Energy storage

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In the pursuit of green energy, storage is needed for 2 reasons:

  1. To smooth out the intermittency of solar and wind power.
  2. To store energy in electric vehicles.

Note: This page does not include thermal energy storage.


Type Main issues
Lithium-ion batteries Needs too much cobalt
Lithium-sulfur batteries Can't handle enough charge cycles
Sodium-ion batteries Tech not ready yet
Sodium-sulfur batteries Tech not ready yet
Lead-acid batteries Toxic / hazardous
Iron redox flow batteries Not suited for vehicles
Hydrogen gas Energy losses, rare metal catalysts
Compressed air ?
Pumped hydro Only viable in rare geographical locations
Gravity blocks Outrageously high environmental footprint of construction
Flywheels ?

For more details, read the wikipage of each energy storage type. Links are in the table.

So far, sodium-based batteries seem to have the most hope of being a widespread solution - along with iron-based batteries for stationary energy storage.

How much energy storage might be needed?

Some quick estimates:


65.2 kWh
Energy capacity of the average electric vehicle battery
Useable battery capacity of full electric vehicles
1.446 billion
Without this, we'd be calculating for just personal vehicles. But we also need to factor in commercial vehicles such as buses and trucks. These vary widely in size, and data is hard to find, so for simplicity sake, we just assume that they'd add up to about the same as personal vehicles - thus doubling total energy storage needed. This assumption is based on the fact that freight trucks are a somewhat smaller share of energy demand than passenger vehicles, but the trucks probably need a longer range. * ev.battery * commercial_factor

^ This could be reduced by walkability and public transit (specifically trains).


3290.73 Mtoe/year
Global energy usage, total final consumption minus transport and industrial
Source: Key World Energy Statistics 2020 (IEA report)
We subtract transport because it was already dealt with above. We subtract industrial because - in principle, most factories/industry could just run during peak sunlight/wind, needing negligable energy storage.
24 hours
How big the "buffer" of energy storage would have to be to be resiliant against weather fluctuations
The exact number could be up for debate. Join the discussion.
other_energy.tfc * storage_timescale

^ This could be reduced by alternative heating/cooling systems for homes/buildings.

There are more options for this type of energy storage, because it's stationary (not moving in a vehicle).

These numbers might be reused on other wikipages to assess the large-scale viability of various types of energy storage. Don't worry if you're not familiar with terajoules as an energy unit.