4 ms·

I always thought it'd be interesting to do the gravity storage inside the column of a wind turbine. After all you've already built a tall steel tower. Individua

by mNovak 6y ago

I always thought it'd be interesting to do the gravity storage inside the column of a wind turbine. After all you've already built a tall steel tower. Individually it's tiny storage, but in aggregate it's not meaningless, especially as we keep building more towers. But I assume there's structural issues with suspending a few extra tons on your structure.

dragontamer 6y ago
I feel like "gravity storage" should take advantage of natural landscapes better. ARES (rail energy storage) builds a rail-line uphill, for example. Rail cannot handle a very steep slope, but a gentle hill climb will build up potential energy fine. In the case of vertical-based gravity storage, I'd imagine that lifting blocks to the top of a cliff (or down a valley) would be most efficient. I mean, Pumped Hydro is gravity storage, and does just that. Pumping water up a mountain and generating energy by dropping it back down. But presumably, we don't want to use water in the Western states (where water is scarce). So Gravity-energy storage WITHOUT water is the goal.
- syllable_studio 6y ago
  The issue with using natural landscapes is that it limits your height. And adding more height is ~exponentially~ (edit: quadratically) better than just adding more installations with an equivalent total height. (You can dig about a mile deep). You can see more details in my comments below - search for the text "It is worth it to dig a hole!"
  - dragontamer 6y ago
    I was thinking of combining techniques. Best case scenario in USA is something like Owens Valley: 14,000 at its peak, but 4000 feet at the bottom of the valley. Leading to ~10,000 feet (or nearly 2-miles) of elevation change. From there, you can dig another mile underground, leading to 1-mile (under ground), or -1000 feet elevation, to a peak elevation of 14,000. If a tower were built on the top of the mountain: you could gain another 2000 feet or so on top: so maybe 16,000 (a 2000 foot tower on top of the mountain peak) to -1000ft (1-mile deep from the bottom of the 4000-ft elevation valley), for a total differential of 17,000 feet. Ignoring earthquakes and other issues, of course. :-) Just purely from a hypothetical perspective: working with nature and the natural landscape seems like it'd be better than "just" digging a hole. EDIT: Repurposing abandoned mine shafts might be worthwhile, depending how deep they are.
  - andbberger 6y ago
    Wrong, wrong, wrong, so wrong! Gravitational potential energy is (approximately) linear in height. I say approximately because this assumes constant g (which is a good assumption when h is small compared to the radius of the earth, which it is). And in fact, a consequence of gravity's 1/r^2 nature is that one is only subject to gravitational acceleration from what is beneath them (shells above cancel out), so mine shafts are less efficient than towers (the effect size is small to the depths we can mine). So adding more height doesn't help, and if that height is underground it could actually hurt net efficiency. Efficiency in this context refers potential energy stored per unit height. The field is conservative no matter what you build.
    - syllable_studio 6y ago
      Hey andbberger, Yeah, we're _definitely_ assuming that g is constant for all elevations :) There's another thread on this comment page talking about why height is important. Please see this slide in our presentation illustrating it. https://docs.google.com/presentation/d/17FI-jrI9RWS3q7Ng44YhiHs7il8JvnxK-cV6_g_-cGo/edit#slide=id.g844fb8814b_1_136 https://docs.google.com/presentation/d/17FI-jrI9RWS3q7Ng44Yh...
      - Xylakant 6y ago
        I don't think it's fair to call that "scales quadratic". Certainly the energy stored in the total number of blocks is growing quadratic by digging deeper, but it also ignores that costs and effort grow when digging deeper. In effect, adding a block at the bottom comes with substantially higher effort than adding a block right next to it on the same level.
    - reitzensteinm 6y ago
      I'm assuming that the quadratic parent refers to comes from the increased potential energy per kg of material multiplied by the ability to store more material due to the additional volume. If you picture a dense weight like a cannon ball on the end of a string you're right, but if you're digging down n meters, encasing n/2 meters worth of dirt and moving it up and down the free n/2 meters of shaft, the energy storage would indeed be proportional to n^2. I don't know anything about the field and had the same reaction you did, but considering parent is running a startup in it they're either a lunatic that doesn't know the equivalent of FizzBuzz or there's something we missed on first inspection, and we should charitably assume the latter...
- mNovak 6y ago
  The issue here is that not everyone has that landscape (and as we know, doesn't want to destroy the view). I grew up in the US midwest--no hills for miles on which to build railcars, pump hydro etc.
  - dragontamer 6y ago
    But high-voltage power lines can run power for hundreds of miles with minuscule losses. Look at the MISO grid: https://upload.wikimedia.org/wikipedia/commons/4/40/2015_MISO_Map.png https://upload.wikimedia.org/wikipedia/commons/4/40/2015_MIS... There's hills somewhere in there, and those hills can form energy-storage solutions that can be transmitted across the entire MISO grid.
    - adrianN 6y ago
      High voltage lines are not free. You have to compete with different energy storage that doesn't need special landscapes, e.g. batteries.
      - dragontamer 6y ago
        High voltage power lines already exist. They are part of the landscape, and connect large parts of the country together. Case in point: a solar panel is Missouri could be providing power to Iowa. Bonus points: if you want to build a big battery in Iowa, you can take advantage of excess power in Iowa or Missouri. Building tiny batteries here and there will only lower your efficiency. There's a reason why a lot of discussion here is on large 100s of MW proposals: because anything smaller won't really be a big win economically. And it shouldn't be too hard to fill up 100s of MW capacity because of the nature of our large and reliable power grids here in the USA.
    - tonyedgecombe 6y ago
      In general more connectivity means you need less storage as it's always windy/sunny somewhere in the world.
- octoberfranklin 6y ago
  Lifting things creates hazards for what's below them in the event of catastrophic failure. For example, all the dam failures that have obliterated entire towns. I'd rather a failure obliterated a bunch of earthworms and voles. I expect that the voles disagree with me.
jbay808 6y ago
That's pretty clever! I would guess that wind turbine towers are mainly loaded in bending, and an extra compression load wouldn't hurt much as long as it doesn't cause buckling.
syllable_studio 6y ago
Yeah, this would be similar to what energyvault.com is doing. I love that energy vault got funding ($110M) and is pushing the industry forward. But IMHO, I ultimately don't think they will be able to compete with underground gravity storage because of the massive 10x advantage you get from digging underground and getting 10x more height (see my other comments below why that is.)
MurMan 6y ago
This idea assumes that the interior of the tower is empty space that could be used by the moving weight. Towers have an elevator for maintenance personnel that would reduce the available space. I'm guessing that the towers aren't high enough to store enough energy to justify the cost of the extra equipment. I doubt that suspending the weight is the main structural issue. It's the high center of mass when the weight is at the top.
- mNovak 6y ago
  Yup, internal space is a very valid issue, given that cheap weights are probably big. I'd worry about oscillations for a high-up, suspended weight too. Regarding justifying the cost--obviously depends what the cost is. If it's really just the generator, cabling etc, it might work as a short term load balancer. I saw somewhere about GE investing $X millions to smooth turbine output over 5min intervals.
simonebrunozzi 6y ago
It wouldn't work - the towers would need to be heavier to handle the extra weight of the gravity storage, denying all benefits.
hannob 6y ago
This actually exists using water. There's a pilot installation in southern Germany which has been running for a few years: https://www.naturspeicher.de/de/pilotprojekt/pilotprojekt.php https://www.naturspeicher.de/de/pilotprojekt/pilotprojekt.ph...
owenversteeg 6y ago
> (100 ton) * (80 meter) * (9.81 (m / (s^2))) = 21.8 kilowatt hours Nah. In exchange for nearly doubling the weight of the average 3MW tower, adding enormous complexity, you'd be able to boost power output to 3.02 MW for one hour. That gets us back to the fundamental problem with gravity storage - it's all mgh. You want to store a lot of energy, you better have a shit-ton of either m, g, or h, and one of those numbers is already tough to change :)

by mNovak 6y ago

dragontamer 6y ago

I feel like "gravity storage" should take advantage of natural landscapes better. ARES (rail energy storage) builds a rail-line uphill, for example. Rail cannot handle a very steep slope, but a gentle hill climb will build up potential energy fine. In the case of vertical-based gravity storage, I'd imagine that lifting blocks to the top of a cliff (or down a valley) would be most efficient. I mean, Pumped Hydro is gravity storage, and does just that. Pumping water up a mountain and generating energy by dropping it back down. But presumably, we don't want to use water in the Western states (where water is scarce). So Gravity-energy storage WITHOUT water is the goal.

syllable_studio 6y ago
The issue with using natural landscapes is that it limits your height. And adding more height is ~exponentially~ (edit: quadratically) better than just adding more installations with an equivalent total height. (You can dig about a mile deep). You can see more details in my comments below - search for the text "It is worth it to dig a hole!"
- dragontamer 6y ago
  I was thinking of combining techniques. Best case scenario in USA is something like Owens Valley: 14,000 at its peak, but 4000 feet at the bottom of the valley. Leading to ~10,000 feet (or nearly 2-miles) of elevation change. From there, you can dig another mile underground, leading to 1-mile (under ground), or -1000 feet elevation, to a peak elevation of 14,000. If a tower were built on the top of the mountain: you could gain another 2000 feet or so on top: so maybe 16,000 (a 2000 foot tower on top of the mountain peak) to -1000ft (1-mile deep from the bottom of the 4000-ft elevation valley), for a total differential of 17,000 feet. Ignoring earthquakes and other issues, of course. :-) Just purely from a hypothetical perspective: working with nature and the natural landscape seems like it'd be better than "just" digging a hole. EDIT: Repurposing abandoned mine shafts might be worthwhile, depending how deep they are.
- andbberger 6y ago
  Wrong, wrong, wrong, so wrong! Gravitational potential energy is (approximately) linear in height. I say approximately because this assumes constant g (which is a good assumption when h is small compared to the radius of the earth, which it is). And in fact, a consequence of gravity's 1/r^2 nature is that one is only subject to gravitational acceleration from what is beneath them (shells above cancel out), so mine shafts are less efficient than towers (the effect size is small to the depths we can mine). So adding more height doesn't help, and if that height is underground it could actually hurt net efficiency. Efficiency in this context refers potential energy stored per unit height. The field is conservative no matter what you build.
  - syllable_studio 6y ago
    Hey andbberger, Yeah, we're _definitely_ assuming that g is constant for all elevations :) There's another thread on this comment page talking about why height is important. Please see this slide in our presentation illustrating it. https://docs.google.com/presentation/d/17FI-jrI9RWS3q7Ng44YhiHs7il8JvnxK-cV6_g_-cGo/edit#slide=id.g844fb8814b_1_136 https://docs.google.com/presentation/d/17FI-jrI9RWS3q7Ng44Yh...
    - Xylakant 6y ago
      I don't think it's fair to call that "scales quadratic". Certainly the energy stored in the total number of blocks is growing quadratic by digging deeper, but it also ignores that costs and effort grow when digging deeper. In effect, adding a block at the bottom comes with substantially higher effort than adding a block right next to it on the same level.
  - reitzensteinm 6y ago
    I'm assuming that the quadratic parent refers to comes from the increased potential energy per kg of material multiplied by the ability to store more material due to the additional volume. If you picture a dense weight like a cannon ball on the end of a string you're right, but if you're digging down n meters, encasing n/2 meters worth of dirt and moving it up and down the free n/2 meters of shaft, the energy storage would indeed be proportional to n^2. I don't know anything about the field and had the same reaction you did, but considering parent is running a startup in it they're either a lunatic that doesn't know the equivalent of FizzBuzz or there's something we missed on first inspection, and we should charitably assume the latter...
mNovak 6y ago
The issue here is that not everyone has that landscape (and as we know, doesn't want to destroy the view). I grew up in the US midwest--no hills for miles on which to build railcars, pump hydro etc.
- dragontamer 6y ago
  But high-voltage power lines can run power for hundreds of miles with minuscule losses. Look at the MISO grid: https://upload.wikimedia.org/wikipedia/commons/4/40/2015_MISO_Map.png https://upload.wikimedia.org/wikipedia/commons/4/40/2015_MIS... There's hills somewhere in there, and those hills can form energy-storage solutions that can be transmitted across the entire MISO grid.
  - adrianN 6y ago
    High voltage lines are not free. You have to compete with different energy storage that doesn't need special landscapes, e.g. batteries.
    - dragontamer 6y ago
      High voltage power lines already exist. They are part of the landscape, and connect large parts of the country together. Case in point: a solar panel is Missouri could be providing power to Iowa. Bonus points: if you want to build a big battery in Iowa, you can take advantage of excess power in Iowa or Missouri. Building tiny batteries here and there will only lower your efficiency. There's a reason why a lot of discussion here is on large 100s of MW proposals: because anything smaller won't really be a big win economically. And it shouldn't be too hard to fill up 100s of MW capacity because of the nature of our large and reliable power grids here in the USA.
  - tonyedgecombe 6y ago
    In general more connectivity means you need less storage as it's always windy/sunny somewhere in the world.
octoberfranklin 6y ago
Lifting things creates hazards for what's below them in the event of catastrophic failure. For example, all the dam failures that have obliterated entire towns. I'd rather a failure obliterated a bunch of earthworms and voles. I expect that the voles disagree with me.

jbay808 6y ago

That's pretty clever! I would guess that wind turbine towers are mainly loaded in bending, and an extra compression load wouldn't hurt much as long as it doesn't cause buckling.

syllable_studio 6y ago

Yeah, this would be similar to what energyvault.com is doing. I love that energy vault got funding ($110M) and is pushing the industry forward. But IMHO, I ultimately don't think they will be able to compete with underground gravity storage because of the massive 10x advantage you get from digging underground and getting 10x more height (see my other comments below why that is.)

MurMan 6y ago

This idea assumes that the interior of the tower is empty space that could be used by the moving weight. Towers have an elevator for maintenance personnel that would reduce the available space. I'm guessing that the towers aren't high enough to store enough energy to justify the cost of the extra equipment. I doubt that suspending the weight is the main structural issue. It's the high center of mass when the weight is at the top.

mNovak 6y ago
Yup, internal space is a very valid issue, given that cheap weights are probably big. I'd worry about oscillations for a high-up, suspended weight too. Regarding justifying the cost--obviously depends what the cost is. If it's really just the generator, cabling etc, it might work as a short term load balancer. I saw somewhere about GE investing $X millions to smooth turbine output over 5min intervals.

simonebrunozzi 6y ago

It wouldn't work - the towers would need to be heavier to handle the extra weight of the gravity storage, denying all benefits.

hannob 6y ago

This actually exists using water. There's a pilot installation in southern Germany which has been running for a few years: https://www.naturspeicher.de/de/pilotprojekt/pilotprojekt.php https://www.naturspeicher.de/de/pilotprojekt/pilotprojekt.ph...

owenversteeg 6y ago

> (100 ton) * (80 meter) * (9.81 (m / (s^2))) = 21.8 kilowatt hours Nah. In exchange for nearly doubling the weight of the average 3MW tower, adding enormous complexity, you'd be able to boost power output to 3.02 MW for one hour. That gets us back to the fundamental problem with gravity storage - it's all mgh. You want to store a lot of energy, you better have a shit-ton of either m, g, or h, and one of those numbers is already tough to change :)