Capacitor uses

[Ron]

I've been researching capacitors and wonder if they could be used to store and release energy extending solar use after dark. Or with wind turbines to keep energy flowing if the wind quits for a few minutes. Surprisingly there is very little info out there besides using them for HVAC. A run type capacitor seems like it could help a lot. I don't see any drawbacks to their use.
I also wondered about putting an AC capacitor with a breaker box to help stabilize any incoming power rush. maybe someone here is much better educated on this subject.

 

[jgh]

I've been researching capacitors and wonder if they could be used to store and release energy extending solar use after dark.

The energy stored is nowhere near enough. We use chemistry for good reason.

 

[outsider]

Batteries store far, far more energy than capacitors do, even supercapacitors, per weight, and per volume, and per dollar.

 

[outsider]

There is a use for supercapacitors in a battery application where one needs extremely high surge currents for just a little while, in that a supercapacitor may be significantly smaller, lighter, cheaper, than a bunch of batteries able to supply that same surge load. But for plain old energy storage, it's tough to beat batteries.

 

[Hedges]

Capacitor - Wikipedia

en.wikipedia.org

The energy stored is:



Where E is in Joules (watt seconds)

Run the numbers for any capacitor you've got and you'll see how much it can store.

 

[bolhuijo]

Excellent, I've got a spare 50mF, 440V run capacitor for my AC system. It only cost $25. 1/2 * 50e-06 * 440^2 = 4.84 Joules. That works out to 0.00134 Watt hours. Compared to this pathetic little LR44 watch battery which is only 115mAh at 1.5V, or 0.17 Watt hours. Oh that's not a lot.

 

[efficientPV]

I use a 6,000uF capacitor bank and it can only store enough useful energy for about 0.4 milliseconds. Half a cycle at 60Hz is 8.3ms.

 

[outsider]

The best thing about working on RF circuits is that the capacitors only have to store energy for a few, or a few tens of, nanoseconds. 0.1 microfarads is a huuuuge capacitor at 100 MHz.

Needless to say the picture changes at DC.

 

[McKravitts]

For comparison sake the AH equivalent of a capacitor is given by AH = F*V/3600

F is farads not mF or uF.

Using the formula a 10 Farad capacitor ( a very large cap ) rated 12 volts and costing about $100.00 will store less than .03 AH.
The same $100.00 will buy you about 50 AH of 12 volts liFePo battery(s).

As metioned above there is no comparison as far as AH storage. The Batteries win hand down.

On the other hand a fully charged 10 F capacitor can deliver an instataneous power of 10,000 watts.

The average Li battery may deliver 100A * 12 volts = 1,200 watts.

A super cap in parallel with a LI battery bank gives you the best of both worlds.

You must pre-charge the Cap before adding it to the circuit and place the cap as close (wire length wise) as possible to the load.
A small inductive reactance between the battery bank and the Cap is helpful. This can be achieved with a long hook up wire