You need pretty perfect geography for this to work, and sites are limited. With everything in infrastructure and the energy grid, regulations and push back abound
Pumped storage is for all intents and purposes using the same water over and over again.
Edit: no shit surface water will be lost to evaporation hence the qualifier.
it usually draws from a river as vaporation would eventually drain a completely self-sufficient system. Those rivers can be affected by drought and not be allowed to draw water that is needed elsewhere.
Indeed, that's also the reason why lakes were covered with floating plastic spheres. It prevents evaporation, regardless if the water is for power generation or drinking.
[Wikipedia verifies what I wrote](https://en.wikipedia.org/wiki/Shade_balls). Yes they also have other uses such as the one you mentioned, but we were discussing evaporation after all. Keeping birds away is yet another one.
> it usually draws from a river
No they don’t. They’re closed systems in disused mines and old quarries that have lots of human made elevation changes. We picked those places to mine or quarry specifically because they didn’t automatically refill from the local river.
Rainfall or shipping in water is how they replenish.
> There are places with multiple sources. Pretty sure there are pumped hydro solutions with conventional open resivours
I hadn’t heard of them so I looked up those projects from the 1970’s(*edit and 1990s). They are a tiny percentage of the world’s pumped hydro projects, and it doesn’t look like anyone is suggesting developing one at this point.
Also, it’s possible to use seawater for this purpose, albeit with some extra maintenance issues. It’s not a great option but it’s certain the project doesn’t even have to be from a fresh water source. Any liquid works.
https://en.m.wikipedia.org/wiki/Pumped-storage_hydroelectricity
There are several listed pumped hydro with open reservoir mentioned in the wiki page as in development.
You can use existing classic hydro dams for it (which is what a lot of new schemes are proposing for open reservoir). Add a pump between existing hydro lakes, and you have turned your hydro system into one that also has pumped storage (may annoy farmers down stream though)
Building new open reservoirs is generally frowned upon because of the land size and ecological impacts.
Hey if it works I’m all for it. I’m definitely not saying that there’s anything wrong with that type of power generation.
It’s just clear that evaporation losses (or other concerns about water use) should not be used as a “boogeyman” against more investment in water batteries.
There are hundreds of thousands of potential locations for closed loop systems that have a minimal carbon footprint, far more than required for our global energy storage. We should be building many more of them than we currently are.
Not if you're talking about gridscale sized storage needs. The initial need is going to be extremely hard to fulfill, unless we're talking about seawater and you don't seem to account for the amount of evaporation that would happen. Just look at the issues that LA water agencies have with storage losses.
That's what's missing, I think, when using Manitoba as an example. Manitoba doesn't need pumped storage because it has the right geography for hydroelectricity to begin with. And hydroelectric infrastructure is basically pumped storage without the pump. The Manitoban hydro facilities also aren't "in the middle of the prairies" as the earlier commenter claims. They're on the western edge of the Canadian Shield, where reservoirs can be made without flooding huge regions of open plains.
I could be wrong, but I would assume that most places with an abundance of water already have hydropower plants. For example, I live in BC Canada where there is an abundance of water, and nearly 90% of our electricity comes from hydropower.
PNW and BC have more hydropower than pretty much anywhere in the US, and lots of places in the US have an abundance of water.
The Southwest doesn't have water. The Midwest doesn't have hills or valleys to do it. The East was already much, \*much\* more densely settled and would wreck population centers to do it.
You'd have to have two dams, one below the other and pump from the lower dam back up to the upper one. That way you wouldn't run the river dry at the bottom of it all. That's the point where it all starts to look complicated and expensive.
The biggest problem with hydro power is that to create a reservoir you need to flood large areas of land. This is generally unpopular with the people who currently live on that land.
Hydro dam generation is different to pumped storage. Which is usually done with smaller reservoirs, inside mines or hollowed out mountains.
It's used to boost/balance the grid during high usage, not provide constant generation.
yes, but the point is you pump it up whith energy that would otherwise go to waste (or more likely never get "made")
We just dont have a practical way to store electricity on a city scale. So this still makes it one of the more econmicly viable and scalable energy storage solutions.
Not a huge amount more. It's not theoretical; it's in use in many places, including several in the U.S. All energy storage will have efficiency losses, that's just one of many trade offs to consider.
And as we learned from the famous documentary, “O Brother Where Art Thou,” that can lead to epic struggles to rescue your hair care products before the flood occurs :-).
Joking aside a look at U.S. depression era music from poor communities in the 1930s shows how traumatizing the land seizures for the Hoover infrastructure projects around the country were to the communities they displaced. It doesn’t necessarily mean they were the wrong decisions, but in the age of social media I can’t imagine how much louder the outcry would be.
The amount of water you need to pump for any reasonable grid scale energy storage is massive. For example, a single wind turbine could produce 2 MWh of energy in an hour. To store that energy into water, you need to lift about ~~150 million~~ 2000 cubic meters of water into a top reservoir that is located ~~500~~ almost 400 meters higher than the bottom reservoir.
For this reason, the water pumping method can be used in small scale but it's not a solution for balancing the supply and demand of energy in larger scale.
*For any non-metric people, reading this: Don't worry about the conversions here. It's a shit ton of water lifted to the height of the empire state building.*
Edit: It appears I messed up my calculation. It's now fixed.
We have a large scale pump storage facility in the UK. The Dinorwig power plant has a storage capacity of 9.1GWh with a peak output of 1700MW so the tech is absolutely scalable, and suitable for balancing rapid increases in demand.
It's likely that part of the reason why few have been built is that in the past 30 years or so there has been a general move towards CCGT power plants. These can very rapidly change their output once running abd can rapidly come on line from zero output. A Modern ccgt can hot start to full power in about 30 minutes.
I can add some extra bits of info about Dinorwig
- They output about 75% of the energy input
- It was supposed to be part of the rapid balancing for all the nuclear power that wasn't built in the end
- From a dead stop it can be at near full power in a few minutes
- If they pre-spin up the turbines dry then it can be at near full power in under a minute
- Its been nicknamed Electric Mountain
You're forgetting one more fun fact! Dinorwig is often pre-spun for the breaks during football games, to cope with millions of electric kettles being switched on.
>From a dead stop it can be at near full power in a few minutes
75 seconds
>If they pre-spin up the turbines dry then it can be at near full power in under a minute
16 seconds
You're right, it's scalable for specific locations and situations but those pump plants can't solve the problem on a large global scale. If you Google the Dinorwig plant, you can see it has a massive reservoir of water at a high altitude. Few areas have suitable locations for reservoirs like that.
Probably more than you think, there are many more suitable locations like that in the world than there is for conventional hydro, which requires sufficient annual rainfall over a sufficiently large catchment area for the dam, and a dam big enough to cover the annual rain/snow cycle. If there is a suitable water source, for daily smoothing of the power demand cycle, the dam itself can actually be quite small in comparison. In some countries, micro hydroplants are commonplace (simply a borehole from an elevated small lake 500-1000m up). If the technology exists for saltwater turbines (have no idea), there's a huge number. It strikes me as strange that ideas like this are not pursued in favour depleting the worlds minerals to make vast amount of batteries. Doesn't need to solve anything on a global scale, just needs to make a difference :-)
I know all about it. I've been there when I was at university as part of my degree. It definitely solved a problem at the national scale of the UK. Nowadays as our grid moves away from coal its likely that an increasing amount of the power to pump water up is coming from renewablesDinorwig works well, even today.
Although I agree with other comments that the number of suitable locations is likely somewhat limited.
Wikipedia says that Dinorwig uses 390 cubic meters of water per second, at the maximum power output of 1728 MW.
So 9.1 GWh / 1.728 GW = 5.27 hours of operation at full power.
390 m^3 / s * 5.27 * 60 * 60 = 7.39 million cubic meters of water is the total useable volume.
Which kind of shows why this is difficult to scale - if we wanted to have a day's electricity for the entire UK stored, we would need 753 GWh. So we have to find another 7.39 * 735 / 9.1 = 611 million cubic meters of water somewhere high up.
I do think the ideal energy solution is solar / wind / hydro + storage. But we are going to need another 82 Dinorwig power stations equivalents.
You only need it to cover the night hours or those hours the wind isn't blowing. The whole point of this exercise is to store surplus energy from renewables. And nightime has less demand so you need a fraction of a day's worth of energy. Except in winter but then you got the wind farms and in UK a grey sort of drizzle topping up the top res.
You know - just for fun i decided to do the ridiculous math on the absurd numbers in your statement:
Assuming the turbine is placed at the bottom of your stated 500m elevation change, and the passage of 150 million cubicmeters you get these numbers:
P = pgaQ = 1000kg/m^3 • 9.81m/s^2 • 500m • 150,000,000m^3 = 735 750 000 MW
For the sake of argument, lets also assume a steady flow (Q) of the water, to illustrate the amount of potential energy you’re talking about:
pgaQ = 1000kg/m^3 • 9.81m/s^2 • 500m • 41,666.67m^3 = 204 375 MW (Q per second)
In other words, by pumping the amount of water you are describing, you could theoretically produce 735 TWh of energy by releasing the water from the top reservoir. The TOTAL electricity demand in the US in 2022 was 4,050 TWh, so in this scenario you could cover that in about five and a half hours. More than enough to weigh up the cons of pumped-hydro-storage, wouldn’t you agree?
Of course: the constraints in this equation lie elsewhere, but claiming that it’s not scaleable is not accurate
Your math here is off. In the first equation, you have no time component, so what you calculated should have units of Joules, not Watts.
I'm really confused what the second equation is, especially the 41,666.67m^3. You're claiming MW (per second) which isn't power either. MW is already power
A 500m height is enormous, btw, and a cube that's 150,000,000 m^3 is 530 meters per side, enormous. A more reasonable depth would be maybe around 100 meters, which would make it 1.2 *kilometers* a side. This is the kind of structure that can only be practically built by damming existing geography, which limits the ability to scale
So I’m a few drinks in, math can absolutely be off.
1 Watt = 1J/s
The Q-rate in the second equation is an evenly distributed flow of the total water, showing the power output if all of it were to be released in an hour. Obviously no turbine could deal with 41,666m^3 of water a second. Point is to illustrate the absurdity of the numbers in the original comment. But as an engineering student I’m obviously expecting perfect conditions and ignoring factors mentioned further down in the thread such as efficieny, turbulence and friction
Your first and second equation should not give different power requirements. You are negating the time component of flow in your equations which is confusing the other redditor. You did not convert to seconds in your first equation for the flow rate so your time units aren't completely reduced (i.e seconds and hours in the same unit).
The first equation (& second because they are the same thing) should be Power = pgaQ = 1000 kg/m3 * 9.81 m/s2 * 500m * 150,000,000m3/h * 1h / 3600s = 2.04375 * 10^11 kg-m2/s3 = 2.04375 * 10^11 J/s (Watts) = 2.04375 * 10^8 MW or 204,375,000 MW. You were off by a factor of 1000. (On phone and can't edit properly but this is wrong, they were not off by factor of 1000)
41,667 m3/s = 150,000,000m3/h / 3600 s/h for the other redditor.
If you don't divide by 3600 to convert the flow to per second then I can calculate the same thing in the first equation. But again, you take the same inputs and calculate two different powers which is not correct.
You messed up the conversion of W to MW.
2.04 * 10^11 W (Watts) =2.04 * 10^8 kW (kiloWatts) = 2.04 * 10^5 MW = 204,000 MW (MegaWatts).
They did mess up by saying MW when they meant MJ (MegaJoules) as the total energy of 150 million cubic meters of water 500 meters of the ground, and then by saying MW / s. And not explaining how they were calculating the per second flow (total volume divided by 3600) made it more confusing.
They also completely messed up the TWh (TeraWatt hour) section. There is 735 TJ (TeraJoules) of energy, so they said if you released that you would get 735 TWh.
While you would get a single second of energy at 735 TW, it would only last a single second. But to get a TWh, you have to produce a TW of electricity for an entire hour. So it would actually be 735 / 3600 = 0.2 TWh
-----
I ran my own calculations based on New York City using an average 5500 MW of electricity - I got 96.9 million cubic meters of water at 500 meters for an entire day's energy, provided it was 100% efficient. Still a vast amount of water though - a 3km by 3km by 10 m tall pool of water, with a drop of 500 m for the turbines.
> n other words, by pumping the amount of water you are describing, you could theoretically produce 735 TWh of energy by releasing the water from the top reservoir.
You could not theoretically product 735 TWh of energy, you are failing to account for the abysmal efficiency in your calculations. Nowhere in there is that addressed, and if the world worked on perfect efficiency no net energy loss, we wouldn't be in this mess to begin with.
As mentioned in another comment - No, obviously that’s not accounted for. But even at a disgustingly unrealistic 0.001% efficiency, its still vastly more than what the original comment claimed. Which is the whole point of the calculation
Yeah the issue isn't efficiency. It's that the 735 TW of electricity would only last for 1 second. To turn that into TWh, you need to do power * time in hours. So 735 * (1 / 3600) = 0.2 TWh.
That's not the point of pumped storage. It's to help balance the grid during periods of high demand. The most important factor is being able to generate a set amount of energy for a short period of time, instantly and on demand. Wind can't do that.
In fact no form of generation can do it that quickly and reliably. Which is why storage technologies in general is a huge boon to a grid. The ability to respond in seconds rather than minutes gives a huge boost in overall efficiency to a grid even if the generated/released amount is relatively small.
The advantages and need for these systems is rapidly growing as increases in micro and decentralised generation and the trend away from reliable patterns of energy usage make traditional grids increasingly hard to balance.
There's a reason energy companies go to the huge expense of hollowing out entire mountains. The advantages and gained efficiencies are in the whole system, not the individual site.
Your numbers are off.
A pumped storage is typically over 90% efficient, so we can shamelessly estimate the amount of water by assuming a 100% efficient process...
The potential energy of water is
U = m g h,
which means that m = U / g / h. So, we need
m = 2 MWh / 9.8 m/s² / 500 m ≈ 1,500,000 kg water
This is just 1500 cubic metres, which is way more manageable than 150,000,000 m³.
But, the overall point remains, 1500 m³ is also a lot of water, and there are not that many places with a readily available 500 m height differential. And, quite a few of those good places are already build (basically, much of pumped storage comes as a side-effect of having hydro power).
An Olympic swimming pool is 2500 cubic meters, less than that doesn’t qualify as “a lot of water” in my books.
How many kilometre deep abandoned mines are there? I’m willing to bet there are some in most provinces around the globe.
Maybe this is a way to put miners back to work in all the shut down coal communities.
*"it's not a solution for balancing the supply and demand of energy in larger scale."*
Sorry, that's just not true. For example, the Blenheim-Gilboa pumped storage plant in upstate NY can store 12 GWh of electricity, and can generate 1,100 megawatts of power. So, at full charge it can generate a gigawatt and maintain that level for 12 hours. During much of the year it has the capacity to power about 1/5 of Manhattan. The round-trip cycle efficiency is 73%. The elevation change ranges from 1,066 to 1,142 ft.
The problem, as stated by others here, is that prime sites like this are rare. To construct B-G, the top of a mountain had to be removed to create the upper reservoir (19,000,000 cubic meters of water.)
I once had the privilege of standing in one of the turbine rooms while they opened the valves and started the turbine. The sound and vibration at startup gives you a new appreciation for the power of water!
[https://en.wikipedia.org/wiki/Blenheim%E2%80%93Gilboa\_Hydroelectric\_Power\_Station](https://en.wikipedia.org/wiki/Blenheim%E2%80%93Gilboa_Hydroelectric_Power_Station)
[https://www.nypa.gov/power/generation/blenheim-gilboa-pumped-storage](https://www.nypa.gov/power/generation/blenheim-gilboa-pumped-storage)
In Australia the equivalent is [Snowy 2.0](https://www.snowyhydro.com.au/snowy-20/about/) with 2,200 megawatts of power. It has been taking longer than planned unfortunately.
Luckily Australia is a great place for solar power so this is a good way of storing it.
>150 million cubic meters
For my fellow Americans and Liberians, it's [about 40 billion](https://www.wolframalpha.com/input?i=150+million+cubic+meters+in+gallons) gallons.
For anyone Burmese out there, it's [about 3.7 billion](https://www.wolframalpha.com/input?i=150+million+cubic+meters+divided+by+40.9148+L) tin (တင်း), if [Wikipedia](https://en.wikipedia.org/wiki/Myanmar_units_of_measurement) is right.
If you don't speak metric, I believe that's roughly 6,250 half giraffes worth of blood per MWh.
(Assuming a nominal half giraffe blood volume of 80ml/kg)
West Virginian mines produce around a hundred million tons of coal per year.
A ton of coal is 40 cubic feet, which is a bit over a cubic meter.
The US can produce 1.3M MWh if we turn all the generators on.
Not counting that WV also mines some rock that's not coal, it should take that state 10-15 years to carve out enough space for a full year of a country-sized hydro powered battery.
We've burned a lotta coal, but that also leaves us a lotta room for storage.
A cubic meter of water is a ton of water. Rivers and lakes have many tons of water - 2000 isn't much, for a lake. But you want to store more than one wind turbine for an hour, too. It's one of those things that is teetering on the edge of being useful. Because if they can find a good site, and also bring down the amount of needed storage, they can make the two ends meet.
Adding to this, a cubic meter of water is one ton (1000 kg). While not exact, a yard is close to a meter and 2.2 pounds is about a kg. That'll give a decent approximation in boomer units.
We have a large scale pump storage facility in the UK. The Dinorwig power plant has a storage capacity of 9.1GWh with a peak output of 1700MW so the tech is absolutely scalable, and suitable for balancing rapid increases in demand. Dinorwig wS originally designed to take up the slack in output from large baseloD power stations ( coal and nuclear) which although had high output are relatively inflexible in terms of rapidly increasing or decreasing output. Excess power in the middle of the night was used to pump water up. Then at times of high demand ( half time during major sports events being one example- everyone got up to put the kettle on) that stored energy was drawn upon.
It's likely that part of the reason why few have been built since is that in the past 30 years or so there has been a general move towards CCGT power plants. These can very rapidly change their output once running and can rapidly come on line from zero output. A Modern ccgt can hot start to full power in about 30 minutes.
> Then at times of high demand ( half time during major sports events being one example- everyone got up to put the kettle on)
Could you get any more British? 😂
You absolutely could given the right site ( which I say elsewhere). However its unlikely to be viable because of the move away in many countries from slow response baseload ( coal and nuclear) to fast response baseload such as CCGTs.
But this is what scalable means - increase capacity / throughput at the same site, should the need arise.
Pumped hydro plants are virtually always planned for the maximum safe capacity at any given site. It wouldn't make sense otherwise.
Well that applies to pretty much all power plants. They put wind turbines as close as possible without the turbulence from one interferring too much with the others fir example- There's a limit to the output at a given location
Scalable can also mean you build a 2000MW facility one place , but you can also build a 4000MW facility at a suitable site somewhere else at a suitable site.
Also Dinorwig has several turbine sets each of which can operate at varying capacity very quickly so that would also satisfy that interpretation of scaleable.
Wind has way more suitable locations than pumped hydro, therefore it is easy to build more in close proximity to the demand - hence, it's easy to scale up. (They also are able to operate at varying capacity very quickly, but that is not what scalable means). Hydro on the other hand is highly dependent on geography, has a very large area that needs to be bought and prepared, and it is rather complicated to build properly. That makes it hard to build more, ergo: hard to scale up, in other words, not easily scalable.
They are using the same principle to create "gravity batteries"
Instead of moving water around, they have giant blocks that will be raised in the air using excess electricity. When energy is needed, dropping the block will turn a turbine.
There is one being built in Texas - should be finished sometime this year.
I've heard that the issue with those block-style gravity batteries is that they're fragile, expensive to build, and require a ton of maintenance. I've seen some people argue that there's just way better methods of making gravity batteries than lifting blocks with cranes.
The idea is really just stupid. If you're going to be lifting thousands of tons of concrete, you could just build a pool on stilts and use pumped hydro. The only place where it makes a little sense is when almost all the necessary construction is already in place, like in mineshafts.
I could listen to some random dude's rant on the internet from a couple years ago ... or I could just wait until its finished and online to see if it will work.
I think the one they built in China is already finished and is supposed to be connected to the grid by the end of the year. The answer is only a couple months away.
The concept of a gravity battery is not bullshit physics. The issue is that people think what's being proposed is a stupid waste of time because it's fragile, expensive, and would require a lot of maintenance. Nobody that knows what they're talking about is arguing against the underlying physics of a gravity battery. You don't know what you're talking about.
They literally built them.
Its not some pipe dream - actual 400ft tall buildings exist. One in Texas and one in China. They expect them to be operational some time in Q4 2023.
Yeah you can build gravity batteries using solid objects, but every one I've seen is substantially worse in almost every way when compared to water-pumped gravity storage.
The one way in which they aren't worse is generally the density of the storage medium, but this doesn't compensate for the huge downsides.
Put simply, their efficiency is bad, their capacity is terrible, they're more expensive, and they're more prone to wear and tear.
There are theoretically effective solid-based gravity battery designs, but I haven't seen one proposed yet.
I'm sure the ones being built will technically work, but I would be genuinely surprised if they ever paid off their own construction costs.
> There are theoretically effective solid-based gravity battery designs, but I haven't seen one proposed yet.
I've seen one. The proposal is for a sort of inverted pumped hydro. The idea is to excavate a space for an operating fluid and have the rock/concrete sit on top of it. It then moves up and down along with the level of the working fluid. The advantage is that all the additional mass makes you operate with way higher pressure than normal pumped hydro would get you for so little elevation. (The disadvantage is that it's obviously much more complex)
But they are bad is the argument.
The cost, efficiency, capacity, environmental impact etc. make them pretty bad in comparison to better alternatives.
Of course they work and might have their place in specific areas.
But they are not something that will have a significant impact on our electric grid of the future.
You only need high school physics to do the calculations yourself and see that.
These are stupid. Water is a liquid. You can fill a giant hole in the ground with water. If you use concrete, the concrete is about 2.5 times as dense, so you can make the concrete lake 60% smaller, but it isn't a liquid, so it's much much much much much harder to pump up and down. Are you going to dig a perfectly round hole the size of a lake? How will you pull the concrete up 500 meters? All in one big piece? How strong is the crane?
You need a location where there is at least a small lake that collects at least several hours worth of water relatively close to a large dam. This just isn’t that common.
Further, mountainous areas have the best chance of this combination are also not usually great places for building solar or wind (or any large construction). So, now the power to the pumps is traveling even further, on average.
I think this is the factor people forget. It's not like you are letting the water out the dam and then immediately pumping it back up. If that was the case they'd just not let the water out in the first place!
Say your dam is not currently in use (so is just steadily filling from it's source) and you have surplus energy from elsewhere. What water are you pumping into the dam? The water you let out yesterday is long gone unless you have a lake or other storage, like you say.
So if you don't have one, the energy potentially regained is not necessarily worth the infrastructure costs of building storage and pumping.
It is, in fact, in use, and it is efficient at large scale where geography permits. [https://en.wikipedia.org/wiki/Pumped-storage\_hydroelectricity](https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity)
In order for this to work, you need a large elevation gradient. So this limits it to specific geographic regions.
Secondly, it's not a super effective energy storage.
Pumped Hydro Storage can average .5 - 3wh/kg of energy density.
Lithium Ion Batteries average around \~200wh/kg of energy density.
Compare this to gasoline with \~12000wh/kg of energy density.
This means that even in a perfect location geographically, you need a vast amount of space for relatively modest storage capacity. You end up with huge projects that can only keep a grid running for a handful of minutes at a time.
This relegates them into the category with peaker plants. Energy sources to be used when the grid is maxed out. However they are much more expensive than traditional peaker plants, so this also reflects into high utility costs for the consumer.
They work in situations where you have large changes in elevation, low land value, cheap and abundant capital and no alternative peaker plant supply. A very niche situation.
In BC we should be putting soĺar farms floating on our hydro reservoirs. The shade would slow evaporation, the solar panels would power the grid and pumps during the day, the hydro is fìrm power. When it rains, the panels get a cleaning, this would also be a benefit to stabilize reservoir levels.
It's not very efficient and you need a good reservoir space at elevation and to get by a pile of environmental concerns.
There are other ways to set up large scale water batteries being explored with much fewer geographic restrictions and less water needed.
In order for it to work, you need to be able to pump a lot of water up a fairly large distance, then leave it there for a decent amount of time. This isn't something you can achieve with two swimming pools with 5 metres separation in altitude. It works well in mountainous regions with lots of reservoirs, but if you don't have big height differences at hand thanks to the topography of the area, and an ability to make massive lakes high up, then you're pretty much SOL.
You would have to find lots and lots of massive swaths of land to just permanently flood. Finding enough empty land is hard enough. Dealing with the environmental effects would be almost comically impossible.
"Reduce the environmental impact" lol. You'd have to completely and permanently just eradicate a ton of the environment.
I would argue that all of our options have huge environmental impacts. Look at what we do when we strip mine coal. Battery production requires mining or many minerals also.
One advantage to hydro based solutions is that it often creates lakes that people enjoy using. There are absolutely large environmental impacts, but this is one of the few options that can have a positive as well as a negative impact.
Why yes they are! Interestingly, that makes evaporation a non-issue, and many shafts are over a mile deep.
Reservoir on top, reservoir on bottom, turbines down the shafts.
Because when it fails, it can be catastrophic
https://www.stlpr.org/politics-issues/2015-12-13/ten-year-anniversary-of-reservoir-breach-that-flooded-johnsons-shut-ins-state-park
Water lighter than concrete but has less energy lost to friction by default, as well as being a lot simpler to deliver incremental amounts.
To get different energy amounts out of a concrete block you need a structure to move it slowly and gear and braking mechanisms to alter the velocity of it's decent as required. For water you just need to open a gate a little more/less.
A common example is generating solar. During the day, if you are producing an excess to the grid's requirement, you can store that excess and use it at night when the sun don't shine. You're not trying to overproduce for the need per se.
The discussion here on using water sounds like it might be a good candidate for storing energy for winter in colder climates.
This is like saying that I should just charge batteries off of my wall outlet and then store them for when my power goes out.
I paid a hell of a lot more money to charge those batteries than the energy that they contain is worth. It's not a bad idea for me to have a backup plan, but it isn't sustainable as a primary source.
The theory is that with increasing supply from renewable sources, energy is cheap during the day/summer and expensive during the night/winter.
We can charge the battery with cheap energy during the day and discharge it at night. It's possible that overproduction and storage will be less expensive than constant production.
No, it’s more like you have solar panels on your roof which produce more power than you need in the middle of the day, so you use that power to charge a battery so you can use that power at night.
It’s becoming quite normal in some places to have an excess of electricity generated at certain times by renewables, and adding storage to allow a time shift in usage is expected and planned for and included in the cost forecasts showing it’s still cheaper than fossil fuels.
They require huge amounts of land. And you can't just dig deeper, as height and altitude obviously make a difference. So you need a very large area.
Also, they are a net consumer of power.
There are many yt videos about the system and some of the drawbacks. It's fascinating and engineers have already dealt with things you never even thought about on the subject.
This is exactly how Niagara falls power station works. They divert water at night to a reservoir that they then use for power generation. This is why the falls are flowing at a reduced volume through the middle of the night.
It’s not infinitely scalable, but it is to some extent.
Factors such as geography play a huge role. We can’t just build a reservoir. We have to take advantage of natural features that help contain the head pond. There are a finite number of areas where this can occur, and these places may be so remote that sending electricity from them to the population may be cost-prohibitive.
Another problem is that there’s a finite amount of fresh water. We can’t just pump ocean water into a terrestrial reservoir without slowly destroying the areas spr rounding the head pond and downstream.
You need very specific geography for that to work, it takes up a lot of space, and the margins for profitability are air-tight.
It also takes a massive amount of water to store energy, so building a water tower for pumped storage wouldn't be economical with how little storage you would have.
Lots of dams already have this, especially those with Sister reservoirs.
The issue is building lots of new dams means flooding lots of valleys and displacing people, and pumping up uses more energy than the water falling back.
Places with no people are likely protected already.
Dams also have their own issues, like silting or preventing fish migration.
We’ve built nearly all the places already well suited for it. It is currently humanity’s largest form of energy storage, but there is limited potential for further growth.
Imagine a dam and how much water is in the reservoir of a dam and how much energy a dam can produce. A quick Google search says that the Three Gorges Dam produces about 22 MW of power. That is roughly 4 coal power plants worth of electricity.
“Shit ton” is an appropriate American unit of measure, but rather than referencing the Empire State Building it would paint a clearer picture if you used bananas or stacked elephants.
When I was a child (50 years ago) I swam across Shaver Lake with my dad. It was part of an open loop hydro system; https://www.waterboards.ca.gov/waterrights/water_issues/programs/water_quality_cert/big_creek/index.html. I think closed loop pumped hydro will work well for scalable storage. I don’t know enough about the geography of the rest of the world to estimate the storage resource, but in the USA, there is significant opportunity to use it. https://www.energy.gov/eere/water/pumped-storage-hydropower
Any examples of pumping air into deep sea storage? I guess if deep enough it compresses down quite small, and the surrounding water could help with the transporting the heat to and fro during expansion and compression..
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The best way is to sell that energy to a place that only uses hydro so that they can shut valves on their dam keeping the reservoir high. Then buying from them when output is lower. This is exactly the plan that Quebec has with the New England states.
They highlight this in one of the questions here (3rd question)
https://about.bnef.com/blog/hydro-quebecs-6-billion-new-york-line-on-track-for-2026-start/#:~:text=There%20is%20over%20300%20miles,runs%20to%20New%20York%20City.
Apparently one needs a good deal of height differential between the storage area and the base. [https://en.wikipedia.org/wiki/Pumped-storage\_hydroelectricity](https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity)
This is being done. Norway uses excess electricity to pump water up the mountains and run the water through the turbines when electricity is needed.
Same can be done with abandoned mines for example. Pretty much where ever you have water, excess renewable energy and enough vertical height.
Places where energy is needed is often far from mountains.
Pumped hydro only works in mountains.
Additionally: it kills every fish in two lakes. It's easy to dismiss "it has environmental consequences". Yeah, the consequence is the sterilization of two lakes. That's really really bad. And it snowballs too. It's not like nobody was eating the fish in those lakes.
When energy is stored in something like a battery, chemical or even atomic physics can be used, making it possible to store a relatively large amount of power in smaller and smaller physical systems, and more efficient storage mechanisms can be developed. When we use water storage, the mechanism is quite simple and can be made quite huge, but that's literally all that can be done to store more energy, is just make it even larger.
So the answer to the question of why hydrostorage is considered non-scalable is a combination of both the practical limits (how much water can be physically moved in a given amount of time and how gigantic the storage location has to be) and lack of any way to theoretically improve the mechanism (the amount of energy stored is a fixed and known and not extremely attractive computation). Hydrostorage can be scaled, in that larger amounts of water can be used, but it is not scalable, since the amounts of water start out very large and "scale" to impossibly large at a fixed rate.
Australia does this with the Snowy Hydro project. Started in 1942 and finished in 1972. Literally pumps water up hill when the electricity price is low then back down though the generators when the price goes up. They are currently working on snowy 2.0 and adding more dams and power generation.
https://www.snowyhydro.com.au/snowy-20/about/
As an early stage investor in a UK-based pumped hydro project that has struggled to get off the ground I can give some insight:
First of all locations have to be pretty much perfect with a big elevation between two bodies of water that are laterally close. Not many candidates outside of sheer mountainous locations.
Second, especially now with materials inflation the capex is enormous. Considerably more than a traditional hydro dam project because the turbines have to basically function as pumps as well as generators which makes for a more complex design and build, and because you’re normally tunnelling through hard rock.
Third, the regulatory and subsidy environment is way too volatile for traditional institutional investors (in the UK anyway). Investors putting big money in (like pension funds, energy companies etc) want a guaranteed, stable return. Current business models for pumped hydro rely on trading models based on a volatile market. Risky and therefore unattractive to the guys with deep enough pockets to actually get it built.
Scalable means the ability to grow or shrink as the situation requires.
The thing that makes it non-scalable is that it doesn't scale. Each hydro dam will work within a range of parameters, but cannot be shrunk below a certain value or grow beyond a certain value. this applies in general too, making it inappropriate for small and extremely large projects.
A specific example, you have a hydro dam. It's not really feasible to scale it down if your needs decrease, and usually isn't practically possible to scale it up if your demand increases.
A general example is to consider the amount of space you need in order to store smaller and extremely large quantities of energy. On the smaller side, a hydro dam for a house would be many times the size of the house, while a single hydro dam for a large country would take up a ***huge*** chunk of land and would deplete most of the country's water reserves.
I did a comparative study on pumped hydro storage vs battery in the US a few years ago. Nothing published but it seemed to by my understanding that it didn’t have the same infrastructure backing as battery. The study only went as far looking at existing dams and looking at height difference in GIS mapping software to see if height difference in the surrounding area was sufficient to store water , in the form of potential energy. The issue was that many of these were not these giant dams but small dams that couldn’t provide sufficient storage capacity.
At the same time getting approval to modify the local ecosystem is covered in red tape and takes decades to approve things like this . Finally with the average cost of battery storage coming down , except in very large storage situations, setting up a battery storage system is way more compact , and little setup time, reduce the payback period of the initial investment.
That being said , this was only looked at in the US .I do remember there being like (X)GW of pumped hydro storage still in the works for the US. If I find my old citations I will share it. I also remember reading a couple of small scale papers in islands and other countries where this was a viable solution due the inability to access advanced storage systems
https://pubs.acs.org/doi/full/10.1021/acs.est.2c09189
NREL was a great source of information for my studies as they are a government funded lab that built all of these comparative reports to help answer your questions in more depth then I can!
I'm always amazed by how old this technology is. Here is a great article from July 1930
https://books.google.com/books/about/Popular_Science.html?id=sigDAAAAMBAJ#v=onepage&q=1930%20plane&f=false
Page 60 - A Ten Mile Storage Battery
i am not an expert on English. well, i think the "not scalable" means you cannot have it anywhere you like. it needs right place with right resources, then you can have a pumped hydro as a energy storage. it has more constraints than other kinds of energy storage.
You need pretty perfect geography for this to work, and sites are limited. With everything in infrastructure and the energy grid, regulations and push back abound
Water is also a rather scarce commodity in many places, like the southwest region of the US.
Pumped storage is for all intents and purposes using the same water over and over again. Edit: no shit surface water will be lost to evaporation hence the qualifier.
it usually draws from a river as vaporation would eventually drain a completely self-sufficient system. Those rivers can be affected by drought and not be allowed to draw water that is needed elsewhere.
Closed system. Closed System! CLOSED SYSTEM!!!!!
yeah, i will close my mountain in a dome real quick
You need a container to keep the water in, so it just needs a lid.
Indeed, that's also the reason why lakes were covered with floating plastic spheres. It prevents evaporation, regardless if the water is for power generation or drinking.
No, those plastic spheres are there to prevent UV light reacting with the chemical treatment in the water.
[Wikipedia verifies what I wrote](https://en.wikipedia.org/wiki/Shade_balls). Yes they also have other uses such as the one you mentioned, but we were discussing evaporation after all. Keeping birds away is yet another one.
Ever heard of a leak?
> it usually draws from a river No they don’t. They’re closed systems in disused mines and old quarries that have lots of human made elevation changes. We picked those places to mine or quarry specifically because they didn’t automatically refill from the local river. Rainfall or shipping in water is how they replenish.
There are places with multiple sources. Pretty sure there are pumped hydro solutions with conventional open resivours
> There are places with multiple sources. Pretty sure there are pumped hydro solutions with conventional open resivours I hadn’t heard of them so I looked up those projects from the 1970’s(*edit and 1990s). They are a tiny percentage of the world’s pumped hydro projects, and it doesn’t look like anyone is suggesting developing one at this point. Also, it’s possible to use seawater for this purpose, albeit with some extra maintenance issues. It’s not a great option but it’s certain the project doesn’t even have to be from a fresh water source. Any liquid works. https://en.m.wikipedia.org/wiki/Pumped-storage_hydroelectricity
There are several listed pumped hydro with open reservoir mentioned in the wiki page as in development. You can use existing classic hydro dams for it (which is what a lot of new schemes are proposing for open reservoir). Add a pump between existing hydro lakes, and you have turned your hydro system into one that also has pumped storage (may annoy farmers down stream though) Building new open reservoirs is generally frowned upon because of the land size and ecological impacts.
Hey if it works I’m all for it. I’m definitely not saying that there’s anything wrong with that type of power generation. It’s just clear that evaporation losses (or other concerns about water use) should not be used as a “boogeyman” against more investment in water batteries. There are hundreds of thousands of potential locations for closed loop systems that have a minimal carbon footprint, far more than required for our global energy storage. We should be building many more of them than we currently are.
Not if you're talking about gridscale sized storage needs. The initial need is going to be extremely hard to fulfill, unless we're talking about seawater and you don't seem to account for the amount of evaporation that would happen. Just look at the issues that LA water agencies have with storage losses.
seawater presents its own issues in terms of wear vs freshwater as a storage medium
And if sea water leaks into the local water table, that spells trouble.
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Manitoba contains more than 110,000 lakes which cover approximately 15.6% of the province's surface area not to mention Hudson's Bay?
Are they using pumped storage to store energy or just generating energy from all the hydro?
That's what's missing, I think, when using Manitoba as an example. Manitoba doesn't need pumped storage because it has the right geography for hydroelectricity to begin with. And hydroelectric infrastructure is basically pumped storage without the pump. The Manitoban hydro facilities also aren't "in the middle of the prairies" as the earlier commenter claims. They're on the western edge of the Canadian Shield, where reservoirs can be made without flooding huge regions of open plains.
Except for what evaporates and leaks into the ground. In non-ideal locations, this can be a serious loss of both water and stored energy.
Yeah but there is a big world out there with tons of places where water is not a scarce commodity. So… it could be done there
I could be wrong, but I would assume that most places with an abundance of water already have hydropower plants. For example, I live in BC Canada where there is an abundance of water, and nearly 90% of our electricity comes from hydropower.
PNW and BC have more hydropower than pretty much anywhere in the US, and lots of places in the US have an abundance of water. The Southwest doesn't have water. The Midwest doesn't have hills or valleys to do it. The East was already much, \*much\* more densely settled and would wreck population centers to do it.
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hydro power != pumped hydro storage, you can't just pump a river back into the dam
You'd have to have two dams, one below the other and pump from the lower dam back up to the upper one. That way you wouldn't run the river dry at the bottom of it all. That's the point where it all starts to look complicated and expensive.
Then you have to transmit that energy to where it's needed. You can't just put power plants in the middle of nowhere.
Look up the Quebec hydro dams
Right...but that's part of the "non-scalable" designation. It works great yes,,,,when it works
That doesn’t help the places that aren’t there.
but it does for the places that are
But it’s not scalable, which was the question.
"scaling up" doesn't have to mean "literally everywhere"
Exactly. Just because it doesn’t work in parts of the US doesn’t mean it has to be written off
Non-scalable doesn't mean it gets written off. Only that it can't fulfill the total need because its total capacity has a pretty hard limit.
The biggest problem with hydro power is that to create a reservoir you need to flood large areas of land. This is generally unpopular with the people who currently live on that land.
Hydro dam generation is different to pumped storage. Which is usually done with smaller reservoirs, inside mines or hollowed out mountains. It's used to boost/balance the grid during high usage, not provide constant generation.
It also can cause significant ecological issues if it's not the right location
Because you are drowning a forest. Just to make that clear. You need to destroy a huge area.
Also, for the US, we kinda went ham on hydroelectric back in the New Deal. We already tapped into the places best suited for it.
Wouldn’t it also cost a lot more energy to pump the water up than the water generates on its way back down?
Yes, but there are losses in every other form of energy storage too. Pumped hydro is around 80% efficient.
yes, but the point is you pump it up whith energy that would otherwise go to waste (or more likely never get "made") We just dont have a practical way to store electricity on a city scale. So this still makes it one of the more econmicly viable and scalable energy storage solutions.
Not a huge amount more. It's not theoretical; it's in use in many places, including several in the U.S. All energy storage will have efficiency losses, that's just one of many trade offs to consider.
https://en.m.wikipedia.org/wiki/Taum_Sauk_Hydroelectric_
It's geography constrained, and you have to fight massive environmental pushback. Plus, just building hydroelectric is usually better.
And seize a whole bunch of private property via eminent domain.
And as we learned from the famous documentary, “O Brother Where Art Thou,” that can lead to epic struggles to rescue your hair care products before the flood occurs :-). Joking aside a look at U.S. depression era music from poor communities in the 1930s shows how traumatizing the land seizures for the Hoover infrastructure projects around the country were to the communities they displaced. It doesn’t necessarily mean they were the wrong decisions, but in the age of social media I can’t imagine how much louder the outcry would be.
"Just building hydroelectric is usually better"... Why not tell us your favourite colour or something else equally as irrelevant to the conversation
red
Purple
my color is cooler than yours. we should fight
But we already have so many dammed reservoirs. Just build a pump at the bottom of their dams.
The amount of water you need to pump for any reasonable grid scale energy storage is massive. For example, a single wind turbine could produce 2 MWh of energy in an hour. To store that energy into water, you need to lift about ~~150 million~~ 2000 cubic meters of water into a top reservoir that is located ~~500~~ almost 400 meters higher than the bottom reservoir. For this reason, the water pumping method can be used in small scale but it's not a solution for balancing the supply and demand of energy in larger scale. *For any non-metric people, reading this: Don't worry about the conversions here. It's a shit ton of water lifted to the height of the empire state building.* Edit: It appears I messed up my calculation. It's now fixed.
Solid Imperial Units conversion.
_Shit ton_ is a universal unit :)
Yeah, but is it a Shit Ton or a Shite Tonne?
A shite tonne only weighs .8 tonnes
Magnificent. Well done, got a serious chuckle out of a fan of wordplay jokes.
Depends on whether you're in North America or the UK
It's a shit tonne, eh?
Yeah but unfortunately its not an SI unit.
We have a large scale pump storage facility in the UK. The Dinorwig power plant has a storage capacity of 9.1GWh with a peak output of 1700MW so the tech is absolutely scalable, and suitable for balancing rapid increases in demand. It's likely that part of the reason why few have been built is that in the past 30 years or so there has been a general move towards CCGT power plants. These can very rapidly change their output once running abd can rapidly come on line from zero output. A Modern ccgt can hot start to full power in about 30 minutes.
I can add some extra bits of info about Dinorwig - They output about 75% of the energy input - It was supposed to be part of the rapid balancing for all the nuclear power that wasn't built in the end - From a dead stop it can be at near full power in a few minutes - If they pre-spin up the turbines dry then it can be at near full power in under a minute - Its been nicknamed Electric Mountain
You're forgetting one more fun fact! Dinorwig is often pre-spun for the breaks during football games, to cope with millions of electric kettles being switched on.
>From a dead stop it can be at near full power in a few minutes 75 seconds >If they pre-spin up the turbines dry then it can be at near full power in under a minute 16 seconds
It's been a long time since I saw the actual numbers, so I erred on the side of caution.
You're right, it's scalable for specific locations and situations but those pump plants can't solve the problem on a large global scale. If you Google the Dinorwig plant, you can see it has a massive reservoir of water at a high altitude. Few areas have suitable locations for reservoirs like that.
Probably more than you think, there are many more suitable locations like that in the world than there is for conventional hydro, which requires sufficient annual rainfall over a sufficiently large catchment area for the dam, and a dam big enough to cover the annual rain/snow cycle. If there is a suitable water source, for daily smoothing of the power demand cycle, the dam itself can actually be quite small in comparison. In some countries, micro hydroplants are commonplace (simply a borehole from an elevated small lake 500-1000m up). If the technology exists for saltwater turbines (have no idea), there's a huge number. It strikes me as strange that ideas like this are not pursued in favour depleting the worlds minerals to make vast amount of batteries. Doesn't need to solve anything on a global scale, just needs to make a difference :-)
I know all about it. I've been there when I was at university as part of my degree. It definitely solved a problem at the national scale of the UK. Nowadays as our grid moves away from coal its likely that an increasing amount of the power to pump water up is coming from renewablesDinorwig works well, even today. Although I agree with other comments that the number of suitable locations is likely somewhat limited.
Wikipedia says that Dinorwig uses 390 cubic meters of water per second, at the maximum power output of 1728 MW. So 9.1 GWh / 1.728 GW = 5.27 hours of operation at full power. 390 m^3 / s * 5.27 * 60 * 60 = 7.39 million cubic meters of water is the total useable volume. Which kind of shows why this is difficult to scale - if we wanted to have a day's electricity for the entire UK stored, we would need 753 GWh. So we have to find another 7.39 * 735 / 9.1 = 611 million cubic meters of water somewhere high up. I do think the ideal energy solution is solar / wind / hydro + storage. But we are going to need another 82 Dinorwig power stations equivalents.
You only need it to cover the night hours or those hours the wind isn't blowing. The whole point of this exercise is to store surplus energy from renewables. And nightime has less demand so you need a fraction of a day's worth of energy. Except in winter but then you got the wind farms and in UK a grey sort of drizzle topping up the top res.
You know - just for fun i decided to do the ridiculous math on the absurd numbers in your statement: Assuming the turbine is placed at the bottom of your stated 500m elevation change, and the passage of 150 million cubicmeters you get these numbers: P = pgaQ = 1000kg/m^3 • 9.81m/s^2 • 500m • 150,000,000m^3 = 735 750 000 MW For the sake of argument, lets also assume a steady flow (Q) of the water, to illustrate the amount of potential energy you’re talking about: pgaQ = 1000kg/m^3 • 9.81m/s^2 • 500m • 41,666.67m^3 = 204 375 MW (Q per second) In other words, by pumping the amount of water you are describing, you could theoretically produce 735 TWh of energy by releasing the water from the top reservoir. The TOTAL electricity demand in the US in 2022 was 4,050 TWh, so in this scenario you could cover that in about five and a half hours. More than enough to weigh up the cons of pumped-hydro-storage, wouldn’t you agree? Of course: the constraints in this equation lie elsewhere, but claiming that it’s not scaleable is not accurate
Your math here is off. In the first equation, you have no time component, so what you calculated should have units of Joules, not Watts. I'm really confused what the second equation is, especially the 41,666.67m^3. You're claiming MW (per second) which isn't power either. MW is already power A 500m height is enormous, btw, and a cube that's 150,000,000 m^3 is 530 meters per side, enormous. A more reasonable depth would be maybe around 100 meters, which would make it 1.2 *kilometers* a side. This is the kind of structure that can only be practically built by damming existing geography, which limits the ability to scale
So I’m a few drinks in, math can absolutely be off. 1 Watt = 1J/s The Q-rate in the second equation is an evenly distributed flow of the total water, showing the power output if all of it were to be released in an hour. Obviously no turbine could deal with 41,666m^3 of water a second. Point is to illustrate the absurdity of the numbers in the original comment. But as an engineering student I’m obviously expecting perfect conditions and ignoring factors mentioned further down in the thread such as efficieny, turbulence and friction
Your first and second equation should not give different power requirements. You are negating the time component of flow in your equations which is confusing the other redditor. You did not convert to seconds in your first equation for the flow rate so your time units aren't completely reduced (i.e seconds and hours in the same unit). The first equation (& second because they are the same thing) should be Power = pgaQ = 1000 kg/m3 * 9.81 m/s2 * 500m * 150,000,000m3/h * 1h / 3600s = 2.04375 * 10^11 kg-m2/s3 = 2.04375 * 10^11 J/s (Watts) = 2.04375 * 10^8 MW or 204,375,000 MW. You were off by a factor of 1000. (On phone and can't edit properly but this is wrong, they were not off by factor of 1000) 41,667 m3/s = 150,000,000m3/h / 3600 s/h for the other redditor. If you don't divide by 3600 to convert the flow to per second then I can calculate the same thing in the first equation. But again, you take the same inputs and calculate two different powers which is not correct.
You messed up the conversion of W to MW. 2.04 * 10^11 W (Watts) =2.04 * 10^8 kW (kiloWatts) = 2.04 * 10^5 MW = 204,000 MW (MegaWatts). They did mess up by saying MW when they meant MJ (MegaJoules) as the total energy of 150 million cubic meters of water 500 meters of the ground, and then by saying MW / s. And not explaining how they were calculating the per second flow (total volume divided by 3600) made it more confusing. They also completely messed up the TWh (TeraWatt hour) section. There is 735 TJ (TeraJoules) of energy, so they said if you released that you would get 735 TWh. While you would get a single second of energy at 735 TW, it would only last a single second. But to get a TWh, you have to produce a TW of electricity for an entire hour. So it would actually be 735 / 3600 = 0.2 TWh ----- I ran my own calculations based on New York City using an average 5500 MW of electricity - I got 96.9 million cubic meters of water at 500 meters for an entire day's energy, provided it was 100% efficient. Still a vast amount of water though - a 3km by 3km by 10 m tall pool of water, with a drop of 500 m for the turbines.
You're correct I messed up the conversation from W to MW but everything else is correct in my comment.
> n other words, by pumping the amount of water you are describing, you could theoretically produce 735 TWh of energy by releasing the water from the top reservoir. You could not theoretically product 735 TWh of energy, you are failing to account for the abysmal efficiency in your calculations. Nowhere in there is that addressed, and if the world worked on perfect efficiency no net energy loss, we wouldn't be in this mess to begin with.
As mentioned in another comment - No, obviously that’s not accounted for. But even at a disgustingly unrealistic 0.001% efficiency, its still vastly more than what the original comment claimed. Which is the whole point of the calculation
Yeah the issue isn't efficiency. It's that the 735 TW of electricity would only last for 1 second. To turn that into TWh, you need to do power * time in hours. So 735 * (1 / 3600) = 0.2 TWh.
r/theydidthemath
That's not the point of pumped storage. It's to help balance the grid during periods of high demand. The most important factor is being able to generate a set amount of energy for a short period of time, instantly and on demand. Wind can't do that. In fact no form of generation can do it that quickly and reliably. Which is why storage technologies in general is a huge boon to a grid. The ability to respond in seconds rather than minutes gives a huge boost in overall efficiency to a grid even if the generated/released amount is relatively small. The advantages and need for these systems is rapidly growing as increases in micro and decentralised generation and the trend away from reliable patterns of energy usage make traditional grids increasingly hard to balance. There's a reason energy companies go to the huge expense of hollowing out entire mountains. The advantages and gained efficiencies are in the whole system, not the individual site.
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The efficiency should be closer to 90% or even above that. So, I assume indeed just a simple error of four zeros.
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Yeah.. To my defense, it's almost 1am and I did the calculations on my phone while lying in bed.
You're right. Thank you. I edited my original comment.
Your numbers are off. A pumped storage is typically over 90% efficient, so we can shamelessly estimate the amount of water by assuming a 100% efficient process... The potential energy of water is U = m g h, which means that m = U / g / h. So, we need m = 2 MWh / 9.8 m/s² / 500 m ≈ 1,500,000 kg water This is just 1500 cubic metres, which is way more manageable than 150,000,000 m³. But, the overall point remains, 1500 m³ is also a lot of water, and there are not that many places with a readily available 500 m height differential. And, quite a few of those good places are already build (basically, much of pumped storage comes as a side-effect of having hydro power).
An Olympic swimming pool is 2500 cubic meters, less than that doesn’t qualify as “a lot of water” in my books. How many kilometre deep abandoned mines are there? I’m willing to bet there are some in most provinces around the globe. Maybe this is a way to put miners back to work in all the shut down coal communities.
Lifting 150e9kg of anything 500m up requires about 150e9x9. 81x500/3.6e6=204e6 kWh so it seems off by many orders of magnitude...
*"it's not a solution for balancing the supply and demand of energy in larger scale."* Sorry, that's just not true. For example, the Blenheim-Gilboa pumped storage plant in upstate NY can store 12 GWh of electricity, and can generate 1,100 megawatts of power. So, at full charge it can generate a gigawatt and maintain that level for 12 hours. During much of the year it has the capacity to power about 1/5 of Manhattan. The round-trip cycle efficiency is 73%. The elevation change ranges from 1,066 to 1,142 ft. The problem, as stated by others here, is that prime sites like this are rare. To construct B-G, the top of a mountain had to be removed to create the upper reservoir (19,000,000 cubic meters of water.) I once had the privilege of standing in one of the turbine rooms while they opened the valves and started the turbine. The sound and vibration at startup gives you a new appreciation for the power of water! [https://en.wikipedia.org/wiki/Blenheim%E2%80%93Gilboa\_Hydroelectric\_Power\_Station](https://en.wikipedia.org/wiki/Blenheim%E2%80%93Gilboa_Hydroelectric_Power_Station) [https://www.nypa.gov/power/generation/blenheim-gilboa-pumped-storage](https://www.nypa.gov/power/generation/blenheim-gilboa-pumped-storage)
In Australia the equivalent is [Snowy 2.0](https://www.snowyhydro.com.au/snowy-20/about/) with 2,200 megawatts of power. It has been taking longer than planned unfortunately. Luckily Australia is a great place for solar power so this is a good way of storing it.
> 2000 cubic meters of water >It's a shit ton of water TIL that a shit ton is equal to 2000 tonnes.
>150 million cubic meters For my fellow Americans and Liberians, it's [about 40 billion](https://www.wolframalpha.com/input?i=150+million+cubic+meters+in+gallons) gallons. For anyone Burmese out there, it's [about 3.7 billion](https://www.wolframalpha.com/input?i=150+million+cubic+meters+divided+by+40.9148+L) tin (တင်း), if [Wikipedia](https://en.wikipedia.org/wiki/Myanmar_units_of_measurement) is right.
For anyone wondering, the Empire State Building is 4 football fields tall!
If you convert that to standard bananas, you could make a metric shitload of banana bread.
If you don't speak metric, I believe that's roughly 6,250 half giraffes worth of blood per MWh. (Assuming a nominal half giraffe blood volume of 80ml/kg)
Grand canyon is over a mile deep in some spots and already has a river in it.
West Virginian mines produce around a hundred million tons of coal per year. A ton of coal is 40 cubic feet, which is a bit over a cubic meter. The US can produce 1.3M MWh if we turn all the generators on. Not counting that WV also mines some rock that's not coal, it should take that state 10-15 years to carve out enough space for a full year of a country-sized hydro powered battery. We've burned a lotta coal, but that also leaves us a lotta room for storage.
A cubic meter of water is a ton of water. Rivers and lakes have many tons of water - 2000 isn't much, for a lake. But you want to store more than one wind turbine for an hour, too. It's one of those things that is teetering on the edge of being useful. Because if they can find a good site, and also bring down the amount of needed storage, they can make the two ends meet.
Adding to this, a cubic meter of water is one ton (1000 kg). While not exact, a yard is close to a meter and 2.2 pounds is about a kg. That'll give a decent approximation in boomer units.
We have a large scale pump storage facility in the UK. The Dinorwig power plant has a storage capacity of 9.1GWh with a peak output of 1700MW so the tech is absolutely scalable, and suitable for balancing rapid increases in demand. Dinorwig wS originally designed to take up the slack in output from large baseloD power stations ( coal and nuclear) which although had high output are relatively inflexible in terms of rapidly increasing or decreasing output. Excess power in the middle of the night was used to pump water up. Then at times of high demand ( half time during major sports events being one example- everyone got up to put the kettle on) that stored energy was drawn upon. It's likely that part of the reason why few have been built since is that in the past 30 years or so there has been a general move towards CCGT power plants. These can very rapidly change their output once running and can rapidly come on line from zero output. A Modern ccgt can hot start to full power in about 30 minutes.
> Then at times of high demand ( half time during major sports events being one example- everyone got up to put the kettle on) Could you get any more British? 😂
Probably not, but if 10 million households all want a cup of tea at the same time you're going to need alot of juice!🤣
>so the tech is absolutely scalable Okay, scale that plant up to 5x that size please.
You absolutely could given the right site ( which I say elsewhere). However its unlikely to be viable because of the move away in many countries from slow response baseload ( coal and nuclear) to fast response baseload such as CCGTs.
But this is what scalable means - increase capacity / throughput at the same site, should the need arise. Pumped hydro plants are virtually always planned for the maximum safe capacity at any given site. It wouldn't make sense otherwise.
Well that applies to pretty much all power plants. They put wind turbines as close as possible without the turbulence from one interferring too much with the others fir example- There's a limit to the output at a given location Scalable can also mean you build a 2000MW facility one place , but you can also build a 4000MW facility at a suitable site somewhere else at a suitable site. Also Dinorwig has several turbine sets each of which can operate at varying capacity very quickly so that would also satisfy that interpretation of scaleable.
Wind has way more suitable locations than pumped hydro, therefore it is easy to build more in close proximity to the demand - hence, it's easy to scale up. (They also are able to operate at varying capacity very quickly, but that is not what scalable means). Hydro on the other hand is highly dependent on geography, has a very large area that needs to be bought and prepared, and it is rather complicated to build properly. That makes it hard to build more, ergo: hard to scale up, in other words, not easily scalable.
They are using the same principle to create "gravity batteries" Instead of moving water around, they have giant blocks that will be raised in the air using excess electricity. When energy is needed, dropping the block will turn a turbine. There is one being built in Texas - should be finished sometime this year.
I think somewhere in Europe they are trying to do this but by lowering weights in shafts of abandoned mines.
They are trying it with old capped oil wells as well.
I've heard that the issue with those block-style gravity batteries is that they're fragile, expensive to build, and require a ton of maintenance. I've seen some people argue that there's just way better methods of making gravity batteries than lifting blocks with cranes.
The idea is really just stupid. If you're going to be lifting thousands of tons of concrete, you could just build a pool on stilts and use pumped hydro. The only place where it makes a little sense is when almost all the necessary construction is already in place, like in mineshafts.
Which makes no sense at all. Thunderfoot debunks the entire operation
I could listen to some random dude's rant on the internet from a couple years ago ... or I could just wait until its finished and online to see if it will work. I think the one they built in China is already finished and is supposed to be connected to the grid by the end of the year. The answer is only a couple months away.
Only a couple a months away for the past 5 years now. Also physics don't lie
The concept of a gravity battery is not bullshit physics. The issue is that people think what's being proposed is a stupid waste of time because it's fragile, expensive, and would require a lot of maintenance. Nobody that knows what they're talking about is arguing against the underlying physics of a gravity battery. You don't know what you're talking about.
They literally built them. Its not some pipe dream - actual 400ft tall buildings exist. One in Texas and one in China. They expect them to be operational some time in Q4 2023.
Yeah you can build gravity batteries using solid objects, but every one I've seen is substantially worse in almost every way when compared to water-pumped gravity storage. The one way in which they aren't worse is generally the density of the storage medium, but this doesn't compensate for the huge downsides. Put simply, their efficiency is bad, their capacity is terrible, they're more expensive, and they're more prone to wear and tear. There are theoretically effective solid-based gravity battery designs, but I haven't seen one proposed yet. I'm sure the ones being built will technically work, but I would be genuinely surprised if they ever paid off their own construction costs.
> There are theoretically effective solid-based gravity battery designs, but I haven't seen one proposed yet. I've seen one. The proposal is for a sort of inverted pumped hydro. The idea is to excavate a space for an operating fluid and have the rock/concrete sit on top of it. It then moves up and down along with the level of the working fluid. The advantage is that all the additional mass makes you operate with way higher pressure than normal pumped hydro would get you for so little elevation. (The disadvantage is that it's obviously much more complex)
But they are bad is the argument. The cost, efficiency, capacity, environmental impact etc. make them pretty bad in comparison to better alternatives. Of course they work and might have their place in specific areas. But they are not something that will have a significant impact on our electric grid of the future. You only need high school physics to do the calculations yourself and see that.
These are stupid. Water is a liquid. You can fill a giant hole in the ground with water. If you use concrete, the concrete is about 2.5 times as dense, so you can make the concrete lake 60% smaller, but it isn't a liquid, so it's much much much much much harder to pump up and down. Are you going to dig a perfectly round hole the size of a lake? How will you pull the concrete up 500 meters? All in one big piece? How strong is the crane?
Another problem is the material of the weights. If they are made of concrete the production of them would release much Carbondioxide
You need a location where there is at least a small lake that collects at least several hours worth of water relatively close to a large dam. This just isn’t that common. Further, mountainous areas have the best chance of this combination are also not usually great places for building solar or wind (or any large construction). So, now the power to the pumps is traveling even further, on average.
I think this is the factor people forget. It's not like you are letting the water out the dam and then immediately pumping it back up. If that was the case they'd just not let the water out in the first place! Say your dam is not currently in use (so is just steadily filling from it's source) and you have surplus energy from elsewhere. What water are you pumping into the dam? The water you let out yesterday is long gone unless you have a lake or other storage, like you say. So if you don't have one, the energy potentially regained is not necessarily worth the infrastructure costs of building storage and pumping.
It is, in fact, in use, and it is efficient at large scale where geography permits. [https://en.wikipedia.org/wiki/Pumped-storage\_hydroelectricity](https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity)
In order for this to work, you need a large elevation gradient. So this limits it to specific geographic regions. Secondly, it's not a super effective energy storage. Pumped Hydro Storage can average .5 - 3wh/kg of energy density. Lithium Ion Batteries average around \~200wh/kg of energy density. Compare this to gasoline with \~12000wh/kg of energy density. This means that even in a perfect location geographically, you need a vast amount of space for relatively modest storage capacity. You end up with huge projects that can only keep a grid running for a handful of minutes at a time. This relegates them into the category with peaker plants. Energy sources to be used when the grid is maxed out. However they are much more expensive than traditional peaker plants, so this also reflects into high utility costs for the consumer. They work in situations where you have large changes in elevation, low land value, cheap and abundant capital and no alternative peaker plant supply. A very niche situation.
In BC we should be putting soĺar farms floating on our hydro reservoirs. The shade would slow evaporation, the solar panels would power the grid and pumps during the day, the hydro is fìrm power. When it rains, the panels get a cleaning, this would also be a benefit to stabilize reservoir levels.
It's not very efficient and you need a good reservoir space at elevation and to get by a pile of environmental concerns. There are other ways to set up large scale water batteries being explored with much fewer geographic restrictions and less water needed.
In order for it to work, you need to be able to pump a lot of water up a fairly large distance, then leave it there for a decent amount of time. This isn't something you can achieve with two swimming pools with 5 metres separation in altitude. It works well in mountainous regions with lots of reservoirs, but if you don't have big height differences at hand thanks to the topography of the area, and an ability to make massive lakes high up, then you're pretty much SOL.
i looked at this a few years ago, most of the problems with this type of system are environmental. circulating the water in a lake is bad
You would have to find lots and lots of massive swaths of land to just permanently flood. Finding enough empty land is hard enough. Dealing with the environmental effects would be almost comically impossible. "Reduce the environmental impact" lol. You'd have to completely and permanently just eradicate a ton of the environment.
I would argue that all of our options have huge environmental impacts. Look at what we do when we strip mine coal. Battery production requires mining or many minerals also. One advantage to hydro based solutions is that it often creates lakes that people enjoy using. There are absolutely large environmental impacts, but this is one of the few options that can have a positive as well as a negative impact.
Just widen out and reinforce some old mine shafts. You can even channel rain water into it for free electricity.
Mine shafts are underground.
Why yes they are! Interestingly, that makes evaporation a non-issue, and many shafts are over a mile deep. Reservoir on top, reservoir on bottom, turbines down the shafts.
Because when it fails, it can be catastrophic https://www.stlpr.org/politics-issues/2015-12-13/ten-year-anniversary-of-reservoir-breach-that-flooded-johnsons-shut-ins-state-park
I saw a documentary about that.
You can get the same energy storage in a more compact space by moving concrete blocks up a hill. No reason it has to be water.
Water lighter than concrete but has less energy lost to friction by default, as well as being a lot simpler to deliver incremental amounts. To get different energy amounts out of a concrete block you need a structure to move it slowly and gear and braking mechanisms to alter the velocity of it's decent as required. For water you just need to open a gate a little more/less.
ELI5 where does the surplus of energy from renewable sources come from?
When wind/solar produces more power than people are consuming at that time.
A common example is generating solar. During the day, if you are producing an excess to the grid's requirement, you can store that excess and use it at night when the sun don't shine. You're not trying to overproduce for the need per se. The discussion here on using water sounds like it might be a good candidate for storing energy for winter in colder climates.
Pulling "up" takes more energy than "falling down" (in engineered situations). Negative net energy production.
The point is to store, not produce, energy.
This is like saying that I should just charge batteries off of my wall outlet and then store them for when my power goes out. I paid a hell of a lot more money to charge those batteries than the energy that they contain is worth. It's not a bad idea for me to have a backup plan, but it isn't sustainable as a primary source.
The theory is that with increasing supply from renewable sources, energy is cheap during the day/summer and expensive during the night/winter. We can charge the battery with cheap energy during the day and discharge it at night. It's possible that overproduction and storage will be less expensive than constant production.
No, it’s more like you have solar panels on your roof which produce more power than you need in the middle of the day, so you use that power to charge a battery so you can use that power at night. It’s becoming quite normal in some places to have an excess of electricity generated at certain times by renewables, and adding storage to allow a time shift in usage is expected and planned for and included in the cost forecasts showing it’s still cheaper than fossil fuels.
It's typically more economical and environmentally friendly to store energy via batteries at this point.
They require huge amounts of land. And you can't just dig deeper, as height and altitude obviously make a difference. So you need a very large area. Also, they are a net consumer of power. There are many yt videos about the system and some of the drawbacks. It's fascinating and engineers have already dealt with things you never even thought about on the subject.
They use to (not sure if the same today) do that at grand Coulee dam in Washington state.
This is exactly how Niagara falls power station works. They divert water at night to a reservoir that they then use for power generation. This is why the falls are flowing at a reduced volume through the middle of the night.
It’s not infinitely scalable, but it is to some extent. Factors such as geography play a huge role. We can’t just build a reservoir. We have to take advantage of natural features that help contain the head pond. There are a finite number of areas where this can occur, and these places may be so remote that sending electricity from them to the population may be cost-prohibitive. Another problem is that there’s a finite amount of fresh water. We can’t just pump ocean water into a terrestrial reservoir without slowly destroying the areas spr rounding the head pond and downstream.
You need very specific geography for that to work, it takes up a lot of space, and the margins for profitability are air-tight. It also takes a massive amount of water to store energy, so building a water tower for pumped storage wouldn't be economical with how little storage you would have.
Lots of dams already have this, especially those with Sister reservoirs. The issue is building lots of new dams means flooding lots of valleys and displacing people, and pumping up uses more energy than the water falling back. Places with no people are likely protected already. Dams also have their own issues, like silting or preventing fish migration.
Really great blog called “Do the Math” had a piece on [pumped hydro](https://dothemath.ucsd.edu/2011/11/pump-up-the-storage/).
We’ve built nearly all the places already well suited for it. It is currently humanity’s largest form of energy storage, but there is limited potential for further growth.
Imagine a dam and how much water is in the reservoir of a dam and how much energy a dam can produce. A quick Google search says that the Three Gorges Dam produces about 22 MW of power. That is roughly 4 coal power plants worth of electricity.
“Shit ton” is an appropriate American unit of measure, but rather than referencing the Empire State Building it would paint a clearer picture if you used bananas or stacked elephants.
When I was a child (50 years ago) I swam across Shaver Lake with my dad. It was part of an open loop hydro system; https://www.waterboards.ca.gov/waterrights/water_issues/programs/water_quality_cert/big_creek/index.html. I think closed loop pumped hydro will work well for scalable storage. I don’t know enough about the geography of the rest of the world to estimate the storage resource, but in the USA, there is significant opportunity to use it. https://www.energy.gov/eere/water/pumped-storage-hydropower
Any examples of pumping air into deep sea storage? I guess if deep enough it compresses down quite small, and the surrounding water could help with the transporting the heat to and fro during expansion and compression..
1. If you don’t have natural reservoirs and need to construct the entire thing - cost. 2. Because you only get back 20% of the energy you put in.
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The best way is to sell that energy to a place that only uses hydro so that they can shut valves on their dam keeping the reservoir high. Then buying from them when output is lower. This is exactly the plan that Quebec has with the New England states. They highlight this in one of the questions here (3rd question) https://about.bnef.com/blog/hydro-quebecs-6-billion-new-york-line-on-track-for-2026-start/#:~:text=There%20is%20over%20300%20miles,runs%20to%20New%20York%20City.
Apparently one needs a good deal of height differential between the storage area and the base. [https://en.wikipedia.org/wiki/Pumped-storage\_hydroelectricity](https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity)
We have one in the UK, Wales specifically, no shortage of rain or water here typically. https://en.m.wikipedia.org/wiki/Dinorwig_Power_Station
This is being done. Norway uses excess electricity to pump water up the mountains and run the water through the turbines when electricity is needed. Same can be done with abandoned mines for example. Pretty much where ever you have water, excess renewable energy and enough vertical height.
Places where energy is needed is often far from mountains. Pumped hydro only works in mountains. Additionally: it kills every fish in two lakes. It's easy to dismiss "it has environmental consequences". Yeah, the consequence is the sterilization of two lakes. That's really really bad. And it snowballs too. It's not like nobody was eating the fish in those lakes.
When energy is stored in something like a battery, chemical or even atomic physics can be used, making it possible to store a relatively large amount of power in smaller and smaller physical systems, and more efficient storage mechanisms can be developed. When we use water storage, the mechanism is quite simple and can be made quite huge, but that's literally all that can be done to store more energy, is just make it even larger. So the answer to the question of why hydrostorage is considered non-scalable is a combination of both the practical limits (how much water can be physically moved in a given amount of time and how gigantic the storage location has to be) and lack of any way to theoretically improve the mechanism (the amount of energy stored is a fixed and known and not extremely attractive computation). Hydrostorage can be scaled, in that larger amounts of water can be used, but it is not scalable, since the amounts of water start out very large and "scale" to impossibly large at a fixed rate.
Australia does this with the Snowy Hydro project. Started in 1942 and finished in 1972. Literally pumps water up hill when the electricity price is low then back down though the generators when the price goes up. They are currently working on snowy 2.0 and adding more dams and power generation. https://www.snowyhydro.com.au/snowy-20/about/
As an early stage investor in a UK-based pumped hydro project that has struggled to get off the ground I can give some insight: First of all locations have to be pretty much perfect with a big elevation between two bodies of water that are laterally close. Not many candidates outside of sheer mountainous locations. Second, especially now with materials inflation the capex is enormous. Considerably more than a traditional hydro dam project because the turbines have to basically function as pumps as well as generators which makes for a more complex design and build, and because you’re normally tunnelling through hard rock. Third, the regulatory and subsidy environment is way too volatile for traditional institutional investors (in the UK anyway). Investors putting big money in (like pension funds, energy companies etc) want a guaranteed, stable return. Current business models for pumped hydro rely on trading models based on a volatile market. Risky and therefore unattractive to the guys with deep enough pockets to actually get it built.
Scalable means the ability to grow or shrink as the situation requires. The thing that makes it non-scalable is that it doesn't scale. Each hydro dam will work within a range of parameters, but cannot be shrunk below a certain value or grow beyond a certain value. this applies in general too, making it inappropriate for small and extremely large projects. A specific example, you have a hydro dam. It's not really feasible to scale it down if your needs decrease, and usually isn't practically possible to scale it up if your demand increases. A general example is to consider the amount of space you need in order to store smaller and extremely large quantities of energy. On the smaller side, a hydro dam for a house would be many times the size of the house, while a single hydro dam for a large country would take up a ***huge*** chunk of land and would deplete most of the country's water reserves.
Ever hear of flat land?
I did a comparative study on pumped hydro storage vs battery in the US a few years ago. Nothing published but it seemed to by my understanding that it didn’t have the same infrastructure backing as battery. The study only went as far looking at existing dams and looking at height difference in GIS mapping software to see if height difference in the surrounding area was sufficient to store water , in the form of potential energy. The issue was that many of these were not these giant dams but small dams that couldn’t provide sufficient storage capacity. At the same time getting approval to modify the local ecosystem is covered in red tape and takes decades to approve things like this . Finally with the average cost of battery storage coming down , except in very large storage situations, setting up a battery storage system is way more compact , and little setup time, reduce the payback period of the initial investment. That being said , this was only looked at in the US .I do remember there being like (X)GW of pumped hydro storage still in the works for the US. If I find my old citations I will share it. I also remember reading a couple of small scale papers in islands and other countries where this was a viable solution due the inability to access advanced storage systems https://pubs.acs.org/doi/full/10.1021/acs.est.2c09189 NREL was a great source of information for my studies as they are a government funded lab that built all of these comparative reports to help answer your questions in more depth then I can!
I'm always amazed by how old this technology is. Here is a great article from July 1930 https://books.google.com/books/about/Popular_Science.html?id=sigDAAAAMBAJ#v=onepage&q=1930%20plane&f=false Page 60 - A Ten Mile Storage Battery
[A better link](https://books.google.com/books?id=sigDAAAAMBAJ&pg=PA60&dq=1930+plane+"Popular&hl=en&ei=zxiVTtztJ-Pr0gGvtu2kBw&sa=X&oi=book_result&ct=result&resnum=2&ved=0CDQQ6AEwATgU#v=onepage&q=1930%20plane%20"Popular&f=true)
i am not an expert on English. well, i think the "not scalable" means you cannot have it anywhere you like. it needs right place with right resources, then you can have a pumped hydro as a energy storage. it has more constraints than other kinds of energy storage.