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Herald Angel: The next talks – actually two talks – will be about, somehow about,
saving the world and saving the environment. We will have two different
ways of saving them and the first talk is "Saving the World with Space Solar Power".
It's held by Stefan and Anja and they work as space engineers in Berlin at the
Technical University. That talk will be followed by another approach which is
introduced to you by Christoph. He has a PhD in theoretical physics and his former
work was he was working with higher loop perturbation theory and supersymmetric
yang-mills theories and now he is doing airborne wind energy and that will be his
talk also. Please give the three of them a warm applause!
Applause Anja Kohfeldt: Yeah hello! As you have
heard today we are trying to save the world with introducing you to two very
different approaches of sustainable energy generation. We are three, the three of us,
and we start with Stefan. Stefan Junk: Yeah hello everyone. Thanks
for having us here! Anja: And me with our talk about space
solar power. Of course we have an outline and I will start the introduction with
showing you this very nice picture. Here you see the earth at night also known as
the black marble. It's a very interesting picture because it illuminates you or
shows you where people live or at least where people have electric energy. But
there is more information in this picture: When you start comparing these pictures
from different years, you also can see how certain regions are developing. And you
also see where suddenly it gets dark, where there has been a catastrophe or a
war or something like that. So the availability of electricity is an
indicator for human development. We still have an increasing amount of power. This
is also something we can see with that picture. But, unfortunately, currently
this power demand is largely covered by fossil resources. So yes, we need
definitely renewable sustainable energy such as solar power, wind parks, water
plants or even other solutions. The thing with terrestrial bound energy plans is
that they are bound to a certain location on earth, normally, so you either need to
decentralize them having a lot everywhere or you need a lot of the transfer
infrastructure. The other thing is – especially when thinking about a wind or a
solar power – that the availability is very varying and bound to certain
conditions. So you need to store the energy. When coming, when talking about
solar energy of course I mean we have the day/night cycle, we have the atmosphere,
so we have weather interferences. So why not go into space? There are some selling
arguments – or some really selling arguments – about space solar power: As I
already said it's sustainable, because it's sun powered. Space generally is very
very large, so we can build quite big structures without covering any space, any
area on earth. We are, it is possible to have some sunlight on our satellites up
there all around the clock. And we don't have an atmosphere, so there is no
weather. So space solar power promises to have an unlimited, constant and
predictable energy source. That's cool! Good! In addition, we don't need that much
infrastructure to distribute the power on earth. For example if you could compare
that to a huge solar theater for example in the Sahara, you would need a lot of
cables in order to get the power for example to Europe. This comes with some
problems. But also if solving the problem of power transmission, you can get energy
to very very remote locations on earth and you also can get the energy there quite
quickly. And of course the intervention in the landscape is … let's call it minimized
to a certain way. This concept of space solar power actually isn't that young.
It's there's a pattern from Peter Glaser from the 70s who already proposed a method
and apparatus for converting solar radiation to electrical power. And here
you see – you yes there's a small red spot, I'm not sure whether you can see
that – but you already see that he introduces all the components that are in
need: Of course we need the earth, we need some large area for solar, for sun
collection and we need some some antenna in order to transmit this power. Since the
70s these concepts were actually discussed all along. Since then they where
discussed. And the state of the art approach for that is called SPS Alpha
which stands for "Solar Power Satellite by means of Arbitrarily Large Phased Array".
It's the best-documented approach in that area which comes with a phase one study
financed by NASA in 2011 and 12, and they suggest a satellite structure based on the
geostationary orbit which is non moving gravity gradient stabilized. It's
collecting the sun with a very very large mirror array and a transmitter power with
a microwave beam. It looks like that for example – or it could look like that, like
a whine glass. It could look like a puddle, but there is three main components
here: So we have the Sun Reflector Mirror – this is this very very large shape –
these sun reflecting mirrors are made of actually solar sail material so extremely
lightweight although they are so big. The core piece of this installation are the so
called hex modules which you see here and they host both the solar array, the solar
panels and the wireless power transmission modules. We come to that later. And then
of course you also need the structure which holds everything together. In
addition to that you need some support structures like little robots combining,
fixing, exchanging modules and so on, but they are not further discussed yet. But
the NASA approach isn't the only one. There's also an approach from from JAXA.
This is a Japanese Space Agency. They call their approach tethered SPS. It's also a
gravity ground stabilized approach which you can see here. The idea is basically
the same but they don't have the mirrors. Their selling argument is: You know our
system is so simple, we're sure it will work somehow. But they also say that it's
not as efficient as the other approaches. In addition there are Japanese scientists
involved in the SPS Alpha study. But what I think is most interesting there are also
a lot of Japanese approaches driving forwards the wireless power transmission.
Then there's a new – quite new – approach. This is from the Chinese space agency of
CAST and they suggest a Multi-Rotary joints SPS, which you can see here. So
here in this the yellow spot over here also is the transmission antenna. But they
have their solar arrays bound in this structure which is approximately 10
kilometers wide and they adjust the position of their solar panels according
to the sun position. So this is how they try to increase the efficiency. There's
also a paper from Europe which is quite old but I'm not aware of a current work on
European ground here. If we summarize some of the core parameters of these three
documented or still discussed approaches, we come to this nice table. So we are
talking about a power transmission between 1 and 2 gigawatts. These entire structures
have a mass of about 10,000 tons – metric tons – or even more. Yes the Japanese
approach the antennas are quite big. We'll come to that later. This comes with a
certain energy density, but the total efficiency of this of these approaches are
calculated – and there's also a little bit of like a small wish list included. This
total energy is in the range of more or less 20%. I put a question mark behind
this 25% of the JAXA approach, because they even said that they won't be as
efficient as the others are. So don't take this number too serious. Maybe we must
calculate it. Yes. With that with these three approaches, I would say problem
solved, isn't it? Applause Stefan: .......concepts. But there are some major
challenges we want to point out here. At first this is the attitude in orbit
control so this station is in the geostationary orbit. There are several of
the TV satellites doing the same and it's working quite well, but these TV
satellites are about 1.8 metric tons and this station we're talking about is about
10,000 tons or 9 to 25 thousand tons, so this is a huge difference. In the
geostationary orbit it's not a big deal to rotate. It's very slow. So we just need to
point to watch the earth to hit the designated point on earth we want to
transfer the energy to. And then we have a phased array antenna, so these are these
little modules you saw before to form a beam which points exactly to the receiving
point at the earth for the energy. Another point is the the orbit control. This means
the distance from Earth and the speed the station is traveling with. This is another
point. This is already for TV satellites a little bit difficult to do. And now we
have, as I said, this one thousand metric tons station to lift up to the right
distance or to accelerate. There are several forces trying to push us out of
the exact orbit and we would lose the exact spot we want to point at. And there
is the lunar gravity, the sun gravity or solar gravity, and the flattened poles of
the earth. You know the earth is not a perfect sphere, is more imperfect, is more
like a donut. You have flattened points at the poles which disturb the gravity field.
There are solar winds and radiation pressure. Solar wind comes from the Sun.
These are particles hitting the station and pushing it out of the orbit. And there
is radiation pressure, the same that comes from deep space. This station is huge. So
you have a huge surface. This is different from the most TV satellites. So we have to
overcome this. Luckily, we have nearly unlimited energy with this station, and we
can use electrical thruster. So we don't need any fuel or propellant. Maybe a
little bit propellant to bring up to the station. Another point is the power
transmission. I think this is the most critical point. As I said, it's in a
geostationary orbit and I have an example here. I chose the MR SPS because the
numbers are so round, but most of the concepts are similar, as you saw before.
So I think about a 1GW output station. And in the picture on the right and chopped
you can see the yellow point is the standing antenna. This would be about
1.000 meter in diameter. So this is about 110 soccer fields placed in space. This
antenna is sending a microwave beam with 2.45 GHz or 5.8 GH. These frequencies are
chosen because of the low attenuation or damping in the atmosphere. We want to
transfer the most energy. And this beam hits at the receiving antenna, or in the
literature called the Rectenna. And this Rectenna is going to be about 5.000 meters
in diameter. This is 2.750 soccer fields, or about 20 times the Messe Leipzig area.
So you can imagine this is a big deal. If you think about wind parks are ugly, then
maybe you think about this area. OK, so you can read more about if you like in the
references. We have a link to this. Now, I guess you wonder about the efficiency of
this. Anja talked about it already a little bit. I have the subsystems here
including, and I think the most important part is this microwave beam. This is the
third position, and this is actually not tested. So this is just a calculated
number. These 85% or 90% to 95% is just from the studies we read. Current tests
are more in the area of 1% or a few percent. And most studies are not really
certain about the total efficiency. So we have 18% to 24% with these numbers. And
from other studies we have 13% to 25%. So this is most calculated. So now you would
wonder if wouldn't laser work for this? Or microwave beep sounds nice and you have
this nice receiving antenna. But a laser would be much smaller, I guess. So, yes,
basically you could use laser for this. And it would have a much higher energy
density. So you could hit a really smaller spot on the earth to receive the energy.
You don't have this 5 kilometers receiving antenna. But most of the research
institutes don't want to talk about lasers. I think it's just a little bit too
obvious that you have some … Laughter
Stefan: OK, so this is the most technical things, I think.
Anja: The other question is, who is gonna pay for that? And if we talk about this
extremely large structures that have to be built, and since they're also are meant to
be in the geostationary orbit where we have a certain radiation force, and we
want these components to operate for quite a long time, they are usually quite
expensive and geting all the certification for sending them up there is also very
expensive. Somehow the SPS Alpha approach has thought about that, and they are
aiming at, although the numbers are varying very much, at a material cost of $
250 per kilogram, which still is some billion dollars. And it is also a wish
list. So they are aiming for this number in their third approach where they think
that they already have the mass production, and have the certification,
and the engineering and development cost all covered up already. There's another
thing and this is the launch cost. So we are talking about a structure which is
maybe 10 thousand tonnes large, or heavy. Again, the SPS Alpha guys, they hope that
they could launch a kilo for $600 into the low-earth orbit, and continue from the
low-earth orbit into the geostationary orbit with electrical truck trusters. OK,
maybe if the BFR rocket will be available for the price of the Falcon 9, maybe. But
this also would take some time. Just a reality check right now, for the prices
the SpaceX provides on their site, the Falcon Heavy which was erected today, I
don't know whether you have heard that, so also the Falcon Heavy has not flown yet.
But SpaceX hopes that they could sell the the Falcon Heavy for 90 million dollars in
order to lift 26 tons into geostationary orbit. But that would be approximately 400
launches for such a structure as the SPS Alpha, and also would cost some tens of
billion dollars. Additioned to that, there are some other costs like the initial
orbit installation cost which comes with 11 billion dollars, and an operation of a
100 million a year. So it's quite expensive and probably this is also one of
the reasons why we don't have space solar power, yet. But still, I mean, we have
technical problems, this is just money, maybe it's also solvable, isn't it?
Stefan: Yeah, so you know about the concept, you know about the challenges,
and let's assume we can overcome these challenges, and someone is funding this
big station. I think, there are some considerations about if we want to do
this. And at first, so this beam is, you need a precision of about one 10.000ths of
a degree plus minus to hit the spot at the earth. So this is like you want to hit a
hazelnut of a 100 meters from a station flying with 3 kilometers per second. If
there's something goes wrong and the beam is hitting the wrong spot, maybe, you
know, it's not a good idea. Or if some of the antennas are not working well, the
beam is not forming right, and it's straying somewhere. So this is one point.
Let's assume everything works well, and the beam is still going through the space,
and it's going through the atmosphere. And there are some other satellites going.
Maybe, for an accident, they go through the beam. What happens then? Or, if you
can't, or by accident, and the airplane goes through the beam. So it's not even
allowed to turn on your phone on the airplane. You can imagine what happens if
this beam with 50 watts per square meter hits the airplane. I don't want to sit in
this. And then you can't avoid the animals, birds, insects, whatever go
through the beam. And maybe you have a same imagination like I have, or we have.
Soft laughter Stefan: And it looks a little bit like
this maybe. Laughter
Stefan: It sounds pretty scary, I think. Doesn't it a little bit sound like an
energy weapon? So we thought about: OK 50 watts per square meter; it's not like a
nuclear weapon, but still it could harm a lot. There is a high energy density, and
you can really fast readjust this beam. So you can point it in 1 second to the
receiving antenna, and the next second, you can just point it to some city, and a
second later, you point it just back. It's really fast to change. It's not really
defendable. I mean, you can sit in the bunker and try to hide, and maybe put your
aluminum hat on. After all it's useful. Applause
Stefan: But still, this thing is 24/7 on, so it could hit your bunker all the time.
And last year, there's a lot of interest from military institutions. So this is, I
think it's a bit scary. OK. And then you would ask: But it's legal to install this
kind of application? So basically, yeah. You see, there is already the United
Nations Outer Space Treaty. It was first signed from the Russian Federation, and
the United Kingdom, and the United States. And now it's in the United Nations
treaties and most of the other countries signed it, too. It's about all the
activities of States in the space. What does it say about this case here? And it
says, there are no nuclear weapons or other weapons of mass destruction allowed
in outer space. As always, there's a backdoor. If you install a military object
in outer space with a scientific reason, then it's allowed again. So another point
is in this treaty you must not influence the earth environment at all. There are no
real studies about this. I have a feeling it's going to influence somehow the
environment, but I'm not sure about this – I'm not a lawyer. So finally this all this
funding and this technology and the knowledge is necessary, so it's only
possible by some few states to build this. And how do you prevent that certain
leaders of states or whoever's want to build this is misuse this technology. So I
can't give you an answer on that, but I think there are some who shouldn't have
this. Yeah and you maybe you can think about this after the talk. And now we have
some take-home words for you from Anja. Anja: So yes, the concepts are existing
and we don't say that they should not be discussed and that they are entirely evil.
They it's technologically feasible – at least that that's proposed some studies –,
but I mean it's still challenging: The technology is not there yet, but the moral
questions are still open. So yes it's still pretty science-fiction and as I said
we don't say it's we should not do that at all, but at least we should think about it
and be critical with this kind or also with other new technologies. So but right
now, maybe, we should think about: Is there another solution to this energy
problem? Maybe a more realistic, maybe a less problematic one I mean?
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