Flywheels

From the change wiki

Flywheels are a proposed solution to part of the energy storage problem.

Flywheels store energy mechanically by spinning a heavy rotor at high speeds. This has been implemented before, both inside vehicles (...)( but not necessarily storing enough energy to power the vehicle for more than a few kilometers at best ) and in stationary electrical systems (...)( with a much higher specific energy ).

Viability

#Need for iron Not too bad
#Need for rare-earth magnets Might be an issue[RESEARCH needed]
#Energy in manufacturing Unknown[RESEARCH needed]
#Charge/discharge losses Tradeoff with the other issues[RESEARCH needed]
#Suitable for vehicles? Probably not suitable enough[RESEARCH needed]

Need for iron

If flywheels are made mostly of steel (which is mostly iron), we would have enough metal to build enough of them:

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)

Note: This is roughly the amount of on-grid energy consumption that we might need energy storage for. It consists of - for example - lighting, heating, appliances, and other energy used in homes and other buildings. We don't count industrial here, because we can assume (in principle) that most factories could operate 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.
flywheels.practical.energy_by_mass
5 kWh per (450 kg)
Based on this product as an example: http://www.rosseta.de/texte/pdat-t4.pdf
iron.reserves
85 billion tonnes
Global iron reserves - iron metal recoverable
Source: Global iron ore reserves 2010-2021 - Statista
iron.production
1.95 billion tonnes/year
Source: World crude steel production 2021 - Statista



The source doesn't specify whether this is steel from newly-mined iron or steel from recycling scrap. Probably it's both combined.

other_energy.tfc * storage_timescale / flywheels.practical.energy_by_mass % iron.reserves (calculation loading) other_energy.tfc * storage_timescale / flywheels.theoretical.energy_by_mass % iron.reserves (calculation loading)

How much energy would it take to refine all that steel?

energy.tfc
9938 Mtoe/year
Global total final energy consumption
Source: Key World Energy Statistics 2020
steel.recycled.production.energy_by_mass
sqrt(1665*4170) watt hours per kg
How much energy does it take (on average) to produce 1 kilogram of...https://www.lowtechmagazine.com/what-is-the-embodied-energy-of-materials.html
steel.new.production.energy_by_mass
sqrt(5550*13900) watt hours per kg
How much energy does it take (on average) to produce 1 kilogram of...https://www.lowtechmagazine.com/what-is-the-embodied-energy-of-materials.html

steel.new.production.energy_by_mass * other_energy.tfc * storage_timescale / flywheels.practical.energy_by_mass months energy.tfc (calculation loading)

Energy in manufacturing

However, the energy needed to manufacture the flywheels from the steel, might be vastly more. This page needs more research.

Need for rare-earth magnets

It is unknown how much of other metals might be needed to make the flywheel systems - for example the rare earth magnets involved in the motor/generator components. This page needs more research.

Charge/discharge losses

Solutions might need a lot of rare-earth magnets or energy in manufacturing.[RESEARCH needed]

Suitable for vehicles?

Flywheel-based vehicles have existed for over a century, but they don't store enough energy to last more than a kilometer. Perhaps vacuum-sealed electrical type of flywheel could store more energy (...)( this page needs to clarify this more in previous paragraphs ), but would the bumps of the road cause energy losses too quickly? This page needs more research.