The universe provides so much power, yet we
struggle to tap it and crave more. Instead of being powerless, let’s get off
Earth and conquer space. So today we continue the Upward Bound series
and our look at how to get into space cheaper and easier, and what we can do up there once
we can place stuff in orbit more cheaply. Of course, if you’re up in space for a while
you’ll need a reliable power supply, and that generally means either solar or atomic. In terms of the latter, fusion is a good option
if we can ever get it working, but fission is not something folks want in orbit overhead
in large quantities. The big weaknesses of ground-based solar are
that it’s useless on cloudy days and at night, but this is an area where being in
space is actually a major advantage. When we refer to the dark void of space, we’re
being more poetic than accurate. Space near Earth is constantly lit brighter
than the noon-time Sun, and indeed you’d have to get out beyond the Asteroid Belt before
solar stops being as effective there as it is on most of Earth. The equivalent of darkness in space depends
on your distance from the Sun, or if something’s in between you and the Sun, placing you in
the object’s shadow. While any object in a classic Low Earth orbit
is spending a lot of its time in the relatively large shadow of the planet, as you get further
away less of your orbital path is in that shadow. Additionally, various non-circular obits,
or locations like the Lagrange points, have little to no time in shadow, eliminating most
or all of the downtime experienced by solar panels situated on the Earth. As for wearing down over time, solar panels
on Earth have to contend with dust, rain, snow, hail, sandstorms, thermal fluctuations
and other weathering, none of which are present in the vacuum of space - and, needless to
say, there are no clouds there either. The total benefit is about seven times more
kilowatts-hours per year from a given Photovoltaic solar panel. Perpetual lighting also eliminates most of
the need for batteries. All of which makes solar an excellent choice
for space. It’s much more attractive than on Earth,
and of course we’re interested in getting that energy to Earth, whether beamed down
or otherwise, and eventually to other places in space. This idea has been looked at a lot for decades,
but is becoming increasingly feasible now that launch costs are plummeting. For this to be practical though we have to
overcome certain issues, and we should start by laying those out. First and foremost, getting stuff into space
is expensive. Doing that cheaper is, after all, what this
series is mostly about. A solar panel in space might be several times
more effective than one on Earth, but if you needed to spend hundreds of times more money
to get that panel up there, while it remains useful for powering things up there, it wouldn’t
really make sense to beam it down. Not when you can far more easily deploy and
maintain conveniently-sized arrays of panels down here. But down here you have to add energy storage,
which is several times more expensive than PV panels, if you want to compare apples to
apples. Second, there is the question of how you beam
that energy down, and this comes with a lot of problems. For instance if you’re beaming down with
a visible-light laser, it still has to go through all that air and clouds. There is also an additional effect called
thermal blooming that causes laser light to be absorbed by the atmosphere over any significant
distance, at least for frequencies that interact with the atmosphere. You also lose energy at every stage of the
process, as you convert sunlight to electricity, then into lasers, then down to Earth through
the atmosphere, into a collector there, and back into electricity again. We’ll be looking at these problems, some
solutions, and some alternatives to visible light today in greater detail. But that brings up a third issue, which is
safety. A big giant laser is also known as a death
ray, and with any power-beaming system, you are directing a lot of energy into a potentially
small place. This is a serious problem if your beam goes
off target from the collector, and over to a city, be that as a result of an accident
or deliberate action. So we will be looking at ways you’d be trying
to make one safe to use. It is also worth remembering though that a
giant laser in space also has some handy uses, like blowing up incoming asteroids or space
junk, not to mention it’s a great way to push spaceships up to high speeds, so we will
also be discussing some of the non-terrestrial uses of power-satellites later on, though
our main focus is getting energy to Earth. At this point, we have to start considering
scale. At present, humanity uses energy, from all
sources combined, at an average power rate of about 18 terawatts, 18 million megawatts,
not including the solar energy used by photosynthesis and evaporation. That’s about 2400 watts per person, day
in and day out, every day, and while we are getting a lot more efficient with power usage,
we also have a lot of people in developing regions who don’t use much yet and hopefully
will in the future; hopefully not too much or too soon though because our main method
of power generation has concerns about heating up the planet. We should start with a note there then, as
folks often worry about power satellites heating the planet by adding more energy, which of
course they do. The thing is, it isn’t our direct use of
energy that’s heating the planet. While we use energy at an 18 terawatt rate,
Earth receives about 10 thousand times that energy from sunlight. The extra heat we add would be trivial on
its own. The concern is with greenhouses gases being
released and trapping an additional fraction of the solar energy, not the extra energy
we consume directly. However, power satellites are solar-powered,
so were that a concern you could just have them block incoming light to Earth, cutting
down on how much reaches us. Not that you’d bother, since you could easily
use a mirror to do the job, which is cheaper, thinner, and a lot less complex for such a
geoengineering purpose. 18 Terawatts is a huge amount of power, and
even our most efficient experimental solar panels, those still being worked on in the
lab, would only get about 600 watts per square meter, in orbit. To get up to 18 Terawatts, you’d need 30,000
square kilometers of our best panels, or a single panel 100 kilometers in radius. That wouldn’t include any losses in transmission
either. Fortunately, we can assume high-efficiency
panels are used, as the single biggest cost to deploying a power satellite is launch cost,
which we’ll discuss in a moment. Solar panels will continue to get lighter,
cheaper, more durable, and more efficient as times goes on. But for the moment, if we use our top end
figures for performance, we can do a panel with thickness as low as 2 millimeters, massing
only about 2 kilograms a square meter and generating about 600 watts per kilogram in
space, constantly. To get 18 trillion watts out of 600 watts
per square meter would require 30 billion square meters or 30,000 square kilometers,
at an approximate mass of 60 billion kilograms. At current launch costs, that could run nearly
a hundred trillion dollars, and doesn’t include any losses in transmission or other
associated equipment. However, these would likely have a lifetime
of 20-30 years, and since the energy sector is several trillion dollars a year, with estimated
figures varying widely, spread out over 20-30 years this would already be approaching a
competitive cost. As manufacturing continues to improves and
launch costs drop, this could get us into the economically feasible zone for power satellites
rather quickly, and now would seem a good time to start prototyping to see if this can
be made viable as launch costs drop. However, this is SFIA so we’re less interested
in the next decade then the next century, and the earlier episodes of this series discuss
many launch systems that we already have the tech for that can drop launch costs to a tenth
or even a hundredth of what SpaceX’s Falcon Heavy can do. As a reminder, stuff like Jim Powell’s StarTram
or Keith Lofstrom’s Launch Loop or Paul Birch’s Orbital Ring are not all that high
tech, they just have a big upfront cost, many billions of dollars, which only looks big
since we don’t actually spend our relatively small space budget on launching truly massive
things. Our annual ground to space launch volumes
are tiny compared to a single day’s traffic through any major airport, and same as you
don’t build an international airport next to a small village, you don’t build these
kind of launch systems till you are ready to up your game and a launch a lot more, not
because they are particularly high-tech. When you are thinking about replacing a multi-trillion
dollar sector of the economy, options like those launch alternatives suddenly become
much more attractive and profitable. See those episodes for details, but even the
most expensive of them are offering launch costs smaller than the production cost of
the power satellites. It’s also worth noting that much of their
operational cost is electricity, which needless to say is altered when you’re launching
gigawatt-sized power generators into orbit. Additionally, most of the weight of a panel
is still silicon, the second most abundant element on the Moon’s Surface, right after
oxygen. Nor are solar panels incredibly tricky to
produce, especially when mass and efficiency isn’t much of an issue, and the moon is
close enough for us to do remote operations, so any factories there don’t need much personnel
physically present to operate, or sophisticated artificial intelligence. Before we move on, I should also note that
photovoltaics, turning photons into electricity the way a solar panel does, is not the only
way to turn light into electricity. We could, for instance, just concentrate light
on a liquid in pipes so it heats up, boils, and turns a turbine… a Thermal Powersat,
like the prize-winning Flowersat design. This is a viable way of generating power,
provided the light is sufficiently intense, and sunlight can be made incredibly intense. Thermal methods are how most power generation
occurs, using an atomic or chemical fuel source for heat instead of sunlight. If you can’t make cheaper solar panels,
you can always use a bunch of thin parabolic mirrors and non-imaging light funnels to focus
light on some substance to heat it and drive a fairly standard heat engine. Getting rid of the waste heat during the cycle
is harder, when you can only remove heat from a system in space by radiating it, but you
can still use cooling by conduction and forced convection inside it. The back side of all those mirrors can also
be used for radiating surfaces, too. Even surfaces exposed to sunlight can potentially
be used to radiate waste heat, by use of wavelength-selective surfaces. Okay, so we can collect it up there, but how
do we get it down? The traditionally suggested method is microwaves,
in a beam, which worries folks a bit since we all use those to heat up our food and they’ll
heat up a person, or a city, just as well. We’ll get to the safety issues in a bit. First, why microwaves? They are not the only option, but in terms
of our spectrum, the atmosphere does a very good job keeping out virtually all gamma and
X-ray radiation, and the overwhelming majority of Ultraviolet too, so they’re not great
wavelengths to use to get our energy past the atmosphere. Visible light goes through pretty well, obviously,
but much is still lost even in an open sky, and clouds obviously are murderous on visible
light transmission. Don’t discard it just from that though. Power satellites all around the planet can
just re-target their beams to collectors not obscured by the clouds, and only on the cloudiest
days would we not have clear sky windows which some powersats could use to get an angle on
the ground-based collectors. I should also note that we always want other
power generation methods and energy storage in any power grid anyway, so that some ground
based collectors being blocked by clouds sometimes is not really a deal-breaker for visible light. Nor do you necessarily need to beam light
down as a laser. A big parabolic dish concentrating light on
ground-based collectors is an option, too, which gets around thermal blooming that happens
when a high-powered laser enters a medium, like air, that’s absorbing some if it and
heating up and scattering the beam a lot. This, by the way, is a really big issue for
using ground-based lasers to intercept missiles or using lasers for ultra-high-bandwidth data
transmission over long distances. Since part of the point is to get power down
at night, using the visible range of the spectrum in broad diffuse beams could cause a lot of
light pollution, though in some places this might be advantageous. Of all the spectrum, radio waves are the ones
that basically ignore the atmosphere and clouds the most over all, and microwaves, which are
shorter than radio waves in wavelength, which is where the name micro comes from, are quite
good at going through our atmosphere, clouds or not. You might wonder about the danger of this,
but if you are accessing this episode over a wireless network, I should note that those
use microwaves too and the same frequency as your microwave oven. There’s nothing very special about that
frequency by the way, it just in a small band the FCC leaves free for non-broadcast purposes. Equipment operating at these frequencies is
also pretty efficient at converting between electricity and microwaves, especially compared
to lasers. You can do better than 75% with a magnetron
converting electricity into microwaves whereas laser efficiency, as much as it’s improved,
is still generally more like 50%. Our best new laser designs can almost match
that, but historically, lasers have been much less efficient. Microwaves remain better, but not by the same
overwhelming margin. Here’s the thing though, a Rectenna, a specialized
type of antenna for absorbing these microwaves and turning them back into electricity, has
an efficiency of at least 85%, much better than our best solar panels. This means that any side-effect environmental
heating from beamed-in microwaves will be much less as well. Now as to safety concerns, the general notion
is to beam the energy in at about 100 Watts per square meter, non-coincidentally what
OSHA says is the maximum safe workplace exposure amount. To get 18 Terawatts, and keeping in mind 15%
is lost in conversion by the Rectennas, would require about 200,000 square kilometers of
rectenna collector surface area. Sounds big, and indeed it is, that’s about
the size of Nebraska. Not that you’d be putting them all in the
same place. More to the point, that doesn’t really seem
much better than covering huge chunks of land with solar panels. Of course you could just increase power density,
and fence the place off, but you’d still be blowing birds away left and right and potentially
have a doomsday weapon. Though, realistically you could ramp the beam
intensity up an order of magnitude without producing too much of either problem. Birds would tend to avoid them as uncomfortable
or be able to swoop through before being hurt. This is mostly just raw heat damage like being
too near your fireplace, after all. However, the neat thing about a Rectenna is
that you can use multiple of them to cover a wide area, and this area is not entirely
lost to you, as a Rectenna is a mesh more like chicken wire than an opaque glass panel,
and tougher too. Indeed you could beam it right down on a city
and provide wireless power, though obviously you’d want to be careful about concentrating
it too much. Incorporating solar panels into roads and
parking lots obviously has extreme issues with durability, while sticking a layer of
chicken wire over farm fields or grazing land, isn’t difficult, nor is it that hard to
concentrate such beams to such sizes and keep them on target, nor will they torch a fiery
furrow through the landscape as they go. But the optical considerations of microwaves
mean that rectennas receiving gigawatts will necessarily be large, usually several kilometers
across. Safety is easily achieved by having the emitter
and collector handshake, and the beam just shuts off if it goes off target. I should probably note that an optical version
of this, using nanotech and metamaterials, called the Nantenna, shows promise of achieving
a 70% or higher conversion of optical light frequencies to electricity. The impact of this emerging technology on
solar panels, ground or space based, might be immense and very near at hand. Again though, this is SFIA. In this series, it’s only been a few episodes
since we were talking about Orbital Rings, the great big rings around planets for getting
into space once we want to be moving millions of people and megatons of cargo back and forth
between space and the ground on a daily basis. An Orbital Ring is far cheaper, kilogram for
kilogram, than any other options and you can scale it up immensely if you want to, unlike
rockets, where that kind of throughput would also produce enough pollution and heat to
mess with your climate. If you want to do a lot of travel from ground
to space, and you love your planet, you should put a ring on it. While the massive drop in launch costs is
certainly handy, the orbital ring also brings some benefits from being directly connected
to the planet below. You can run tethers and lines down to the
surface without making them of super-materials like graphene. Though you may still want to use graphene
in particular, since recent improvements are being made in producing it in bulk, and it’s
quite a good conductor of electricity. But the important point is that tethers going
from the ring to the planet need only be reasonably strong, not space-elevator strong, and don’t
have to be rigid or run in straight lines. Because of this, they can be built with some
extra features in mind, such as transmitting power, bringing people or cargo to and from
the cities near the ring, and can do so without a lot of the hassle of something like a rocket. You can’t launch a rocket anywhere near
a city, or any sort of spaceship meant for that kind of speed and acceleration, not without
damaging the city or even killing people, so you’d have to commute to a launch pad
far from that city and any of its suburbs. Alternatively an Orbital Ring tether can leave
from any terminal in that city as easily as a train or subway, allowing direct transport
of people from a city up to the Ring. And for that matter, they can also transport
up heat, something we might discuss more in the future, but this is interesting in the
context of Ecumenopolises, planet-wide cities, or their little brothers, arcologies, in that
it means space based power generation is actually better than fusion, because a fusion reactor
is still producing a lot of waste heat in the process of making electricity. Power plants generally lose over half their
energy to heat loss in making electricity, even before it hits the power grid, where
even more is lost to resistance on the lines. But a solar panel in space running electricity
right down a cable to a city, or for that matter a reactor in space doing the same,
is not producing one extra drop of heat on Earth that isn’t in the grid. So no heat is being produced due to electricity
production waste, though of course all that electricity will end as heat, either in the
wires or at your house, it’s just not leaving half or more back at the power plant. Orbital Rings a major investment, and they
also aren’t local, you have to encircle the whole planet. We do have another option, which can be done
strictly at one location, and that is to build Karman space-towers. I call them that because they reach the Karman
line, which is the generally accepted line between our atmosphere and space. Even with our material science today, we can
build such a lightweight structure using Carbon fiber materials. We might even squeak by without having to
resort to newer construction techniques too. As many of you will be aware though, here
at SFIA, we are very much in favour of using active support systems to build higher and
stronger. See our episode on space towers, and particularly
the Atlas Pillar, for how to do that. As a brief recap, we support the tower by
a series of fountains of material propelled through the tower. Our Karman towers are lightweight Atlas Pillars
poking above the atmosphere with an energy collector at the top. Now, the atmosphere does not abruptly end
as you go into space. At the Karman line, which is 100 kilometers
up, the air density is about 2.2 million times less than at the surface. That's handy for power generation, as we'll
see. Should you have trouble building quite that
high, much of the advantage remains from going shorter, but taller is better. Atlas Pillars take a lot of power to keep
them supported, how much depends on your efficiency regenerating the momentum of the support material,
in theory that could be a 100% efficient closed loop but we’re not there yet and these would
use a fair amount of power. You might ask what is the point of having
a Karman Tower that consumes some of the power it produces when you could just beam the energy
to ground instead? The answer is the energy collector is in space. Having the collector in space handily gets
around a lot of the transmission losses and other problems we discussed, like thermal
blooming, light pollution, hazards to animals, and that trade off of concentration for safety. You can skip a lot of the steps by just having
big mirrors and parabolic dishes that can point at a large array of solar collectors
fanned out on top of that tower and flood the panels with as much light as they can
handle, and those mirrors can bounce light to night side collectors just fine as well
as filter out any frequencies we can’t use well or which might degrade the panels. You stick one just north of a city so it never
shadows it and run a low resistance power line down it and now that city has a good
power supply and a popular tourism spot, since looking down from 100 kilometers up gives
a breathtaking view of everything for a thousand kilometers around. It also has virtually no footprint on the
ground, is very safe if there’s a power loss, offers ultra-high efficiency power transfer,
and provides direct access to space and a launch system. See the Space Towers episode for more on this. Another thing that having a direct connection
between space and the ground gives us is an ability to deal with the heat produced at
the converter. In space, the only way to get rid of heat
is to radiate it away, which requires giant radiators. It's also less efficient than using convection
and conduction, which are cooling options only available on the ground. If we pipe the heat back to Earth, we can
much more easily dissipate it. We can also use the heat as a source of power
in its own right, or use it as a way of desalinating water with coastal Karman Towers. Come to think of it, I like the idea of a
steampunk solution. We generate steam at the collector and use
the steam pressure as part of the active support of the tower itself. We also tap it for energy using turbine generators
and then pump the cooled fluid back up to the collector. The entire structure could be a giant steam
engine converting the steam to electricity as we go. Traditionally you do this with magnets, launching
material up a mass driver that’s slowed down and deflected back by a receiver up top,
but in theory any flow of matter works. So power satellites seems a much more attractive
option, and a potential gateway to space as launch costs drop. We’ve talked about many industries that
might fuel a snowball effect to help us get into space, science, tourism, even filmmaking,
but which of these can match energy? A market making up roughly 10% of our global
economy, and the biggest bottleneck on greater prosperity for humanity in this modern era. Get power satellite operations down to even
just near the price per kilowatt-hour of other existing sources, and it not only could power
our homes here on Earth, but our efforts to make homes off Earth. And certainly the power demands to manufacture
space habitats will be much higher than that sized for the habitat’s ongoing domestic
consumption. So, even if power generation was the first
piece of infrastructure built, additional power could be beamed to construction projects
as needed - or even as emergency power later. Indeed temporary beamed power for space projects,
such as mining and construction could be a major space industry in itself. And its applications aren’t just for Earth
and near Earth. As we’ll see next week, when we continue
our discussion of generation ships to colonize distant stars, one of the hardest parts about
traveling in deep space is getting up to the speeds necessary to do it on reasonable timelines
and to provide power to those ships, far from the Sun, but still needing to keep warm and
lit for those who dwell inside. You can beam power out quite a long way, and
you can use it to help ships get up to speed. Of course slowing down is another matter,
and one we’ll discuss next week in “Exodus Fleet”. Electricity is the life’s blood of all of
our science and industry here on Earth, and will be for those ships too, and fundamentally,
as launch costs drop and solar panels efficiency rises, power satellites can offer us a virtually
unlimited supply of electricity without the ecological problems or supply bottlenecks
of our current energy options. We had to gloss over a lot of discussion of
the basics of electromagnetism, induction, current, heat engines, and other core topics
that explain how power generation and transmission is actually done, and why some of the methods
we looked at today are better than others. If you’d like to learn more about those
topics or just brush up on them, then I’d recommend the Regents Physics Reviews. Those courses step through basic physics and
some more advanced material in a detailed and professional fashion, never skipping over
terms by assuming folks already know them, but also not dumbing things down either. Those are available over at Skillshare, an
online learning community that focuses on assembling classes on technology and has courses
on everything from basic sciences to a lot of modern software, and I’ve been using
a lot of their classes on video production, audio engineering, and animations to improve
the content here on the channel. If you want to improve your skills, unlock
new opportunities, and do the work you love, give Skillshare a try, and a Premium Membership
gives you unlimited access to classes like those. If you want to join me and the millions of
other students already learning on Skillshare, we have a special offer just for my listeners:
Get 2 months of Skillshare for free. To sign up, go to S-K-L-dot-S-H slash Isaac. Again, go to S-K-L-dot-S-H slash Isaac to
get 2 months of unlimited access to over 20,000 classes for free. Act now for this special offer, and start
learning today. As mentioned, next week we’ll be returning
to our topic of Generation Ships to look at ways to provide them the power they need to
cover huge interstellar distances in reasonable times and to keep their crew alive during
those voyages through the empty ocean of space. The week after that we’ll be teaming up
again with Joe Scott of Answers with Joe to look at some of the potential catastrophes
humanity might have to deal with before we can get out and settle the galaxy, and ways
we might avoid those, mitigate the damage, or recover afterwards. For alerts when those and other episodes come
out, make sure to subscribe to the channel, and if you enjoyed this episode, hit the like
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have a great week!
Just finished. Was great as ever.
You mentioned the high initial cost of most of the alternate launch systems and this always bothers me. You are right that a luanch loop with a build cost of 2-4 billion dollars is a fair bit but let us remember that the Endevour cost about $1.7 billion at the time of its construction.
Additionally even if the launch loop was costing $100/kg to launch, that is still 1/50th the launch cost of what the Atlas V were achieving.
Also if we consider that the ISS cost somewhere in the (very large) range of 16 to 60 billion USD just to launch, a loftrom loop would pay for itself through lowered launch costs with just one such large project.
Okay, I've done some math.
Imagine if I wanted to install such a system in 5 years. By that point, SpaceX' BFR should be operational. It is advertised to carry 150 ton for 7M USD.
Isaak mentioned that the latest solar panels mass 2kg/m² and produce 600W/m². Filling the BFS up will give us 75'000 m² worth of solar panels. Taking a bit of margin for auxiliary equipment, that nets about 70K m² solar panels, which gives us 42MW of electricity.
If we take the maximum of 100W/m² as our beam density, that means we need to reserve 420K m² on the ground for our rectennas. This is the same as a square of 650m on a side or a circle of radius 366m. Because we need to take some margin as the beam will be blotting out somewhat and to account for inaccurate aim, I would use a circle with radius 400m as the receiver.
Now, where to put this? I've been going over the map in my local neighbourhood (Belgium) to see where there is place to put this. I assume that farmers would not like to have this over their fields as some sunlight is definitely going to be blocked off, and there is not a single industrial plot that is big enough that the entire area can be covered by one owner. On top of that: most big factories already have PV panels on their roof and again, less sunlight. I'm not even gonna try putting it above residential of nature reserves.
I did find the ideal location though: a cloverleaf intersection. I found that most of them are about as big as our required circle. The entire plot is owned by the state, so acquisition should be easy, and nobody lives or works underneath it, so no one should complain too hard.
Now, cost. The launch will be 7M USD. PV solar panels go for about 10 USD/m², which gives us 750K USD. Based on existing satellites, I can't imagine the rest of the space-based equipment costing any less than 1M USD. I could not find the cost of rectennas. Altogether, I think the total cost will be something between 10M and 15M USD (8.6-12.8M EUR).
According to ELIA (the Belgian grid administrator), the price for tertiary power reserves (the type that stays always on) varies between 2.5 and 5.5 EUR/MWh. (look at the bottommost table). Given 80% efficiency on the receiver, we receive day and night 33.6MW. There are 8760 hours in a year, so that gives us 294 GWh per year. Given 3.5 EUR/MW, that gives us 1M EUR per year.
I could make a business model out of this.
Someone should get Elon Musk’s thoughts on this. He’s very bearish on Power Satellites, which I don’t really buy. Yes, he’s proven himself to be eccentric, but the only reason I can think of him being so opposed is to discourage potential competitors.
The guy who makes this blog did a lot of work optimizing several space solar power technologies, with impressive results.
http://toughsf.blogspot.com/2017/11/advanced-solar-energy-in-space-part-i.html
DidI miss the orbital corrections needed because of the thrust from beaming power down to earth? Surely they will just push themselves further and further away...
Isaaaac... did you estimate the efficiency of a microwave beaming system with a magnetron?!?
Then you said it was more efficient than a laser. News flash: to beam energy from space you need microwave " " lasers " " which are made with Gyrotrons, not Magnetrons. You should compare magnetron efficiency with a light bulb if you were trying to compare apples to apples.
Rookie mistake for a space alien.