Author Topic: Space-based solar power for Earth  (Read 189318 times)

Offline Robotbeat

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Re: Space-based solar power for Earth
« Reply #520 on: 06/09/2016 05:34 pm »
I worked on a concept at Uni back in the day and my own idea which I still find very attractive is to just put the sats in LEO and have two GEO satellites with individual mirrors per LEO sat. Instead of microwave beaming you use laser to transfer the energy from the LEO sat to the GEO sat to the groundstation on Earth. From LEO to GEO the airy disk (which contains 86% of the energy of the laser beam) only widens to something like 5 meter. If the laser would have a pointing accuracy of an order of magnitude worse than the hubble telescope it would still be very spot on.
Lasers are much less efficient than microwave generators.  Photovoltaics, even designed for a single wavelength, can't beat a rectina for efficiency.  Lasers don't deal well with overcast, while microwaves of a well chosen wavelength have little loss through the atmosphere even with heavy clouds.  On the other hand, you can get a much tighter, even dangerous, power beam.
ACTUAL very high frequency (i.e. ~1mm) microwave generators and rectennas are actually pretty close to the round-trip efficiency of direct-diode lasers and concentrating, single-wavelength photovoltaics.
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Offline SICA Design

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Re: Space-based solar power for Earth
« Reply #521 on: 06/10/2016 07:19 am »
I worked on a concept at Uni back in the day and my own idea which I still find very attractive is to just put the sats in LEO and have two GEO satellites with individual mirrors per LEO sat. Instead of microwave beaming you use laser to transfer the energy from the LEO sat to the GEO sat to the groundstation on Earth. From LEO to GEO the airy disk (which contains 86% of the energy of the laser beam) only widens to something like 5 meter. If the laser would have a pointing accuracy of an order of magnitude worse than the hubble telescope it would still be very spot on.
Lasers are much less efficient than microwave generators.  Photovoltaics, even designed for a single wavelength, can't beat a rectina for efficiency.  Lasers don't deal well with overcast, while microwaves of a well chosen wavelength have little loss through the atmosphere even with heavy clouds.  On the other hand, you can get a much tighter, even dangerous, power beam.
ACTUAL very high frequency (i.e. ~1mm) microwave generators and rectennas are actually pretty close to the round-trip efficiency of direct-diode lasers and concentrating, single-wavelength photovoltaics.

Is that not another way of saying 1mm (300 GHz) microwave conversion and atmospheric propagation is far less efficient than "well chosen" 52mm (5.8 GHz) or 122mm (2.45 GHz) wavelengths?

Offline Hanelyp

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Re: Space-based solar power for Earth
« Reply #522 on: 06/10/2016 03:24 pm »
The chief advantage of space based solar over ground based is the potential for near 24/7/365 operation.  A power link that has trouble with overcast defeats that advantage.

Uptime might be improved against the solstice outage if multiple solar satellites can be coordinated to deliver coherent microwaves to a receiving station.  Instead of one HUGE satellite, a swarm of smaller ones.

Offline Robotbeat

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Re: Space-based solar power for Earth
« Reply #523 on: 06/10/2016 03:45 pm »
I worked on a concept at Uni back in the day and my own idea which I still find very attractive is to just put the sats in LEO and have two GEO satellites with individual mirrors per LEO sat. Instead of microwave beaming you use laser to transfer the energy from the LEO sat to the GEO sat to the groundstation on Earth. From LEO to GEO the airy disk (which contains 86% of the energy of the laser beam) only widens to something like 5 meter. If the laser would have a pointing accuracy of an order of magnitude worse than the hubble telescope it would still be very spot on.
Lasers are much less efficient than microwave generators.  Photovoltaics, even designed for a single wavelength, can't beat a rectina for efficiency.  Lasers don't deal well with overcast, while microwaves of a well chosen wavelength have little loss through the atmosphere even with heavy clouds.  On the other hand, you can get a much tighter, even dangerous, power beam.
ACTUAL very high frequency (i.e. ~1mm) microwave generators and rectennas are actually pretty close to the round-trip efficiency of direct-diode lasers and concentrating, single-wavelength photovoltaics.

Is that not another way of saying 1mm (300 GHz) microwave conversion and atmospheric propagation is far less efficient than "well chosen" 52mm (5.8 GHz) or 122mm (2.45 GHz) wavelengths?
Calculate the size of satellite antenna and ground station for 2.45GHz. You're talking a dish 1km wide for transmitting and 4km wide for receiving.

Additionally, please show me microwave conversion efficiencies for specific components in that range, as well as rough operating temperatures.
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Offline SICA Design

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Re: Space-based solar power for Earth
« Reply #524 on: 06/10/2016 05:52 pm »
Calculate the size of satellite antenna and ground station for 2.45GHz. You're talking a dish 1km wide for transmitting and 4km wide for receiving.

Additionally, please show me microwave conversion efficiencies for specific components in that range, as well as rough operating temperatures.

Actually the multiple of the diameters at 2.45 GHz is more like 10.8E6 m^2 (i.e. 11km rectenna for 1km dish*), or 4.5E6 m^2 at 5.8 GHz. HESPeruS has an effective transmitter aperture of 4.4 km; which is of the right order to match its (non rotating) solar-collecting area (5 - 10 GW sunlight) for delivering 1 GW to the grid.

This could focus down to a 1km rectenna, BUT:

(a) a 1km Airy disc (for 1 GW to grid) would have a central beam intensity of 1.4 kW/m^2 which would be deemed unacceptable for overflying aircraft or wildlife - it is deliberately defocused (by means of the 40.68 MHz pilot beam emitted from the rectenna site) for a minimum 4.6km Airy disc. This gives a central beam intensity of 300 W/m^2, or under one-third equatorial noon sunlight intensity.

(b) HESPeruS is optimised for latitudes above 45deg, where the incoming beam angle may be as low as 20 degrees above the horizon, stretching the Airy disc by nearly 200%. For this reason, the rectenna diameter is chosen as 12 km, which also increases the 20deg beam interception to 88.5% - or for a zenith beam from 84% (just for the Airy disc) to 94.7%.

Uniquely for HESPeruS, a 12km rectenna would allow a one-tenth scale prototype to deliver 100 MW to the grid from its target Molniya orbit. This could later be expanded to full scale.

This one-tenth scaling, reduced mass from essentially flat film construction, coupled with the fact that a Molniya orbit requires less than half the orbital energy of GSO, allows a fully working prototype to be demonstrated at far lower cost than other GSO/GEO SBSP systems.

As requested, I've included examples of actual demonstrated rectenna efficiencies - which is mostly a function of schottky diode efficiency:  http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20020091852.pdf

Just recently a group based at Manchester University has announced a graphene-based Ballistic Rectifier which has zero band-gap (a function which normally limits conversion efficiency at lower field strengths): http://www.nature.com/ncomms/2016/160531/ncomms11670/abs/ncomms11670.html

 * A parabolic dish is a bit too 70's for me - try google "planar phased array"
« Last Edit: 06/10/2016 05:55 pm by SICA Design »

Offline TrevorMonty

Re: Space-based solar power for Earth
« Reply #525 on: 03/23/2018 01:54 am »
The development of SBSP as always is financial hurdle. SpaceX BFR and Blue NG by lowering cost of access to space may help lower cost of SBSP but it will need a large space base ISRU infrastructure to really bring price down to 10cUnit.

What SBSP really needs is someone willing spend a lot more per Unit to help start ball rolling. Yet again it could be internet companies to rescue with their huge cash reserves and enviroment conscious.
Google, Amazon and Microsoft are all committed to reducing their carbon foot print.

https://www.geekwire.com/2018/microsoft-makes-largest-corporate-solar-deal-u-s-history-buying-power-750000-solar-panels/

I'm picking Jeff Bezo will be one of first, whether it is via Blue, Amazon or consortium I don't know.

Offline TrevorMonty

Re: Space-based solar power for Earth
« Reply #526 on: 04/22/2021 03:15 am »

Youtube video on AFRL progress in space solar power. Google "AFRL SSPIDER" to find more.

https://twitter.com/DrPhiltill/status/1384882871740125187?s=19

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Offline CameronD

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Re: Space-based solar power for Earth
« Reply #527 on: 04/22/2021 05:10 am »

Youtube video on AFRL progress in space solar power. Google "AFRL SSPIDER" to find more.

Presumably you mean "AFRL SSPIDR"??..  odd that they've been working on this for years now, and yet only just released this video.

https://afresearchlab.com/technology/successstories/space-power-beaming/

FWIW. it's a research project:  "AFRL is not developing the final system, but instead is collaborating with Northrop Grumman and the Naval Research Laboratory in researching, maturing, and demonstrating the technologies required to build the objective system."

My guess is that (translated from spin-speak) that means, roughly:  "We think it's a great concept, but if you're looking for something commercially viable in your life-time, there's nothing to see here.. Move along!!"
 
« Last Edit: 04/22/2021 05:19 am by CameronD »
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going to land, and it could be dangerous sitting under them as they fly overhead.

Offline edzieba

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Re: Space-based solar power for Earth
« Reply #528 on: 04/22/2021 10:08 am »
It's more of a desire to mature the technology to the point that - if it is needed, e.g. getting embroiled in some long-term expeditionary conflict again - it is high enough TRL to start farming out contracts for manufacture and launch rather than for research and development.

Offline TrevorMonty

Re: Space-based solar power for Earth
« Reply #529 on: 04/22/2021 10:21 am »
Long way from commercial product but you have to start somewhere. Most importantly somebody developing this technology and willing to pay for flight demos.

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Offline Frogstar_Robot

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Re: Space-based solar power for Earth
« Reply #530 on: 04/22/2021 10:48 am »

Youtube video on AFRL progress in space solar power. Google "AFRL SSPIDER" to find more.

Presumably you mean "AFRL SSPIDR"??..  odd that they've been working on this for years now, and yet only just released this video.

https://afresearchlab.com/technology/successstories/space-power-beaming/

April 2122 is "Earth Day", so apparently it is related to that.

"Science fiction to reality" - the video ends with a receiving station which looks like a 1m dish, which is science fiction. The path from SF to reality is mapped by the Gartner "Hype Cycle" [1]. On there, SBSP is still at R&D stage, so a long way to go.

In general, the nature of the ground equipment is glossed over.

There are reports apparently based on an AFRP press release (e.g. [2]) which say
Quote
A major objective of SSPIDR is to break the one-meter-squared aperture threshold for solar power capture and conversion, and beam that energy to the ground which AFRL will do with Arachne – SSPIDR’s flagship flight experiment.

I am wondering what is the "1m^2 aperture threshold" they refer to?

ARACHNE is the in-space demonstrator mission due to launch in 2024 [3]. I didn't find if they have a LV booked yet.

[1] https://www.gartner.com/en/documents/3887767/understanding-gartner-s-hype-cycles
[2] https://technologynewsroom.com/solar-power/beaming-solar-power-from-satellite-array/
[3] https://afresearchlab.com/news/afrl-receives-first-component-of-solar-beaming-project/
« Last Edit: 04/22/2021 06:34 pm by Frogstar_Robot »
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Offline high road

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Re: Space-based solar power for Earth
« Reply #531 on: 04/22/2021 11:27 am »
when is it supposed to launch?

Offline Frogstar_Robot

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Re: Space-based solar power for Earth
« Reply #532 on: 04/22/2021 06:34 pm »
when is it supposed to launch?

What do you mean by "it"?
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Offline TrevorMonty

Re: Space-based solar power for Earth
« Reply #533 on: 10/12/2023 09:44 am »
Caltech tile concept for SBSP.

https://www.researchgate.net/publication/361417363_A_Lightweight_Space-based_Solar_Power_Generation_and_Transmission_Satellite

Basic figures based on their 651kg GEO concept vehicle, will deliver 491kw to grid or 0.75kw/kg to grid based on 10% overall efficiency they say between 7-14%. The collection area is 60x60m.
They use x20 concentrators to maximise solar cells power generation.
Paper also went into launch costs but given how fluid they are becoming not that important at present. Likely to be lot cheaper when this launches.

While getting from LEO to GEO is currently very expensive using chemical proplusion and even SEP there are other alternatives. Solar sails driven by high powered lasers on earth, something Caltech is also working on.

Edit. Beam Microwave propulsion is another way to transport these from LEO to GEO. Microwave beam heats hydrogen resulting in very simple 900ISP thruster. With microwave power coming from GEO power farm.
« Last Edit: 10/12/2023 10:04 am by TrevorMonty »

Online redneck

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Re: Space-based solar power for Earth
« Reply #534 on: 10/12/2023 11:45 pm »
Caltech tile concept for SBSP.

https://www.researchgate.net/publication/361417363_A_Lightweight_Space-based_Solar_Power_Generation_and_Transmission_Satellite

Basic figures based on their 651kg GEO concept vehicle, will deliver 491kw to grid or 0.75kw/kg to grid based on 10% overall efficiency they say between 7-14%. The collection area is 60x60m.
They use x20 concentrators to maximise solar cells power generation.
Paper also went into launch costs but given how fluid they are becoming not that important at present. Likely to be lot cheaper when this launches.

While getting from LEO to GEO is currently very expensive using chemical proplusion and even SEP there are other alternatives. Solar sails driven by high powered lasers on earth, something Caltech is also working on.

Edit. Beam Microwave propulsion is another way to transport these from LEO to GEO. Microwave beam heats hydrogen resulting in very simple 900ISP thruster. With microwave power coming from GEO power farm.

There are concepts for getting far more Isp from beamed power to hydrogen. One of them involves "smog" in the hydrogen that absorbs the beamed energy rather than the physical engine. Supposed t do wonders for engine cooling with a far hotter reaction mass. .Beaming from astern obviously.

Offline Asteroza

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Re: Space-based solar power for Earth
« Reply #535 on: 10/13/2023 01:40 am »
Caltech tile concept for SBSP.

https://www.researchgate.net/publication/361417363_A_Lightweight_Space-based_Solar_Power_Generation_and_Transmission_Satellite

Basic figures based on their 651kg GEO concept vehicle, will deliver 491kw to grid or 0.75kw/kg to grid based on 10% overall efficiency they say between 7-14%. The collection area is 60x60m.
They use x20 concentrators to maximise solar cells power generation.
Paper also went into launch costs but given how fluid they are becoming not that important at present. Likely to be lot cheaper when this launches.

While getting from LEO to GEO is currently very expensive using chemical proplusion and even SEP there are other alternatives. Solar sails driven by high powered lasers on earth, something Caltech is also working on.

Edit. Beam Microwave propulsion is another way to transport these from LEO to GEO. Microwave beam heats hydrogen resulting in very simple 900ISP thruster. With microwave power coming from GEO power farm.

There are concepts for getting far more Isp from beamed power to hydrogen. One of them involves "smog" in the hydrogen that absorbs the beamed energy rather than the physical engine. Supposed t do wonders for engine cooling with a far hotter reaction mass. .Beaming from astern obviously.

Not necessarily, some solar moth butterfly mirror designs allowed mirror slewing while firing through an engine chamber window into the hydrogen.

Some RF SPS designs proposed beaming RF power from the ground into the SPS antenna, to supply electric thrusters with power, though I think most of the modern tile design distributed systems are fundamentally incapable of doing this well. If you have the infrastructure to beam from the ground, it might make more sense to beam to a rectenna equipped OTV tug rather than having a SPS bootstrap itself up from a LEO assembly orbit.

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Offline Robotbeat

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Re: Space-based solar power for Earth
« Reply #537 on: 01/20/2024 12:26 am »
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline Twark_Main

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Re: Space-based solar power for Earth
« Reply #538 on: 01/22/2024 10:39 pm »
The Dream is Over?

https://spacenews.com/nasa-report-offers-pessimistic-take-on-space-based-solar-power/
Pretty terrible report. Unprofessional and technically incorrect.

The report is fine. The headline writing is (as always and by design) unnecessarily divisive and clickbait-y.

From the article:

Quote from: SpaceNews
The NASA study did address the baseline model's sensitivity to factors such as lower launch costs, use of electric propulsion and assuming a longer lifetime for components in GEO than the 10 years included in the baseline. Incorporating all of those factors reduces the electricity costs of the SBSP systems to levels similar to terrestrial renewable alternatives.

From the report:

Quote from: NASA
The following combination of revised assumptions yields SBSP solutions that are cost competitive with terrestrial alternatives, with lower GHG emissions:

    • lower launch cost: $50M per launch, or $500/kg; $425/kg with 15% block discount

    • electric propulsion orbital transfer from LEO to GEO

    • extended hardware lifetimes: 15 years

    • cheaper servicer and debris removal vehicles: $100M and $50M, respectively

    • efficient manufacturing at scale: learning curves of 85% and below

Our sensitivity analyses highlight the need for advances across a wide range of SBSP enabling capabilities

That's no obituary.  It's a shopping list.  ;)
« Last Edit: 01/22/2024 10:47 pm by Twark_Main »
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Offline Robotbeat

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Re: Space-based solar power for Earth
« Reply #539 on: 01/23/2024 12:16 am »
The Dream is Over?

https://spacenews.com/nasa-report-offers-pessimistic-take-on-space-based-solar-power/
Pretty terrible report. Unprofessional and technically incorrect.

The report is fine. The headline writing is (as always and by design) unnecessarily divisive and clickbait-y.

From the article:

Quote from: SpaceNews
The NASA study did address the baseline model's sensitivity to factors such as lower launch costs, use of electric propulsion and assuming a longer lifetime for components in GEO than the 10 years included in the baseline. Incorporating all of those factors reduces the electricity costs of the SBSP systems to levels similar to terrestrial renewable alternatives.

From the report:

Quote from: NASA
The following combination of revised assumptions yields SBSP solutions that are cost competitive with terrestrial alternatives, with lower GHG emissions:

    • lower launch cost: $50M per launch, or $500/kg; $425/kg with 15% block discount

    • electric propulsion orbital transfer from LEO to GEO

    • extended hardware lifetimes: 15 years

    • cheaper servicer and debris removal vehicles: $100M and $50M, respectively

    • efficient manufacturing at scale: learning curves of 85% and below

Our sensitivity analyses highlight the need for advances across a wide range of SBSP enabling capabilities

That's no obituary.  It's a shopping list.  ;)
No, the headlines are accurate. The report mischaracterizes current plans and uses absurdly pessimistic assumptions for the base case for 2050. And the lead author made clear during a presentation that NASA (well, NASA HQ decisionmakers) are not interested in SBSP and won’t pursue it. I’m not even very bullish on SBSP, but I was dismayed they didn’t even really try to make it work.

A small side note about a case where it actually does work is not sufficient to address those shortcomings.
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To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

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