Energy storage

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.

Types

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:

Vehicles

ev.battery

65.2 kWh

Energy capacity of the average electric vehicle battery

Useable battery capacity of full electric vehicles
https://ev-database.org/cheatsheet/useable-battery-capacity-electric-car

world.cars

1.446 billion

How Many Cars Are There In The World in 2022?
https://hedgescompany.com/blog/2021/06/how-many-cars-are-there-in-the-world/

commercial_factor

2

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.

world.cars * ev.battery * commercial_factor

terajoules

vehicle_energy_storage_needed

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

Other

other_energy.tfc

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.

storage_timescale

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

terajoules

other_energy_storage_needed

^ 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.