5 ms·

Seems to me that the potential of simply lifting a weight up (storage) and down (generation) beats these fancy engineering goals for cost and practicality. Espe

Seems to me that the potential of simply lifting a weight up (storage) and down (generation) beats these fancy engineering goals for cost and practicality. Especially if the weight being lifted is a container full of rocks. At first glance there are plenty of those everywhere. No hills or reservoirs needed either. Of course, no papers need to be published ... that may be the goal.

chrisbrandow 3y ago
I’m excited about gravity storage but everything I’ve read indicates that the density and scalability are just not quite feasible.
- RhodesianHunter 3y ago
  It isn't. Even with pumping water up hill and letting it flow down, which is far easier and more efficient, there just isn't the land, elevation, and water for the scale we need.
  - ggm 3y ago
    This is one of those sort-of hyperbolic put downs which goes to "we need" encompassing the entire western worlds power requirements. No, you can't replace all existing power sources now and into the future by pumped hydro. Pumped hydro has a massive role to play in power supply, time shifting electricity from renewable sources, providing system resiliency, black start, inductive and inertial load, you-name-it. It also exists. It's in widespread use, across the globe. I have one less than 100km from me here in Qld, there is one under construction in the snowy hydro project (with issues) complementing an existing unit at Tumut, Another at Shoalhaven in NSW and there are two large sites in the UK power grid Dinorwig and Cruachan, both of which supply near-instantaneous (<20sec) power against demand shifts. Compared to gas turbine load start (minutes), pumped hydro is fast (seconds). Compared to batteries (milliseconds), It's slow. Batteries have capacity limits too. In the capacity stakes, Pumped hydro can beat them hands-down but for a massive initial capital outlay. Snowy 2.0 will supply DAYS of power. 2Gigawatts, as 350GWh of power. 3 million homes equivalent, for a week. People argue about the economics, not about the underlying capability. Worldwide there are plenty of good sites, including mine shafts. And, gravity models for power include trains, and cranes. Neither of which will replace all sources of power for all burdens in the network either. The idea this is limited to existing land-surface bodies of water simply isn't true. Not all useful things have to be able to solve the problems "at the scale we need" to be both useful, and able to solve problems.
    - kamranjon 3y ago
      I’ve always wanted to ask someone who knew something about this stuff if this idea is feasible: Imagine a giant empty bucket held high in the air. As it rains, the bucket fills and using a counter-weight it slowly lowers down to ground level. Now the bucket is covered and the water is slowly drained causing the counter-weight to lower to the ground and the bucket to rise in the air again. If this were geared properly, could energy be generated in any meaningful amount?
      - ben_w 3y ago
        Nowhere rains enough for that; hydro dams only manage it by having a huge catchment area nobody needs to build. Highest rainfall in a year: > 26,470 mm (1,042 in); Cherrapunji, Meghalaya, India, 1860–1861 https://en.wikipedia.org/wiki/List_of_weather_records https://en.wikipedia.org/wiki/List_of_weather_records 26.4 tons * 1km * 9.8m/s/s / 1 year = 7.4 watts
      - deleted 3y ago
        [deleted]
      - noam_k 3y ago
        Randall Monroe made some calculations here: https://what-if.xkcd.com/91/ https://what-if.xkcd.com/91/
      - magicalhippo 3y ago
        You just described hydroelectric power but with more steps and a much smaller area to catch rain.
    - RhodesianHunter 3y ago
      No at all. No one is suggesting it must cover all power needs. Sure, there may be municipalities that are advantaged by it due to the unique and perfect nature of their geography. But that's not going to be enough to put any realistic dent in the problem at a national level. Many people have done the math. https://dothemath.ucsd.edu/2011/11/pump-up-the-storage/ https://dothemath.ucsd.edu/2011/11/pump-up-the-storage/
- imtringued 3y ago
  Building the contraption that carries weights is not feasible. Worse yet, if you have to pay for the weights, then your idea needs to be thrown out entirely because you will never recoup the cost of a manufactured weight.
ReptileMan 3y ago
Unfortunately lifting weights is extremely efficient and low energy endeavor. So it makes a really shitty density wise storage.
robinzfc 3y ago
To estimate the cost and practicality, assume you build a tower 120 meters tall and machinery able to lift 60 tons block of concrete to the top, then retrieve the stored energy by lowering it to the ground level. Think for a moment how much that would cost. Then calculate: mgh = 60000kg x 120m x 10m/s^2 (assume acceleration of gravity is 10m/s^2 for simplicity, no energy losses due to friction etc). The result is 72 million joules. That is 20 kilowatt-hours, about two days of a single household electricity usage.
- harry8 3y ago
  >assume you build a tower 120 meters I think the more popular approach is to use a deep hole, like a mine shaft. Maybe depth measured in kms. Because you're suspending from above you might be able to get a bit heavier than 60 tons.
  - aniken 3y ago
    useage in this manner could lead to a mineshaft gap
  - imtringued 3y ago
    A kilometer deep hole is not very cheap.
    - nerpderp82 3y ago
      Lets make them cheap. What is the minimum shaft size to get construction equipment to the bottom?
- hbossy 3y ago
  Or you could avoid building the machinery and just pump water up and down. Then to lower the cost you could drop the tower idea and use a natural hill with reservoir on top. Surprise, surprise you just invented a pumped-storage power station.
  - nostrademons 3y ago
adrian_b 3y ago
This is already used in many places, due to the very low cost, but the amount of energy stored in a given volume is very small in comparison with batteries or supercapacitors, even when a great difference in height is available.
Cthulhu_ 3y ago
That only works for relatively small amounts of (potential) energy, not grid-scale; the best / most efficient form of that is pumping water up into an elevated lake, that's the scalable version. But it's limited by availability of elevation and whatnot.

chrisbrandow 3y ago

I’m excited about gravity storage but everything I’ve read indicates that the density and scalability are just not quite feasible.

RhodesianHunter 3y ago
It isn't. Even with pumping water up hill and letting it flow down, which is far easier and more efficient, there just isn't the land, elevation, and water for the scale we need.
- ggm 3y ago
  This is one of those sort-of hyperbolic put downs which goes to "we need" encompassing the entire western worlds power requirements. No, you can't replace all existing power sources now and into the future by pumped hydro. Pumped hydro has a massive role to play in power supply, time shifting electricity from renewable sources, providing system resiliency, black start, inductive and inertial load, you-name-it. It also exists. It's in widespread use, across the globe. I have one less than 100km from me here in Qld, there is one under construction in the snowy hydro project (with issues) complementing an existing unit at Tumut, Another at Shoalhaven in NSW and there are two large sites in the UK power grid Dinorwig and Cruachan, both of which supply near-instantaneous (<20sec) power against demand shifts. Compared to gas turbine load start (minutes), pumped hydro is fast (seconds). Compared to batteries (milliseconds), It's slow. Batteries have capacity limits too. In the capacity stakes, Pumped hydro can beat them hands-down but for a massive initial capital outlay. Snowy 2.0 will supply DAYS of power. 2Gigawatts, as 350GWh of power. 3 million homes equivalent, for a week. People argue about the economics, not about the underlying capability. Worldwide there are plenty of good sites, including mine shafts. And, gravity models for power include trains, and cranes. Neither of which will replace all sources of power for all burdens in the network either. The idea this is limited to existing land-surface bodies of water simply isn't true. Not all useful things have to be able to solve the problems "at the scale we need" to be both useful, and able to solve problems.
  - kamranjon 3y ago
    I’ve always wanted to ask someone who knew something about this stuff if this idea is feasible: Imagine a giant empty bucket held high in the air. As it rains, the bucket fills and using a counter-weight it slowly lowers down to ground level. Now the bucket is covered and the water is slowly drained causing the counter-weight to lower to the ground and the bucket to rise in the air again. If this were geared properly, could energy be generated in any meaningful amount?
    - ben_w 3y ago
      Nowhere rains enough for that; hydro dams only manage it by having a huge catchment area nobody needs to build. Highest rainfall in a year: > 26,470 mm (1,042 in); Cherrapunji, Meghalaya, India, 1860–1861 https://en.wikipedia.org/wiki/List_of_weather_records https://en.wikipedia.org/wiki/List_of_weather_records 26.4 tons * 1km * 9.8m/s/s / 1 year = 7.4 watts
    - deleted 3y ago
      [deleted]
    - noam_k 3y ago
      Randall Monroe made some calculations here: https://what-if.xkcd.com/91/ https://what-if.xkcd.com/91/
    - magicalhippo 3y ago
      You just described hydroelectric power but with more steps and a much smaller area to catch rain.
  - RhodesianHunter 3y ago
    No at all. No one is suggesting it must cover all power needs. Sure, there may be municipalities that are advantaged by it due to the unique and perfect nature of their geography. But that's not going to be enough to put any realistic dent in the problem at a national level. Many people have done the math. https://dothemath.ucsd.edu/2011/11/pump-up-the-storage/ https://dothemath.ucsd.edu/2011/11/pump-up-the-storage/
imtringued 3y ago
Building the contraption that carries weights is not feasible. Worse yet, if you have to pay for the weights, then your idea needs to be thrown out entirely because you will never recoup the cost of a manufactured weight.

ReptileMan 3y ago

Unfortunately lifting weights is extremely efficient and low energy endeavor. So it makes a really shitty density wise storage.

robinzfc 3y ago

To estimate the cost and practicality, assume you build a tower 120 meters tall and machinery able to lift 60 tons block of concrete to the top, then retrieve the stored energy by lowering it to the ground level. Think for a moment how much that would cost. Then calculate: mgh = 60000kg x 120m x 10m/s^2 (assume acceleration of gravity is 10m/s^2 for simplicity, no energy losses due to friction etc). The result is 72 million joules. That is 20 kilowatt-hours, about two days of a single household electricity usage.

harry8 3y ago
>assume you build a tower 120 meters I think the more popular approach is to use a deep hole, like a mine shaft. Maybe depth measured in kms. Because you're suspending from above you might be able to get a bit heavier than 60 tons.
- aniken 3y ago
  useage in this manner could lead to a mineshaft gap
- imtringued 3y ago
  A kilometer deep hole is not very cheap.
  - nerpderp82 3y ago
    Lets make them cheap. What is the minimum shaft size to get construction equipment to the bottom?
hbossy 3y ago
Or you could avoid building the machinery and just pump water up and down. Then to lower the cost you could drop the tower idea and use a natural hill with reservoir on top. Surprise, surprise you just invented a pumped-storage power station.
- nostrademons 3y ago

adrian_b 3y ago

This is already used in many places, due to the very low cost, but the amount of energy stored in a given volume is very small in comparison with batteries or supercapacitors, even when a great difference in height is available.

Cthulhu_ 3y ago

That only works for relatively small amounts of (potential) energy, not grid-scale; the best / most efficient form of that is pumping water up into an elevated lake, that's the scalable version. But it's limited by availability of elevation and whatnot.