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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!

<i>Applause</i>
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? <i>Applause</i>
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 …
<i>Laughter</i>

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.

<i>Soft laughter</i>
Stefan: And it looks a little bit like

this maybe.
<i>Laughter</i>

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.
<i>Applause</i>

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?

<i>Interrupted?</i>

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