Pumped hydro, the real issues....

HammaMan

Solar Enthusiast
Per the AMA, the big issue with pumped hydro is you need a good 150m+ worth of head and a big ass area to store a lake worth of water. The larger the elevation, the less water is needed per given unit of power. It's not practical on a small scale. You also need a lake's worth of water to move every day. Here's one the utilities around here use.

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Plant specs
 

Short_Shot

Photon Sorcerer
Well, if you have a cliff over the sea, for residential use you don't quite need a lake.
Yeah lol the headaches of seawater alone drive up the price of such a system by a rather significant margin.

And you certainly need a lake if you expect any economy of scale.
 

Don B. Cilly

Energetic energy padawan
Yeah lol the headaches of seawater alone drive up the price of such a system by a rather significant margin.

And what would those headaches be, exactly?
I'm a (retired) boat captain, so quite familiar ;·) with seawater. We use it for lots of systems. First stage engine cooling, toilets, anchor washing... it runs through pumps just fine. So why not turbines.

And you certainly need a lake if you expect any economy of scale.

What would the economy of scale for residential (a house) be?
 

Short_Shot

Photon Sorcerer
And what would those headaches be, exactly?
I'm a (retired) boat captain, so quite familiar ;·) with seawater. We use it for lots of systems. First stage engine cooling, toilets, anchor washing... it runs through pumps just fine. So why not turbines.



What would the economy of scale for residential (a house) be?
Those headaches are everything you deal with except at a much larger scale. How much stuff have you replaced over the years? Now scale that up to large equipment, bigger pumps, much, much more pipe, and ask the associated control and electronics being larger and thus more expensive to replace.

Why larger? Because...

Economy of scale means for a single house the gains are vastly outweighed by the huge costs. ROI would be virtually nonexistent.

The only time this method makes sense is at far larger scales powering hundreds or thousands of homes, and even then doing so with saltwater makes it impractical.
 

Short_Shot

Photon Sorcerer
If you're wondering about it, consider that the world's first pumped hydro with seawater was built in 1999 and dismantled in 2016. The primary reason was for lack of power demand.

The difficulties of seawater can of course be managed with the right design as you should very well know. They solved those issues here, but the cost at a smaller scale is prohibitive.

They had demand of much more than a single home and still folded because the economic viability was not there. They were only trying to deliver 2% of the demand and still couldn't make it happen.


 

Short_Shot

Photon Sorcerer
Oh and even if you did do so at a single home scale you still need several large swimming pools worth to make it through the night of an average home, depending on height.

Good luck building a 150 meter tall tank as well, so the water volume needed increases the lower you go.
 

Don B. Cilly

Energetic energy padawan
Well, I don't know (I've never tried :·) Mainly because I don't have a cliff, though :)
A deep-well pump that can pump 150+ metres is a non-problem. Not expensive either.
If used often, seawater won't affect it much at all.

The reservoir... again, I don't know, but to get the equivalent of, say, 400 Ah worth of batteries? I guess not all that much, right?

Turbines are not expensive either. Home hydroelectric installations use them. And obviously, hydroelectric is the Holy Grail of power. It will run day and night, needs virtually no storage, etc. You just need a river that doesn't run dry ;·)
 

Short_Shot

Photon Sorcerer
The reservoir... again, I don't know, but to get the equivalent of, say, 400 Ah worth of batteries? I guess not all that much, right?
Lots of "probably" and "maybe" and "can't be".
Assuming you have a pretty nice generator that's 80% efficient (though if you spend big bucks you can get 90% or more) you're looking at 1 cubic foot of water per second from 20 feet of height through a 6 inch pipe giving you 1.35kw.

Assuming your 400ah of batteries I'll just go with 12v and call it 4800wh. So you'd need to run that system for 3.55 hours.

At 1 cubic foot per second you need 12,791 cubic feet of water, or at 7.48 gallons per cubic foot, 95 673 gallons placed 20 feet above your turbine.

That's all napkin math of course but as you can see it's a lot of water.

Screenshot_20210922-022104_Chrome.jpg
 

Short_Shot

Photon Sorcerer
Oh and you'd have more power loss pumping that water up during the day than you would by just putting it into batteries.

The system would cost vastly more than just buying lithium.

Even if you quadruple the height to 80 feet you still need tens of thousands of gallons and a cheap galvanized 30 thousand gallon tank costs 29 grand plus assembly and plus the cost to mount it 8 stories above the ground.
 

Don B. Cilly

Energetic energy padawan
If we started with a 150 metres (450 feet?) cliff, why are we talking 20 ft, 80 ft, and such?
And why not use "sensible" units, that make sense arithmetically, like metres and litres? And metric tons convert really easy, too... water, one cubic metre=1000 litres=one metric ton (1000 Kg.)... salt water, close enough.

So we have the cliff. We don't install anything any feet up. The reservoir is on the ground. The pump is down by the water. It's deep-well pump...
A little excavation and some roofing felt would do fine, actually, or plastic containers.
I don't have the cliff. Do you? :·) Hence the ifs and buts.

There's also a difference in attitude between a problem finder and a problem solver... I belong - everyone says - to the second category :)
 

Short_Shot

Photon Sorcerer
If we started with a 150 metres (450 feet?) cliff, why are we talking 20 ft, 80 ft, and such?
And why not use "sensible" units, that make sense arithmetically, like metres and litres? And metric tons convert really easy, too... water, one cubic metre=1000 litres=one metric ton (1000 Kg.)... salt water, close enough.

So we have the cliff. We don't install anything any feet up. The reservoir is on the ground. The pump is down by the water. It's deep-well pump...
A little excavation and some roofing felt would do fine, actually, or plastic containers.
I don't have the cliff. Do you? :·) Hence the ifs and buts.

There's also a difference in attitude between a problem finder and a problem solver... I belong - everyone says - to the second category :)
Because you're talking about home scale.

Home scale user won't have 150 meters of elevation.

Your idea of a problem solving attitude seems to be more along the lines of "insisting it can be done then leaving everyone else to figure it out".

That's not problem solving. It's not even problem finding. It's problem creating. The problem doesn't exist because lithium is far more economical, so there's no sense in even attempting to build a pumped hydro system at the small scale.


You don't have a cliff. I don't have a cliff. The vast majority (>99.9% I'd bet) of the population does not have access to a 150 meter cliff.
So because you are insisting on single home scale, I did the math based on what is technologically viable for a single home scale user.

Furthermore, for your 4800wh, 450 feet up is 22.5x the height of the 20ft I used.
To get your 400ah equivelent still requires 4252 gallons of water.

A 4500 gallon tank still costs almost $8000 USD. Even buying battleborns you can get twice the energy storage out of that money and that's before you buy a pump, turbine, or any of the other infrastructure you need.

If you DIY the pack you can get 8-9x the storage from batteries for the price of the tank alone.

Simple fact is it's not economically viable. The ROI is negative. The energy storage is vastly more expensive per watt hour than lithium.

Regarding what you consider sensible units; your opinion on what units I should use is largely irrelevant to the results. I deal with gallons on a daily basis, so it's easier for me.

Since you aren't bothering to do any of the math (read: actual problem solving) I'll use whatever suits me.

4,252 gallons of water is just under 20,000 liters by the way.
 

Short_Shot

Photon Sorcerer
So no. You're not at all being a problem solver here by insisting on a non-viable method of energy storage at a single home scale.

If your goal is just to show that it's physically possible then sure, you did it, gold star.
If you have the perfect piece of property in the probably 1 or 2 places in the world where this could be done using only the natural landscape then sure.

However that kind of means nothing when the original comment about why you shouldn't do this was entirely a matter of financial reasons.


The fact that just the tank alone costs more than the equivalent in lithium batteries shoots this in the foot even if you gain the elevation and all the other equipment for free and with zero work.

I enjoy these debates but the "problem solving" makes it clear: this absolutely is not viable for anything less than grid scale, large public works projects.
 

Short_Shot

Photon Sorcerer
What's your point?

Even if you have the cliff, the tank alone costs 2-8x as much as the equivalent capacity of lithium.
 
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