Daniel and Kelly’s Extraordinary Universe - The Quantum Physics of Solar Panels

Episode Date: October 27, 2020

Daniel and Jorge break down the physics and engineering behind solar panels Learn more about your ad-choices at https://www.iheartpodcastnetwork.comSee omnystudio.com/listener for privacy information.

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Embarrassingly, I don't. You don't? Why not? I just haven't gotten around to it yet, is the honest truth. kind of an energy barrier there? I know, I know I should do it, but you know, prices keep falling and I guess that's what I say to myself to justify my

laziness. Oh, man, you're just cheap. Well, would you get solar panels if they cost pennies, or if they could repair themselves and automatically reproduce? Well, that's an offer so powerful I could hardly refuse. Hi, I'm Jorge. I'm a cartoonist and the creator of PhD comics.

Hi, I'm Daniel. I'm a particle physicist. And like you, I have a to-do list that's too long. Welcome to our podcast, Daniel and Jorge Explain the Universe, a production of IHeartRadio. In which we talk about all the things that are amazing about the universe, all the places our curiosity has taken us, all the questions we have asked and all the answers we have found so far. But we love to talk about the questions that we have and the questions that you have, the things that you are curious about the universe. Yeah, we like to take you to the far reaches of the cosmos to other galaxies and inside of black holes. But we also like to take you to your neighborhood, to the world around you, and talk about the things and the questions that we have in our everyday lives. Because physics is everywhere. It's not just out there in the center of black holes and the craziness of neutron stars.

It is right here making our lives better. Or maybe Jorge, you'd say this is engineering. Yes, yes, I would say that. Or maybe finally, this is physics and engineering working harmoniously together. Yeah, because as humans, we've made a lot of technology and a lot of progress and science and knowing how things work to the point where we can create things that take advantage of nature to make our lives easier. That's right, because the universe is out there pumping out energy into space,

these crazy nuclear bombs going off at the center of every solar system. And so, of course, it's tempting to potentially take advantage of that. Yeah, so today we'll be tackling a question that a lot of readers have sent in, right, Daniel? That's right. A lot of folks see these things on the roofs in their neighborhoods, and they wonder, how does that work? What's going on in there? So today on the program, we'll be asking the question, How do solar panels work?

It's a really fun question because you see these on the roofs in your neighborhood, and you know they generate electricity. but how does it actually happen? I mean, we know the sun pumps out energy, but how does that turn into zippy electrons in your iPhone battery? I have solar panels in my roof. It's amazing. I haven't paid an electricity bill in like years.

In fact, the electric company writes me checks for how much energy I produce. So you are the electric company now. Yeah, I am my own electric company, yes. Yeah, no, it's pretty awesome. I mean, you invest in it and then it pays off over the years. Yeah, and it makes a lot of sense. because in the end, the sun is the direct source of almost all the energy we use here on Earth.

Even fossil fuels originally just came from energy from the sun. And so it's tempting to say, hey, let's just go direct to the source. Why build a fusion reactor here on Earth when we have a huge one in the center of our solar system? Let's just suck up some of that energy. Yeah, because it sort of feels like a waste almost, you know? Like I think about all of the energy that used to hit my roof before I had solar panels. and all that energy just kind of goes to waste. It just hits the roof and bounces and heats it up a little bit,

but then it cools down again at night. So I feel so much more like I'm taking advantage of nature and using up the energy that's there. Right. So you're not just doing it for the economic benefits. You're doing it because it makes you feel like a better person. Honestly, yeah. I feel like I invested in a more guilt-free lifestyle. Like in the summer, we can just turn on the AC and guilt-free

because it's all coming from the sun. Yeah, and have a second box of cookies, right? Yeah. And you're right, there is a huge amount of energy there. The amount of sunlight that falls on the earth is like 173,000 terawatts. It's incredible. That's a lot of watts. That's a lot of terawatts.

And it's actually a thousand times more than the entire energy budget of our civilization. Wow. Meaning that a thousand times more energy falls in Earth from the sun than we use. Yeah. So if you could capture the solar energy, you could easily power the entire. civilization with just a fraction of the energy that comes from the sun. So it's a huge resource. It's incredibly powerful.

It's right there. It seems awfully tempting to try to capture it. What would be the number, Daniel? So if it's a thousand times more, does that mean that if we cover the earth, one one thousand of the earth in solar panels, we would be set? If it was 100% efficient, yeah. I've seen lots of different calculations, actually, about how many solar panels you would need, but you don't need to cover a significant fraction of the earth in solar panels.

to get enough energy to power the earth. We'll talk about it a little bit more later. One of the biggest challenges actually is getting that power to the right place and storing it and having it at the right time. But it's a big percentage these days or a significant percentage of the power that we consume these days, right? I mean, it's not like zero. It's not like zero.

Here in the U.S., we get about 3% of the energy that we use from solar panels. But in other countries, it's higher. China's 4%. Germany is 8%. Australia goes to 9% and Honduras tops it out at 15%. Wow. Well, Australia is understandable. I mean, everything's bigger in Australia.

And sunnier. Even there's solar panels. Spiders and solar panels. Yeah, but aren't like the kangaroos hanging out on top of the solar panels blocking it? I wonder if that gets factored in. And I guess the great thing about it is that it's carbon-free. Like it doesn't give off any emissions, does it? Yeah, operating the solar panels certainly doesn't.

There's a question of constructing solar. panels and the infrastructure to store that and to create batteries and there's definitely some toxic materials that are used and created there. But operating solar panels, no, they have no moving parts. They just sit there and turn photons into electricity. So they're pretty awesome. Yeah. So a big question that our readers have is how do they work? Like how do they convert solar energy, sunlight into electricity? You can use for your devices and video games and televisions and Netflix. And so we were wondering how many people out there know how solar panels work.

That's right. And so I asked folks who volunteered to speculate without Googling about how solar panels work. And if you'd like to speculate without reference materials on difficult questions in physics, please write to me at questions at danielanhorpe.com. Yeah. So think about it for a second. Do you know how solar panels work? Here's what people had to say.

You know, I've never thought about it. And I have no idea. The panels capture the photons from the sun and store. You know what? It's a circle of life. You know, I don't really know the specifics. I know that they're also called like photovoltaic panels. I don't know if I'm saying that right.

I've only ever seen the word written out, which makes me think it's got to have something to do with the photons specifically interacting with the panel. You know, because I just saw a small presentation last week. So, sunlight activates the panels, the silicon panels, and the cells produce electrical current, which is converted in electrical energy, or no, electrical energy is converted in electrical power. My understanding is that the solar energy hits these panels, and based on that energy, there's some photovoltaics. cells, which translate that into electrical energy, not really sure how. Maybe because of the expanding heat, it creates a differential in different metals.

I know they have photovoltaic cells in them, but I couldn't explain the science behind it. All right. A lot of people seem to have some idea. A lot of people said the words photovoltaic. That's pretty impressive. Yeah, that's pretty awesome. And it goes to the core, the physics that's happening inside solar panels. And I think often they're called photovoltaic cells.

And so that gives people a clue about what's going on inside. Photo, I guess, light, voltaic, just kind of meaning electricity. Yeah. And it is in the end an interaction between photons and electrons. So it makes a lot of sense. All right. Well, let's break it down for folks. How do solar panels work, Daniel?

I mean, I assume they get sunlight and somehow that gets transformed into electricity. So what's going on? Yeah. So there's sort of two steps there. One is, how does the energy get from the photon into the material? And the second is, how can you construct a material that can effectively grab that energy and siphon it off into electricity? And so the first step is called the photovoltaic effect, or a photon hits a piece of material, and it basically passes that energy to an electron. What does that mean?

Like, the electron absorbs the photon or, like, the photon hits the electron? How can I visualize it? the photon is absorbed by the electron. Remember that electrons interact electromagnetically, and that just means that they trade photons. So every kind of electromagnetic interaction, every push and pull by electric fields, is mediated by photons.

So photons are the way that electrons talk to each other and other charged particles. And photons are not eternal, right? They can get absorbed by an electron. Their energy goes right into the electron, and then the electron has that energy. So the way I visualize it is like a photon coming in, meets an electron and then only the electron continues.

So now the electron absorbs the photon and now I guess it's charged up or something. Yeah, it's more excited. Exactly. It's charged up. And there's two different effects here that are very closely related. One is the photovoltaic effect, which is what we're talking about. And the other is something more famous that people might have heard about called the photoelectric effect. They sound very similar and they are very similar. Photoelectric effect is when the photon has enough energy that the electron gets kicked out of the material.

So people saw this about 100 years ago. If you shine light at a material, you'll get electrons boiling off the surface. And that's because they have so much energy, they can leave the trap of the material. Meaning like an electron is orbiting the nucleus of an atom because the nucleus is positive, but now it has so much energy, it just pops out. Yeah, it just pops out. And this photoelectric effect is actually what Einstein won his Nobel Prize for explaining and was one of the key experiments that led us to understand,

that light is not just electromagnetic waves, but actually comes in little particles because we saw these weird relationships between the intensity of the light and the wavelength and how many electrons were boiled off. But we have a whole other podcast episode about that, about how we know that light is quantized made out of these little photons. But that's very similar to the photovoltaic effect. Photovoltaic effect is when the photon comes in and the electron gets enough energy, but not enough to actually leave the material. It gets excited, but it's still hanging out sort of in the same blob of stuff. Oh, I see.

So it's just a matter of whether or not it gets enough energy to pop out, basically. Yeah. And there are some materials where electrons don't have to be isolated to one specific atom. Like the picture you described is correct. You have an electron. It's orbiting a nucleus, for example, although we don't really like to think of them as actually orbiting. It's hanging around quantum mechanically near its nucleus. But in lots of crystals, you have electrons that can flow between atoms.

And so, for example, in semiconductors, you have electrons. You have electrons that are trapped that are around individual atoms. And then if they get enough energy, they can jump up over a little gap into a band where they can move around more freely and jump from atom to atom. Yeah, they sort of float around, right? They're not bound to one atom. They can, you know, hang out. Yeah, they're like social butterflies. They just float around.

They have enough energy. They're sort of like flying high above all of these little gaps. And so that's what happens in the photovoltaic effect that a photon comes in and knocks an electron off. from being stuck around one of the atoms and so they can float around free. Wait, that's the photoelectric or photovoltaic? Photovoltaic is when it knocks it off so it can float around inside the material. Photoelectric is when it gets so much energy that it flies free of the material and out into space. It's like abandons its original family.

Oh, I see. I see. One is like pop out out of the material, like out of like away. And voltaic, it leaves the atom, but it hangs out in the lattice and the structure of the material. Yeah, it's just jumping around from atom to atom floating free inside the material. A photoelectric effect,

it's like totally liberated and may never come back to home. All right, so that's the two effects and the one in solar panels is the photovoltaic effect. Exactly. And so the key thing for solar panels

is to take advantage of the photovoltaic effect because now you have this electron, it's got more energy. If you could grab that energy somehow, if you could funnel it into an electric current, then you could turn effectively

that photons energy into electricity. And so that's why you need a special kind of material. Now, any kind of material can have the photovoltaic effect, your hand or a rock or whatever. When it absorbs a photon,

the electrons that absorb it don't fly off the material, then you're having the photovoltaic effect. You're grabbing that energy into the object. But you need a special kind of material to effectively gather that energy and funnel it off into electricity.

And that's where the silicon diode comes in. Yeah, we had a whole episode about diodes, right? and transistors. Yeah, we did because we talked about how LEDs work. And diodes are like a really key foundational element of modern computing because you can use them to make LEDs and transistors and all sorts of stuff. And it comes from semiconductors.

And that's why silicon is so important to the computing industry because it's the most important semiconductor for building these kinds of things. Right. And it's important because it's kind of a special material, right? Like it has just the right number of loose electrons and it's pretty stable. Yeah, because the electrons have these two different regimes they can be in. A conductor is where the electrons just flow freely everywhere from atom to atom. An insulator is one where the electrons are all stuck around their individual atoms.

And a semiconductor is one that has both. It has the electrons around the atoms and electrons at a higher energy that can hop freely from atom to atom. So that's what a semiconductor is, and silicon is a great example of it. And what happens in silicon is exactly that. The electrons jump over this band and then they can float around free. Yeah. And so that's how you make a solar panel is you use silicon to make a solar panel. And then do you have to like create these different areas where one area is like a P-type and the other one is an N-type? Yeah, you can't just use normal silicon. You need to create something that's going to funnel off the electrons.

So the way that works is that you have two different kinds of silicon. It's not pure silicon. You've added stuff to it slightly to change the behavior. And so you have one kind you called N-type, which has like extra electrons. There are a bunch of electrons floating around that sort of don't have a chair to sit in if you played musical chairs. And another kind where you've added other kinds of materials like gallium or arsenite or whatever. So they're called P-type. They don't have enough electrons. They're like empty spots for electrons to sit in.

And semiconductor physicists, they talk about these things as holes. And they treat them as if they're sort of like positively charged electrons. They think of them sort of like as particles. If you remember we talked about the quasi-particles like things that are not particles, but sort of act like particles. This is a good example of one. It's a hole. It's like a missing spot for a particle,

but it moves around sort of as if it was a positively charged particle. Right. It's like if you had five people for six chairs and they move around and change seats, it's like you keep track of the empty seat, not the people. Yeah. And the empty seat moves like a particle, right? Because if one person slides from one seat to the other,

then the empty spot slides the other direction. It's sort of cool to have that idea in your mind of an emptiness being a thing. Anyway, so you have these two kinds of silicon, the P type that has extra holes and the N type that has extra electrons. And because they match up together, there's the sort of, you know, too much electrons on one side and too many holes in the other. Some of the electrons flow across the junction between them and fill up some of the holes in the other side. And that makes an electric field across them. That's the key thing.

The electrons have flowed in one direction and now they make an electric field going the other way. Right. I think what happens is that the material that has too many electrons loses some of them because they all go to the side that has the holes and now you have like this buildup of too much, too many electrons in one place. And so that creates like a barrier, like something that repels other electrons. Yeah, exactly. It's sort of like, you know, diffusion of temperature. You have a hot thing next to a cold thing, then the heat's going to flow over the cold side. And so you put this N-type stuff with too many electrons next to the P-type stuff without enough. electrons, some of them flow over and you're right, it creates his barrier. So now you have this PN junction. You have the silicon that's all primed to get your photon because what happens when a photon hits this special diode, this combination of P-type and N-type silicon, is that when the electron gets kicked free, it doesn't just wander around loosely. It's now an electric field created by the PN junction that pushes the electron all away in one direction. And then you just have to have

something at the edge there to gather these electrons, these electrons that have the solar energy absorbed so they can move along and create electric current. All right, well, I have some questions about that, and let's get into some of the details in. And also, maybe let's talk about some of the larger issues about solar panels. But first, let's take a quick break. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys.

Then, at 6.33 p.m., everything changed. There's been a bombing at the TWA terminal. Apparently the explosion actually impelled metal, glass. The injured were being loaded into ambulances. Just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged. And it was here to stay. Terrorism. Law and order criminal justice system is back.

In season two, we're turning our focus to a threat that hides in plain sight. That's harder to predict and even harder to stop. Listen to the new season of Law and Order Criminal Justice System on the IHeartRadio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Oh, wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, it's back to school week on the OK Storytime podcast, so we'll find out soon.

This person writes, my boyfriend has been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now, he's insisting we get to know each other, but I just want her gone. Now, hold up. Isn't that against school policy? That sounds totally inappropriate. Well, according to this person, this is her boyfriend's former professor and they're the same age. And it's even more likely that they're cheating.

He insists there's nothing between them. I mean, do you believe him? Well, he's certainly trying to get this person to believe him because he now wants them both to meet. So, do we find out if this person's boyfriend really cheated with his professor or not? To hear the explosive finale, listen to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. I'm Dr. Scott Barry Kaufman, host of the psychology podcast. Here's a clip from an upcoming conversation about exploring human potential. I was going to schools to try to teach kids these skills, and I get eye rolling from teachers

or I get students who would be like, it's easier to punch someone in the face. When you think about emotion regulation, like, you're not going to choose an adaptive strategy, which is more effortful to use unless you think there's a good outcome as a result of it, if it's going to be beneficial to you. Because it's easy to say, like, go you go blank yourself, right? It's easy. It's easy to just strengthen. extra beer. It's easy to ignore, to suppress, seeing a colleague who's bothering you and just

like walk the other way. Avoidance is easier. Ignoring is easier. Denial is easier. Drinking is easier. Yelling, screaming is easy. Complex problem solving, meditating, you know, takes effort. Listen to the psychology podcast on the IHeartRadio app, Apple Podcasts, or wherever you get your podcasts. All right, we're talking about solar panels and how they work, and they do work. They're pretty good. I have some. How well do your solar panels work?

You generate enough electricity for your house every day? Yeah. In fact, they generate so much energy. We get a check from the electric company. They're like, you gave us too much electricity. Here's some money back. And your energy goes back to the electric company and then back to your house, right? You don't directly use the electricity, create.

it on your roof, do you? Right, yeah. No, I don't have a battery. So it just goes back into the grid and then we get from the grid. But they keep track. And if we make more than we take, then they give us a small amount of money for that.

Awesome. Yeah. So we were talking about how it works and it involves silicon and P-type and N-type of materials that have holes and extra electrons. And so is the idea then that,

you know, the side that has too many electrons gives them to the side that doesn't have enough electrons. And that creates kind of like a, like a stand. off almost, like a barrier for any more electrons to flow. But once the light comes in, then that kind of kicks things up. Yeah.

And then these new electrons get pushed away from that barrier, as you said, and towards the edge. And then they get gathered up and the current forms with all these energetic electrons. And you can draw that off. And that's basically what electricity is. It's energetic electrons. It's electrons moving along. That's what current is. It's just the motion of charged particles.

Wow. It feels kind of like almost like, magic. I mean, like the sunlight is not actually creating energy. It's just kind of like triggering the flow of energy. Yeah, well, sunlight is energy, right? It's energy that was released from the fusion of hydrogen into helium in the center of the sun and that has been flying 93 million miles through space. And the cool thing is that that energy doesn't like evaporate or run out. You know, photons can fly through space basically forever without losing any energy. It doesn't take them any energy to fly the speed of light. And then that energy gets

deposited, you know, on your solar cell and gets lirped up into that electron. It's really pretty awesome. And the coolest thing about it, I think, is that it's quantum mechanics. You know, this is not something you can explain with classical physics. So it's something we only could have invented pretty recently. Well, we understand it now, but didn't we sort of invented before understanding how it works? Yeah, you're right. We understand it now, which allows us to, like, optimize it.

And we certainly never could have built like these complicated PN junctions without understanding quantum mechanics. But I suppose some clever engineer could have put it together without a deep physics understanding. You suppose. Like I guess if they were like a super special genius engineer. No, you're absolutely right. And there's lots of examples of times when we built something, we saw I do something cool and we didn't understand what was happening. And that led to lots of really awesome questions. You know, like that's how electrons were discovered. People didn't understand crooks tubes and these glowing rays they saw inside them. And so it led to lots of awesome stuff. Yes, absolutely. You can build stuff before you understand it.

It is pretty cool to think now that you mention it. It's amazing how these photons were made in the sun and they traveled millions of miles, really sort of uninterrupted. Like they don't lose any energy in the way. It's almost like a perfect transmission. And then they hit my solar panel and powers my devices. Yeah, exactly. So really, solar power is fusion power. You know, it's just like you are a blanket to absorb energy from a fusion device.

We talked about Eater a few weeks ago and how a big problem they have is how to absorb the energy that Eater creates. Like, haven't really tackled that problem yet. And you're basically doing that for the sun. You know, the sun is this huge fusion engine. Yeah. And you're putting up a little panel to grab a tiny little slice of it. Oh, man. I wonder how many more panels they would sell.

They called it that, you know, fusion panels. Who wants some. Probably fewer. Who wants a fusion generator on the roof. A hydrogen bomb on your roof where you're. Kids sleep. Who doesn't want their computer, their work powered by fusion energy? Me, I don't.

No, honestly, I do. That's super awesome. I think it's wonderful. And also, it works pretty well. You know, it's sort of shocking how efficient it is. What do you mean? What's the efficiency? Well, the record efficiency for like the most highly engineered solar panel so far is about

46%. That's the fraction of the energy of the photons coming in that you can effectively gather out as electricity. Wow. And that's pretty good. Yeah. That's like a one out of every two photons. You actually use it for something. Yeah. And it's not 100% efficient because not all the energy goes into one electron or that electron loses some of its energy along the way as it moves along through the silicon and gets to the thing that stirps it out or it goes into, you know, exciting the nucleus or stuff like that. And most devices that you would have on your roof are not that efficient. Mostly they're like 15 to 20% efficient, though they've climbed a lot in recent years.

It's incredible. the prices are dropping and the efficiencies are rising. And even 20% is really pretty efficient. Yeah. What happens to the other percent? Like where does all the other energy go? Gets reflected or absorb? It just goes into heating the material.

You know, there's lots of ways for silicon to absorb energy, not just one electron getting kicked up an energy level. The nucleus can absorb energy or the electron can absorb the energy and then lose it to something else. And so there's a lot of delicate engineering involved in getting those electrons to be the place for the energy lands and getting them to deliver it to the edge of the PN junction. You know, this stuff is really cool because it's actually very similar to what we do with the large Hedron Collider.

We use silicon devices to detect the passage of particles, photons, but also like muons or other particles, and you detect particles in exactly this same way. The particle passes through the detector, and it leaves a trail of electrons behind it, which we then slurp off and use that as evidence to say, hey, there was a particle. that passed through here. Wow. So we should maybe think about rebranding it that way, too. Like, don't call them solar panels, call them muon absorbers.

Particle detectors. Particle, yeah, who doesn't want a particle detector on the roof? And, you know, the same basic principle works also in every digital camera, right? That's how a digital camera turns a photon, which is the picture you're seeing into an electrical signal, which is what your computer needs to record it. The photovoltaic effect, it turns a photon into a little. electrons, which then get gathered up at the edge of your little pixels and recorded as evidence that a photon came through as light.

That's right. Yeah. That means everyone who has a camera on their phone has a solar panel in their pocket. That's right. That's right. Except that it draws power instead of generating it. Unfortunately, it generates images, but it doesn't generate power. Does that mean I have a giant camera on my roof taking pictures of the sun every day?

Absolutely. And, you know, we have done the calculations. Can you use solar panels? as particle detectors, could we use everybody's solar panels as like a huge telescope to understand cosmic rays? Unfortunately, you can't because you're swamped by the photons from the sun, which make a huge signal and everything else we're interested in, like little muons or positrons or protons is swamped by that huge blinding light from the sun.

But it does, you say my solar panels do detect these other particles? It is technically, like catching them and converting them to a signal? It totally is. If you covered your solar panels, if you made them light proof, which would be terrible for your electrical efficiency, but if you made them lightproof and covered them up so they were in a black box, then there would be great detectors for muons or other kinds of particles that could penetrate that seal and leave energy. Interesting. All right. I am ready to do scientific experiments on my roof. At the expense of actually generating any electricity.

Well, some sacrifices might have to be made. How important is science to you? All right. Well, that's sort of how they work. I guess maybe a question is they're pretty great, but why aren't there more of them out there? Why doesn't everyone jump into this solar energy bandwagon? Is it political or are there other limitations? There are some other limitations.

You're right. They're pretty great. But there are some downsides to solar panels. One is that the sun is not always above you in the sky, right? Sometimes there are clouds or it's nighttime. time. And so you're generating power whenever the sun is above your solar panels, but that's not always the case. And you need power sometimes at night or when it's cloudy. And so you need a complicated system there to buffer, to gather energy into like a battery and to save it for you for

when you need it. Right. But that's not really a negative. It just means that, you know, you need a like a buffer. You need like a something that stores it like a battery. Yeah, but it adds to the cost. You know, just like the transport issues. Say, for example, you have. a huge solar panel array out in the desert to gather energy really efficiently, then you need to send that energy hundreds or thousands of miles to where it needs to go, because you have a mismatch sometimes between where the energy is used and where the energy is created. I mean, if every device could just create solar power whenever it needed it, wherever it was, that would be awesome. But one of the main costs of solar power is fabricating the devices

themselves, of course, which is not trivial and not cheap, but also transporting and buffering, building these batteries. You know, battery technology is complicated and also quite toxic. Right. But I think that, you know, you need to do these things anyways for any kind of power, don't you? Like, you still need the infrastructure for burning coal or for nuclear powered energy, right? Well, you know, you can turn your coal power plant on any time of day or night, right? And so it can be a much steadier source of power. It doesn't have these fluctuations. You don't need the same kind of buffer for a coal power plant. A coal power plant, essentially the energy is already in a battery.

That battery is called coal, and it's available for whenever you need it. You just have to transform it into electricity. Now, of course, coal is terrible for lots of other reasons. I'm not selling coal. But one of the disadvantages of solar power is that it's not always created when you need it. Right, right. But fortunately, I'm mostly asleep at night. Well, actually, that's not true for me.

But I think for most of humanity, you're sort of asleep at night, so you don't actually use that much. energy at night, right? And it's cooler and so you don't need the AC. Really, like, I think most people's power consumption matches sort of daylight. Yeah, do you use less power when it's cloudy outside? Yeah, because, you know, you don't need to cool your house as much, right? No, you're absolutely right. It's not a killer for solar power for sure. It just means, you know, you have to build this infrastructure and you have to have batteries and you have to do this kind of stuff. But you're right, people use more energy when it's daytime and they need more AC when it's sunny outside. And so that's not

that big an issue. Well, obviously, it's not like free energy and it's not super simple to get solar energy, but it's still, I think overall, it's renewable, right? And we don't create carbon emissions and it's still more positive than most other sources of energy, right? Absolutely. And it's getting cheaper. You know, the more we work on it, the easier it is to fabricate these solar panels. They last longer. They're more efficient. They're cheaper. They're easier to produce. And it's sort of something that builds on itself. The larger the market is, the more companies get involved, the more competition there is, the more clever engineers get on board for making these things effective, the better batteries get. It seems like an excellent option for the future. It just takes

sort of an investment. It just takes us deciding to make this happen. Yeah. And it's like we're getting this energy from space for free. It feels great to use it. It does. And there's lots of really fun ideas for how you could tap into it. You know, you don't need to build a huge array of solar panels in the middle of your city. You can put them in the desert. We have lots of huge areas of the earth where nobody's living because it's just sand. And you could put vast solar arrays there. You could even have them like floating on things in the ocean, just gathering up solar energy. So if you built enough infrastructure there, you could really power a lot of our civilization's energy needs. Yeah, and create a lot of shade in the desert, which would be pretty good probably for a lot of the animals there.

All right. Well, that's sort of the big picture and the little picture. of solar power, and we're going to do something a little bit interesting next, which is compare them to photosynthesis. But first, let's take a quick break. December 29th, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed. There's been a bombing at the TWA terminal.

Apparently the explosion actually impelled metal glass. The injured were being loaded into ambulances, just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, and it was here to stay. Terrorism. Law and order, criminal justice system is back. In season two, we're turning our focus to a threat that hides in. plain sight that's harder to predict and even harder to stop listen to the new season of law and order criminal justice system on the iHeart radio app apple podcasts or wherever you get your

podcasts my boyfriend's professor is way too friendly and now i'm seriously suspicious oh wait a minute sam maybe her boyfriend's just looking for extra credit well dakota it's back to school week on the okay story time podcast so we'll find out soon this person writes my boyfriend has been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now, he's insisting we get to know each other, but I just want her gone. Now, hold up. Isn't that against school policy?

That sounds totally inappropriate. Well, according to this person, this is her boyfriend's former professor, and they're the same age. And it's even more likely that they're cheating. He insists there's nothing between them. I mean, do you believe him? Well, he's certainly trying to get this person to believe him because he now wants them both to meet. So, do we find out if this person's boyfriend really cheated with his professor or To hear the explosive finale, listen to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast.

I'm Dr. Scott Barry Kaufman, host of the Psychology Podcast. Here's a clip from an upcoming conversation about exploring human potential. I was going to schools to try to teach kids these skills, and I get eye rolling from teachers or I get students who would be like, it's easier to punch someone in the face. When you think about emotion regulation, like you're not going to choose an adaptive strategy. which is more effortful to use unless you think there's a good outcome as a result of it, if it's going to be beneficial to you. Because it's easy to say, like, go you, go blank yourself, right? It's easy.

It's easy to just drink the extra beer. It's easy to ignore, to suppress, seeing a colleague who's bothering you and just, like, walk the other way. Avoidance is easier. Ignoring is easier. Denial is easier. Drinking is easier. Yelling, screaming is easy. Complex problem solving, meditating, you know, takes effort.

Listen to the psychology podcast on the IHartRadio app, Apple Podcasts, or wherever you get your podcasts. All right, we're talking about solar power, and we talked about how solar panels work. And so, Daniel, you thought something interesting would be to sort of compare this man-made machine and device that we've made to capture solar energy to what nature has done. plants use solar power and so through something called photosynthesis. And so how do the two compare? Do they use a similar mechanism or is it totally different?

Yeah, I thought this was really fascinating because we've been working on this technology for decades, but nature has been doing this for literally billions of years. And it's got a really refined process for making things more efficient and more effective in finding solutions. And so naively, I

thought to myself, well, I'm sure that our efficiency is pretty good, but nature's efficient. must be even higher because it's been fine-tuned for so long. But you know, you start to read about photosynthesis and you discover that it's actually less efficient that a smaller fraction of the light that comes from the sun and hits a plant gets turned eventually into energy. And it's using a completely different process. Yeah, so they're not as good as solar panels, I guess, and absorbing energy.

I guess they don't have the advantage of like having silicon and all these dope materials and highly engineered materials. How do they work? How do plants absorb sunlight? Yeah, you're right. The plants don't necessarily have access to some of the rarer elements that we use to dope our silicon to make these diodes work. What they do is they have the light come in and it interacts with carbon dioxide and water inside the leaf. And essentially what it does is it builds a sugar.

They turn light not into electricity because plants aren't interested in electricity. They don't run air conditioning or sit on their phones all day, right? It basically turns light into plant food, which is these complex. complex carbohydrates. These carbons and hydrogens and oxygens all built together into things that are fiber or what we would call sugar. They do it through chemistry. Like, you know, they have the ingredients there sort of on the leaf and then the sunlight triggers a reaction or triggers like molecules kind of coming together. Yeah, exactly. Chemistry is all about energy flows, right? So you can store energy in chemical bonds. You can build something that has energy inside of it.

But then you need to put the energy in, right? You can't just have the ingredients. there, sort of like baking a cake. You can't just mix the ingredients. You need to supply the heat. And so in order to make these sugars, these sugars which store energy, you need to bring the raw ingredients together, which is carbon dioxide and water. And then you need to apply the energy. And that's where the photon comes in. And so the photon comes in and chemistry happens. And then you get out, you get sugar, and you get oxygen as a byproduct, which is wonderful for all of us oxygen breathers. Yeah. And all of those salad eaters, too. Yeah. And for the plants, Specifically, it's basically turned the energy into plant food, right?

So we want to generate electricity, and plants, what they want to do is they want to generate these sugars. And really the answer to the question of, you know, why is photosynthesis less efficient than solar power is really that they're doing different things. Plants have optimized turning photons into plant food, into this fuel, which they can store and then very easily use later on, whereas we've optimized for creating these electrons, which we can either use immediately or try to funnel into batteries. It's almost like they've invented the battery and the panel at the same time. Yeah, it's really pretty impressive technology, right?

This plant fuel is a great way to store energy. And so it's a really nice thing for them because they can use it whenever they need it. They don't have to worry about creating the battery. Right. And in fact, it takes carbon dioxide from the air. Yeah, exactly. And produces oxygen. Yeah.

And delicious vegetables. And delicious vegetables. Exactly. And, you know, it also captures a different fraction of the solar energy. Like photovoltaic cells, the ones that we build, they can capture energy that's out of the visible spectrum. You don't have to be able to see the photon for your solar panel to be able to slurp it up and turn it into electricity. You can also capture the energy of photons that have a wavelength that's too long. They're in the infrared or photons that have a wavelength that's too short.

They're in the ultraviolet. Your photovoltaic cells made from silicon can slurp that up. Plants are mostly sensitive to the visible spectrum. So they get sort of a smaller slice of all the light that comes in. But I think solar panels also use a photo will take effect a little bit similar. I mean, they're optimized for certain wavelengths, right? Yeah, I mean, we certainly are optimized

for the wavelengths that come from the sun, right? They've chosen a material that can absorb it. And you're right, this is quantum mechanical, and so you can't absorb just any photon that comes in. It has to be a good match for the material because every material has certain wavelengths of light. It can absorb, and other wavelengths it's transparent to. And so one of the reasons silicon is chosen, it's not just because it's a semiconductor, but because it can absorb light in the wavelength that's hitting the earth.

So plants aren't as efficient, but they're pretty good at other things, right? Like a plant, you don't need to hose it down when it gets too dusty. That's right. Plants are a much nicer option compared to solar panels in some way because, for example, they build themselves, right? If you could just sprinkle like solar panel seeds on your roof and they like sprouted up and created working solar panels, that would be pretty. awesome. That would be pretty awesome, yeah. That sounds like crazy science fiction, right? But that's basically what plants can do. They self-assemble from a seed. You ever look at it like a huge tree and wonder like, where did all the stuff from that tree come from? Well, that tree has basically

built itself out of the air. It has pulled the carbon out of the air to construct itself. That's pretty awesome engineering, you know. Without any supervision, no project management, no Excel spreadsheets, you know, no invoices, no meetings. It just did it. That's the most attractive part to you right now. Like no Zoom meetings were required to make this tree. That's the apex of cleverness and achievement there. Yeah, exactly. And on top of that, they fix themselves. You know, if you shadow your solar panel, you can't come back the next day and see it started to heal. But if a leaf falls off your plant, it'll just grow a new one, you know? It'll just fix itself. So they're really pretty awesome. And they can be grown basically

anywhere using the materials readily at hand. You don't have to mine this delicate material out of the crust of the earth. So I've got a lot of good things to say about plants. And even though technically their energy transmission rate is less efficient than photovoltaic panels, they're pretty awesome. Yeah. Now for sure, plants are amazing, but they can't power my computer or our podcast recorder here. No, not directly. But, you know, there are folks who are working on electric leaves. What? What do you mean? These are mechanical devices or electrical devices that are trying to replicate photosynthesis instead of replicating, you know, photovoltaic process.

So you have the stuff inside this device, basically water and carbon dioxide, and you want to replicate photosynthesis to produce sugar and oxygen. So an electric leaf is different from a photovoltaic cell. Right. Oh, so it will produce sugar as an output? Like, you can have a sugar factory on your roof? Yeah. You feed in carbon dioxide and water.

and sunlight. And yes, it will give you sugar and oxygen. So there are a whole group of folks working on these artificial leaves instead of working on photovoltaic cells. Interesting. So you can put it in your cold coffee because you don't have any electricity to heat it up. Yeah. But, you know, artificial leaves still do not grow themselves or fix themselves and they're a lot more expensive than a seed. So it's a tough engineering challenge to beat nature at its own game. Yeah. Well, What if, Daniel, you build like a factory with AI that makes its own solar panels to power itself? That would be sort of like making a self-growing solar panel. Yeah.

If you design robots that could build solar panels and manage them and fix them, then yeah, that would be pretty awesome. That's kind of what a plant is, isn't it? It's like a little robot. I mean, he's just following the instructions in the DNA. It's just kind of like a little robot that's following its own instructions. Yeah, it's a little organic, evolved robot. but then I guess so are we, right? Until your AI goes crazy and then just covers the whole planet with solar panels, right?

Which would give us a lot of energy. There you go. But there'd be nobody to use it, right? Like, sorry Jorge, I have to knock down your house to build solar panels. Those are my instructions. Well, I can live under a panel. Just saying, you know. I'm imagining this science fiction novel, a future dystopia where we all live in the darkness,

but we have a lot of energy from the solar panels. Yeah. Well, you can build windows. I mean, come on. They can spare a few percentage of the square footage there. And then the robot comes along and filled it in with a solar panel. All right, a little off topic here. So solar panels, yes.

They take sunlight and convert it to electricity and they do it through these silicon circuits. But, you know, they take some infrastructure. But overall, the infrastructure is sort of worth it, right? Because it's clean energy. Absolutely. And the infrastructure can get cleaner and simpler and cheaper. that's an engineering, that's a technology barrier. It's not something fundamental to the process.

Like with nuclear fission, which will always produce some toxic waste, or with fossil fuels, which will always release some sort of carbon. This, at its core, is a really clean, cheap source of energy that's already produced and being beamed to us from the facility 90 million miles away. Yeah, and it's guilt-free. That's right. It's negative guilt. So you can turn on your solar panel and have an extra box of cookies. Yeah.

There you go. and the electric company will send you a box of cookies every month. Or money, whichever you prefer. All right, well, we hope you enjoyed that. Thanks for joining us. See you next time. Thanks for listening,

and remember that Daniel and Jorge Explain the Universe is a production of IHeartRadio. For more podcasts from IHeartRadio, visit the IHeartRadio app, Apple Podcasts, or wherever you. you listen to your favorite shows. December 29th, 1975, LaGuardia Airport.

The holiday rush, parents hauling luggage, kids gripping their new Christmas toys, then everything changed. There's been a bombing at the TWA terminal, just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, terrorism. Listen to the new season of Law and Order Criminal Justice System on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Why are TSA rules so confusing? You got a hood of you. I'll take it all!

I'm Manny. I'm Noah. This is Devin. And we're best friends in Germany. with a new podcast called No Such Thing, where we get to the bottom of questions like that. Why are you screaming at me? I can't expect what to do. Now, if the rule was the same, go off on me. I deserve it. You know, lock him up. Listen to No Such Thing on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. No Such Thing. I'm Dr. Joy Harden Bradford, host of the Therapy for Black Girls podcast. I know how overwhelming it can feel if flying makes you anxious.

In session 418 of the Therapy for Black Girls podcast, Dr. Angela Neal-Barnett and I discuss flight anxiety. What is not a norm is to allow it to prevent you from doing the things that you want to do, the things that you were meant to do. Listen to Therapy for Black Girls on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. This is an IHeart podcast.