Comment by remmargorp64 | Hacker News Reader

Comment by remmargorp64 | Hacker News Reader

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All they need to do is build mechanical/hydraulic systems for storing solar power during the day and unleashing it at night.

For example, use solar power during the day to pump fluid from a lower reservoir into a higher reservoir, and then harness the energy of the water flowing from the higher reservoir into the lower reservoir through turbines.

As long as your output energy is always coming from the turbines, and as long as your solar powered pumps running during the day can keep up with double the rate of drainage flow, then you should have a constant loop with a steady supply of power.

This type of system could be retrofitted onto virtually any dam, giving you a way to create a closed loop with constant power and without the water loss typical from a dam (other than evaporation).

For areas where water is scarce and a dam isn't feasible, there are also other ideas, such as gravitational potential energy systems that use solar powered energy to lift weights on pulleys, which then power a generator as the weights are lowered by gravity.

Other ideas: Thermal storage including molten salts which can efficiently store and release very large quantities of heat energy, compressed air energy storage, flywheels, cryogenic systems, etc...

You're wildly underestimating how complicated pumped hydro is.

For one thing, existing dams absolutely cannot be converted to pumped hydro. Dams do not store water below them. Water flows downstream because a dam is in a river. There is no water to pump uphill. Unless, of course, you also build a second dam very close downstream to create another lower reservoir. This is usually a bad idea, and better to just find better geography that will support a new pumped hydro dam.

Some dams, such as Lake Oroville in California, do use an afterbay to allow for off-peak water pumping back into the lake (https://norcalwater.org/efficient-water-management/efficient...).

Sadly, dams tend to destroy healthy fishery ecosystems —- a side effect of not “wasting” the water.

>...For example, use solar power during the day to pump fluid from a lower reservoir into a higher reservoir, and then harness the energy of the water flowing from the higher reservoir into the lower reservoir through turbines.

Trying to rely only on intermittent power sources has huge storage requirements due to weather along with daily/seasonal variation. If grid energy storage was a simple problem it would have been done decades ago.

For example, one estimate is that for Germany to rely on solar and wind would require about 6,000 pumped storage plants which is literally 183 times their current capacity:

>...Based on German hourly feed-in and consumption data for electric power, this paper studies the storage and buffering needs resulting from the volatility of wind and solar energy. It shows that joint buffers for wind and solar energy require less storage capacity than would be necessary to buffer wind or solar energy alone. The storage requirement of over 6,000 pumped storage plants, which is 183 times Germany’s current capacity, would nevertheless be huge.

https://www.econstor.eu/bitstream/10419/144985/1/cesifo1_wp5...

If you want to make renewable storage seem ridiculous, you just model storage as if every electron generated is precious and can't be wasted and you get an answer like the above.

Overprovisioning is so simple and widely accepted a concept that anyone ignoring it is likely trying to intentionally mislead.

> If grid energy storage was a simple problem it would have been done decades ago.

Except storage is much less useful in the old paradigm, so the motivation wasn't there. Going forward, prices will swing wildly, so storage will be more valuable.

>Except storage is much less useful in the old paradigm,

Plentiful storage would obviously have been very useful over the last several decades. There is a large variation in daily electrical usage (particularly in summer months):

https://www.eia.gov/todayinenergy/detail.php?id=42915

There is also the need for extra capacity in the system because of planned and unplanned maintenance.

>...Going forward, prices will swing wildly, so storage will be more valuable.

Well yes, our economy is based on having reliable power and it would be impossible to have anywhere near the reliable power relying on intermittent power sources without a huge amount of storage. The problem is that contrary to what advocates claim, people have been looking at grid energy storage for decades and it isn't as simple as they claim.

As Bill Gates said in an interview: "…They have this statement that the cost of solar photovoltaic is the same as hydrocarbon’s. And that’s one of those misleadingly meaningless statements. What they mean is that at noon in Arizona, the cost of that kilowatt-hour is the same as a hydrocarbon kilowatt-hour. But it doesn’t come at night, it doesn’t come after the sun hasn’t shone, so the fact that in that one moment you reach parity, so what? The reading public, when they see things like that, they underestimate how hard this thing is. So false solutions like divestment or “Oh, it’s easy to do” hurt our ability to fix the problems. Distinguishing a real solution from a false solution is actually very complicated."

https://www.theatlantic.com/magazine/archive/2015/11/we-need...

Gates is investing in 4th gen nuclear and energy storage companies so he is putting his money where his mouth is.

Good ideas but not currently feasible at grid-scale and so can't be really considered today as viable components of a power grid.

Yup, stacked concrete: https://qz.com/1355672/stacking-concrete-blocks-is-a-surpris...

Which all costs a lot of money.

There's nothing more handwavy than electricity storage

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