Useful Power from A Single Solar Cell

 

"Electronic Design" magazine publishes some gems sometimes. Here is a
boost circuit that will start up at about .25 volt and supply 8-10V
(open circuit) from a single solar cell. It cost about 5 bucks to
build.

It's also useful for sucking about every last ounce of energy from a
standard battery. Most multivibrators quit at ~.8V and this one just
keeps on goin' down to about .25-.27V.

http://electronicdesign.com/Articles/ArticleID/15420/15420.html

I built the circuit and tested it. I didn't have the exact inductors
in stock here, so I used some 44uh units. Some observations:

It seems to charge two nicads in series, although slowly. Don't exceed
2.0V input, this destroys the transistors. For a light load circuit
this thing is neat. The solar cell I had is about .6V @50mA.

After I'm done fiddling with it, I'll find out when it complains,
current-wise, short it under power and otherwise stress it and see
what happens. I only have 4 of the germanium tranisistors here so I
have to make them count.

 

One of those boosters and a Honeywell Thermopile that is used to keep
pilot light valves open would charge your cellphone if you put the
thermopile in the campfire.

 



A whole lot better is the common Peltier pile, operated as a Seebeck device.  A
typical pile such as used in thermoelectric coolers will generate about 12 volts
at a
couple amps when subjected to the same temperature differential as it would be
generating if powered.

I built a 12 volt, approx 5 amp battery charger using several piles clustered
around
a hunk of aluminum heated with a propane torch.  The other side of each pile was
connected to a LARGE heat sink.

It worked great in cooler weather, lesser great in warm.  The major limitation
is the
indium solder used to build the pile.  It has a low melting point and thus
limits the
hot side temperature to a couple hundred degrees.

If one had a cold heat sink, say a spring or deep lake, to cool the cold side, I
wonder how a Peltier pile would compare in efficiency to a run-of-the-mill solar
cell?  Guess I need to do the math sometime.

One of my round tuit projects is to equip my generator with some piles to see if
I
can use waste heat to generate some more electricity in enough quantity to make
it
worthwhile.  One of the tuits I need is a source of cheap piles.

John
---
John De Armond
See my website for my current email address
http://www.neon-john.com
Cleveland, Occupied TN
Nuke the Whales!

 




if I

The conversion efficiency of peltier modules is next to hopeless.

But in the homepower world there is no such thing as waste heat.
Either dump it into a hot water tank or, if you have too much hot
water, drive an absorption refrigerator.   Running generators, even on
waste oil and not grabbing the last bit of energy from them isn't IMHO
very green.



--

 



if I

make it

Probably right in there with PVs.  Some back-of-the-napkin figuring. My charger
made
about 5 amps at 13.8 volts or 69 watts.  A propane torch makes about 2,000
BTU/hr or
about 585 watts.  69/585 = about 12%.  Hmmm, never done the numbers before.  It
actually IS pretty close to PVs.


I don't give a flying fsk about that ritualized pagan gaia worship called
"green".
I'm pretty much the polar opposite - I would say I'm red but that color already
has
its own political baggage.  All I care about is convenience and cost.  If I'm
camping
in my RV and I can snatch a little more power from the generator's waste heat
doing a
nifty experiment then I'll go for it.

John
---
John De Armond
See my website for my current email address
http://www.neon-john.com
Cleveland, Occupied TN
Okay, okay, I'll take it back ... UNfuck you!