Alternative electricity storage.

[omgwtfbyobbq]

I was thinking, for solar/wind electricity, at different times of the year, they can sometimes output tons of energy, maybe more than the battery pack can handle, at least in terms of wind. And adding batteries is expensive, so how else can we store this energy? Most other forms used in large scale electricity generation seem way too complex for small scale, except for hydroelectric.

Lets take two water tanks (double as emergency water storage), one being roughly six feet above the other. By pumping water from the bottom tank to the top tank, we can take any excess energy and store it. Use will be via a switch that lets the water drain back into the other tank, which can spin a generator, to charge up the batts. If there's a ton of wind during the winter, as long as the tanks are big enough/there's enough distance between them, that should allow for plenty of energy storage.

Also, the size and cost of the battery pack can be minimized to something that can provide enough energy for half a day, versus a few days, since we'll effectively have two energy storage devices. Ideally, it'd be neato if there was some sort of throttling mechanism for the water flow, so that a battery system wouldn't be needed at all,but that seems way too complex.

So... Am I insane, or could this actually work? :D

[Ryland]

how much energy does it take to lift water 150 feet out of a well, in to your house? how much energy would be stored if you were to lift water another 150 feet in the air, you would have 150 of head, right? I could see this being a practical energy storage system if you had a 5000+ gallon tank in your attic, or in the upper storie of a building up a hill from your house, but lifting 100 gallons of water 6 feet might be enough energy to do what? light a light bulb (small compact floresent) for a few minutes, really if you want a good energy dump heat is the way to go, dump that heat in to a mass that will stay warm for months, 100's of tons of sand, or water, and draw off that heat all thru the winter, sure you are going to loose a bit of heat, but you wanted it to be cheap, right?

[DracoFelis]

The idea of pumping water uphill as a "power storage" idea isn't new. I heard about some country in Europe doing that (pumping water up a mountain to store electricity, and getting some fraction of that power back later by using a hydro generator), way back in the 1970's.

However, the storage "efficiency" of such a system is limited by the combination of the efficiency limits of the pumps (used to "store" the energy) and the efficiency limits of the hydro generators (used to get the power back). So this is far from the most "efficient" of "batteries".

Furthermore, the total "storage capacity" is limited by the amount of liquid you can pump, and the distance (upward) that you can pump it. And in your average home, you usually can't move the liquid up more than a few stories, nor would you want huge tanks. So besides not being the most efficient of batteries (see above), it would also be a rather big battery, if you were trying to keep this in your home.

So, it's an idea that has been done. And it would actually work. However, it's not a choice that is well suited to use in a home environment.

OTOH if you are "on grid" (i.e. you aren't someone with a home that's away from the normal utility power lines), than why not cut a deal with the power company to sell them your excess power? That's what I would likely do, if/when I ever make the jump to my own home energy generation. And as long as you are already wired up to get power from the power company, it's supposed to be a reasonably easy/cheap way to "store your excess energy". And in many (most?) states in the USA, there are even laws that state the power company has to make arrangements to do this for you (if you desire this service). So if you are already wired up to the power company, why not use them as your own (huge capacity) "battery" (i.e. sell them your extra power when you have it, and then "buy it back" when you aren't generating as much).

NOTE: I know that the power company doesn't have batteries either. However, it frequently turns out that when "renewable power sources" (especially solar) are generating the maximum power, is also the time of peak utility energy demands. So the power company often "wins" (as well as the homeowner) with such arrangements, as the power they buy from homeowners can often save them from having to buy the most expensive "peak power" they would otherwise have to get to meet demand (and conversely, when your system isn't generating much energy, is often when the power company has the most "free capacity" to sell you power with). So while the power company isn't a "battery" per se, it's still true that deals with homeowners (that generate their own power) can help "even out the load" for the rest of the power system.

[omgwtfbyobbq]

Given a 1kw system, that produces at that output for ten hours a day, that should be the equivalent of 1000J/s, or ~36 million Joules per day. Now we need some combination of capacity and pumping distance, and since water weighs ~3.78kg/gallon, some combo of 972,000 (meters*gallons), which is a lot of water/distance. I suppose it's doable under the right conditions, like two ponds with a significant difference in elevation, but for the most part, not practical.

[onegammyleg]

Hi theclencher.

-dont forget the Hummers.
http://car-audio-video.info/offroad/hummer-h2.jpg

[JanGeo]

Heat into the house is the same idea I had too and a big cistern in the basement to store the heat should work well also big compressed air caves is supposed to be the "new" thing. Big lead storage is what is typically used. Selling back to the grid really doesn't pay well at all . . . talk about losses!

[omgwtfbyobbq]

How about this way to put all those stupid SUVs to work... Have a tall tower or an old crane lift the heavy suckers waaaaay up in the air, then generate when you let 'em down.


I was thinking about that too, but dismissed it because of the huge weight needed, but that could be anything, even barrels of dirt, and could be lifted very very slowly with appropriate gearing. I honestly don't know enough about electric motors/generators to guess about the viability/efficiency (probably <20%), but it's an interesting idea. There's also compressed air and maybe even electrolysis of water, but they're probably not very pragmatic.

[onegammyleg]

Hi omgwtfbyobbq -¨but it's an interesting idea. ¨

It does sound good when thinking that whatever amount of energy is stored (already lifted weight) that it stays stored untill you want it., but yeah , prety well all of the electricity storage ideas I can come up with that involve mechanical devices seem to have large losses. :thumbdown:

[kps]

I wonder how many dead disk drives I'd have to cannibalize for magnets in order to float a multi-ton flywheel?

[cfg83]

theclencher -

It's not either/or... sometimes insane people come up with good ideas!

I agree. Don't knock until it's quantified. Maybe this is another optional use for the Ram-Air Wind alternator from another thread.

Actually, this should be very quantifiable. It's just a "micro-hydro" power station. This could be part of a rainwater storage system two (as in *two* for one).

CarloSW2

[cfg83]

Hello -

It reads like DracoFelis answered most of the pragmatic questions. I think this solution requires an optimum real estate situation, i.e. a hill that you own to locate the upper storage tank (or hole in the ground that you dig), good precipitation, and such. Ten to one this has already been attempted by an 0ff-grid homeowner. Seems like a homepower.com or homeenergy.org article to me.

CarloSW2

[WisJim]

http://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity has a bit about pumped water storage.

We thought about doing this 20+ years ago when we had a place with a quarry on a hill top, but it wasn't the kind of quarry with pits full of water, so tanks or ponds would have had to be constructed. As it turned out, our wind generator located near the house at the bottom of the hill produced 90% of the power we needed, the rest supplied by rarely running an old engine driven generator, and later with PV panels, so we never did much except a rough estimate of piping cost, etc. , which was enough to scare me off.

Good old lead acid batteries work fine for me in this kind of situation, but using the power directly (such as solar hot water panels) can be cheaper.

[DRW]

Reminds me of when I lived in the mountains. Our house got water from a nearby stream, so we got a small water-powered generator. We had a water tank up the hill so there was plenty of pressure and constant supply. The generator was basically a 4" water wheel in a sealed housing with a fitting to screw in the garden hose. An automobile alternator was attached to the wheel. We got an AC/DC converter (rectifier?) to tricklecharge several batteries all day long. It was enough to power most of the lights, radio and TV at night, but we had to use a propane generator for the stove and fans. When the batteries couldn't keep the TV on anymore, it was bedtime!

The water coming out of the generator went in into the back garden which grew very well with a constant supply.

So let mother nature do the pumping. If you're house is efficient you won't need much power or storage capacity.