3 ms·

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-t

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.

moloch-hai 4y ago
Adding some numbers. A smallish supertanker, one you are more likely to find available for scrap, carried in its day 500,000 barrels of oil. That weighs ~79,000 tonnes. So if you use 5000 tonne weights, it has capacity for only about 16 of them. The biggest tankers in use now would handle 32. This is a smaller number than I would have guessed. So, maybe you use 1000 tonne weights instead, and put 80 of them aboard, with 80 cables, reels, and clutches, and maybe five shafts. If you don't want to build a "moon pool" for each cable through the bottom of the ship, you can run balanced pairs of them over pulleys on opposite gunwales.

moloch-hai 4y ago

Adding some numbers. A smallish supertanker, one you are more likely to find available for scrap, carried in its day 500,000 barrels of oil. That weighs ~79,000 tonnes. So if you use 5000 tonne weights, it has capacity for only about 16 of them. The biggest tankers in use now would handle 32. This is a smaller number than I would have guessed. So, maybe you use 1000 tonne weights instead, and put 80 of them aboard, with 80 cables, reels, and clutches, and maybe five shafts. If you don't want to build a "moon pool" for each cable through the bottom of the ship, you can run balanced pairs of them over pulleys on opposite gunwales.