In the pursuit of green energy, storage is needed for 2 reasons:
- To smooth out the intermittency of solar and wind power.
- To store energy in electric vehicles without gasoline or diesel.
|Type||Metals of concern, and is there enough in the earth?||Other concerns||Energy footprint||Labor footprint|
|Lithium-ion batteries||Lithium: Just barely enough.
Cobalt: Not enough.
|Lifespan and recyclability||To be determined||To be determined|
|Lead-acid batteries||Lead: Not enough.||Toxic||To be determined||To be determined|
|Iron redox flow batteries||Iron: There is plenty.||Not implemented commercially yet. Could be viable for grid storage but not vehicles.||To be determined||To be determined|
|Flywheels||Iron: There is plenty. But other rare metals are probably needed too. To be determined.||Only the highest-energy-density designs would be worthwhile, but would they work in vehicles?||To be determined||To be determined|
|Hydrogen gas||To be determined - how many rare metals would be needed for the electrolysis and the fuel cells. Most likely not enough platinum.||In the case of vehicles: Needs pressurized fuel tanks, which might come with safety issues and wouldn't be as energy-dense as gasoline tanks. Also, fuel cell energy losses are higher than batteries.||To be determined||To be determined|
How much storage would be needed?
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.
^ 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).
How much storage is this really?
Most people aren't familiar with terajoules. Let's express it instead in terms of "gallons of gasoline equivalent energy" per person.
This much energy has to be stored in some other way (not gasoline).
Car engines can viably be built to burn hydrogen gas instead of gasoline. However, this isn't as efficient as building an electric car powered by hydrogen fuel cells (which use chemistry to convert the hydrogen energy back to electricity, which powers electric motors that run the car).
But even hydrogen fuel cells might not be quite efficient enough:
www.carboncommentary.com › blog › hydrogen-made-by-the-electrolysis...
www.californiahydrogen.org › uploads › files › doe_fuelcell_factsheet
This is only half the charge-discharge efficiency of lithium-ion batteries.
Hydrogen fuel cells contain rare minerals.[quantification needed]
Hydrogen gas requires a pressurized fuel tank, which is significantly heavier than a gasoline tank[quantification needed] but probably not as heavy as a lithium-ion battery pack, for the same amount of energy. Safety concerns are similar to other pressurized fuels such as natural gas or propane.
Heating and cooking
- Homes could be heated with hydrogen gas instead of natural gas.
- Gas-powered stoves could easily be adapted to burn hydrogen.
Lithium-ion batteries are the current standard for electric cars and most small gadgets (phones, laptops, etc).
Is there enough lithium?
It's 3.6 volts for the "cobalt type" of lithium-ion battery. Other types might have a very slightly different voltage.
The article says lithium per amp hour. We convert this to lithium per watt hour (energy), by including the cell voltage.
Added up all the countries: 9,200,000 + 4,700,000 + 1,900,000 + 1,500,000 + 750,000 + 220,000 + 95,000 + 60,000 = 18,425,000 metric tons
Just barely. How about cobalt?
- Using some other version of lithium-ion batteries, which doesn't depend so much on cobalt.
- Marketing cheaper electric vehicles with much smaller battery capacity, for city driving only.
- Extracting lithium from seawater (the viability of this may be questionable).
Other important stats:
from wikipedia; haven't found original source yet
Iron-redox flow batteries
But this battery comes with a few challanges:
- The iron has to be kept molten at very hot temperatures.
- Hence it's only viable to build a battery the size of a shipping container, not smaller.
- This battery is not suited for electric vehicles.
There would be enough iron:
The source doesn't specify whether this is steel from newly-mined iron or steel from recycling scrap. Probably it's both combined.
Besides being toxic, there wouldn't be enough lead to scale these up:
The only advantage is that some people already have a few lead-acid car batteries they could use in some DIY home energy storage solution.
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.
If flywheels are made mostly of steel (which is mostly iron), we would have enough metal to build enough of them:
However, 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.
How much energy would it take to refine all that steel?
However, the energy needed to manufacture the flywheels from the steel, might be vastly more. This page needs more research.
Viability of flywheels in vehicles is unknown too. 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.