Capacitor Used as Energy Storage Device for Off Grid Power?

Of course they can be used.

It would cost more than the litium batteries, & take up a huge amount of space.

Yes, but that technology is not yet mature.

The technology is called super capacitors, and work on improving their energy storage density per unit volume is ongoing.

https://www.youtube.com/watch?v=z3x_kYq3mHM

The line between capacitors and batteries has definitely been blurred by super-capacitors. Their construction and chemistry starts to look very battery-like, even more so than electrolytics.

Have you ever used a nickel iron battery? Did you engineer the system. Did you buy it from Iron Edison?

I have built some very large systems, using Unigy AGM 40KWH units. Did you establish and require a service contract for required electrolyte maintenance, or did you purchase an automatic watering system?

No, I have not done any of those things. I have installed other equipment at sites that used nickel iron batteries. Will you please enlighten us.

Then why would you recommend nickle iron batteries? Just curious. They are very much a niche product.

Yes, they are a niche product. As I said I've seen them used before at a communication hub site. Everything that I've read here and elsewhere on the web tells me that nickle iron batteries for off the grid power storage is one such task in this niche.

Again, please enlighten us with your experience.

NiFe technology is really interesting. They are not suitable for most residential and small commercial applications. IMHO. They are initially expensive, have low power density, (require about 40% more volume than AGM or flooded LA batteries), consequently weigh much more, require at least as much watering as flooded lead. They have peak load limitations, although they excel at consistent low load applications (like a communications hub) They can be ramped up, but as load variability increases, the relative expense of providing that increased potential is problematic.

If you are building a giant megawatt scale load shifting storage plant, maybe they make sense. No one has done it with anything close to an economic justification, they are just talking about it. Pumped water is still much cheaper, but of course also has the same issue of restricted peak load production. And who wants a big lake of water just standing around with fish and stuff in it.

Check out Aquion. I don't work for them. We are using them in a 125KWH bank, which might be classified as medium/large scale residential project right now. Very similar to NiFe, but with less maintenance, and very intelligent connectivity. The project requires an unusually low peak demand, that lasts for unusually short periods. Most residential off grid or grid tied backup systems are designed to have as small a bank as possible to (1) meet design loads during periods derived from autonomy requirements, and (2) to meet peak output requirements based on estimates of variable loads. and (3) to reduce expense, (4) to reduce space requirements. It is all about the upfront money for many apps, then maintenance costs, then lifecycle costs.

I welcome input from anyone, especially those who see flaws in my assumptions, which unfortunately, seem to happen regularly if I am trying to understand new things. Thanks for that, Fred.

Wait up on the new Aluminium Battery technology that is being developed right now. Long life (in comparison to lithium for example) and fast charging....though it won't be next week!!

A year or two I expect.....

The aluminum battery recently presented in the press does charge quickly but what they don't highlight is that the battery does not have high current discharge capability. They're working on improving the discharge characteristic. The capacity vs. discharge (A-hr vs. A) metric is about 1/10 of a Li-Ion cell.

It's somewhat strange that you charge this battery very quickly but you can't discharge it quickly. Most batteries have similar (symmetrical) charge-discharge characteristics.

That Al battery development is the most promising one of late. A year or 2 more probably is right.

...but capacitors..... already covered by our other esteemed posters.

Use capacitor only if you are a certifiable Aggie! Otherwise save your life by not using a capacitor (which you would obviously short out if not a certifiable Aggie). On second thought, I think I have my wires crossed.

Why not just use a doggone Edison battery, or the newest latest, greatest aluminum-graphite cells that are way better, and much safer than Lithion ion?