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'[OT]Solar Panels?'
1999\03\05@154409 by PJH

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face
Hi,
Can anyone point me to a website
where I can bone up on the ins &
outs of solar panels?

I have to operate a PIC-controlled
remote camera system and the
Pb-acid batteries get sucked dry
pretty quick. It operates at night
so trickle\periodic charge by day
looks good. I've never fiddled with
solar cells before but I'd guess
the main gotcha would be if the
batteries discharged thru the solar
panel - and fried it.

The panel I'll use is fairly
expensive so I'm just looking for
a  page with some practical tips on
hooking up solar panels, what not
to do, how to screw up big-time etc
etc.

Regards & thnax - PJH.

1999\03\05@164005 by Mark Willis

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PJH wrote:
>
> Hi,
> Can anyone point me to a website
> where I can bone up on the ins &
> outs of solar panels?
> <snipped>
> looks good. I've never fiddled with
> solar cells before but I'd guess
> the main gotcha would be if the
> batteries discharged thru the solar
> panel - and fried it.
> <snipped>
>
> Regards & thnax - PJH.

 I know you want a diode in series with the stack of solar cells (It's
not uncommon for that diode to already be in the manufactured solar
array.)  I'm interested in learning more here, want a PC110 array <G>

 Also if you put multiple arrays in parallel you do want a diode in
series with each array (so if one array's shaded, it doesn't
back-charge) etc.  I suggest Schottky's rated at the highest peak
current the array could possibly generate <G>

 Lessee, some places I pointed my brother at were:

 Photon Tech's Links Page
 http://members.aol.com/photontek/photon/weblist0.html

 Personal Solar
 http://www.yessolar.com/

 All I have time to snag just now <G>

 Mark

1999\03\05@170742 by Wagner Lipnharski

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PJH wrote:
{Quote hidden}

We are testing a small solar cell from PowerLine Solar
Products, 32 S.Ewing Ste #331, Helena MT, 59601, they
have a website(???) the small cell we have is only 2" by
2¹" and it recharges a NiCad pack 4xAA in bright sun
with 5.4V @ 23mA... wow, yes, it is nice. They deserve
this free adv. There is this list of companies:
http://www.cleanenergy.de/name_s.html
--------------------------------------------------------
Wagner Lipnharski - UST Research Inc. - Orlando, Florida
Forum and microcontroller web site:   http:/http://www.ustr.net
Microcontrollers Survey:  http://www.ustr.net/tellme.htm

1999\03\05@193011 by Nick Taylor

picon face
PwerLine Solar Products was bought by Advanced Power
Technologies a few weeks ago.  Their new URL is:
  http://powerexperts.com/solar.htm
Enjoy,
- - - Nick - - -

Wagner Lipnharski wrote:
<snip>
> We are testing a small solar cell from PowerLine Solar
> Products, 32 S.Ewing Ste #331, Helena MT, 59601, they
> have a website(???) the small cell we have is only 2" by
> 2¹" and it recharges a NiCad pack 4xAA in bright sun
> with 5.4V @ 23mA

1999\03\05@204145 by PJH
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Mark Willis wrote:

> PJH wrote: Hi, Can anyone point me to a website where I can bone up on
> the ins & outs of solar panels?
>
>     All I have time to snag just now <G>

You mean, shed some light on? <G>pjh

1999\03\05@204400 by WIL REEDER

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Hi PJH
I spend about half my time living in a solar powered house (wind too). The
general rules are electrically: a Shottkey diode in the line to the battery
and you will likely need three times the solar panel in the winter than
summer, so, some form of regulation may be required. Mechanically: Face the
cells south (true not magnetic --try the shadow at noon trick) or if the
sun is obstructed face it at the center of the open area. Set the cells at
an angle equal to your latitude.
A simple regulation method could be a 6.3v zener at the panels, rated to
handle the full output, then on to the blocking diode and battery (4.8 v
nicad)
Hope this is some help, You get extra points for going with renewable
energy!!!


Wil Reeder
spam_OUTteachtechTakeThisOuTspambc.sympatico.ca
Vancouver,Canada 0x34
solar,wind,tide, TEG  renewable energy

----------
| From: PJH <.....elekKILLspamspam@spam@NETSTRA.COM.AU>
| To: PICLISTspamKILLspamMITVMA.MIT.EDU
| Subject: [OT]Solar Panels?
| Date: Friday, March 05, 1999 12:40 PM
|
| Hi,
| Can anyone point me to a website
| where I can bone up on the ins &
| outs of solar panels?
|
| I have to operate a PIC-controlled
| remote camera system and the
| Pb-acid batteries get sucked dry
| pretty quick. It operates at night
| so trickle\periodic charge by day
| looks good. I've never fiddled with
| solar cells before but I'd guess
| the main gotcha would be if the
| batteries discharged thru the solar
| panel - and fried it.
|
| The panel I'll use is fairly
| expensive so I'm just looking for
| a  page with some practical tips on
| hooking up solar panels, what not
| to do, how to screw up big-time etc
| etc.
|
| Regards & thnax - PJH.

1999\03\05@205022 by Lynx {Glenn Jones}

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> summer, so, some form of regulation may be required. Mechanically: Face the
> cells south (true not magnetic --try the shadow at noon trick) or if the


Unless, of course you live in the souther hemisphere :)

1999\03\06@002546 by Mark Willis

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PJH wrote:
>
> Mark Willis wrote:
>
> > PJH wrote: Hi, Can anyone point me to a website where I can bone up on
> > the ins & outs of solar panels?
> >
> >     All I have time to snag just now <G>
>
> You mean, shed some light on? <G>pjh

 Boo, Hiss.  <G>  I thought I was the official harasser of the PICList,
now?

 Mark

1999\03\06@003211 by Mark Willis

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Lynx {Glenn Jones} wrote:
>
> > summer, so, some form of regulation may be required. Mechanically: Face the
> > cells south (true not magnetic --try the shadow at noon trick) or if the
>
> Unless, of course you live in the souther hemisphere :)

 Not at all;  You just need to set them at a NEGATIVE angle <G>

 (I remember one application one person was complaining about showing
the world map "upside down" - turns out the developer chose to "flip"
the world view when you chose a home city in the southern hemisphere, so
South was "up" - freaked this user out <G> - I suggested he pick a "home
base" city in the same Time Zone, but north of the equator.  I've seen
THAT one more than once, sorta a neat trick, easy enough to do from a
coding point of view, too!)

 Mark

1999\03\06@023324 by Wagner Lipnharski

picon face
Mark Willis wrote:
> Not at all;  You just need to set them at a NEGATIVE angle <G>
>(I remember one application one person was complaining about showing
> the world map "upside down" - turns out the developer chose to "flip"
> the world view when you chose a home city in the southern hemisphere, so
> South was "up" - freaked this user out <G> - I suggested he pick a "home
> base" city in the same Time Zone, but north of the equator.  I've seen
> THAT one more than once, sorta a neat trick, easy enough to do from a
> coding point of view, too!)
>
>   Mark

whaaat? :)
--------------------------------------------------------
Wagner Lipnharski - UST Research Inc. - Orlando, Florida
Forum and microcontroller web site:   http:/http://www.ustr.net
Microcontrollers Survey:  http://www.ustr.net/tellme.htm

1999\03\06@144142 by Wagner Lipnharski

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Mark Willis wrote:
<snip>
>   Us northern hemisphere denizens don't control the southern hemisphere,
> ya know, they got all these different ideas of which way "Right side up"
> is, when Summer and Winter are, and even have managed to change which
> way water swirls as it goes down the drain, for all locations south of
> the equator.  Pretty powerful, huh?
>   I figure it's a massive SouthHemispherian conspiracy, but cannot offer
> any proof, as the cat ate it <G>  (He's easy to bribe, dangit!  And he
> gets bored...)  They're out there, I just know it <VBG>  (The cats, or
> the southern hemispherians?  Yes.)
>
>   Mark (Should I yell at myself for being off topic, yet?)

Well, I was born in Brazil, southest state, almost the end of South
America,
right above Uruguay country, we use to see the world map south-down,
north-up,
the water swirls contrary to the north hemisphere, and also the radio
waves,
yes, helicoidal antennas are build contrary to the ones used in north
side of
the globe.

There are few scientists down there trying to convince us that the globe
map
must be plotted from inside out, since it is easy to see the
coordinates.
Imagine yourself in the physical middle of the planet ball, so it would
be
easy to pinpoint any place in the globe using lat/long/alt. In real this
is
not a bad idea, since it is easy to create the concept of real distance
between points.  If you first connect the origin and destination by a
straight
internal line, then stretch it to the surface via an arch, you get it.

Lots of people really think that it is easy to go from New York to Japan
in
a straight horizontal line to the west, via San Francisco for example,
when
going straight via Alaska is shorter.  But it is very easy to see that
if
you imagine yourself inside the globe.

So, going back to the subject, anybody out there already developed any
PIC interface to a GPS unit powered by a Solar Panel?
--------------------------------------------------------
Wagner Lipnharski - UST Research Inc. - Orlando, Florida
Forum and microcontroller web site:   http:/http://www.ustr.net
Microcontrollers Survey:  http://www.ustr.net/tellme.htm

1999\03\06@164556 by Gerhard Fiedler

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At 14:39 03/06/99 -0500, Wagner Lipnharski wrote:
>There are few scientists down there trying to convince us that the globe
>map
>must be plotted from inside out, since it is easy to see the
>coordinates.

i guess the question is not whether to plot it inside out or from the
outside, it is how to project a sphere's surface on a flat surface. since
this can't be done without =some= distortion, the question is =what= to
distort... in doubt, use a globe. usually from the outside :)

ge

1999\03\07@140723 by goflo

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Per battery current measurement, hall-effect current sensors
are in use on some late-model autos.
Likewise interested in an elaboration of "power trackers".

Regards, Jack

Mike Keitz wrote:
{Quote hidden}

1999\03\07@151848 by Wagner Lipnharski

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Mike Keitz wrote:
{Quote hidden}

As far as I understand Ohm's law, the maximum current will be
proportional to the maximum voltage, so... if the batteries
are at 96V, any voltage above that will work. The output power
is a fixed relation to the input power less the losses in the
conversion, so, if the cells generate 0.45Vx110A (50Watts),
take off the conversion losses, let say 15% in the best deal,
the power output will be 42.5W.  It will take a cell size of
aprox 1660 square inches, or a board of 41x41 inches.

It doesn't matter much what the voltage is being generated at
the bust conversion, it needs at least to be higher than the
batteries voltage. The batteries internal impedance would be
so low that this is what will rules about the battery charge
current. Also the solar cells high impedance will drop its
output voltage with the increase of the drained current.

So, imagine the batteries are at 85V, your buster step-up is
trying to generate something around 100V, but its output
impedance is higher than the batteries impedance, so the
current output will be a factor of the power transferred
divided by the battery voltage. 42.5(W)/85(V) = 0.5 A.

I never saw a step-up conversion with a productivity better
than 85-87%... even the small ones produced by Maxim or Linear
Tech, and charge capacitive pumps are not better, so I think
that losing 15% in solar power is a high price.

Solar cells are very easy to cut, plastic, flexible or the
liquid ones right now, so build an array with 300 cells
in series is not a big problem... well, I don't know the
problems you may have to do that, but it would give you at
least 15% more power... aprox 588mA, not talking about the
most economic wiring AWG as well the cost of the buster,
or then 15% less cell overall sizes, what correspond to
a reduction of almost 16x16 inches in the cell area.
--------------------------------------------------------
Wagner Lipnharski - UST Research Inc. - Orlando, Florida
Forum and microcontroller web site:   http:/http://www.ustr.net
Microcontrollers Survey:  http://www.ustr.net/tellme.htm

1999\03\07@153335 by Dave VanHorn

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>I never saw a step-up conversion with a productivity better
>than 85-87%... even the small ones produced by Maxim or Linear
>Tech, and charge capacitive pumps are not better, so I think
>that losing 15% in solar power is a high price.


Charge pumps (capacitors) are the WORST in efficiency. Think about
I^2R losses, and what happens when you connect a discharged cap to a
supply...

Boost converters can get into the high 90s especially if the working
voltages are respectable.

Were I charging lead acid batteries from a solar array, I would set
the array for the highest voltage that is less than the battery
discharged voltage, then use a current mode boost circuit set to a
limit current at some reasonable rate WRT the battery size, maybe C/5
or some such, and set the voltage to about 2.3 or 2.4 V/Cell.   CS384X
series make great controllers for this sort of thing.

1999\03\07@160108 by Harold Hallikainen

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On Sun, 7 Mar 1999 20:30:12 +1100 PJH <elekspamspam_OUTNETSTRA.COM.AU> writes:
>Hey, that doesn't sound like a bad idea. Not bad at all. There's a a
>chip from
>Motorola, the MC34063,  sometimes goes by the id uA78S40. It's a
>"Switching
>Regulator Controller" for DC:DC step up\step down supplies that'd be
>ideal in the
>application.You can boost it's o/p current easily and use a pic to
>oversee the whole
>thing, switching between batteries, turning off the system for a
>periodic charge up
>etc.(Just thinking of my remote camera app, not the sun-car.)
>PJH

       I've used the 78S40 before, but I don't see why to use it here.  Why not
just have the PIC generate the appropriate PWM and drive the FET directly
(or through a driver if we need a higher gate voltage)?  As I've stated
before, the ideal design has zero parts!

Harold
>

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1999\03\07@160114 by Harold Hallikainen

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On Sun, 7 Mar 1999 12:32:36 -0500 Mike Keitz <@spam@mkeitzKILLspamspamJUNO.COM> writes:
>
>Exactly how does it work? Do you just adjust the PWM slightly and see
>if  the battery current increases or decreases, or is measurement of the

>solar panel voltage involved too?  Can you just regulate the panel
>voltage to some level and get maximum power out, or does the optimum
>panel voltage vary widely under different light levels?  Measuring the
>battery current seems like the best way since that's really what
>you're after, but it may be hard to do without losing some power in a
>resistor.
>I've heard of these power trackers, but never a description of
>exactly
>what method they use to operate at the maximum power point.
>

       You've got it!  The idea is just to adjust the PWM and see if the
battery current goes up or down.  the solar panel voltage does not play a
part in it.  We could measure the panel voltage and current, then adjust
PWM for the maximum of the product, but measuring the output current
seems much simpler.
       I see the Thevenin equivalent of a solar panel as a variable voltage
source and a variable source resistance, both of which vary with the
amount of light falling on the panel.  The converter adjusts its load on
the panel to match the source resistance, giving us the most output
power.  Instead of looking at source resistance, load resistance, or
whatever, we just adjust for what we want:  maximum output power.  Since
the output power always increases with increasing current into the
batteries, it's pretty simple to measure.  Of course measuring the solar
panel current, we'd find a maximum current when we got zero output power
(driving a short), or maximum voltage when we got zero output power
(driving an open).
       Sensing the output current efficiently might be a bit of a problem.  We
don't really need to know the absolute current, just whether it's going
up or down.  So, we could measure the voltage across something where we
are already getting a voltage drop, such as the output diode in the step
up converter.  Another idea might be use of a Hall effect sensor, or
maybe a SenseFET.  So far I've just told the students "Here are some
ideas to play with."  I haven't had to get any of it to work!
       They did bring me a circuit someone had developed with LOTS OF PARTS!
It sampled the input voltage and current, multiplied the two (in analog
circuitry) and adjusted a standard switching regulator chip.


Harold
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