Speaker 1: Hey, Daniel, do you have solar power panels on your roof? Embarrassingly,
Speaker 1: I don't. You don't? Why not? I just haven't gotten
Speaker 1: around to it yet. It's the honest roof, so there's
Speaker 1: kind of an energy barrier there. I know, I know
Speaker 1: I should do it, but you know, prices keep falling,
Speaker 1: and I guess that's what I say to myself to
Speaker 1: justify my laziness. Oh man, you just cheap. We would
Speaker 1: you get solar panels if they caused pennies or if
Speaker 1: they could repair themselves and automatically reproduce. Well, that's an
Speaker 1: offer so powerful I could hardly refuse. I am more
Speaker 1: handmade cartoonists and the creator of PhD comics. I'm Daniel.
Speaker 1: I'm a particle physicist, and like you, I haven't to
Speaker 1: do list that's too long. Welcome to our podcast, Daniel
Speaker 1: and Jorge Explain the Universe, a production of I Heart Radio,
Speaker 1: in which we talk about all the things that are
Speaker 1: amazing about the universe, all the places our curiosity has
Speaker 1: taken us, all the questions we have asked and all
Speaker 1: the answers we have found so far. But we love
Speaker 1: to talk about the questions that we have in the
Speaker 1: questions that you have, the things that you are curious
Speaker 1: about the universe. Yeah, we like to take you to
Speaker 1: the far reaches of the cosmos, to other galaxies and
Speaker 1: inside of black holes, but we also like to take
Speaker 1: you to your neighborhood, to the world around you and
Speaker 1: talk about the things and the questions that we have
Speaker 1: in our everyday lives, because physics is everywhere. It's not
Speaker 1: just out there in the center of black holes and
Speaker 1: the craziness of neutron stars. It is right here making
Speaker 1: our lives better. Or maybe, Jorge, you'd say this is engineering. Yes, yes,
Speaker 1: I would say that. Or maybe finally, this is physics
Speaker 1: and engineering working harmoniously together. Yeah, because as humans, we've
Speaker 1: made a lot of knowledgy and a lot of progress
Speaker 1: in science and knowing how things work to the point
Speaker 1: where we can create things that take advantage of nature
Speaker 1: to make our lives easier. That's right, Because the universe
Speaker 1: is out there pumping out energy into space, these crazy
Speaker 1: nuclear bombs going off at the center of every solar system,
Speaker 1: and so of course it's tempting to potentially take advantage
Speaker 1: of that. Yeah, So today we will be tackling a
Speaker 1: question that a lot of readers have sent in, right, Daniel,
Speaker 1: that's right. A lot of folks see these things on
Speaker 1: the roofs in their neighborhoods and they wonder how does
Speaker 1: that work? What's going on in there? So to be
Speaker 1: on the program, we'll be asking the question how do
Speaker 1: solar panels work. It's a really fun question because you
Speaker 1: see these on the roofs in your neighborhood, and you
Speaker 1: know they generate electricity, but how does it actually happen.
Speaker 1: I mean, we know the sun pumps out energy, but
Speaker 1: how does that turn into zippy electrons in your iPhone battery.
Speaker 1: I have solar panels in my roof. It's amazing. I
Speaker 1: haven't paid any electricity bill in like years. In fact,
Speaker 1: the electric company writes me checks for how much energy produce.
Speaker 1: So you are the electric company now I am my
Speaker 1: own company. Yes, yeah, I know. It's pretty awesome. I
Speaker 1: mean you invest in it and then it pays off
Speaker 1: over the years. Yeah. And it makes a lot of
Speaker 1: sense because in the end, the sun is the direct
Speaker 1: source of almost all the energy we use here on Earth.
Speaker 1: Even fossil fuels originally just came from energy from the sun,
Speaker 1: and so it's tempting to say, hey, let's just go
Speaker 1: direct to the source. Why build a fusion reactor here
Speaker 1: on Earth when we have a huge one in the
Speaker 1: center of our solar system, Let's just suck up some
Speaker 1: of that energy. Yeah, because it sort of feels like
Speaker 1: a waste almost, you know, Like I think about all
Speaker 1: of the energy that used to hit my roof before
Speaker 1: I had a solar panels, and all the energy just
Speaker 1: kind of goes to waste. It just hits the roof
Speaker 1: and bounces and heats it up a little bit, but
Speaker 1: then it cools down again at night. So I feel
Speaker 1: so much more like I'm taking advantage of nature in
Speaker 1: using up the energy that's there. Right, So you're not
Speaker 1: just doing it for the econom benefits, You're doing it
Speaker 1: because it makes you feel like a better person. Honestly. Yeah,
Speaker 1: I feel like I invested in a more guilt free lifestyle.
Speaker 1: Like in the summer, we can just turn on the
Speaker 1: A C guilt free because it's all coming from the
Speaker 1: sun and have a second box of cookies. Right. Yeah,
Speaker 1: And you're right, there is a huge amount of energy there.
Speaker 1: The amount of sunlight that falls on the Earth is
Speaker 1: like a hundred and seventy three thousand terra wats. It's incredible.
Speaker 1: It's a lot of wats. That's a lot of terra wats.
Speaker 1: And it's actually a thousand times more than the entire
Speaker 1: energy budget of our civilization. Wow, meaning that a thousand
Speaker 1: times more energy falls on Earth from the Sun than
Speaker 1: we use. Yeah, so if you could capture the solar energy,
Speaker 1: you could easily power the entire civilization with just a
Speaker 1: fraction of the energy that comes from the Sun. So
Speaker 1: it's a huge resource. It's incredibly powerful. It's right there.
Speaker 1: It seems awfully tempting to try to capture it. What
Speaker 1: would be the number, Daniel is, So if it's a
Speaker 1: thousand times more, does that mean that if we over
Speaker 1: the earth the Earth in solar panels, we would be
Speaker 1: set if it was efficient. Yeah. I've seen lots of
Speaker 1: different calculations actually about how many solar panels you would need,
Speaker 1: But you don't need to cover a significant fraction of
Speaker 1: the Earth and solar panels to get enough energy to
Speaker 1: power the Earth. We'll talk about a little bit more later.
Speaker 1: One of the biggest challenges actually is getting that power
Speaker 1: to the right place and storing it and having it
Speaker 1: at the right time. But it's a big percentage these days,
Speaker 1: or a significant percentage of the power that we consume
Speaker 1: these days, right, I mean, it's not like zero. It's
Speaker 1: not like zero. Here in the US we get about
Speaker 1: three percent of the energy that we use from solar panels,
Speaker 1: but in other countries it's higher. China's four percent, Germany
Speaker 1: is eight percent, Australia goes to nine percent, and Honduras
Speaker 1: tops it out at well A sairly as understandable. I mean,
Speaker 1: everything is bigger in Australia and Sunnier, even their solar panels.
Speaker 1: Spiders and solar panels. Yeah, it aren't like the kangaroos
Speaker 1: hanging out on top of the solar panels blocking it.
Speaker 1: I wonder if that gets factored in. And I guess
Speaker 1: the great thing about it is that it's carbon free,
Speaker 1: Like it doesn't give off any emissions? Does it have
Speaker 1: operating the solar panels certainly doesn't. There's a question of
Speaker 1: constructing solar panels and infrastructure to store that and create batteries,
Speaker 1: and there's definitely some toxic materials that are used and
Speaker 1: created there. But operating solar panels no, they have no
Speaker 1: moving parts. They just sit there and turn photons into electricity.
Speaker 1: So they're pretty awesome. Yeah, so a big question that
Speaker 1: our readers have is how do they work, Like, how
Speaker 1: do they convert solar energy sunlight into electricity you can
Speaker 1: use for your devices and video games and televisions and Netflix,
Speaker 1: and so we were wondering how many people out there
Speaker 1: know how solar panels work? That's right, and so I
Speaker 1: asked folks who volunteered to speculate without googling about how
Speaker 1: solar panels work. And if you'd like to speculate without
Speaker 1: reference materials on difficult questions in physics, please write to
Speaker 1: me at questions at Daniel and Jorge dot com. Yeah,
Speaker 1: so think about it for a second. Do you know
Speaker 1: how solar panels work? Here's what people had to say.
Speaker 1: You know, I've never thought about it, um and I
Speaker 1: have no idea. The panels capture the photons from the
Speaker 1: sun and stored. You know, it's a circle of life,
Speaker 1: you know. I don't really know the specifics. I know
Speaker 1: that they're also called like photo voltaic panels. I don't
Speaker 1: know if I'm saying that right. I've only ever seen
Speaker 1: the word written out, but which makes me think it's
Speaker 1: got to have something to do with the photon specifically
Speaker 1: interacting with the panel, you know, because I just saw
Speaker 1: a small presentation last week. So sunlight activates the panels
Speaker 1: the silly compounds, uh, and the cells produce electrical current,
Speaker 1: which is converted in um electrical energy or no electrical
Speaker 1: energy is converted in electrical power. My understanding is that
Speaker 1: these solar energy hits these panels, and based on that energy,
Speaker 1: there's some photo voltaic cells which translate that into electrical energy.
Speaker 1: I'm not really sure how. Maybe because of the expanding heat,
Speaker 1: it creates a differential and different metals. I know they
Speaker 1: have photo voltaic cells in them, um, but I couldn't
Speaker 1: explain the science behind it. All Right, A lot of
Speaker 1: people seem to have some idea. A lot of people
Speaker 1: said the words photo voltaic. That's pretty impressive. Yeah, that's
Speaker 1: pretty awesome, and it goes to the core of the
Speaker 1: physics that's happening inside solar panels. And I think often
Speaker 1: they're called photo voltaic cells, and so that gives people
Speaker 1: a clue about what's going on inside photo I guess
Speaker 1: light will take just kind of a meaning electricity. Yeah,
Speaker 1: and it is in the end of interaction between photons
Speaker 1: and electrons, So it makes a lot of sense. All right,
Speaker 1: Well let's break it down for folks. How do solar
Speaker 1: panels work, Daniel? I mean, I assume they at sunlight
Speaker 1: and somehow that gets transformed into electricity. So what's going on? Yeah,
Speaker 1: So there's sort of two steps there. One is how
Speaker 1: does the energy get from the photon into the material?
Speaker 1: And the second is how can you construct a material
Speaker 1: that it can effectively grab that energy and siphon it
Speaker 1: off into electricity? And so the first step is called
Speaker 1: the photovoltaic effect, or a photon hits a piece of
Speaker 1: material and it basically passes that energy to an electron.
Speaker 1: What does that mean, Like the electron absorbs the photon,
Speaker 1: or like the photon hits the electron. How can I
Speaker 1: visual life? Yeah, the photon is absorbed by the electron.
Speaker 1: Remember that electrons interact electromagnetically, and that just means that
Speaker 1: they trade photon. So every kind of electromagnetic interaction, every
Speaker 1: push and pull by electric fields is mediated by photons.
Speaker 1: So photons are the way that electrons talk to each
Speaker 1: other and other charged particles. And photons are not eternal, right,
Speaker 1: they can get absorbed by an electron, Their energy goes
Speaker 1: right into the electron and then the electron has that energy.
Speaker 1: So the way I visualize it as like a photon
Speaker 1: coming in meets an electron and then only the electron continues.
Speaker 1: So now the electron absorbs the photon and now I
Speaker 1: guess it's charged up or something. Yeah, it's more exciting, exactly,
Speaker 1: it's charged up. And there's two different effects here that
Speaker 1: are very closely related. One is the photo voltaic effect,
Speaker 1: which is what we're talking about, and the other is
Speaker 1: something more famous that people might have heard about called
Speaker 1: the photoelectric effect. They sound very similar and they are
Speaker 1: very similar. Photoelectric effect it's when the photon has enough
Speaker 1: energy that the electron gets kicked out of the materials.
Speaker 1: So people saw this about a hundred years ago. If
Speaker 1: you shine light at a material, you will get electrons
Speaker 1: boiling off the surface, and that's because they have so
Speaker 1: much energy they can leave the trap of the material,
Speaker 1: meaning like a you know, an electron is orbiting the
Speaker 1: nucleus of an atom because the nucleus is positive, but
Speaker 1: now it has so much energy it just pops up. Yeah,
Speaker 1: it just pops out. And this electric effect is actually
Speaker 1: what Einstein won his Nobel Prize for explaining and was
Speaker 1: one of the key experiments that led us to understand
Speaker 1: that light is not just electromagnetic waves, what actually comes
Speaker 1: in little particles, because we saw these weird relationships between
Speaker 1: the intensity of the light and the wavelength and how
Speaker 1: many electrons were boiled off. But we have a whole
Speaker 1: other podcast episode about that about how we know that
Speaker 1: light is quantized made out of these little photons. But
Speaker 1: that's very similar to the photovoltaic effect. But the voltaic
Speaker 1: effect is when the photon comes in and the electron
Speaker 1: gets enough energy, but not enough to actually leave the material.
Speaker 1: It gets excited, but it's still hanging out sort of
Speaker 1: in the same blob of stuff I see. So it's
Speaker 1: just a matter of whether or not it gets enough
Speaker 1: energy to pop out, basically. Yeah, And there are some
Speaker 1: materials where electrons don't have to be isolated to one
Speaker 1: specific atom, like the picture you described as correct, you
Speaker 1: have an electron it's orbiting a nucleus, for example, although
Speaker 1: we don't really like to think of them as actually orbiting.
Speaker 1: It's hanging around quantum mechanically near it's nuclear is. But
Speaker 1: in lots of crystals, you have electrons that can flow
Speaker 1: between atoms, and so, for example, in semiconductors, you have
Speaker 1: electrons that are trapped that are around individual atoms, and
Speaker 1: then if they get enough energy, they can jump up
Speaker 1: over a little gap into a band where they can
Speaker 1: move around more freely and jump from atom to atom. Yeah,
Speaker 1: they sort of float around, right, They're not bound to
Speaker 1: one atom. They can you know, hang out. Yeah, they're
Speaker 1: like social butterflies. They just float around. They have enough energy,
Speaker 1: they're sort of like flying high above all of these
Speaker 1: little gaps. And so that's what happens in the photovoltaic effect,
Speaker 1: that a phoeton comes in and knocks an electron off
Speaker 1: from being stuck around one of the atoms, and so
Speaker 1: they can float around free. Wait, that's the photo electric
Speaker 1: or photovoltaic. Poto voltaic is when it knocks it off
Speaker 1: so we can float around inside the material. Photo electric
Speaker 1: is when it gets so much energy that it flies
Speaker 1: free the material and out into space. It's like abandons
Speaker 1: its original family. Oh, I see, I see you Like
Speaker 1: one is like pop out out of the material, like
Speaker 1: out out of like a way and bolt take it
Speaker 1: leaves the atom. But it hangs out in the lattice,
Speaker 1: in the structure of the material. Yeah, it's just jumping
Speaker 1: around from atom to atom, floating free inside the material.
Speaker 1: The photo electric effect, it's like totally liberated and may
Speaker 1: never come back to home. All right. So that's the
Speaker 1: two effects, and the one in solar panels is the
Speaker 1: photovoltaic effect exactly. And so the key thing for solar
Speaker 1: panels is to take advantage of the photovol take effect.
Speaker 1: Because now you have this electron, it's got more energy.
Speaker 1: If you could grab that energy somehow, if you could
Speaker 1: funnel it into an electric current, then you could turn
Speaker 1: effectively that photons energy into electricity. And so that's why
Speaker 1: you need a special kind of material. Now, any kind
Speaker 1: of material can have the photovol take effect. Your hand
Speaker 1: or a rock or whatever. When it absorbs a photon,
Speaker 1: the electrons that absorb it don't fly off the material.
Speaker 1: Right then you're having the photovol take effect. You're grabbing
Speaker 1: that energy into the object. But you need a special
Speaker 1: kind of material to effectively gather that energy and funnel
Speaker 1: it off into electricity. And that's where the silicon diode
Speaker 1: comes in. And we had an a whole episode about diodes, right,
Speaker 1: and transistors. Yeah, we did because we talked about how
Speaker 1: L E d s work, and diodes are like a
Speaker 1: really key foundational element of modern computing because you can
Speaker 1: use them to make L D s and transistors and
Speaker 1: all sorts of stuff. And it comes from semiconductors. And
Speaker 1: that's why silicon is so important to the computing industry
Speaker 1: because it's the most important semiconductor for building these kinds
Speaker 1: of things, right, And it's important because it's kind of
Speaker 1: a special material, right, Like it has just the right
Speaker 1: number of loose electrons and it's pretty stable. Yeah, because
Speaker 1: the electrons have these two different regimes they can be in.
Speaker 1: A conductor is where the electrons just flow freely everywhere
Speaker 1: from atom atom and insulator is one with the electrons
Speaker 1: are all stuck around their individual atoms. And a semiconductor
Speaker 1: is one that has both and has the electrons around
Speaker 1: the atoms and electrons at a higher energy that can
Speaker 1: hop freely from atom to atom. So that's what a
Speaker 1: semiconductor is, and silicon is a great example of it.
Speaker 1: And what happened and silicon is exactly that the electrons
Speaker 1: jump over this band and then they can float around free. Yeah,
Speaker 1: and so that's how you make a solar panel. As
Speaker 1: you use silicon to make a solar panel. But and
Speaker 1: then do you have to like create these different areas
Speaker 1: where one one area is like a P type and
Speaker 1: the other ones in N type. Yeah, you can't just
Speaker 1: use normal silicon. You need to create something that's going
Speaker 1: to funnel off the electrons. So the way that works
Speaker 1: is that you have two different kinds of silicon. It's
Speaker 1: not pure silicon. You've added stuff to it slightly to
Speaker 1: change the behavior. And so you have one kind you
Speaker 1: called N type, which has like extra electrons there are
Speaker 1: a bunch of electrons floating around that sort of don't
Speaker 1: have a chair to sit in if you played musical chairs.
Speaker 1: And another kind where you've added other kinds of materials
Speaker 1: like gallium or arsenide or whatever. So they're called P type.
Speaker 1: They don't have enough electrons. They're like empty spots for
Speaker 1: electrons to sit in. And semiconductor physicists they talk about
Speaker 1: these things as holes, and they treat them as if
Speaker 1: they're sort of like positively charged electrons. They think of
Speaker 1: them sort of like as particles. I remember we talked
Speaker 1: about the quasi particles like things that are not particles
Speaker 1: but sort of act like particles. This is a good
Speaker 1: example of one. It's a hole. It's like a missing
Speaker 1: spot for a particle, but it moves around sort of
Speaker 1: as if it was a positively charged particle. Right. It's
Speaker 1: like if you had five people for six chairs and
Speaker 1: they move around and change seats. It's like you keep
Speaker 1: track of worth of the empty seat, not the people. Yeah,
Speaker 1: and the empty seat moves like a particle, right, because
Speaker 1: if one person slides from one seat to the other,
Speaker 1: then the empty spot slides the other direction. Sort of
Speaker 1: cool to have that idea in your mind of an
Speaker 1: emptiness being a thing. Anyway, So you have these two
Speaker 1: kinds of the lookon the P type that has extra
Speaker 1: holes and the end type that has extra electrons, And
Speaker 1: because they match up together, there's the sort of you know,
Speaker 1: too much electrons on one side and too many holes
Speaker 1: in the other. Some of the electrons flow across the
Speaker 1: junction between them and fill up some of the holes
Speaker 1: on the other side, and that makes an electric field
Speaker 1: across them. That's the key thing. The electrons have flowed
Speaker 1: in one to action, and now they make an electric
Speaker 1: field going the other way right. I think what happens
Speaker 1: is that like the material that has too many electrons
Speaker 1: loses some of them because they all go to the
Speaker 1: side that has the holes. And now you have like
Speaker 1: this build up of too much too many electrons in
Speaker 1: in one place, and so that creates like a like
Speaker 1: a barrier, like a something that repels other electrons. Yeah, exactly.
Speaker 1: It's sort of like you know, diffusion of temperature. If
Speaker 1: a hot thing next to a cold thing, then the
Speaker 1: heat's going to flow over the cold side. And so
Speaker 1: you put this N type stuff with too many electrons
Speaker 1: next to the P type stuff without enough electrons, some
Speaker 1: of them flow over, and you're right, it creates this barrier.
Speaker 1: So now you have this P N junction, you have
Speaker 1: the silk, and it's all primed to get your photon.
Speaker 1: Because what happens when a photon hits this special diode,
Speaker 1: this combination of P type and N type silicon, is
Speaker 1: that when the electron gets kicked free, it doesn't just
Speaker 1: wander around loosely. Is now an electric field created by
Speaker 1: the P N junction that pushes the electron all away
Speaker 1: in one direction, and then you just have to have
Speaker 1: something at the edge there to gather these electrons, these
Speaker 1: electrons that have the solar energy absorbed, so they can
Speaker 1: move along and create electric current. All right, well, I
Speaker 1: have some questions about that, and let's get into some
Speaker 1: of the details in and also maybe let's talk about
Speaker 1: some of the larger issues about solar panels. But first,
Speaker 1: let's take a quick break. Right. We're talking about solar
Speaker 1: panels and how they work, and they do work, they're
Speaker 1: pretty good. I have some how Well, do your solar
Speaker 1: panels work? You generate enough electricity for your house every day? Yeah?
Speaker 1: In fact, they generate so much energy we get a
Speaker 1: check from the electric company. They're like, you gave up
Speaker 1: too much electricity. Here's some money back, and your energy
Speaker 1: goes back to the electric company and then back to
Speaker 1: your house. Right. You don't directly use the electricity created
Speaker 1: on your roof, do you, right? Yeah? No, I don't
Speaker 1: have a battery, So it just goes back into the
Speaker 1: grid and then we get from the grid. But they
Speaker 1: keep track and if we make more than we take,
Speaker 1: then they give us a small amount of money for them. Awesome. Yeah,
Speaker 1: So we were talking about how it works, and it
Speaker 1: involves silicon and p type and type of materials that
Speaker 1: have holes and extra electrons, and so is the idea
Speaker 1: then that you know, the side that has too many
Speaker 1: electrons gives them to the side that doesn't have enough electrons,
Speaker 1: and that creates kind of like a like a standoff
Speaker 1: almost like a barrier for any more electrons to flow.
Speaker 1: But once the light comes in, then that kind of
Speaker 1: kicks things up. Yeah, and then these new electrons get
Speaker 1: pushed away from that barrier as you said, and towards
Speaker 1: the edge, and then they get gathered up and the
Speaker 1: current forms with all these energetic electrons and you can
Speaker 1: draw that off. And that's basically what electricity is. It's
Speaker 1: energetic electrons. It's electrons moving along. That's what current is.
Speaker 1: It's just the motion of charged particles. It feels kind
Speaker 1: of like almost like magic. I mean, like the sunlight
Speaker 1: is actually creating energy, is just kind of like triggering
Speaker 1: the flow of energy. Yeah, well, sunlight is energy, right,
Speaker 1: It's energy that was released from the fusion of hydrogen
Speaker 1: into helium in the center of the sun and that
Speaker 1: has been flying nine million miles through space. And the
Speaker 1: cool thing is that that energy doesn't like evaporate or
Speaker 1: run out. You know, photons can fly through space basically
Speaker 1: forever without losing any energy, doesn't take them any energy
Speaker 1: to fly the speed of light, and then that energy
Speaker 1: gets deposited, you know, on your solar cell and gets
Speaker 1: slurped up into that electron. It's really pretty awesome, and
Speaker 1: the coolest thing about it, I think is that it's
Speaker 1: quantum mechanics. You know, this is not something you can
Speaker 1: explain with classical physics. So it's something we only could
Speaker 1: have invented pretty recently. Well, we we understand it now,
Speaker 1: but didn't we sort of invented before understanding how it works? Yeah,
Speaker 1: you're right, we understand it now, which allows us to
Speaker 1: like optimize it. And we certainly never could have built
Speaker 1: like these complicated p N junctions without understanding quantum mechanics.
Speaker 1: But I suppose some clever engineer could have put it
Speaker 1: together without a deep physics understanding. Suppose, like I guess,
Speaker 1: if they were like a super special genius engineer. You're
Speaker 1: you're absolutely right. And there's lots of examples of times
Speaker 1: when we build something we saw do something cool and
Speaker 1: we didn't understand what was happening, and that led to
Speaker 1: lots of really awesome questions, you know, like that's how
Speaker 1: electrons were discovered. People didn't understand crooks tubes and these
Speaker 1: glowing rays they saw inside them, and so it led
Speaker 1: to lots of awesome stuff. So yes, absolutely, you can
Speaker 1: build stuff before you understand it. It It is pretty cool
Speaker 1: to the thing now that you mentioned it. It's amazing
Speaker 1: how like these photons were made in the Sun and
Speaker 1: they traveled millions of miles really sort of uninterrupted, like
Speaker 1: they don't lose any energy in the way. It's like
Speaker 1: almost like a perfect transmission. And then they hit my
Speaker 1: solar panel and powers my devices. Yeah, exactly. So really,
Speaker 1: solar power is fusion power. You know. It's just like
Speaker 1: you are a blanket to absorb energy from a fusion device.
Speaker 1: We talked about either a few weeks ago and how
Speaker 1: a big problem they have is how to absorb the
Speaker 1: energy that either creates, like haven't really tackled that problem yet,
Speaker 1: And you're basically doing that for the Sun. You know,
Speaker 1: the Sun is this huge fusion engine and you're putting
Speaker 1: up a little panel to grab a tiny little slice
Speaker 1: of all. Man. I wonder how much any more panels
Speaker 1: they would sell. They called it dead. You know, fusion
Speaker 1: panels probably fewer fusian generator on the roof, a hydrogen
Speaker 1: bomb on your roof where your kids sleep. Who doesn't
Speaker 1: want their computer, their work powered by fusion energy? Me?
Speaker 1: I don't. No, No, honestly I do. That's super awesome.
Speaker 1: I think it's wonderful. And also it works pretty well.
Speaker 1: You know, it's sort of shocking how efficient it is.
Speaker 1: But I mean, what's the efficiency. Well, the record efficiency
Speaker 1: for like the most highly engineered solar panels so far
Speaker 1: is about forty that's the fraction of the energy of
Speaker 1: the photons coming in that you can effectively gather out
Speaker 1: as electricity. And that's pretty good. That's like a one
Speaker 1: out of every two holdons you actually use it for something. Yeah,
Speaker 1: And it's not a hundred percent efficient because not all
Speaker 1: the energy goes into one electron, or that electron loses
Speaker 1: some of its energy along the way as it moves
Speaker 1: along through the silicon and gets to the thing that
Speaker 1: stirps it out, or it goes into you know, exciting
Speaker 1: the nucleus or stuff like that. And most devices that
Speaker 1: you would have on your roof are not that efficient.
Speaker 1: Mostly they're like fifteen to twenty percent efficient, though they've
Speaker 1: climbed a lot in recent years. It's incredible the prices
Speaker 1: are dropping and the efficiencies are rising, and even is
Speaker 1: really pretty efficient. Yeah, what happens to the other percent?
Speaker 1: Like where does all the other energy go gets reflected
Speaker 1: or absorbed? It just goes into heating the material. You know,
Speaker 1: there's lots of ways for silicon to absorb energy, not
Speaker 1: just one electron getting kicked up an energy level. The
Speaker 1: nucleus can absorb energy, or the electron can absorb the
Speaker 1: energy and then lose it to something else, and so
Speaker 1: there's a lot of delicate engineering involved in getting those
Speaker 1: electrons to be the place where the energy lands and
Speaker 1: getting them to deliver it to the edge of the
Speaker 1: p N junction. You know, this stuff is really cool
Speaker 1: because it's actually very similar to what we do with
Speaker 1: the large Hadron collider. We use silicon devices to detect
Speaker 1: the passage of particles photons but also like muans or
Speaker 1: other particles, and you detect particles in exactly this same way.
Speaker 1: The particle passes through the detector and it leaves a
Speaker 1: trail of electrons behind it, which we then slurp off
Speaker 1: and use that as evidence to say, hey, there was
Speaker 1: a particle that passed through, So we should maybe think
Speaker 1: about rebranding it that way too, Like, don't call them
Speaker 1: solar panels, call them melon absorbers, particle detectors, particles. Yeah,
Speaker 1: who doesn't want a particle detector on the roof? And
Speaker 1: you know the same basic principle works also in every
Speaker 1: digital camera, right, That's how digital camera turns a photon,
Speaker 1: which is the picture you're seeing, into an electrical signal,
Speaker 1: which is what your computer needs to record it. The
Speaker 1: photovo take effect. It turns a photon into little electrons
Speaker 1: which then get gathered up at the edge of your
Speaker 1: little pixel and recorded as evidences stead of photon came
Speaker 1: through as like, oh, that's right. Yeah, that means everyone
Speaker 1: who has a camera on their phone has a solar
Speaker 1: panel in their pocket. That's right, that's right, except that
Speaker 1: it draws power instead of generating it. Unfortunately, it generates images,
Speaker 1: but it doesn't generate power. Does I mean I have
Speaker 1: a giant camera on my roof taking pictures of the
Speaker 1: sun every day? Absolutely? And you know we have done
Speaker 1: the calculations. Can you use solar panels as particle detectors?
Speaker 1: Could we use everybody's solar panels? Is like a huge
Speaker 1: telescope to understand cosmic rays. Unfortunately you can't because you're
Speaker 1: swamped by the photons from the Sun which make a
Speaker 1: huge signal. And everything else we're interested in, like little
Speaker 1: muans or positrons or protons, is swamped by that huge
Speaker 1: blinding light from the sun. But it does you're you're saying,
Speaker 1: my solar panels do detect these other particles. It is
Speaker 1: technically like catching them and converting them to a signal.
Speaker 1: It totally is. If you covered your solar panels, if
Speaker 1: you made them light proof, which would be terrible for
Speaker 1: your electrical efficiency, But if you made them light proof
Speaker 1: and cover them up so they were in a black box,
Speaker 1: then they would be great detectors for muans or other
Speaker 1: kinds of particles that could penetrate that seal and leave energy. Interesting.
Speaker 1: All right, I am ready to do scientific experiments at
Speaker 1: the expense of actually generating any electricity. Wow, some sacrifices
Speaker 1: might have to be made. How important is science to you?
Speaker 1: All right? Well, um, that's sort of how they work.
Speaker 1: I guess. Maybe a question is they're pretty great, but
Speaker 1: why aren't there more of them out there? Why doesn't
Speaker 1: everyone jump into this solar energy bandwagon. Is it political
Speaker 1: or are there other limitations? There are some other limitations.
Speaker 1: You're right there, pretty great, but there are some downsides
Speaker 1: to solar panels. One is that the sun is not
Speaker 1: always above you in the sky. Right, Sometimes there are
Speaker 1: clouds or it's night time, and so you're generating power
Speaker 1: whenever the sun is above your solar panels. But that's
Speaker 1: not always the case, and you need power some times
Speaker 1: at night or when it's cloudy, and so you need
Speaker 1: a complicated system there to buffer, to gather energy into
Speaker 1: like a battery, and to save it for you for
Speaker 1: when you need it. Right, But that's not really a negative.
Speaker 1: It just means that, you know, you need a like
Speaker 1: a buffer, you need like a something that stores it
Speaker 1: like a battery. Yeah, but it adds to the cost,
Speaker 1: you know, just like the transport issues. Say, for example,
Speaker 1: you have a huge solar panel array out in the
Speaker 1: desert to gather energy really efficiently, then you need to
Speaker 1: send that energy hundreds or thousands of miles to where
Speaker 1: it needs to go because you have a mismatch sometimes
Speaker 1: between where the energy is used and where the energy
Speaker 1: is created. I mean, if every device could just create
Speaker 1: solar power whenever it needed it wherever it was. That
Speaker 1: would be awesome. But one of the main costs of
Speaker 1: solar power is fabricating the devices themselves, of course, which
Speaker 1: is not trivial and not cheap, but also transporting and
Speaker 1: buffering building these batteries. You know, battery technology is complicated
Speaker 1: and also quite toxic, right, but I think that you
Speaker 1: know you need to do these things anyways for any
Speaker 1: kind of power, don't you Like, do you still need
Speaker 1: the infrastructure for um, burning coal or for nuclear powered energy? Right? Well,
Speaker 1: you know you can turn your coal power plant on
Speaker 1: any time of day or night, right, and so it
Speaker 1: can be a much steadier source of power doesn't have
Speaker 1: these fluctuations. You don't need the same kind of buffer
Speaker 1: for a coal power plant. A coal power plant, essentially
Speaker 1: the energy is already in a battery. That battery is
Speaker 1: called coal, and it's available for whenever you need it.
Speaker 1: You just have to transform it into electricity. Now, of course,
Speaker 1: coal is terrible for lots of other reasons. I'm not
Speaker 1: selling coal. But one of the disadvantages of solar power
Speaker 1: is that it's not always created when you need it, right, right,
Speaker 1: But fortunately I'm mostly asleep at night. Well, actually, that's
Speaker 1: not true for me, but I think for most of humanity,
Speaker 1: you're sort of asleep at night, so you don't actually
Speaker 1: use that much energy at night, right, and it's cooler
Speaker 1: and you so you don't need the a C. Really like,
Speaker 1: I think most people's power consumption matches sort of daylight. Yeah.
Speaker 1: Do you use less power when it's cloudy outside, Yeah,
Speaker 1: because you know you don't need to your house as
Speaker 1: much right now, You're absolutely right. It's not a killer
Speaker 1: for solar power for sure. It just means, you know,
Speaker 1: you have to build this infrastructure and you have to
Speaker 1: have batteries, you have to do this kind of stuff.
Speaker 1: But you're right, people use more energy when it's daytime,
Speaker 1: and they need more A C when it's sunny outside,
Speaker 1: and so that's not that big an issue. Well, obviously
Speaker 1: it's not like free energy, and it's not super simple
Speaker 1: to get solar energy, but it's still I think overall,
Speaker 1: it's it's renewable, right, and we don't create carbon emissions,
Speaker 1: and still more positive than most other sources of energy, right, absolutely,
Speaker 1: And it's getting cheaper, you know, the more we work
Speaker 1: on it, the easier it is to fabricate these solar panels,
Speaker 1: they last longer, they're more efficient, they're cheaper, they're easier
Speaker 1: to produce, and it's sort of something that builds on itself.
Speaker 1: The larger the market is, the more companies get involved,
Speaker 1: the more competition there is, the more clever engineers get
Speaker 1: on board from making these things effective, the better batteries get.
Speaker 1: It seems like an excellent option for the future. It
Speaker 1: just takes sort of an investment. It just takes us
Speaker 1: deciding to make this happen. Yeah, and it's like we're
Speaker 1: getting this energy from space for free. It feels great
Speaker 1: to you. It does, and there's lots of really fun
Speaker 1: ideas for how you could tap into it. You know,
Speaker 1: you don't need to build a huge array of solar
Speaker 1: panels in the middle of your city. You can put
Speaker 1: them in the desert. We have lots of huge areas
Speaker 1: of the earth where nobody's living because it's just sand,
Speaker 1: and you could put vast solar arrays there. You can
Speaker 1: even have them like floating on things in the ocean,
Speaker 1: just gathering up solar energy. So if you built enough
Speaker 1: infrastructure there, you could really power a lot of our
Speaker 1: civilization's energy needs. Yeah, and create a lot of shade
Speaker 1: in the desert, which would be pretty good probably for
Speaker 1: all the animals there. All right, well that's sort of
Speaker 1: the big picture and the little picture of solar power.
Speaker 1: And we're gonna do something a little bit interesting next,
Speaker 1: which is compare them to photo synthesis. But first, let's
Speaker 1: take a quick break. All right, we're talking about solar power,
Speaker 1: and we talked about how solar panels work, and so, Daniel,
Speaker 1: you thought something interesting would be too, sort of compare
Speaker 1: this man made machine and device that we've made to
Speaker 1: capture solar energy to what nature has done. Plants use
Speaker 1: solar power and so through something called photosynthesis, And so
Speaker 1: how do the two compare. Do they use a similar
Speaker 1: mechanism or is it totally different? Yeah? I thought this
Speaker 1: was really fascinating because, you know, we've been working on
Speaker 1: this technology for decades, but nature has been doing this
Speaker 1: for literally billions of years, and it's got a really
Speaker 1: refined process for making things more efficient and more effective
Speaker 1: in finding solutions. And so naively, I thought to myself, well,
Speaker 1: I'm sure that our efficiency is pretty good, but Nature's
Speaker 1: efficiency must be even higher because it's been fine tuned
Speaker 1: for for so long. But you know, you start to
Speaker 1: read about photosynthesis, and you discover that it's actually less efficient,
Speaker 1: that a smaller fraction of the light that comes from
Speaker 1: the sun and hits a plant gets turned eventually into energy,
Speaker 1: and it's using a completely different process. So they're not
Speaker 1: as good as solar panels, I guess, and absorbing energy,
Speaker 1: I guess. They don't have the advantage of like having
Speaker 1: silicon and all these dope materials and highly engineered materials.
Speaker 1: How do they work? How do plants absorb? Some might Yeah,
Speaker 1: you're right. The plants don't necessarily have access to some
Speaker 1: of the rarer elements that we use to dope our
Speaker 1: silicon to make these diodes work. What they do is
Speaker 1: they have the light come in and it interacts with
Speaker 1: carbon dioxide and water inside the leaf, and essentially what
Speaker 1: it does is it builds a sugar. They turn light,
Speaker 1: not into electricity, because plants aren't interested in electricity. They
Speaker 1: don't run air conditioning or sit on their phones all day. Right.
Speaker 1: It basically turns light into plant food, which is these
Speaker 1: complex carbohydrates, these carbons and hydrogens and oxygen's all built
Speaker 1: together into things that are fiber or what we would
Speaker 1: call sugar. They do it through chemistry. Like you know,
Speaker 1: they have the ingredients, they're sort of on the leaf,
Speaker 1: and then the sunlight triggers a reaction or triggers like
Speaker 1: a molecules kind of coming together. Yeah, exactly. Chemistry is
Speaker 1: all about energy flows, right, So you can store energy
Speaker 1: in chemical bonds. You can build something that has energy
Speaker 1: inside of it, but then you need to put the
Speaker 1: energy in. Right. You can't just have the ingredients. They're
Speaker 1: sort of like baking a cake. You can just mix
Speaker 1: the ingredients. You need to supply the heat. And so
Speaker 1: in order to make these sugars, these sugars which store energy,
Speaker 1: you need to bring the wrong ingredients together, which is
Speaker 1: carbon dioxide and water, and then you need to apply
Speaker 1: the energy. And that's where the photon comes in. As
Speaker 1: the photon comes in and chemistry happens, and then you
Speaker 1: get out, You get sugar, and you get oxygen as
Speaker 1: a byproduct, which is wonderful for all of us oxygen breathers, yeah,
Speaker 1: and all of those salad eaters. Yeah, and for the
Speaker 1: plant specifically. It's basically turned the energy into plant food. Right.
Speaker 1: So we want to generate electricity and plants. What they
Speaker 1: want to do is they want to generate these sugars.
Speaker 1: And really the answer to the question of you know
Speaker 1: why is photosed in this is less efficient than solar
Speaker 1: power is really that they're doing different things. Plants have
Speaker 1: optimized turning photons into plant food, into this fuel which
Speaker 1: they can store and then very easily use later on,
Speaker 1: whereas we've optimized for creating these electrons which we can
Speaker 1: either use immediately or try to funnel into batteries. It's
Speaker 1: almost like they've invented the battery and the panel at
Speaker 1: the same time. Yeah, it's really pretty impressive technology. Right.
Speaker 1: This plant fuel is a great way to store energy,
Speaker 1: and so it's a really nice thing for them because
Speaker 1: they can use it whenever they need it. They don't
Speaker 1: have to worry about creating the battery. Right And if
Speaker 1: I get takes carbon diotside from the era, yeah exactly
Speaker 1: and produces oxygen and delicious vegetables and delicious vegetables exactly.
Speaker 1: And you know it also it captures a different fraction
Speaker 1: of the solar energy. Like photobole take cells, the ones
Speaker 1: that we build, they can capture energy that's out of
Speaker 1: the visible spectrum. You don't have to be able to
Speaker 1: see the photon for your solar panel to be able
Speaker 1: to slurp it up and turn it into electricity. You
Speaker 1: can also captured the energy of photons that have a
Speaker 1: wavelength it's too long they're in the infrared, or photons
Speaker 1: that have a wavelength it's too short there in the
Speaker 1: ultra violet. Your photovolt take cells made from silicon can
Speaker 1: slurk that up. Plants are mostly sensitive to the visible spectrum,
Speaker 1: so they get sort of a smaller slice of all
Speaker 1: the light that comes in. But I think solar panels
Speaker 1: also use a photo will take effect a little bit similar.
Speaker 1: I mean, they're optimized for certain wavelengths, right, Yeah, I
Speaker 1: mean we certainly are optimized for the wavelengths that come
Speaker 1: from the sun. Right. They've chosen a material that can
Speaker 1: absorb it, and you're right, this is quantum mechanical, and
Speaker 1: so you can't absorb just any photon that comes in.
Speaker 1: It has to be a good match for the material,
Speaker 1: because every material has certain wavelength of light it can
Speaker 1: absorb and other wavelengths it's transparent to. And so one
Speaker 1: of the reasons silicon has chosen it's not just because
Speaker 1: it's a semiconductor, but because they can absorb light in
Speaker 1: the wavelength that's hitting the earth. So plants aren't as efficient,
Speaker 1: but they're pretty good at other things, right, Like a
Speaker 1: plant you know, need to hose it down when it
Speaker 1: gets too dusty. That's right. Plants are a much nicer
Speaker 1: option compared to solar panels in some way because, for example,
Speaker 1: they build themselves. Right if you could just sprinkle like
Speaker 1: solar panel seeds on your roof and they like sprouted
Speaker 1: up and created working solar panels, that would be pretty awesome.
Speaker 1: That would be pretty awesome. Yeah, that sounds like crazy
Speaker 1: science fiction, right, but that's basically what plants can do.
Speaker 1: They self assemble from a seed. Ma. You ever look
Speaker 1: at it like a huge tree and wonder like where
Speaker 1: did all this stuff from that tree come from? Well,
Speaker 1: that tree has basically built itself out of the air.
Speaker 1: It has pulled the carbon out of the air to
Speaker 1: construct itself. That's pretty awesome engineering. You know, without any supervision,
Speaker 1: no project management, no Excel spreadsheets, you know, no invoices,
Speaker 1: no meetings. It just did it. That's the most attractive
Speaker 1: part to you right now, Like no zoom meetings were
Speaker 1: required to make this tree. That's that's the apex of
Speaker 1: of cleverness and a cheatment there, yeah, exactly. And and
Speaker 1: on top of that, they fix themselves. You know, if
Speaker 1: you shadow your solar panel, you can't come back the
Speaker 1: next day and see it started to heal. But if
Speaker 1: a leaf falls off your plant, it'll just grow a
Speaker 1: new one, you know, it'll just fix itself. So they're
Speaker 1: really pretty awesome, and they can be grown basically anywhere
Speaker 1: using the materials readily at hand. You don't have to
Speaker 1: mind this delicate material out of the crust of the earth.
Speaker 1: So I've got a lot of good things to say
Speaker 1: about plants. And even though technically their energy transmission rate
Speaker 1: is less efficient than photovoltaic panels, they're pretty awesome. Yeah. Now,
Speaker 1: for sure, plants are amazing, But they can't power my
Speaker 1: computer or our podcast recorder here, No, not directly. But
Speaker 1: you know, there are folks who are working on electric leaves.
Speaker 1: What what do you mean? These are mechanical devices or
Speaker 1: electrical devices that are trying to replicate photosynthesis instead of
Speaker 1: replicating you know, photovoltaic process. So you have the stuff
Speaker 1: inside this device, basically water and carbon dioxide, and you
Speaker 1: want to replicate photosynthesis to produce sugar and oxygen. So
Speaker 1: electric leaf is different from a photovoltaic cell, right, So
Speaker 1: it will produce sugar as an output. Like you can
Speaker 1: have a sugar factory on your roof. You feed in
Speaker 1: carbon dioxide and water and sunlight, and yes, it will
Speaker 1: give you sugar and oxygen. So there's a whole group
Speaker 1: of folks working on these artificial leaves instead of working
Speaker 1: on photobo take cells. Interesting, so you can put it
Speaker 1: in your cold coffee because you don't have any electricity
Speaker 1: to heat it up. Yeah, but you know, artificial leaves
Speaker 1: still do not grow themselves or fix themselves, and there
Speaker 1: are a lot more expensive than a seed. So it's
Speaker 1: a tough engineering challenge to beat nature at its own game. Yeah. Well,
Speaker 1: what if Daniel, you build like a factory with AI
Speaker 1: that makes its own solar panel to power itself. That
Speaker 1: would be sort of like making a self growing solar panel. Yeah.
Speaker 1: If you design robots that could build solar panels and
Speaker 1: manage them and fix them, then yeah, that would be
Speaker 1: pretty awesome. That's kind of what a plant is, isn't it.
Speaker 1: It's like a little robot. I mean, it's just following
Speaker 1: the instructions in the DNA. It's just kind of like
Speaker 1: a little robot that's following its own instructions. Yeah, it's
Speaker 1: a little organic, evolved robot. But then I guess so
Speaker 1: are we, right until your AI goes crazy and then
Speaker 1: just covers the whole planet with solar panels, right, which
Speaker 1: would be give us a lot of energy there you go,
Speaker 1: but to be nobody to use it, right, like sorry,
Speaker 1: or have to knock down your house to build solar panels.
Speaker 1: Those are my instructions. Well, I can live under the panel.
Speaker 1: I'm just saying. You know, I'm imagining this science fiction novel,
Speaker 1: a future dystopia where we all live in the darkness,
Speaker 1: but we have a lot of energy from the solar panels. Yeah,
Speaker 1: well you can build windows. I mean, come on, they
Speaker 1: can spare a few percentage of the square footage there
Speaker 1: and then the robot comes along and filled it in
Speaker 1: with a solar panel. Alright, a little off topic here.
Speaker 1: So solar panels, Yes, they take sunlight and converted to electricity,
Speaker 1: and they do it through these silicon sir kids. But
Speaker 1: you know, they take some infrastructure, but overall, the infrastructure
Speaker 1: sort of worth it, right because it's clean energy, absolutely,
Speaker 1: and the infrastructure can get cleaner and simpler and cheaper.
Speaker 1: That's an engineering that's a technology barrier. It's not something
Speaker 1: fundamental to the process, like with nuclear fission, which will
Speaker 1: always produce some toxic waste, or with fossil fuels, which
Speaker 1: will always release some sort of carbon. This at its
Speaker 1: core is a really clean, cheap source of energy that's
Speaker 1: already produced and being beamed to us from the facility
Speaker 1: ninety million miles away. Yeah, and it's a guilt free
Speaker 1: that's right. It's negative guilt. So you can turn on
Speaker 1: your solo panel and have an extra box of cookies.
Speaker 1: There you go, and the electric company will send you
Speaker 1: a box of cookies every month or money, whichever you prefer.
Speaker 1: All right, well, we hope you enjoyed that. Thanks for
Speaker 1: joining us, see you next time. Thanks for listening, and
Speaker 1: remember that Daniel and Jorge explain. The univer is a
Speaker 1: production of I Heart Radio. Or more podcast from my
Speaker 1: heart Radio. Visit the I Heart Radio app, Apple Podcasts,
Speaker 1: or wherever you listen to your favorite shows.