Power "Beaming"

[Uber_the_Goober]

From here - page 3, first paragraph:

"Until recently the high cost and low efficiency of lasers suitable for power beaming have been
barriers to the practical application of the technology. However, with recent advances, laser diodes are becoming powerful, efficient, and inexpensive enough to make the commercial development of laser power beaming feasible. In 2007, the Pentagon released a study recommending
the development of space-based power systems using laser power beaming as one option for
transmission*
. In that study, the Pentagon found that, if placed correctly, space power systems
could provide enough solar energy in a single year equal to all known oil reserves on Earth, provide power for global U.S. military operations and deliver energy to disaster areas and developing
nations. "

Sorry for the copy/paste, but this bit caught my attention. I haven’t read through the entire .pdf, but my very first thought was Fallout: New Vegas! After that I thought, could this seriously work as an alternative to fossil fuels? Giant focused mirror arrays focusing sunlight ala a magnifying glass down to solar plants on earth?

Would this improve their efficiency?

The .pdf is about an UAV that has the batteries recharged via frickin’ laser beams. Pretty cool, but I wonder how it would scale. Anyway, that’s beside my point.

Any thoughts?

[DrFidelius]

One misalignment of the European grid down-link could cause the Cooking of Provincial France.

(I’ll go away now until someone with actual knowledge appears.)

[Uber_the_Goober]

I thought of that too…don’t know how you’d actually make that part safe.

Let’s hand-wave that away for now. Good on you for bringing that up right from the start though

[si_blakely]

We already have a problem with global warming, and you want to add energy into the atmosphere via massive amounts of additional solar energy. And what happens on a rainy day?

Basically, the atmospheric losses would reduce the utility of such a system. Much more efficient to convert the solar energy in space, and then get it to earth via a less-lossy medium (microwave, maybe, or an tower/cable at a rotational axis point.

[Dewey_Finn]

The idea of power beaming reminds me of some of the concepts of Gerard K O’Neill, who suggested large orbiting colonies, along with a solar power satellite that would beam the energy produced to a collector array on Earth. See here for more detail.

[Gray_Ghost]

I had thought that Solar Power Satellite energy transmission would be via microwave, not lasers operating at other wavelengths. Huh, the more you know… Anyway, here’s a 1992 IEEE paper on the basics of microwave energy transmission from one of these SPSs. (.pdf) He mentions a conversion efficiency of 54%, demonstrated on a benchtop basis. The paper also goes into environmental issues with beaming high energy microwaves down to a rectenna.

Doubtlessly, someone like Stranger on A Train can come in and expand on this. I want to say we’ve had some recent threads on the idea here.

I love the idea of it, but I don’t think the economics currently make sense. It costs a lot to get mass out of our gravity well. Not to mention that we wholly lack the kind of construction experience in vacuum—putting together the ISS just isn’t the same thing as building the satellite in situ—to make something like a SPS work.

[Uber_the_Goober]

@si_blakely

We already have a problem with global warming, and you want to add energy into the atmosphere via massive amounts of additional solar energy. And what happens on a rainy day?

Basically, the atmospheric losses would reduce the utility of such a system. Much more efficient to convert the solar energy in space, and then get it to earth via a less-lossy medium (microwave, maybe, or an tower/cable at a rotational axis point.

Ok, picker of nits. I concede your point - just pointing the additional solar energy at the earth may not be good for global warming.

But wouldn’t we be capturing that energy and converting it via the solar plant? The “atmospheric losses” - would this literally be energy converted to heat (from the magnified light striking suspended particles in the air) in the atmosphere? And would that heat transfer actually have an impact on the global temperature?

And converting the light energy to microwaves - and then pointing them at a plant on earth - isn’t that a SIM City power plant option? Didn’t they have a tendency to fail catastrophically? Not that SIM City is a good working model of the real world or anything.

[Uber_the_Goober]

@Gray_Ghost

I love the idea of it, but I don’t think the economics currently make sense. It costs a lot to get mass out of our gravity well. Not to mention that we wholly lack the kind of construction experience in vacuum—putting together the ISS just isn’t the same thing as building the satellite in situ—to make something like a SPS work.

Man’s ingenuity will improve exponentially when pressed against the wall of “No more oil”. That’s a far way off, granted, but it’ll happen eventually.

I don’t think lack of construction experience is a factor to consider in this instance. A hurdle to overcome, not a barrier outright.

[Dewey_Finn]

@Gray_Ghost

I had thought that Solar Power Satellite energy transmission would be via microwave, not lasers operating at other wavelengths. Huh, the more you know… Anyway, here’s a 1992 IEEE paper on the basics of microwave energy transmission from one of these SPSs. (.pdf) He mentions a conversion efficiency of 54%, demonstrated on a benchtop basis. The paper also goes into environmental issues with beaming high energy microwaves down to a rectenna.

I read a lot about Dr O’Neill’s ideas in high school and I believe his idea was for microwave transmission.

[Gray_Ghost]

@Dewey_Finn

I read a lot about Dr O’Neill’s ideas in high school and I believe his idea was for microwave transmission.

Me too. Another guy who took the idea and played around with it was Jerry Pournelle, in his A Step Farther Out. And then there’s always the dancing on the glacier scene from Fallen Angels…

Off-topic of SPS’s, but what do you think of Elon Musk basically re-badging O’Neill’s ‘maglev in vacuum tubes’ idea?

[si_blakely]

@Uber_the_Goober

But wouldn’t we be capturing that energy and converting it via the solar plant? The “atmospheric losses” - would this literally be energy converted to heat (from the magnified light striking suspended particles in the air) in the atmosphere? And would that heat transfer actually have an impact on the global temperature?

There will be a path taken by the light from the collector to the surface collector. There will be an increase in the temperature in that column, due to simple thermal conversion. The air will get warm, causing a thermal updraft sucking in air from round the collector (and laying dust on the mirrors, probably). The thermal bloom and moving air will distort the beam (making it hard to aim) and the weather patterns round the collectors will be impacted. If there is a cloud, then they will absorb and reflect the light before it gets to the collector, and you will get massive distortions of the local weather as warm moisture laden air rises, cools and condenses as rain and hail.

[Smeghead]

@si_blakely

We already have a problem with global warming, and you want to add energy into the atmosphere via massive amounts of additional solar energy. And what happens on a rainy day?

Replacing the combustion of fossil fuels for energy production with a completely carbon-free energy source would be a massive boon to the fight against global warming. The increased amount of energy entering the Earth’s atmosphere would be tiny compared to the benefit of not having all that CO2 trapping heat in.

[AdamF]

From the aforementioned Pentagon study, they were trying to solve this problem:

When all indirect and support costs are included, it is estimated that the DoD currently spends over $1 per kilowatt hour for electrical power delivered to troops in forward military bases in war regions.

And their finding was fairly unsuprising:

The SBSP Study Group found that even with the DoD as an anchor tenant customer at a price of $1-2 per kilowatt hour for 5-50 megawatts continuous power for the warfighter, when considering the risks of implementing a new unproven space technology and other major business risks, the business case for SBSP still does not appear to close in 2007 with current capabilities (primarily launch costs).

And specifically in regards to power transmission:

Visible and infrared ranges, because of their much shorter wavelength, have the advantage of much smaller apertures, but today have lower efficiencies both in generation and reception, are less mature at high power levels, may have eye-safety concerns, and may be unacceptable to the public regardless of the density of the beam because of negative associations Light Amplication by Simulated Emission of Radiation may have with the general public. Nevertheless, the ability to achieve first power at much lower weights, and to beam it to much smaller receivers deserves additional study and attention.

The more typical design for Space Power Satellites has been the 2.4 or 5.8 GHz ranges where transmission and coupling is favorable. The disadvantage of this approach is the unforgiving physics of microwave power transmission, which requires extremely large apertures, and therefore large on-orbit weights, to mitigate the beam divergence. This minimum aperture to ensure a sufficiently small spot size and coupling efficiency is true regardless of the amount of power transmitted, and therefore scales poorly for small amounts of power.