Usually, when we read of the SPS scenario, there is a SPS and a
dedicated rectenna farm.

To me, such a scenario negates two of the advantages of GSO, namely
the wide footprint into which a SPS can beam power and the never
varying power output of the SPS.

To me these limations present three different scenarios for
increased efficiency. What are the flaws of logic or engineering
that I may be overlooking in the descriptions below?

1.) A SPS for a city is designed for below peak power rating, and
the neighboring SPS, which would be offset by perhaps a few
timezones, can supplement with additional power to meet the peak
power rating. Necessary premise: Peak power demand will ebb in the
city providing supplemental power while it is rising in the city in
need of the power. I also, realize that the microwaves coming in
from the SPS a few time zones away will be coming in at an acute
angle, and thus not be as concentrated. And this might also cause
havoc with issues like restricted airspace.

2.) A super-sized SPS, with multiple transmitter arrays, serving
multiple rectenna farms in a narrow longitudinal band. This could
provide power balancing between different utilities. Also by
extending this concept to a larger scale, could a Super-Size SPS
serve multiple utilities across the hemispherical line, thus
providing power to summer peak loads while the other hemispehre is
experiencing winter?

3.) A transfer of microwave power to and from multiple orbiting SPS
in order to take power where it is needed. This prevents designing
SPS capacity for peak power load. Thus, a SPS orbiting above a
longitude in the night, can beam a portion of its power across
space, perhaps relayed by other SPSs, to a SPS above a daylight
longitude. This SPS would receive the microwaves, phase them into
its own transmission and beam them down to the rectenna. What effect
would the microwaves have on the communication satellites KU band
signals? Such a lateral transfer of microwaves would cut a swath
through all of the uplink-downlink paths.

Thanks for your help in troubleshooting this idea.

In a message dated 9/14/02 7:27:15 PM, tango_dancer@... writes:

<< Usually, when we read of the SPS scenario, there is a SPS and a
dedicated rectenna farm. >>

Thanks for asking. My answer on the subject of SPS is easy: how dose SPS
promote the individualization of power generation? By individualization, I
mean that the generation of power is devoluted to the level of individuals
who comsume however much or less he desire. If he is a factory owner, then
the power generation will be paid more in term of fuel by the owner. If the
power requirement is low at a place like a summer cabin, then the owner pay
less. More importantly, with internet and technology and general
communications becoming more critical, the idea of dependacy upon centralized
plants become more and more risky in the light of both statist inference
(mainly monopolies) and also from terrorist actions. By individualization,
the economy and society gain more stable and secure means of power. SPS,
because of its size, scale of cost, and giant overhead of paperworks required
to deal with the states and security concerns will not be hat cheap or that
secure for a long time. Moreso, we have to talk into consideration the
problem of our own state's taking action against peaceful purpose such as the
freedom of press. Image China cutting off the power form its nationalized
SPS to deviant ISPs. Considering that powerful men hungers for growth of
control even in USA where we have shameful act of violence such as Gen.
MacArthur's crimes against unarmed and peaceful Bonus Army of 1930's, it
would be better for the free market in long run to not use SPS. It would be
better for other planets.

Carl E. Mullin
visionary artist and entrepreneur
homo asteralis
ravenart@...
www.ravenartstudio.com

"They that can give up essential liberty to obtain a little temporary safety
deserve neither liberty nor safety." -Benjamin Franklin, Historical Review of
Pennsylvania (1759)

Carl, the problem with answering technically oriented questions with
politcal mumbo jumbo is that it doesn't really address what the
poster is seeking from other group members. I asked a question of
group members because I don't know the technical limitations
involved. Perhaps others do, and they can post to further my
understanding. That kind of answer would be very helpful to me.
Besides, the problem with political orientations is that others will
always disagree with EVERYTHING you say. Like I will below.

Quite frankly, I'm very surprised you hold this view on the utility
of the SPS. It has been quite central to the economics of developing
the orbital habitats since O'Neill put it all together. Every report
I've read has acknowledged the two go almost hand-in-hand. I have a
lot of trouble seeing an economic rationale for habitats without SPS
development.

How do you foresee habitats occuring without their raison d'etre,
the SPS?

--- In spacesettlers@y..., Ravenart@a... wrote:
>
> In a message dated 9/14/02 7:27:15 PM, tango_dancer@h... writes:
>
><< Usually, when we read of the SPS scenario, there is a SPS and a
> dedicated rectenna farm. >>
>
> Thanks for asking. My answer on the subject of SPS is easy: how
dose SPS
> promote the individualization of power generation?

Who says it has to? Where did this requirement come from? What does
that even have to do with what I asked? You should start a new
thread and make your statements there, rather than hi-jacking this
one, because I fear, most responses will now be about the politics
of your position.

By individualization, I
> mean that the generation of power is devoluted to the level of
individuals
> who comsume however much or less he desire. If he is a factory
owner, then
> the power generation will be paid more in term of fuel by the
owner. If the
> power requirement is low at a place like a summer cabin, then the
owner pay
> less.

Are you saying that the more power you use the more you should pay
for it? How does that even touch on the SPS?

>More importantly, with internet and technology and general
> communications becoming more critical, the idea of dependacy upon
centralized
> plants become more and more risky in the light of both statist
inference
> (mainly monopolies) and also from terrorist actions.

What a state infers from what? Who cares what they infer? I don't. I
don't see why a state inferring something has anything to do with
centralized power plants.

If you think that centralized power plants are a bad idea, take a
look at California, where they've not been able to approve any power
plants for the last decade. Now imagine how more contentious it
would be if they had to contend with a hundred times more plants, in
a hundred more neighborhoods, in order to decentralize power
production.

By individualization,
> the economy and society gain more stable and secure means of
power.

Why? Who says so?

SPS,
> because of its size, scale of cost, and giant overhead of
paperworks required

On the contrary, there'll probably be less paperwrok involved. No
NIMBY objections, no environmental damage, no coal mining, nuclear
accident potential, gas pipelines, wind power unsightliness and
noise, river and fish damage, etc. . .

> to deal with the states and security concerns will not be hat
cheap or that
> secure for a long time.

Easier to secure something 35,786 km above the surface of the earth,
which even the Shuttle can't get to, than it is to secure one
heavily guarded centralized power plant, or a hundred unguarded
plants. With the last, you can have a bunch of guys riding around in
their Chevy throwing Molatov cocktails at those unguarded plants,
and they'll do more damage to them than a heavily armed assualt
against a nuclear plant.

Moreso, we have to talk into consideration the
> problem of our own state's taking action against peaceful purpose
such as the
> freedom of press. Image China cutting off the power form its
nationalized
> SPS to deviant ISPs.

OK, I'm imagining. And I'm trying very hard to see the relevance
that this has to the feasibility of the SPS concept. They could do
this without a SPS.

Considering that powerful men hungers for growth of
> control even in USA where we have shameful act of violence such as
Gen.
> MacArthur's crimes against unarmed and peaceful Bonus Army of
1930's, it
> would be better for the free market in long run to not use SPS.

How you reached this conclusion from the statements you wrote
escapes me!

It would be
> better for other planets.

HUH?

In a message dated 9/14/02 11:21:32 PM, tango_dancer@... writes:

<< Quite frankly, I'm very surprised you hold this view on the utility
of the SPS. It has been quite central to the economics of developing
the orbital habitats since O'Neill put it all together. Every report
I've read has acknowledged the two go almost hand-in-hand. I have a
lot of trouble seeing an economic rationale for habitats without SPS
development. >>

What I am doing here is not political but futuring like Mr. Toffler. The
thing about your interest in SPS is that you're interested in finding way to
promote space colonization and I agreed with you on the goal. But wanting
something and what the customers want are not same thing. As I see it, in
light of recent history, many people wnat more control over their own power
in order to prevent the events I has described. That's tinking in their
shoes. In meantime, just the fact that a lot of people think SPS is key to
space dosen't mean that they're right. Space have many more advantage and
it's best to consider how to get started an open-end question and a fun
challenge.

Carl E. Mullin
visionary artist and entrepreneur
homo asteralis
ravenart@...
www.ravenartstudio.com

"They that can give up essential liberty to obtain a little temporary safety
deserve neither liberty nor safety." -Benjamin Franklin, Historical Review of
Pennsylvania (1759)

victoriatangoman wrote:

>Usually, when we read of the SPS scenario, there is a SPS and a
>dedicated rectenna farm.
>
>To me, such a scenario negates two of the advantages of GSO, namely
>the wide footprint into which a SPS can beam power and the never
>varying power output of the SPS.
>
Yes, the solar array is fixed power, but the load on the power grid
depends on time of
day, year, and what's on TV.

>To me these limations present three different scenarios for
>increased efficiency. What are the flaws of logic or engineering
>that I may be overlooking in the descriptions below?
>
>1.) A SPS for a city is designed for below peak power rating, and
>the neighboring SPS, which would be offset by perhaps a few
>timezones, can supplement with additional power to meet the peak
>power rating. Necessary premise: Peak power demand will ebb in the
>city providing supplemental power while it is rising in the city in
>need of the power. I also, realize that the microwaves coming in
>from the SPS a few time zones away will be coming in at an acute
>angle, and thus not be as concentrated. And this might also cause
>havoc with issues like restricted airspace.
>
Yes, there's an inverse cosine law on the size of the rectenna on the
ground. As the angle varies from the vertical, the width of the rectenna
has to increase on the ground, to capture the same amount of energy.

The transmitter is much smaller than the receiver, and possibly cheaper.
The idea of moving power from, say, the east coast to the west coast,
would probaly work, but the rectenna would have to be bigger on each
side to compensate for the angles.

For east coast America to west coast, I make it about a 37.5 angle to
the vertical. Therefore the rectennas on the ground end up about 20%
bigger (you might like to check it out yourself, I may have screwed up.)

So all you need to do is switch off one transmitter and turn on the
other and you can supply extra power. I suppose in theory you could
point it just about anywhere, provided you were prepared to wait for the
antenna to swing across and lock in.

>2.) A super-sized SPS, with multiple transmitter arrays, serving
>multiple rectenna farms in a narrow longitudinal band. This could
>provide power balancing between different utilities. Also by
>extending this concept to a larger scale, could a Super-Size SPS
>serve multiple utilities across the hemispherical line, thus
>providing power to summer peak loads while the other hemispehre is
>experiencing winter?
>
Yeah, don't see why not; it looks very doable. The only question is
whether there is enough market south of the equator.

>3.) A transfer of microwave power to and from multiple orbiting SPS
>in order to take power where it is needed. This prevents designing
>SPS capacity for peak power load. Thus, a SPS orbiting above a
>longitude in the night, can beam a portion of its power across
>space, perhaps relayed by other SPSs, to a SPS above a daylight
>longitude.
>
I'm less certain this works so well. Well, it works, but the
transmitters are typically much smaller than the rectenna (actually
according to the equation I've seen the product of their areas is
related to the distance you're sending it.). So you'd end up building
huge rectennas to make this work, and you'd need them to be in space.
That's probably prohibitively expensive in launch costs right now,
although in the long run the costs are probably not an issue at all (in
the context of space settlement).

You could try having multiple repeaters though, that way the antennas
are much smaller... The issue with this is efficiency, as you'd lose
power with each hop, but also, for any significant distance you're
talking kilometer antennas. And the distances from one side of the
earth, the long way is 100,000 km or so if you have multiple hops.

--- In spacesettlers@y..., Ian Woollard wrote:
> victoriatangoman wrote:
>
> So all you need to do is switch off one transmitter and turn on
the
> other and you can supply extra power. I suppose in theory you
could
> point it just about anywhere, provided you were prepared to wait
for the
> antenna to swing across and lock in.

Thanks for your insight. Maybe you can help with this question too.
If the overhead SPS is beaming power to the rectenna, would there be
any issue with waveform interference if another SPS from a few time
zones away, beamed in a portion of its power, but that power is
coming in at a different angle than from overhead?

>
> >2.) A super-sized SPS, with multiple transmitter arrays, serving
> >multiple rectenna farms in a narrow longitudinal band. This could
> >provide power balancing between different utilities. Also by
> >extending this concept to a larger scale, could a Super-Size SPS
> >serve multiple utilities across the hemispherical line, thus
> >providing power to summer peak loads while the other hemispehre
is
> >experiencing winter?
> >
> Yeah, don't see why not; it looks very doable. The only question
is
> whether there is enough market south of the equator.
>
> >3.) A transfer of microwave power to and from multiple orbiting
SPS
> >in order to take power where it is needed. This prevents
designing
> >SPS capacity for peak power load. Thus, a SPS orbiting above a
> >longitude in the night, can beam a portion of its power across
> >space, perhaps relayed by other SPSs, to a SPS above a daylight
> >longitude.
> >
> I'm less certain this works so well. Well, it works, but the
> transmitters are typically much smaller than the rectenna
(actually
> according to the equation I've seen the product of their areas is
> related to the distance you're sending it.). So you'd end up
building
> huge rectennas to make this work, and you'd need them to be in
space.
> That's probably prohibitively expensive in launch costs right now,
> although in the long run the costs are probably not an issue at
all (in
> the context of space settlement).

After some analysis, I too have some doubts about how well this will
work. The over riding factor will be what is the value of
electricity that is generated in the middle of the night that you
can't sell. If that value is zero, then it might be worth trying to
sell it in another market despite the huge transmission losses.

Consider the following, radius of earth is 6,378.1 km, GEO is 35,786
km above earth surface, thus 2 SPSs with 1 relay, would entail two
legs for the transmission, each 59,629 km. This is compared to the
35,786 km from SPS to the rectenna.

Please check me on these calculations. If we designate power
received at rectenna from overhead SPS to be 100%, then power
received at the relay would be 36%. Is there further loss, in the
process of, not the distance involved of, redirecting the energy?
Now when the power is received at the destination SPS, it will be at
9%. But this is power coming from the dead of night across the
globe. Our time offset is 12 hours between the two SPSs. What is the
value of that power if there is no use for it at its designated
rectenna? I would contend it has no value. So beam it to another
rectenna whose market demands that power, even if we can only get 9%
of that power across that distance.

If we use just the line-of-sight scenario we are limited to, at
most, a 120 degree separation, with a direct line transmission of
73,030 km between the two SPSs. The received power would be 24% of
that received at the rectenna directly underneath the sending SPS.
Our time offset is 8 hours between the two SPSs. Now, we have more
power received at the final SPS, but it came from a market that is 8
hours offset from us. The question arises, does that sending market
have as much excess power to send as the one that is offset 12
hours? I don't know.

>
> You could try having multiple repeaters though, that way the
antennas
> are much smaller... The issue with this is efficiency, as you'd
lose
> power with each hop, but also, for any significant distance you're
> talking kilometer antennas. And the distances from one side of the
> earth, the long way is 100,000 km or so if you have multiple hops.

To address your concern I'll just throw an idea out without having a
clue as to its feasability. We use microwaves to beam energy from
SPS to rectenna because they travel through the atmosphere without
too much attenuation, but is this necessarily the best form in the
vacuum of space. Could the inter-SPS transfers occur as laser light?
We'd still face the dreaded inverse square loss issue, but wouldn't
laser light resolve the problem of kilometer long rectennas in space?

--- In spacesettlers@y..., "victoriatangoman"

Whoa Nelly. Hang on a sec. I have a fundamental physics question. In
my previous post I was using the inverse square law as a measure of
power lost in transmission, but is it more correct to say that it is
power lost per given area.

The inference from the last question, is that all of the power can
be captured by having a rectenna that, in the case of the 180 degree
seperation, is the inverse of 9%, namely 11.1 times larger than the
transmitter. And in the case of the 120 degree separation, the
inverse of 24%, namely 4.166 times larger than the area of the
transmitter?

If the above is correct, then my doubts about the feasability of
space power sharing may have to be reconsidered. It is my
understanding that rectennas are constructed of less expensive
components than the SPS. Maybe it could work?

Hi Tango,
Just a few comments, I hope that at least one or two will be helpful....

spacesettlers@yahoogroups.com wrote:

> 1. What's wrong with this idea?
> From: "victoriatangoman"
>
>Message: 1
> Date: Sat, 14 Sep 2002 23:26:05 -0000
> From: "victoriatangoman"
>Subject: What's wrong with this idea?
>
>Usually, when we read of the SPS scenario, there is a SPS and a
>dedicated rectenna farm.
>
>To me, such a scenario negates two of the advantages of GSO, namely
>the wide footprint into which a SPS can beam power and the never
>varying power output of the SPS.
>

I am afraid that I don't really understand your concerns here; of
course a rectenna will be required to receive the microwaves the SPS
produces - are you concerned about the initial costs of the rectennas?
Or worried about some aspect of the feasibilty of a dedicated rectenna
facility? Also is GSO Geo-Synchronous Orbit (also called GEO
Geostationary Earth Orbit)? If so, how is the unvarying output of the
SPS a problem? Is it scheduling of power delivery that you are
concerned with - what do you do with the excess power? As I said, I am
just a little confused, please be more explicit.

>To me these limations present three different scenarios for
>increased efficiency. What are the flaws of logic or engineering
>that I may be overlooking in the descriptions below?
>
>1.) A SPS for a city is designed for below peak power rating, and
>the neighboring SPS, which would be offset by perhaps a few
>timezones, can supplement with additional power to meet the peak
>power rating. Necessary premise: Peak power demand will ebb in the
>city providing supplemental power while it is rising in the city in
>need of the power. I also, realize that the microwaves coming in
>from the SPS a few time zones away will be coming in at an acute
>angle, and thus not be as concentrated. And this might also cause
>havoc with issues like restricted airspace.
>
Using one SPS to take up the slack where another fails to deliver
enough power is a very real possibility; in fact I think there is
already a power transmission satellite in orbit - reflecting microwaves
transmitted from Earth to other points on Earth. On a related note, my
own (admittedly inexpert) understanding of SPS systems is that there are
two schools of thought on beam reception: a narrow and high energy
density beam, or a wider beam with lower energy density.
The high density option allows there to be small dedicated
facilities where the energy is converted into electricity, and put onto
a distribution grid like any other powerplant. This has some advantages
- very little of your energy is wasted 'off target', the existing grids
and billing systems can be used, and the receiving facility can be made
small (and so perhaps cheaper, at least in so far as the materials
required to BUILD the rectennas) and located in a remote area if so
desired. The down sides of the high density beam have to do with its
detrimental effects on those things which are not rectennas - what about
birds, or just missing the target? What could you do to prevent the use
of the SPS as a doomsday space weapon?
The low power density option does away with many safety concerns by
making basking in the beam harmless; sure you get warm, but microwaves
are NOT ionizing radiation - and generally contain less energy than
infra-red light. The low density beam has its own problems though; the
beam has a large footprint, and so requires a large (potentially
expensive) area of rectennas; plus losses to water vapor in the
atmosphere may be higher. If the rectennas are simply built into the
roofing materials of the customer area, then perhaps they could be made
available cheaper, and eventually the whole area could be brought
on-line piecemeal for lower cost than a huge dedicated facility - but
how do you charge for the power? Or distribute it to clients with high
requirements? Also, doing this wastes some (potentially much) of the
energy in the beam by sending it off target - if you are blanketing the
entire San Francisco (for example) area with your transmission, some of
your signal is going to hit the ground.
My personal vision here sees some hope in those schemes where the
utility companies buy the excess electricity from the building owner -
they still maintain their own grid, and sell fuel generated power to
high requirement or peak time customers, but they are spared
considerable stress on the grid by the distributed delivery of power by
the SPS. Needless to say, the arrangement between building (rectenna)
owner and the SPS owner need work.

>2.) A super-sized SPS, with multiple transmitter arrays, serving
>multiple rectenna farms in a narrow longitudinal band. This could
>provide power balancing between different utilities. Also by
>extending this concept to a larger scale, could a Super-Size SPS
>serve multiple utilities across the hemispherical line, thus
>providing power to summer peak loads while the other hemispehre is
>experiencing winter?
>
Again, rectenna 'farms' (large, dedicated facilities) may or may not
exist; but I don't believe there is a technical barrier to serving
multiple areas sequentially (or even simultaneously, provided they are
few and large enough). About serving opposite hemispheres though, your
earlier point about a highly acute beam angle (with respect to the
ground) being a problem (which is true enough) may factor in; at some
point it may be easier just to put another SPS or even a constellation
of 'relay' satellites.

>3.) A transfer of microwave power to and from multiple orbiting SPS
>in order to take power where it is needed. This prevents designing
>SPS capacity for peak power load. Thus, a SPS orbiting above a
>longitude in the night, can beam a portion of its power across
>space, perhaps relayed by other SPSs, to a SPS above a daylight
>longitude. This SPS would receive the microwaves, phase them into
>its own transmission and beam them down to the rectenna. What effect
>would the microwaves have on the communication satellites KU band
>signals? Such a lateral transfer of microwaves would cut a swath
>through all of the uplink-downlink paths.
>
Relaying energy from one SPS to another should present few
difficulties; and the idea of using one SPS to cover for another is
appealing. Hmm... actually - wouldn't the transfer between SPSs use
high density beams? Wouldn't this create some of the same safety
concerns as transmitting a high density beam to Earth? Also, I am not
sure that it would be practical to design the SPS to deliver energy to
satisfy peak demand - you've got to pay for every gram of the SPS, and
the extra (up-to-peak) capacity which (by definition) cannot sell its
energy off-peak may not be worth the extra cost. On the optimistic
side, an SPS might make sufficient money without meeting peak demand...
The effects on the Ku (and other) band(s) should be minimal; while
the microwave beam from an SPS could probably fry an average
communications satellite very quickly, this shouldn't be a problem
because the SPS isn't being pointed at them. Remember -
electro-magnetic radiation doesn't interfere with itself casually; just
crossing beams won't do it.

>Thanks for your help in troubleshooting this idea.
>
You're welcome - I just hope some of it was useful.

Joe.

--- In spacesettlers@y..., "Joseph L. Brown" wrote:
> >
> I am afraid that I don't really understand your concerns here;
of
> course a rectenna will be required to receive the microwaves the
SPS
> produces - are you concerned about the initial costs of the
rectennas?
> Or worried about some aspect of the feasibilty of a dedicated
rectenna
> facility? Also is GSO Geo-Synchronous Orbit (also called GEO
> Geostationary Earth Orbit)? If so, how is the unvarying output of
the
> SPS a problem? Is it scheduling of power delivery that you are
> concerned with - what do you do with the excess power? As I said,
I am
> just a little confused, please be more explicit.

This was just a preamble and a concise statement of fact with
respect to the prevalent design architecture. This was a lead-in to
the scenarios and questions that followed.

The low density beam has its own problems though; the
> beam has a large footprint, and so requires a large (potentially
> expensive) area of rectennas; plus losses to water vapor in the
> atmosphere may be higher. If the rectennas are simply built into
the
> roofing materials of the customer area, then perhaps they could be
made
> available cheaper, and eventually the whole area could be brought
> on-line piecemeal for lower cost than a huge dedicated facility -
but
> how do you charge for the power? Or distribute it to clients with
high
> requirements? Also, doing this wastes some (potentially much) of
the
> energy in the beam by sending it off target - if you are
blanketing the
> entire San Francisco (for example) area with your transmission,
some of
> your signal is going to hit the ground.

The scenario you wrote about above is a completely new one to me. Is
this something that you've though about or did you see it written
somewhere? If so, do you recollect who wrote it and where I can rad
their analysis?

>
>> Relaying energy from one SPS to another should present few
> difficulties; and the idea of using one SPS to cover for another
is
> appealing. Hmm... actually - wouldn't the transfer between SPSs
use
> high density beams? Wouldn't this create some of the same safety
> concerns as transmitting a high density beam to Earth?

Yes, but that's an administrative and political issue, not a
technical nor economic one. I'd be happy if it could be done
economically and let the future decision makers worry about
safeguarding it.

> The effects on the Ku (and other) band(s) should be minimal;
while
> the microwave beam from an SPS could probably fry an average
> communications satellite very quickly, this shouldn't be a problem
> because the SPS isn't being pointed at them. Remember -
> electro-magnetic radiation doesn't interfere with itself casually;
just
> crossing beams won't do it.

Thanks for the clarification.

--- In spacesettlers@y..., "victoriatangoman"
> Usually, when we read of the SPS scenario, there is a SPS and a
> dedicated rectenna farm.
>
> To me, such a scenario negates two of the advantages of GSO, namely
> the wide footprint into which a SPS can beam power and the never
> varying power output of the SPS.
>
> To me these limations present three different scenarios for
> increased efficiency. What are the flaws of logic or engineering
> that I may be overlooking in the descriptions below?

Why not beam down constant power and store it on the ground until its
needed? Current pumped storage facilties can store up to 15,000MWH
and release it when necessary. (Google on "pumped storage" to see
how it works.) You could even put the whole faciltiy underground and
reuse the same water by pumping it between two reservoirs if you want
to leave a pristine Earth.

Ed Milne

--- In spacesettlers@y..., "ed_toronto1" wrote:
> --- In spacesettlers@y..., "victoriatangoman"
> wrote:
> > Usually, when we read of the SPS scenario, there is a SPS and a
> > dedicated rectenna farm.
> >
> > To me, such a scenario negates two of the advantages of GSO,
namely
> > the wide footprint into which a SPS can beam power and the never
> > varying power output of the SPS.
> >
> > To me these limations present three different scenarios for
> > increased efficiency. What are the flaws of logic or engineering
> > that I may be overlooking in the descriptions below?
>
> Why not beam down constant power and store it on the ground until
its
> needed? Current pumped storage facilties can store up to
15,000MWH
> and release it when necessary. (Google on "pumped storage" to see
> how it works.) You could even put the whole faciltiy underground
and
> reuse the same water by pumping it between two reservoirs if you
want
> to leave a pristine Earth.
>
> Ed Milne

Thanks for the information. It made for some interesting reading.
To me it looks very similar to flywheel technologies that have been
discussed for storing surplus energy on the moon during the day and
using that energy during lunar night. That particular technology
spun up very massive flywheels and then at night spun them down.

The pumped storage seems to work on the same principle.

My concerns with this strategy would be whether the additional cost
of constructing this "battery" could be justified by the elctrical
cost savings. I think from our perspective, we High Frontier types
will build the SPS, and the earth side utility can decide whether to
add additional features to their rectenna farms.

What do you think?

In a message dated 9/15/02 1:13:53 PM, ian.woollard@... writes:

<< You could try having multiple repeaters though, that way the antennas
are much smaller... The issue with this is efficiency, as you'd lose
power with each hop, but also, for any significant distance you're
talking kilometer antennas. And the distances from one side of the
earth, the long way is 100,000 km or so if you have multiple hops. >>

How about antennas on each home and building itself? No wires to the home!

Carl E. Mullin
visionary artist and entrepreneur
homo asteralis
ravenart@...
www.ravenartstudio.com

"They that can give up essential liberty to obtain a little temporary safety
deserve neither liberty nor safety." -Benjamin Franklin, Historical Review of
Pennsylvania (1759)

victoriatangoman wrote:

>Thanks for your insight. Maybe you can help with this question too.
>If the overhead SPS is beaming power to the rectenna, would there be
>any issue with waveform interference if another SPS from a few time
>zones away, beamed in a portion of its power, but that power is
>coming in at a different angle than from overhead?
>
Probably no massive issues. You'd want to keep the overall intensity
down to whatever limits are agreed, and tune them to different
frequencies to avoid standing waves. Other than that- I see no problems,
rectennas should be able to handle it fine.

>To address your concern I'll just throw an idea out without having a
>clue as to its feasability. We use microwaves to beam energy from
>SPS to rectenna because they travel through the atmosphere without
>too much attenuation, but is this necessarily the best form in the
>vacuum of space. Could the inter-SPS transfers occur as laser light?
>We'd still face the dreaded inverse square loss issue, but wouldn't
>laser light resolve the problem of kilometer long rectennas in space?
>
Actually I can tell you now, that'd work a LOT better. The lasers
currently cost about $1/watt
and they're coming down some ridiculous rate (30% a year IRC), if you
use semiconductor lasers.

The only downside about lasers is that they are a potential weapon; so
you may not be able to use them for that reason,
although you might be able to defocus the beam enough to keep people
from worrying, maybe. Hmm. If you defocus it
down to around the intensity of sunlight, you could point the lasers at
the solar panels. (Neat!)

Hello again Tango;
Thanks for the prompt responses - here's my latest round of comments
and responses; hope it helps.

>
>Message: 2
> Date: Tue, 17 Sep 2002 20:12:06 -0000
> From: "victoriatangoman"
>Subject: Re: Digest Number 547
>
>--- In spacesettlers@y..., "Joseph L. Brown" wrote:
>
>>Hi Tango,
>> Just a quick note to respond to a couple of thoughts I saw on
>>the thread.
>> Laser light may be do-able, but I doubt you would really want
>>to try it. First, exactly how large do you think an SPS will be?
>>
>
>Probably large enough to transmit 1-5 GW of electrical energy.
>
>Is a
>
>>kilometer long rectenna a signifigant added expense?
>>
>
>I'm sure it is. But a derivation of your question yields one which
>asks can the added expense of a rectenna be offset by even greater
>revenue generated by inter-orbital transmission of power to deliver
>such power from time specific low demand markets to time specific
>high demand markets?
>
I don't know about the value of electricity on markets that don't exist
yet, but lets take a stab at estimating the size of an SPS.... Lets say
Sol delivers about 1600 watts / square meter at about 1 AU (astronomical
unit, the distance of Terran orbit from Sol). Let us also posit solar
cells of about 35% efficiency, and an SPS that produces 1 gigawatt. A
gigawatt of energy is delivered by Sol across an area of ~625,000 square
meters; but this doesn't acount for our conversion efficiency of only
35%... so - 625,000 / 0.35 = ~1,785,714 square meters. But if you want
to deliver 1 gigawatt to your market, and assuming a rectenna is about
80% efficient at turning microwaves into electricity, your SPS has to be
bigger yet - about 2,232,143 square meters and that's only if it 100%
efficient at converting the electricity from the collected solar into
microwaves in the first place, and if it is always pointed directly at
Sol, and if the performance of the solar-electric cells do not degrade
over time. This works out to a square of about 1494 meters to a side,
and a 5 gigawatt facility to a square of about 3340 meters to a side.
As you have pointed out, with sufficient focussing technology the beams
between SPSs could experience little beam spreading - how big a rectenna
would we really need to recieve an incoming beam from another SPS
120,000 km away?

>I noticed that Ian
>
>>Woolards concern was with current day launch cost, but if it was
>>built on-orbit from space resources, this is less of a problem. Second,
>>its not just getting through the atmosphere that makes microwaves
>>attractive - rectennas are simple (basically just a wire mesh) and convert
>>microwaves into electricity very efficiently (about 70 to 80
>>percent - perhaps more - compared to bleeding edge solar-electric cells
>>which peak at about 35 percent). The dreaded inverse square law is a
>>problem, but it is a problem for all beams - the trick is focus.
>>
>Actually, I've been assured that the inverse square law doesn't
>apply to focused beams. So I was in error in introducing that as a
>topic of concern.
>
>If you want to use
>
>>laser tech, could I suggest masers?
>>
>OK, you suggest it but don't give me any specifics as to the pros
>and cons of the suggestion. Can you illuminate this for me? :)
>
Oops. Sorry - Masers are Microwave
Amplification by Stimulated Emission of Radiation; basically just lasers
using microwave wavelengths as opposed to the (implied) visible light
lasers of the recent "Hey! Just shine it onto the Solar Panels!" proposal.

>>Of course all this brings us back to potential weaponizing of the high energy density beams you are
>>tossing about....
>>
>True, but its design is peaceful, just like earth side nuclear
>reactors, oil refinerys, Bhopal like chemical factoris. Earth side
>facilities have safeguards, I would propose that orbital facilities
>too should have safeguards. To forever prohibit technologies very
>useful to peaceful purposes because they have the potential to be
>used for harm is a troubling issue.
>
I agree - delay and stagnation are never the answers. But if you
will propose that safeguards must be built into the space-based
facilities (just as in Terran facilities) then those safeguards must be
- at least minimally - considered; especially since so much of the
safety can easily be in-built by defocusing the beam slightly or only
focusing the beam dynamically, in response to continous feedback and
data from the recieving station. If you propose an orbital facility
with the potential to be a doomsday weapon, sources of funding are going
to run for political cover just as fast as they can. Remember Gerald Bull?

[Snip]

>OK, seeing how you were attempting to devine what my statement was
>really saying and then posited your questions on your
>interpretations, I thought my clarification about preamble would
>assure you that I wasn't concerned about the issues you raised. Now,
>it appears our discussion has veered and you indeed would like the
>questions you raised answered, so I'll be happy to further our
>dialogue.
>
>No, I'm not concerned about the cost of rectennas. In the greater
>scheme of things, they'll probably be the least expensive component
>of the SPS system.
>
Maybe - rectennas seem pretty cheap to build; but remember any
Terran facility requires maintenance. And a dedicated rectenna farm
(emphasis added to highlight the idea that perhaps the rectenna facility
could be built to be multi-purpose, or simply added to an existing
facility) has to be built on land somewhere - and land can be expensive,
as can permits to use the land. Here in the US, (God Bless America,
Land of the Lawsuit!) and California especially, getting permission to
put up a rectenna facility may meet considerable - and expensive -
resistance. Oh yeah - if the rectenna farms are considered a hazard to
people and wildlife, and have to be located in remote locations where
mishaps with improperly targetted beams will be least damaging, then add
the cost of building roads to the new location, improving the land to a
usable state, and then patching the facility into the grid - with
attendant transmission losses for sending the power through the extra
kilometers of wire.

>I'm not worried about any aspect of the rectenna system. I think
>that it is a well understood technology and even the costing of such
>a facility could be pretty much dead-on.
>
>Yes, I happen to use GSO and GEO interchangably.
>
Thanks for clearing this up.

>I see the unvarying output of a SPS as a problem of economics, not
>of design. The economic issue is one in which the unvarying power of
>the SPS is not demanded by its earthside market in an unvarying
>quantity. The earthside market will have peak demand periods and low
>demand periods. The question that I derived from this analysis was
>what to do with the surplus energy of the SPS during the low period?
>One solution was to beam it to another SPS which was serving a
>market in its peak demand period. If this process could be
>accomplished in a cost-effective way, then the SPSs in orbit would
>be used to their fullest potential.
>
Very true. And it all ties back to how efficient the transmission
of power through the grid is, and how good the energy storage technology
can be.

>> Well, of course of I've thought about it. More
>>seriously though, this isn't my area of expertise - but I have been in love
>>with the idea of SPS ever since I became aware of it about a decade or
>>so ago. As a result very little of my post represents original (my
>>own) thinking - with the possible exception of roofing with rectennas -
>>but I cannot point to a specific source for it. Even the roofing
>>rectennas aren't terribly original; they were just an extreme veiw of the
>>more mundane point that rectennas are pretty "friendly" (since one is
>>essentially just a conductive wire mesh with the wires about a
>>millimeter apart) and that you could happily live under one - even
>>the 'shading' of the area underneath would be minimal. Imagine having
>>a fine wire mesh suspended over your yard and house about five or
>>six meters up, and this mesh providing most of the power you require
>>for your home; the land under the rectenna is not 'dedicated' to just
>>rectenna farm.
>> As for my original sources, the only thing I can suggest is
>>that you do what I did - and search the web on 'Solar Power Satellite'.
>>Sorry that I can't do better than that....
>>
>Well, I too have been following the issue of SPS for over a decade,
>and I haven't run into a study that advocated receiving the
>microwaves in any fashion other that a dedicated rectenna farm. Your
>proposal to have such a facility spread over a city was a completely
>new one to me.
>
Like I said - the rectennas in the roofing material was the only
thing which even came close to being an original idea on my part, but
even so they were an extreme veiw of a very simple principle -
microwaves aren't very dangerous. If our SPS proposal is to pass the
Raving Lunatic (TM) test {ie, could a raving lunatic 'take over' the SPS
somehow and turn the beam into a doomsday weapon to murder millions and
hold entire hemispheres hostage?} then the energy density of the beam
has to be pretty low; which really isn't a problem Take, for example,
my apartment in soutern Mississippi - my breaker-box is wired for a
total of 2000 watts, and the size of the apartment is (I am guessing
here) about 100 square meters. 2000 watts / 100 meters = 20 watts per
meter, at peak load. If the SPS were to provide half my energy needs
per day, that drops to 10 watts/meter, and I buy a kilowatt from the
local grid. What is 10 watts per meter? Well, sunlight is about 900
watts/meter here (clouds, etc.) and my microwave over has 800 watts
concentrated in a cavity of about .009 meters cubed.

>My first concerns were about the constant, never ceasing exposure of
>humans to the microwaves. What health issues may derive from such
>exposure?
>
Surprisingly few. I feel a little more confident here because I did
a little graduate level research in molecular biology, and the lab I was
in handlesd a few radioisotopes. The three criteria to concern yourself
with where ratiation damage to biological systems is involved are:
Ionizing radiation, which Penetrates the body, above a critical
Threshold level. First. microwaves are not ionizing radiation - an
individual microwave contains less energy than even far infra-red
radiation, which itself has much (orders of magnitude?) less than UV
light, which has less than X-rays, etc. A quick look at a chart of the
Electro-magnetic spectrum should put your mind at ease. Secondly -
penetration is a bit of problem, but not much of one; microwaves are
absorbed by water molecules, so microwaves may penetrate a few
centimeters into the body, but most of them will expend their energy in
the outermost cm or two of the body. Lastly, the threshold level - 10
watts / meter is certainly less radiation than you get from solar
radiation every day; it certainly seems reasonable to postulate that the
human bodys' tolerance for non-ionizing EM radiation is much higher than
10 w/m.

>Secondly, unless every square meter of the city is covered by
>rectenna, then there would be energy loss on a ratio of uncovered
>area as a percentage of the beam target footprint. I have trouble
>imagining 100% coverage of a city.
>
Don't bother. The really cool thing about SPS energy is that it
almost does represent an untapped infinity of energy, once the first one
is built and paid for (and it might be surprisingly cheap if asteroidal
or other space resource materials were used) the energy is essentially
free, and the costs of building a second SPS is much lower. Sure, the
city gets a bit warmer from the off target microwaves, but consider the
drop in temperature and other beneficial environmental effects of
reducing the fossil fuel fired energy demand.

> That's why I rally wanted to read
>a review, analysis or critique of this proposal because, other than
>as a layman, I'm really in no position to evaluate the scientific or
>engineering merits/pitfalls without the guidance of professionals.
>
I can sympathize. I am a bit out of my depth in places here -
physics was my first love, but I never had the discipline or math for it.

[Snip]

>I didn't think I was side-steppoing the issue. The nature of my
>question presumed a technical and economic solution, which would
>then be up to the adminstrators and politicians to authorize, modify
>or deny. There's no use in coming to a political or administrative
>solution to a problem that is not technically nor economically
>feasible, is there?
>
Of course not, but I am only asking for technical consideration of
safety issues. If we can anticipate a problem now - and design around
it - there will be fewer political hurdles later.

>Thanks for your interest in the this thread. If you have the time,
>I'd like to know more about the merits of maser, rather than laser,
>transmission.
>
Merits? Heck, I dunno - I have a couple of friends with technical
certificates in electronics, etc. but I haven't really got a whole lot
of formal training here myself. I just can't help but think that since
microwaves seem more efficient for power transmission, and you seem to
think that the properties of laser light would be useful in the problem
at hand, that the microwave laser (Maser) would be a natural thing to
suggest. Anybody out there with hard numbers on how common masers are
in point-to-point broadcasting today? Or other applications? Any Info?
Help?

--- In spacesettlers@y..., "Joseph L. Brown" wrote:
> I don't know about the value of electricity on markets that don't
exist yet,

Just a small point: the electricity markets do exist, it's just that
the SPS production capacity doesn't exist. Right now, today, if you
could deliver electricity at the wholesale cost of 2-3 cents/kWh
you'd find buyers. In some locations, Europe, and most especially
Japan, you could probably charge even more.

Using your figures below, if you had a 5 GW SPS, then it could
deliver a revenue stream of (at $.03/kWh) $1,314,000,000 per year.
If you capitalized that revenue stream in order to determine a value
for the sale of the entire SPS, well I'm preparing a very detailed
financial analysis for a later posting, but let's just say, that you
could probably realize a lot more than typical earth powerplants,
which go for about $1/watt. But these plants also incur fuel costs
in order to meet the 2-3 cents/kWh price target. So, a worst case
price scenario would be $5 billion.

Don't ask me how much to build the damn thing. Probably much more
than you could sell it for! According to O'Neill's estimates, 5 GW
of capacity in orbit, would require a mass of 5,000,000 kg. WE're
not going to launch that!

But I digress.

but lets take a stab at estimating the size of an SPS.... Lets say
> Sol delivers about 1600 watts / square meter at about 1 AU
(astronomical
> unit, the distance of Terran orbit from Sol). Let us also posit
solar
> cells of about 35% efficiency, and an SPS that produces 1
gigawatt. A
> gigawatt of energy is delivered by Sol across an area of ~625,000
square
> meters; but this doesn't acount for our conversion efficiency of
only
> 35%... so - 625,000 / 0.35 = ~1,785,714 square meters. But if
you want
> to deliver 1 gigawatt to your market, and assuming a rectenna is
about
> 80% efficient at turning microwaves into electricity, your SPS has
to be
> bigger yet - about 2,232,143 square meters and that's only if it
100%
> efficient at converting the electricity from the collected solar
into
> microwaves in the first place, and if it is always pointed
directly at
> Sol, and if the performance of the solar-electric cells do not
degrade
> over time. This works out to a square of about 1494 meters to a
side,
> and a 5 gigawatt facility to a square of about 3340 meters to a
side.
> As you have pointed out, with sufficient focussing technology the
beams
> between SPSs could experience little beam spreading - how big a
rectenna
> would we really need to recieve an incoming beam from another SPS
> 120,000 km away?

I don't claim to have the answers, but I sure like to ask the
questions. I thought that there would be no beam spreading due to
atmospheric conditions. Further, energy density could be increased.
Further still, if laser was used, the beam could be tighter, and
perhaps more energy dense. But in the end, I can't answer your
question.

> I agree - delay and stagnation are never the answers. But if
you
> will propose that safeguards must be built into the space-based
> facilities (just as in Terran facilities) then those safeguards
must be
> - at least minimally - considered; especially since so much of the
> safety can easily be in-built by defocusing the beam slightly or
only
> focusing the beam dynamically, in response to continous feedback
and
> data from the recieving station. If you propose an orbital
facility
> with the potential to be a doomsday weapon, sources of funding are
going
> to run for political cover just as fast as they can. Remember
Gerald Bull?

Point taken. Good suggestions.
> >No, I'm not concerned about the cost of rectennas. In the greater
> >scheme of things, they'll probably be the least expensive
component
> >of the SPS system.
> >
> Maybe - rectennas seem pretty cheap to build; but remember any
> Terran facility requires maintenance. And a dedicated rectenna
farm
> (emphasis added to highlight the idea that perhaps the rectenna
facility
> could be built to be multi-purpose, or simply added to an existing
> facility) has to be built on land somewhere - and land can be
expensive,
> as can permits to use the land.

Many of the suggestions to date have focused on leasing rectenna
space from farmers, who could still do their thing under the mesh. I
can't think of a more ideal solution to this issue. Better and
cheaper than trying to lease rooftops in a city. Farms can be 100%
covered, while cities will always have streets that can't be
covered. Cows and chickens don't complain. Take a look at my
TransOrbital post for an indication of science awareness in some
sectors of society.

See my message #1999 for other interesting tidbits. Selected quotes
follow.

BILL WOULD BAN SPACE-BASED MIND CONTROL WEAPONS

Rep. Dennis Kucinich (D-OH) introduced a bill in the House of
Representatives late last year that would ban weapons in space. But
while there have been many similar legislative initiatives in the
past, Rep. Kucinich's bill is distinguished by its unusually
expansive definition of "weapons."

Among the weapons that it would proscribe the new measure
includes "psychotronic" devices that are "directed at individual
persons or targeted populations for the purpose of ... mood
management, or mind control."

No explanation for this peculiar proposal was immediately available.
But the text of "The Space Preservation Act of 2001" (H.R. 2977),
introduced on October 2, may be found here:

http://www.fas.org/sgp/congress/2001/hr2977.html
The Kucinich bill was hailed by Citizens Against Human Rights Abuse,
one of a number of organizations of people who say they are victims
of government experimentation involving electromagnetic and other
psychotronic weapons. See their web site here:

http://www.dcn.davis.ca.us/~welsh/
The bill has been referred to three House Committees.

Now imagine if you told this group that you were going to beam
microwaves down onto their heads. Wasn't there a movie a few
decades ago called scanners, where some guys with ESp would blow up
your head? I could just see the pandemonium that would ensue. No,
better to deal with the cows and chickens and wheat. Heck, we could
even tell people that they'll get roasted beef and chicken in the
supermarkets. No more having to cook their food, it's done by
microwaves from space

Here in the US, (God Bless America,
> Land of the Lawsuit!) and California especially, getting
permission to
> put up a rectenna facility may meet considerable - and expensive -
> resistance.

Expensive compared to what? The regulatory process can't be avoided.
Rectenna's will probably be a whole lot cheaper to permit than a
polluting power plant.

Oh yeah - if the rectenna farms are considered a hazard to
> people and wildlife, and have to be located in remote locations
where
> mishaps with improperly targetted beams will be least damaging,
then add
> the cost of building roads to the new location, improving the land
to a
> usable state, and then patching the facility into the grid - with
> attendant transmission losses for sending the power through the
extra
> kilometers of wire.

Yes, but all within the economics of the project, especially
considering the cost incurred in orbit. Look at what they did in
Brazil www.itaipu.gov.br (thanks for the site, Lucio) to get some
power and it made economic sense.

> Like I said - the rectennas in the roofing material was the
only
> thing which even came close to being an original idea on my part,
but
> even so they were an extreme veiw of a very simple principle -
> microwaves aren't very dangerous. If our SPS proposal is to pass
the
> Raving Lunatic (TM) test {ie, could a raving lunatic 'take over'
the SPS
> somehow and turn the beam into a doomsday weapon to murder
millions and
> hold entire hemispheres hostage?} then the energy density of the
beam
> has to be pretty low; which really isn't a problem Take, for
example,
> my apartment in soutern Mississippi - my breaker-box is wired for
a
> total of 2000 watts, and the size of the apartment is (I am
guessing
> here) about 100 square meters. 2000 watts / 100 meters = 20 watts
per
> meter, at peak load. If the SPS were to provide half my energy
needs
> per day, that drops to 10 watts/meter, and I buy a kilowatt from
the
> local grid. What is 10 watts per meter? Well, sunlight is about
900
> watts/meter here (clouds, etc.) and my microwave over has 800
watts
> concentrated in a cavity of about .009 meters cubed.

Hey, as long as we're actually beaming power down, it won't matter
to me where the rectenna is. Considering all factors, my preference
would be for farmland, but if they decide city is better, I wonn't
say a peep.

>
> >My first concerns were about the constant, never ceasing exposure
of
> >humans to the microwaves. What health issues may derive from such
> >exposure?
> >
> Surprisingly few. I feel a little more confident here because
I did
> a little graduate level research in molecular biology, and the lab
I was
> in handlesd a few radioisotopes. The three criteria to concern
yourself
> with where ratiation damage to biological systems is involved are:
> Ionizing radiation, which Penetrates the body, above a critical
> Threshold level. First. microwaves are not ionizing radiation -
an
> individual microwave contains less energy than even far infra-red
> radiation, which itself has much (orders of magnitude?) less than
UV
> light, which has less than X-rays, etc. A quick look at a chart
of the
> Electro-magnetic spectrum should put your mind at ease. Secondly -

> penetration is a bit of problem, but not much of one; microwaves
are
> absorbed by water molecules, so microwaves may penetrate a few
> centimeters into the body, but most of them will expend their
energy in
> the outermost cm or two of the body. Lastly, the threshold level -
10
> watts / meter is certainly less radiation than you get from solar
> radiation every day; it certainly seems reasonable to postulate
that the
> human bodys' tolerance for non-ionizing EM radiation is much
higher than
> 10 w/m.

Terrific. That's good information to have. Thanks.

>
> >Secondly, unless every square meter of the city is covered by
> >rectenna, then there would be energy loss on a ratio of uncovered
> >area as a percentage of the beam target footprint. I have trouble
> >imagining 100% coverage of a city.
> >
> Don't bother. The really cool thing about SPS energy is that
it
> almost does represent an untapped infinity of energy, once the
first one
> is built and paid for (and it might be surprisingly cheap if
asteroidal
> or other space resource materials were used) the energy is
essentially
> free, and the costs of building a second SPS is much lower. Sure,
the
> city gets a bit warmer from the off target microwaves, but
consider the
> drop in temperature and other beneficial environmental effects of
> reducing the fossil fuel fired energy demand.
>
> > That's why I rally wanted to read
> >a review, analysis or critique of this proposal because, other
than
> >as a layman, I'm really in no position to evaluate the scientific
or
> >engineering merits/pitfalls without the guidance of professionals.
> >
> I can sympathize. I am a bit out of my depth in places here -
> physics was my first love, but I never had the discipline or math
for it.
>
]

Electricity produced from solar on Earth is much more expensive than
electricity produced from coal, nuclear, oil, gas, hydro or even
wind. Producing electricity in space will cost more than producing
it on Earth. The principal advantage to space is that solar
insolation is about three times what it would be at any point on the
Earth's surface.

But the cost of delivering, assembling and maintaining electric
generating equipment to and in orbit much exceed the cost of the same
tasks performed on Earth by orders of magnitude. But even if
constructing this facility in orbit cost the same as on Earth (a
ridiculous assumption within the range of any foreseeable
technology), there would still be three show stoppers:

1. The losses inherent in converting electricity to some form of
beamable energy which must be at least 50% and probably higher. And
there will additional losses in the energy beamaiming and focussing
will not be 100% perfect all the time, and there will be atmospheric
losses.

2. Converting this beamed energy back into electricity is not a
trivial problem. The best technology for doing this currently would
be using a steam turbine generator at less than 40% efficiency.

3. The solar energy which is not converted into electricity will be
deposited as heat onto the power satellite. With photovoltic there
is a theoretical maximum efficiency of 37%. If there's not enough
energy in the photon to flip the electron, all the energy of the
photon is deposited as heat. If the photon carries excess energy,
that excess is deposited as heat. The best commercially available PV
cells today opearate at less than 20% efficiency, and they are very
expensive.

At least 63% of the solar energy must be deposited as heat, probably
closer to 80% with current off-the-shelf technology. In addition,
the energy lost in converting electricity to beamable energy will
also be deposited as heat. More than 80% of the energy received from
the sun will be used to heat the power satellite, and convention is
not available in a vacuum.

Using current technology I calculate the electricity delivered from a
satellite would cost about 15,000 times more than today's
conventionally supplied electricity. A $100 electric bill would rise
to $1.5 million.

When you suggest that the most sensible way to covert rectenna energy into
AC is via a steam turbine, this indicates you've not looked at SPS terribly
closely. That casts suspicions on the entire analysis.

Regards,

Mike Combs

From: bobunf [mailto:bobunf@...]

On Friday, September 20, 2002, at 11:32 PM, bobunf wrote:

> Electricity produced from solar on Earth is much more expensive than
> electricity produced from coal, nuclear, oil, gas, hydro or even
> wind.

Actually, this depends on what costs you count. For example, we spend
tens of billions every year of military control of the Persian gulf to
insure oil supplies, but these costs do show up in income tax, not when
you buy gas. Coal costs do not reflect the costs of mitigating acid
rain. Nuclear does not pay all of it's insurance costs (the government
covers it by fiat). Nuclear has received orders of magnitude more
government R&D than solar. It's not clear that solar or wind would be
cheaper on a level playing field, but it is abundantly clear that the
playing field isn't anywhere near level.

The dinosaurs were destroyed by an asteroid because they weren't
space-faring. It's almost as if Gaia then thought "Well, dinosaurs
worked pretty well, but space-faring is necessary. Maybe I'll should
try mammals this time." Humanity is now developing systems to detect and
deflect asteroids, and could build orbital space colonies to spread
beyond Earth to insure life would survive a planetary catastrophe.

Al Globus
CSC at NASA Ames Research Center
http://www.nas.nasa.gov/~globus/home.html

--- In spacesettlers@y..., "bobunf" wrote:
> Electricity produced from solar on Earth is much more expensive
than
> electricity produced from coal, nuclear, oil, gas, hydro or even
> wind. Producing electricity in space will cost more than
producing
> it on Earth. The principal advantage to space is that solar
> insolation is about three times what it would be at any point on
the
> Earth's surface.
>
> But the cost of delivering, assembling and maintaining electric
> generating equipment to and in orbit much exceed the cost of the
same
> tasks performed on Earth by orders of magnitude. But even if
> constructing this facility in orbit cost the same as on Earth (a
> ridiculous assumption within the range of any foreseeable
> technology), there would still be three show stoppers:
>
> 1. The losses inherent in converting electricity to some form of
> beamable energy which must be at least 50% and probably higher.

Why must it be? Is this new research that you're quoting? Could you
post a citation for us? The body of research that underlies the
discussion on this group has been performed by scientists, published
in peer-reviewed journals and their results have been duplicateable.
Unless you can provide us with some support for your claim that the
losses must be >50%, then I think I'll rely on the proven numbers
thus far, which show a conversion efficiency of 85% from DC to radio
frequency. In the SSI list, Charles Radley was able to provide some
data which was summerized by William Mook, that breaks the whole
process down as follows.

DC to RF 0.85. . . . . . .Conversion at the SPS
Antenna 0.98 . . . . . . .Power sent from SPS
Atmosphere 0.98. . . . . .Atmospheric attneuation
Energy Collection 0.88 . .Earth Rectenna Efficiency
RF to DC 0.89. . . . . . .Conversion at the Rectenna
Grid .97 . . . . . . . . .Convert DC to AC with Inverter

Thus, .85*.98*.98*.88*.89*.97 = 62.02% overall efficiency delivered
into the grid.

And
> there will additional losses in the energy beamaiming and
focussing
> will not be 100% perfect all the time, and there will be
atmospheric
> losses.
>
> 2. Converting this beamed energy back into electricity is not a
> trivial problem. The best technology for doing this currently
would
> be using a steam turbine generator at less than 40% efficiency.

How did you come up with the conclusion that a steam turbine
generator is the best option? You really should dig deeper into the
research on the matter of SPS and associated technologies!

>
> 3. The solar energy which is not converted into electricity will
be
> deposited as heat onto the power satellite. With photovoltic
there
> is a theoretical maximum efficiency of 37%. If there's not enough
> energy in the photon to flip the electron, all the energy of the
> photon is deposited as heat. If the photon carries excess energy,
> that excess is deposited as heat. The best commercially available
PV
> cells today opearate at less than 20% efficiency, and they are
very
> expensive.
>
> At least 63% of the solar energy must be deposited as heat,
probably
> closer to 80% with current off-the-shelf technology. In addition,
> the energy lost in converting electricity to beamable energy will
> also be deposited as heat. More than 80% of the energy received
from
> the sun will be used to heat the power satellite, and convention
is
> not available in a vacuum.
>
> Using current technology I calculate the electricity delivered
from a
> satellite would cost about 15,000 times more than today's
> conventionally supplied electricity. A $100 electric bill would
rise
> to $1.5 million.

Please show us how you calculate your 15,000X factor. I really want
to understand your argument, but all of your conclusions are
unsupported, so basically, I'm left with you presenting no argument
other than wild assertions.

If it comes down to having to compare your unsupported asertions
against those of others who have actually done published research
and show that SPS, less lift costs and space development costs, is
more than economically competitive against any earth based power
solution, then hands down I'll support those who actually present
evidence to supoort their conclusions.

And a last thought, do any of the earth based solutions have to
completely support the infrastructure they use on earth, e.g.
housing for workers, food they eat, transportation network,
vehicles, and development.

>Grid .97 . . . . . . . . .Convert DC to AC with Inverter

Do inverters exist that can handle the MegaWatt and KiloVoltage requirements
of the grid? I'm not saying they don't exist - I'm just asking.

Cheers
D

On Friday, September 20, 2002, at 11:32 PM, bobunf wrote:

> But the cost of delivering, assembling and maintaining electric
> generating equipment to and in orbit much exceed the cost of the same
> tasks performed on Earth by orders of magnitude.

Given current infrastructure, of course. SPS only works with a large
in-orbit infrastructure and extra-terrestrial resources.

> , there would still be three show stoppers:
>
> 1. The losses inherent in converting electricity to some form of
> beamable energy which must be at least 50% and probably higher.

If memory servers, a turbine system with concentrated sunlight heating a
working fluid is over 80% efficient.
>
> Using current technology I calculate the electricity delivered from a
> satellite would cost about 15,000 times more than today's
> conventionally supplied electricity. A $100 electric bill would rise
> to $1.5 million.

Current technology isn't good enough, not even close. That's why we
need a government program to develop the technology and infrastructure
(particularly launch) -- much as the government developed the internet,
subsidized development of the rail system, builds the roads, militarily
controls the Mid-East oil supply, etc. etc. etc.

The International Space Station (ISS) most important legacy may be
jump-starting space tourism. Consider: the first space tourist, Dennis
Tito, was supposed to go to the Soviet era Mir space station. Under
pressure from NASA, Russia de-orbited the Mir which resulted in Mr. Tito
going to the ISS instead. Now the Mir was old, smelly, crowded and
probably not all that nice. The ISS was brand new, shinny, much more
roomy, etc. Mr. Tito came back to Earth with glowing accounts of how
great space is. Would his experience have been as good on Mir?

Al Globus
CSC at NASA Ames Research Center
http://www.nas.nasa.gov/~globus/home.html

Hi folks,
Just a few comments on the SPS idea being bounced between Bobunf and
Tango...

>
>Message: 3
> Date: Tue, 24 Sep 2002 05:02:11 -0000
> From: "victoriatangoman"
>Subject: Re: What's wrong with this idea?
>
>--- In spacesettlers@y..., "bobunf" wrote:
>
>>Electricity produced from solar on Earth is much more expensive
>>than electricity produced from coal, nuclear, oil, gas, hydro or even
>>wind. Producing electricity in space will cost more than
>>producing it on Earth. The principal advantage to space is that solar
>>insolation is about three times what it would be at any point on
>>the Earth's surface.
>>
I don't think I agree with this; the way I have always seen the case
for space presented is that the biggest advantages have to do with
plentiful, inexpensive resources (including insolation, true) and low
transport costs. These considerable advantages must be weighed (no pun
intended) against the costs of getting out of our gravity-well.

>>But the cost of delivering, assembling and maintaining electric
>>generating equipment to and in orbit much exceed the cost of the
>>same tasks performed on Earth by orders of magnitude.
>>
Actually, the same tasks cannot be performed on Earth - unless you'd
care to take a stab at building a self supporting thin-film mirror about
3 km across. Also, if your objection here centers on the launch costs,
what effects would fabricating the equipment on-orbit from space
resources have on your projected pricing?

>> But even if
>>constructing this facility in orbit cost the same as on Earth (a
>>ridiculous assumption within the range of any foreseeable
>>technology), there would still be three show stoppers:
>>
>>1. The losses inherent in converting electricity to some form of
>>beamable energy which must be at least 50% and probably higher.
>>
>Why must it be? Is this new research that you're quoting? Could you
>post a citation for us? The body of research that underlies the
>discussion on this group has been performed by scientists, published
>in peer-reviewed journals and their results have been duplicateable.
>Unless you can provide us with some support for your claim that the
>losses must be >50%, then I think I'll rely on the proven numbers
>thus far, which show a conversion efficiency of 85% from DC to radio
>frequency. In the SSI list, Charles Radley was able to provide some
>data which was summerized by William Mook, that breaks the whole
>process down as follows.
>
>DC to RF 0.85. . . . . . .Conversion at the SPS
>Antenna 0.98 . . . . . . .Power sent from SPS
>Atmosphere 0.98. . . . . .Atmospheric attneuation
>Energy Collection 0.88 . .Earth Rectenna Efficiency
>RF to DC 0.89. . . . . . .Conversion at the Rectenna
>Grid .97 . . . . . . . . .Convert DC to AC with Inverter
>
>Thus, .85*.98*.98*.88*.89*.97 = 62.02% overall efficiency delivered
>into the grid.
>
Hi Tango - I notice you got some better numbers than I could supply,
but I also notice that you don't list a solar to DC efficiency. If I
may ask, what sort of technology is assumed, and at what efficiency? It
occurs to me that I have assumed PV, and that the 35% efficiency I gave
them in my example was very generous, but Bobunfs' idea of a steam
turbine is actually quite good - I got to looking through one of my
ancient college physics texts and the Carnot efficency of steam turbines
can be very good in space.

>>And there will additional losses in the energy beam--aiming and
>>focussing will not be 100% perfect all the time, and there will be
>>atmospheric losses.
>>
>>2. Converting this beamed energy back into electricity is not a
>>trivial problem. The best technology for doing this currently
>>would be using a steam turbine generator at less than 40% efficiency.
>>
>How did you come up with the conclusion that a steam turbine
>generator is the best option? You really should dig deeper into the
>research on the matter of SPS and associated technologies!
>
Ok, here the idea of a steam turbine is actually quite bad - a
rectenna can convert microwaves into DC much more efficiently than this.

>>3. The solar energy which is not converted into electricity will
>>be deposited as heat onto the power satellite. With photovoltic
>>there is a theoretical maximum efficiency of 37%. If there's not enough
>>energy in the photon to flip the electron, all the energy of the
>>photon is deposited as heat. If the photon carries excess energy,
>>that excess is deposited as heat. The best commercially available
>>PV cells today opearate at less than 20% efficiency, and they are
>>very expensive.
>>
>>At least 63% of the solar energy must be deposited as heat,
>>probably closer to 80% with current off-the-shelf technology. In addition,
>>the energy lost in converting electricity to beamable energy will
>>also be deposited as heat. More than 80% of the energy received
>>from the sun will be used to heat the power satellite, and convention
>>is not available in a vacuum.
>>
All good points, and quite true as far as I can tell - but don't
limit your thinking to PV. Also, as misirable as PV looks to you right
now, consider that it actually is the energy source of choice on-orbit
with todays technology; the ISS consumes somewhere near 100 Kw, and
supplys all of its needs with PV without boiling the crew.

>>Using current technology I calculate the electricity delivered
>>from a satellite would cost about 15,000 times more than today's
>>conventionally supplied electricity. A $100 electric bill would
>>rise to $1.5 million.
>>
>Please show us how you calculate your 15,000X factor. I really want
>to understand your argument, but all of your conclusions are
>unsupported, so basically, I'm left with you presenting no argument
>other than wild assertions.
>
>If it comes down to having to compare your unsupported asertions
>against those of others who have actually done published research
>and show that SPS, less lift costs and space development costs, is
>more than economically competitive against any earth based power
>solution, then hands down I'll support those who actually present
>evidence to supoort their conclusions.
>
>And a last thought, do any of the earth based solutions have to
>completely support the infrastructure they use on earth, e.g.
>housing for workers, food they eat, transportation network,
>vehicles, and development.
>
I'd like to see the calculations on the "15000 times" figure as
well. I also agree the playing feild isn't remotely level - but perhaps
we're just going to have to deal with the idea that it never will be;
the inherent differences in how the infrastructure is built, shared, and
maintained might be the one advantage that planets have. What needs to
be done is to make space competitive in spite of the seeming unfairness
of the current market.

Yeah, it's not so very hard; worst case you make kiloamps by having lots
of semiconductors in parallel at a few hundred volts, switch them to get
AC and then put the current through a step up transformer. Consider that
an existence proof only though; there's probably much better ways.

The current grid system is based on the assumption that DC-DC converters
are difficult to build. That's no longer true- modern semiconductors can
do it with relative ease and very high efficiencies.

space1d@... wrote: