Here is a lovely design capable of 0 dbm - 1 milliwatt.
http://www.edn-europe.com/highefficienc ... urope.html
All we need to do is to scale it up by 1E6 and we are already in the kilowatt range. And then all you need is 100,000 of them connected together.
Politics is not the only problem.
Space-based power
MSimon wrote:
There is the little problem of junction capacitance my friend. Power scales as junction area (and not well either - due to heat dissipation being easier in smaller objects) and capacitance also scales as area.
Currently power diodes are limited to the MHz range. Getting them to the GHz range? Well it is not just engineering. There are a few physics problems as well.
Engineering is not magic. Although it might seem so to the uninitiated.
For $10 million the estimated time frame is roughly infinite. If you have $100 million to $1 billion I might be able to shorten the time frame considerably. No promises. It requires a breakthrough which is in the real world somewhat unpredictable since a path is not evident.
I'm wondering, and I'm just throwing this out there for thought, how would a SPS be different from the power levels of microwave RADAR systems?
From what I've read, here http://dx.doi.org/10.1117/12.172711,
Some RADAR systems can have a peak power over 30MW, this are assembled from separate smaller antennae. Some work would be needed to reduce the weight but the technology is almost there.
You are correct (sort of). High peak power microwave generators are not uncommon. Continuous power in the 100 KW to 1 MW range is off the shelf. If we go down to 1 KW or so they are produced in the millions.gblaze42 wrote:I'm wondering, and I'm just throwing this out there for thought, how would a SPS be different from the power levels of microwave RADAR systems?MSimon wrote:
There is the little problem of junction capacitance my friend. Power scales as junction area (and not well either - due to heat dissipation being easier in smaller objects) and capacitance also scales as area.
Currently power diodes are limited to the MHz range. Getting them to the GHz range? Well it is not just engineering. There are a few physics problems as well.
Engineering is not magic. Although it might seem so to the uninitiated.
For $10 million the estimated time frame is roughly infinite. If you have $100 million to $1 billion I might be able to shorten the time frame considerably. No promises. It requires a breakthrough which is in the real world somewhat unpredictable since a path is not evident.
From what I've read, here http://dx.doi.org/10.1117/12.172711,
Some RADAR systems can have a peak power over 30MW, this are assembled from separate smaller antennae. Some work would be needed to reduce the weight but the technology is almost there.
What we don't have is power receivers any where near that range.
So we can say that power generation will not be a serious obstacle. Reception (at reasonable efficiency and cost) is something else.
Engineering is the art of making what you want from what you can get at a profit.
A couple of additional points.
I actually looked for some information on eclipse time at GEO distances. I didn't find much except that Earth's shadow at GEO distances is ~ 20 degrees wide, as opposed to a little over 1 degree wide at the Moon's distance. So total eclipses would be ~ 20 times more frequent than lunar eclipses ( Assumeing the Moon's orbit was equatorial, which it is not). T total luner eclipses occur perhaps a few times per year, partial eclipses more frequently. The duration would be based on how fast the satallite transited this region- some math gives a result of 80 minutes. Another Google blurb (the link was broken) mentioned that up to 70 min. eclipse periods per day near the equanoxes . So partial or total loss of output from a few satallites would be significant. Having excess capacity in other satallites would help to minimise the effect, as would scheduled reduction of industrial usage during these periods.
As one post points out, space based solar cells degrad with time, and partical bombardment (solar protons, cosmic ray, etc.)is a major culprit. Shielding against UV or converting UV to longer wavlengths would have no effect on this process. As I mentioned earlier massive solar storms could be devistating. The two modest solar outbursts resulted in ~ 1% loss each.
Orbital debri (man made) is much less and spread out over a much larger area at GEO distances, but not totally absent. I'm more concerned about natural micro meteorites (like in a comets tail (cause of the recurrent meteor showers at various times of the year)), especially a new one that might have many thousands more meteorites per unit volume than the old reliable showers. And solar power collecting satallites would have large surfaces to intercept these dust particles. That is why I wonder if using a large reflecter to collect the light and concentrate it onto much smaller solar panels is more survivable. Alot of tiny holes would not effect the reflectance of a milar sheet much, but the same damage to a solar panel might.
Power transmittance to the ground is certainly a problem. Not mentioned here is the effect of weather. A thick cloud severely attenuates microwave transmission (any useful windows at certain frequencies?). What would dust do?. ie- while space based solar power may be less suseptable to Earth based weather, it is not totally immune. And it is certainly more susceptable to space weather.
The Wikipedia article
http://en.wikipedia.org/wiki/Space_solar_power
mentions transmitting antenna ~ 1 km wide and recieving antennas ~ 10 km wide for a ~ 5-10 Gw GEO satallite. [Edited]
How much average power could you produce on the ground if you replaced the ground antenna surface area with solar cells, thermal collecters, or in places wind turbines?
The effects of solar wind on a satallite would not balance out on opposite sides of the Sun. The solar wind force is always away from the Sun- pushing an object into a higher solar orbit. Tacking back and forth perpendicular to this wind would perhaps maintain position. After all, you would already have large collecters/ sails. It might be profitable to use them instead of ion engines, etc.
Dan Tibbets
I actually looked for some information on eclipse time at GEO distances. I didn't find much except that Earth's shadow at GEO distances is ~ 20 degrees wide, as opposed to a little over 1 degree wide at the Moon's distance. So total eclipses would be ~ 20 times more frequent than lunar eclipses ( Assumeing the Moon's orbit was equatorial, which it is not). T total luner eclipses occur perhaps a few times per year, partial eclipses more frequently. The duration would be based on how fast the satallite transited this region- some math gives a result of 80 minutes. Another Google blurb (the link was broken) mentioned that up to 70 min. eclipse periods per day near the equanoxes . So partial or total loss of output from a few satallites would be significant. Having excess capacity in other satallites would help to minimise the effect, as would scheduled reduction of industrial usage during these periods.
As one post points out, space based solar cells degrad with time, and partical bombardment (solar protons, cosmic ray, etc.)is a major culprit. Shielding against UV or converting UV to longer wavlengths would have no effect on this process. As I mentioned earlier massive solar storms could be devistating. The two modest solar outbursts resulted in ~ 1% loss each.
Orbital debri (man made) is much less and spread out over a much larger area at GEO distances, but not totally absent. I'm more concerned about natural micro meteorites (like in a comets tail (cause of the recurrent meteor showers at various times of the year)), especially a new one that might have many thousands more meteorites per unit volume than the old reliable showers. And solar power collecting satallites would have large surfaces to intercept these dust particles. That is why I wonder if using a large reflecter to collect the light and concentrate it onto much smaller solar panels is more survivable. Alot of tiny holes would not effect the reflectance of a milar sheet much, but the same damage to a solar panel might.
Power transmittance to the ground is certainly a problem. Not mentioned here is the effect of weather. A thick cloud severely attenuates microwave transmission (any useful windows at certain frequencies?). What would dust do?. ie- while space based solar power may be less suseptable to Earth based weather, it is not totally immune. And it is certainly more susceptable to space weather.
The Wikipedia article
http://en.wikipedia.org/wiki/Space_solar_power
mentions transmitting antenna ~ 1 km wide and recieving antennas ~ 10 km wide for a ~ 5-10 Gw GEO satallite. [Edited]
How much average power could you produce on the ground if you replaced the ground antenna surface area with solar cells, thermal collecters, or in places wind turbines?
The effects of solar wind on a satallite would not balance out on opposite sides of the Sun. The solar wind force is always away from the Sun- pushing an object into a higher solar orbit. Tacking back and forth perpendicular to this wind would perhaps maintain position. After all, you would already have large collecters/ sails. It might be profitable to use them instead of ion engines, etc.
Dan Tibbets
To error is human... and I'm very human.
This has two totally different but both correct answers. Since the various proposed rectennas do not consume the space like PV and SolTherm do (i.e. they are akin to chicken wire mesh overhead), the answer can be, very little since there is no land used for the rectenna. OTOH, just talking about using a land area of the same total dimensions, the average output from the PV etc would be consistant with the output from the rectenna. The microwave density is quite small in the beam center, but it is there 24-7-350ish (plus ~22-7-16ish) and the conversion efficiency has been demonstrated to be quite high. Check out the Space Studies Institute at the url I posted earlier folk. Get some reliable data.D Tibbets wrote:How much average power could you produce on the ground if you replaced the ground antenna surface area with solar cells, thermal collecters, or in places wind turbines?
This link doesn't work.KitemanSA wrote:Folks,
Go to the source. SSI has been into this for DECADES. Their data should help this discussion.
Engineering is the art of making what you want from what you can get at a profit.
Half the earth can't see the moon at any one time.Helius wrote:What are you thinking? There aren't even 19 full moons/year. Also, if there's a lunar eclipse, it doesn't matter where in the universe you are. If you can see the moon, you see the eclipse.MSimon wrote:If you count the whole Earth I believe there are 19 lunar eclipses a year.
But maybe the number is the total number of solar + lunar eclipses per year.
Engineering is the art of making what you want from what you can get at a profit.
Maximum possible eclipses per year = 7
Minimum possible eclipses per year = 2
Solar eclipses per year? Never less than 2, or more than 5.
Observer at a particular location will see, on the average,
1 lunar eclipse per year
1 partial solar eclipse every 2 years
1 total solar eclipse every 400 years!
http://www.physics.mcgill.ca/~crawford/ ... ctriv.html
Minimum possible eclipses per year = 2
Solar eclipses per year? Never less than 2, or more than 5.
Observer at a particular location will see, on the average,
1 lunar eclipse per year
1 partial solar eclipse every 2 years
1 total solar eclipse every 400 years!
http://www.physics.mcgill.ca/~crawford/ ... ctriv.html
Engineering is the art of making what you want from what you can get at a profit.
Another issue of space-based solar power is that no one has yet tested out the microwave transmission of electricity. Many theoretical papers were written on this during the heyday of the L-5 Society. However, no one bothered to set up an experimental rig to transmit electricity from, say the roof top of one building, to a receiver on the roof top of a nearby building. The SSI guys, who built demonstrator mass drivers, never tried this experiment. This is an experiment that could be easily done for a few $10k.
John C. Mankins demonstrated microwave power transmission between two of the hawaiian islands last year across 92 miles (148 kilometers). NASA demonstrated transmission of "10's of kilowatts" in 1975. The efficiency of these tests was on the order of 80%
The eclipse issue can be easily avoided by inclineing a geosync orbit so you are always in sunlight. Consider that at geosync the orbit is about 46,000 miles in diameter and the earth is under 8000 miles in diameter. You'd have to keep the beam pointed correctly, but that should be solveable.
The launch costs of mass are the real killer. I've often wondered if PV was the wrong approach. Remember the 'ECHO' series of satellites? Inflated low mass baloons to reflect transmissions? Suppose you made pre-shaped parabolic inflateable baloons half clear, half reflective and used the collected heat to drive a turbogenerator. The normal 60Hz mass could be reduced by useing frequencies much higher than 60Hz.
Microwave transmission isn't the only posibility either. Infrared laser is another option which sidesteps the microwave power device issues.
The eclipse issue can be easily avoided by inclineing a geosync orbit so you are always in sunlight. Consider that at geosync the orbit is about 46,000 miles in diameter and the earth is under 8000 miles in diameter. You'd have to keep the beam pointed correctly, but that should be solveable.
The launch costs of mass are the real killer. I've often wondered if PV was the wrong approach. Remember the 'ECHO' series of satellites? Inflated low mass baloons to reflect transmissions? Suppose you made pre-shaped parabolic inflateable baloons half clear, half reflective and used the collected heat to drive a turbogenerator. The normal 60Hz mass could be reduced by useing frequencies much higher than 60Hz.
Microwave transmission isn't the only posibility either. Infrared laser is another option which sidesteps the microwave power device issues.
Turbogenerators run into the problem of mass from the get go. And getting them space rated is going to be tricky. Esp a zero G condenser. Steam plants on earth are leaky. No problem. You add make up water. Of course water wouldn't be used in space - still. Mfg. tolerances will have to be very tight.Grumalg wrote:John C. Mankins demonstrated microwave power transmission between two of the hawaiian islands last year across 92 miles (148 kilometers). NASA demonstrated transmission of "10's of kilowatts" in 1975. The efficiency of these tests was on the order of 80%
The eclipse issue can be easily avoided by inclineing a geosync orbit so you are always in sunlight. Consider that at geosync the orbit is about 46,000 miles in diameter and the earth is under 8000 miles in diameter. You'd have to keep the beam pointed correctly, but that should be solveable.
The launch costs of mass are the real killer. I've often wondered if PV was the wrong approach. Remember the 'ECHO' series of satellites? Inflated low mass baloons to reflect transmissions? Suppose you made pre-shaped parabolic inflateable baloons half clear, half reflective and used the collected heat to drive a turbogenerator. The normal 60Hz mass could be reduced by useing frequencies much higher than 60Hz.
Microwave transmission isn't the only posibility either. Infrared laser is another option which sidesteps the microwave power device issues.
Engineering is the art of making what you want from what you can get at a profit.
No reason water has to be the working fluid. The mass could easily be reduced by a higher operating frequency. If you've seen and compared 60 Hz stuff to 400 Hz stuff you know what I mean. Suppose everything was built to run at 10's to 100's of Khz. The mass would go way down.Turbogenerators run into the problem of mass from the get go. And getting them space rated is going to be tricky. Esp a zero G condenser. Steam plants on earth are leaky. No problem. You add make up water. Of course water wouldn't be used in space - still. Mfg. tolerances will have to be very tight.
Not saying the mass would be tiny, but that it could be far less than what you'd expect from looking at 60 Hz equipment.