Friday, August 23, 2013

Space-based solar

Source
 With apologies to Roger Pielke, Jr, the problem in tackling the carbon problem is not a lack of technology. It's the inability of our people and our political system to exploit to harness the technology we have through collective political action.

If our country retained the tiniest bit of the ambition and drive that built the Hoover Dam or the Interstate Highway System, we could rip our way through the assumptions of the fossil fuel era like a Sherman tank through a chain-link fence.

Case in point: space-based solar energy.

Space-based solar requires getting a significant amount of mass into geostationary orbit, coping with the degradation of solar panels in that environment, and getting the power back to earth.

There are many speculative technologies for reaching orbit cheaply -- space elevators, magnetic catapults, laser-ablative propulsion, reusable spaceplanes -- but we are approaching a point at which mature conventional rocket technology can, for the first time, move significant masses into orbit without a cost-prohibitive number of launches.

Mature Heavy Lift Launch Vehicles  offer the promise of cutting the cost to low earth orbit (LEO) from $10,000-$15,000/kg today to perhaps $2,200/kg (the estimated cost of a lift from the new Falcon Heavy, a SpaceX rocket in development).

Once you move your payload into LEO, you need to raise it higher, into geostationary orbit (GEO). Fortunately, once in free fall, more stately and deliberate (low-thrust) transportation can be used, such as, for example, ion thrusters. A "tugboat service" could be set up between LEO and GEO, docking with payloads in LEO and gradually moving them into GEO.

Once in geostationary orbit and deployed, a solar panel enjoys half again the power output available on the ground (144%) and can gather that power for >99% of the time. Hence a square meter in orbit will produce between five and ten times as much electricity as the same solar panel on the ground, and it provides baseload power.

The first problem with reaping this bounty is getting their weight into orbit; the second problem is the life expectancy of the panels (the third is getting the power back to earth, which I'll get to in a minute.) It's the second problem, I think, which is the most tricky.

Researchers have succeeded in creating absurdly thin and light solar cells; most recently, the groundwork has been laid for cells two molecules thick. But the orbital environment has an abundance of hard radiation and a certain amount of atomic oxygen that limits the useful life of solar cells. Here too, though, there has been dramatic progress:

Source
A group at NASA took on the challenge of specing out a space-based solar system. Their report is worth a read. They have creative solutions to some of the problems with a space-based system mentioned above (as well as some I hadn't thought about, like waste heat). For example, they limit the mass of expensive and degradable photovoltaics by using a hybrid solar concentrator-PV model -- in plain English, they use reflectors, which are more lightweight and durable, to direct sunlight at a smaller area of solar panels. One model of the end result looks like this:

The large teacup is the reflector array; the small disk is the PV panels. This concentration-PV hybrid approach is also being tried for earth-based systems, and seems promising.

The PV panels, in this design, are cleverly sandwiched together with microwave emitters, which transmit the power to a receiving station below.

The NASA group estimated a final cost of an industrial-scale system along the lines of the above to be about $90/MWh (see page 9). That's a really low number, comparable to new coal plants:


Some have proposed using disposable, foldable ultralight solar panels; your panel collects energy for ten years, and then you simply roll out another thin layer of PV. The article just cited (see part 8) estimates such a system could offer a "power density" (a standard measure of the mass-to-current ratio of space-based PV) of 1.2kW/kg. Ignoring things like the earthbound receiver ("rectenna"), the cost of the panels, and the LEO-GEO shuttle service (because they will essentially be rounding errors for the total cost) a 1,200GW baseload system (supplying about half the current global electrical demand of 20,000TWh/year, or 40% or so after transmission losses) with a forty-year life expectancy would mass about one million tons and cost about $2.3 trillion dollars to orbit with the Falcon Heavy rocket.

That's a staggering sum of money -- almost exactly what we have spent, so far, on the wars in Iraq and Afghanistan.

Despite the remarkably low ROI from that, we are still the richest, most powerful nation in the world, however little it feels that way. It's not about technology. It's about ambition. It's not about how we solve the problem. Contrary to popular opinion, there are many possible solutions. It's about making the decision to solve the problem and concentrating all our efforts on what has to be done.


28 comments:

  1. " the problem in tackling the carbon problem is not a lack of technology. It's the inability of our people and our political system to exploit to harness the technology we have through collective political action."

    Agreed and tweeted

    ReplyDelete
    Replies
    1. Thank you! I find that's the common endpoint of a lot of my thinking these days. The specific choices are less important than the decision to act, as a society, with full determination and all our resources.

      Delete
  2. The Idiot magnet strikes again.

    If you read the NASA document rather carefully, do you think that there might be any problems with the projected mass of the system?

    Since the technologies that are required to make this a practcial proposition do not actually exist, one cannot help thinking that a little more than national ambition is required.

    ReplyDelete
    Replies
    1. "If you read the NASA document rather carefully,"

      Are you implying that you have? Do tell. That would imply a greater degree of patience and focus than you have heretofore shown yourself capable of. Please, explain the problem you think you've found with the mass of the system.

      "Since the technologies that are required to make this a practcial [sic] proposition do not actually exist . . ."

      You have managed to get the point exactly backwards. The technologies do exist, as opposed to, say, the technologies that world allow us to adapt to a world that had warmed three or four degrees.

      You're not going to go down to the hardware store and buy a giant solar power satellite, but no major breakthroughs are required anywhere. Do you have a specific technology in mind that you think is lacking?

      Delete
    2. The mass of the SPS DRM-5 a 2GW installation is put at ~25000 MTonnes. The International space station is 19.1 MT.

      According to table 7-15 this will have hardware costs of ~$6T and earth to orbit costs of $500/kg = 1.275x10^10.

      Also it will require 1000 robots (which don't exist) to assemble the thing.

      There don't seem to be any estimates for the cost of the terrestial receiver but an energy density of 50 wm-2 is mentioned which is going to give a pretty big receiver.

      The mass to be put into geo-synch orbit is enormous by contemporary standards and would only take a mere 1200 Falcon heavy rocket launches to get it up there.

      The technology is extremely speculative as are the costs. Do you think that these might be a trifle optimistic?

      Don't get me wrong, I'm not saying it isn't possible or that it shouldn't be done but the difficulties and costs are enormous.

      The other small problem is that rather a lot of these devices might be required to have a meaningful impact on energy supplies.

      Perhaps the money might be better spent on developing Thorium reactors or does the idiot magnet reject anything that starts with the N word?

      Delete
    3. "earth to orbit costs of $500/kg = 1.275x10^10."

      $12, no almost $13 billion dollars! To put in orbit a power source that could replace three coal power plants. That's a lot. Why, it's almost three times the free money we send to Israel every year! It's almost a third of Charles Koch's net worth! It's almost one-quarter of one percent of the total cost of the wars in Iraq and Afghanistan! (Skip one war, build a couple hundred.)

      So where's the problem? You are struggling with the idea of 1,200 rocket launches? (To LEO, not GEO.) Saddam managed to launch scores of rockets while being pounded by the US Air Force; Hitler managed to invent, deploy, and launch several hundred while being mauled simultaneously by the Russians and ourselves; I think we could manage.

      "The other small problem is that rather a lot of these devices might be required to have a meaningful impact on energy supplies."

      Why is that a problem? Again, 12 billion dollars is really not a lot of money for three power plants' worth of power. It's one forth what Goldman Sachs is worth. Cash them in and get 3-4 systems; you'll get a lot more benefit to society.

      "Perhaps the money might be better spent on developing Thorium reactors or does the idiot magnet reject anything that starts with the N word?"

      You do realize that if I'm an idiot magnet and you continue to come back here, that you are describing yourself? But I suppose it is in the nature of idiots to miss such subtle points.

      If you would spend more time reading and less sneering, you'd know my opinion of nuclear power. I do think it's humorous that you would complain about unproven technology and close with a plea to research technology no one has ever made work on a large scale.

      I am perfectly willing to see large-scale expansion of nuclear power. I believe that however expensive it is, fossil fuels are more so. However destructive to the environment or human health it may be in the worse case, it pales in comparison to the harm done by fossil fuels in the best case.

      There are a number of options available to us, and nuclear is one of them. I don't particularly care what route we take to get to net zero carbon emissions. It's far more important to me that we start as soon as possible, go as fast as possible, and do not stop until we get there/

      Delete
    4. Thanks,
      I coined the Idiot magnet because I cannot imagine the intellectual level of your blog as being anything but that.

      I lurk here because you have have been so bloody rude to sevsral people in the past. Not that we are particularly affected by this but I thought I would have a little gentle fun in challenging your over-intellectualised, intellectuallly subsatnadrad idiocy. In fact I am doing to you what you have done to others.

      Delete
  3. What about long-term heat gain to the atmosphere from the microwave transmission? Long-term, we need to be concerned about that.

    IMO ground-based solar/wind w/ storage plus geothermal and tidal (most of it existing or very near future technology) will be more than sufficient, probably a lot cheaper, and (with the partial exception of geothermal) will result in no net heating of the atmosphere..

    ReplyDelete
    Replies
    1. Not really, Steve. From what I've seen a few percent of power transmitted (compared to, say, 40% at least for fossil, and 70% for nuclear; but you knew that).

      Even renewables will cause similar-sized changes, not by adding heat but by rerouting natural energy streams. You know, "climate change" not "global warming" ;-)

      Delete
  4. It's so rarely mentioned that I have think I'm a victim of the notorious "D-K" effect but with microwave energy transmission systems on this scale, how is reject energy due to transmission inefficiency dealt with?

    Even with careful attention to detail and exploitation of state-of-the-art technology, efficiency of microwave transmitters is such that a bulk power transmission system will need to dispose of eye-popping amounts of energy manifesting itself as warmth. This heat must be gotten rid of or the whole idea seems a nonstarter.

    It seems that a phased array of microwave transmitters might be made such that each transmitter would require a modest passive radiator but the precision required for such a thing to work at the wavelengths necessary is daunting. Larger transmitters would likely require phase-change cooling of some kind.

    Any system for disposing of heat adds mass needing to be put into orbit.

    What's the plan here for getting rid of ~20% of the energy gathered and then inevitably converted to heat in the transmission process?

    Plenty of background on this at history.nasa.gov. Just search for radiator, sublimator or the like.

    ReplyDelete
    Replies
    1. Yep, dumping the heat is a central engineering challenge. Fortunately it stays outside the Earth climate system, but in space the only way to dump heat is by radiation. IOW, big, black surfaces.

      Synchronizing a phased array for microwaves even kilometres across should be doable. Frankly what astronomers already do with optical adaptive mirrors in a one-g environment is more impressive.

      Delete
    2. Replying to myself as a way of helping to visualize this problem, take note of the cargo bay doors of the space shuttles, or the things that look sort of like solar panels but are not on the ISS. Total generation capacity on the shuttles was 21kW continuous. ISS systems are capable of generating about 120kW with consumption ~85kW.

      Belatedly I also see that the article IT steers us to does indeed mention waste heat. Unfortunately this mention is essentially confined to "...topics for future analysis and R&D." Yep.

      Delete
    3. Reply to Martin, I've worked with doing a phased array at ~2GHz and the tolerances even at that relatively low frequency are quite unforgiving. I'm going to hypothesize that even if we're prepared to assume the necessary construction accuracy is possible in the given assembly context, gravitational anomalies affecting and changing the shape of a structure with the required size will make running it efficiently very difficult.

      It is indeed a topic for "future analysis and R&D."

      Delete
    4. Doug, we're talking adaptive optics here. Construction accuracy is irrelevant.

      Delete
    5. Ah, that's an interesting thought. Particularly, I could see using otherwise-annoying thermal properties of materials to help with maintaining geometry.

      Other interesting topics are station-keeping and attitude control. Attitude control could be relatively friendly since such a large structure is naturally conducive to sailing but then we end up with additional challenges for station-keeping.

      As well, the debris/Kessler syndrome business is another worry. With regard to debris, already there should be monetary penalties imposed on organizations not taking responsibility for their debris burden. Everything we do in LEO/MEO is at risk already; it's not impossible that none of these plans can come to fruition simply thanks to such idiocy as the 2007 FY-1C incident. The impact of a large structure on the Kessler threshold could itself be a tragic showstopper. See "Orbital Debris Quarterly," related publications for more info.

      Delete
  5. they use reflectors, which are more lightweight and durable, to direct sunlight at a smaller area of solar panels. One model of the end result looks like this:cheap elo boost
    Cheap League of Legends Coaching

    ReplyDelete
  6. Wireless power transfer seems key to me, and could be developed much further without doing anything in space. If you can practically transfer megawatts, then much cheaper space launches should be possible with a sufficiently powerful ion cannon. But if you can do that, you should also be able to power electric buses/trucks on Earth at a pretty great distance. Let me know when that works.

    ReplyDelete
  7. This blog site is pretty good! How was it made . I view something genuinely interesting about your site so I saved to my bookmarks . You can visit my site.
    solar

    ReplyDelete
  8. Lols Gag is the the Best Lol Network Ever, where you can every thing is lol and Funny, Troll Images, Funny Vidoes, Prank Peoples, Funny Peoples, Prank Images, Fail Pictures, Epic Pictures, Epic Videos, Prank Videos, Fail Videos and Much More Fun and Entertainment, Lols and Gags, Lol Pictures, Lol Videos, Funny Pictures, Lol is the Laugh out of Laugh where you can Fun Unlimited and Laughing Unlimited.
    lolsgag.com

    ReplyDelete
  9. Entertainment for Fun... Entertainment Articles, Entertainment News, Entertainment Pictures, Bollywood, Hollywood and Lollywood Pictures and Videos, Entertainment Latest updates, Hot Entertainment News and Pictures Funny Entertainment Pictures, lol Pictures, Funny Pictures and Much More Fun Only on 1 Current Affairs Network
    hotcurrentaffairs.com

    ReplyDelete
  10. Internet Users have very big Good News, Now you can earn with Just Share an add or picture on Facebook, Facebook is the Most popular Website in the World and you can make unlimited income with Just Facebook Posting Program.
    Genuines Works of Data Entry, Facebook Posting, Copy Pasting, Add Posting, Clicking, Web Surfing, Website Visiting, Article Sharing, Data Sharing, Google Business Plan and Much More Business Plans.
    www.jobzcorner.com

    ReplyDelete
  11. World Most popular Upcoming Latest cars and vehicles, Latest Mazda Models, Racing Cars, International Sport Cars, Concept Cars, PS-Pod, Strange Vehicles, Nissan, Royce Corniche, Ford Concept Cars, Strange Vehicles, Mercedes and More Sport Cars and Vehicles with Pictures and Info
    WorldLatestVehicles.com

    ReplyDelete
  12. Want to Learn Forex Trading and earn with Forex Business...?? The best Forex Trading Learning Website where you can get any thing about Forex, Trading updates, forex trading latest news, forex brokers directory, forex brokers list, Dollars news affairs, Stock Markets, stock market news, stock market analysis, technology news, international forex markets, international forex business news and all updates about Forex Trading
    ForexAffairs.Com

    ReplyDelete
  13. Lols Gag is the the Best Lol Network Ever, where you can every thing is lol and Funny, Troll Images, Prank Peoples, Funny Peoples, funny planet, funny facts, funny cartoons, funny movies pics, iphone funny, funny jokes, Prank Images, Fail Pictures, Epic Pictures, Lols and Gags, Lol Pictures, Funny Pictures, Lol is the Laugh out of Laugh where you can Fun Unlimited and Laughing Unlimited.
    lolsgag.com

    ReplyDelete
  14. Lol and Funny, Troll Images, Prank Peoples, Funny Peoples, funny planet, funny facts, funny cartoons, funny movies pics, iphone funny, funny jokes, Prank Images, Fail Pictures, Epic Pictures, Lols and Gags, Lol Pictures, Funny Pictures, Lol is the Laugh out of Laugh where you can Fun Unlimited and Laughing Unlimited.
    lolsgag.com

    ReplyDelete
  15. Thanks for this informative post and I would like to refer this post,solar fencing is hoping to see more posts from you.

    ReplyDelete