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  • MAREN: Timeline time.

  • 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.

MAREN: Timeline time.

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Under the Hood of a Solar Race Car

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    林宜悉 posted on 2021/01/06
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