Pumping water as a kinetic energy battery

The farm style windmill pump can pump water up 10m.  Hydro power is wonderful but places where it can be used are rare.  So I was thinking about pumping water into an elevated cistern which can be drawn off into a filter system or through a pipe to drive a turbine generator.  I know hydro is normally run 24/7 and this would be more of a battery to facilitate charging the battery.  The water used for generation could go either into the filter system for potable water or back into the well.

The pumps are not cheap and hydro turbine generators are not cheap either, but they are both quite dependable once properly installed with only annual maintenance required for the windmill water lifter.  I would imagine that the turbine would ware better with only periodic use.

Depending on how much water the pump can lift, help from an open top cistern maybe, it might be possible to run the turbine round the clock for electric refrigeration.  I don't know.

Am I nuts here? 

paulusmj,

If your goal is to generate electricity, you'd be far better off using the windmill directly for that. If you have batteries at the end of the process, why not leave out the stuff in the middle?

Farm-type windmills have very low efficiency, and any tower built high and strong enough to hold enough water to make, say, a pelton wheel practical, would be very expensive. Do forgive me, but it's a bit Rube Goldbergian to connect all those bits together.

More to the point it's crucial to understand how much energy is lost at each step, converting it from one form to another. I would not be surprised if you ended up with only 2-3% of the energy initially available in the sweep area of the windmill (and that amount depends primarily on wind speed). Whereas if you generate electricity from a properly designed wind turbine-- assuming that you have a situation that would make wind-electric power practical to begin with, i.e. where the wind blows at 10mph or better a sufficient percentage of the time-- you might reasonably get 10 times that output.




d.

paulusmj wrote:
Depending on how much water the pump can lift, help from an open top cistern maybe, it might be possible to run the turbine round the clock for electric refrigeration.  I don't know.

Sounds doable.

Stored energy can be dangerous in most any form: it might be best to have the windmill pump as one feature of a much larger water system. As David mentioned, a tower would be expensive, but maybe some earthworks upslope would be less so. For the amount of energy stored, they will almost certainly be less expensive than a large bank of lead-acid batteries, and they'll probably also have other uses.

A keyline system would also allow rainwater to be collected at a high elevation, for another source of hydroelectric.

However, if it's only refrigeration, maybe a root cellar would be less work to maintain. If you need freezing, look into Paul Wheaton's Wofati ice house scheme. There are also solar absorption-type or adsorption-type heat pumps, that use solar thermal energy to drive the fluid processes inside and don't involve electricity at all.

Lastly, I have to agree with David that you'll get more electricity with an electric windmill. In fact, if you do want to store your energy as elevated water, you'll probably store more by having a reversible electric pump/hydroelectric turbine powered by an electric wind turbine: the control circuitry is priced fairly reasonably nowadays.

Thanks for the quick response.  I was thinking of this as a supplement to a wind generator.  It is said that solar and wind work well in tandem.  Lots of sun in the summer, lots of wind when it's not sunny.  The problem is what to do when you have neither.  I like steam, but gravity is always on so if I could store extra wind power in a form that serves multiple purposes (elevated water) then so much the better.

I don't see waste being a big problem in the system because once it is in place and going it lifts water which is useful in many ways.  I was just thinking about a good way to make use of that potential energy to augment electric production.

The idea of refrigeration was just because the few people I've heard of who were able to get hydro going from a suitable stream got an electric refrigerator since they had a steady source of electricity.  If you have enough electrical production capacity why not make use of it? 

Don't return water to your well, whatever else you do. Only in a completely sealed, geo-thermal heatpump is this a safe thing to do.

rockguy wrote:
Don't return water to your well, whatever else you do. Only in a completely sealed, geo-thermal heatpump is this a safe thing to do.

Thank you for that info.

While David is correct that you'll have lots of conversion losses, that's not exactly what we're looking at in terms of ROI.

A tower would probably be very expensive, but if you have the slope to put in a dam as Joel says, that should be fairly cheap.

The main advantage of this system is the fact that you don't have batteries to maintain and replace every so many years.  That is a significant cost that reduces your ROI in a traditional system.

With that said, I'd second the idea that it will probably be more efficient to keep your energies of the same type rather than going from mechanical to electrical (wind generator) to mechanical (pump) to electrical (turbine) to mechanical (whatever machine you're operating that's plugged in).  Wind powered pump to pneumatic hammer or whatever seems easier.

So ... kinda like this?

The idea that rattles through my head is two parts:

1)  big pond high up that is filled in many different ways

2)  generator that somehow matches demand - so the pond is drained for power usage on an as needed basis. 

paul wheaton wrote:
So ... kinda like this?

Very much so, I was thinking about simple windmill pumps to elevate water into a high tank with posible multiple stages since each of those will only lift so much water so high.  Although building an elevated pond is likely to be less work, more useful and more esthetically pleasing.  It could still be fed with wind pumping water as one of the sources.  I just know that land with suitable drop for microhydro is rare so I was looking at ways to get around that.

just for information the first post says 10m or about 30 to 40 feet, farm style windmills depending on the size and the pump, can pump up to a 1000 feet up,

my own windmills pump 280 feet up out of the ground, and then one pumps over 2600 feet horizontal and another 30 feet in elevation.

one bonus of a water pumper is most will function in lighter winds than a electrical wind turbine,

but I would think that unless conditions or one need a emergency supply of energy I really doubt that the system would be that practical,

as in my case the both mills pump about 2 to 3 gallons a min, when at wind speed that is making the machine regulate, to get that 300 foot of elevation,  so in 24 hrs, 3600 gallons  and that is with 24 hrs of wind, normally you do not get 24 hrs of wind, 

a 10 foot windmill only has a general hp at regulating wind speed, is about !/2 horse power,  and a 12 foot is only about 5/8 hp,  so if your only getting half of that reliably, the max power you could reap on a continual basis would be about 1/3 of that amount, or about 200 watts,
now if one would use for burst of power,  then a larger pip would capable of proving more power for a few mins or hrs at the most, to get any usable power out of it,

like other have said just using the mill for generation the power would most likely be the best solution,

If you happen to have a handy uphill pond for storing the water, I can see the logic of it.

However, there is one big difference between the pond-as-battery and an actual battery: controlling the output.  A proper electrical battery gives you as much or as little power as you demand from it.  If you are only running a 1-watt load, you are only drawing one watt from the battery (plus a small amount lost to inefficiency).  However, if you are drawing water from the pond to generate power as you use it, it is highly unlikely that you can tailor the water flow to meet your energy demand.  In other words, you are probably going to flow the same number of gallons per minute whether you draw 1 watt or 100 watts.  Any kind of automatic load sensing to adjust the flow rate would be horribly complicated and prone to problems.

In other words, you are likely going to waste a lot more of your harnessed wind power through wasting water than you would if you just charged up a battery.  Fine if you have lots of water and lots of wind to pump it, but you'll need to do the math to plan for that wastage.

Kieth is mostly right, there is however an easy work around.  A small battery bank, less cost than a large one, that you draw the electricity from and use the stored water power to regenerate those batteries rather than provide the electricity directly.  When the batteries reach a certain state of discharge the water power can be turned on to fill them.  That generator works at full capacity until the batteries are recharged thus making efficient use of the energy stored as water.  Battery recharging technology is well developed as is the technology for auto on and auto off switches.  More expensive than a no battery system but much less than an all battery system.

A tower would probably be very expensive, but if you have the slope to put in a dam as Joel says, that should be fairly cheap.

For that matter, a tank on a hill would work too.  I like the idea of pumping that water a little higher now to use as a battery later.

I have thought about using elevated water (or any form of potential kinetic energy) as a green alternative to batteries.  Imagine installing a bio-kinetic harvester (such as a hydrostatic displacement pump, or a trickle ram pump attached to a turn-style or a door-hinge) in high foot traffic area like a colliseum or a subway station so that you could generate energy passively with human movement.  Purely conceptual at this point, but I think the idea of using elevated water and bypassing the battery system is worth exploring.

Slightly different idea: how about using a wind mill (or any other suitable alternative energy device) to elevate a large pendulum as a kinetic battery?

Uncle Ned says:

The total horsepower developed by water falling from a height is the product of the mass flow rate in pounds per minute times the falling height in feet divided by 33,000.

The mass flow rate would be gpm*8.33 to determine it.

32 ft/s2 aka the gravitational constant

height

so

m*h*g
______
33,000

m-mass flow rate, h=height in feet, g=gravitational constant, 33k the work of 1 horse power can do in pounds per 1 foot.

Now the harsh reality, lifted water great energy storage, the real deal. Bad news though, decent pump efficiencies are in the 65% range unless you spend huge large. This is in fact why we lift water for storage to maintain water pressure, trying to pump it to that pressure at a reasonable flow rate would be 100 times more expensive and a huge waste of energy.

The above math will give you your falling horse power, HP / 746 * turbine generator efficiency is your electrical output capacity in watts.

Because of the double loss, you are better off without the pumping situation and storing the enrgies another way as your going to be rapidly approaching less than 20% of the actual energy put into the windmill being usable energy.

Hello Paul,

Only just discovered your post. Nice to know I am not alone and no you are not nuts. I fully developed that your talking about and put out to the world in Open Technology. My first accomplishment was to raise water to storage and flow back, next was to connect the hydro turbine direct to the pump. The pump itself is entirely my own design and uses gas pressure to force the water. The gas I use is Carbon-C02. However other more active gasses may be used though to date CO2 is the only one I have been able to get specific graph on as heat to pressure. But first of all back to the hydro turbine/generator. A one litre 9 bar per second 82% efficient (common) rotating at 60 RPM produces 720 watts. This increases by pressure, volume or rotation. Next the pump, this being the DaS Valve also fully developed by myself. It works on the principal that gas shall rise to the surface in liquid. A heat expnding gas pocket above water creates a water pressure exact to that of the gas pressure. This gas pressure is whats used to drive the water from the pump. The minimum 9 bar pressure requirement is reached at minus 10* Celsius, the same gas at plus 100* Celsius produces 10,000 pressure. The pump being fully sealed is 100% recycle. The complete device is constructed by cut and weld of pipe. Care should be taken in pipe strength to make sure it can handle the pressure requirements. I used line pipe for 10,000 bar pressure (720 kilowatts). The three attachments are complete engineerings of the DaS Valve, the ambient heat hydro turbine generator and the CO2 pressure to heat graph. Most happy to help further.

Cheers Peter

Water as energy storage:

1 kwhr = 10 cubic meters of water (= 10,000 liters = 25,000 gallons) elevated 36 meters (100 feet)

Double the water, half the height.

And that's with perfect efficiency. Not practical for us peasants.

Hello S. G. Botsford,

I cannot debate your figures as I am solely reliant on California University School of Hydro turbine power generation.

One litre of water per second falling ten feet upon a 82% efficient hydro turbine/generator produces 720 watts.

Increase to 1.5 litres per second gives the 1 killowatt output.

A storage of 5,400 litres elevated ten feet shall supply 1 Killowatt hour. 1 kilowatt constant 24 hours requires a storage of 129,600 litres.

A storage of 5,400 litres elevated 240 feet shall supply 1 Kilowatt constant for 24 hours.

Such storage usualy takes place on sloping land, ie house at top and generator at bottom land.

However this brings a new dimension into play as windmills are terribly inefficient as to the head they pump to so source water needs be close to storage point.

Alternate is windmill pumping to small tank on ten foot stand. Though when theres no wind there no water pumpage and as conseqequence no electricity production.

Chhers Peter

A liter of water weighs a kilogram.
Force of gravity on 1 kg is just under 10 nt.
10 feet is close to 3 meters.

A liter per second Energy = force * distance
E = 10 nt * 3 m = 30 J

It would produce about 30 watts. At 82% efficiency it would be about 24-25 watts.

Even 1 liter per second however is 3.6 cubic meters per hour

Do you have a link for that figure?

Googling "California University School of Hydro turbine power generation" I am unable to find a web site for them.


http://www.engineeringtoolbox.com/hydropower-d_1359.html is an online calculator.


Note that efficiencies even as high as 80% are unlikely at such low flow rates. Too much loss in the plumbing

This also may be of use to you:

http://www.smallhydropower.com/manual3.htm

Hello S. G. Botsford,

Sorry dont have web site any more, three hard drives ago, found by search Hydro Turbine. The figures I quote are direct fro that web site.

Shall go look again for myself and get back to you.

Cheers Peter

Hello S. G. Botsford

Sorry cant find. Was web education California University. Turbine was Francis. Even had a picture of hydro plant in canyon 1 litre per second. 9 bar pressure, 720 watts. Thank you, am aware of other sites that at best give 32 watts though some rate turbine efficiency 60% and Francis is 82% efficient.

Shall now chase old company records they should have something, year of research was 2002.

Cheers Peter

Hello S. G. Botsford,

Found one web site but not california university.

http://www.fortunecity.com/skyscraper/fortune/284/hydro.html

Cheers Peter

A wind generator with 3 phase output connected through a control panel to the ordinary 3 phase motor without battery, inverter is a true water pumping arrangement for a farmer who is blessed with 6-10 hours wind near him farm and well.

I guess you'd want 2 ponds, as well. One high, one low. So, the water would go from high through electric generation, then down to low pond. Then, you have another windmill or solar water pump pumping back up to top pond.

The problem, however, is that you need a very large pond to store any amount of usable energy, Plus, evaporation and soil infiltration takes away your power.

One L per second is 86400 liters per day, and that'll yield about 14 kWr a day (that's 10 times what I use in a day). That's more water than I use for my house in an entire year.

So, for me, let's scale it back by a factor of 10. I only need about 1.5 kWr per day. So, that's about 8640 L a day (probably more like 10,000 L a day with losses and such). Still a lot of water, but somewhat doable, and easier to cover and protect from evaporation. I'm currently on solar, so maybe just run this at night, and do it with 5000L a day. That might be doable with 2 X 5000L tanks, one on top of the hill, one at the bottom.

Now, if those holding tanks were also fish tanks, and pumping the water back and forth was situated to help aerate it, you could be stacking some functions there.

The point being, don't put all your eggs in one basket. Have some wind power, some solar, some batteries, some water storage, and your system will be more resilient.

Not nuts at all!

You're talking about pumped storage. There's case study in Serious Microhydro: Water Power Solutions from the Experts that used a turbine to pump water uphill and then run a small turbine/battery/inverter system.

Utilities do that sometimes, especially where money is no object and power is short, like in Hawaii.

That said, pumped storage is very inefficient. Every time water goes in or out of the tank, there are pump and generator losses. These add up rapidly. Really, batteries aren't so bad in certain situations.

With the case study mentioned above, perhaps the necessity for pumped storage would be eliminated by using a smaller, more efficient turbine for low flow periods.

Solar and wind power go well together...lots of people have them. The three factors with wind power are: Tower height, tower height and tower height. Many of the old style farm wind machines do well at pumping, which is a low speed affair. Generating electricity involves higher rotational speeds to get generators small enough to be practical. A small (say 1 kW) machine will produce a surprising amount of power on a tall tower. But that's wind...


Cheers,

Scotty

solomon martin wrote:I have thought about using elevated water (or any form of potential kinetic energy) as a green alternative to batteries.  Imagine installing a bio-kinetic harvester (such as a hydrostatic displacement pump, or a trickle ram pump attached to a turn-style or a door-hinge) in high foot traffic area like a colliseum or a subway station so that you could generate energy passively with human movement.  Purely conceptual at this point, but I think the idea of using elevated water and bypassing the battery system is worth exploring.

Slightly different idea: how about using a wind mill (or any other suitable alternative energy device) to elevate a large pendulum as a kinetic battery?

lol I would castrate you if I found out I had to walk harder to generate your power

Hi,  I would be interested in picking up this thread and know what you would recommend seven years on factoring the current costs of micro hydros and deep cycle batteries. We have a rise in our property that would probably just be 3m / 10ft high.

I do have on-grid electricity, but will have a separate solar/wind system I will set up myself, and already have 10Kw battery storage capacity we got for a food trailer.  I pay NZ33 cents  (US 24 cents) per KW.

We are starting a home-based food business, so will be doing quite a bit of early morning baking, and so could use this additional storage on a daily basis for this.

Annie,

This is a super interesting idea, and while there are some grid-scale pumped hydro energy storage setups around the country, the processes don’t scale down very well to the homeowner level.

As has been mentioned earlier in this thread, every time energy is changed from one form to another energy is inevitably lost.  Wind to mechanical energy (turbine) to electrical energy (generator) back to mechanical (water pump) to another form of mechanical energy (water wheel) to electricity (another generator) is a lot of steps.  Each step costs money to build and each transition looses energy.  As what was mentioned a while back (in 2010 no less) is essentially correct.  Converting wind directly to mechanical energy to drive a pump does skip a step, nonetheless the losses are huge.

Far better is to convert to electricity, charge a battery, then discharge the battery.  There are still significant losses but better than the pumped hydro storage.  For batteries I would suggest lead acid deep cycle batteries which allow a full discharge without damaging the battery and are relatively cheap as batteries go.

Grid scale pumped storage can take advantage of some large scale efficiency, locally elevated terrain and highly optimized (and expensive) equipment.  Home scale likely gets none of those.

Please don’t read this as being a negative post.  I actually get really fascinated with all things energy related.  I strongly suspect that if one really does want to go grid independent and hydro is not an option then a combination of solar and wind with a decent battery backup is the most efficient way to go—both by cost and by energy conversion standards.

Super interesting topic and I would love to hear other thoughts and especially challenges to my basic assumptions.  I have studied this in graduate school, but changes do occasionally occur.

Eric