3 ms·

Flywheels never seem to work out for storing more than a few seconds' power. The pictures here do not show them mounted underground or surrounded by earthen be

Flywheels never seem to work out for storing more than a few seconds' power. The pictures here do not show them mounted underground or surrounded by earthen berms, which seems foolishly hazardous. The Philippines could store power much more economically by suspending weights from cable reels on a ship, lowering them to the sea floor to extract power. The key to economical operation is to share a big motor-generator and winch, protected from weather, along a single shaft with a long line of reels and weights coupled via clutches. This is akin to the similar scheme using a mineshaft, but is much more economically viable. Using separate weights, the winch can usefully be of much lower capacity than the mineshaft needs, so available off-the-shelf. The seabed is in many places deeper than common disused mineshafts, and there is plenty of it.

closewith 4y ago
> The key to economical operation is to share a big motor-generator and winch, protected from weather, along a single shaft with a long line of reels and weights coupled via clutches. With respect, placing machinery at sea and protecting it from weather are antithetical.
- moloch-hai 4y ago
  Tell that to cruise-line passengers and offshore wind-turbine operators. The key is keeping parts necessarily exposed to weather simple and sturdy, and the touchy electro-mechanical stuff well housed. A physical shaft between them safely moves power in or out. We see the same dichotomy play out in wave-energy extraction systems, where wave action pumps air through a turbine. The air could easily be conducted via a culvert to a turbine onshore, safely indoors, and shared. But somehow people building those seem never think of it.
  - willyt 4y ago
    Convert semi submersible oil rigs, which are designed for deep water, to grid storage?
    - moloch-hai 4y ago
      If you are suspending a lot of heavy weights, you need something buoyant enough to hold them all up. An old supertanker would work fine. You make tunnels from the bottom up to the reels, for the cables to run through. You would want to let it turn to face waves, but you need and electrical tie-in to shore, or anyway to the nearest wind farm to move power in and out. All the weights hanging deep under water keep it stable. Motor/generator and winch are maybe where the engine was.
    - moloch-hai 4y ago
      There will be a hell of a lot of surplus supertankers.
schiffern 4y ago
This is quite a fascinating suggestion. * Water has ~1000x as much drag as air, so you want your weights to be shaped like low-drag bodies. * Buoyancy will somewhat counteract the weight of your ballast, so there's an incentive to use high-density material (this also reduces hydrodynamic drag). High-density concrete, with a density of 6.0-6.4 g/ml, is an obvious choice. * The specific material will, of course, need to be tested to withstand pressure cycling at operational depths. * The natural project locations fall along the continental shelf, as close as possible to the shore. This allows cheap power connections in shallow water, while still enjoying maximum operational depth. * Since you'll be operating well within the SOFAR channel, you'll probably want to implement acoustic mitigations (eg slower speeds when passing through those depths, sound-dampening tether connections, low-noise shape, low-vibration equipment, project siting away from critical marine ecosystems, etc). * Semi-submersible vessels are likely worth considering, since that means one end of the cable won't be trying to bob up and down in the waves. * If you really can covert an existing vessel, I expect the weights will need to be hung in a way that approximates the distribution of the original payload. This would be necessary to avoid invalidating the vessel's original structural and stability calculations. Thank you. Overall, a very intriguing proposal! Do you know anyone working on this?
- moloch-hai 4y ago
  1. Ironstone riprap in nets would probably be better than a concrete block, both for cost and density. 2. The weight on a tether should be as large as an off-the-shelf crane winch can manage, to balance descent speed and cost. Maybe 5000t? Tether descent speed is probably not enough to matter, environmentally or energetically. 3. For best shape and reliability, overlap a series of nets on the tether. Tethers might be cable or chain, or some of each. 3. Site over an ocean trench close to shore. There is a lot of ocean, so only the best sites need be chosen. Taiwan, the whole east coast of South America, S Spain, Monaco, SE Greece, SE India, Sydney, Togo, E South Africa, Madagascar, Monterey (CA), SW Mexico, Cuba, Japan, Hawaii, various Indonesian islands, and the Philippines have deep water right offshore. 3. Calm water might matter more than maximum depth. A thousand meters is usefully deep. 4. The huge mass on all the tethers in deep water -- there is no need to hoist above, say, 100m deep -- aids stability. 5. Tethers may be distributed over the entire length and beam of the vessel, via pulleys. Mount a dozen parallel shafts, with a winch/motor/generator at the end, on each vessel. Shafts run the full length of the vessel, with a reel, clutch, and brake for each tether. 6. You can attach multiple vessels together, side by side, for more stability. There will be a lot of surplus supertankers. 7. The advantage over tethering in a mineshaft is that the winch and motor/generator can be shared among as many tethers as you like, and the winch may be off-the-shelf. 8. Storage beyond a couple of weeks' worth will probably not be a big market. Beyond that, you just order a shipment of NG or, later, ammonia to burn. Building out gravity storage reduces your NG bill. I don't recall where I saw this mentioned. That company doing winches in mineshafts, Gravitricity, could branch out. All contact with fraudsters at Energy Vault Holdings must be avoided.

closewith 4y ago

> The key to economical operation is to share a big motor-generator and winch, protected from weather, along a single shaft with a long line of reels and weights coupled via clutches. With respect, placing machinery at sea and protecting it from weather are antithetical.

moloch-hai 4y ago
Tell that to cruise-line passengers and offshore wind-turbine operators. The key is keeping parts necessarily exposed to weather simple and sturdy, and the touchy electro-mechanical stuff well housed. A physical shaft between them safely moves power in or out. We see the same dichotomy play out in wave-energy extraction systems, where wave action pumps air through a turbine. The air could easily be conducted via a culvert to a turbine onshore, safely indoors, and shared. But somehow people building those seem never think of it.
- willyt 4y ago
  Convert semi submersible oil rigs, which are designed for deep water, to grid storage?
  - moloch-hai 4y ago
    If you are suspending a lot of heavy weights, you need something buoyant enough to hold them all up. An old supertanker would work fine. You make tunnels from the bottom up to the reels, for the cables to run through. You would want to let it turn to face waves, but you need and electrical tie-in to shore, or anyway to the nearest wind farm to move power in and out. All the weights hanging deep under water keep it stable. Motor/generator and winch are maybe where the engine was.
  - moloch-hai 4y ago
    There will be a hell of a lot of surplus supertankers.

schiffern 4y ago

This is quite a fascinating suggestion. * Water has ~1000x as much drag as air, so you want your weights to be shaped like low-drag bodies. * Buoyancy will somewhat counteract the weight of your ballast, so there's an incentive to use high-density material (this also reduces hydrodynamic drag). High-density concrete, with a density of 6.0-6.4 g/ml, is an obvious choice. * The specific material will, of course, need to be tested to withstand pressure cycling at operational depths. * The natural project locations fall along the continental shelf, as close as possible to the shore. This allows cheap power connections in shallow water, while still enjoying maximum operational depth. * Since you'll be operating well within the SOFAR channel, you'll probably want to implement acoustic mitigations (eg slower speeds when passing through those depths, sound-dampening tether connections, low-noise shape, low-vibration equipment, project siting away from critical marine ecosystems, etc). * Semi-submersible vessels are likely worth considering, since that means one end of the cable won't be trying to bob up and down in the waves. * If you really can covert an existing vessel, I expect the weights will need to be hung in a way that approximates the distribution of the original payload. This would be necessary to avoid invalidating the vessel's original structural and stability calculations. Thank you. Overall, a very intriguing proposal! Do you know anyone working on this?

moloch-hai 4y ago
1. Ironstone riprap in nets would probably be better than a concrete block, both for cost and density. 2. The weight on a tether should be as large as an off-the-shelf crane winch can manage, to balance descent speed and cost. Maybe 5000t? Tether descent speed is probably not enough to matter, environmentally or energetically. 3. For best shape and reliability, overlap a series of nets on the tether. Tethers might be cable or chain, or some of each. 3. Site over an ocean trench close to shore. There is a lot of ocean, so only the best sites need be chosen. Taiwan, the whole east coast of South America, S Spain, Monaco, SE Greece, SE India, Sydney, Togo, E South Africa, Madagascar, Monterey (CA), SW Mexico, Cuba, Japan, Hawaii, various Indonesian islands, and the Philippines have deep water right offshore. 3. Calm water might matter more than maximum depth. A thousand meters is usefully deep. 4. The huge mass on all the tethers in deep water -- there is no need to hoist above, say, 100m deep -- aids stability. 5. Tethers may be distributed over the entire length and beam of the vessel, via pulleys. Mount a dozen parallel shafts, with a winch/motor/generator at the end, on each vessel. Shafts run the full length of the vessel, with a reel, clutch, and brake for each tether. 6. You can attach multiple vessels together, side by side, for more stability. There will be a lot of surplus supertankers. 7. The advantage over tethering in a mineshaft is that the winch and motor/generator can be shared among as many tethers as you like, and the winch may be off-the-shelf. 8. Storage beyond a couple of weeks' worth will probably not be a big market. Beyond that, you just order a shipment of NG or, later, ammonia to burn. Building out gravity storage reduces your NG bill. I don't recall where I saw this mentioned. That company doing winches in mineshafts, Gravitricity, could branch out. All contact with fraudsters at Energy Vault Holdings must be avoided.