Energy storage

We'll need a lot of energy storage for 2 main reasons:

1. To smooth out the natural fluctuations of wind and solar
2. To store energy in cars and other vehicles, without fossil fuels

Types / Case studies

Energy storage type	EROI iEROI stands for "energy return on investment". The energy invested includes: ~ the construction of the storage system ~ energy lost in charging, storage, or discharging The energy returned includes only the energy obtained by discharging. 💬 discussion For some rows of the table, if I have a half-baked estimate that doesn't factor in all losses yet, I can add "<&eq;" in front of the number to indicate that additional stuff might bring it down	Vehicle- usable?	Materials per MJ stored i1 MJ (megajoule) is about equivalent to the energy in an ounce of gasoline 💬 discussion For any scarce mineral involved, I should quantify the mass but also show it as a percentage of {global mineral reserves per capita in 2024}. Also, should I add an additional column about recyclability? But then also gotta specify that it matters more in some cases than others (as in, it depends how scarce the minerals involved are).
NMC lithium-ion batteries		Yes	Full mass: _; Lithium: _; Nickel: _; Cobalt: _;
LFP lithium batteries		Yes	Full mass: _; Lithium: _;
Sodium-ion batteries 💬 discussion May need to be more specific about which implementation of sodium-ion, because it's not standard yet. Btw, in this table maybe I could put more than 1 row for the same energy storage type, each row linking to a different estimate		Yes	Full mass: _;
Iron-redox flow batteries		No	Full mass: _; Iron: _;
Hydrogen production + combustion💬 discussion for this and the fuel cell one, the "materials needed" depend on the capacity factor of the energy source used to produce the hydrogen. For these cases, probably go with wind power as the default.		Yes	💬 discussion Need to specify a storage time horizon before quantifying platinum-group metals, as it's proportional to production 'rate', not total energy stored.
Hydrogen production + fuel cell		Yes
Hydrogen storage, pressurized 💬 discussion Maybe I should have a subsection for hydrogen, showing various cases based on: production energy source, storage type, storage time, and usage type. Need not cover all combinations, just enough to illustrate		Maybe
Gravity "battery"		No
Flywheels		Barely
Compressed air		Barely
Pumped hydro		No	Land: _; 💬 discussion Assuming a particular height of water pumped, or something. Gotta be a case study

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