# 15128 byZachary Ernst Sorenson on June 23, 2001, 6:14 p.m.
Member since 2022-08-22
I'm a little suprised that the idea of beamed power has never been fully
investigated. It seems that there are many possibilities for beamed power
ranging from sharing between grids to SPS to maybe devices that operate off
of beamed power (I wouldn't go that far though). Its just kind of funny
that so very little experimentation has gone into the subject (or at least
that's how I understand it). I was just thinking of the things one could do
with energy on such a convienient and mobile level. The possibilities could
go far beyond what could be done with SPS. Again, it is just sort of funny
this subject isn't more preavalent in common life (if it is, please tell me.
I would hate to have missed how something in my life works by that much).
# 15129 byIan Woollard on June 23, 2001, 6:54 p.m.
Member since 2022-08-22
> I'm a little suprised that the idea of beamed power has never been fully
> investigated. It seems that there are many possibilities for beamed power
> ranging from sharing between grids to SPS to maybe devices that operate off
> of beamed power (I wouldn't go that far though). Its just kind of funny
> that so very little experimentation has gone into the subject (or at least
> that's how I understand it). I was just thinking of the things one could do
> with energy on such a convienient and mobile level. The possibilities could
> go far beyond what could be done with SPS. Again, it is just sort of funny
> this subject isn't more preavalent in common life (if it is, please tell me.
> I would hate to have missed how something in my life works by that much).
technologies, in most situations e.g. wires, carrying fuel around,
batteries
Also, there are safety, and plenty of other practical issues. For
example the energy doesn't magically arrive at the destination,
it has to travel through empty space to get to the thing you want to
power. There are also concerns any time you have that much energy
floating around; things can get fried if you're not careful (e.g.
birds ;-)
> -Z. Sorenson
civilization?"
# 15130 byCharles Radley on June 24, 2001, 10:26 a.m.
Member since 2022-08-22
>
> I'm a little suprised that the idea of beamed power has never been fully
> investigated.
There are a couple of demos. One was done at Goldstone. And there is
another big one going on in Reunion Island right now. I have also
heard of tests between islands in Japan and perhaps Alaska.
If somebody can provide some links to those latter experiments it would
be
nice.
You can get links to the Reunion Island experiment from here:-
http://www.spaceref.com/news/viewpr.html?pid=5144
One of the people behind it is Guy Pignolet, here is his web page:
http://www.lindamood.com/guy.htm
Maybe there is something we can do about it.
Can we get some good cost numbers for space based microwave power
beaming systems ?
Then we could start making outline business plans.
We do not need full SPS to get started.
Maybe it is possible to come up with power beaming systems which are
cheaper than some terrestrial power transmission methods.
# 15131 byCharles Radley on June 24, 2001, 10:26 a.m.
Member since 2022-08-22
>
> The problems are that it often loses in comparison with other
> technologies, in most situations e.g. wires, carrying fuel around,
> batteries
>
Land based transmission lines are more expensive over longer distances,
GEO microwave relays are not.
How about transmission of power between islands, perhaps in an
archipeligo.
As a thought experiment, how about relaying power from New Zealand to
Fiji ?
> Also, there are safety, and plenty of other practical issues. For
Could you be more specific ?
> example the energy doesn't magically arrive at the destination,
> it has to travel through empty space to get to the thing you want to
> power. There are also concerns any time you have that much energy
> floating around; things can get fried if you're not careful (e.g.
> birds ;-)
>
The key word here is "concerns".
The issue is more physchological than real. The frequencies used are
not absorbed by water, and the only known health effects of microwave
absorption are thermal due to water absorption. And for SPS types
beams the peak intensity is less than that of natural sunlight.
Even though there is no real health issue, we still have a marketing
job.
It is similar to the problem of irradiated foods or genetic engineered
foods. They have never hurt anybody, but a lot of people are scared
stiff of them. They are still banned in some countries.
Interestingly enough, although some folks are questionining the safety
of cell phone microwaves, they are widely used and is is not affecitng
the market.
These are issues that I would really like to see more detailed
discussion on this list.
Or can somebody point me to another forum where they are being actively
discussed ?
Cheers.
CR.
# 15132 byCharles Radley on June 24, 2001, 10:55 a.m.
Member since 2022-08-22
>
> The problems are that it often loses in comparison with other
> technologies, in most situations e.g. wires, carrying fuel around,
> batteries
>
transmitting bulk energy.
Imagine convoys of trucks laden with batteries travelling from Texas to
California :-)
Let us address the issue of fuel transportaiton as a substitute for
electricity transportation:-
It actually does not solve the real-world problem.
Transporting fuel to an electricity market does no good at all if there
is no power station at the market location.
The problem of California is a case in point.
California has lots of fuel, but they are short of electricity. The
reasons are complex, and those are the reasons we should address in
order to devise a model in which microwave power beaming can compete.
The essential thing to keep in mind is that the electricity market is
not static, it is very dynamic, and changes constantly. Some of the
changes are predictable, some are not.
Examples of things which scew the electricty demand and supply
situation:
Laws and beurocracy
Regulatory Changes
Weather
Seasons
Economic growth/decline
Movement of population
Lack of investment capital - not available when needed
Time it takes to build transmission lines (including approval process)
Time it takes to build power stations (including approval process)
overlaid on all of these is....bad planning.
This results in a chaotic set of parameters which can result in major
gaps in supply versus demand which occur with very little advance
warning. Western US is a case in point.
The shortages can be local and transitory. But they can last long
enough that those positioned properly can make a good profit - even with
artificial price controls.
An interesting benefit of a GEO power transmitter (e.g. a relay) is that
it can potentially serve most of an entire hemisphere. We cannot
predict when or where a power shortage will occur. But it is quite
likely that most of the time there will be a power shortage somewhere in
the field of view.
Whenever a power shortage emerges a single GEO transmitter can
immediately reorient the beam to serve that new market.
A crucial enabling technology for this would be a portable rectenna. Or
at least a rectenna which can be assembled very quickly compared to the
time it takes to build ground transmission lines or conventional power
stations. How difficult would that be ? Any ideas ?
# 15133 byIan Woollard on June 24, 2001, 12:05 p.m.
Member since 2022-08-22
>>The problems are that it often loses in comparison with other
>>technologies, in most situations e.g. wires, carrying fuel around,
>>batteries
>>
> Do you have any numbers to support that assertion ?
you are misreading my email slightly.
Anyway, check out how much it costs to move a fuel gallons of
GAS around. It's down in the cents region. Now work out the costs
for building a microwave power transmitter/receiver.
> Land based transmission lines are more expensive over longer distances,
> GEO microwave relays are not.
Right now, for just about any scenario you can imagine, there are
cheaper ways of DISTRIBUTING power than building a GEO relay. It
doesn't matter how it scales if it's sufficiently expensive in the
first place.
> How about transmission of power between islands, perhaps in an
> archipeligo.
>
> As a thought experiment, how about relaying power from New Zealand to
> Fiji ?
Sure, go for it, if you can work out how to do it, specifically
the economics. It's certainly not impossible.
>>Also, there are safety, and plenty of other practical issues. For
> Could you be more specific ?
For most normal sitations, the antennas are 10s or hundred of meters
across. The GEO sat has a huge antenna too, but the costs are reduced
by launching from the moon. For non SPS use the power scales inversely
to area; and you can get into very legitimate concerns. For SPS use, the
antennas have to be so large that the power density is very much lower,
and can be made much safer than cell phones.
> Cheers.
>
> CR.
civilization?"
# 15134 byCharles Radley on June 24, 2001, 1:44 p.m.
Member since 2022-08-22
>
> >>The problems are that it often loses in comparison with other
> >>technologies, in most situations e.g. wires, carrying fuel around,
> >>batteries
> >>
> >>
> >
> > Do you have any numbers to support that assertion ?
>
> I was refering to the non SPS uses of this tech. I have a feeling
> you are misreading my email slightly.
>
> Anyway, check out how much it costs to move a fuel gallons of
> GAS around. It's down in the cents region. Now work out the costs
> for building a microwave power transmitter/receiver.
>
GAS fuel is useless to an electricity consumer if there is no power
station in the market, e.g. California. The electrcicity cost there
is dominated by the cost of financing power stations and power
transmission.
>
> Right now, for just about any scenario you can imagine, there are
> cheaper ways of DISTRIBUTING power than building a GEO relay. It
> doesn't matter how it scales if it's sufficiently expensive in the
> first place.
>
Again, where are the numbers ? How big is the gap ?
>
> For most normal sitations, the antennas are 10s or hundred of meters
Please define "normal" situation, I am not surwe what you are referring
to.
The demo antennas to date have been a lot smaller for short distance
experiments.
> across. The GEO sat has a huge antenna too, but the costs are reduced
GEO antennas have to be several kilometres size both and the
transmitting end and the receiving end.
> by launching from the moon. For non SPS use the power scales inversely
Luna is a good place to solar cells for an SPS, but the antennas and
microwave components weigh a lot less, are more difficult to manufacture
and could be better sent up from Earth.
> to area; and you can get into very legitimate concerns. For SPS use, the
What kind of concerns, again I am not sure what you mean.
> antennas have to be so large that the power density is very much lower,
> and can be made much safer than cell phones.
>
So we agree that the safety risk from SPS sized microwave beams is
non-existent.
Do you think we can sell this as safe to the genral public ?
Cheers,
CR.
# 15135 byMitchell E. James on June 24, 2001, 9:07 p.m.
Member since 2022-08-22
Charles Radley wrote: Imagine convoys of trucks laden with batteries travelling from Texas to
California :-)
I can imagine hydrogen fuel cell powered trucks.
Whenever a power shortage emerges a single GEO transmitter can
immediately reorient the beam to serve that new market.
A crucial enabling technology for this would be a portable rectenna. Or
at least a rectenna which can be assembled very quickly compared to the
time it takes to build ground transmission lines or conventional power
stations. How difficult would that be ? Any ideas ?
Sort of the ultimate spot market. The emphasis would have to be on portability or quick cheap assembly. This method would be used for those areas where the spot market price exceeds XXX instead of being the transmission method for base electrical generation.
Mitchell James
www.InnerTransit.org (Homebase for collaborative engineering)
# 15136 byIan Woollard on June 24, 2001, 9:34 p.m.
Member since 2022-08-22
>
>>Anyway, check out how much it costs to move a fuel gallons of
>>GAS around. It's down in the cents region. Now work out the costs
>>for building a microwave power transmitter/receiver.
>>
> GAS fuel is useless to an electricity consumer if there is no power
> station in the market, e.g. California. The electrcicity cost there
> is dominated by the cost of financing power stations and power
> transmission.
millions or so. Maybe one hundred million.
>>Right now, for just about any scenario you can imagine, there are
>>cheaper ways of DISTRIBUTING power than building a GEO relay. It
>>doesn't matter how it scales if it's sufficiently expensive in the
>>first place.
>>
> Again, where are the numbers ? How big is the gap ?
Why do I have to do all your numbers for you? Shouldn't you
do that bearing in mind you're making the claim that it makes
sense?
Oh, well, lets assume an arbitrary 1kg/m^2. Sounds in the ballpark
(that would make it less than 1mm thick, but in space that's probably
not totally out of the question.) Cost to GEO is about ~$10000 per kg.
You need atleast 1km^2, that's 1 million m^2.
Therefore one GEO transmitter would cost atleast 10 billion.
You may need two in fact, one for receive, one for transmit. That
makes 20 billion. On top of that you need to stick some equipment
on the ground to receive the microwaves and distribute it. On top
of that are the development costs.
This for about a megawatt. i.e. not very much power
>>For most normal sitations, the antennas are 10s or hundred of meters
>>
> Please define "normal" situation, I am not surwe what you are referring
> to.
Like when you need to transmit more than tens of kilometers. Try looking
at the equations sometime.
> Luna is a good place to solar cells for an SPS, but the antennas and
> microwave components weigh a lot less, are more difficult to manufacture
> and could be better sent up from Earth.
Certainly not in the long run. In the short run definitely, but then
it's expensive.
> So we agree that the safety risk from SPS sized microwave beams is
> non-existent.
No.
> Do you think we can sell this as safe to the genral public ?
Yes.
> CR.
civilization?"
# 15137 byCharles Radley on June 24, 2001, 9:55 p.m.
Member since 2022-08-22
>
> Sort of the ultimate spot market. The emphasis would have to be on
> portability or quick cheap assembly. This method would be used for
> those areas where the spot market price exceeds XXX instead of being
> the transmission method for base electrical generation.
>
It could be the foot in the door to prove the concept of space power
beaming as a commercially viable technology. After that, baseload via
SPS will be a lot easier to sell.
# 15138 byCharles Radley on June 24, 2001, 10:34 p.m.
Member since 2022-08-22
>
> Yeah? And? These power stations aren't THAT expensive. Few tens of
> millions or so. Maybe one hundred million.
>
>
> Why do I have to do all your numbers for you? Shouldn't you
> do that bearing in mind you're making the claim that it makes
> sense?
>
Some references would suffice.
Also, I am not familiar with the strip antenna technology you described,
and am asking for some source data.
> Oh, well, lets assume an arbitrary 1kg/m^2. Sounds in the ballpark
I would rather have some real numbers. Anybody got any references ?
1 kg / m^2 for something only 1mm thick sounds high to me.
What material is it made from ? Aluminum ?
> (that would make it less than 1mm thick, but in space that's probably
> not totally out of the question.) Cost to GEO is about ~$10000 per kg.
>
Sure, could it be even less than 1 mm thick ?
> You need atleast 1km^2, that's 1 million m^2.
>
> Therefore one GEO transmitter would cost atleast 10 billion.
>
Good, that is one data point.
Now, let us look at the assumptions.
What is the thickness for the antenna material ?
If it were thinner, let us say like kitchen aluminum Foil.
I just measured some, it weighs in at 0.0475 kg per square metre,
thickness is unspecified,
looks like less than 0.1 mm
1 km^2 would be 10e6 m^2 = 47,500 kg
Cost to GEO from Earth surface about $ 475 million US.
Also, does it need to be solid Aluminum ? Can we use aluminized mylar
or Kapton ? A lot lighter.
Does it need to be solid surface ? Would a mesh be OK ?
===
If we get a bit more ambitious, 50 tons of Aluminum, well, we could
recover that from surplus rocket stages and Shuttle external tanks, and
avoid launch costs. We would need a space factory to process the
Aluminium and turn it into foil. That is starting to get more
expensive in capital cost, probably not what we would do for the first
one or two.
> You may need two in fact, one for receive, one for transmit. That
Yes, we need two at least.
> makes 20 billion. On top of that you need to stick some equipment
$ 1 billion US might suffice. For the space segment.
Ground segment would be a lot less.
> on the ground to receive the microwaves and distribute it. On top
> of that are the development costs.
>
How much for development ?
Some phased array analysis.
Materials research to figure how thin a material we can use.
Then we need to research the method of deployment/construction.
Other ?
Add another billion for the ground segment and R&D, actually it would
probably be less than half that.
> This for about a megawatt. i.e. not very much power
>
The O'Neil designs were for about 1 Gigawatt per square kilometre of
antenna.
So my numbers give about $ 1 billion or two per gigawatt.
In the same ball park as terrestrial power systems.
> >>For most normal sitations, the antennas are 10s or hundred of meters
> >>
> >
> > Please define "normal" situation, I am not surwe what you are referring
> > to.
>
> Like when you need to transmit more than tens of kilometers. Try looking
> at the equations sometime.
>
I am quite familiar with the equations, no need to labor that point.
Microwave telecom systems routinely go tens of kilometres, so that is a
good experience base.
>
> > So we agree that the safety risk from SPS sized microwave beams is
> > non-existent.
>
> No.
>
Now I am really confused.
You stated that SPS beams would be less intense than cell phones, ergo
less hazardous.
Or did you mean that cell phones may yet turn out to be hazardous ?
>
> > Do you think we can sell this as safe to the genral public ?
>
> Yes.
>
Well that is hopeful at least.
Cheers,
CR.
# 15139 byIan Woollard on June 25, 2001, 11:57 a.m.
Member since 2022-08-22
>>
>>Yeah? And? These power stations aren't THAT expensive. Few tens of
>>millions or so. Maybe one hundred million.
>>
> And then some. They come in about $1 billion per gigawatt.
about right.
>>Oh, well, lets assume an arbitrary 1kg/m^2. Sounds in the ballpark
> I would rather have some real numbers. Anybody got any references ?
So would I but lets see if we're in the ballpark first.
> 1 kg / m^2 for something only 1mm thick sounds high to me.
> What material is it made from ? Aluminum ?
Ok, about 1/7 of a millimeter for aluminium.
>>(that would make it less than 1mm thick, but in space that's probably
>>not totally out of the question.) Cost to GEO is about ~$10000 per kg.
> Sure, could it be even less than 1 mm thick ?
Yes, but its limited by resistive heating I think.
>>You need atleast 1km^2, that's 1 million m^2.
>>Therefore one GEO transmitter would cost atleast 10 billion.
> Good, that is one data point.
>
> Now, let us look at the assumptions.
>
> What is the thickness for the antenna material ?
> If it were thinner, let us say like kitchen aluminum Foil.
> I just measured some, it weighs in at 0.0475 kg per square metre,
> thickness is unspecified,
> looks like less than 0.1 mm
It's not clear its upto the job though.
> 1 km^2 would be 10e6 m^2 = 47,500 kg
>
> Cost to GEO from Earth surface about $ 475 million US.
Marginal. In the ballpark though.
> Also, does it need to be solid Aluminum ? Can we use aluminized mylar
> or Kapton ? A lot lighter.
Aerials have to conduct, you make it too thin it melts.
> Does it need to be solid surface ? Would a mesh be OK ?
Yes. But the amount of conductor stays the same, and the
surface area goes down... less cooling. You're in a
vacuum, only radiative cooling.
> The O'Neil designs were for about 1 Gigawatt per square kilometre of
> antenna.
1 Gigawatt/km^2 = 1kw/m^2. Sounds like it my be too much for
aluminium foil. You'd need to do some more checking.
For an example of what happens to aluminium foil when the
power goes too high, stick an AOL CD in a microwave for a
few seconds, next to a glass of water; label side up is
best. (It WON'T wreck the microwave, provided you include the
glass of water.)
> So my numbers give about $ 1 billion or two per gigawatt.
> In the same ball park as terrestrial power systems.
>>You may need two in fact, one for receive, one for transmit. That
>Yes, we need two at least.
Not necessarily. A diffraction grating can make a directional
mirror. In theory it might be possible to point a diffraction
grating at the ground station. In practice that may not be
possible due to mechanical misalignment issues.
Still, I'm wondering whether an electronically steerable
diffraction grating could be constructed. Might be very much cheaper
as you only need one surface.
> Microwave telecom systems routinely go tens of kilometres, so that is a
> good experience base.
Not really, but their power efficiency is mostly irrelevant, only
received power and the cost of the antennas.
> You stated that SPS beams would be less intense than cell phones, ergo
> less hazardous.
>
> Or did you mean that cell phones may yet turn out to be hazardous ?
There's a risk that its hazardous. The evidence is weak though. And
it doesn't seem to get more strong with careful study, which
probably means it's junk science. Still, its very difficult to prove
something safe. The public have a very skewed perception of risk,
any NEW risk is looked at very carefully, particularly when it
doesn't directly benefit them. The public probably won't think this
benefits them, unless the electricity price ends up half the old
cost or something.
> CR.
>
civilization?"
# 15140 byMitchell James on June 25, 2001, 12:54 p.m.
Member since 2022-08-22
>>>Yeah? And? These power stations aren't THAT expensive. Few tens of
>>>millions or so. Maybe one hundred million.
>> And then some. They come in about $1 billion per gigawatt.
>Ok, I was assuming a power of around 100 megawatts, so I was
>about right.
bouncing power from earth to GEO and back. In that case the comparison
cost is the cost of the transmission line between points A and B
and the conversion equipment. Not the power plant which you are
going to have to have anyway.
Mitchell James
mejames@...
http://www.InnerTransit.net (Email distribution for multilevel organizations)
http://www.InnerTransit.org (Homebase for collaborative engineering)
# 15141 byCharles Radley on June 25, 2001, 11:34 p.m.
Member since 2022-08-22
Some excellent points, good areas for research.
> > Sure, could it be even less than 1 mm thick ?
>
> Yes, but its limited by resistive heating I think.
>
We need to understand this. Resistive disspation will increase as
resistance falls, P = E^2 / R
The losses in the system should be quite small, the RF systems is
supposed to be efficient in the high 90's %.
Most of the heat loss should be in the solid state amplifiers.
> > thickness is unspecified,
> > looks like less than 0.1 mm
>
> It's not clear its upto the job though.
>
Need more specs and data.
Is there an antenna designer in the house ?
> Aerials have to conduct, you make it too thin it melts.
>
This might not follow. For AC fields most of the electricity is
carried
on the skin of the conductor, so the core could be non-conductive.
> > Does it need to be solid surface ? Would a mesh be OK ?
>
> Yes. But the amount of conductor stays the same, and the
> surface area goes down... less cooling. You're in a
> vacuum, only radiative cooling.
>
With a mesh it would reduce the amount of conductor per unit area.
Antennas need not be solid, mesh designs are fairly common. It depends
on frequcny. Mesh antennas are less common in the higher frequency
microwave regions.
>
> 1 Gigawatt/km^2 = 1kw/m^2. Sounds like it my be too much for
> aluminium foil. You'd need to do some more checking.
>
That is about the same as sunlight, 1 Kw / square metre.
And if the efficiency is 99%, then the waste heat to be dissipated would
be
10 Watts / square meter.
> For an example of what happens to aluminium foil when the
> power goes too high, stick an AOL CD in a microwave for a
> few seconds, next to a glass of water; label side up is
> best. (It WON'T wreck the microwave, provided you include the
> glass of water.)
>
Not sure of the mechanism here or how relevant that is.
Aluminum conducts and reflects the microwaves.
This can be quite spectacular, I did something like that once by
accident.
Our antenna would be tuned. Local heating could result if the antennas
went out of tune.
I am rather speculating here, not my area of expertise.
>
> Still, I'm wondering whether an electronically steerable
> diffraction grating could be constructed. Might be very much cheaper
Interesting idea, sounds patentable if it works.
We really need some research on antenna desings for high power microwave
beaming. The studies I have seen were rather superficial in that
area.
Can anybody post some links to something more specific ?
Cheers,
CR.
# 15142 byhollroa@... on June 26, 2001, 2:33 a.m.
Member since 2022-08-22
>>
>>Yeah? And? These power stations aren't THAT expensive. Few tens of
>>millions or so. Maybe one hundred million.
>>
> And then some. They come in about $1 billion per gigawatt.
stations can produce electrical power for as little as 1.8c/Kw. When you
factor in the cost of 10's of thousands of Km of transmission lines,
substations, transformers and local distribution networks, the cost per
kilowatt can go up by a factor of 3 or more. In effect, the generation
costs become almost irrelevant.
The South Africans are trying to get around this problem by designing a
small, modular pebble bed nuclear reactor. This would provide power to
local industries and cities without the heavy transmission infrastructure
that is required by larger nukes and coal burners.
It would be great if an SPS could function in a similar way. Small towns
and cities could be fed electric power by small football pitch sized
rectena. Even if the capital cost of the power increased by a factor of 2,
you could still come out ahead, due to the elimination of transmission
infrastructure.
Tony
how to use your computer to create multiple income streams, from the
comfort of your own home.
# 15143 byCharles Radley on June 26, 2001, 9:10 a.m.
Member since 2022-08-22
>
> factor in the cost of 10's of thousands of Km of transmission lines,
> substations, transformers and local distribution networks, the cost per
> kilowatt can go up by a factor of 3 or more. In effect, the generation
> costs become almost irrelevant.
>
And if possible I need typical range of costs (max and min)
corresponding to difficulty of terrain.
> It would be great if an SPS could function in a similar way. Small towns
> and cities could be fed electric power by small football pitch sized
> rectena. Even if the capital cost of the power increased by a factor of 2,
Not gonna happen.
The minimum size for a useful rectenna is about 10 kilometres diameter.
Best sites for recetennas are farmland, where they can co-exist with
crops and livestock.
Or else lakes and deserts.
# 15144 byTom Musgrove on June 26, 2001, 9:32 a.m.
Member since 2022-08-22
see this link
nd/ch10note.htm
many potentially useful sources of info...
15. The majority of circuit miles of overhead electric line of 115 kilovolts
through 230 kilovolts in 1992 were 115-kilovolt lines. The cost assumptions
for this analysis therefore considered 115- kilovolt transmission lines for
construction and interconnection. See Edison Electric Institute, Statistical
Yearbook of the Electric Utility Industry 1992 (Washington, DC, October
1993), p. 97.
Also, they have a link
http://www.eia.doe.gov/contacts/main.html
to contact experts
here are the electric power experts
http://www.eia.doe.gov/contacts/electric.htm
and here is the guy for transmission data
Transmission Data
John Makens
287-1749
john.makens@...
Tom M.
TomM@...
# 15145 byhollroa@... on June 26, 2001, 9:37 a.m.
Member since 2022-08-22
>>>>What is a number ? I need X US dollars per megawatt per
kilometre...
corresponding to difficulty of terrain.>>>>
Let me put it this way. The coal burning power plant, where my father
works, produces power at a cost of about 2p (3UScents) per kw hour, on
average. The daytime rate, in the UK, is about 14USc/Kw-hr. Thats quite a
big increase and the only thing in-between those two values is utility
profit and transmission costs.
>>>Not gonna happen.
The minimum size for a useful rectenna is about 10 kilometres diameter.>>>
Wow!! Thats pushing 20,000 acres! Do any of the SPS concepts consider the
use of MASER's (microwave lasers) as power transmission devices? I can see
that the cost of setting up just one rectena is not likely to be trivial.
Tony
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# 15146 bycfrjlr@... on June 26, 2001, 11:51 a.m.
Member since 2022-08-22
Tom,
I wonder why the DOE site does not have a link to transmission anywhere on their site map.
Cheers,
CR.
<< see this link
http://www.eia.doe.gov/cneaf/solar.renewables/renewable.energy.annual/backgr
nd/ch10note.htm
many potentially useful sources of info...
# 15147 bycfrjlr@... on June 26, 2001, 11:56 a.m.
Member since 2022-08-22
Let me put it this way. The coal burning power plant, where my father
works, produces power at a cost of about 2p (3UScents) per kw hour, on
average. The daytime rate, in the UK, is about 14USc/Kw-hr. Thats quite a
big increase and the only thing in-between those two values is utility
profit and transmission costs.
>>>>>>>>>>>>>>>>>
>>>Not gonna happen.
The minimum size for a useful rectenna is about 10 kilometres diameter.>>>
Wow!! Thats pushing 20,000 acres! Do any of the SPS concepts consider the
use of MASER's (microwave lasers) as power transmission devices? I can see
The transmission technology used makes no difference. It is a matter of geometry and the Rayleigh criterion.
The smaller the target, the bigger the transmitter must be. The bigger the target, the smaller the transmitter needs to be.
Masers are diffraction limited in the same way as any other transmitter.
The cost of antennas in space is a lot more expensive than rectennas on the ground. So we want the space segment antenna to be as small and light as possible,
the trade off is that the ground antennas must be correspondigly larger, according to the Rayleigh equation.
>>>>>>>>>>>>>>>>>>>>>>
that the cost of setting up just one rectena is not likely to be trivial.
>>>>>>>>>>>>>>>>>>>>>>
Indeed, but it is a lot cheaper than the space segement portion.
And the cost of the competing power systems is also non-trivial.
We are talking real money here :-)
Cheers,
CR.
# 15148 byTom Musgrove on June 26, 2001, 12:57 p.m.
Member since 2022-08-22
If we had a relay system at a lower level, (say balloon suspended in the
upper atmosphere)
Couldn't we reduce the size of our rectenna(s) and transmitter(s)?
TomM@...
# 15149 byIan Woollard on June 26, 2001, 2:35 p.m.
Member since 2022-08-22
> The minimum size for a useful rectenna is about 10 kilometres diameter.
There are health concerns at the smaller sizes, but then again, I
don't expect people to stand in the beam, any more than people
grab hold of 10 kilovolt electric lines.
civilization?"
# 15150 byJustin on June 26, 2001, 3:04 p.m.
Member since 2022-08-22
>
> There are health concerns at the smaller sizes, but then again, I
> don't expect people to stand in the beam, any more than people
> grab hold of 10 kilovolt electric lines.
>
hold of. For beams from orbit, isn't there health concerns for airplanes
flying in the path of the beam? Would we just have to issue a "steer
clear" signal to all aircraft in the area somehow? And just what would
happen if an aircraft flew into one of these energy beams? Presumably the
smaller the rectenna, the stronger the beam, the nastier the consequences
of getting caught in the middle?
It's an interesting tradeoff, and we could propose both systems. One
rectenna which is very large but very safe, another which is much cheaper
but requires much more care in its use.
--Justin
# 15151 byTom Musgrove on June 26, 2001, 3:47 p.m.
Member since 2022-08-22
Here is a source of many links on wireless power transmission
They may help with the estimates, also, there may be some contacts who've
already worked some of the figures for us.
Some of the links are dead, however doing a search on the link name in
google usually finds a live link.
i.e.
http://www.spacefuture.com/archive/a_few_things_you_occasionally_wanted_to_k
now_about_wireless_power_transmission.shtml
http://www.spacefuture.com/archive/a_few_things_you_occasionally_wanted_to_k
now_about_wireless_power_transmission.shtml
Since individuals such as Seth Potter and Martin Hoffert have already done
some of the work, we may want to contact them and see if they would be
interested in helping throw together a proposal...
Tom M.
TomM@...
# 15152 byTom Musgrove on June 26, 2001, 3:54 p.m.
Member since 2022-08-22
Here is another really good link...
ound_segment.shtml
SPS is solar power satellite.
Tom M.
TomM@...
# 15153 byIan Woollard on June 26, 2001, 4:02 p.m.
Member since 2022-08-22
> But for electric lines, there's a very clear object you'd better not
> grab hold of. For beams from orbit, isn't there health concerns for
> airplanes flying in the path of the beam? Would we just have to
> issue a "steer clear" signal to all aircraft in the area somehow?
don't fly through that either.
There's plenty of other areas that are already marked like that on
maps. You wouldn't exactly put this downwind of an airport anyway.
Besides, you can surround it with towers, with lights on top.
In bad weather, there's GPS. If GPS fails, they have air
traffic control.
> And just what would
> happen if an aircraft flew into one of these energy beams?
Not a lot.
The power people get upset because the power dips.
Aeroplanes are good Faraday shields i.e a perfect shield
against microwaves. Basically, it bounces off and dissipates.
Its highly unlikely to do any major damage to the plane.
> Presumably the smaller the rectenna, the stronger the beam, the
> nastier the consequences of getting caught in the middle.
Yes, but even at 1km it's down below the power of sunlight. 10km
for a 1 gigawatt link is total overkill. 3km is below the power limits
for cell phones. And that's a 1 gigawatt link; which is a biggy.
> It's an interesting tradeoff, and we could propose both systems. One
> rectenna which is very large but very safe, another which is much
> cheaper but requires much more care in its use.
>
> --Justin
civilization?"
# 15154 byIan Woollard on June 26, 2001, 4:47 p.m.
Member since 2022-08-22
>>Aerials have to conduct, you make it too thin it melts.
> This might not follow. For AC fields most of the electricity is
> carried on the skin of the conductor, so the core could be non-conductive.
conduct the heat away but that's all.
>>1 Gigawatt/km^2 = 1kw/m^2. Sounds like it my be too much for
>>aluminium foil. You'd need to do some more checking.
> That is about the same as sunlight, 1 Kw / square metre.
Sunlight reacts with metals quite differently to microwaves.
Due to the longer wavelength, microwaves set up strong currents
in the surface- that's why they reflect the microwaves in fact;
indeed all conductors reflect microwaves for that reason.
> And if the efficiency is 99%, then the waste heat to be dissipated would
> be 10 Watts / square meter.
The problem is that the hotter it gets, the higher the resistance
becomes. The higher the resistance, the less efficient it is.
The less efficient it is, the hotter it gets.
If it reaches 700C, then the aluminium melts.
>>For an example of what happens to aluminium foil when the
>>power goes too high, stick an AOL CD in a microwave for a
>>few seconds, next to a glass of water; label side up is
>>best. (It WON'T wreck the microwave, provided you include the
>>glass of water.)
> Not sure of the mechanism here or how relevant that is.
> Aluminum conducts and reflects the microwaves.
> This can be quite spectacular, I did something like that once by
> accident.
Then you know all about it.
That's past the limit of how much power aluminium can take. There
you have 600 watts going into perhaps a square foot. The question is,
what's the smallest amount of power this effect takes?
> CR.
civilization?"
# 15155 byking_rodent@... on June 26, 2001, 5:37 p.m.
Member since 2022-08-22
> If we had a relay system at a lower level, (say balloon suspended
in the
> upper atmosphere)
> Couldn't we reduce the size of our rectenna(s) and transmitter(s)?
instance, if the baloon was at 10 miles in altitude, it's still 190
more miles just to Low Earth Orbit. The Solar Power Satellite is
going to be in Geostationary Orbit, at over 20,000 MILES!!! It would
only be a spit in the ocean.
You could put SPS's in LEO, but you'd need a fleet of them (think
Iridium) plus you loose the advantage of having sunlight 24/7.
king_rodent (putting the eek in geek)