How scientists turn lakes into giant batteries
As of 2020, the world’s biggest
lithium-ion battery
is hooked up to the Southern California
power grid
and can provide 250 million watts
of power,
or enough to power about 250,000 homes.
But it’s actually not the biggest battery
in the world:
these lakes are.
Wait— how can a pair of lakes
be a battery?
To answer that question,
it helps to define a battery:
it’s simply something that stores energy
and releases it on demand.
The lithium-ion batteries that power
our phones, laptops, and cars
are just one type.
They store energy in lithium ions.
To release the energy, the ions
are separated from their electrons,
then rejoined at the other end
of the battery
as a new molecule with lower energy.
How do the two lakes
store and release energy?
First, one is 300 meters higher
than the other.
Electricity powers pumps that move
billions of liters of water
from the lower lake to the higher one.
This stores the energy by giving the water
extra gravitational potential energy.
Then, when there’s high demand
for electricity,
valves open, releasing the stored energy
by letting water flow downhill
to power 6 giant turbines that can
generate 3 billion watts of power
for 10 hours.
We’re going to need more and more
giant batteries.
That’s because right now, generating
enough electricity to power the world
produces an unsustainable amount
of greenhouse gas:
14 billion tons per year.
We’ll need to get that number
down to net-zero.
But many clean energy sources
can’t produce electricity 24/7.
So to make the switch, we need a way to
store the electricity until it's needed.
That means we need grid-scale batteries:
batteries big enough
to power multiple cities.
Unfortunately, neither of the giant
batteries we’ve talked about so far
can solve this problem.
The two lakes setup requires specific
geography, takes up a lot of land,
and has high upfront costs to build.
The giant lithium-ion battery
in California, meanwhile,
can power about 250,000 homes, yes,
but only for an hour.
Lithium-ion batteries are great for things
that don’t use a lot of power.
But to store a lot of energy,
they have to be huge and heavy.
That’s why electric planes aren’t a thing:
the best electric plane
can only carry two people
for about 1,000 kilometers on one charge,
or its batteries would be too heavy
to fly.
A typical commercial jet can carry
300 people over 14,000 km
before refueling.
Lithium-ion batteries also require
certain heavy metals to make.
These resources are limited, and mining
them often causes environmental damage.
Inventors all over the world are rising
to the challenge
of making batteries that can meet
our needs—
many of them even weirder
than the two lakes.
One company is building
a skyscraper battery.
When the sun is shining,
a crane powered by solar energy
piles blocks on top of each other
in a tower.
At night, the cranes let gravity
pull the blocks down
and use the resulting power
to spin generators.
Though there have been
some early setbacks,
another promising approach involves
heating up salts until they melt.
The molten salt can be stored until
there’s a high demand for electricity,
then used to boil water.
The steam can power turbines
that generate electricity.
Another idea: bio-batteries made
from paper, powered by bacteria,
and activated by spit.
Bacteria release energy in the form
of electrons when they metabolize glucose,
and at least one species of bacteria can
transfer those electrons
outside its cells,
completing a circuit.
While these batteries won’t power
a city, or even a house,
they don't have the waste and cost
concerns of traditional batteries.
From vast mountain lakes
to microscopic bacteria,
from seawater batteries
that bypass the need for heavy metals
to nuclear batteries
that power deep space missions,
we're constantly rethinking
what a battery can be.
The next unlikely battery could
be hiding in plain sight—
just waiting to be discovered
and help us achieve a sustainable future.
