|
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Dust down those orbital power plans
The Australian Government has, for reasons that have much to do with
politics, and little to do with the environment, decided to throw $Au 10 billion into the bottomless pit that is renewable energy. Lest it all get turned into yet more solar panels and windfarms, I invite all comers to submit their plans for orbital power satellites. At least then we might get some technological advance for our money, even though I doubt we'd actually see any orbital power. Sylvia. |
#2
|
|||
|
|||
Dust down those orbital power plans
On Jul 12, 4:17 am, Sylvia Else wrote:
The Australian Government has, for reasons that have much to do with politics, and little to do with the environment, decided to throw $Au 10 billion into the bottomless pit that is renewable energy. Lest it all get turned into yet more solar panels and windfarms, I invite all comers to submit their plans for orbital power satellites. At least then we might get some technological advance for our money, even though I doubt we'd actually see any orbital power. Sylvia. Please let me know more, especially who to talk to. I am hkhenson on Skype or hkeithhenson at gmail dot com Keith |
#3
|
|||
|
|||
Dust down those orbital power plans
On 14/07/2011 10:14 AM, Keith Henson wrote:
On Jul 12, 4:17 am, Sylvia wrote: The Australian Government has, for reasons that have much to do with politics, and little to do with the environment, decided to throw $Au 10 billion into the bottomless pit that is renewable energy. Lest it all get turned into yet more solar panels and windfarms, I invite all comers to submit their plans for orbital power satellites. At least then we might get some technological advance for our money, even though I doubt we'd actually see any orbital power. Sylvia. Please let me know more, especially who to talk to. I am hkhenson on Skype or hkeithhenson at gmail dot com Keith It'll be a while. The government has made the announcement, and supposedly has the numbers in parliament, but the legislation won't be passed until later this year. A single by-election in the meantime could yet lead to the whole thing unravelling. Sylvia. |
#4
|
|||
|
|||
Dust down those orbital power plans
On 12/07/2011 9:17 PM, Sylvia Else wrote:
The Australian Government has, for reasons that have much to do with politics, and little to do with the environment, decided to throw $Au 10 billion into the bottomless pit that is renewable energy. Lest it all get turned into yet more solar panels and windfarms, I invite all comers to submit their plans for orbital power satellites. At least then we might get some technological advance for our money, even though I doubt we'd actually see any orbital power. Sylvia. Didn't we go through this a couple of days ago? |
#5
|
|||
|
|||
Dust down those orbital power plans
On Jul 12, 9:17 pm, Sylvia Else wrote:
The Australian Government has, for reasons that have much to do with politics, and little to do with the environment, decided to throw $Au 10 billion into the bottomless pit that is renewable energy. Lest it all get turned into yet more solar panels and windfarms, I invite all comers to submit their plans for orbital power satellites. At least then we might get some technological advance for our money, even though I doubt we'd actually see any orbital power. Sylvia. You could make a **** load of parabolic reflectors aimed at the hot part of a Stirling engine, these things are about 6m wide and produce about 10Kw A Spanish comp[any makes them. The main problem is the colour, all shiny and not a bit og brown or green on them :-) \ Julian |
#6
|
|||
|
|||
Dust down those orbital power plans
Bohica Bohica wrote:
On Jul 12, 9:17 pm, Sylvia Else wrote: The Australian Government has, for reasons that have much to do with politics, and little to do with the environment, decided to throw $Au 10 billion into the bottomless pit that is renewable energy. Lest it all get turned into yet more solar panels and windfarms, I invite all comers to submit their plans for orbital power satellites. At least then we might get some technological advance for our money, even though I doubt we'd actually see any orbital power. Sylvia. You could make a **** load of parabolic reflectors aimed at the hot part of a Stirling engine, these things are about 6m wide and produce about 10Kw A Spanish comp[any makes them. The main problem is the colour, all shiny and not a bit og brown or green on them :-) That's actually close to what the generating part of an orbital power sat should be - lots of mirrors feeding sunlight to a Brayton cycle gas turbine. Forget acres of solar cells, they are too heavy and too expensive and too fragile. A Brayton cycle engine in that size range is lighter than a Stirling engine, no regenerator needed. Not as efficient, but cheaper and lighter to launch. -- Peter Fairbrother |
#7
|
|||
|
|||
Dust down those orbital power plans
On Jul 19, 5:48 am, Peter Fairbrother wrote:
Bohica Bohica wrote: On Jul 12, 9:17 pm, Sylvia Else wrote: The Australian Government has, for reasons that have much to do with politics, and little to do with the environment, decided to throw $Au 10 billion into the bottomless pit that is renewable energy. Lest it all get turned into yet more solar panels and windfarms, I invite all comers to submit their plans for orbital power satellites. At least then we might get some technological advance for our money, even though I doubt we'd actually see any orbital power. Sylvia. You could make a **** load of parabolic reflectors aimed at the hot part of a Stirling engine, these things are about 6m wide and produce about 10Kw A Spanish comp[any makes them. The main problem is the colour, all shiny and not a bit og brown or green on them :-) That's actually close to what the generating part of an orbital power sat should be - lots of mirrors feeding sunlight to a Brayton cycle gas turbine. Forget acres of solar cells, they are too heavy and too expensive and too fragile. And it would be hard to scale up to the number needed for 100 GW/year of new construction. A Brayton cycle engine in that size range is lighter than a Stirling engine, no regenerator needed. Not as efficient, but cheaper and lighter to launch. The turbines themselves are around 1/10th of a kg/kW. The concentrating reflectors, radiators and heat absorbers seem to make up the bulk of the satellite. I have offered a spreadsheet before to anyone interested. It's partly a refutation of an influential paper published in 1962 and never revisited as far as I can tell. What I did was very simple. In the radiation spread sheet, the first column is absolute temperature, column B is deg C. Col C is radiation per square meter at 0.95, D is at 0.1. E is how many square meters per kW based on C (both sides radiate). D isn't further used. Column E is the area to radiate on kW. F is the Carnot efficiency from 1400 K down to the radiation temperature, G is the 75% of F based on the typical real turbines. H is the square meters required to collect one kW out at 100% of Carnot efficiency based on 1.366kW/meter^2. I is how much area it would take to collect sunlight based on .75 of Carnot efficiency. I is the area it would take to radiate heat from ideal Carnot, K is the area for real (.75) of Carnot. L sums the areas for ideal Carnot cycle, M sums the radiator area plus collector area at the temperature required to get rid of the heat rejected by a real (75%) Carnot cycle. This doesn't take into account the reflector (concentrator) loss or the re-radiation loss from the working fluid heater, but I have reasons to think both will be small. Of course I could have expressed area as a function of the sum of the two areas computed from radiation and Carnot efficiency as a function of T and solved it analytically by setting the derivative to zero. I find spreadsheets give me more insight though. Assuming the radiator and collector mass per square meter is about the same, then you can see from the graph that the minimum occurs a bit above 100 deg C, which is far below the 370-650 deg C quoted in an old paper he http://contrails.iit.edu/DigitalColl...2article42.pdf I can't say for sure what the mass per unit area of radiation or collection are. I need to analyze a canvas tube (like an air mattress) radiator filled with low pressure gas and air float charcoal, Buckey balls or BeO. Assuming they are both around a kg/m^2, a kW should come in around 3.2 kg. Turbines and generators are around 0.1 kg/kW based on Boeing 777 engines. Transmitters have been analyzed at less than a kg/kW. So giving room for such parts as power conductors and the joint to the transmitter, it *might* come in at 5kg/kW. If anyone has some spare web space to hang a small xls file, I can send it to you. Keith -- Peter Fairbrother |
#8
|
|||
|
|||
Dust down those orbital power plans
Keith Henson wrote:
[...] Assuming the radiator and collector mass per square meter is about the same, then you can see from the graph that the minimum occurs a bit above 100 deg C, which is far below the 370-650 deg C quoted in an old paper he http://contrails.iit.edu/DigitalColl...2article42.pdf I'd use something like 1,000 K as Tl. High efficiency and high rate heat radiation in space is problematic unless the temp is high. Radiative heat dispersal is about 100 kW/m^2 for the low temp radiator. Incident radiation on the collector is 1.1 MW/m^2, the mirror (which weighs 0.005 kg/m^2 excluding support) concentrates sunlight from 1.33 kW/m^2 to 1.1 MW/m^2, approximately 820 times at 80% efficiency. Th is 1800 K, Carnot efficiency is 44%, assumed overall efficiency to local electricity is 29%. I can't say for sure what the mass per unit area of radiation or collection are. I need to analyze a canvas tube (like an air mattress) radiator filled with low pressure gas and air float charcoal, Buckey balls or BeO. Assuming they are both around a kg/m^2, a kW should come in around 3.2 kg. I do not understand that. Ignoring the mirror, which I think - actually, I don't know what you are doing - In my example design the single sided collector has a mass of 5 kg/m^2, the double sided radiator 1 kg/m^2. The gas contact areas are 15 times the collecting or radiating areas. The coefficients of convective heat transfer are 800 and 80 W/m^2 K (the gas in the high temperature one is at twelve times the pressure of the low temperature one). The temperature difference across each is 100 K - the collector surface is at 1900K, the radiator surface at 900 K. One m^2 of collector produces 400 kWe at the station, and needs 8 or 10 square meters of radiator, so 15 kg of collectors and radiators are needed to produce 400 kWe, or 0.0375 kg/kW. My numbers might be a little hard to achieve, though they are meant to be only medium-tech at best, so let's be very generous and say 150 grams per kW. That's still 20 times less. Turbines and generators are around 0.1 kg/kW based on Boeing 777 engines. Transmitters have been analyzed at less than a kg/kW. So giving room for such parts as power conductors and the joint to the transmitter, it *might* come in at 5kg/kW. If anyone has some spare web space to hang a small xls file, I can send it to you. Yes please. I seem to be missing something in your argument. Will put it up too. -- Peter Fairbrother Keith -- Peter Fairbrother |
#9
|
|||
|
|||
Dust down those orbital power plans
Sylvia Else wrote:
On 20/07/2011 3:35 AM, Peter Fairbrother wrote: Sylvia Else wrote: On 19/07/2011 10:48 PM, Peter Fairbrother wrote: Bohica Bohica wrote: On Jul 12, 9:17 pm, Sylvia Else wrote: The Australian Government has, for reasons that have much to do with politics, and little to do with the environment, decided to throw $Au 10 billion into the bottomless pit that is renewable energy. Lest it all get turned into yet more solar panels and windfarms, I invite all comers to submit their plans for orbital power satellites. At least then we might get some technological advance for our money, even though I doubt we'd actually see any orbital power. Sylvia. You could make a **** load of parabolic reflectors aimed at the hot part of a Stirling engine, these things are about 6m wide and produce about 10Kw A Spanish comp[any makes them. The main problem is the colour, all shiny and not a bit og brown or green on them :-) That's actually close to what the generating part of an orbital power sat should be - lots of mirrors feeding sunlight to a Brayton cycle gas turbine. Forget acres of solar cells, they are too heavy and too expensive and too fragile. A Brayton cycle engine in that size range is lighter than a Stirling engine, no regenerator needed. Not as efficient, but cheaper and lighter to launch. Will it run maintenance free for a couple of decades? The compressor and turbine, I don't see why not. It's only one moving part, gas bearings are well-developed technology and there are no critical rotating seals. It's much simpler than a Stirling engine, and they reckon they can make those work for long periods in space. The generator? Yes, I'd think so too. The heat exchangers might need some work though, probably multiple redundant circuits. leak sealing and gas refills or something. Likewise the mirrors and mirror pointing stuff. But would it need to last 20 years without maintenance? If you are going to build it in the first place, you'd need a good launch capability anyway. And if it's providing a goodly proportion of your energy, you'd want to be able to fix it if it breaks. no matter what the built-in reliability claimed was. I would assume that there would be enough examples in orbit to provide redundancy in the case of failure. After all, even if you can perform in-orbit maintenance, it's unlikely you can do so at the kind of short notice required for power supply failures that cause blackouts. If it lasts 20 years on average without intervention, then you can probably afford to deorbit it when it breaks, and send up a new one. If you're talking about in-orbit repairs you're almost certainly talking about manned missions, with all that that entails. One thing the shuttle missions have shown us is that getting up there is just the start. Fixing things in zero-g while wearing a space suit is not such an easy task. Hmmm - suppose a 1 million square meter (just over 1.1 km across) mirror shining on a 1000 square meter (35 meters across) collector/Brayton engine/radiator. It collects a little over a gigawatt of solar energy, and produces maybe 500MW of electricity. It short-range-beams that to the downlink satellite, which beams it on to Earth, and that provides 300MW on Earth. The downlink satellite services a flight of - what, 100 of these powersats? - giving 30 GW electrical on Earth, equivalent to 20 large nuclear power stations. Say you have three downlink stations which can be fed by any of the powersats as required, and 300 powersats, that's maybe 80 GWe on Earth, or GWeE. The 300 powersats can be deorbited (or perhaps brought to LEO for refurbishment in a shirt-sleeve atmosphere?) if they fail, so an average life of twenty years is acceptable. I don't think that would be too hard to achieve, though they might need a scheduled resupply of maneuvering fuel. However as they have ample power, ion drives using very little fuel might be okay. I've been considering what to make the powersats from, the hard part is the high temperature solar collector. First, operating fluid. Initial options are hydrogen, helium, methane, water, neon and argon. Strike helium for leakyness and neon for lack of availability. Methane, water and hydrogen are liable to have reactivity problems over 20 years, and we are left with argon. A little heavy, but in the amounts needed the extra weight is lost in the noise. Apart from that, argon is all good. First it's cheap and readily available. It is monatomic, which is thermodynamically useful, as it gives better efficiency. And it is almost completely inert chemically, which means we can use it a high temperatures (with concomitant high efficiency) without worrying too much about chemical corrosion of the parts. On to the collector. It has an area of 1,000 square meters, and receives 1 MW/m2 of energy. That's a blackbody temperature of 2050 K. We could make it really thin, say 0.1 kg/m2 - like a thin sheet of paper - so it would only weigh 100 kg, but a very thin collector would be leaky, and it would require many tiny channels. We could make it from carbon-carbon-carbon-carbon or something, but that would be leaky and fragile. I suggest zirconium (or a zircalloy) at 0.8 mm thick, which would mass about 5 tons. That won't melt even if the gas supply fails. The collector is made from 2 large sheets of 0.4mm zircalloy, one corrugated, which are roller-welded in strips, so as to leave channels for the gas between welds. This provides a very low-leak solution. The waste heat radiator could be made from something less heat resistant and lighter, possibly titanium. It would need an area of about 6,000 square meters, but unlike the collector it could be double sided, meaning 3,000 square meters overall. Mass, about 10 tons. The engine could be about 10 tons - compared to a jet engine which weighs 4 tons in aircraft form and produces 60 MWe in marinised form, that's 15 MW/ton, the spools are simpler and do less work and there are no combustion chambers, so 30 MW/ton should be quite possible using available technology. A bit of handwavium now, I'm out of time: Add 20 tons for the alternator, 5 tons for the beam transmitter, 10 tons for fuel, 5 for pipework etc, and 5 for the mirror, and we have a mass of 70 tons. If the mirror support structure can come in under 30 tons, that's 100 tons for the powersats. 300 of them is 30,000 tons in GEO. Plus you need the downlinks, say 10,000 tons each, or 60,000 tons in total. For 80GWe. -- Peter Fairbrother |
#10
|
|||
|
|||
Dust down those orbital power plans
On Jul 21, 10:48 am, Peter Fairbrother wrote:
Sylvia Else wrote: On 20/07/2011 3:35 AM, Peter Fairbrother wrote: Sylvia Else wrote: On 19/07/2011 10:48 PM, Peter Fairbrother wrote: Bohica Bohica wrote: On Jul 12, 9:17 pm, Sylvia Else wrote: The Australian Government has, for reasons that have much to do wi th politics, and little to do with the environment, decided to throw $Au 10 billion into the bottomless pit that is renewable energy. Lest it all get turned into yet more solar panels and windfarms, I invite all comers to submit their plans for orbital power satellites. At least then we might get some technological advance for our money, even though I doubt we'd actually see any orbital power. Sylvia. You could make a **** load of parabolic reflectors aimed at the hot part of a Stirling engine, these things are about 6m wide and produ ce about 10Kw A Spanish comp[any makes them. The main problem is the colour, all shiny and not a bit og brown or green on them :-) That's actually close to what the generating part of an orbital powe r sat should be - lots of mirrors feeding sunlight to a Brayton cycle gas turbine. Forget acres of solar cells, they are too heavy and too expensive and too fragile. A Brayton cycle engine in that size range is lighter than a Stirling engine, no regenerator needed. Not as efficient, but cheaper and lighter to launch. Will it run maintenance free for a couple of decades? The compressor and turbine, I don't see why not. It's only one moving part, gas bearings are well-developed technology and there are no critical rotating seals. It's much simpler than a Stirling engine, and they reckon they can mak e those work for long periods in space. The generator? Yes, I'd think so too. The heat exchangers might need some work though, probably multiple redundant circuits. leak sealing and gas refills or something. Likewis e the mirrors and mirror pointing stuff. But would it need to last 20 years without maintenance? If you are goi ng to build it in the first place, you'd need a good launch capability anyway. And if it's providing a goodly proportion of your energy, you'd want t o be able to fix it if it breaks. no matter what the built-in reliabilit y claimed was. I would assume that there would be enough examples in orbit to provide redundancy in the case of failure. After all, even if you can perform in-orbit maintenance, it's unlikely you can do so at the kind of short notice required for power supply failures that cause blackouts. If it lasts 20 years on average without intervention, then you can probably afford to deorbit it when it breaks, and send up a new one. If you're talking about in-orbit repairs you're almost certainly talking about manned missions, with all that that entails. One thing the shuttl e missions have shown us is that getting up there is just the start. Fixing things in zero-g while wearing a space suit is not such an easy task. Hmmm - suppose a 1 million square meter (just over 1.1 km across) mirror shining on a 1000 square meter (35 meters across) collector/Brayton engine/radiator. It collects a little over a gigawatt of solar energy, and produces maybe 500MW of electricity. It short-range-beams that to the downlink satellite, which beams it on to Earth, and that provides 300MW on Earth. Unless you know something I don't, you take a ~50% hit in each microwave link. The downlink satellite services a flight of - what, 100 of these powersats? - giving 30 GW electrical on Earth, equivalent to 20 large nuclear power stations. Say you have three downlink stations which can be fed by any of the powersats as required, and 300 powersats, that's maybe 80 GWe on Earth, or GWeE. The 300 powersats can be deorbited (or perhaps brought to LEO for refurbishment in a shirt-sleeve atmosphere?) It's a good idea. Boeing first thought about it in the 70s and even did some great artwork of assembling power sats in LEO. Then someone worked out what would happen to them in the months of going from LEO to GEO on ion engines. It was not nice. Even in those days they got hit several times with space junk. :-( if they fail, so an average life of twenty years is acceptable. I don't think that would be too hard to achieve, though they might need a scheduled resupply of maneuvering fuel. However as they have ample power, ion drives using very little fuel might be okay. I've been considering what to make the powersats from, the hard part is the high temperature solar collector. First, operating fluid. Initial options are hydrogen, helium, methane, water, neon and argon. Strike helium for leakyness and neon for lack of availability. Methane, water and hydrogen are liable to have reactivity problems over 20 years, and we are left with argon. A little heavy, but in the amounts needed the extra weight is lost in the noise. Apart from that, argon is all good. First it's cheap and readily available. It is monatomic, which is thermodynamically useful, as it gives better efficiency. And it is almost completely inert chemically, which means we can use it a high temperatures (with concomitant high efficiency) without worrying too much about chemical corrosion of the par ts. Argon is good, but it turns out that supercricial CO2 is even better. I favor two cycles because the more heat you can convert to electric power, the less you have to radiate. On to the collector. It has an area of 1,000 square meters, and receives 1 MW/m2 of energy. That's a blackbody temperature of 2050 K. We could make it really thin, say 0.1 kg/m2 - like a thin sheet of paper - so it would only weigh 100 kg, but a very thin collector would be leaky, and it would require many tiny channels. We could make it from carbon-carbon-carbon-carbon or something, but that would be leaky and fragile. I suggest zirconium (or a zircalloy) at 0.8 mm thick, which would mass about 5 tons. That won't melt even if the gas supply fails. The collector is made from 2 large sheets of 0.4mm zircalloy, one corrugated, which are roller-welded in strips, so as to leave channels for the gas between welds. This provides a very low-leak solution. The waste heat radiator could be made from something less heat resistant and lighter, possibly titanium. It would need an area of about 6,000 square meters, but unlike the collector it could be double sided, meaning 3,000 square meters overall. Mass, about 10 tons. The engine could be about 10 tons - compared to a jet engine which weighs 4 tons in aircraft form and produces 60 MWe in marinised form, that's 15 MW/ton, the spools are simpler and do less work and there are no combustion chambers, so 30 MW/ton should be quite possible using available technology. A bit of handwavium now, I'm out of time: Add 20 tons for the alternator, 5 tons for the beam transmitter, 10 tons for fuel, 5 for pipework etc, and 5 for the mirror, and we have a mass of 70 tons. If the mirror support structure can come in under 30 tons, that's 100 tons for the powersats. 300 of them is 30,000 tons in GEO. Plus you need the downlinks, say 10,000 tons each, or 60,000 tons in total. For 80GWe. That's kind of optimistic. 60,000 t for 80 GW is 750 t per GW. My numbers (and Dr. Phil Chapman's) come in at around 5,000 tons per GW, 6.7 times as high. On the other hand, Solare's numbers come out a lot lighter so you are not that far from various estimates. Keith -- Peter Fairbrother |
|
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Dust down those orbital power plans | Sylvia Else[_2_] | Policy | 19 | July 16th 11 10:05 AM |
Europe, Russia discuss 'orbital shipyard' plans | [email protected] | Policy | 50 | May 23rd 09 11:02 PM |
PopSci feature on Robert Bigelow and "CSS Skywalker" orbital resort plans | Neil Halelamien | Policy | 4 | February 17th 05 10:23 AM |
Rutan describes plans for orbital spacecraft | Neil Halelamien | Policy | 14 | October 11th 04 01:45 AM |
calculations of orbital decay for the Nebular Dust Cloud theory why has no astronomer or physicist calculated | Archimedes Plutonium | Astronomy Misc | 6 | January 13th 04 08:42 PM |