[cupofpython]

Makes sense, it is definitely a useful tool. I just think it is insufficient to act as storage. It can be good at producing variable amounts of Watts on demand but not so good at storing enough Watt-hours to keep things running for very long. I can see a great appeal for it to help with load-balancing for a significant amount of choppiness between supply and demand on the hour timescale.

For something like solar, where we will want to store over half our daily energy production at peak storage (ideally 2-3 days worth I think) - I don't think it holds up. Additionally, it doesnt seem like a good bet as a primary mechanism for either storage or on-demand generation if energy consumption continues to increase due to the rather large coefficients involved for scaling it up.

"The United States generated 4,116 terawatt hours of electricity in 2021"[1]

4,116 TWh/year = 11.2 TWh/day

The storage capacities for the largest items listed on the wiki is on the magnitude of GWh. The scale goes kilo-, Mega-, Giga-, then Terra. So we are talking about a need on the order of a thousand pumped storage facilities per country. The US would need over 50 of them per state (on average) in order to keep everything running without production for 24 hours. Doesnt matter how many solar panels we have, if we get 1 dark day then we would run out of power. If we tried to rely on solar entirely, we'd also still need very roughly half that amount of storage just to get through the night.

lithium batteries are obviously much better suited for overnight storage, but I have no idea what the numbers are on how much lithium is physically available to use as such storage.

If we want to get on the order of monthly to yearly storage to allow, for example, solar panels in alaska to provide enough energy for a resident to get through months of darkness - I have no idea what the leading storage options are, probably lithium still

[1]https://www.statista.com/statistics/188521/total-us-electric...

[Schroedingersat]

Sodium ion is expected to sharply take over cost limited applications some time in the next couple of years. There are pilot mass production programs designed to avoid scarce materials that drop into existing processes. Natron have products on the market (at presumably high cost) targetting datacenters for high safety applications.

For longer scale storage it's a tossup between opportunistic pumped hydro, CAES where geology makes it easy, hydrogen in similar areaswith caverns, ammonia, synthetic hydrocarbons, sodium ion, and one of the emerging molten salt or redox flow battery technogies. Lithium isn't really in the running due to resource limits.

Wires also have a lot of value for decreasing the need for storage. Joining wind and solar 1000s of km apart can greatly reduce downtime. Replacing as much coal and oil with those, and maintaining the OCGT and CCGT fleet is the fastest and most economic way to target x grams of CO2e per kWh where x is some number much smaller than the 400 of pure fossil fuels but bigger than around 50. Surplus renewable power (as adding 3 net watts of solar is presently cheaper than the week of storage to get an isolated area through that one week where capacity is 1/3rd the average) will subsidize initial investments into better storage and electrolysis with no further interventions needed.

[cupofpython]

Awesome response. I've come across the molten salt option but havent researched in depth. I saw it referenced as something a lot of scientists are hyping up, but I am not sure what kind of engineering challenges exist for implementation and maintenance.

Second paragraph is a bit too information dense, I had trouble following some of it. Renewable energy deficiencies will be localized, so i understand how wires help here. A larger connected area produces more stability, makes sense. Agreed with the carbon reduction priority to tackle coal and oil first. Surplus renewable power acting as a subsidy checks out, but that is skirting around the energy storage problem imo. Sounds like you are saying "instead of storing renewable energy, get more than you need and sell it back to the grid and then use those funds to buy the energy back later". This would certainly work for local consumers, but doesnt do too much to help the power grid itself manage what to do with the surplus energy. Sell it to neighboring power grids? Ties in to the first point about connecting a larger area - but what are the limits here? Can we physically connect the sunny side of earth to the dark side? (ignoring that it seems logistically/legally prohibitive)

the question really comes down to what should we be spending money on to get "better storage"? What are the best solutions for long-term local storage?