3 ms·

2-6 hours is nowhere near enough to offset daily fluctuations, let alone seasonal fluctuations. Overproduction only gets you so far, unless this proposal also i

2-6 hours is nowhere near enough to offset daily fluctuations, let alone seasonal fluctuations. Overproduction only gets you so far, unless this proposal also involves transoceanic HVDC cables. Hydropower is not exactly the same thing as storage: you can stop releasing water and build up the reservoir, but you cannot pump water up river. Even just 6 hours of storage -which would not be sufficient even with several factors of overproduction - is 15,000 GWh of storage to satisfy present global electricity use.

Retric 3y ago
Overproduction means you don’t ever see daily fluctuations you have a surplus every single day of the year. Unless storage gets insanely cheap that’s by far the cheapest safe option. Hydropower dams are already storage. When you don’t release the water it’s saved until you do. If you have enough rain from 3 months ago to release 10 MW 24/7 over a week then you also have enough water to release 15 MW for 12 hours and 5 MW for the other 12 every day etc. You can’t save 100% of the water or the river downstream runs dry but the minimum is generally well below the average flow rate. This isn’t unusual, most dams ramp production up and down to maximize the value of the stored water.
- Manuel_D 3y ago
  > Overproduction means you don’t ever see daily fluctuations you have a surplus every single day of the year. No, this is not even remotely true. No amount of solar overproduction will let you produce energy at night. 12 hours a day (on average, depend on the season) you will not have any production regardless of overproduction. You'll have a lot of excess energy during the day, but still no energy when the sun has set. Infinity times zero is still zero. Not unless you create transoceanic HVDC cables that connect Eurasia to the Americas, literally piping electricity from one side of the world to the other. Wind also has windless days, with more extreme seasonal fluctuations. Overproduction is not a silver bullet that eliminates the need for storage. Just because you have net surplus over the course of a 24-hour period does not mean demand was satisfied at all times. This is why intermittent sources are so challenging. > Hydropower dams are already storage. When you don’t release the water it’s saved until you do. But you can only save energy at the rate that rainfall refills the dam. If you have a dam that refills at a rate of 10MW, you can only effectively store 10MW of excess energy. If you have 20MW of excess production, you can still only store 10MW and the other 10 MW is wasted. Dams are not batteries, they can store a lot of energy but they can only be refilled at the rate dictated by rainfall. You also can't completely shut off a dam or the river will run dry with serious ecological consequences, and impairing downstream water supply.
  - Retric 3y ago
    Excess per day doesn’t mean you get solar power every single second just per day, that’s what batteries are for. > But you can only sacs energy at the rate rainfall refills the dam. > can’t completely shut off You’re completely misunderstanding how dams are used look here: https://en.wikipedia.org/wiki/Hoover_Dam https://en.wikipedia.org/wiki/Hoover_Dam Installed capacity 2,078.8 MW, Capacity factor 23% Minimum flow rate isn’t 0, but is plenty low enough to have a great deal of flexibility.
    - Manuel_D 3y ago
      > Excess per day doesn’t mean you get solar power every single second just per day, that’s what batteries are for. ...which would require an enormous and infeasibly large amount of batteries. You're right: overproduction doesn't mean you get power for every second per day. But a grid does need sufficient energy at every single second per day or you have blackouts. This is why overproduction of intermittent sources is not as useful as it sounds. Nothing in your link about dams contradicts what I wrote: their rate of recharge is limited. You can shut off much of the turbines and let the reservoir build up, but they cannot be recharged faster than the rate at which rainfall refills the reservoir. Judging by a 2 GW capacity and 23% capacity factor, one would infer that it's refilled at a rate of ~500 MW (in reality, less than that since Lake Meade is shrinking). Completely shutting off the turbines would only refill at a rate of 500 MW. If you have 2 GW of overproduction, you can't refill Lake Meade with 2 GW of potential energy. You can shut down its turbines and let the reservoir refill at a rate of 500 MW, but the other 1,500 MW can't be used to recharge Lake Meade. A dam is sort of like a battery but its rate of recharge is much more limited than it's rate of discharge, which is a big disadvantage when trying to capture the overproduction from intermittent sources.
      - Retric 3y ago
        > ...which would require an enormous and infeasibly large amount of batteries False, but you can’t substantiate your argument by simply saying the words you need to back it up with something such as actual calculations etc. > Their rate of recharge is limited That’s completely irrelevant here. Rainfall is so concentrated in short periods that they often have months of water in reserve and can decide when exactly to release it over that kind of timeframe. 95% of the time there is less water flowing out of a dam than flowing into it. That’s why we build dams.

Retric 3y ago

Overproduction means you don’t ever see daily fluctuations you have a surplus every single day of the year. Unless storage gets insanely cheap that’s by far the cheapest safe option. Hydropower dams are already storage. When you don’t release the water it’s saved until you do. If you have enough rain from 3 months ago to release 10 MW 24/7 over a week then you also have enough water to release 15 MW for 12 hours and 5 MW for the other 12 every day etc. You can’t save 100% of the water or the river downstream runs dry but the minimum is generally well below the average flow rate. This isn’t unusual, most dams ramp production up and down to maximize the value of the stored water.

Manuel_D 3y ago
> Overproduction means you don’t ever see daily fluctuations you have a surplus every single day of the year. No, this is not even remotely true. No amount of solar overproduction will let you produce energy at night. 12 hours a day (on average, depend on the season) you will not have any production regardless of overproduction. You'll have a lot of excess energy during the day, but still no energy when the sun has set. Infinity times zero is still zero. Not unless you create transoceanic HVDC cables that connect Eurasia to the Americas, literally piping electricity from one side of the world to the other. Wind also has windless days, with more extreme seasonal fluctuations. Overproduction is not a silver bullet that eliminates the need for storage. Just because you have net surplus over the course of a 24-hour period does not mean demand was satisfied at all times. This is why intermittent sources are so challenging. > Hydropower dams are already storage. When you don’t release the water it’s saved until you do. But you can only save energy at the rate that rainfall refills the dam. If you have a dam that refills at a rate of 10MW, you can only effectively store 10MW of excess energy. If you have 20MW of excess production, you can still only store 10MW and the other 10 MW is wasted. Dams are not batteries, they can store a lot of energy but they can only be refilled at the rate dictated by rainfall. You also can't completely shut off a dam or the river will run dry with serious ecological consequences, and impairing downstream water supply.
- Retric 3y ago
  Excess per day doesn’t mean you get solar power every single second just per day, that’s what batteries are for. > But you can only sacs energy at the rate rainfall refills the dam. > can’t completely shut off You’re completely misunderstanding how dams are used look here: https://en.wikipedia.org/wiki/Hoover_Dam https://en.wikipedia.org/wiki/Hoover_Dam Installed capacity 2,078.8 MW, Capacity factor 23% Minimum flow rate isn’t 0, but is plenty low enough to have a great deal of flexibility.
  - Manuel_D 3y ago
    > Excess per day doesn’t mean you get solar power every single second just per day, that’s what batteries are for. ...which would require an enormous and infeasibly large amount of batteries. You're right: overproduction doesn't mean you get power for every second per day. But a grid does need sufficient energy at every single second per day or you have blackouts. This is why overproduction of intermittent sources is not as useful as it sounds. Nothing in your link about dams contradicts what I wrote: their rate of recharge is limited. You can shut off much of the turbines and let the reservoir build up, but they cannot be recharged faster than the rate at which rainfall refills the reservoir. Judging by a 2 GW capacity and 23% capacity factor, one would infer that it's refilled at a rate of ~500 MW (in reality, less than that since Lake Meade is shrinking). Completely shutting off the turbines would only refill at a rate of 500 MW. If you have 2 GW of overproduction, you can't refill Lake Meade with 2 GW of potential energy. You can shut down its turbines and let the reservoir refill at a rate of 500 MW, but the other 1,500 MW can't be used to recharge Lake Meade. A dam is sort of like a battery but its rate of recharge is much more limited than it's rate of discharge, which is a big disadvantage when trying to capture the overproduction from intermittent sources.
    - Retric 3y ago
      > ...which would require an enormous and infeasibly large amount of batteries False, but you can’t substantiate your argument by simply saying the words you need to back it up with something such as actual calculations etc. > Their rate of recharge is limited That’s completely irrelevant here. Rainfall is so concentrated in short periods that they often have months of water in reserve and can decide when exactly to release it over that kind of timeframe. 95% of the time there is less water flowing out of a dam than flowing into it. That’s why we build dams.