Daniel and Kelly’s Extraordinary Universe - How can we keep solar panels clean on Mars?

Episode Date: July 27, 2023

Daniel and Kelly talk about how to keep solar panels bright and powerful when they far away on a dusty planet.See omnystudio.com/listener for privacy information.

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founding partner of IHeart Women's Sports Network. Hey, Kelly, how are things running on the side? science farm. Pretty well, but our house is like over 100 years old, so there's the usual number of issues that you'd expect from a house of that age. And so who's the like fixer-upper in your family? Is it the biologist or the cartoonist? Oh, it is absolutely the biologist. I have a series of Twitter posts actually where I secretly record Zach trying to use tools. And each video is better than the last. Every time a contractor comes through and is like, ma'am, where is your Should we discuss this with him?

I laugh out loud because, because Zach, he's just not interested in this stuff at all. So, all right, how about in your family? Is it, so let's see, you're an experimentalist. So does that make you the one who's handy with tools? Ooh, I wish. Technically, I'm an experimentalist, but in practice, I do more computer stuff. So that means I fix, like, the broken laptops and the iPhones. Like in your family, my wife is much more hands-on than I am.

And so is she the one who usually? is doing the fixing. She's actually too busy fixing stuff in her lab to fix stuff around the house. So we don't really have anybody fixing stuff. So what do you do when the stuff breaks? Stuff doesn't just not break because there's no one available to fix it. I've learned that. Our strategy is to live with it as long as possible.

The house is pretty new when we moved in. And so we're just going to see how long that works. This is a horrible plan, Daniel. Houses are not disposable. You can't just break it down and then move out. We'll see. Good luck. Hi, I'm Daniel.

I'm a physicist and a professor at UC Irvine, and I'm not good at fixing broken stuff. Hi, I'm Kelly Weiner-Smith. I am adjunct at Bryce University. And if I didn't fix things, the house would fall down around us. It sounds like you're going to be actually useful when the end times come. I hope so. You know, Zach Gardens, so he might be useful when the end times come.

We joke about the apocalypse a lot. But we're pretty sure that when it comes to self-defense, we're goneers. I pretty much have no useful skills. I mean, I can write programs. I can record podcasts. I can think deeply about the nature of the universe. But, you know, none of that's going to translate into like whiskey or gold in the end times. Yeah, no, so you, like, probably wouldn't make it to the second season of The Walking Dead.

I like to think that I'd still be around on The Walking Dead, but I'm not sure. I'd have to get good with the sword or something. You know, the Walking Dead actually does teach people to survive. There's this incredible story about a young woman in Irvine who's attacked in a parking garage in real life by a huge ex-Marine. And she managed to wrestle the blade away from him and kill her. attacker. And when they asked her how she managed to do that, she said, I watch the walking dead. I know it's kill or be killed. Oh my gosh. But I mean, she must have, like, she must work out or have had some prior martial art training or there's got to be more to it than I watched

the walking dead. Because I've seen it all. Turns out there's a lot more grit in Orange County than you might expect. I guess so. I believe it. That's incredible. But speaking about grit and survival, humanity needs to have a sustainable way to live here on Earth and out in the solar system. And on this podcast, we like to think about the future, but what science and technology hold for our future exploration of our neighborhood. So welcome to the podcast, Daniel and Jorge, Explain the Universe, in which we talk about exactly those things, how the universe works, how it all comes together, and how we can take advantage of our knowledge of physical laws to build ourselves a sustainable life here on

Earth and perhaps also on neighboring planets. Thanks very much, Kelly, for being a guest host on today's episode. Thanks for having me back. I always love being on the show. And I always love talking to you about fancy technology in space because you bring that bracing dash of skepticism. Yes, everybody loves to have the wet blanket around. I'm glad I'm appreciated somewhere. Well, you know, it's fun to blue sky think about what might be possible, but if we're actually going to make it out into the solar system. If we're going to send our probes and one day our children out into deep space, we better have stuff that actually works that somebody has actually thought through and maybe even tested. Well, you know, you need the wet blankets to put out the fires. And so that I

offer a service I like to think. And fire turns out to be quite essential. We use it here on earth to keep ourselves warm and also to transform various kinds of energy into electricity. We have mammoth amounts of coal and gas still being burnt to turn steam turbines to convert it into electricity, as well as huge amounts of the planet covered in solar panels to generate electricity for our lifestyle. But when we send our robots into outer space, they don't necessarily have access to coal-fired power plants. So they need to think about other ways to stay warm and keep running. And the environment of space is a tough one. As we've talked about several times on the podcast.

So on today's episode, we're going to think through some of the details of how our little robots can keep chugging away on the surface of alien planets. More specifically, on today's episode, we'll answer the question. How can we keep solar panels clean on Mars? But maybe we should start closer to home. How do you keep your solar panels clean, Kelly? I don't. You can't just let these things break in.

and move on. Oh, you know, it's possible I'm a bit of a hypocrite sometimes. Actually, while I was thinking about today's episode, I realized that I have never cleaned the solar panels that are up on top of one of our barns. I just don't know how I'd reach them. But we do live in a dusty, you know, we've got Virginia dusty clay.

So I guess I just hope it rains a lot. And it does. Don't you have small children? They're good at climbing and their little fingers are great at cleaning tiny little electronics. Yes. No, absolutely. And I haven't read the child labor laws to know if I'm allowed to do this or not. But probably it's fine. And so maybe that's what they'll do this weekend. Well, I hear there are loosening labor laws all across the South. So maybe soon your children can legally work for you. Yay, thank you, politics.

So if Kelly can't even keep her solar panels clean on Earth, how it could be possible for NASA to keep solar panels clean on Mars, a famously dusty and very distant environment where there aren't even child laborers available to clean those little robots? Gosh, I hope we can fix that one day. That's why we have to send people to Mars starting with children. Yes, absolutely. But we reached out to our audience to ask them if they had thoughts

about how to keep solar panels clean when they are thousands and millions of miles away and also essential to the operation of remote robots? If you would like to answer questions for this segment of the podcast, please don't be shy. We would love to have your voice on the podcast. Just send me an email to Questions at Danielanhorpe.com, and I will set you up. So think about for a moment. Do you have clever ideas for how to keep solar panels clean on Mars? Here's what people had to say.

You know what? That's a good question. The rover has got a lot of batteries. It's not solar powered. It's not solar powered. That's why. I would say that the reason why they don't have wipers is because we would have to probably have fluid to spray on the solar panels to wipe and clean. And that's probably just too much to do with the rover.

I've never really thought about that. My guess is that using a regular wiper would scrape the lens. I'm guessing they blow the dust off with some type of compresses. air system. I don't know. That's a really good point. Maybe the solar panels have a self-cleaning technology like self-cleaning glasses that are available in civil construction. Hmm, I don't know. If it's dry, maybe that would just scratch the lenses. Maybe you need like the film that just keeps replacing itself. I thought these were really great answers. The listeners identified a lot of the actual big problems and had some good ideas. And to be honest, I have.

hadn't heard of self-cleaning window technology. Do you know about this, Daniel? Do you know how it works? I'm not an expert in self-cleaning windows, but later in the episode, we're going to talk about self-cleaning solar panels. This is actually technology people at MIT are working on. Oh, very cool.

So you're right, our listeners are on point. These are some smart people we have listening to the podcast. And good looking, too. Yes, that's called the Halo effect, I think. Yeah, I bet they're also good at video games. and probably very fast. Do you think correlation implies causation, like the more episodes of the podcast you listen to, the better looking you are?

Yeah, no. And I hope that if I co-host enough that I'll be even more good looking than just listening. So that's what I'm banking on. I'm not here just because you're fun to talk to, Daniel. I'm not sure. It might go the other way. You know, if we have faces that are good for podcasting, it might just mean that they get better and better for podcasting.

Daniel, I'm sorry I have to go. It's been fun, but I'm doing something else with my time. All right, but we do want to keep our little robots powered on alien planets. I mean, we send these devices off to Mars to measure earthquakes, to gather samples, just to drive around and see the geology and understand what used to be on Mars, maybe even discovering water, evidence of life, or potentially even existent life on Mars. The questions are still open. And well beyond Mars, we send things to other planets.

We'd like to drive them around and even fly them around those planets. And for all these things, they need power. None of this stuff comes for free. And we need to get really good at this stuff if we're ever going to have humans living in space because you really can't have your power ever break down if you're living in space. That's right. In space, you can't just wait till your space station breaks down and then move out into another one. Space stations are not disposable.

Well, I mean, we've burned a lot of them up in the atmosphere, but you better have another plan before that happens. Yeah, we like to do some repairs before we recycle. But solar power actually isn't the only way to power some of these distant devices. How else do we do it, Daniel? Well, another option is really fascinating are nuclear batteries. And if you want to power something for a long, long time, you need a steady source of energy, then you definitely don't want to bring gasoline along.

You want a very, very dense source of power. You want some kind of fuel that releases a lot of energy and doesn't have a lot of kilograms. And so in the same way that we power like our aircraft carriers and our submarines, we turn to atomic physics to produce that energy. You know, that aircraft carriers can go for like decades without refueling because they have nuclear power plants on board, like fully functioning fission reactors on board, turning uranium into electricity. Same with submarines sliding around the Earth's ocean. It's really pretty amazing. I think it would take me a little while to get used to knowing that I was living that close to a new. nuclear reactor. On the other hand, it would be good to know that you have a reliable power source.

But these things are delicate and dangerous, and you can't put a whole nuclear power plant on a satellite or on a little rover that's going to be driving around the surface of Mars. Instead, they have a different way to extract energy from radioactive elements. These things are called RTG's radioisotope thermoelectric generators. Basically, it's a big block of material which decays radioactive. and turns the heat from that decay into electricity. So that's one of the ways that we can power things in space. Kelly, you're something of an expert in the history of nuclear power and space.

Have humans ever launch an actual working fission reactor into space? Oh, man. We've done it more times than you're probably comfortable knowing. More than zero is more times than I'm comfortable knowing. Yeah, exactly. And so in 1965, the U.S. did it for a satellite. It was like a test and it didn't go great. then we boosted it into a graveyard orbit.

So we actually have one of these reactors still orbiting the Earth. But the USSR loved these. They did it a bunch of times. I think they sent up 33 or maybe even more of them. And so, yeah, there have been a lot of little nuclear reactors that have been sent to space to power our satellites. I don't think any of them have gone to like Mars or the moon to power rovers, but we do have some experience with using these as satellites.

Also, fun fact, if your definition of fun, is raining nuclear waste over the earth. One of the USSR's satellites that was powered by a nuclear reactor, this one's called Cosmos 954, accidentally re-entered when it wasn't meant to re-entered, and it sprayed nuclear material all over Canada. The U.S. and Canada had to clean it up. That sounds bad.

It was bad. Russia agreed to pay for half of it. I think it's the only time in which the Liability Convention through the United Nations has been invoked. as a like, dude, this is kind of your responsibility. And I think the Soviet Union tried to be like, well, it's hard, maybe not. But eventually they went havesies with us. Well, sending working fission reactors into space doesn't seem like a great idea.

But fortunately, these other devices, the radioisotope thermoelectric generators, are simpler solid state devices. They don't have any moving parts. They can't like melt down. Basically, you just have like a block of radioactive material, which is decaying, and releasing energy as those decays happen, which heats up the block, and then you just got to turn that heat into electricity. Yeah, and most of the time, you don't end up with, for example, one of the lunacods breaking up

over the Soviet Union and sending polonium all over the place when they're radioactive. What is it? This was a thermoelectric generator that broke up and, you know, dropped waste over the USSR. You're right. This is definitely a danger. If you are launching radioactive materials, whether it's for an RTG or for a working reactor, you're risking blowing that over the surface of the Earth at launch because launches are still violent and risky events.

No matter how good we get at it, sometimes these things still blow up. And if your payload is dangerous, then that presents a danger to the population on Earth. There are ways to make it safer. You know, there's like new cladding that you can get and you can send up smaller and smaller amounts on different rocket launches and then put them all together when you get to space. But certainly our history is littered with radioactive accidents. So these things are dangerous. They're also super duper expensive. I mean, often they use like plutonium 238 for which we have a very limited supply because until recently we stopped making plutonium. And so it's not easy to get this stuff. If it blows up on launch, it's very dangerous. On the flip side, it lasts for a long time. Like you can build one of these things and it will steadily produce power for 10 to 15 years. Just pumping out electricity. It doesn't require the sun. There's no moving parts. It's very, very. very stable. So these things are sort of the gold standard for NASA if it wants to power something

that goes to like the outer solar system where even solar panels are not going to be effective because you're so far away from the sun. Well, and I got to say, if I was moving to Mars, I would really like to have a tiny nuclear power plant on Mars rather than relying on anything else. And there are engineers working on it and they all really like the Simpsons and they name all of their designs after Simpson's stuff. Oh, no. So what, let's see, In 2018, they tested the kilopower reactor using sterling technology, and by, like, picking the right letters out of those various words, they come up with Krusty and, like, the clown. I think they also had one called Duff, like, after Duff Beer.

And anyway, one of the engineers has been at this for, like, decades. But anyway, it is a nice, reliable power source if you could get it to work safely. It is very cool, and it uses an interesting effect where you turn heat into electricity by having two different kinds of metal. One is hotter and one is cooler, and that generates an electromotive force across them. Basically, like the electrons and the hotter side are moving more, and the electrons in the cooler side are not,

and that creates a flow of current across the threshold. And so you can turn this heat into electricity, again, with no moving parts. You don't need, like, a steam engine or a turbine or anything. It just produces electricity. And, yeah, if I was living on the surface of Mars, I would like a backup source of energy, especially if it didn't come with me to Mars, they're like landed separately, so I didn't have to worry about radiation from it if it broke down.

Yeah, no debt. Well, and also there's, you know, lots of reasons in space why you'd like to have heat and these reactors also produce heat. So you could, you know, I don't know, maybe heat up your ice and turn it into water. But because these things are expensive and they are dangerous and they're also in limited supply, NASA tends to be pretty stingy with these things. They reserve them for like the deepest, longest, high priority, lowest risk missions. And so when people started talking about putting a rover on Mars, the Mars program wasn't really in great shape that had a bunch of losses. They seemed very high risk. They were thinking these rovers were only going to cruise around for like a few weeks at most.

So they didn't have the option of using one of these nuclear batteries and they had to go for solar panels. And after the break, we'll tell you about how those were. Imagine that you're on an airplane and all of a sudden you hear this. Attention passengers. The pilot is having an emergency, and we need someone, anyone to land this plane. Think you could do it? It turns out that nearly 50% of men think that they could land the plane with the help of air traffic control. And they're saying like, okay, pull this, until this. Do this. Pull that. Turn this. It's just... I can do it my eyes close. I'm Manny. I'm Noah. This is Devin. And on our new show, no such thing. We get to the bottom of questions like these.

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to judge. It is so expensive in these streets. I 100% can see how in just a few months you can have this much credit card debt when it weighs on you. It's really easy to just like stick your head in the sand. It's nice and dark in the sand. Even if it's scary, it's not going to go away just because you're avoiding it. And in fact, it may get even worse. For more judgment-free money advice, listen to Brown Ambition on the IHeart Radio app, Apple Podcast, or wherever you get your podcast. I had this like overwhelming sensation that I had to call it right then. And I just just hit call, said, you know, hey, I'm Jacob Schick, I'm the CEO of One Tribe Foundation, and I just wanted to call on and let her know. There's a lot of people battling some of the very

same things you're battling, and there is help out there. The Good Stuff podcast, season two, takes a deep look into One Tribe Foundation, a non-profit fighting suicide in the veteran community. September is National Suicide Prevention Month, so join host Jacob and Ashley Schick as they bring you to the front lines of One Tribe's mission. I was married to a combat army veteran, and he actually took his own life to suicide. One tribe saved my life twice. There's a lot of love that flows through this place and it's sincere. Now it's a personal mission. I don't have to go to any more funerals, you know. I got blown up on a React mission. I ended up having amputation below the knee of my right leg and a traumatic brain injury because I landed on my head. Welcome to season two

of the Good Stuff. Listen to the Good Stuff podcast on the IHeartRadio app, Apple Podcasts, or wherever you get your podcast. Hello, it's Honey German And my podcast Grasas Come Again is back This season we're going even deeper Into the world of music and entertainment With raw and honest conversations

With some of your favorite Latin artists and celebrities You didn't have to audition? No, I didn't audition. I haven't audition in like over 25 years. Oh, wow. That's a real G-talk right there. Oh, yeah. We've got some of the biggest actors,

musicians, content creators, and culture shifters sharing their real stories of failure and success. You were destined to be a start. We talk all about what's viral and trending with a little bit of chisement, a lot of laughs, and those amazing vibras you've come to expect. And of course, we'll explore deeper topics dealing with identity, struggles, and all the issues affecting our Latin community. You feel like you get a little whitewash because you have to do the code switching?

I won't say whitewash because at the end of the day, you know, I'm me. But the whole pretending and code, you know, it takes a toll on you. Listen to the new season of Grasas has come again as, part of My Cultura Podcast Network on the IHartRadio app, Apple Podcasts, or wherever you get your podcast. Okay, so we've decided that nuclear power is reliable, but it's expensive and sometimes things go wrong. And one way or another, solar panels are really popular on space voyages. So how about you tell us a bit how solar panels in space were? Yeah, solar panels in space work the same way the solar panels do here on Earth, which is essentially transforming the energy of the photons into current.

And photons interacting with electrons is, of course, very famous in physics. It's the basis of the photoelectric effect for which Einstein won the Nobel Prize more than 100 years ago. When photons hit a piece of metal, they don't just interact with the whole metal, and they're not classical electromagnetic waves where they deposit their energy broadly. or they come in terms of photons, which means that a single photon hits a single electron and deposits its energy. The photoelectric effect is when there's so much energy in that photon that electrons boil off the surface. Like you can knock electrons off of a piece of metal by shining high energy light at it. So that's the photoelectric effect. The photovoltaic effect is the principal underlying solar panels, and it's the sort of like lower energy cousin of the photoelectric effect.

If you dial down the energy of the photons so that they don't have enough energy to kick the electrons out of the metal, you're not boiling electrons off the surface. Instead, you're just exciting the electrons. You're giving them more energy so they can flow around. And then how do you get energy out of them flowing around? Yeah, so you need to build a special kind of material. So here we use silicon diodes. And silicon, remember, is a semiconductor. So it's not quite an insulator where all the electrons are like trapped in the lattice of the crystal.

It's not quite a conductor where there's no gap between where the electrons live in the crystal and where the electrons flow freely. So electrons are just zooming everywhere. A semiconductor has like a little bit of a gap there. So it's like hard for the electrons to flow, but not impossible. And if you put the right kind of materials into the silicon, if you dope it with other kinds of elements, then you can subtly tune the size of that gap. So a diode has two different kinds of silicon in it. They call it N-doped and P-doped.

N-doped silicon has like extra electrons in it. It's end-doped, it's more negative. P-doped silicon has more positive charges, basically has holes for the electron. So you have these two kinds of silicon next to each other, and you apply an electric field to keep the electrons from flowing from the N-side to the P-side. So it's sort of like having a bunch of water behind a dam. Then when the photons come in, they push some of those electrons basically over that ridge, and they flow across the material.

And that creates a current, and that's what you want. The current is your electrical energy. So he turns those photons into motion of electrons across the silicon, which then adds the voltage on your battery. I did not know that. And I'll also note that I've never heard the word dope using a scientific context. And it's great.

I actually feel like I should write a song, maybe like a rap song about how diodes work. Maybe not. Maybe let's pull that out. Doping is for Smarty Pants, it turns out. That's right. That's right. I was thought of it doping more in the Lance Armstrong sense than in the like, you're a dope sort of a sense.

Well, no, so you're a dope is like negative, but I was thinking of it as like, that's dope, man. Oh, I see. And when I said it, it sounded incredibly uncool. So anyway, this is where I am in the universe. No, silicon is definitely dope material, yeah. Right. Okay. So now we know how you get energy from it.

Is this like a good way to do it? Yeah, it's a pretty good way to get energy out of the photons. It's frustratingly not 100% efficient. Some of the energy is lost just to diffusion and just to heat. It's not all directly converted from the energy of the photon to the energy of the electron. They have like research systems where they try to optimize all the conditions and they can get it up to like maybe 45 to 50%. That's like the record in research. In terms of the photovoltaic panels like on your house or on big power plants,

they're typically like 20% efficient, which means like 80% of the energy is just lost. You know, stuff gets heated up, but it's not ending up in your battery. That's interesting. And of course, as a biologist, what I'm wondering is how far behind are we lagging nature? So, you know, photosynthesis is all about capturing the sun's energy. How efficient is photosynthesis? Weirdly, photosynthesis is a lot less efficient. It's something like 3% efficient, yeah, compared to the photovoltaic method.

Come on, evolution. You're letting me down. But photosynthesis is pretty awesome because, you know, it builds itself, right? Like my solar panels aren't making more solar panels. And in addition, as you know, like it turns the energy of the photons into like complex chemicals that store energy. It's much, much better than a battery, right? It's like it's literally creating fuel out of sunlight. Whereas all we can do is like convert it into electricity, which then stays in a battery. And that's hard to transmit across long distances.

etc, et cetera, et cetera. So plants are doing something that we're definitely not doing. All right, evolution. I'm sorry about what I said about you. Let's be friends again. On the other hand, photovoltaic cells can use like infrared light and UV light. They can use a broader spectrum, whereas plants mostly get their energy from the visible spectrum.

So there's pluses and minuses. But yeah, I would like free solar panels that grow themselves and maintain themselves. That would be pretty awesome. That would be solid. And if you were starting a settlement on Mars, that would really give you a leg up. But we don't know how to do that yet. But speaking of Mars, so, you know, on Earth, we're closer to the Sun than Mars, which probably helps with gathering energy.

What is the situation like on Mars? It's farther out. So how much less sunlight does it get? Yeah, Mars is much further out than Earth. So the solar energy is like a corridor of what lands on Earth. But, you know, it's closer than a lot of other planets. You want to send something to Uranus or Neptune. By the time you get out there, the sun is a distant dot in the sky and is really very little

solar energy. So Mars is in a pretty good spot for solar panels because it's close enough to really be able to gather some energy. And when they were building the first rover, that's what they went with. Sojourner in 1997 was only supposed to last for like seven days or seven souls, actually. So they didn't even ask for like a nuclear power plant that would last for 10 or 15 years. I thought that would be a waste. And this was a very experimental technology. So they put a little solar panel on top. And that little guy well outperformed its mission. Instead of only going for seven souls, it worked for 83, and it traveled up to 100 meters. This was like the first time people are really driven around on an alien planet. It was pretty awesome. That's totally incredible. And so since then,

how many of our rovers have used solar? Spirit in 2003 also used solar panels, and it went like eight kilometers before getting trapped in the sand. Opportunity in 2003 was amazing. It lasted for 5,300 souls and drove 45 kilometers until dust storms blocked its solar panels. I got to be honest, I'm not like a very sentimental person. I don't cry very often. But when I read about some of these rovers, I get like kind of choked up. Like when Curiosity landed, I remember watching the landing and like shedding the single tier. I feel like some of this stuff is just like the best humans have to offer.

The fact that we've managed to land a rover and then operate it for 5,300. hundred souls is just like amazing. So sorry. Okay. Opportunity. Yeah, opportunity was great. And by then the Mars rover program had really sort of earned its strike. People believed that it could work and that it could last for a while, that you weren't sending something up there that was just going to drive around for a week. So Curiosity actually has a nuclear power plant. And that's one reason why it's still going. Like, it doesn't matter how dusty it is or what the weather is like on Mars. Curiosity gets its power from its nuclear battery. Nice. And I think some of the that have solar also have radioactive heaters.

They're not like thermocoupled to generate electricity, but you still got to, it gets pretty cold up there. Exactly. And Insightlander, which doesn't have a rover, but is operating on Mars and doing a bunch of science, it also has solar panels. And they have to worry about keeping them clean. Perseverance, which landed in 2020, which is the one with a helicopter on top, that one also has a nuclear plant.

So these days, we still see some with solar panels, but it's sort of transitioning to the nuclear power plants because these are longer-lasting, lower-risk missions? I'm probably being too picky. Are those power plants or are those thermoelectric generator couplers? No, you're right. These are not fission plants. These are like nuclear batteries. These are RTGs.

So when we were writing our book about space settlements, I was super surprised because I don't think I had really absorbed the magnitude of the dust storm problem on Mars, which of course is going to be majorly bad for solar panels. Can you tell us a bit about the dust problem on Mars? So dust is really a big problem on Mars and a big problem for solar panels in general. Even here on Earth, dust storms are a big issue. Like there are big power plants in the deserts like in the UAE that produce like 10 megawatts. But they estimate that dust storms in the desert have reduced production at those facilities by like 40%.

In order to clean them, they need water because you've got to spray them clean. you can't scrape them clean or you'll scratch them. So it takes a huge amount of water to clean these desert solar panels. They're currently estimated cost like 10 billion gallons of water per year just to keep those solar panels clean. Oh my gosh. And that's got to get pumped in from somewhere. It's crazy.

And, you know, for a really big solar installation, even like a one or two percent reduction results in a huge loss in annual revenue. Over the life cycle of these plants, it can be like billions of dollars. And so for most of these facilities here on Earth, the cost of keeping it clean and just keeping the dust off of the panels is about 10% of the operating cost of these facilities. So it's interesting. What we were writing our book, an argument we came across often was like, well, we'll figure out how to do this stuff when the stakes are high. So, you know, like, we'll figure out how to clean the solar panels on Mars. But apparently the stakes are already super high on Earth.

Like, this is tons of money that's being lost. It was just like finding a slightly better, like, rag so you could buff off the dust. Presumably, somebody would have, like, spent the money on that already. But anyway, okay, wow, I didn't realize the scope of the problem. Yeah, well, ironically, it's kind of good news for space exploration. That's also a problem here on Earth because it means that, like, big money players are going to try to solve this problem. You know, it's just like in particle physics, when we need to invent something fancy and new, we always look around to see, like, hmm, is some other huge. industry invented this already for other reasons.

You know, like we use GPUs in our machine learning at the Large Hadron Collider. GPUs that were invented for like making Call of Duty a better video game, right? Not for unraveling the secrets of the universe, but turns out they're awesome for inverting matrices and solving machine learning problems. And so, you know, this is a well-worn path in science. Remember, like, the NSF's entire budget is a tiny fraction of the amount of money people spend on like cell phones every year. So if you can get like the military or some huge commercial industry involved in your physics problem, then probably they're going to solve it for you in

about 10 minutes and come up with a really cheap solution. And so fortunately, there are a lot of people working on ways to keep solar panels clean, especially here on Earth. And we hope that some of those might translate to Mars. It sounds like at the moment we don't have a great solution. But on the other hand, Mars does have plenty of water. It's not easy to get. It's going to be a bit of pain, but you know, you'd be in a lot more trouble if you were on the moon, for example. Yeah, that's true. But Mars also has a whole lot of dust. I mean, there are these huge dust storms that can like choke up Mars for weeks at a time. Anyway, solar panels on Mars face a very similar problem to solar panels on Earth. The wind is going to blow. Dust is going to block it.

And as the dust blocks the solar panels, the energy output drops. And if you're driving your rover across the surface, you got to keep those panels clean. People might remember in the movie the Martian. He spent a good fraction of his day, washing his solar panels to keep his energy production up. Stressful. You went through and you talked about a bunch of rovers that sort of extended their stay longer than we thought that they would. In the end, for a lot of them, was dust, the thing that killed them? In the end, it was. Yeah. Now, Spirit got trapped in the sand, unfortunately, so it wasn't a solar panel issue. But like opportunity, it was a dust storm that blocked its panels and basically killed it.

It couldn't stay warm and it couldn't keep moving. The same thing for the Insight lander. Mars is far enough way that you can't just sort of like send someone out there to brush something off if you get a dust storm that you didn't expect. If you're not willing to send your kids to climb up on your barn, you're definitely not sending them to Mars with a brush. Probably not. So let's take a break and then talk about methods that we've come up with so far

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in fact, it may get even worse. For more judgment-free money advice, listen to Brown Ambition on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. Okay, so we have some experience with trying to keep solar panels clean on Mars. You know, we've sent up enough rovers that we've probably learned a thing or two.

So, Daniel, what do we do now? And we just hope that there's no dust storms that take out our rovers or can we be proactive? Yeah. Thoughts and prayers don't really work very well when it comes to keeping your mission going on an alien planet. You know, I come back to what the listeners were mentioning. You might imagine, like, let's just put a rag on the thing

or, like, put a mechanical arm with a brush to wipe stuff off. But as people mentioned, like, it could scrape it. These solar panels have a delicate surface. And if you scrape it, it's going to reduce the absorption and then also be a way for dust to gather, right? You're creating little valleys that are going to grab the dust out of the air. And you really don't want anything like mechanical on your rover as much as possible. You want to keep it simple because, you know, things that turn and grind, they're going to break.

They're prone to failure. And dust on Mars is particularly tricky because it's really, really small. Like there's sand and grit, but the actual dust is sort of like particles of smoke. It's hyper fine. And so in order to brush that off, you need a brush that had really, really, really fine. bristles. Otherwise, you're just going to slide right over it. So it's really a tricky problem. So if you send your kids out there, they should have a really good ventilator. That's the lesson, I think. One of the listeners suggested like an air compressor. Could you send the rover with like

an air compressor and like blow it off? You might be able to. I mean, people have talked about like helicopter blades blowing things off the solar panels. And we do have one helicopter on Mars. Remember that the atmosphere is very, very thin. And so hell, helicopter blades don't produce a whole lot of wind. And so that sort of seems very dangerous. In terms of air compression, you know, you're either going to have to bring compressed air or you're going to have to compress it, which takes a lot of energy. And so you're probably not going to, in the end, win by compressing your own air.

So we've struck out a few times now. What are some other options? But, you know, these little guys on Mars have lasted for a long time. So you might wonder, like, how is it possible to keep going for 5,400 days? There are a couple of tricks. One of them basically is thoughts and prayers, which means waiting for wind because, you know, there are storms on Mars, and sometimes those Martian storms will, like, deposit a bunch of dust on your solar panels, and sometimes they will blow it clean.

It's got to be amazing to have spent, like, a decade of your life planning a project and then hoping a breeze comes by so that you can keep collecting data. A breeze comes by on Mars. But, okay, so breeze is work sometimes. Yeah, and spirit and opportunity. both of these relied on breezes for years to keep things clean. The Mars Pathfinder mission, unfortunately, didn't benefit from such winds and its solar panels got blocked and never recovered.

You know, that's the tough thing about it is like if you go down to zero and get too cold, things just stop working. So you really can't like stay cold for very long. You need like a consistent source of energy. But, you know, NASA has clever engineers and they've come up with some like really counterintuitive solutions to this problem. One of them is pour dirt on the solar panels. What?

No, no, no, no. That's going to make it worse. All right, how does that help? It's sort of amazing. It's because the soil, the dirt on Mars, has some dust in it, but mostly it's sand. And that sand actually works as a cleansing agent. So you pour like a bunch of the sand on top, and it'll grab those little hyperfine pieces of dust and pull them along with it.

And so you pour dirt on top of it. sand will pull that dust off of your solar panels. And that's less likely to scratch it than like using a rag? That's less likely to scratch it. Here you're also relying on wind. And this is something they discovered accidentally. They have this seismometer on Mars, which is separated from the inside lander. And there's a tether that connects the seismometer to inside itself,

like sends along power and information. And they were trying to keep the tether in place. So they dumped a bunch of soil on top of it. And they noticed that when wind came along, it would blow off the soil and leave its shiny, sparklingly clean. So then they thought, all right, let's try this on the solar panels. And so they, on purpose, dumped sand on top of their own solar panels. I'm like, that must have been terrifying, right?

Like, you make this mistake. There's no going back. But it worked. And it boosted the energy production by like 5%. You imagine telling the funders for this project. Like, no, hear me out. We're going to dump dirt on the solar panels. It's going to be great.

They try to time it for like the windiest part of the day. So basically it's like you're building a little thing to catch the wind, which is going to push the sand along, which is going to grab the dust with it and clean off the solar panels. So it like makes better use of the wind than just waiting for the wind to blow this hyperfine dust away. That is incredible and super smart. But so if I was going to be living in a settlement on Mars, I would hope we'd have a better option than dumping dirt on top of the solar panels.

Are there any more like futuristic options that we're hoping we'll be able to test out in the future? There are people working on ways to clean solar panels here on Earth for all the reasons that we talked about and billions of dollars in research, not just because we want to have our rovers drive around on Mars, but because we want to have efficient energy production here on Earth without spending lots of time, money, and especially water on cleaning them. But they're looking into our solid state solutions, things with no mechanical moving parts. And one of the most promising technologies is called electrostatic cleaning. And it takes advantage of the fact that these dust particles are not neutral.

They tend to have positive or negative charges. You know, it's not that hard to make something ionized. Like the reason you get static electricity when you walk across the floor or when you rub a balloon against your head is that you're like stripping electrons off the surface of the material. So, you know, these electrons in some cases are kind of loosely held. And so dust is like flying around the atmosphere in Mars and ends up losing some of its charges. So these dust particles are charged, which means you can push them with electric fields. So you would like start from the center and sort of move the electric charge outward to move things off the edges of the panels.

Is that the idea? Yeah. So you actually build oscillating electric fields. You have electric fields that go one way and then another way. And in one configuration, they will push off like positively charged particles. And then you flip it to push off negatively charged particles. The idea is just to like loosen them so then they drift off. So you like loosen the negatively charged particles and they drift away.

You flip it and you loosen the positively charged particles and they drift away. And this process of oscillating the charges is actually a little bit violent for the uncharged particles. And they can end up stripping them of their electrons charging them so that they can also then get pushed away. that good or bad? That's good, right? So you want to push away the negatives and the positives and the neutrals. So you flip the electric field so you get the positives and then the negatives. And in the process, you convert the neutrals to either positive or negative so they can get flipped off in the next cycle. Nice. Got it. Awesome. And how have we been able to try something like this on earth yet? So this technology is under development in research settings. And what they're working on

is like minimizing the amount of electrical current that's needed. Just like with the air compressor example, you don't want to develop a system to boost your energy, which costs more energy than it saves, right? And so in the case here, they're focusing on using a very small electrical current and one that only needs to be applied for like a couple of minutes every day in order to boost the overall electrical generation power of your system. Nice. I like it. This is clever. All right, maybe you can get me to move to Mars. What else do we have? This involves also like treating the solar panels with like a few nanometers of special material to cover. the glass and then applying a voltage across that. There's other systems that have like a little metal bar that passes over the panel, though that's mechanical so it's less attractive. Otherwise, people are working on systems like vibration. Like instead of blowing something on it or brushing something across it, these are tiny and little hyperfine particles. What if you just like shook them a little bit? You know, very, very gently shook them. Could the dust just like fall off? I feel like I would worry that over time the panels would hold up less well if they're constantly

being slightly vibrated. But I'm sure someone's thought of that. No, you're right. That definitely is an issue. I mean, anytime you're like shaking your system, you're going to be like loosening connections and something that you don't want to shake off might shake off one day. But in test, this works pretty well for like the bigger pieces. The very, very fine particles don't tend to get shaken off as well using the vibration system. But, you know, people are working on this and people are working on lots of other different directions. It's definitely a big area that people are exploring because we want to be powering our devices. We want them to last as long as possible.

You spend like hundreds of millions of dollars developing this thing and people's entire careers are focused on the questions that might be answered. You don't want it to go up there and then get blocked by a dust storm in like week two and then it's over, right? You definitely want something beyond thoughts and prayers. Absolutely. Well, in more long term, if you've got humans living on Mars, you don't want them to have to spend all their day cleaning the like many football fields

worth of solar panels that you're going to need to run your settlement. Although, you know, children have to have something to complain about, or does it really count as a childhood? You know, they can be maintaining the cricket ranch for the protein. They'll have plenty to complain about if they're living on Mars. Yeah, that's true. Children are creative. They'll always find something to grieve about. Mommy, these crickets are too spicy.

You're lucky you've got any protein. That's right, exactly. So as humans think about how to explore the solar system and how to power our little robotic devices that are going to lead the way and tell us where the most promising places are for our humans to maybe one day build colonies. We want them to keep their power and we want those solar panels crystal clean. As well as down here on Earth, if we're converting ourselves into sustainable sources of energy, we want our solar panels to stay clean and dry without requiring a bazillion gallons of water. Absolutely. This is definitely an area where if the space scientists figure out a solution, it would help the rest of us too. Exactly. And maybe that means that

Our solar panels will eventually be self-cleaning, and neither me nor Kelly will have to get up on the roof and do some squeegee in. You mean my kids. It'll be good that they don't have to go on the roof. Exactly. All right, thanks for joining us in this tour of solar panels around the solar system. We hope they all stay sparkling clean. Thanks very much, Kelly, for joining us today, and thanks everybody for listening. Thanks for having me. Have a good time, everyone.

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