# Micro Pumped Hydro Storage

Registered Users Posts: 7 ✭✭
I did a quick search and didn't see this topic covered. Sorry if it has.

Is anyone out there doing micro (miniscule) hydro pumped storage? From say 5000 gallon tank to 5000 gallon tank?

I have a tank (its actually 30,000 gallons solar well fed) on a hill above my house and get 100 psi to my house (the rise? Id guess 200 or so ft)

Im off grid now with about 300 watts of tracker solar and 12 volt battery bank at 800 amp hours.

What Im wondering is if it would be feasible to used pumped storage when my batteries are full. So most of the time I would depend on the batteries and solar like it is now. But in this case when the batteries get full the solar power would power a pump that would pump water from a lower tank near my house to the upper tank. When my batteries get low at night and there is water in the upper tank, I could open a valve to power a very small pelton wheel (output of 100-400 watts) and use this to I would assume recharge my battery bank (rather than try to use the pelton tied directly to my inverter.

Has this been done? I know they are doing this for large scale grid peak applications but is it being done on a very small scale?

Jameson

Re: Micro Pumped Hydro Storage

You can use a site like this:

http://www.oregon.gov/ENERGY/RENEW/Hydro/Hydro_index.shtml

Following is wrong (thank you Malcom):

To figure out how much power you can generate for 5,000 gallons of water:
Gross Head x Flow x System Efficiency (in decimal equivalent) x C = Power (kW)
C is a constant (the value is different in English and metric units).
• 100 psi / 2.13 psi per foot * 1 cf/s * 0.55 turbine eff * 0.085 = 2.19 kWatts
• note fixed 0.85 should be 0.085
• 5,000 gallons * 1/7.48 gallons per cuft * 1/1cf per sec = 668 seconds = 11 minutes of power
Looks like a lot of "work" for little "work"... 2kWatts for 11 minutes.

Fixed:
Yep, I think your are correct (and I messed up several ways)... 100 PSI is 232 foot head, not 47 feet. I messed up several ways.
• 100 psi * 2.32 foot per PSI * 1 cf/s * 0.55 turbine eff * 0.085 = 10.846 kWatts
• 5,000 gallons * 1/7.48 gallons per cuft * 1/1cf per sec = 668 seconds = 11 minutes of power
• 10.846 kWatt * 11 min * 1/60 min per hour = 1.99 kWH per 5,000 gallons of water

More power, but still not a huge amount... If you want to run 1 kWatt:

1 cfm * 1kW/10.846 kW = 0.0922 cfm
11 min * 1 cfm /0.0922 cfm = 119 minutes

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 7 ✭✭
Re: Micro Pumped Hydro Storage

Bill, Thanks so much, that was just the answer I was looking for.

Stored chemical energy wins over kinetic energy

Cheers.

Jameson
• Solar Expert Posts: 593 ✭✭
Re: Micro Pumped Hydro Storage

A lot of talk is made about pumped water as a method of storing wind or PV power in order to time shift it to peak periods.

What Bill just pointed out is generally the stopping point. Too big of a reservoir and too much head is needed. Not many places have the geography to support such a solution.

Not to worry though - İ am sure one of the 'green' blogs will be pushing pumped storage again next week as if it is the answer to all problems.
• Solar Expert Posts: 144 ✭✭
Re: Micro Pumped Hydro Storage

Every type of "mechnical" storage is a waist of money and energy on small size.

You will find a nice topic about compressed air in this forum.

Preheating water is a better solution to use spare energy.

Greetings from Greece
• Solar Expert Posts: 8,972 ✭✭✭✭✭
Re: Micro Pumped Hydro Storage

Dang! I was thinking about something like that for myself, now i have to figure what size pipe could drain the 5,000 gallon tank in 11 minutes !
I have pond, and hill, but not enough \$ this year.
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• Solar Expert Posts: 157 ✭✭
Re: Micro Pumped Hydro Storage
mike90045 wrote: »
Dang! I was thinking about something like that for myself, now i have to figure what size pipe could drain the 5,000 gallon tank in 11 minutes !
I have pond, and hill, but not enough \$ this year.

All it would take is a 1/2" pipe...

Installed at the base of the tank...

And then filled with black powder and detonated. Of course, it'll probably drain the tank in less than 11 minutes, and connecting it to your turbine might be tricky.:p

I've been looking at micro-pumped storage lately, but, sure enough, it only makes sense if you already have a big pond (or place to dam up a big stream) up a big hill.

Pity that molten-salt storage is so inaccessible to small-scale DIYers.
• Registered Users Posts: 1
Re: Micro Pumped Hydro Storage
BB. wrote: »
You can use a site like this:

http://www.oregon.gov/ENERGY/RENEW/Hydro/Hydro_index.shtml

To figure out how much power you can generate for 5,000 gallons of water:
Gross Head x Flow x System Efficiency (in decimal equivalent) x C = Power (kW)
C is a constant (the value is different in English and metric units).
• 100 psi / 2.13 psi per foot * 1 cf/s * 0.55 turbine eff * 0.085 = 2.19 kWatts
• note fixed 0.85 should be 0.085
• 5,000 gallons * 1/7.48 gallons per cuft * 1/1cf per sec = 668 seconds = 11 minutes of power
Looks like a lot of "work" for little "work"... 2kWatts for 11 minutes.

-Bill

Hi, I'm very interested in pumped storage, as I hate the care and feeding of batteries. Those in my golf cart are plenty bad enough.
I believe you're selling the process short, as you apparently got a couple of things backwards in your calculations.
You said,

"100 psi / 2.13 psi per foot * 1 cf/s * 0.55 turbine eff * 0.085 = 2.19 kWatts
note fixed 0.85 should be 0.085
5,000 gallons * 1/7.48 gallons per cuft * 1/1cf per sec = 668 seconds = 11 minutes of power

Looks like a lot of "work" for little "work"... 2kWatts for 11 minutes."

To determine head, in feet, you should have MULTIPLIED 100 psi by 2.31 (not 2.13, btw).

Thus, the head would actually be 231 feet-much better than he 47' of head from your calcs!

All else being equal, you would therefore be able to produce electricity for, not 11 minutes, but 54 minutes. Ok, that's still not all that impressive, but it does seem like stored hydro could be used in some situations. For instance, I could build a tank or pond at the ridge top above my house, and have just under 500 feet of head. This would allow me to produce (at the same 2.19 Kw rate you used) for about two hours. And of course, if I built a larger pond(s) I could increase my timeline substantially.

What's keeping me from doing this is, mostly, my ignorance as to how to install and wire a pelton wheel and generator to produce ON DEMAND power. Any ideas on THAT?

I'd greatly appreciate any help!

Malcolm
• Solar Expert Posts: 1,384 ✭✭✭✭
Re: Micro Pumped Hydro Storage

I would think a voltage sensor connected to a throttling water valve.

A 10,000 gallon tank filled by a ram pump might be an interesting way to get bursts of electrical power.

I am available for custom hardware/firmware development

Re: Micro Pumped Hydro Storage

Yep, I think your are correct (and I messed up several ways)... 100 PSI is 232 foot head, not 47 feet. I messed up several ways.

• 100 psi * 2.32 foot per PSI * 1 cf/s * 0.55 turbine eff * 0.085 = 10.846 kWatts
• 5,000 gallons * 1/7.48 gallons per cuft * 1/1cf per sec = 668 seconds = 11 minutes of power
• 10.846 kWatt * 11 min * 1/60 min per hour = 1.99 kWH per 5,000 gallons of water

More power, but still not a huge amount... If you want to run 1 kWatt:

1 cfm * 1kW/10.846 kW = 0.0922 cfm
11 min * 1 cfm /0.0922 cfm = 119 minutes

I will correct my post.

Thank you,
-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 1,571 ✭✭
Re: Micro Pumped Hydro Storage

Here are two online calculators that'll do the work for you:
- Calculate flow rate: http://www.calctool.org/CALC/eng/civil/hazen-williams_g
- From flow rate calculate hydro power: http://www.reuk.co.uk/Calculation-of-Hydro-Power.htm

I looked at this idea a while back when considering building an irrigation dam, so was thinking of building 2 smaller dams instead of 1 big one and using pumped hydro between the two. But if you add all the additional costs of piping, hydro generator + grid tie inverter (which I'd need because of the distance to the second dam), then the costs start approaching that of my existing forklift battery.

It may be more feasible if you already have both storage reservoirs and the pump setup and are just looking to install the hydro gen. My rough calcs here: http://www.casanogaldelasbrujas.com/blog/2013/01/17/rough-calculations-for-mad-pumped-hydro-idea/