1 (current)
2
# 10046 bybobunf@... on May 25, 2007, 2:52 p.m.
Member since 2021-10-03
It distresses to me to see space advocates waste time and resources
advocating and dealing with a technological approach so completely
off the wall as solar power satellites.
foreseeable future--the balance of the century if not longer. Even
under a set of more than a dozen unrealistically optimistic as-
sumptions, a solar power satellite would produce electricity at a
cost more than 17 times that of an Earth based system--realistically,
probably hundreds of times more.
This can be demonstrated by comparing a solar power satellite system
measuring ten square kilometers with an Earth based solar power
station of the same size.
Many hoped for technological improvements will benefit both space and
Earth based systems; so many of those hoped for improvements are
irrelevant in such a comparison--for instance, the effi-ciency of
solar cells. Solar cell efficiency and cost improvements will
benefit Earth based sys-tem just as much as a space based system.
Let's assume solar cell efficiency of 30%, which is beyond anything
commercially available today, but is remotely feasible for cost
effective large scale operations in the not too distant future. But,
whether solar panel efficiency is 10% or 50% makes no difference,
since efficiency will be about the same in space and on Earth.
Another example is electricity-microwave-electricity conversion
efficiencies and costs. Increases in these efficiencies and
decreases in cost improve the economics of both power satellites and
Earth based systems. In a limiting case, where energy losses
approached zero and cost was negli-gible, power could be transported
from the most optimal locations around the Earth, and the is-sues of
diurnal, weather and seasonal variability for an Earth based system
would be eliminated.
The average delivered electrical output to a facility on Earth for
the power satellite in geostationary orbit is derived as follows:
1300 watts per square meter (solar insolation at Earth's distance
from the Sun)
times *10^7 square meters of solar panels (ten square kilometers of
solar panels)
times 30% solar panel efficiency
less 1% for station keeping
times 50% efficiency in converting electricity to a power beam
less 2% for temperature control
less 2% loss in transmission through the atmosphere
less 2% loss in dispersion and aiming errors
times 70% efficiency in converting the energy beam back into
electricity
= 1300 watts*10^7*.3*.99*.5*.98*.98*.99*.7 = 128 watts *10^7.
The average delivered electrical output for the Earth based systems
is derived as follows:
According to the US National Renewable Energy Laboratory Resource
Assessment Program, the average daily total solar insolation at the
Earth's surface using a two-axis tracking concentrator is about 10 kw
hours of electricity per day per m/2 over large areas stretching from
Southern Cali-fornia through Nevada, Utah, Arizona, New Mexico and
West Texas. Vast areas of Northern Mexico have similar, or even
greater, solar insolation. This area encompasses over a million
square kilometers, and contains the Sonoran and Chihuahuan Deserts.
Much of it is at altitudes exceeding a thousand meters; and much of
it has population densities of less than one person per square
kilometer.
The average solar insolation collectable in these areas is 10 kw
hours * 365 days per year divided by the 8766 hours in a year = 416
watts/m2. The amount of electricity generated at the ten square
kilometer Earth based station
= 416*watts*10^7*.3 = 125 watts *10^7.
The costs of these systems are summarized below:
Earth based system capital costs
Materials & Construction $1,100 million ($100 per annual megawatt
hour capacity)
Land $3 million ($1,000 per acre exclusive of mineral rights)
TOTAL $1,103 million
Power satellite capital costs
Materials and construction $5,600 million (based on 1/10 the current
cost of manned missions to orbit)
Ground Station(s) $50 million
Transport of materials and equipment to orbit $20,000 million (based
on 20,000 ton total weight and cost to geostationary orbit of $1,000
per kilogramless than a 20th of current costs)
TOTAL $25,650 million
Based on current experiences with photovoltaic systems, operations
and maintenance costs for the Earth system would be about $20 million
per year; for the power satellite, about $115 million. This assumes
the equivalent of only one shuttle mission per year, but to
geostationary orbit, and at 1/5 the current cost to low Earth orbit;
and $5 million for operations at the 11 terawatt receiving station on
Earth.
Assuming a 30 year life for the Earth based system, the cost per
kilowatt hour would be the sum of the depreciation of materials and
construction costs (you don't depreciate land) = $1.1 billion divided
by 30 = $37 million, operations and maintenance = $20 million per
year and the cost of capital per year= 5% of $1,103 million = $55
million. Total = $112 million
Divided by the total electricity produced per year (8766*125*10^4 =
about 11 terawatts) = about 1 cent per kilowatt hour.
This cost is far below both the current wholesale cost of electricity
and the current cost of gener-ating electricity from solar panels.
This is because of the optimistic assumptions about solar cell
efficiency and cost, and all the other costs that occur from the bus
forward.
Assuming a 50 year life for the space based system, the cost per
kilowatt hour would be the sum of:
The annual depreciation of materials and construction costs
including transportation to orbit= $25,650 million divided by 50 =
$513 million
Operations and maintenance = average of $115 million per year, and
The cost of capital per year = 5% of $25,650 million = $1,282
million.
Total = $1910 million divided by the total electricity produced per
year (8766*128*10^4 = about 11 terawatts) = about 17 cents per
kilowatt hour.
These estimates of output and cost for the space based system contain
more than a dozen assumptions and estimates which are barely
conceivable in this century. These include:
Cost to geostationary orbit of $1,000 per kilogramless than 1/20
the current cost;
Efficiencies of large scale energy conversions exceeding the best
laboratory results to date;
Solar panels with much higher efficiency and a tenth the cost that
is now commercially avail-able;
Weight for the solar panels (including wiring, substrates,
adhesives, spars, harnesses and other structural components) of one
kilogram per square meter, a tenth of that which is now commercially
available--even with double the efficiency and ten times lower cost.
Temperature control in space handled at negligible cost;
A 50 year life for the power satellite. The limiting factor will
probably be technological change, and it will probably manifest
itself in much sooner than 50 years;
And about ten other very optimistic assumptions and estimates.
The solar power satellite is not a system worth advocating for this
century, if ever. Even under a set of more than a dozen
unrealistically optimistic assumptions, a power satellite would pro-
duce electricity at a cost 17 times higher than that of an Earth
based system --realistically, probably hundreds of times more.
# 10047 byjoe@... on May 25, 2007, 3:23 p.m.
Member since 2021-10-03
On May 25, 2007, at 14:52 UTC, bobunf wrote:
> advocating and dealing with a technological approach so completely
> off the wall as solar power satellites.
Then I would suppose that you haven't looked into them very deeply.
Those who have conclude that they're one of the best possibilities for
meeting the world's energy needs, unless of course Bussard's fusion
reactor pans out.
I noticed several incorrect assumptions in your estimates, but I recall
going over these a month or two ago, and lack the time or interest in
doing it again. If you're really so much smarter than the scientists
and engineers who have spent a lot of time thinking about this deeply,
then go submit a paper for publication and show the world their folly,
and (if you succeed) I'll applaud you for it.
I may however succumb to the urge to point out one big, glaring problem
with your analysis, which is that SSP can deliver electricity to where
it's needed, rather than to deserts far from where it's needed, as your
terrestrial solar comparison plant would do. And no, microwave power
beaming does not help with moving power from one place on the Earth to
another, since there are always annoying things like buildings and
people and continental crust in the way. (Unless, perhaps, you put a
relay station in GEO, at which point you should put the solar cells
there too and get 7X more power out of them, and free up valuable real
estate on the ground.)
Best,
- Joe
Joe Strout -- joe@...
Strout Custom Solutions
# 10048 bymikecombs@... on May 25, 2007, 3:34 p.m.
Member since 2021-10-03
From: bobunf
> advocating and dealing with a technological approach so completely
> off the wall as solar power satellites.
Your analysis is very impressive, but it proceeds from the same error as
does Bob Zubrin's: That the stated advantage of SPS over ground-based
solar is that one can get more power for a same-sized array (or I
suppose same power from a smaller-sized array). But that's not it. The
advantage of SPS is that the power is available 24/7, rain or shine,
which makes it much better suited to the generation of baseload power.
> a solar power satellite would produce electricity at a
> cost more than 17 times that of an Earth based system--realistically,
> probably hundreds of times more.
We can find experts who will agree with the lowball figure, others who
will insist on the highball estimate, and others who will disagree
entirely and say that SPS can undersell fossil fuel costs we're likely
to see in the near future.
I've tended to support SPS because in comparison to other business plans
I've seen offered up in support of space settlement, everything else
seemed less realistic, less technologically ready, or a less vital
market.
Assuming you support the settlement of space, what alternative economic
model would you promote?
Regards,
Mike Combs
# 10049 bydante_feditech@... on May 25, 2007, 5:48 p.m.
Member since 2021-10-03
> From: bobunf
> Solar power satellites are not worth advocating anytime in the
> foreseeable future
you're profoundly ignorant, too lazy to research the topic, and foolish
enough to prove both on a forum of your betters.
> This can be demonstrated by comparing a solar power satellite system
> measuring ten square kilometers with an Earth based solar power
> station of the same size.
Oh. Please. Let's do just that.
GSO = 8x more sunlight
GSO = sellers market (2x gross profit)
GSO = relative invulnerability to terrorists / industrial action
GSO = no harmful oxygen
GSO = 1/10th weight solar panels
GSO = new technology = new markets
> Many hoped for technological improvements will benefit both space and
> Earth based systems;
Some will. Some will not. The first two in the above list will make it
pretty hard for ground based solar to compete.
> But,
> whether solar panel efficiency is 10% or 50% makes no difference,
> since efficiency will be about the same in space and on Earth.
Not true. There are a variety of environmental factors that determine real
world efficiency; including light frequencies, and ambient temperature.
> Another example is electricity-microwave-electricity conversion
> efficiencies and costs. Increases in these efficiencies and
> decreases in cost improve the economics of both power satellites and
> Earth based systems.
I'm not aware of any ground based power systems that use microwave power
transmission.
> In a limiting case, where energy losses
> approached zero and cost was negli-gible,
Erm... 'negligible' is one word. Is there some reason you repeatedly do
that?
> power could be transported
> from the most optimal locations around the Earth, and the is-sues of
> diurnal, weather and seasonal variability for an Earth based system
> would be eliminated.
Not entirely. Since microwaves don't go round corners you'd still need to
transmit it either multiple times via ground stations or twice via satellite
and ground stations. And if you're going to build microwave relay satellite
that big anyway...
> The average delivered electrical output to a facility on Earth for
> the power satellite in geostationary orbit is derived as follows:
>
> 1300 watts per square meter
Or alternatively, not particularly clever uses of light weight mirrors 2600+ watts.
> times 30% solar panel efficiency
Higher efficiencies have been demonstrated, but if you wish to use this
one...
> less 1% for station keeping
Probably a gross over estimate.
> times 50% efficiency in converting electricity to a power beam
Definately a gross over estimate
> less 2% for temperature control
What have you been smoking?
> times 70% efficiency in converting the energy beam back into
> electricity
Closer to 90%
> = 1300 watts*10^7*.3*.99*.5*.98*.98*.99*.7 = 128 watts *10^7.
Even if this is true, what matters is not over all system efficacy but
life-cycle cost VS gross profit. If the latter is larger than the former
then the system can make money. If it makes significantly more money than it
costs (say twice as much) then it's worthwhile investment.
> According to the US National Renewable Energy Laboratory Resource
> Assessment Program, the average daily total solar insolation at the
> Earth's surface using a two-axis tracking concentrator is about 10 kw
> hours of electricity per day per m/2
Two axis tracking is not particularly cheap. Mechanical systems usually
require regular maintenance; which can be very expensive.
> over large areas stretching from
> Southern Cali-fornia through Nevada, Utah, Arizona, New Mexico and
> West Texas.
And the rest of us? This is a multinational list - not an american one.
> The average solar insolation collectable in these areas is 10 kw
> hours * 365 days per year divided by the 8766 hours in a year = 416
> watts/m2. The amount of electricity generated at the ten square
> kilometer Earth based station
>
> = 416*watts*10^7*.3 = 125 watts *10^7.
Not quite. A two axis tracking system usually takes up 4x the collecting
area in terms of ground space. Remember you want to avoid having your
collectors casting shadows on each other.
> The costs of these systems are summarized below:
>
> Earth based system capital costs
> Materials & Construction $1,100 million ($100 per annual megawatt
> hour capacity)
> Land $3 million ($1,000 per acre exclusive of mineral rights)
> TOTAL $1,103 million
That seems an insanely low price. You can add to that a $3B campaign to
justify 'paving over' tens of kilometers of wilderness and farmland. Plus
another few billion for the construction cost of the roadway to get to your
building site. These cost will repeat every time you build a new power
station. You can't easily spread it out over several.
> Power satellite capital costs
> Materials and construction $5,600 million (based on 1/10 the current
> cost of manned missions to orbit)
> Ground Station(s) $50 million
> Transport of materials and equipment to orbit $20,000 million (based
> on 20,000 ton total weight and cost to geostationary orbit of $1,000
> per kilogramless than a 20th of current costs)
> TOTAL $25,650 million
My figures come to $70B per 10GW SSPS, plus $50B for one-time start up
costs, and $20B for overhaul every thirty years to make them good as new. My
figures also assume the SSPS owners are not stupid and sell their
electricity where they can make the most money, that electricity costs will
not go down significantly, and hence the owners make a gross profit of
$140B over each 30 year lifetime. Given that once they are in orbit,
overhaul will only cost about $20B there is also significant potential to
cut electricity costs.
> Based on current experiences with photovoltaic systems, operations
> and maintenance costs for the Earth system would be about $20 million
> per year; for the power satellite, about $115 million.
> This assumes the equivalent of only one shuttle mission per year
Only a complete loony would suggest using the space shuttle. Countless
industry studies have shown that with a large market for launch services
(and a chain of SSPSs would certainly count) would enable a price of
$200-$1000/kg. It's a mixture of rocket science, the square-cube rule, and
common sense.
> Assuming a 30 year life for the Earth based system, the cost per
> kilowatt hour would be the sum of the depreciation of materials
BS snipped.
The cost per kilowatt would be whatever the damn market would bare. That's
what 'seller's market' means. Of course in GSO you can sell to any nation in
the western hemisphere. In a ground station you're stuck with your own
nation (or possibly a very close by neighbour - if you government lets you)
and it's a buyers market.
> [SSPS] Total = about 17 cents per kilowatt hour.
My figures...
$70B construction.
10GW * 30 years = 2.63*10^12 Kwh
Total = 3 cents per kilowatt
Second lifetime:
$20B overhaul
10GW * 30 years = 2.63*10^12 Kwh
Total = 0.86 cents per Kwh
The single problem is that SSPSs are large scale engineering projects, and
only work when run that way. Only on the small scale (under ~1GW) can they
not compete with ground systems
> These estimates of output and cost for the space based system contain
> more than a dozen assumptions and estimates which are barely
> conceivable in this century.
Translation: I'm too stupid to think of solutions, nor look up the solutions
that have existed for the past forty years.
> Cost to geostationary orbit of $1,000 per kilogramless than 1/20
> the current cost;
A cost of $500/kg to LEO is achievable. A nuclear or solar powered tug would
certainly be capable of moving goods to GSO without doubling costs.
> Weight for the solar panels (including wiring, substrates,
> adhesives, spars, harnesses and other structural components) of one
> kilogram per square meter, a tenth of that which is now commercially
> available--even with double the efficiency and ten times lower cost.
'Commercially available panels today' are designed to operate at ground
level, in the wind and rain, after being covered in the weight of eight
inches of snow, and having the family dog piddle on them. Oh yes - and they
need to support their own weight.
# 10050 byjoe@... on May 25, 2007, 5:58 p.m.
Member since 2021-10-03
Relevant to this thread, there was just a workshop on this very topic
at MIT: http://web.mit.edu/space_solar_power/
and the economic feasibility of SSP in depth.
The "Resources" and "Participants" pages linked above will both be of
interest, though for different reasons.
Best,
- Joe
Joe Strout -- joe@...
Strout Custom Solutions
# 10051 bymikecombs@... on May 25, 2007, 7:43 p.m.
Member since 2021-10-03
From: ANTIcarrot [dante_feditech@...]
>
> > In a limiting case, where energy losses
> > approached zero and cost was negli-gible,
>
> Erm... 'negligible' is one word. Is there some reason you repeatedly
do
> that?
I'd mentioned that some of the arguments reminded me of Zubrin's
analysis. The above, plus the fact that one paragraph is repeated as
both the second and last one makes me wonder if this was cut-and-pasted
from somewhere.
bobunf, I'm really not trying to jump down your throat or accuse you of
any kind of impropriety, but is this your analysis, or did you cut and
paste from another reference? I only ask because I'm curious to know if
we're debating you, or essentially debating Zubrin by proxy.
> > power could be transported
> > from the most optimal locations around the Earth, and the is-sues of
> > diurnal, weather and seasonal variability for an Earth based system
> > would be eliminated.
>
> Not entirely. Since microwaves don't go round corners you'd still need
to
> transmit it either multiple times via ground stations or twice via
satellite
> and ground stations. And if you're going to build microwave relay
satellite
> that big anyway...
David Criswell (LSP advocate) likes to make the point that an orbital
microwave reflector would mass significantly less than a same-area SPS.
But the point remains that neither LSP nor the above proposal saves us
the complications of having to emplace large structures in orbit.
> > less 1% for station keeping
>
> Probably a gross over estimate.
That figure didn't raise my eyebrow the first time I saw it. But on
further reflection, I'm recalling that somebody said the average SPS
would have 10 times the power output of a nuclear reactor. So what the
above implies is that it might take 1/10 the output of a nuclear reactor
just to maintain orientation of this satellite. Maintaining orbital
altitude wouldn't even enter into it since there is no significant drag
at GEO altitude.
> > less 2% for temperature control
>
> What have you been smoking?
I've never read anything about SPS to imply that anything beyond passive
cooling would be necessary.
> > This assumes the equivalent of only one shuttle mission per year
>
> Only a complete loony would suggest using the space shuttle.
And that stood out to me too. Even before the Shuttle flew, in the era
when its capabilities were assumed to be much greater than they turned
out to be in reality, SPS advocates assumed yet more advanced space
transportation systems with capabilities far beyond even the
hypothetical Shuttle ones.
Regards,
Mike Combs
# 10052 bybobunf@... on May 26, 2007, 12:03 a.m.
Member since 2021-10-03
--- In spacesettlers@yahoogroups.com, "Combs, Mike"
"The advantage of SPS is that the power is available 24/7, rain or
shine, which makes it much better suited to the generation of
baseload power."
advantage, although the power output would not always be the same.
Power output would be about 6% higher at the height of winter in the
Northern Hemisphere, than at the height of summer, because of the
eccentricity of the Earth's orbit. The Earth is closer to the sun in
the Northern Hemisphere winter and further from the sun in summer.
Unfortunately, this is exactly the opposite of demand for elec-
tricity, which increases about 20% over the average at the height of
summer, and decreases about 20% over the winter period.
If the excess electricity had to be stored for the six months during
the year when production was above demand, the required storage would
be about 23%*.5*11 terawatt hours = about 1,265 million kw hours or
about 42 days of production. Such storage would also eliminate any
difficulties of eclipses by the Moon and Earth. As can be seen,
there are obvious disadvantages to a system that produces electricity
varying in the opposite direction of demand.
The Earth based system would have to contend with diurnal, seasonal
and weather variations in solar insolation. These variations track
the demand for electricity, albeit imperfectly. Demand is lower in
winter, at night, and on cloudy days. Seasonal variation in solar
insolation is much largerdiffering by a factor of more than two and
extending over six month periods, but partially offset because demand
for electricity is about 50% higher in summer than in winter. There
are obvious advantages to a power source that tracks demand, even if
imperfectly.
These variations in production could be somewhat ameliorated by
placing generating stations in multiple locations in the very
desirable and accessible areas described in my previous post. These
areas span more than 30 of longitude and 20 of latitude in the
American Southwest and Northern Mexico. This could have the effect
of substantially reducing variation due to weather, and reducing
variation due to the diurnal cycle by as much as 10%.
But, even with these ameliorative measures and lower demand, because
of the large seasonal variation in solar insolation, it would still
be necessary to store over 9x10^8 kw hours of electricity, or about
30 days of production.
A more likely approach in the actual environment of electricity
generation and demand would be the use of a nuclear or coal base
generating capacity with the solar adding to that capacity and more
closely tracking the demand. For instance, if demand were 100 units
in winter and 150 in summer, the base would provide 50 units all the
time, and Earth based solar 50 units in winter and 100 in summer;
yielding exactly what's demanded at no added cost.
Such a delightful situation would obviously not be possible with a
space based system that generated electricity in cycles contrary to
demand.
Besides, base power at a cost 17 times what we get it for with 19th
century technology is hardly sometime to advocate.
Bob
# 10053 bydante_feditech@... on May 26, 2007, 1:26 a.m.
Member since 2021-10-03
> From: bobunf
> The Earth is closer to the sun in
> the Northern Hemisphere winter and further from the sun in summer.
> Unfortunately, this is exactly the opposite of demand for elec-
> tricity, which increases about 20% over the average at the height of
> summer, and decreases about 20% over the winter period.
additional load on the grid due to plug-in hybrids or pure electric cars.
> If the excess electricity had to be stored for the six months during
> the year when production was above demand,
It would not need to be stored; nor would there be any purpose in such an
effort. If you have excess power, you simply allow some energy to go to
waste, or sell it in anotehr market. A SSPS can stop beaming power down to
the US and target a recieving station in Europe or Africa in a matter of
hours (pesimistically) allowing you to maintain high energy throughput and
hence monetary income. Alternatively, you have the SSPSs supplying 90% of
the national load, and a few other more conventional power stations to take
care of seasonal and hourly variations.
> Such storage would also eliminate any
> difficulties of eclipses by the Moon and Earth.
I don't believe that woudl ever be a problem. The US could easily consume
the output of 50 10GW SSPSs. Only one of them would be obscured by the moon
or earth for any amount of time. Since succh eclipses woudl be easily
predictable and (I'm almost certian) only partial they woudl be easy to
compensate for.
> The Earth based system would have to contend with diurnal, seasonal
> and weather variations in solar insolation.
And a hell load of other problems. Including atmospheric, water, and
wildlife based corrosion.
> Demand is lower in
> winter, at night, and on cloudy days.
You keep forgetting to say 'only in california'. You're forgetting the road
rule. If electriccity/cars are cheap enough, usage will expand to fill any
capacity.
Though this does raise an additional point. How well would ground stations
cope with extreme weather conditions? Snow brings down power cables and
hurricanes push them over. since the ground stations is effectively going to
look like *lots* of electricity pylons...
> But, even with these ameliorative measures and lower demand, because
> of the large seasonal variation in solar insolation, it would still
> be necessary to store over 9x10^8 kw hours of electricity, or about
> 30 days of production.
This sems to be based on the complete-idiots guide to home power generation.
It tells you that after you install solar panels on your roof you absolutely
must buy hugely expensive batteries, several transformers and a horribly
complex computer system to run it. By contrast the sane-person's guide will
tell you just connect the panels directly to your mains circuit via a
transformer. There's always something using power in your home, usually the
fridge, and this way every time you generate $0.01 cent of solar power (and
you'll likely never generate more than a trickle) that's simply another
$0.01 you don't get billed for by your power company. The second system can
cost half as much and is much more effecient in putting power into the
plugs; hence pays for itself faster.
> Besides, base power at a cost 17 times what we get it for with 19th
> century technology is hardly sometime to advocate.
This figure isn't going to magically become true no matter how many times
you say it.
John
# 10054 bybmaillists@... on May 26, 2007, 1:56 a.m.
Member since 2021-10-03
You can sell anywhere in the world, no need to stick to the Western
Hemisphere.
poor sucker that has to clean the dust off them so that they retain full
efficiency.
Remember ground based solar is based on 5 peak hours (7 if you are lucky
and in an optimal area) of output a day. In space you get 24 hours a day
of it.
There is also no absolute need to use solar cells.
B
ANTIcarrot wrote:
# 10055 bycsmyth@... on May 26, 2007, 3:09 a.m.
Member since 2021-10-03
--- In spacesettlers@yahoogroups.com, joe@... wrote:
>
> Relevant to this thread, there was just a workshop on this very topic
> at MIT: http://web.mit.edu/space_solar_power/
>
> Best,
> - Joe
>
> --
> Joe Strout -- joe@...
> Strout Custom Solutions
>
Hi Joe,
conclusions of the workshop will be published?
Chris
# 10056 bybobunf@... on May 26, 2007, 3:09 a.m.
Member since 2021-10-03
--- In spacesettlers@yahoogroups.com, "ANTIcarrot"
wrote:
have you been smoking?" "you're profoundly ignorant, too lazy to
research the topic, and foolish enough to prove both on a forum of
your betters"
Ah! I tremble in the presence of my betters.
But, really, I don't think it's helpful to throw around silly
insults.
"GSO = 8x more sunlight"
Not according to the US National Renewable Energy Laboratory Resource
Assessment Program and oodles of other outfits that publish pretty
maps of solar power availability under various circumstances.
According to them the average annual solar insolation recoverable
over more than a million square kilometers described in my previous
post is 416 watts per square meter. 1300 watts/m2 divided by 416
watts/m2 = 3.1.
"GSO = relative invulnerability to terrorists / industrial action"
What about the ground station(s)?
"GSO = no harmful oxygen"
Also no air to breathe or water to drink
"I'm not aware of any ground based power systems that use microwave
power transmission."
According to Shiva Javalagi, Vijay Reddy, Kiran Gullapalli, and Dean
Neikirk of the University of Texas at Austin in "High Power and High
Efficiency Quantum Well Diode Microwave Oscillators:" "DC to RF
conversion efficiency as high as 50 % was obtained under optimum RF
circuit / device matching conditions."
And Mark Obenshain of the NASA Technology Applications Team and the
Research Triangle Institute, and Sammy Nabors of the NASA Marshall
Space Flight Center, "The results were
Class-D power amplifiers with a 49.7% DC-to-RF conversion efficiency
at 2 to 3 GHza significantly higher efficiency than with prior S-
band microwave power amplifiers."
Oh, but I'm not aware of any space based power systems that use
microwave power transmissionor anything else.
"Or alternatively, not particularly clever uses of light weight
mirrors = 2600+ watts."
I have not included in my estimates the possible use of mirrors as a
means to reduce costs, weight, improve performance or to ameliorate
variations in output. There are several reasons for this:
The use of mirrors in space would exacerbate the heat problem
for the power satellite.
Mirrors would introduce into space a whole new set of
steering, orientation, monitoring and control issues, increasing
complexity and probably adversely affecting reliability.
The reduction in the square meters of solar panels and the
consequent reduction in weight and cost would be offset by the weight
and cost of the additional heat control measures, by the weight and
cost of the mirrors and their steering, orientation, monitoring,
communications, and control systems.
Mirrors would place additional demands on the capacities of the solar
panels including the ability to effectively use the increased solar
insolation. These added capacities would have a cost.
Mirrors could be used much more simply to increase the
economic efficiency of an Earth based system. The diurnal, weather
and seasonal variations extant on Earth mean that the solar panels
would usually not be operating at their peak output, and mirrors
could narrow that gap with no increased demands on the capacities of
the solar panels.
Space based mirrors could illuminate an Earth based solar
panel array, increasing efficiency of the Earth based system and
reducing diurnal and other variations.
It seems to me the uncertainties in the use of mirrors and the
offsets between and within the two systems preclude imputing any
significant advantage one way or the other.
"Higher efficiencies have been demonstrated"
This is true about a whole lot of thingstransmutation of the
elements, for instance--but it's pretty meaningless if it doesn't get
out of the lab. A lot of things never get out of the lab.
" temperature control What have you been smoking?"
Temperature control is necessary to optimize the solar panel
productivity, and, in the extreme, to prevent damage to the system.
Temperature control will be more difficult in space since convection
is not an option. The amount of heat produced in space will also be
greater than on Earth, because of higher and continuous solar input,
50% efficiency converting electricity into a power beam, and the heat
generated by station keeping activities not necessary on Earth.
Also, waste heat on Earth can more easily be used for alternative
purposes such as providing heat for buildings, industrial processes
or heating water, perhaps, improving the economy of the whole
system.
About 13 million kilowatts (kws) of energy will impinge on the power
satellite nearly continuously. Of this, about 1.95 million kws (13
million kws * 30% solar panel efficiency * 50% efficiency converting
electricity into a power beam) is transmitted to Earth, and an equal
amount will be deposited on the power satellite as heat.. About half
(or moresolar panels aren't designed to reflect sunlight) of the
remaining 9.8 million kws will be deposited as heat on the solar
array, and the balance will be reflected.
Some kind of cooling system will be needed to radiate this continuous
6.85 million kws of heat-- an enormous amount. Dealing with the
problem is likely to be expensive, heavy and will use lots of the
system's electricity. Efficiency in most solar cells starts dropping
at around 50C, although some solar cells currently used in space
operate efficiently at temperatures approaching 100C. This suggests
that fairly tight temperature control will be necessary.
Temperature control may be the single biggest problem confronting a
solar power satellite, but let's assume that the cost and weight of
the cooling system and associated monitoring and controlling
equipment are negligible, and that power used for all of this will be
only 2% of the electricity generated.
"converting the energy beam back into electricity. Closer to 90%"
>From the Institute of Electronics, Information and Communication
dissertation MIURA and T., N. Shinohara and H. Matsumoto, "Study of a
High Power Rectenna for Microwave Power Transmission", IEICE B,
Vol.J83-B and No.4, 2000, pp.525-533: (abstract) "The rectification
circuit which it developed when microwave input power is 16W,
operates at conversion efficiency approximately 65%. This paper
describes a new rectenna for high power reception at 2.45GHz This
new design achieved an efficiency of 68.6 \ % at the input power
level of 6.7W. The efficiency remains above 65% around an input power
of 16W."
This sounds to me like the technology has a ways to go, but I'm
optimistic and say 70% efficiency. They'll probably get there some
day, at least for 16 watts.
"what matters is not over all system efficacy but life-cycle cost VS
gross profit."
There will be no profit if the cost of electricity produced by power
satellites is more than the cost of electricity produced on Earth.
Zero times 50, or any other number, is still zero.
"This is a multinational list - not an american one."
I'm sure there are many other suitable areas in the world. My pay
for this work isn't high enough to justify researching the globe.
Others can look in places like the Sahara, the Gobi, the Great
Victorian, etc., etc.
"That seems an insanely low price. You can add to that a $3B campaign
to justify 'paving over' tens of kilometers of wilderness and
farmland."
The Springerville Solar Generating System in Arizona is, by some
measures, the largest photovoltaic array in the world. It occupies
44 acres (about 1/10 square kilometer), produces about 8 million kw
hours of electricity per year; and it cost about $8 million. This
cost is reported by the Arizona Corporation Commission, but I
wouldn't bet the farm on its accuracy.
At the price of $1 for materials and construction per kw hour, an 11
terawatt facility would cost $11 billion ($11*10^9). This is based
on an operating plant in the real world that reliably produces and
sells electricity. I think it's quite reasonable to expect economies
of scale, advancement on the learning curve and imminent
technological advances to reduce that cost by at least an order of
magnitude. So I have estimated the cost of materials and
construction at $100 per megawatt of annual output, or $1.1 billion
dollars for an Earth based plant.
The vegetation and wildlife have been minimally disturbed at
Springerville. There's been no paving over, and no campaign.
Ridiculous as it sounds, people pay a premium to buy this "green"
electricity.
I've estimated cost reductions in transport to orbit of more than an
order of magnitude, as well as the cost of materials and construction
in orbit.
"Plus another few billion for the construction cost of the roadway to
get to your building site."
I think this is a rather huge over-estimate; there's a fairly
extensive road system in the Southwest United States, and to a lesser
extent in Northern Mexico.
"My figures come to $70B per 10GW SSPS"
What does that mean in terms of kilowatt hours of electricity
available at the receiving station? What efficiencies, cost to
orbit, etc are you assuming? You're a little light on details.
"Countless industry studies have shown that with a large market for
launch serviceswould enable a price of $200-$1000/kg."
Could you direct me to a few of these studies? Also, what is
the "square-cube rule?
"The cost per kilowatt would be whatever the damn market would bare."
I think you confuse the words "cost" and "price." The price might
be "whatever the damn market would" bear, except that utilities are
regulated industries and there is frequently a direct relationship
between cost and price.
"A cost of $500/kg to LEO is achievable. A nuclear or solar powered
tug would certainly be capable of moving goods to GSO without
doubling costs."
When is the first launch of any of these vehicles scheduled?
# 10057 bybobunf@... on May 26, 2007, 5:01 a.m.
Member since 2021-10-03
--- In spacesettlers@yahoogroups.com, "Combs, Mike"
"I'm curious to know if we're debating you, or essentially debating
Zubrin by proxy."
told that the way to make a statement is to "Tell them what you're
going to say; say it; then tell them what you said." I skipped one
of these three steps.
I'm not aware that Robert Zubrin has written on this subject. Can
you tell me the title of his work on this subject?
"So what the above implies is that it might take 1/10 the output of a
nuclear reactor just to maintain orientation of this satellite.
Maintaining orbital altitude wouldn't even enter into it since there
is no significant drag at GEO altitude."
Station keeping consists of controlling the generation, conversion
and transmission of electricity, monitoring and communications,
aiming the solar panels and the power beam, other orbital,
rotational, and orientation adjustments, monitoring and dealing with
static electric, magnetic, vibration and oscillation issues, and
keeping the whole thing stable.
The power satellite will be subject to perturbations from
gravitational and magnetic anomalies on the Earth, Earth-Moon-Sun
interactions, coronal mass ejections, the influence of Jupiter and
Venus, and many others. Also, I don't think you can just point the
thing at the Sun, and let it go at that. The satellite will revolve
around the Earth every 24 or so hours in an orbit inclined to the
elliptic by differing amounts as the seasons progress, and subject to
other rotational effects of the Earth.
I estimated that the total energy cost for all of this would be about
39 megawatts (1300 watts/m2 * 10^7 meters of solar arrays * 30% solar
cell efficiency * 1%). The International Space Station (ISS) uses
about 65 kilowatts of electricity, but it doesn't use electricity for
orbital, rotational, or orientation adjustments. I haven't found any
way to determine the electrical equivalent of the ISS thrusters, but
I'm sure it would represent a substantial fraction of the total
energy use of the Station.
When one considers that the power satellite will weight about 100
times as much as the ISS, and that it will process a solar flux of 13
gigawatts in a facility that is about 10,000 times as large as the
ISS, a few hundred times as much equivalent electricity use including
the orbital, rotational, and orientation adjustments seems in the
ballpark.
"I've never read anything about SPS to imply that anything beyond
passive cooling would be necessary."
The ISS uses liquid ammonia radiators to dissipate heat. The power
satellite would process an enormously greater energy flux. I think
the heat issue alone could be a show stopper. About 13 million
kilowatts (kws) of energy will impinge on the power satellite nearly
continuously. Of this, about 1.95 million kws (13 million kws * 30%
solar panel efficiency * 50% efficiency converting electricity into a
power beam) is transmitted to Earth, and an equal amount will be
deposited on the power satellite as heat. About half (or moresolar
panels aren't designed to reflect sunlight) of the remaining 9.8
million kws will be deposited as heat on the solar array, and the
balance will be reflected.
6.85 million kws of heat will have to be radiated into space.
"the equivalent of only one shuttle mission per year.. SPS advocates
assumed yet more advanced space transportation systems with
capabilities far beyond even the hypothetical Shuttle ones."
With the "shuttle equivalent missions," I am assuming an equivalent
mission (about 7 crew and 22 tons of cargo), but at 1/10 the cost to
LEO, and 1/5 the cost to geostationary orbit. I think a ten fold
reduction in cost would represent some significant advancement.
Bob
# 10058 byspider_boris@... on May 26, 2007, 1:30 p.m.
Member since 2021-10-03
--- bobunf wrote:
> I estimated that the total energy cost for all of
> this would be about
> 39 megawatts (1300 watts/m2 * 10^7 meters of solar
> arrays * 30% solar
> cell efficiency * 1%).
just from bobunf - that a solar power satellite would
be using photovoltaic arrays. This is incorrect.
The bulk of a solar power satellite would most likely
be a sheet of aluminum foil. Inflatable ribs would
hold that sheet in a paraboloid shape. This giant
reflector would focus sunlight onto a boiler, which
would heat a working fluid, and thus drive a
turbine/generator combination. This would be a Carnot
cycle heat engine. The hot side could get arbitrarily
hot, the cold side would be in the shadow of the
reflector, and thus not much more than the 3 Kelvin
cosmic background. If the hot side is a mere 300
Kelvin, then the efficiency of the system would be 99%
(less frictional losses).
Ed
# 10059 byxenophile2002@... on May 26, 2007, 2:14 p.m.
Member since 2021-10-03
--- In spacesettlers, Ed Minchau wrote:
> bobunf - that a solar power satellite would be using
> photovoltaic arrays. This is incorrect.
I remember reading (more than a decade ago so I don't remember who
wrote it) an essay which asserted that SPS was utterly undoable
because solar wind radiation would degrade the PV cells. Never mind
that PV-based powersat designs have the cells facing *away from* the
sun, never mind the gajillions of satellites currently orbiting our
planet and using PV, and yet somehow still working. Never mind that,
even if that were to be a showstopper (which it wouldn't be), there
are always the powersat designs that don't use PV.
# 10060 bydante_feditech@... on May 26, 2007, 2:24 p.m.
Member since 2021-10-03
> From: bobunf
> But, really, I don't think it's helpful to throw around silly
> insults.
to use google to find out, and you base SSPS station keeping and thermal
requirements on the ISS, then you don't get to say that.
> "GSO = 8x more sunlight"
>
> Not according to the US National Renewable Energy Laboratory Resource
> Assessment Program and oodles of other outfits that publish pretty
> maps of solar power availability under various circumstances.
> According to them the average annual solar insolation recoverable
> over more than a million square kilometers described in my previous
> post is 416 watts per square meter. 1300 watts/m2 divided by 416
> watts/m2 = 3.1.
Let's look at your source then:
http://en.wikipedia.org/wiki/Insolation
http://www.nrel.gov/gis/images/us_pv_annual_may2004.jpg
The map seems a lot more yellow than red to me. An average of about 4 or 5
kwh per day. In space that would be 33 kwh. Seems to hover around x8 or x6 -
and it's certianly not three. Seems you need to find another organisation to
excuse your mistruths.
And this is before the ground panels start to get dirty and suffer other
problems.
> "GSO = relative invulnerability to terrorists / industrial action"
> What about the ground station(s)?
Most ground based designs involve a central tower, which contains
vaulnerable equipment. All forms will have a transfformer farms which can
also be knocked out easily. Only in the SSPS is the actual generator safely
out of reach, and only the SSPS can be retargeted at another ground station
and be back in use in hours.
> "GSO = no harmful oxygen"
>
> Also no air to breathe or water to drink
Which, in case you didn't know, isn't a problem for solar power. In fact
it's a good thing, as any structure needs much less protection from
enviromental degridation.
> "I'm not aware of any ground based power systems that use microwave
> power transmission."
>
> According to Shiva Javalagi, Vijay Reddy, Kiran Gullapalli, and Dean
> Neikirk of the University of Texas at Austin in "High Power and High
> Efficiency Quantum Well Diode Microwave Oscillators:" "DC to RF
> conversion efficiency as high as 50 % was obtained under optimum RF
> circuit / device matching conditions."
Microwave OVENS regularly reach 60% efficiency. TWTs can go up to 70%. And
the latter isn't a piece of lab equipment, it's airborne radar. Again, your
sources seem a little behind the times. Or you migght be mistaking student
lab tsts for cutting edge technology.
> "Or alternatively, not particularly clever uses of light weight
> mirrors = 2600+ watts."
>
> The use of mirrors in space would exacerbate the heat problem
> for the power satellite.
Ten times zero is still zero. An SSPS would be a very shin structure. Every
square kilometer of backside provides black-body cooling. The same 'piece of
paper' arguement would hold true for mirrors. Save that mirrors really could
weigh gramms per square meter (sheets of maylar, not 'mirror mirror on the
wall' style affairs) and could filter out frequencies (UV light for example)
which aren't useful in terms of high efficiency.
> Mirrors would introduce into space a whole new set of
> steering, orientation, monitoring and control issues, increasing
> complexity and probably adversely affecting reliability.
Control problems for large thin structures are something that has not been
studied to any great depth by anyone. There is no reason why mirror
strucctures would be any weaker than 1980s design proposals.
> The reduction in the square meters of solar panels and the
> consequent reduction in weight and cost would be offset by the weight
> and cost of the additional heat control measures, by the weight and
> cost of the mirrors and their steering, orientation, monitoring,
> communications, and control systems.
Beyond a certian point it does become a case of diminishing returns.
> Mirrors could be used much more simply to increase the
> economic efficiency of an Earth based system.
BS. Earth based mirror systems have to be 2 axis control and need to be
cleaned. Space would be fixed and would not need cleaning. Nothing
'simplier' here.
> The diurnal, weather
> and seasonal variations extant on Earth mean that the solar panels
> would usually not be operating at their peak output, and mirrors
> could narrow that gap with no increased demands on the capacities of
> the solar panels.
Tracking motors.
Car rule yet again. North America or Europe would easily soak up all the
output of any SSPS network.
> Space based mirrors could illuminate an Earth based solar
> panel array, increasing efficiency of the Earth based system and
> reducing diurnal and other variations.
Significant increase would be a blinding hazard even at great distance from
the reciever station. The beam would be severely reduced by even light
cloud. Microwaves are better.
> It seems to me the uncertainties in the use of mirrors and the
> offsets between and within the two systems preclude imputing any
> significant advantage one way or the other.
Since they are also unneeded to produce cheap power I woudl not advocate
their use on a first generation installation.
> About 13 million kilowatts (kws) of energy will impinge on the power
> satellite nearly continuously.
Fine. More maths.
1300w per square meter
30% = 952w heat.
http://www.projectrho.com/rocket/rocket3e.html#radiator
With an Re of 1.0 (not real world, but this is just an estimate)
Solar panel tempreature would be 360K = -13*C
> 50% efficiency converting
70% remember. Though I think a good 80,000 tons with an average tempreature
of -13*c would be able to cope. That's an extra 137w of heat per square
meter. With the extra heating the satelite might even get to 0*C!
> (or moresolar panels aren't designed to reflect sunlight) of the
But they do anyway. That's why they're generally shiny.
> Some kind of cooling system will be needed to radiate this continuous
> 6.85 million kws of heat-- an enormous amount.
Let me guess. You once read in a comic book that 'space is hot' and you
weren't paying attention in class when the teacher tried to explain the
difference between 'heat' and 'temperature'.
> "converting the energy beam back into electricity. Closer to 90%"
http://adsabs.harvard.edu/abs/1993STIN...9411357B
As I said, closer to 90%
> "what matters is not over all system efficacy but life-cycle cost VS
> gross profit."
>
> There will be no profit if the cost of electricity produced by power
> satellites is more than the cost of electricity produced on Earth.
> Zero times 50, or any other number, is still zero.
As you have noted elsewhere, green power sells at a premium. It also becomes
economical in the face of carbon taxes. And you have yet to show the SSPS
would cost more.
> "That seems an insanely low price. You can add to that a $3B campaign
> to justify 'paving over' tens of kilometers of wilderness and
> farmland."
>
> The Springerville Solar Generating System in Arizona is, by some
> measures, the largest photovoltaic array in the world. It occupies
> 44 acres (about 1/10 square kilometer), produces about 8 million kw
> hours of electricity per year; and it cost about $8 million. This
> cost is reported by the Arizona Corporation Commission, but I
> wouldn't bet the farm on its accuracy.
> At the price of $1 for materials and construction per kw hour, an 11
> terawatt facility would cost $11 billion ($11*10^9).
1.1*10^13 kwh/year = 350kW - hardly a full scale power station. And for
'only' $11B.
As I said. Insanely low price estimates.
> The vegetation and wildlife have been minimally disturbed at
> Springerville. There's been no paving over, and no campaign.
> Ridiculous as it sounds, people pay a premium to buy this "green"
> electricity.
And you'd only need 30,000 to match the output of one SSPS. That kind of
area will anger a lot of people.
> I've estimated cost reductions in transport to orbit of more than an
> order of magnitude, as well as the cost of materials and construction
> in orbit.
Rocket ecomonics for stupid people:
The NASA facilities for launching the space shuttle employs 20,000.
They all get payed on average over $100,000 per year.
Hence if they launch the shuttle once per year, it costs $2B per launch.
If they launch once every two years it costs $4B per launch.
If they launch twice a year it costs $1B per launch - which is the current
launch rate and cost.
If they launch 10 times a year it would cost $200M - which is close to
competative.
The space shuttle is a horse designed by comettee to fulfil following design
aims in the following order of priority:
1) Be dependent upon workers in 200+ congressional districts
2) Requires an army of 20,000 to build it - so no gets fired
3) Carry 30 tons to orbit and half that home
4) Operate at the absolute edge of performance at the expense of safety and
reliability
5) Be capable of getting into orbit
6) Be safe
7) Be reliable
Because reliability and safety are at the bottom of the list the shuttle can
only launch in perfect conditions, and it takes 30,000 man hours merely to
rebuild the thermal tiles underneith. If the shuttle was run as an HLLV, it
could send up 100 tons and wouldn't need perfect conditions. They coudl be
launched as quickly as they could be built and a suitable launch window was
available. You could also sack about half of the NASA employees, since they
wouldn't be needed to rebuild the orbiter any more. Assume ten flights a
year. Half the facilities costs. Three times the payload. That's thirty
times cheaper with no new technology.
> "Countless industry studies have shown that with a large market for
> launch serviceswould enable a price of $200-$1000/kg."
> Could you direct me to a few of these studies?
Some more ambitious plans:
http://www.abo.fi/~mlindroo/SpaceLVs/Slides/index.htm
And details of the proposed SSX programme:
http://www.jerrypournelle.com/slowchange/SPACECOVER.html
> "My figures come to $70B per 10GW SSPS"
>
> What does that mean in terms of kilowatt hours of electricity
> available at the receiving station? What efficiencies, cost to
> orbit, etc are you assuming? You're a little light on details.
No, that's power delivered to the national power grid.
Satellite weight = 100,000 tons
Launch cost to GEO: $500/kg = $50B
Material & assembally costs: ~$10B
Ground facilities: $10B
(A nimitz CVN costs $10B and that's a lot more ccomplex and weighs 100,000
tons.)
One time start up costs:
SSX type/Ansari-G programme: $20
Construction shack: $10B
Contingancies: $20B
This is a very conservative design.
> Also, what is the "square-cube rule?
Something most school children know.
Use google you lazy git:
http://www.google.co.uk/search?q=square+cube+rule&ie=utf-8&oe=utf-8&aq=t&rls
=org.mozilla:en-US:official&client=firefox-a
> "The cost per kilowatt would be whatever the damn market would bare."
> I think you confuse the words "cost" and "price." The price might
> be "whatever the damn market would" bear, except that utilities are
> regulated industries and there is frequently a direct relationship
> between cost and price.
Internationally that doesn't happen.
Please explain to me how your nation 'regulates' the prices OTEC can charge.
> "A cost of $500/kg to LEO is achievable. A nuclear or solar powered
> tug would certainly be capable of moving goods to GSO without
> doubling costs."
>
> When is the first launch of any of these vehicles scheduled?
Solar powered ion engine? About 9 years ago. See also NASA's Promethius. As
for the rest... NASA does not have a plane capable of flying non stop round
the world without refueling. That doesn't mean succh an achievement is
impossible. See the politics of the space shuttle above for why it doesn't
happen.
With private space developments... Say another ten or twenty years.
John
# 10061 bybobunf@... on May 26, 2007, 2:27 p.m.
Member since 2021-10-03
--- In spacesettlers@yahoogroups.com, Ed Minchau
"the efficiency of the system would be 99% (less frictional losses)."
interesting possibility. Von Braun envisaged just such systems
before the advent of solar cells.
But, there are two conversions: from solar insolation to kinetic
energy and then from kinetic energy to electricity. While the
theoretical maximum efficiency of the first process might approach
100%, there's an awfully long way to go from 1-Tc/Th to something in
real life.
Very large scale modern electric generating plants with a theoretical
maximum Carnot efficiency of about 1-300/1500 = 80% operate at
efficiencies below 40%. If the same ratio held for a plant operating
with a Carnot efficiency of 99%, the efficiency of conversion of
solar insolation to electrical energy would be about 50%, which, I
think, is much more realistic. It is still an efficiency more than
double what current commercially available photovoltaic cells deliver.
It's interesting that this early 19th century technology is so
superior to some darlings of the early 21st century. The
disadvantage to any mechanical system, of course, is moving parts,
and the vastly more complex problems of operations and maintenance.
Interesting the theoretical maximum efficiency of a solar powered
heat engine on Earth could be as much as 1-300/2000 = 85%. Even
higher is heat failure of materials weren't a concern.
Bob
# 10062 bysqorpo@... on May 26, 2007, 2:34 p.m.
Member since 2021-10-03
--- In spacesettlers@yahoogroups.com, "bobunf" wrote:
>
> --- In spacesettlers@yahoogroups.com, "ANTIcarrot"
> wrote:
>
> "a complete loony" "BS" "too stupid to think of solutions" "What
> have you been smoking?" "you're profoundly ignorant, too lazy to
> research the topic, and foolish enough to prove both on a forum of
> your betters"
>
> Ah! I tremble in the presence of my betters.
>
> But, really, I don't think it's helpful to throw around silly
> insults.
are "some" in this group who resort to these kinds of attacks, But I
too do not think they are either helpful nor constructive to the debate..
I think most of you're assumptions are wrong.. It's almost like you're
trying to take "off the self" components to build your estimates
with.. The thing is, these products are 20 to 30 years old and were
never meant for space applications.. The technologies split after the
basic "photovoltaic" transfer (Even this is being challenged in our
research universities and centers)..
The truth is.. You have to be careful where you get your information
from and what other interests might taint the numbers.. The power
companies, oil conglomerates, coal industry, natural gas, propane..
There are a lot of people after those dollars. And with cheap solar
power in the grid, most of them would lose billions.. Even the
government, who should be looking out for what's best for the
"people", instead tend to protect the profits of corporations..
We shouldn't have to "wait" for the technology to develop.. It already
has for the most part.. And could mature quickly if funded properly..
And as for the cost? What about the cost of the energy we use now?
Which is mostly subsidized by the government in the wars we have to
fight, the environment we have to clean up, the tax breaks, the
political and military protections, on, and on, and on..
How much do these things cost??
Do you figure these in your cost comparison??
# 10063 byapsmith@... on May 26, 2007, 3:19 p.m.
Member since 2021-10-03
Good comments - one note, it's not so much of an issue if a solar power
satellite gets a bit hot, unless you need humans to visit and make
repairs. And in that case you could just re-orient it away from the sun
to cool it off. The main efficiency problem with higher temperatures is
increased resistance in the electrical components. But many PV cells
actually run at higher efficiency under concentrator conditions - for
instance Spectrolab's 40.7% efficient cell here:
http://www.gizmag.com/go/6563/
current technology!) would be designed for a certain operating
temperature, with components set up for that; adding radiator elements
to lower that operating temperature might be useful, or might not,
depending on the tradeoffs in the design and what ends up being most
cost-effective. Hard to tell right now.
But it should be noted that a flat surface under direct sunlight does
equilibrate to a higher temperature than a round or more random surface
(input energy is higher per unit surface area, output energy is
proportional to surface area and temperature to the 4th power).
Arthur
# 10064 bybobunf@... on May 26, 2007, 5:11 p.m.
Member since 2021-10-03
--- In spacesettlers@yahoogroups.com, "ANTIcarrot"
wrote:
previous "a complete loony" "BS" "too stupid to think of
solutions" "What have you been smoking?" "you're profoundly ignorant,
too lazy to research the topic, and foolish enough to prove both on a
forum of your betters"
I enter into a discussion of this nature to try to convince others of
the correctness of my viewor, to change my mind. I don't think such
comments convey knowledge, convince anybody, certainly not me and
inhibit whatever benefits discussions such as these may have for you,
me or anybody else.
But, if you insist, I too can insult: you are a fiend, a slippery and
subtle knave, a stony adversary, an inhuman wretch, uncapable of
pity, void and empty from any dram of mercy. Beg that thou may have
leave to hang thyself. You are a tedious fool, contemptuous base
born callet. Dissembling harlot, thou are false in all.
There. Everybody feel better now? Then on to
"Microwave OVENS regularly reach 60% efficiency."
I recently read an article about a series of experiments designed to
test the efficiency of a Magic Chef MCD790SW, 900W microwave oven.
The experiments were conducted by Pablo Pster, who describes himself
as a "Sustainability Engineer."
He observed, "while the microwave is rated at 900W, the Kill-A-Watt
meter registers between 1260W and 1314WOne hypothesisthe 900W
refers to the specifications for the microwave emitter and not the
entire unit and the remaining energy is lost in transforming the 120
VAC to the proper voltage for the emitter" He used "nine glasses in
a 3 x 3 grid and have filled the top row with 100mL of water, the
middle row with 150mL of water, and the bottom row with 200mLThe
best efficiency recorded in this experiment is 33.6%."
Real world. Nothing like it.
"converting the energy beam back into electricity. Closer to 90%
http://adsabs.harvard.edu/abs/1993STIN...9411357B
As I said, closer to 90%"
Did you actually read the article? The 90% refers to a theoretical
maximum. The actual experimental results (in the lab) were under
70%.
Real world, even in a lab; really inconvenient.
Bob
# 10065 bydante_feditech@... on May 26, 2007, 6:57 p.m.
Member since 2021-10-03
> From: bobunf
> I enter into a discussion
now you're avoiding any debate, and trying to excuse your inability to
provide any evidence at all, by hiding behind crodile tears at very accurate
descrriptions of your education and ability to do research.
> But, if you insist, I too can insult:
Insult all you want, but I have *also* suplied *evidence* that many of your
numbers and beliefs are wrong.
> "Microwave OVENS regularly reach 60% efficiency."
> Real world. Nothing like it.
Try compairing apples to apples.
Compairing the total effency of turning 120AC into DC, then into microwaves,
and then into thermal energy does not compair with the kind of transmitter
needed for an SSPS. You're inserting two additional energy convertions. Of
course the overall effency will be lower.
> "converting the energy beam back into electricity. Closer to 90%
> http://adsabs.harvard.edu/abs/1993STIN...9411357B
> As I said, closer to 90%"
>
> Did you actually read the article? The 90% refers to a theoretical
> maximum. The actual experimental results (in the lab) were under
> 70%.
Funny that... A search of that page indicates that despite the presence of
the abstract, the actual article isn't actually present. By contrast this is
what an abstract looks like when an article has been scanned. Not the green
text:
http://adsabs.harvard.edu/abs/1992lbsa.conf..459K
Since you have apparently found it elsewhere, would you care to either
provide a link or upload a copy to the group's file section?
In anycase, it's clear from other abstracts that 70% is not the cast iron
upper limit you seem to believe it is:
http://adsabs.harvard.edu/abs/1993MiOTL...6..655T
> Real world, even in a lab; really inconvenient.
In the real world, not being able to provide a shread of evidence to back up
your claims is also rather inconvenient. And you've provided no evvidence at
all. And I repeat my accusation that have provided no evidence because you
have none.
John
# 10066 byspider_boris@... on May 27, 2007, 11:43 a.m.
Member since 2021-10-03
--- bobunf wrote:
> Very large scale modern electric generating plants
> with a theoretical
> maximum Carnot efficiency of about 1-300/1500 = 80%
> operate at
> efficiencies below 40%. If the same ratio held for
> a plant operating
> with a Carnot efficiency of 99%, the efficiency of
> conversion of
> solar insolation to electrical energy would be about
> 50%, which, I
> think, is much more realistic. It is still an
> efficiency more than
> double what current commercially available
> photovoltaic cells deliver.
hold? What are the losses involved in those
large-scale generation plants? Would they be the same
losses if operating in a vacuum?
Ed
# 10067 bydhandwerk@... on May 29, 2007, 11:08 a.m.
Member since 2021-10-03
Greetings Bob,
compares Apples to Apples, not the Whole Bowl of
Fruit.
A few years ago one of my assignments on a class
project on returning to the moon was to design a
suitable Solar Power Generating System.
I selected the top of Malapert Mountain as it has
something like 95% Sunlight. Diamond Thermionic
Electric generating Devices, because they were said to
be over 92% efficient (of Carnot efficiency), and very
small and light-weight. The next piece was an
Inflatable Concentrating Solar Reflector (which I
think could be modified with some sort of "Heat Pipe"
radiator on the rear (dark) side, to aid in thermal
rejection. The final piece was a frame, circular
track, motor, and small device to adjust the
reflectors tilt (+/- 2.5 degrees) over the course of
the lunar year. In short I came up with a One
Megawatt (electric) Solar Thermionic Electric
Generator (STEG), which had a mass of about 3.5 Tons
metric. The reflector was egg shaped and held in
place by a UV cured plastic foam which filled a
support ring around the 2 or 3 layers of plastic film.
The front was transparent, the middle was aluminized,
and the back was painted black to radiate waste heat.
This is the waste heat that had already been used to
heat the buildings of the lunar settlement.
This would be even better (lighter weight, simpler
design, much smaller structural components) in space.
A 1 MWe STEG would be about 1365 * 0.55 * Pi * R * R 1,000,000. So the diameter would be about 41 m. The
mass would probably come in as low as 2.5 to 3 Ton
metric.
Now I can't tell you what the cost of this unit will
be (Diamonds are not cheap), but vapor deposited
diamond technology has come a long way and the total
mass of diamond I guess, would be under 2/3 of a Kg.
Thermionic electric generation requires a high vacuum
and 1000 degree C. Although this can be provided on
earth, not cheaply.
Next issue in our Apples to Oranges comparison is
launch costs. Since there won't be enough Minotaurs
(Old ICBMs) available let us assume something akin to
the Falcon by SpaceX. They claim $3.5M / Ton.
Electromagnetic Launch would bring it down to $100 /
lb, or $220,000 / Ton. These things could be designed
to virtually self-assemble, but a robot may be needed
for the final touch.
OK, suppose we were able to routinely build a 1 MWe
STEG in space (either at ISS or at GEO) say 1 or 2 a
day. I estimate the total cost at about $2M each
(using EML), or $2 per watt. This is considerably
less than Nuclear, which some decades ago, was $10-12
/ watt. Solar cells are about $4 - 5 / watt, but only
run for 1/4 to 1/3 of a day, on nice days. That makes
them similar to Nuclear. Finally we have to consider
Methane fired gas turbine or similar heat engines.
These are about $2 / watt of AC delivered to the grid.
Oh, you mean we have to deliver our power to a
customer? Well that brings the cost up a factor of 5.
2.5 times due to larger STEG to compensate for losses
in the conversion to Microwaves, atmospheric losses,
then conversion to the AC grid. And 1 more times for
the Microwave Transmission Equipment (and that's a
optimistic assumption). The final 1.5 times would be
for the 1.2 MW Rectannae Array and converters to make
the DC into 60 (or 50) cycle AC.
So the final comparison is: which is cheaper, the $10
/ watt of the SSPS or the $2 / watt or the Methane
Fired Power Station? Remember that methane is cheap
now and very plentiful, but Sunlight is free, and even
a small increase in fuel costs would tip the scale
toward SSPSs.
Also the burning of Hydrocarbons may become more and
more "politically incorrect" as Global Warming issues
become more apparent. In fact, governments may put a
tax on the burning of HCs that bring up the fuel costs
enough to favor SSPSs (regardless of how we feel about
the issue).
With all this said, the cost of $10 / watt is not so
high, with a 2 year payback (which VCs and other high
risk investors like to see that means a wholesale cost
of $0.62 per Kw-hr. With a more reasonable 5 year
payback, that's $0.25 per Kw-hr, and over the life of
the SSPS assuming some maintenance, about $0.05 per
Kw-hr.
The problem is that it is high risk, and it will take
at least $2 to 2.5 B if done by a syndicate of small
to mid-sized companies, specialized in the various
disciplines involved. And 10 or more times that if
done by NASA or any government agency or military type
aerospace company.
Anyway that's my opinion - that Space Apples can't be
compared with Earth Apples, for a number of reasons.
regards,
Dave
--- bobunf wrote:
# 10068 bymikecombs@... on May 29, 2007, 1:40 p.m.
Member since 2021-10-03
From: bobunf
> Northern Hemisphere, than at the height of summer, because of the
> eccentricity of the Earth's orbit.
It seems a bit silly to decide that we can live with the daily 100%
variation in solar availability due to the day/night cycle and then fuss
about the variation due to the eccentricity of Earth's orbit.
> If the excess electricity had to be stored for the six months during
> the year when production was above demand, the required storage would
> be about 23%*.5*11 terawatt hours = about 1,265 million kw hours or
> about 42 days of production.
No, forget about that. Nobody will be investing in expensive storage
systems when SPS energy is involved. During peak hours, other energy
supplies will supplement. During non-peak hours, SPS systems will be
selling excess power to secondary markets on an as-available basis.
> As can be seen,
> there are obvious disadvantages to a system that produces electricity
> varying in the opposite direction of demand.
You might prefer the SPS designs of Geoffrey Landis. They strike me as
sub-optimal, but like you he has an interest in matching available
energy curves to the demand curve. He prefers to consider SPS and
ground-based solar as two components of a complete system.
http://gltrs.grc.nasa.gov/reports/2004/TM-2004-212743.pdf
Regards,
Mike Combs
# 10069 bymikecombs@... on May 29, 2007, 2:03 p.m.
Member since 2021-10-03
From: bobunf
> you tell me the title of his work on this subject?
I don't know if there's an on-line version of his arguments, but he did
have a go at trying to do-in SPS in his book "Entering Space". Of
course at the time he was very concerned that a Senator was trying to
push NASA toward SPS and away from sending people to Mars, so I think
everybody understood that he had a dog in that fight.
> Also, I don't think you can just point the
> thing at the Sun, and let it go at that.
No, I'm not denying that the points you raise are operational
requirements. I'm only saying that supposing they will consume 1/10 the
power output of the average commercial nuclear reactor sounds a bit
excessive.
> I think
> the heat issue alone could be a show stopper.
It's true the SPS intercepts an enormous amount of power, but what you
need to consider is that it's also a very thin object with an enormous
amount of surface area.
> I think a ten fold
> reduction in cost would represent some significant advancement.
I'd agree and will even go on record as saying that a ten fold reduction
in lift costs still probably wouldn't get us to SPS. Those of us who
retain our optimism about SPS think that will just be the beginning of
the improvements we'll see in the next few decades.
Regards,
Mike Combs
# 10070 bycsmyth@... on May 29, 2007, 2:12 p.m.
Member since 2021-10-03
--- In spacesettlers@yahoogroups.com, Dave Handwerk
>
> Greetings Bob,
>
> You have done a very nice job on your argument, but it
> compares Apples to Apples, not the Whole Bowl of
> Fruit.
>
> A few years ago one of my assignments on a class
> project on returning to the moon was to design a
> suitable Solar Power Generating System.
>
> I selected the top of Malapert Mountain as it has
> something like 95% Sunlight. Diamond Thermionic
> Electric generating Devices, because they were said to
> be over 92% efficient (of Carnot efficiency), and very
> small and light-weight. The next piece was an
> Inflatable Concentrating Solar Reflector (which I
> think could be modified with some sort of "Heat Pipe"
> radiator on the rear (dark) side, to aid in thermal
> rejection. The final piece was a frame, circular
> track, motor, and small device to adjust the
> reflectors tilt (+/- 2.5 degrees) over the course of
> the lunar year. In short I came up with a One
> Megawatt (electric) Solar Thermionic Electric
> Generator (STEG), which had a mass of about 3.5 Tons
> metric. The reflector was egg shaped and held in
> place by a UV cured plastic foam which filled a
> support ring around the 2 or 3 layers of plastic film.
> The front was transparent, the middle was aluminized,
> and the back was painted black to radiate waste heat.
> This is the waste heat that had already been used to
> heat the buildings of the lunar settlement.
>
> This would be even better (lighter weight, simpler
> design, much smaller structural components) in space.
> A 1 MWe STEG would be about 1365 * 0.55 * Pi * R * R =
> 1,000,000. So the diameter would be about 41 m. The
> mass would probably come in as low as 2.5 to 3 Ton
> metric.
>
> Now I can't tell you what the cost of this unit will
> be (Diamonds are not cheap), but vapor deposited
> diamond technology has come a long way and the total
> mass of diamond I guess, would be under 2/3 of a Kg.
>
> Thermionic electric generation requires a high vacuum
> and 1000 degree C. Although this can be provided on
> earth, not cheaply.
>
As a layman I'm not qualified to weigh in on the technical
arguments of this topic. I do have two questions and, if you will
permit me, an observation. First, I tried to Wikipedia "Diamond
Thermionic Electric Generating Device" and found no entries. Can you
point me to a source about how this device works? Second, I've seen
the acronym IIRC used several times in this forum. What does this
stand for?
My observation is that it's hard to tell at this point what will be
the "killer app" that will entice large numbers of people and
corporate investors into space. Tourism seems to be a sort of nascent
boutique industry for the very rich so far.
I feel certain that there will arise a compelling comercial
interest in establishing a permanent manned presence in space,
although I can't say whether that interest will flow from the reasons
currently proposed.
Regardless of the actual precipitating industry or enterprise that
sparks our movement into Space, I believe it will happen. When it
does, the profitability of Spaced Based Solar Power Satelites will be
recognized by those who are utilizing Space (perhaps for other
profitable activities).
In a way, it's like the endeavor to build the Hoover Dam.
Originally it was proposed as a flood control and irrigation project.
There was very little in the Arizona/Nevada area at the time the dam
was built that justified the electric power generation capability it
provided. Illustrating a principle already mentioned in this forum,
demand for electricity from the dam has risen to meet availability.
The availability of power from SPS's will find a profitable market
in industrialized nations - who even now are chafing under the
economic, political and environmental burdens of meeting their ever
increasing power requirements. Additionally, a burgeoning market will
be created, I'm sure, in the developing countries that don't yet have
extensive power grids. If power is made available to them by means of
a rectilinear power receiving antenna array, I'm confident that
entepenueurs will waste no time utilizing the cheap local labor and,
subsequently, selling electical products and services to the
newly "affluent" working class.
Chris
1 (current)
2