Bubba Battery?

[rnbraud]

I am from the South, and am a bubba, so ...

Anway, have an idea which may not be worthwhile, but ...

How about a mechanical storage battery. Using wind and/or solar we can create electricity, but I don't like batteries.

How about using the electricity to drive a hydraulic pump, which then drives several hydraulic cylinders which in turn compress a bunch of auto suspension springs welded to some I-beams. This way the energy will be stored in the springs and can be retrieved later by using the same hydraulic cylinders which empty into a hydraulic motor which in turn drives a generator. You could even use the power as you are charging.

Would this be possible? Are springs that efficient in storing energy? How efficient is a hydraulic pump in converting electricity to force? How efficient is a hydraulic motor?

Thanks for any input.

P.S. If this is totally whack, I don't mind constructive sarcasm!

[PHinker]

I've been kicking around similar non-battery storage ideas and ran some numbers on a system which compressed air to store the energy.  Unfortunately, air motors and compressors are phenomenally inefficient.  I figured the system would be 2-5% efficient at best. I'm not trying to dissuade you, just thought I would mention what I found.

Paul

[kitno455]

there have been some alternative storage threads here lately, search the board. here are your biggies:

hot water, elevated water, elevated weights, spinning flyweels, compressed air.

i like the elevated ones myself.

allan

[rnbraud]

Thanks for the replies.

I have read up on several alternative storage systems, but all seem to have major safety issues, especially in a residential setting.

High rpms, high pressures, large weights, large footprints really don't lend itself to practical residential applications.

The "Bubba-Battery", I probrabaly should rename it to the "Hydraulic Spring" battery, would be more compact, somewhat safer except for the hydraulic lines, and be simple enough for the usual DIYer to constuct. Also, it used junkyard parts!

I am not familiar with the efficiencies of hydraulic pumps and motors which is why I posted here hoping some of you guys might have hands on experience with hydraulics.

I will have to do a little more digging to see what the relative efficiences are of springs, hydraulic pumps, and hydraulic motors.

Thanks.

[RP]

I don't know about the hydraulics but the springs may be okay to store energy.  Usually the inefficiencies come in the conversion of one form of energy to another.

Compressed air is fine for storing energy but the act of compressing the air creates heat in the air.  This heat is dissipated in the compressor, tubing and tank and represents lost energy.  After the air cools it contracts (the pressure drops) and this is non recoverable energy.  When you use the air it expands (to do work) which cools it more so now you've got even less pressure.

The act of compressing a large spring doesn't seem to create a great deal of heat (compared to air) so it may be better at storage.  I suspect however that hydraulics system would be a loser.  Ideally you could use a direct mechanical means to compress the spring directly from the motive source (hydro/wind turbine).  This would involve gearing, etc. that would have its own losses from friction though.

My two cents worth...

[Norm]

   Elevated weights will work fine in my opinion

for something with a steady load, like a night

light...a few LEDs to start with ...those solar

lights....some people don't realize how much

energy is stored in those little AA rechargable

batteries they'll lift considerable weight!

   Anyway I had it posted somewhere here on the

board on how you could lift a weight slowly on

one end while it was unwinding and making electricity on the other end.

   Maybe you can find it.

                ( :>) Norm.

[Norm]

http://www.fieldlines.com/story/2005/5/5/163244/7164

Here it is...something like you had in mind?

                    Norm

[kitno455]

what? you have not noticed that a couple i beams separated by a bunch of huge springs is dangerous as all get-out?

the power density by weight of stretched rubber makes it a far better spring. in fact, you could add it to the bottom of a raised weight, to increase 'gravity'

if you are going to use steel for an experiment, i would suggest torsion bars instead of coil springs. they take up less space. try 4x4 chevy s-10, ranger, etc.

allan

[Kwazai]

from rough numbers I'd run in the past-you're into acre pond size water storage for any kind of useful batteries- not sure hydraulic pressures (1200psi) would help a lot. assuming you had the equivalent of a 15ft drop in pressure for a hydro system your still in the 80,000 gallon range for a conventional house to run better than a day off a 'battery'. I too do not like the social costs of conventional batteries. If you have the space- a couple of two acre ponds with a height difference would be the way to go- or damming up a creek into an acre size pond- then a large enough hydro generator to supply the 'on demand'(or peak) power needs. power = volumeflow rate*pressure* conversion efficiency if I remember right. somebody correct me if I'm wrong.

[rnbraud]

Thanks RP, I think you and I are thinking along the same lines.

Originally, I had dismissed mechanically compressing the springs, however, I may revisit it.

I still need to study up on hydrualics and do some calculations to see how much work can be derived from a spring vs say elevated water or elevated static weight.

Later.

[rnbraud]

kitno455, I was wondering when someone would catch this.

You are right, however, I think this can be managed somewhat by placing apparatus underground, or secured with nylon/kevlor straps. Either way there would be a great deal of energy stored there. On the other hand, that is the idea right?

Stretched rubber sounds interesting. Kinda like the weight machine advertised on TV. However, what is the lifespan of rubber?

Oooh, hadn't thought of torsion bars! Great Idea.

Man, I have a lot of research to do.

Thanks.

[rnbraud]

Norm, thanks for the info. I had already read the posting listed. Very interesting.

The "constant load" characteristic of a lifted weight kinda supprts my Hydraulic Spring system, since the output can be varied by opening or closing a valve that supplies hydraulic fluid to the motor.

I need to do a lot more research and do some calculations.

Later.

[ignesandros]

If you hate batteries, you could always pray for your rich aunt to die and leave you all her money. Then, buy some fuel cells. Run some to produce hydrogen from water and store it in tanks. Later, as you need energy, pipe some hydrogen back into another fuel cell to produce electricity. You could even improve efficiency by compressing the oxygen created in the first reaction and sell that oxygen or use it for your oxy-acetaline torch you can't live without.

(don't flame me, I realize this is the EXPENSIVE OPTION)

-Andrew