energy storage for PV systems

Hi guys,

I'm researching battery storage methods for a photovoltaic system.
Which would be cheaper per stored kW-hr: lead acid batteries or NiMH
batteries? (Assume for the sake of argument that temperature effects
can be neglected; i.e. NiMH batts won't work because of high summer
temperatures...)

Just want to see if my calcs concur with yours.

Thanks,

Mike

Mike Darrett wrote:

For my money, NiZn marine/RV batteries are the best value.

[Only registered users see links. ]

-dl

Uncle Al wrote:

That's doing something naughty to physics --
failing to distinguish it from a hole in the ground.
Energy in a solenoid means magnetic field,
that means tension, that means breakage at very low
energy per unit mass and volume.


--- Graham Cowan
[Only registered users see links. ] --
how cars gain nuclear cachet

Dear G. R. L. Cowan:

"G. R. L. Cowan" <[Only registered users see links. ]> wrote in message
news:[Only registered users see links. ]...
....

But it will only break once! ;>}

David A. Smith

Uncle Al wrote:


I was tremendously disappointed when the Cohen brothers, he of
Compaq Computer, gave up on the flywheel powered car. The press
never seemed to give a good reason, but two possibilities occur.
Maybe they could never come up with good enough bearings -- like you
can't make an air bearing in a vacuum chamber, so you gotta come up
with Teflon's teflon, or else some magnetic miracle which can put up
with all this spinning metal, plus precession as you drive the car
around corners, on a planet that revolves, yet.

Then again, maybe the insurance companies put it to them that this
little spinning rotor had more energy in it than a tank of gas by a
factor of five or ten, but when the rotor shreds it doesn't do a
nice slow chemical explosion like hydrocarbons, it all goes blooey
at once.


Al, tell me, I dunno: how do you get power out of a capacitor
slooo-owly? And was is a solenoid as a storage device? That's a new
one on me.

Cheers,

-dlj.

[Only registered users see links. ] wrote in message news:<qLtPa.39$[Only registered users see links. ]>...


Yup. I was surprised, though, to discover that one of my Energizer
2200 mAh, 1.2V "D"-cell NiMH batteries has about 2.5x the storage
capacity of a 10-atmosphere compressed H2 cylinder of the same
dimensions. And NiMH batteries of even higher power densities
exist...



Too true...


Mike

Uncle Al <[Only registered users see links. ].net> wrote in message news:<[Only registered users see links. ].net>...


Is there a way to draw off the energy slowly, over say a 24-hour
period? Or must one release the energy in a spectacular blast?

Very nice security feature though. Any thief would be reduced to a
pile of ashes - maybe even the bones would be vaporized. Would
probably never even know a thief was there. Sure beats hungry guard
dogs, fed every other day or so...

Mike

[Only registered users see links. ] wrote:


<sigh right back>

Mati,

You're trying to operate on one-context-fits-all. Of course a
flywheel is only a storage device, like a battery, from the point of
view of the Whole Shebang.

From the point of view of the car, the battery or the flywheel or
the gasoline are the car's source of energy. period. Get used to it.
See if you can train yourself to think with the point of view
relevant to the problem you are working on, OK? You'll be a nicer
human being and a more effective worker once you accomplish this
small change in your opearting system.


You're not being offensive, Mati. You're just showing your own
inability to function properly. Applying "facts" in senseless
contexts is a major congnitive failure.


My guess, Mati is that you're probably an order or two of magnitude
low in your estimate of the tensile strengths of modern light-weight
materials. Many people make the error of thinking that a steel wheel
will come apart before you get it pumped up very far; indeed it
will. Modern composites are far far stronger, and much less dense,
and hence defy conventional engineering intuitions.


Quite right. As you demonstrate.

-dlj.

"Mike Darrett" <[Only registered users see links. ]> wrote in message
news:d945119c.0307110746.7c564388@posting.google.c om...
news:<qLtPa.39$[Only registered users see links. ]>...
<[Only registered users see links. ]> writes:
....

Way too much polemics is made of this modest difference. Fuel oil is also
not an energy source. It is just a storage medium for very very old solar
energy. That it was formed by natural causes does not change it's nature at
all, so I just can't find it in my heart to pretend that it's nature is
fundamentally different just because we didn't have to grow the organics to
make the oil. A good question of whether we can grow enough oil to provide
for our current high level of consumption.

In article <[Only registered users see links. ] >,
Mike Darrett <[Only registered users see links. ]> wrote:

De-energizing a superconducting magnet is typically done by switching a
big-ass diode into the circuit. The diode drops a few volts, which
dissipates energy by P=IV. A resistor would work, but can generate much
higher voltages since V=IR.

A method without heat dissipation might be to rapidly switch a capacitor
in and out of the circuit.
--
"Is that plutonium on your gums?"
"Shut up and kiss me!"
-- Marge and Homer Simpson