was generated just moments ago.

Because the way things stand today,

electricity demand must be in constant balance

with electricity supply.

If in the time that it took me to walk out here on this stage,

some tens of megawatts of wind power

stopped pouring into the grid,

the difference would have to be made up

from other generators immediately.

But coal plants, nuclear plants

can't respond fast enough.

A giant battery could.

With a giant battery,

we'd be able to address the problem of intermittency

that prevents wind and solar

from contributing to the grid

in the same way that coal, gas and nuclear do today.

You see, the battery

is the key enabling device here.

With it, we could draw electricity from the sun

even when the sun doesn't shine.

And that changes everything.

Because then renewables

such as wind and solar

come out from the wings,

here to center stage.

Today I want to tell you about such a device.

It's called the liquid metal battery.

It's a new form of energy storage

that I invented at MIT

along with a team of my students

and post-docs.

Now the theme of this year's TED Conference is Full Spectrum.

The OED defines spectrum

as "The entire range of wavelengths

of electromagnetic radiation,

from the longest radio waves to the shortest gamma rays

of which the range of visible light

is only a small part."

So I'm not here today only to tell you

how my team at MIT has drawn out of nature

a solution to one of the world's great problems.

I want to go full spectrum and tell you how,

in the process of developing

this new technology,

we've uncovered some surprising heterodoxies

that can serve as lessons for innovation,

ideas worth spreading.

And you know,

if we're going to get this country out of its current energy situation,

we can't just conserve our way out;

we can't just drill our way out;

we can't bomb our way out.

We're going to do it the old-fashioned American way,

we're going to invent our way out,

working together.

(Applause)

Now let's get started.

The battery was invented about 200 years ago

by a professor, Alessandro Volta,

at the University of Padua in Italy.

His invention gave birth to a new field of science,

electrochemistry,

and new technologies

such as electroplating.

Perhaps overlooked,

Volta's invention of the battery

for the first time also

demonstrated the utility of a professor.

(Laughter)

Until Volta, nobody could imagine

a professor could be of any use.

Here's the first battery --

a stack of coins, zinc and silver,

separated by cardboard soaked in brine.

This is the starting point

for designing a battery --

two electrodes,

in this case metals of different composition,

and an electrolyte,

in this case salt dissolved in water.

The science is that simple.

Admittedly, I've left out a few details.

Now I've taught you

that battery science is straightforward

and the need for grid-level storage

is compelling,

but the fact is

that today there is simply no battery technology

capable of meeting

the demanding performance requirements of the grid --

namely uncommonly high power,

long service lifetime

and super-low cost.

We need to think about the problem differently.

We need to think big,

we need to think cheap.

So let's abandon the paradigm

of let's search for the coolest chemistry

and then hopefully we'll chase down the cost curve

by just making lots and lots of product.

Instead, let's invent

to the price point of the electricity market.

So that means

that certain parts of the periodic table

are axiomatically off-limits.

This battery needs to be made

out of earth-abundant elements.

I say, if you want to make something dirt cheap,

make it out of dirt --

(Laughter)

preferably dirt

that's locally sourced.

And we need to be able to build this thing

using simple manufacturing techniques and factories

that don't cost us a fortune.

So about six years ago,

I started thinking about this problem.

And in order to adopt a fresh perspective,

I sought inspiration from beyond the field of electricity storage.

In fact, I looked to a technology

that neither stores nor generates electricity,

but instead consumes electricity,

huge amounts of it.

I'm talking about the production of aluminum.

The process was invented in 1886

by a couple of 22-year-olds --

Hall in the United States and Heroult in France.

And just a few short years following their discovery,

aluminum changed

from a precious metal costing as much as silver

to a common structural material.

You're looking at the cell house of a modern aluminum smelter.

It's about 50 feet wide

and recedes about half a mile --

row after row of cells

that, inside, resemble Volta's battery,

with three important differences.

Volta's battery works at room temperature.

It's fitted with solid electrodes

and an electrolyte that's a solution of salt and water.

The Hall-Heroult cell

operates at high temperature,

a temperature high enough

that the aluminum metal product is liquid.

The electrolyte

is not a solution of salt and water,

but rather salt that's melted.

It's this combination of liquid metal,

molten salt and high temperature

that allows us to send high current through this thing.

Today, we can produce virgin metal from ore

at a cost of less than 50 cents a pound.

That's the economic miracle

of modern electrometallurgy.

It is this that caught and held my attention

to the point that I became obsessed with inventing a battery

that could capture this gigantic economy of scale.

And I did.

I made the battery all liquid --

liquid metals for both electrodes

and a molten salt for the electrolyte.

I'll show you how.

So I put low-density

liquid metal at the top,

put a high-density liquid metal at the bottom,

and molten salt in between.

So now,

how to choose the metals?

For me, the design exercise

always begins here

with the periodic table,

enunciated by another professor,

Dimitri Mendeleyev.

Everything we know

is made of some combination

of what you see depicted here.

And that includes our own bodies.

I recall the very moment one day

when I was searching for a pair of metals

that would meet the constraints

of earth abundance,

different, opposite density

and high mutual reactivity.

I felt the thrill of realization

when I knew I'd come upon the answer.

Magnesium for the top layer.

And antimony

for the bottom layer.

You know, I've got to tell you,

one of the greatest benefits of being a professor:

colored chalk.

(Laughter)

So to produce current,

magnesium loses two electrons

to become magnesium ion,

which then migrates across the electrolyte,

accepts two electrons from the antimony,

and then mixes with it to form an alloy.

The electrons go to work

in the real world out here,

powering our devices.

Now to charge the battery,

we connect a source of electricity.

It could be something like a wind farm.

And then we reverse the current.

And this forces magnesium to de-alloy

and return to the upper electrode,

restoring the initial constitution of the battery.

And the current passing between the electrodes

generates enough heat to keep it at temperature.

It's pretty cool,

at least in theory.

But does it really work?

So what to do next?

We go to the laboratory.

Now do I hire seasoned professionals?

No, I hire a student

and mentor him,

teach him how to think about the problem,

to see it from my perspective

and then turn him loose.

This is that student, David Bradwell,

who, in this image,

appears to be wondering if this thing will ever work.

What I didn't tell David at the time

was I myself wasn't convinced it would work.

But David's young and he's smart

and he wants a Ph.D.,