[HN Gopher] On beaming solar power from low earth orbit
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On beaming solar power from low earth orbit
Author : Jeff_Brown
Score : 41 points
Date : 2021-09-05 18:00 UTC (5 hours ago)
(HTM) web link (innovationfrontier.org)
(TXT) w3m dump (innovationfrontier.org)
| dd444fgdfg wrote:
| and eventually end up with a Dyson Sphere around earth. Doesn't
| sound like a great idea to redirect earth bound heat for
| electricity
| modeless wrote:
| Elon Musk is in dire need of huge and profitable space-based
| businesses to justify his big investment in Starship, which is
| way overkill for any existing space business. And he is
| incredibly motivated to solve climate issues and big into solar
| power specifically. And he has repeatedly pursued far-fetched
| pie-in-the-sky business ideas that are straight out of sci-fi.
| This business would be perfect for him in about ten different
| ways, so the fact that he's _not_ doing it means to me that he is
| completely convinced that it is absolutely impossible to do
| profitably with current or near-future technology.
| polemic wrote:
| That's.. a good point. Reminds me of the moonlanding
| counterfactual: if the USA did _not_ land on the moon, don 't
| you think the Soviet's would've said something about it? Or was
| the cold-war fabricated as well.
| beecafe wrote:
| We need large scale coherent perfect absorbers [0] before we
| can do long distance power beaming. Other than that with a
| solar pumped laser (spread out over many m^2 on the ground to
| reduce the death-ray-ness) you could get decent efficiency.
|
| [0] basically a backwards laser.
| https://en.m.wikipedia.org/wiki/Coherent_perfect_absorber
| darksaints wrote:
| Maybe if we ever find a way to manufacture continuous strands of
| nanotubes, we could create both space elevators as well as wired
| LEO solar power.
| ParoxysmalVigor wrote:
| Approach for energy comparison of solar travel and orbital
| launches: https://en.wikipedia.org/wiki/Delta-v_budget
| Geee wrote:
| While Elon Musk is in the position that he could implement this
| idea, he thinks it's "the stupidest thing ever". [0]
|
| [0] https://www.youtube.com/watch?v=9YZVAMh8b0s
| giantrobot wrote:
| Space based solar is one of many interesting ideas that only
| works if you hand wave a lot of extremely hard or intractable
| problems.
|
| Just to construct some massive structure in space is a monumental
| challenge. Every ton of solar panels or support structure needs
| some bus to get it to the right orbit and maneuver it in place.
| Even if you assume fully automated construction you need buses
| for all the construction robots and tankers to refuel them. Any
| collisions could scrap the whole project by making a debris cloud
| in the same orbital plane as the relatively fragile solar panels.
|
| That all ignores the sourcing of raw materials, finished
| components, fuel, and buses to flit everything around. The "easy"
| answer is "use in-situ materials". In-space mining, refining, and
| fabrication are all entirely unsolved problems. Even the cheapest
| vapor ware SpaceX heavy lift rocket isn't cheap enough to build a
| space based solar plant with components from Earth.
|
| The technical difficulty and cost would be ridiculous compared to
| just building ground based renewables. Ones of billions of
| dollars will get you gigawatts worth of off-shore wind power or
| ground based solar.
|
| Unless you have access to literal magic there's no situation
| where space based solar ends up more efficient or cheaper than
| ground based renewables. The capital expense is literally and
| figuratively astronomical.
| qayxc wrote:
| Even if the "cost" of getting the required infrastructure into
| orbit (assuming Earth-based manufacturing) was close to zero,
| the energy requirements would still eat up the benefits.
|
| SSP only works if every piece of the orbital infrastructure is
| sourced and built outside of Earth's gravity well.
|
| But that's not even the main concern with such system. The
| primary reason we won't see anything like this anytime soon is
| the simple fact that such system can easily be weaponised. An
| SSP is basically a potential space-based weapon. Even if
| there's no intention to use it as such, some governments are
| pretty much guaranteed to see it that way and proceed to
| install actual space-based weaponry in orbit.
| BurningFrog wrote:
| > _An SSP is basically a potential space-based weapon_
|
| Asteroid mining has a similar problem.
|
| Any tech that can send a metal asteroid to Earth orbit can
| also smash it into Buenos Aires.
| nkrisc wrote:
| It doesn't even have to be intentional.
| iso1210 wrote:
| Any tech that can send a 1 ton roadster to mars can crash a
| 1 ton roadster into Buenos Aires at 20,000mph
| foota wrote:
| Wouldn't the car disintegrate in the atmosphere?
| wongarsu wrote:
| Obviously. It all started as a way to drop bombs on
| London, and we are only now reaching a time where the
| majority of rocket models are not derivatives of ICBMs.
|
| Spaceflight is a story of a military technology finding
| civilian use. That has a very different ring to it than
| civilian technology being used as a weapon, even if the
| effect is similar.
| Retric wrote:
| Air resistance limits small kinetic kill weapons. Square
| cube law however means it's less effective for larger
| objects.
| skissane wrote:
| Maybe China will build such a system, not because it makes
| economic sense, rather for national prestige, so they can
| claim to be ahead of the US in that technology. Even if they
| spend a few billion for a modest sized demonstration system,
| that's only a fraction of their national budget.
|
| How would the US respond? Possibly Congress will respond by
| paying to build its own bigger one, again not for the
| economics, simply for the prestige.
|
| I am not sure anyone will care that much about the "space-
| based weapon" angle. If it is a weapon, you just build your
| own and then you have one too, and now both sides have that
| weapon. The ability to have a (possibly illegal) space-based
| weapon yet publicly insist it is just a (completely legal)
| power generation demonstrator may even be attractive to
| military planners on both sides. However, in practice, a
| modest sized technology demonstrator may be quite limited in
| the damage it can inflict, unless it was enhanced with extra
| hardware that made it more obviously a weapon, and harming
| its plausible deniability.
| formerly_proven wrote:
| Is it? Article claims 2 GW / 30 km2, which is ~70 W/m2, a
| fraction of solar irradiance in most places.
| ben_w wrote:
| Sort of yes, sort of no.
|
| If there is at most one space based solar energy system
| visible from any given point on the ground, you can make
| strong safety claims based on wavelength and antenna size.
|
| However, if you limit yourself to one in any given sky, you
| necessarily either (1) put them in high orbit so they do
| useful things in local night, limiting you to a small total
| count planet-wide, or (2) put them in a low orbit, which
| means you can't use them in local nighttime.
|
| If you want nighttime coverage _and_ enough of these
| systems to be relevant to global power -- and the current
| nameplate capacity of ground-based PV is just under a
| terawatt -- you have to worry about multiple orbit-to-
| ground beams being directed at the same spot.
|
| While you _could_ have up to about half a dozen giant
| ground-station for half a dozen giant beams, that needs
| ground level transmission over a significant fraction of
| the surface to be relevant to global energy needs, at which
| point you might as well make a planetary scale power grid
| and get your nighttime supplies from a mixture of the
| rooftops on the other side of the planet and some
| convenient deserts your energy supplier is renting.
| the__alchemist wrote:
| No thank you - I've played Sim City.
|
| (https://simcity.fandom.com/wiki/Microwave_(disaster))
| sircastor wrote:
| This is what I thought of first as well.
| cratermoon wrote:
| Still nope. https://dothemath.ucsd.edu/2012/03/space-based-solar-
| power/
| elcritch wrote:
| It's surprising but even that author turns up a much more
| reasonable return on investment than I expected. His
| calculations suggest it's possible to repay the energy costs,
| including orbit, after only a few years.
|
| Though as he points out there's lots of elements which are
| still impractical. Though I wonder if it could be worthwhile
| given that covering the Sahara with solar panels would change
| the global climate (particularly Brazil's) (1). Space based
| arrays might be a possible way to avoid that. Or perhaps
| provide a power source for remote areas. A starlink for power
| would be intriguing.
|
| 1: https://www.techtimes.com/articles/257268/20210221/sahara-
| de...
| pfdietz wrote:
| Space-based lasers might eventually be a good way to power long
| distance aircraft.
| thiagocsf wrote:
| Charlie Stross recently wrote a blog post about this:
| http://www.antipope.org/charlie/blog-static/2021/09/fossil-f...
|
| He is a lot more optimistic than the average person in this
| comments section.
| AndrewDucker wrote:
| From that post, it gets 4x the efficiency but loses 70% in
| transmission. Which basically cancel each other out.
|
| So the only advantage is the 24x7 availability. Which _is_ a
| big advantage, but I 'm not sure if it's big enough.
| elcritch wrote:
| It should be possible with investment in current tech to get
| transmission losses down to 30-40% or less, IMHO. There's lot
| better power transistors, controls, and simulation to improve
| over the last experiments done decades ago. Some were done in
| the 1970's. Incremental improvements do add up.
| ben_w wrote:
| You could do antipodal HVDC for ~50% loss with the stuff
| currently on the market (3.5% loss per 1000km).
|
| I do like one of the other suggestions to use this for Mars
| solar -- Mars has a much bigger problem with dust blocking
| sunlight than Earth does -- but I don't see it being more
| than experimental here, at least not without a unified
| world government to remove political risks and a whole
| bunch of other tech that might make it redundant anyway.
| Animats wrote:
| _" Many of the raw materials needed for a SSP system can be
| sourced from asteroids or the lunar surface and if these could be
| used to manufacture the SSP components in orbit it would cause
| the cost of the system to plummet. In fact, in-space
| manufacturing may be key to making SSP a cost-competitive energy
| resource."_
|
| This is mostly an excuse to spend money on space programs. It has
| to be cheaper than ground-based solar power with batteries, which
| is working and works better every year.
|
| It's one of those ideas, like automotive battery swapping, which
| were a bet against batteries getting better.
| evgen wrote:
| The interesting thing about space-based solar power is that you
| do not need to direct the beam at the earth. You can also use
| it to beam energy to remote probes and robotic installations.
| If you want to mine asteroids you are better off beaming the
| energy from earth orbit than you are trying to capture solar on
| site. Sending the energy from earth makes it much easier to
| fix/replace the power generation satellite if your remote
| mission is going to depend on that for power generation.
| xt00 wrote:
| Various issues with this tech:
|
| 1. "A 2,000 MW SSP system would require a ground receiver
| covering about 30 square kilometers"
|
| 2. The satellite would be in geostationary orbit, or 22,000 miles
| up, so a directed microwave beam would need to be sent that
| distance in as tight a beam as possible, so likely the
| transmitter side on the satellite would be a large dish (to go
| along with the large surface area of the solar panels, so maybe
| if the solar panels are solved, then a large dish is ok)
|
| 3. Now, if you flew an airplane through that 30 sq km area what
| happens, or various wildlife like birds fly through that area?
| Slight cooking?
|
| 4. Likely that receiver can't be located near a city because
| people would be freaked out about being irradiated by a giant
| microwave beam, so you need transmission towers going across the
| land to the city you are hoping to power
|
| 5. If something goes wrong with your giant power plant in the sky
| you need to spend serious money to go up and try to fix it.
|
| Or, you can dispense with all of that say, ok lets put up a 30 sq
| km solar array and a battery bank with it and just live with the
| fact that you don't get sun all of the time. Far cheaper and
| easier to maintain and upgrade in the future.
|
| If this was a discussion about doing this from a space solar farm
| beaming energy down to mars, then that would be a different story
| since putting mass into orbit around a planet is cheaper than
| getting it onto the ground -- so it may actually make some
| reasonable sense for powering a mars base for some period of time
| rather than deploying tons of solar panels down on the surface of
| mars, then on the surface you come up with a low cost way to
| create some receiver that is low mass and ideally would be just a
| bunch of wire on a spool that somebody drives back and forth
| building up over a month or something.
| [deleted]
| T-A wrote:
| > if you flew an airplane through that 30 sq km area what
| happens, or various wildlife like birds fly through that area?
|
| 30 square kilometers is 3e7 m^2. 2000 MW is 2e9 W. So you're
| looking at less than 70 W/m^2.
|
| For comparison, the solar constant [1] is more than 1300 W/m^2.
|
| So, no cooking.
|
| Also, the receivers would be microwave antennas on poles, i.e.
| they wouldn't monopolize the land they stand on. There is
| concept art from the 70s showing cows grazing between/under
| them.
|
| [1] https://en.wikipedia.org/wiki/Solar_constant
| evgen wrote:
| The receiving rectenna would be large, but from what I know it
| would basically consist of a spaced array of small vertical
| antennas.
|
| The sat does not need to be in geostationary orbit and in fact
| a better solution is to have a constellation at lower orbits.
| This also eliminates the last problem you posed because if
| something goes wrong with the sat you just de-orbit it before
| you had planned and write it off.
|
| If you fly through the beam or walk through it you would not
| know. Do you feel a slight warming when you put your hand on
| top of your wifi antenna?
|
| There are problems with space-based solar and beaming energy,
| but none of your objections make the list.
| senectus1 wrote:
| >in fact a better solution is to have a constellation at
| lower orbits
|
| only that this turns the cost of something that is already
| very very expensive into something that is hideously
| ridiculously expensive.
| xt00 wrote:
| The non-geostationary design in low-earth orbit is mentioned
| with not much detail in this article and would generate far
| less power for a particular receiving location since it only
| periodically receives power -- so there are various
| objections to that approach as well. In the case of the
| geostationary energy being sent through the atmosphere to the
| receiver -- they mentioned 2000MW of power being delivered --
| assuming you use the area of a house (as viewed from top
| down) as an area to compare against, by some rough
| calculations roughly 10KW would be impinging upon a house
| surface that is roughly 1500sqmeters -- so 10KW of microwave
| energy directed into a house area -- that is non-trivial, so
| I assume your comparison between wifi antenna's was in
| reference to the low earth orbit solution -- the geo
| stationary solution referenced in the article is very
| powerful and would be in a totally different class from the
| approx sub 1W range coming from your wifi antennas. So I
| would be worried to walk through it.
| jeffbee wrote:
| 30 sq km isn't even a lot less than the land you'd need for a
| simple terrestrial PV station of the same capacity. NREL said
| in 2012 that the total space needed for PV is 8 acres per MW,
| so 2000 MW would occupy 65 sq km.
| aaron695 wrote:
| > China is investing heavily in SSP and plans to have the first
| operating SSP plant in orbit by the end of the decade
|
| The worlds longest high-voltage subsea cable is only 765 km, the
| EUR2 billion Viking Link project
|
| SSP is a easy 40,000km, 100km through the atmosphere.
|
| So why would the Chinese invest in something so stupid... they
| are not. What they are looking at is stratospheric power.
| Balloons at the 10km - 50km mark. It's still possibly to complex,
| but it's not as childish as space power. Their facility also has
| the military there.
|
| It's a shame people suck, else we could work on real problems
| like extending power grids over the 765 km mark. A world wide
| grid would also nullify the bad weather issue. We do it with
| fibre-optic, and we were doing it in the 90's -
| https://www.wired.com/1996/12/ffglass/ (Neal Stephenson)
|
| A bit of a tech talk on what China is doing here with SSP -
| https://spacewatch.global/2021/07/spacewatchgl-column-dongfa...
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