Speaker 1: Can technology with box Stuff from hastuftfom. Hey there, and
Speaker 1: welcome to tech Stuff. I am your host, Jonathan Strickland,
Speaker 1: and today I thought I would look back on a
Speaker 1: topic that we've covered a few times on Tech Stuff
Speaker 1: in multiple ways, and that's solar power. So we've talked
Speaker 1: about solar power and lots of different episodes. We covered
Speaker 1: the unlikely solar freaking roadways, which we felt were uh,
Speaker 1: unrealistic is probably the best way I can describe that
Speaker 1: in our opinion, and then we also talked about the
Speaker 1: solar Impulse airplane. We've talked about solar panels and their efficiency.
Speaker 1: Today I want to talk a little bit about solar towers,
Speaker 1: which is a different way of harnessing the Sun's energy,
Speaker 1: and I think it's a really clever way as well,
Speaker 1: because it doesn't rely on sunlight hitting a panel. Obviously,
Speaker 1: the big big drawback to that approach is when the
Speaker 1: sun isn't hitting a panel, you're not generating any electricity. Right,
Speaker 1: So if it's super cloudy or if it's nighttime, if
Speaker 1: the sun is not able to hit the panel, the
Speaker 1: sunlight is not getting there, you have nothing to convert
Speaker 1: into electricity, and your solar panels go on to be
Speaker 1: unused for that duration, so that can be really rough
Speaker 1: if you have a long stretch of overcast days, or
Speaker 1: you live in a place where you don't get solar
Speaker 1: exposure at your house because of maybe they're taller buildings
Speaker 1: around you, or trees or whatever it may be. Maybe
Speaker 1: you have a north facing house rather than a south
Speaker 1: facing house here in the Northern Hemisphere. If you have
Speaker 1: a south facing house in the Northern Hemisphere, you're going
Speaker 1: to get more solar exposure than a north facing house,
Speaker 1: So solar panels have that drawback there. Also, there's efficiency
Speaker 1: issues with solar panels. When we talk about efficiency, what
Speaker 1: we mean is how much of the sun's energy can
Speaker 1: we actually convert into electricity and how much of it
Speaker 1: do we lose? How much of that energy bounces off
Speaker 1: the panel and we do not capture it. Most commercial
Speaker 1: solar panels, the kind that you would put on your house,
Speaker 1: the efficiencies around eleven, meaning that you're losing a lot
Speaker 1: of that energy not is not converting into electricity. What
Speaker 1: that means is that you have to buy more solar
Speaker 1: panels to cover more space, to collect more solar energy,
Speaker 1: to generate enough electricity to meet your needs. Obviously, if
Speaker 1: solar panels were efficient, which is impossible, by the way,
Speaker 1: physically impossible. People have proved it with math. Then if
Speaker 1: you if it were a hundred percent efficient, you wouldn't
Speaker 1: need as many solar panels in order to do what
Speaker 1: you need to do. That's just not the case in reality,
Speaker 1: so instead we often have to buy more than what
Speaker 1: we would cover a larger area. And even then again
Speaker 1: you're limited to collecting electricity or generating electricity i should say,
Speaker 1: during the daylight hours. And electricity also is a use
Speaker 1: it or lose it kind of thing, meaning that if
Speaker 1: you don't have an immediate use for that electricity and
Speaker 1: you don't have a way to store it, you lose
Speaker 1: that electricity. You have to use it when it's generated,
Speaker 1: So you need to have some sort of battery system
Speaker 1: as well, so that in the times when you're not
Speaker 1: using the electricity you're generating, you can still save it
Speaker 1: for later use. And until recently, batteries have been really
Speaker 1: expensive for the home, but Tesla's power wall has kind
Speaker 1: of led a revolution in that space, and we're starting
Speaker 1: to see more affordable versions of batteries hit the home market. Okay,
Speaker 1: all of that's out of the way to just say
Speaker 1: that the traditional solar panel approach has its drawbacks. Now,
Speaker 1: let's talk about solar towers, because they take a totally
Speaker 1: different approach to harnessing electricity from the sun, and it's
Speaker 1: really pretty clever, and they can harness electricity or they
Speaker 1: can generate electricity day or night. So you might wonder,
Speaker 1: how is that possible when when the Earth rotates so
Speaker 1: that the sun is no longer shining on a solar tower,
Speaker 1: where is that electricity coming from? So here's the way
Speaker 1: it works. Now. I'm largely going to refer to a
Speaker 1: company called Solar Reserve, which is here in the United States.
Speaker 1: Solar Reserve is just one company that is building structures
Speaker 1: like these around the world, So I don't mean to
Speaker 1: suggest they're the only one. I'm using them as the
Speaker 1: example because that so much of their information is available
Speaker 1: to actually read about and understand. So it's a really
Speaker 1: helpful approach. Solar towers. Well, first of all, the name
Speaker 1: kind of gives away the main feature. There's a tower
Speaker 1: at the center of this, uh structure or really multiple structures.
Speaker 1: So how tall are these towers? Will? According to solar reserve.
Speaker 1: The height of the tower and it's thermal risk fiver
Speaker 1: more on that in just a second. Tends to be
Speaker 1: sixty feet combined or about one So you've got this
Speaker 1: tower in a a large area. You want to have
Speaker 1: an area that gets a lot of solar exposure, otherwise
Speaker 1: this is not a practical way of generating electricity. So
Speaker 1: imagine like a desert, nice flat desert, lots of sunlight
Speaker 1: hitting that desert every typical day, and you have a
Speaker 1: tall tower with a receiver on the top of it.
Speaker 1: Now that receiver is actually a series of dark panels.
Speaker 1: And these aren't solar panels, not in the way that
Speaker 1: you would put on top of your house. They are
Speaker 1: not converting sunlight into electricity directly. Rather, they are panels
Speaker 1: that transfer thermal energy. In other words, they're all about
Speaker 1: transmitting heat. So these panels have sixty six thin wall
Speaker 1: straight tubes in them. Those tubes are designed to conduct
Speaker 1: heat from the outside to the inside of that tower.
Speaker 1: And the tubes are made out of a steel alloy
Speaker 1: that's covered in a high absorptivity black coating to maximize
Speaker 1: the amount of energy the panel can absorb. So you've
Speaker 1: got sunlight shining on this tower. Well, how is that
Speaker 1: enough to generate electricity on its own. It's not. In fact,
Speaker 1: what you end up doing is surrounding the tower with mirrors. Now,
Speaker 1: Solar Reserve uses mirrors that they call heliostats. These heliostats
Speaker 1: are mounted on h arms essentially that allow them to
Speaker 1: track the motion of the sun. That way, the mirrors
Speaker 1: maintain the ideal angle to uh to reflect the Sun's
Speaker 1: light directly towards the top of that tower at that
Speaker 1: receiving point of the tower on those panels. And we're
Speaker 1: talking about a lot of mirrors. Solar Reserve has one
Speaker 1: area it's called the Crescent Dunes that's there there um
Speaker 1: tower or that they have in the US, and the
Speaker 1: Crescent Dunes towers surrounded by more than ten thousand mirrors
Speaker 1: covering a fifteen hundred acre field. So this is a
Speaker 1: big operation. You've got to have a lot of open
Speaker 1: land for this to work. That's obviously one of the
Speaker 1: potential drawbacks, right that you need a place that's going
Speaker 1: to have a lot of solar exposure and you need
Speaker 1: to have enough space to make it makes sense. But
Speaker 1: assuming you have both of those things, you can do
Speaker 1: something pretty incredible. So what these mirrors do is direct
Speaker 1: that sunlight up at those dark panels I was talking about.
Speaker 1: Remember I mentioned there were fourteen. These fourteen panels are
Speaker 1: divided up into two groups of seven. Each group of
Speaker 1: seven represents kind of a circuit, and that circuit is
Speaker 1: not for electricity. It's rather for a circuit of pipes
Speaker 1: that are circulating liquid salts. So liquid salts are pretty cool, uh,
Speaker 1: which is a weird way of putting it when you're
Speaker 1: talking about thermal energy. But liquid salts can hold on
Speaker 1: to more heat than water can and can remain in
Speaker 1: liquid form, so in other words, they don't vaporize into steam.
Speaker 1: And what solar reserve does is it pumps around five thousand,
Speaker 1: eight hundred gallons of liquid salts per minute through the
Speaker 1: receiver circuits that run back and forth across the inside
Speaker 1: of these black panels. So imagine you've got this really
Speaker 1: tall tower. At the top of the tower, you have
Speaker 1: these fourteen dark panels, and then let's just take seven
Speaker 1: on one side. You've got seven of those dark pounds
Speaker 1: on one side. On the inside of those panels, you
Speaker 1: would see this criss crossing of a pipe that is
Speaker 1: circulating liquid salts through the pipe. Heat from the outside
Speaker 1: comes into the tower and it begins to heat those
Speaker 1: liquid salts running through that circuit. It's a simple heat transfer.
Speaker 1: And if you've listened to our podcasts about things like refrigera,
Speaker 1: raiders and air conditioners, you know about you know how
Speaker 1: this what the principles are, how how this is based
Speaker 1: same basic thing. You want to give as much surface
Speaker 1: area you know you want to you want to dedicate
Speaker 1: as much surface area as you can to heat and
Speaker 1: have the liquid salts cross over as much of that
Speaker 1: surface area as as possible to heat up the liquid salts.
Speaker 1: As the liquid salts move through the circuit, they become molten,
Speaker 1: so incredibly high temperatures. So the low side of the
Speaker 1: temperatures for these liquid salts is five fifty degrees fahrenheit
Speaker 1: or two degrees celsius. That's the low end. That's that's
Speaker 1: the chili side. If you want to talk about how
Speaker 1: hot they get, they can get up to a thousand
Speaker 1: fifty degrees fahrenheit or five hundred sixty six degrees celsius.
Speaker 1: That's really impressive. And so you've got this massive amount
Speaker 1: of stored thermal energy. It's all inside the molten salts.
Speaker 1: So you've got a lot of heat stored up. What
Speaker 1: good is heat, Well, you can use heat to do
Speaker 1: the same thing that is done in power plants all
Speaker 1: over the world. You use heat to turn water into
Speaker 1: steam and use the steam to turn a turbine, which
Speaker 1: generates electricity. It's an incredibly simple idea. It's the basis
Speaker 1: of almost every other type of power plant, with the
Speaker 1: exception of things like solar panels that are used in
Speaker 1: solar farms. Like that, that's generating electricity straight from sunlight,
Speaker 1: as opposed to using that electricity to somehow turn water
Speaker 1: into steam. That would be ridiculous. You would lose way
Speaker 1: too much energy in that approach. But things like coal
Speaker 1: fired plants, even nuclear power plants, you're talking about generating
Speaker 1: electricity by heating up water into steam and using that
Speaker 1: steam to turn a turbine to do work, and that
Speaker 1: turbine ends up being an electric generator and you get
Speaker 1: electricity from that. So the the purpose of the solar
Speaker 1: tower is really just to collect heat. That's it. It's
Speaker 1: not doing anything magical. It's just generating tons and tons
Speaker 1: of heat. I know that tons is not really a
Speaker 1: unit when it comes to heat or temperature. But you
Speaker 1: understand what I mean. It creates an enormous amount of heat,
Speaker 1: and the molten salts then go into a big storage tank.
Speaker 1: And it's pretty cool because that storage tank u ends
Speaker 1: up being a a way of holding onto the heat
Speaker 1: for a long time. According to Solar Reserve, the company
Speaker 1: says that the molten salt only loses one degree of
Speaker 1: fahrenheit or about point five five five, etcetera, etcetera degrees
Speaker 1: celsius in heat per day. So, in other words, if
Speaker 1: you have a long stretch of overcast days, you still
Speaker 1: have this massive that really tank. It's not a vat,
Speaker 1: it's a tank because it's completely enclosed of molten salts
Speaker 1: and they hold onto that heat, which means you can
Speaker 1: continuously pump that through your water tank in order to
Speaker 1: heat water up to and when I say pump, you
Speaker 1: pump it through. It's a very similar circuit that you
Speaker 1: would find at the top of the receiver. The molten
Speaker 1: salts don't mix with the water. Instead, you have a
Speaker 1: pipe that runs through the water tank. The molten salts
Speaker 1: run through the pipe and transfer some of their heat
Speaker 1: to the water through the material of the pipe. Itself,
Speaker 1: so you're not laying the molten salts in the water
Speaker 1: mixed together. That would be ridiculous. Instead, you're having the
Speaker 1: molten salts move through a pathway and as they move
Speaker 1: through that pathway, they heat up the water. The water turns,
Speaker 1: the steam turns the turbine. Then the steam goes through
Speaker 1: a condenser to condense the steam back into water and
Speaker 1: it goes back into the water tank. So once you
Speaker 1: use the molten salts to transfer some of this heat,
Speaker 1: they they've lost that thermal energy. They're now moving into
Speaker 1: a different tank. It's a tank to pump the liquid
Speaker 1: salts back up into the top of the tower. So
Speaker 1: the neat thing with this system is that you can
Speaker 1: use it to deliver electricity day or night. You've got
Speaker 1: so much stored heat. After you get the system up
Speaker 1: and running and it's generated enough molten salt, like it's
Speaker 1: created enough molten salt through this process to allow this
Speaker 1: to happen, you can deliver electricity on demand twenty four
Speaker 1: hours a day. And that's how all power plants work.
Speaker 1: They deliver electricity on demand. They're not uh set to
Speaker 1: a certain level, and then if you don't meet that level,
Speaker 1: they you know, just that electricity goes to waste. They
Speaker 1: base it upon what the current demand. And I don't
Speaker 1: mean that as a pun, but it came out of
Speaker 1: that way. Chris would be so proud. They don't. They
Speaker 1: respond to whatever the the demand is at that time
Speaker 1: to produce the amount of electricity needed. So super interesting
Speaker 1: way of doing this by using the sun as an
Speaker 1: energy source to create the heat needed to turn water
Speaker 1: into steam and turn a turbine, as opposed to a
Speaker 1: fossil fuel like coal or oil, or a nuclear fuel
Speaker 1: in the case of nuclear fusion. Now, if we ever
Speaker 1: are fission, I should say nuclear fission. I know all
Speaker 1: of you were ready to write in, and you should
Speaker 1: be because that was a silly mistake I made nuclear fusion.
Speaker 1: If we ever cracked that nut, solar towers may seem
Speaker 1: quaint in comparison, but that's a very difficult problem in
Speaker 1: physics to to solve. So we're still waiting on that.
Speaker 1: So the neat thing about this, obviously is that if
Speaker 1: you do have that amount of space, you can really
Speaker 1: offset a lot of a community's electricity needs with a
Speaker 1: solar tower. And uh, the company thinks that the lifespan
Speaker 1: of these solar towers is somewhere in the area of
Speaker 1: about thirty years, meaning that after thirty years you would
Speaker 1: have to start to replace parts because just of wear
Speaker 1: and tear, or they would not be as uh efficient
Speaker 1: as they had previously been. So, for example, those panels,
Speaker 1: if the panels become less efficient at transferring heat over time,
Speaker 1: you would definitely want to replace them because you would
Speaker 1: be transferring less heat to generate your your molten salts
Speaker 1: will be at a lower temperature. It would require more
Speaker 1: of them to turn water into steam. It become less
Speaker 1: efficient overall, So you have to make sure that uh
Speaker 1: you're all the parts are working very they're very few
Speaker 1: moving parts, which is awesome, but you have to make
Speaker 1: sure they're working throughout the lifetime of the facility and
Speaker 1: then obviously replace parts as needed. So the question then
Speaker 1: becomes doesn't make financial sense to switch over to using
Speaker 1: solar towers at least to offset electricity generation in a
Speaker 1: particular area. To answer that question, you have to look
Speaker 1: at a lot of different factors and it is way
Speaker 1: more complicated than just a simple yes or no. For
Speaker 1: one thing, how much solar exposure is the area getting. Obviously,
Speaker 1: if you're not getting a lot, then that's not going
Speaker 1: to be a good choice for solar towers or a
Speaker 1: good place to put a solar tower. I should say
Speaker 1: also not just where, and and you know what time
Speaker 1: of year do you get solar exposure? Those would be
Speaker 1: two big things. But how much does electricity cost in
Speaker 1: that region already? And the reason why you have to
Speaker 1: ask that question is if you were to provide electricity
Speaker 1: through the solar reserve system, would it make financial sense
Speaker 1: to make that switch? If coal is incredibly cheap in
Speaker 1: the area, then financially it might make more sense to
Speaker 1: stick with coal, even though we all know there are
Speaker 1: big environmental drawbacks to using coal. You create a lot
Speaker 1: of fossil fuels, you have a big carbon footprint that way,
Speaker 1: But it's hard to argue with the dollar cost of energy.
Speaker 1: If that dollar cost is higher with solar reserve, that's
Speaker 1: a tough sell because not everyone is willing to spend
Speaker 1: more money to keep their homes, uh, you know, supplied
Speaker 1: with electricity just so that they have a lower carbon
Speaker 1: footprint with the electricity generation. It's just the truth of
Speaker 1: the matter, and some people don't have the money to
Speaker 1: afford the luxury. Obviously, now, if solar reserve is able
Speaker 1: to be significantly less expensive than whatever the alternatives are,
Speaker 1: that's a huge win for solar towers. So it's a
Speaker 1: lot of different questions along those lines. Obviously, there are
Speaker 1: other questions to ask, like what is the carbon footprint
Speaker 1: of actually building the solar tower? But I would argue
Speaker 1: that whatever it is, it probably has significantly less than
Speaker 1: the carbon footprint produced over the lifetime of a coal
Speaker 1: plant or at gas plant or oil plant. Um. I
Speaker 1: think that's pretty a pretty fair assumption, but it still
Speaker 1: could be a very large upfront uh carbon footprint creation there.
Speaker 1: So that's kind of the approach that I wanted to
Speaker 1: talk about, this idea of being able to generate electricity
Speaker 1: twenty four hours a day using on power without it
Speaker 1: being a solar panel, and I thought it was a
Speaker 1: really cool approach to that, something that could really get
Speaker 1: around a tricky problem with solar power because I know
Speaker 1: a lot of critics point out, hey, if the sun
Speaker 1: is not shining, then you're not making electricity. Well that's
Speaker 1: true with your traditional solar panels, but not with solar towers.
Speaker 1: Assuming that you don't enter into some cataclysmic event where
Speaker 1: you've got crazy overcast skies for a really long time,
Speaker 1: in which case, if we do have that, we're gonna
Speaker 1: have other problems besides where we get our electricity. Um oh,
Speaker 1: and you might want to know how much electricity can
Speaker 1: one of these facilities generate. It would be good for
Speaker 1: me to tell you that. So Solar Reserves says that
Speaker 1: depending on the plant design, it can generate between fifty
Speaker 1: and two hundred megawatts of electricity, and one megawatt is
Speaker 1: enough power to supply around a thousand homes. So you're
Speaker 1: talking about with one solar tower facility, but between fifty
Speaker 1: thousand and two hundred thousand homes. Obviously, there are a
Speaker 1: lot of cities that are bigger than that, and in
Speaker 1: order to supply the electricity for those cities, you would
Speaker 1: need multiple solar tower facilities to to do that. Uh.
Speaker 1: And again that's another question is where would this be
Speaker 1: most appropriate. Obviously a lot of desert towns that have
Speaker 1: medium to small populations. This would be an amazing approach
Speaker 1: to generating electricity, but it might not work for some
Speaker 1: place like New York City for multiple reasons, the population size,
Speaker 1: the lack of land to dedicate to solar power, Obviously,
Speaker 1: that's another issue is that if you are going to
Speaker 1: dedicate land to a solar tower facility, you're not able
Speaker 1: to use that land for other stuff, at least not easily,
Speaker 1: So that's another consideration. Obviously, you don't want to end
Speaker 1: up going to a place where you're dedicating land that
Speaker 1: could be otherwise used for a more productive purpose, possibly
Speaker 1: not in g related. It might be food related, or
Speaker 1: water or something along those lines. So a lot of
Speaker 1: things to take into consideration. But I think it's a
Speaker 1: very elegant approach to generating electricity in a using a
Speaker 1: renewable resource the Sun's energy, and very low impact to
Speaker 1: the environment. The moulten salts are inert, they're not dangerous. Uh.
Speaker 1: They're obviously dangerous in their temperature. You would not want
Speaker 1: to touch them while they're at a thousand fifty degrees fahrenheit,
Speaker 1: but they're not dangerous to the environment. Uh. And these, again,
Speaker 1: the systems are separate. The water system and the salt
Speaker 1: system are separate from each other. So I think it's
Speaker 1: a really interesting approach. Now I'm curious to hear what
Speaker 1: you guys think about the most promising energy sources for
Speaker 1: the future. Do you really think that solar power is
Speaker 1: going to become a major way to offset our electricity generation.
Speaker 1: I'm pretty sure. I feel fairly confident it's never going
Speaker 1: to be the primary way we generate electricity. I don't
Speaker 1: think it's practical enough to be our primary, but I
Speaker 1: certainly see it as a very strong contender for a
Speaker 1: support system, something that can offset some of our electricity needs.
Speaker 1: But what do you think? Do you think there are
Speaker 1: other ones that are better? Do you think wind power
Speaker 1: is better than solar or maybe, uh, maybe you think
Speaker 1: hydro power is better, Maybe you think geothermal. Maybe you're
Speaker 1: looking for that nuclear fusion approach. If that break If
Speaker 1: there is a breakthrough nuclear fusion, that would be an
Speaker 1: enormous benefit to all of humanity because we would suddenly
Speaker 1: be capable of going into an era of energy surplus,
Speaker 1: which would be phenomenal. And I hope it happens, But
Speaker 1: there are a lot of challenges to get out of
Speaker 1: the way first. And maybe I'll do a full episode
Speaker 1: about nuclear fusion in the in the future and talk
Speaker 1: about why it's such a tricky issue. But guys, I
Speaker 1: want to hear what you think. Where do you think
Speaker 1: the future of our energy comes from let me know,
Speaker 1: send me an email, our addresses, text stuff at how
Speaker 1: stuff works dot com, or drop me a line on
Speaker 1: Facebook or Twitter. At both of those, you can find
Speaker 1: me with the handle text stuff h s W and
Speaker 1: I'll talk to you again really soon. For more on
Speaker 1: this and Bathans of other topics, is a house stuff
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