4 ms·

If you want to calculations on just how far short batteries fall, I do so here: https://news.ycombinator.com/item?id=36949165 https://news.ycombinator.com/item?

If you want to calculations on just how far short batteries fall, I do so here: https://news.ycombinator.com/item?id=36949165 https://news.ycombinator.com/item?id=36949165 The rate of recharge is absolutely relevant, because you can't actually capture excess production from intermittent sources. If you're relying on a dam to fulfill periods of non-production, you need a way to put the excess energy during periods of overproduction back into the dam. But a dam can only shut down its turbines, it can't be recharged faster than the rate that rainfall refills it. If you need 40% of your electricity coming from dams during periods of non-production, then you need rainfall sufficient to produce that much energy. It's not like a battery where you can take excess production and store it back in the dam. That's how pumped hydro electric storage works: you run turbines backwards and refill the dam with excess energy. But pumped hydro requires a very specific set of geographic features, and is not easy to scale up.

Retric 3y ago
> If you're relying on a dam to fulfill periods of non-production, you need a way to put the excess energy during periods of overproduction back into the dam. If you're relying on a dam to fulfill periods of non-production, you need a way to put the excess energy during periods of overproduction back into the dam. I understand your point but it’s based on faulty assumptions. Simply not using existing water means it’s still there. If you have 10,000$ in your bank account and you don’t buy something you still have the 10,000$. Dams are the same way if you have 20,000 MWh worth of water and can average 20 MWh for the next 1,000 hours then generating 10 MW for the 500 hours of those hours and 30 MW for the other 500 hours hits zero at exactly the same time. Recharge is important long term but irrelevant in the short term. You might expect to receive water from the spring thaw, but that’s a long way away. Large dams like the hover are built to contain multiple years worth of average flow for a river. It took more than a full year just to collect enough water for them to start generating hydropower. As to your analysis, > 500 GWh globally That’s an outdated estimate for last year even just EV’s broke 500 GWh. “Automotive lithium-ion (Li-ion) battery demand increased by about 65% to 550 GWh in 2022, from about 330 GWh in 2021” https://www.iea.org/reports/global-ev-outlook-2023/trends-in-batteries https://www.iea.org/reports/global-ev-outlook-2023/trends-in... Your number was an estimate for 2022 total production made during 2022, and they got it wrong which isn’t that surprising as EV sales ended up 55% from 2021 and average battery sizes also increased. 2023 numbers are hard to estimate for similar reasons. > Production of batteries may grow in the future Again, the rates have been increasing by double digits per year for a long time, that’s wildly faster than the increase in electricity demand. We don’t need to talk in hypothetical terms here just current factories already wildly invalidate your calculation let alone any kind of longer term estimates when grid storage may start to pick up. > 12 hours As I mentioned that’s a monumental overestimate, but not particularly relevant compared to the first two issues. We can quibble about specifics here but compared to even a 50% EV world grid storage simply isn’t a major factor.
- Manuel_D 3y ago
  Rate of recharge is the limiting factor of the total amount of energy you can release from a dam without reducing the total amount of water in the reservoir over time. Hoover dam may be able to produce 2GW of power, but if it averages more than 500 MW it will drop in water level over time (actually less than that, since it's already reaching record low fill levels). True, rainfall is not constant throughout the year. But it doesn't really matter in the big picture: the total amount of energy you can produce with the dam without lowering fill levels is fixed, and it isn't changed by overproduction. Overproduction doesn't help you here: if you have 3 GW of solar energy and 2 GW of electricity demand, you can't use the remaining 1 GW to refill Hoover Dam. If you produce enough solar to meet demand, you can shut off hoover dam's turbines. But if you overproduce - if you produce more energy than the grid needs - it's wasted, you can't use excess energy to refill the dam beyond just shutting off the turbines. > That’s an outdated estimate for last year even just EV’s broke 500 GWh. "Automotive lithium-ion (Li-ion) battery demand increased by about 65% to 550 GWh in 2022" Demand, not production. Just under 500 GWh of batteries was produced, a good chunk of demand went unfulfilled. If anything, all your source shows is that grid storage is even more infeasible because we can't even satisfy EV's storage needs. > As I mentioned that’s a monumental overestimate No, if anything it's an optimistic underestimate. 12 hours is just enough for diurnal storage. But you also need storage to offset seasonal fluctuations.

Retric 3y ago

> If you're relying on a dam to fulfill periods of non-production, you need a way to put the excess energy during periods of overproduction back into the dam. If you're relying on a dam to fulfill periods of non-production, you need a way to put the excess energy during periods of overproduction back into the dam. I understand your point but it’s based on faulty assumptions. Simply not using existing water means it’s still there. If you have 10,000$ in your bank account and you don’t buy something you still have the 10,000$. Dams are the same way if you have 20,000 MWh worth of water and can average 20 MWh for the next 1,000 hours then generating 10 MW for the 500 hours of those hours and 30 MW for the other 500 hours hits zero at exactly the same time. Recharge is important long term but irrelevant in the short term. You might expect to receive water from the spring thaw, but that’s a long way away. Large dams like the hover are built to contain multiple years worth of average flow for a river. It took more than a full year just to collect enough water for them to start generating hydropower. As to your analysis, > 500 GWh globally That’s an outdated estimate for last year even just EV’s broke 500 GWh. “Automotive lithium-ion (Li-ion) battery demand increased by about 65% to 550 GWh in 2022, from about 330 GWh in 2021” https://www.iea.org/reports/global-ev-outlook-2023/trends-in-batteries https://www.iea.org/reports/global-ev-outlook-2023/trends-in... Your number was an estimate for 2022 total production made during 2022, and they got it wrong which isn’t that surprising as EV sales ended up 55% from 2021 and average battery sizes also increased. 2023 numbers are hard to estimate for similar reasons. > Production of batteries may grow in the future Again, the rates have been increasing by double digits per year for a long time, that’s wildly faster than the increase in electricity demand. We don’t need to talk in hypothetical terms here just current factories already wildly invalidate your calculation let alone any kind of longer term estimates when grid storage may start to pick up. > 12 hours As I mentioned that’s a monumental overestimate, but not particularly relevant compared to the first two issues. We can quibble about specifics here but compared to even a 50% EV world grid storage simply isn’t a major factor.

Manuel_D 3y ago
Rate of recharge is the limiting factor of the total amount of energy you can release from a dam without reducing the total amount of water in the reservoir over time. Hoover dam may be able to produce 2GW of power, but if it averages more than 500 MW it will drop in water level over time (actually less than that, since it's already reaching record low fill levels). True, rainfall is not constant throughout the year. But it doesn't really matter in the big picture: the total amount of energy you can produce with the dam without lowering fill levels is fixed, and it isn't changed by overproduction. Overproduction doesn't help you here: if you have 3 GW of solar energy and 2 GW of electricity demand, you can't use the remaining 1 GW to refill Hoover Dam. If you produce enough solar to meet demand, you can shut off hoover dam's turbines. But if you overproduce - if you produce more energy than the grid needs - it's wasted, you can't use excess energy to refill the dam beyond just shutting off the turbines. > That’s an outdated estimate for last year even just EV’s broke 500 GWh. "Automotive lithium-ion (Li-ion) battery demand increased by about 65% to 550 GWh in 2022" Demand, not production. Just under 500 GWh of batteries was produced, a good chunk of demand went unfulfilled. If anything, all your source shows is that grid storage is even more infeasible because we can't even satisfy EV's storage needs. > As I mentioned that’s a monumental overestimate No, if anything it's an optimistic underestimate. 12 hours is just enough for diurnal storage. But you also need storage to offset seasonal fluctuations.