The first fuel-powered automobile was invented in 1885

by Karl Benz of Mercedes-Benz,

who applied for a patent for his three wheeled,

gasoline-powered Motorwagen the following year.

But there were cars even before that,

like this electric car that was invented in the 1830s,

and this steam-powered tricycle

which had been rolling around France way back in 1769.

Incredibly, it wasn't until 1955

that the world's first solar-powered vehicle was demonstrated.

Even then, at a mere 38cm long,

it was too tiny for a human to drive.

But then, in 1962,

a drivable solar-powered car was finally unveiled.

Turns out, building a vehicle that's powered by the sun

is actually a lot more challenging

than using steam or electricity.

Or really old carbon, also known as fossil fuel.

But while commercially available solar cars

haven't yet made it onto our roadways,

what seems like an impossible piece of technology

is actually very much a reality.

And these solar cars are capable of going faster

and further than you might think.

What's more, the technology in today's solar vehicles

could drive us all toward a cleaner, greener future.

So in this episode, we take a look under the hood

of one of the world's fastest solar cars

to better understand,

how does a solar car actually work?

Like me, you've probably thought of solar cars

as something out of science fiction.

Like, a technology so futuristic and complex

that it feels like it can't actually exist in the real world.

But going back to William Cobb's

38-centimeter model car from 1955,

the Sunmobile,

it seems like solar cars of the past

were pretty simple machines.

This is today's solar car.

Okay, it's a model solar car,

but it is fully functional.

It's about 8cm long, just over three inches,

so it's even smaller than that Sunmobile.

But it's got all the same major components.

Here's the solar panel

that converts those photons into electricity.

We actually covered that whole process in detail

in a previous chapter, so check that out.

That electricity then travels here

to this small direct current motor,

and that motor then converts electricity

into mechanical energy, which propels the car.

Check it out.

Now, as long as the car's solar cells are exposed to sunlight,

there's enough power to keep the wheels turning

and the car moving.

But if that sunlight is cut off...

then the car becomes a paperweight.

Now, this basic demonstration,

and yes, it is a very basic demonstration,

it shows how solar cars of the past worked.

If there were sunlight, they could go.

No sunlight, no go.

So you can see why solar cars of the past

have not been considered a viable option.

Luckily, today's solar cars are a bit more sophisticated.

Okay, a lot more sophisticated.

The solar racers competing in the world Solar Challenge, for example,

don't just use the latest in photovoltaic technology,

they've also adopted innovations

in design, engineering and battery technology.

To get a closer look under the hood

of one of these solar racers,

I got to connect with a few members

of the racing team from Stanford University.

My name is Cori Brendel. I was the team lead

for the 2019 Stanford Solar Car Project cycle.

My name is Cameron Haynesworth.

I'm a junior at Stanford University.

Hi, I'm Julia Gordon.

I started out on the aerodynamics team,

and throughout the race preparation time,

I ended up in a kind of jack-of-all-trades role.

Julia was actually behind the wheel for the 2019 race,

which, unfortunately, didn't go so well for the Stanford team.

I think, like, right as we got outside the city,

I remember I started smelling smoke.

I smell a not good smell.

I remember watching as they pulled the panel off,

just flames come out of the car.

MAREN: Although the Stanford team

had a disappointing performance in 2019,

the team felt that it was overall

an overwhelmingly positive experience.

So we always go in with wanting to win.

But I think one of the big principles underlying the team

is just pushing the envelope

for what we can do with engineering and technology.

So being able to work on a team

that has so many different expertises

working toward one common goal is great,

because you just get exposed to so many really new

and kind of novel engineering concepts.

This drive to innovate pushed the Stanford team

to make a pivotal change in their race car's design.

The project has been around for 30 years now.

This was our 14th vehicle that we've built.

We've always done like a multi-fairing car.

Usually that's a catamaran,

which is your traditional two-fairing vehicle.

CAMERON: Yeah, Black Mamba was definitely a new car.

We went to Black Mamba, which is a bullet car design,

which means all of the wheels are in one fairing.

Um, I'm not an aerodynamics expert,

but single fairing is better for aero

because you are eliminating extra edges on your car.

CAMERON: The trade-off to that is,

as you move your wheels closer together,

it's a lot easier to tip your car.

And the other problem is with the array size.

CORI: To get a really small car,

we went with gallium-arsenide cells

'cause when you use more efficient cells,

you can reduce the size of your car.

CAMERON: We put the driver on the right side of the car,

so it was asymmetric, which had some advantages with the aerodynamics

as well as the shading of the sun on our solar panels,

so that the driver didn't shade the solar panels.

And it was also the first asymmetrical bullet car in WSC.

All the other bullet cars in WSC were center driver.

JULIA: It felt like this one radical change

just kind of spurred off more ambition and more drive

to see how far we can really push Black Mamba.

Another major upgrade to the Stanford solar racer...

gallium-arsenide solar panels.

CAMERON: In the past we had done a silicon array.

Gallium-arsenide is a new development in solar panel technology

that allows for higher efficiencies in solar panels.

We talked about gallium-arsenide technology

in our previous chapter on solar panels.

So, go learn all about that here.

CORI: The size of the gallium-arsenide array

was 3.56 square meters.

And to cover that size array, you need about 100 grand.

Now, to keep things competitive, the World Solar Challenge

did limit the size of gallium-arsenide arrays for each team,

so that teams without the resources,

meaning money, to access this technology,

could still compete in the race fairly.

So then, gallium-arsenide was a whole new technology

with different current and voltage specifications,

so then that changes the entire electrical system,

because when you're operating with different current,

you have to change things down there, too.

On the battery side,

it's a whole new form-factor that you have to fit in the car.

For balance reasons, you'd want the battery across from your driver,

so that your driver and battery can balance each other out,

so battery had a whole new form factor.

MAREN: The battery is one of the key upgrades

to today's solar cars.

Whereas solar cars of the past

sent electricity generated by their solar panels

directly to the motor,

modern solar cars, like Stanford's Black Mamba,

use photovoltaic technology

to charge the lithium-ion batteries

that then power the vehicle.

So the basic gist is that

you've got your solar array, battery and motors.

Then those are all connected

by the internal circuitry of the car.

So as the solar array generates power,

that goes into a battery pack, which starts recharging,

and the solar ray also connects out to the motors.

MAREN: This allows these solar cars to run

even when there's no direct sunlight available.

CORI: There's times when you have more supply

than you have demand, or vice versa.

So really, what you need is you need to have some kind of storage device

so you can store all that power.

MAREN: Now, after all of these upgrades

and really a total reimagining of their solar racer,

the Stanford team's Black Mamba

came into the 2019 World Solar Challenge

at a sleek 180 kilograms.

Its single fairing asymmetric bullet design

with a 3.56 square meter single junction

thin film gallium-arsenide solar array

and 45 amp lithium-ion battery

pushed Mamba to a top speed

of around 110 kilometers per hour.

That is highway speed.

Unfortunately, Black Mamba didn't hit top speed in Australia,

because as the Stanford team learned the hard way in 2019,

having a good battery to motor connection

is absolutely critical.

JULIA: We managed to get the battery out of the car

before anything else really caught on fire.

CAMERON: When lithium-ion batteries go,

they go pretty violently.

CORI: Lithium-ion technology

is definitely a dangerous technology.

If you do have a short, you can get a battery fire

because things will just propagate really, really quickly.

Which brings us to the next two chapters

of our Light Speed Learning Playlist,

where we're gonna take a deep dive

into the wonderful world of batteries.

First up. How do lithium-ion batteries work?

Click the link to find out, or just let this playlist play.