~mickgg/minimax/veroboard.htm

It works best, according to the author, at an input supply no
more than 17V. (Says, 10.5V to 17V.) It doesn't do any
voltage boosting, nor 60Hz AC inverter stuff, so it really
won't drive a 120VAC motor. Even if the power situation
worked out. (The schematic there above looks a lot like what
would be associated with the product you linked.)

You need to look for a device that can deliver 500 watts of
60Hz AC power, sourced from DC solar panels that can actually
provide MORE than 500 watts at your location and time of
operation. You may want a true sine wave inverter, not a
modified sine wave inverter, as you are driving a motor.

None of this is going to be entirely cheap.

Solar panels delivering power synchronized to the AC system
of a home are about $8.5/watt when installing under 10kW, in
California:

http://www.californiasolarstatistics.ca.gov/

A recent publication for my state, Oregon, shows a figure of
$22,500 for 3kW as a "market average" before federal and
state tax credits are accounted for. That $22,500/3kW works
out to about $7.5/watt.

Assuming a similar figure, you would be looking at 500 times
$8.5 (or $7.5) or about $4,250.00 (or $3,750.00) to run your
motor. You don't need the synchronization if the motor is
the only thing hooked to it. So it will be cheaper. But I
would expect more than $2,000.00. But this may be made much
better depending upon your tax situation, current fed and
state tax incentives, etc.

Maybe someone better informed can add their thoughts or
correct mine.

Jon

 

[Nobody]

On Sun, 19 Jun 2011 00:09:31 -0700, Jon Kirwan wrote:

Also, solar panels are usually DC and have a rated output
voltage and current at some expected solar irradiance and
incidence to the panel. If they are rated 85 watts, it may
be that this is only in optimal conditions at the equator,
with no clouds or dust, and assuming 1000W/m^2 of sun. In
Texas, maybe 30N of the equator, you can expect somewhat less
as the cosine(30) is about 87%. And that's at high noon.

That's assuming that the panel is horizontal. If it's oriented directly
toward the sun, cos(a) is 1 regardless of latitude and time of day.
These still affect atmospheric absorption, but that's less significant
than cos(a) (k^(-sec(a)) as a first approximation).

 

[Nobody]

On Sat, 18 Jun 2011 23:47:19 -0500, John M wrote:

I'm a newbie with electronics, but I am looking at powering a 12V 4A fan
with an 85W solar panel like this one:

Oopsies, that should say "120V 60Hz 4A fan motor"

Slight difference

12V*4A = 48W, which is feasible given enough sunlight.
120V*4A = 480W, which isn't feasible under any circumstances.

 

[Rich Webb]

On Sun, 19 Jun 2011 00:09:31 -0700, Jon Kirwan
<jonk@infinitefactors.org> wrote:

On Sat, 18 Jun 2011 23:37:19 -0500, "John M"
jmcculloch@academicplanet.com> wrote:

I'm a newbie with electronics, but I am looking at powering a 12V 4A fan
with an 85W solar panel like this one:

http://www.ul-solar.com/product_p/stp085p-tls.htm

I believe I would need a device like this to condition the power source:

http://shop.ata.org.au/cart.php?target=product&product_id=16327&category_id=251

Should I be concerned about exceeding the fan amp rating or am I being too
optimistic?

[snippety snip]
Assuming a similar figure, you would be looking at 500 times
$8.5 (or $7.5) or about $4,250.00 (or $3,750.00) to run your
motor. You don't need the synchronization if the motor is
the only thing hooked to it. So it will be cheaper. But I
would expect more than $2,000.00. But this may be made much
better depending upon your tax situation, current fed and
state tax incentives, etc.

Maybe someone better informed can add their thoughts or
correct mine.

No corrections; your numbers are reasonable. Just impressed that you
cranked this out at midnight on a Saturday. ;-)

--
Rich Webb Norfolk, VA

 

[Jon Kirwan]

On Sun, 19 Jun 2011 12:44:36 +0100, Nobody
<nobody@nowhere.com> wrote:

On Sun, 19 Jun 2011 00:09:31 -0700, Jon Kirwan wrote:

Also, solar panels are usually DC and have a rated output
voltage and current at some expected solar irradiance and
incidence to the panel. If they are rated 85 watts, it may
be that this is only in optimal conditions at the equator,
with no clouds or dust, and assuming 1000W/m^2 of sun. In
Texas, maybe 30N of the equator, you can expect somewhat less
as the cosine(30) is about 87%. And that's at high noon.

That's assuming that the panel is horizontal.

Yes.

If it's oriented directly
toward the sun, cos(a) is 1 regardless of latitude and time of day.

Or put another way, it's not relevant when oriented squarely
and ignoring rayleigh, aerosols, and the rest.

These still affect atmospheric absorption, but that's less significant
than cos(a) (k^(-sec(a)) as a first approximation).

Atmosphere does have a significant impact that can be quite
close to cos(z). I tend to use cos(z) now as a reasonably
good approximation for surfaces normal to the sun even though
the reason isn't the obvious one.

I remember some fairly nasty looking models (more than a few,
actually) that include CO2, O2, O3, H2O, rayleigh scattering,
total molecular, and aerosols. Total transmittance at 84N in
one such model is 10%. Although for different reasoning,
it's not far from cos(z). At my latitude it is about 73% or
so. I'm at 45N. Again, not far from cos(z). It surprised
me when I saw the models' plots. But then I just figured
that this only means I can use cos(z) as an okay
approximation _for all the wrong reasons._

What's a person to do if reyleigh and molecular and aerosol
scattering get you to about the same place? And when I go to
my local power company to look at their polar charts for
solar panels installed in my area, it turns out that the
numbers experienced in practice here are close to this kind
of rough-shod guessing of peak output. One home I went over
to, about 6 months ago, to look at their recorded performance
(they used a computer to log the data for the year prior)
came out about as I'd expect applying nothing more complex,
as well.

Jon

 

[John M]

Thanks for all the interesting and educational (and quick) responses.

After the "DOH" moment of opening the box and correcting from "12V" to
"120V", and particularly after reading everyone's input, I seem to have no
other choice but to (A) wire it to the house supply or (B) buy a properly
rated motor. It's for an attic fan, and the 12V motors don't seem to move
enough air to make it worthwhile, which leaves me with wiring it to the
house DC.


"John M" <jmcculloch@academicplanet.com> wrote in message
news:itjudp$1rd6$1@adenine.netfront.net...

I'm a newbie with electronics, but I am looking at powering a 12V 4A fan
with an 85W solar panel like this one:

http://www.ul-solar.com/product_p/stp085p-tls.htm

I believe I would need a device like this to condition the power source:

http://shop.ata.org.au/cart.php?target=product&product_id=16327&category_id=251

Should I be concerned about exceeding the fan amp rating or am I being too
optimistic?

Thanks,
John M
Houston, TX


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news@netfront.net ---

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[Tom Biasi]

"John M" wrote in message news:itl6nt$30ri$1@adenine.netfront.net...

Thanks for all the interesting and educational (and quick) responses.

After the "DOH" moment of opening the box and correcting from "12V" to
"120V", and particularly after reading everyone's input, I seem to have no
other choice but to (A) wire it to the house supply or (B) buy a properly
rated motor. It's for an attic fan, and the 12V motors don't seem to move
enough air to make it worthwhile, which leaves me with wiring it to the
house DC.

I don't know what you pay per KW-Hour but for me it would take ten years to
break even on equipment cost vs. using the utility power.
Use thermostat control and the duty cycle will most likely be less than 100.
Lesson: Solar panels are not very efficient, when you can use utility power,
use it. They make power cheaper than you can.

Tom

 

[John M]

"Rich Webb" <bbew.ar@mapson.nozirev.ten> wrote in message
news:r5orv6hi9vicfo0a3svdqu6gpoahknidsm@4ax.com...

On Sun, 19 Jun 2011 00:09:31 -0700, Jon Kirwan
jonk@infinitefactors.org> wrote:

On Sat, 18 Jun 2011 23:37:19 -0500, "John M"
jmcculloch@academicplanet.com> wrote:

I'm a newbie with electronics, but I am looking at powering a 12V 4A fan
with an 85W solar panel like this one:

http://www.ul-solar.com/product_p/stp085p-tls.htm

I believe I would need a device like this to condition the power source:

http://shop.ata.org.au/cart.php?target=product&product_id=16327&category_id=251

Should I be concerned about exceeding the fan amp rating or am I being
too
optimistic?

[snippety snip]
Assuming a similar figure, you would be looking at 500 times
$8.5 (or $7.5) or about $4,250.00 (or $3,750.00) to run your
motor. You don't need the synchronization if the motor is
the only thing hooked to it. So it will be cheaper. But I
would expect more than $2,000.00. But this may be made much
better depending upon your tax situation, current fed and
state tax incentives, etc.

Maybe someone better informed can add their thoughts or
correct mine.

No corrections; your numbers are reasonable. Just impressed that you
cranked this out at midnight on a Saturday. ;-)

--
Rich Webb Norfolk, VA

Ditto that, it looks like I have alot more homework to do.

Thanks for your taking the time Jon to present these facts and analysis
which certainly put some perspective on the Green Energy Hype.

First Solar Inc. claims to have reduced their manufacturing costs to less
than $1 per watt, but I don't know how close we are to having comparable
products available for average consumers. I expect some nano-engineered
material will eventually be developed that makes it worthwhile to harvest
the abundant sunlight.

John M Houston, TX



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[Jon Kirwan]

On Sun, 19 Jun 2011 16:34:14 -0500, "John M"
<jmcculloch@academicplanet.com> wrote:

"Rich Webb" <bbew.ar@mapson.nozirev.ten> wrote in message
news:r5orv6hi9vicfo0a3svdqu6gpoahknidsm@4ax.com...
On Sun, 19 Jun 2011 00:09:31 -0700, Jon Kirwan
jonk@infinitefactors.org> wrote:

On Sat, 18 Jun 2011 23:37:19 -0500, "John M"
jmcculloch@academicplanet.com> wrote:

I'm a newbie with electronics, but I am looking at powering a 12V 4A fan
with an 85W solar panel like this one:

http://www.ul-solar.com/product_p/stp085p-tls.htm

I believe I would need a device like this to condition the power source:

http://shop.ata.org.au/cart.php?target=product&product_id=16327&category_id=251

Should I be concerned about exceeding the fan amp rating or am I being
too
optimistic?

[snippety snip]
Assuming a similar figure, you would be looking at 500 times
$8.5 (or $7.5) or about $4,250.00 (or $3,750.00) to run your
motor. You don't need the synchronization if the motor is
the only thing hooked to it. So it will be cheaper. But I
would expect more than $2,000.00. But this may be made much
better depending upon your tax situation, current fed and
state tax incentives, etc.

Maybe someone better informed can add their thoughts or
correct mine.

No corrections; your numbers are reasonable. Just impressed that you
cranked this out at midnight on a Saturday. ;-)

--
Rich Webb Norfolk, VA

Ditto that, it looks like I have alot more homework to do.

Thanks for your taking the time Jon to present these facts and analysis
which certainly put some perspective on the Green Energy Hype.

All distributed (small, self-contained) power systems are
expensive simply because they cannot take advantage of
economies of scale, if for no other reason.

Solar PV is expensive beyond that basic fact, too, right now.
Even done on a large scale or with concentrating systems that
track the sun, it appears to still be so expensive that no
one does it without some kind of incentive designed to change
the economic calculations. Even in places with the best
lighting, year around, it's still not otherwise done (unless
there are other considerations that factor in.)

The tax incentives are substantial. So it can be worth some
consideration.

First Solar Inc. claims to have reduced their manufacturing costs to less
than $1 per watt, but I don't know how close we are to having comparable
products available for average consumers.

Here in Oregon at 45N, on this side of the Cascades, we get
about 1000 kW-hr/year per "1000 watt module." Using roof top
installations. At $1/watt, that module would cost $1000 and
generate 1000 kW-hr in a year. At a standard $0.10/kW-hr for
electricity, this would produce an "income" (reduction of
costs) of $100 per year for an up-front investment of $1000.
Ignoring interest rates, maintenance, loss of use, and aging
effects, this pays off in about 10 years. (Still longer, in
reality.)

Eastern Oregon's figure is 1250 kW-hr/yr. I'm not sure what
the figures are for Texas, but probably somewhat better than
that.

And as you point out, when we even get to that point for
average consumers is still another question entirely. Those
tax incentives are what makes it happen at all for
individuals, if at all.

By the way, many power companies (certainly the one here) try
to buy those watts as "green energy watts" so they can sell
them, themselves. In choosing to sell them that way, you are
no longer generating carbon-free energy (assuming you ever
imagined that carbon dioxide wasn't produced in making and
installing the systems in the first place) because those
green credits get sold to folks who intend on generating lots
of atmospheric carbon. You have to refuse to accept the
benefit, if you want to imagine any "green-ness" to your
installation. Even then, you remain in doubt as getting a
fully burdened accounting that everyone agrees with seems as
hard as finding a chicken with teeth.

I expect some nano-engineered
material will eventually be developed that makes it worthwhile to harvest
the abundant sunlight.

Green plants achieve very high efficiency, I have read.
Obviously, it is worthwhile to them! We've a planet covered
with their successful use. Of course, it's for their own use
and doesn't directly make electricity.

(Hmm. Some physicist+microbiologist might come up with a
modified chloroplast that moves electrons across some
potential barrier, but then you'd still need to let it use
_some_ of the energy in self-maintenance and perhaps
replication.)

Solar cell technology is working towards better efficiency.
I've no idea when all this gets into the mainstream and out
of some lab, though. It's been a dream for so long, I am not
sure when to expect to wake up from it or who to believe that
is trying to wake me up.

Jon

 

On Jun 19, 9:05 am, "John M" <jmccull...@academicplanet.com> wrote:

Thanks for all the interesting and educational (and quick)
responses.

After the "DOH" moment of opening the box and correcting from "12V"
to
"120V", and particularly after reading everyone's input, I seem to
have no
other choice but to (A) wire it to the house supply or (B) buy a
properly
rated motor.  It's for an attic fan, and the 12V motors don't seem
to move
enough air to make it worthwhile, which leaves me with wiring it to
the
house DC.

"John M" <jmccull...@academicplanet.com> wrote in message

news:itjudp$1rd6$1@adenine.netfront.net...
snip

This is one example of many

http://solaratticfans.com/

We have two of these (or ones like it) in our attic. Roof is black
composition and the attic isn't much warmer than outside. The fans are
virtually silent and do a good job.

G˛

 

On Sat, 18 Jun 2011 23:37:19 -0500, "John M"
<jmcculloch@academicplanet.com> wrote:

I'm a newbie with electronics, but I am looking at powering a 12V 4A fan
with an 85W solar panel like this one:

http://www.ul-solar.com/product_p/stp085p-tls.htm

I believe I would need a device like this to condition the power source:

http://shop.ata.org.au/cart.php?target=product&product_id=16327&category_id=251

Should I be concerned about exceeding the fan amp rating or am I being too
optimistic?

Thanks,
John M
Houston, TX
Don't make it harder than it has to be.

Your fan wants 12V, your solar panel puts out 21 OPEN CIRCUIT. No
solar panel does any useful work Open Circuit that's just how they
specify it. At any load expect much less than 21 volts like maybe 15
if the fan alone is the load.

Can a 12 volt fan withstand more than 12 V? Hell yes. Even a brush
type motor will survive 2-4 over voltage at load without dying.

try it and see.

And solar panels - cells in series are limited to the output of the
cell(s) in the shade. They almost never deliver peak output (since
only people living on the equator would ever know)

 

[Bernhard Kuemel]

On 06/19/2011 01:52 PM, Nobody wrote:

On Sat, 18 Jun 2011 23:47:19 -0500, John M wrote:

I'm a newbie with electronics, but I am looking at powering a 12V 4A fan
with an 85W solar panel like this one:

Oopsies, that should say "120V 60Hz 4A fan motor"

Slight difference

12V*4A = 48W, which is feasible given enough sunlight.
120V*4A = 480W, which isn't feasible under any circumstances.

He could charge a battery (or super capacitor) and drive the fan with a
10% duty cycle. It's typical usage of PV.