The missing link to renewable energy

What's the key to using alternative energy, like solar and wind? Storage -- so we can have power on tap even when the sun's not out and the wind's not blowing. In this accessible, inspiring talk, Donald Sadoway takes to the blackboard to show us the future of large-scale batteries that store renewable energy. As he says: "We need to think about the problem differently. We need to think big. We need to think cheap."

The electricity powering the lights in this theater

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.,

and he proceeds to build --

(Laughter)

He proceeds to build

the first ever liquid metal battery

of this chemistry.

And based on David's initial promising results,

which were paid

with seed funds at MIT,

I was able to attract major research funding

from the private sector

and the federal government.

And that allowed me to expand my group to 20 people,

a mix of graduate students, post-docs

and even some undergraduates.

And I was able to attract really, really good people,

people who share my passion

for science and service to society,

not science and service for career building.

And if you ask these people

why they work on liquid metal battery,

their answer would hearken back

to President Kennedy's remarks

at Rice University in 1962

when he said -- and I'm taking liberties here --

"We choose to work on grid-level storage,

not because it is easy,

but because it is hard."

(Applause)

So this is the evolution of the liquid metal battery.

We start here with our workhorse one watt-hour cell.

I called it the shotglass.

We've operated over 400 of these,

perfecting their performance with a plurality of chemistries --

not just magnesium and antimony.

Along the way we scaled up to the 20 watt-hour cell.

I call it the hockey puck.

And we got the same remarkable results.

And then it was onto the saucer.

That's 200 watt-hours.

The technology was proving itself

to be robust and scalable.

But the pace wasn't fast enough for us.

So a year and a half ago,

David and I,

along with another research staff-member,

formed a company

to accelerate the rate of progress

and the race to manufacture product.

So today at LMBC,

we're building cells 16 inches in diameter

with a capacity of one kilowatt-hour --

1,000 times the capacity

of that initial shotglass cell.

We call that the pizza.

And then we've got a four kilowatt-hour cell on the horizon.

It's going to be 36 inches in diameter.

We call that the bistro table,

but it's not ready yet for prime-time viewing.

And one variant of the technology

has us stacking these bistro tabletops into modules,

aggregating the modules into a giant battery

that fits in a 40-foot shipping container

for placement in the field.

And this has a nameplate capacity of two megawatt-hours --

two million watt-hours.

That's enough energy

to meet the daily electrical needs

of 200 American households.

So here you have it, grid-level storage:

silent, emissions-free,

no moving parts,

remotely controlled,

designed to the market price point

without subsidy.

So what have we learned from all this?

(Applause)

So what have we learned from all this?

Let me share with you

some of the surprises, the heterodoxies.

They lie beyond the visible.

Temperature:

Conventional wisdom says set it low,

at or near room temperature,

and then install a control system to keep it there.

Avoid thermal runaway.

Liquid metal battery is designed to operate at elevated temperature

with minimum regulation.

Our battery can handle the very high temperature rises

that come from current surges.

Scaling: Conventional wisdom says

reduce cost by producing many.

Liquid metal battery is designed to reduce cost

by producing fewer, but they'll be larger.

And finally, human resources:

Conventional wisdom says

hire battery experts,

seasoned professionals,

who can draw upon their vast experience and knowledge.

To develop liquid metal battery,

I hired students and post-docs and mentored them.

In a battery,

I strive to maximize electrical potential;

when mentoring,

I strive to maximize human potential.

So you see,

the liquid metal battery story

is more than an account

of inventing technology,

it's a blueprint

for inventing inventors, full-spectrum.

(Applause)