I'm highly skeptical of the 60% efficiency figure being any sort of end-to-end metric. I suspect that was poorly phrased, and the receiver/rectifier was operating at 60% efficiency (which is reasonable for RF rectifiers), of power incident. But the vast majority of power loss is happening along the path before reaching the receiver.
Some ballpark numbers: 1km at 10GHz is ~110dB of path loss. Those look like feasibly 40dBi antennas at both ends. That still leaves -30dB link budget, i.e. 0.1% of energy reaching the target.
From the YouTube comments:
Video carefully avoids to state that the overall efficiency of the system is 1.8%. Input power was 91.2kW at the TX antenna, out of which 1.65kW was produced at the receiving side.
https://ieeexplore.ieee.org/mediastore_new/IEEE/content/medi...
I'm also not convinced that they're even out of Far-field. That looks like a roughly 5m dish, which at 10GHz is still in the radiating near field at 1km. I wouldn't be surprised if the main lobe is entirely incident on receiving aperture. That's a neat demo but it does not demonstrate truly radiating power between two distant points. They've essentially built a fancy a wireless cellphone charger.
60% is also almost certainly not total system. A portable antenna like that by itself, with no path loss or other losses, would likely have an aperture efficiency of about 60%. A planar patch antenna like the one used to receive would be similar.
Lasers have much higher "antenna" gain. How about using an IR laser to remotely heat a steam engine which runs a generator... I bet overall efficiency is at least an order of magnitude higher.
1km through the atmosphere is probably all you need to verify that the approach would work for Space Based Solar. I know the military is interested in that. Imagine being able to deploy energy anywhere on Earth and not have to setup a logistics chain to facilitate it. That's priceless. The economics for SBS don't really make sense to me, for domestic energy consumption. But economics are irrelevant if it enables you to project power deeper into hostile territory.
"Imagine being able to deploy energy anywhere on Earth and not have to setup a logistics chain to facilitate it."
Logistics is quite a complex beast and you mention "the military". Out of POL (Petrol, Oil, Lubricants) you now have one item nearly sorted - "petrol" ie power source. Your machines also need a few other things to work. Then there is food and water - your army's people need a power source too. Oh and they need a few things to throw at the opposition - munitions.
There's a major war being fought in Ukraine right now. Ukraine is bloody huge and it's all about logistics. Russia cannot possibly "win", where win is take and hold all of Ukraine. There was a huge armoured convoy headed for Kyiv and it stalled because it could not possibly have had enough of anything to run for more than a few days.
As my dad always used to say (Col. (Retd) RAOC): "An army marches on its stomach". That means that Russia may continue to commit acts of barbarism but it cannot possibly achieve its original aims. They have not got the legs.
That's not much comfort for the peoples of Ukraine suffering massive indignity and savage brutality, day after day.
If Space-Based Solar becomes a thing and starts being used in war zones, then it seems almost inevitable that warfare will move in to space... and that could lead to a catastrophic chain reaction of exploding satellites (aka the Kessler syndrome[1]) leading to an impenetrable field of space junk around Earth, which will prevent or at least greatly delay further use/exploration of space.
space based solar probably works fine outside the atmosphere, but any space based "power beaming" system would need to contend with the entire thickness of the atmosphere for path loss.
> Imagine being able to deploy energy anywhere on Earth and not have to setup a logistics chain to facilitate it.
theoretical setups for receiver arrays for space based solar power beamed over microwave are very large, if you're going to go to the trouble to erect a big receiving array somewhere in an empty piece of land, you might as well just build a large ground mount photovoltaic system based on commodity 72-cell monocrystalline Si 400W rated panels.
No, the ionosphere does weird things, including self-lensing at high enough power densities (frequency dependent too), so there's probably a bit more to test
I doubt it's never going to be practical enough to be useful, at all.
I might be wrong and someone can do the calculation to prove me wrong, but I don't think there is any way you're going to power an army or even a single regiment with that (or even more than a couple of toasters).
First, Low Earth Orbit is at least 160km above the Earth. You could do it at 100km but now you have to fight atmospheric drag on top of everything else and constantly need to readjust your orbit to avoid burning up.
Forming a beam tight enough that it stays focussed on your small target is the first challenge. Talk about fraction of a degree. You'll get much worse energy loss just there, because your target will always be smaller than the energy spot. If you have to build large targets, then there is a point where it would be more advantageous to just use solar panels on the ground.
Second, since you'd be using a low orbit, you'd still be in the dark at night, so no power for you.
Third, the lower the orbit, the faster the satellite is going to zoom past in the sky. You'd need a constellation of these to constantly reshape their beam to all their targets. As their distance from the target increases, the power received will also vary a lot. It also means the satellite will have to know the precise location of the target at all times. Might be workable for a static unit, but if you're talking drone/autonomous system, then they will need a way to transmit this information somewhere, very, very accurately too so the beam can find it.
It's not something you could deploy anywhere in an instant unless you have thousands of satellites covering all areas of interest.
The solar panel size you would need to ensure some decent minimum power received on Earth would be pretty big. Say you have a super efficient solar panel that can get you 30% efficiency, you'd get max of 300W/m2. So you would need very large arrays of panels just to get a few kW on the ground.
Now if instead of solar panels you want to beam up energy to bounce from the satellite back to the target, you'd double your problem space: need lots of large emitters that would need to target a constellation of fast moving satellites. Not great unless you know you can deploy them exactly where they are needed, which probably limits the use cases in foreign territories.
So, I'd say this will remain a niche application on Earth, where the size of the transmitting arrays depends on the distance to the target, and will probably never go beyond a trial in space if they manage to convince someone to get funding for it.
> Imagine being able to deploy energy anywhere on Earth and not have to setup a logistics chain to facilitate it.
I suppose. But on the other hand, let's say "anywhere on Earth" is a PCB inside an attacking enemy jet fighter. I haven't designed any PCBs for the military, so I don't know what their standards are, but I can say every low voltage circuit I've designed would not appreciate even 10W being dumped into any arbitrary net...
Isn't this more likely just the cover story for a space based death ray? Why pass energy to the ground for your troops, if you can just kill your targets from space?
Frankly, I'm a bit tired of these proposals transmit power by microwaves back to earth, especially so when frequencies such as 10GHz are either proposed or are used as test frequencies.
Do these people actually realize the likelihood of interference to RF and Microwave bands from potential intermodulation products that they'd cause? It would be an environmental disaster much worse than Musk's light-radiating satellites. I'd reckon that huge swathes of radio spectrum users includibg radio astronomers would be up in arms at such an outrageous proposal.
I've nothing in principle against such a proposal but it needs to be done in a part of the spectrum that will not cause interference to communications - and that will take considerable research and planning. For instance in the infrared or THz spectrum but even then we'd need to take great care for many reasons. (Recently, I've heard of experiments to detect neutrinos in the THz spectrum so that may also be ruled out).
I've strong thoughts about the inappropriate funding of this research in the 10GHz spectrum but I'll refrain from further comment for the moment.
Just let's say I've insufficient adjectives in my magazine to ensure a knockout.
> For context, 1.6 kW is about enough to power 1 home appliance: a dishwasher, refrigerator, or toaster.
Most (US) homes put outlets on a 15A breaker (sometimes 20A), which gives have 1.8 kW to play with. So this is less power than a typical home outlet.
> I think your A/C would be more - but I'm not certain
A/C definitely requires far more power—you have to deal a high peak load for motor start. Absolutely not happening with this setup.
The applications of this are rather curious, and definitely not for the any typical person. Probably defense, with a very short lead time, with the need for faster mobility?
> If you had Solar panels deliver this power [...]
Yes, definitely. And it can still be highly mobile: https://www.youtube.com/watch?v=VTiDklyEYaI (and once a setup is at a location, you could throw it on the back of a truck for some short-range transit. You'd just need to spread out the solar in each new place. FWIW, Solar and Microwave both have interesting yet different line of sight requirements.)
In the US this is almost exactly the maximum you'll find to not risk blowing fuses. Electric heaters are probably the most obvious continuous draw ones.
Those appliances nearly never have 100% duty cycle. It's important to note that this power can be transmitted when it is cloudy or nighttime and could potentially require less weight and setup.
I'm not saying line-of-sight transmission is a great solution, but this is an impressive engineering demonstration with some limited battlefield application.
Yeah, but only for fixed sites, or intermittently mobile sites.
Perovskites open the possibility of printing your solar cells on flexible films, so the panels can be unrolled like projector screens or greenhouse roofs, and rolled up again.[1]
10-15 kW of panels and suitable batteries would get you near 1.6 kW continuous.
This (microwave power beaming) is for battlefield applications, where mobility is primary.
The key point here is that it has a 60% efficient.
The question is, why is it important?
Well in the later part of Afghanistan war, significant time, money, and lives were spend shipping diesel around. If you can avoid that, you can save a shit tonne on logistics.
From the YouTube comments:
Video carefully avoids to state that the overall efficiency of the system is 1.8%. Input power was 91.2kW at the TX antenna, out of which 1.65kW was produced at the receiving side.
https://ieeexplore.ieee.org/mediastore_new/IEEE/content/medi...
based on terrain and other logistical challenges in Afghanistan I bet you $5 that sending a 20' ISO container packed with solar panel/ground mounting/advanced battery system would accomplish a whole lot more kWh per month than a "power over microwave" system from some central point to regional FOBs.
1.0km and 60% efficient is not very impressive.
various parts of the DoD are very interested in things like hydrogen fuel cell generators, more advanced/efficient diesel generators, prepackaged photovoltaic power systems, etc. they fund and buy prototypes all the time. they're well aware of the problem in transporting liquid fuel around.
So like all technological achievements, things will improve so the amount of power that can be transmitted will increase and the distance will increase.
At some point in the future it might become feasible to beam the energy down from a Low Earth Orbiting Satellite, which would transfer logistical costs into the preemptive side of accountancy instead of reactionary accountancy, but if they could do this from a LEO, then perhaps its also become a bit of a non ballistics weapon which may not be covered/restrained by current international agreements.
Whilst 60% is efficient and it's an excellent figure don't be fooled by the hype. I reckon what they've said in the the video is outrageous in that much of it is deceptive and misleading in the extreme.
Let's briefly look at some of the issues:
1. We need to carefully look at where that efficiency happens and then examine every place where loss of energy can occur, especially those that aren't stated. Let's take a brief look at some of the more obvious ones:
2. Conversion of energy into power suitable for generating microwaves at the transmitter. On earth, and assuming direct connection from the power grid, we need to consider losses in the power transformers and power supply or switching power supply, these days efficiency can be very high perhaps even 90% or more. As this equipment will be used primarily for military use, it would likely couple with diesel motor/generators suitable for use in the field, if so then I'd be surprised if the combo was more than 35% efficient at best (someone who knows up-to-date specs on these units correct me if necessary). If the unit is ultimately used in space then the conversion efficiency of its solar panels must be taken into account. As far as I'm aware no solar cell has ever reached 60% or over—even the best GaAs ones (from memory, this 60% figure would exceed theoretical 'quantum efficiency' figures).
3. Assuming no other loss at the power supply end (such as offline batteries, which are a distinct possibility in the field in military use) then we have to take the efficiency of microwave sources into account. I've not up-to-date figures on the latest 10GHz generators so I'd be guessing these figures, suffice to say that until recently generating microwaves was comparatively inefficient (unless magnetrons are used and they have messy and inconvenient HV power requirements).
4. Next comes the waveguides, antenna horn and focusing unit and the antenna (these, if optimized, could be quite efficient).
5. Now comes the path loss between transmitter and receiver. Exactly what that is remains to be seen. I've worked with microwaves and I can assure you that it is dead easy for the antennas be slightly off alignment and you receive almost no signal. For this scheme to work efficiently there would have to be some kind of efficient control system (servo/feedback, etc.) that keeps the TX and RX antennas in precise alignment. Moreover, at 10GHz a storm or a heavy rainfall downpour could kill the circuit altogether (I've actually seen this happen to the extent that only over a path of a half dozens or so miles that not only the fade margin, normally >30dB, on microwave links was exceeded but also the signals fell so low that the circuit was actually lost. Moreover, for reliability, two microwave links were run in parallel and both circuits failed for some 5 or 6 minutes until the rain cleared).
5a. Now the killer bit: as mentioned, commercial microwave links have huge fade margins to protect against variations in atmospherics and objects—planes etc., blocking the way. These links have what is known as AGC—Automatic Gain Control—to keep signals level. That cannot apply in power transmission; in practice, even a temporary path loss of 6 - 12dB (which could easily be expected) would essentially be catastrophic, that is effectively kill all received power at the receiver (they'd want to have pretty good battery backup and often in military operations that's not always possible, extra weight etc.)!
6. Now comes the horror bit (this could also apply to the generation of the microwaves at the transmission end). That is, the rectification of microwaves at the receiving end will generate considerable RF hash and noise. To be efficient, the diodes rectifying the incoming RF would have to have an f(t) of well in excess of that frequency and heaven help anyone operating a microwave receiver within many miles of the receiver (radio astronomers for instance). As the rectification diodes have to be near or on the antenna for efficiency, screening them to stop them radiating locally generated crap everywhere would be a near impossibility—remember your Fourier lessons, you're chopping sine waves up to get DC and that means harmonics—the more efficient the process the more noise generated! Any attempt to filter the hash and noise generated by the diodes would further reduce efficiency. This is the sort of scenario that spectrum managers and planners have nightmares about.
Whilst this isn't quite the same, here's an example that illustrates what can happen. I had an Amateur Radio friend who used to do moonbounce on 432MHz and he'd often complain to me that various LED lights (i.e.: diodes) in his neighbors' possession would interfere with his incoming reception to the point where on occasions he'd have to abort the exercise. Now keep this in mind, he raised this matter with me over 10 years ago when LED lighting was far less common that it is today.
Face the facts, much of this pronouncement is little more than spin. Likely the principle reason the video was made was to keep their funding masters happy. Little of it will fool the technical cognoscenti.
Also keep in mind that all 'niceties' are off during military conflicts, interference to services other than to the military's own communications equipment would likely be irrelevant (as we saw in WWII, the military was the principal user of spectrum, what it wanted it got).
As for a permanent space port 'broadcasting' power to earth the idea is ludicrous—that is, until thousands of questions about likely problems have been asked and that genuine engineering solutions for them are actually found.
Seems to me their PR department has taken a leaf from the wordbook used by social media and politicians—that's the one that redefines the word 'fact'!
Is there some reason that this doesn't scale up to however high you want if you add more input power? I would have thought that 60% efficiency would be the interesting figure, not 1.6 kW.
I wonder if you could use this for "aerial refueling" of an electric drone - might be a cheaper way to make small long-endurance vehicles than trying to stick ICEs in them (though it has the downside of "tethering" them to a ground station).
google "microwave atmospheric path loss calculation" or "microwave free space path loss" - standard calculations for point to point microwave telecom systems, you lose quite a lot to the molecules in the air. probably would work a whole lot better in a vacuum.
Is there any chance that this could ever be reliable enough to act as the primary power source for a plane? (In other words, you'd keep just enough fuel/battery onboard for emergency landings, and otherwise rely almost entirely on space microwaves.)
If so, is there any possibility that it could also provide sufficient throughput to handle supersonic flight?
What if we spent most of the journey at a very high altitude, or even in/near LEO?
I wonder about whether a big enough orbiting phased array, with all the elements carefully quantum-entangled, could achieve much better power delivery to a small receiver.
In this scenario, the phased array transmitters would be placed randomly in a swarm. The receiver would broadcast a pilot signal, and they would all adjust their phase by the received pilot-signal phase and, implicitly, their position in the swarm. (Maybe the pilot signal is at exactly half or twice the transmit frequency, and a maser, so all its photons are entangled.)
I don't know how you arrange to quantum-entangle the transmitting elements and their emitted photons to the pilot signal and (this) to one another. The goal is for all their quantum amplitudes to interfere constructively only at the rectenna, and so deliver all of their energy there. Is there any necessary or enforcible relationship between the photon wave phase and its quantum amplitude?
For a decoupled swarm to stay together, each would need to be in a slightly different almost-circular orbit, continually milling about a common center. Alternatively, they could have hair-thin fibers tying them to near neighbors, and all orbit as a unit.
Department of Energy studied the use of phased arrays to beam power (http://spaceflighthistory.blogspot.com/2016/12/energy-from-s...). The use of a pilot signal was useful because it prevented any 'death ray' scenarios. The transmitter would only be able to beam power to a receiver, even if it was knocked off target.
I am not sure what the benefit of a small receiver would be for power transmission. The DoE system used the same 2.45 GHz frequency as a microwave oven, so the receiver was more like chicken wire than the receivers we are familiar with. They would have been very large to prevent overflying aircraft or birds from being fried by the transmission, and could maybe be placed on pylons over otherwise useful land.
42% is RF to DC conversion efficiency, absolutely no way those omni antennas are end to end dc-rf-dc 42% wireless transmission efficiency at any distance, its going to be many orders of magnitude worse.
Had to do a double take for a minute, as in my days in the Army, we could max out our AN/TRC-170 on troposcatter mode at 2.0 kW, with a substantial range on a good atmosphere day.
The use case here, however, is incredibly different. We'd typically be towing 2x 10 kW diesel generators with us, so this is certainly an interesting POC to follow.
> The frequency was chosen because it was not only able to beam even in heavy rain with a loss of power of under five percent, it's also safe to use under international standards in the presence of birds, animals, and people.
What frequency is this specifically? I'm curious to know how people-safe it is in practice.
The headline makes me wonder - what ever became of Tesla's dream of an building a global atmospheric electric power network? Is it for commercial, physical or technical reasons that the idea seems to have been given up?
The only way this is in any way interesting is as a 1950s style death ray, and even then, it's only enough to warm porridge at that distance. A close-quarters vehicle mounted version at 100m might be a different proposition.
Wow, 60% is way higher efficiency than I thought these systems were getting. I was fully expecting “using 16kw of power 1.6kw was successfully transmitted”
[+] [-] mNovak|4 years ago|reply
Some ballpark numbers: 1km at 10GHz is ~110dB of path loss. Those look like feasibly 40dBi antennas at both ends. That still leaves -30dB link budget, i.e. 0.1% of energy reaching the target.
[+] [-] toephu2|4 years ago|reply
[+] [-] apcragg|4 years ago|reply
60% is also almost certainly not total system. A portable antenna like that by itself, with no path loss or other losses, would likely have an aperture efficiency of about 60%. A planar patch antenna like the one used to receive would be similar.
[+] [-] jhallenworld|4 years ago|reply
[+] [-] pharos92|3 years ago|reply
[+] [-] coenhyde|4 years ago|reply
[+] [-] gerdesj|4 years ago|reply
Logistics is quite a complex beast and you mention "the military". Out of POL (Petrol, Oil, Lubricants) you now have one item nearly sorted - "petrol" ie power source. Your machines also need a few other things to work. Then there is food and water - your army's people need a power source too. Oh and they need a few things to throw at the opposition - munitions.
There's a major war being fought in Ukraine right now. Ukraine is bloody huge and it's all about logistics. Russia cannot possibly "win", where win is take and hold all of Ukraine. There was a huge armoured convoy headed for Kyiv and it stalled because it could not possibly have had enough of anything to run for more than a few days.
As my dad always used to say (Col. (Retd) RAOC): "An army marches on its stomach". That means that Russia may continue to commit acts of barbarism but it cannot possibly achieve its original aims. They have not got the legs.
That's not much comfort for the peoples of Ukraine suffering massive indignity and savage brutality, day after day.
[+] [-] pmoriarty|4 years ago|reply
[1] - https://en.wikipedia.org/wiki/Kessler_syndrome
[+] [-] walrus01|4 years ago|reply
> Imagine being able to deploy energy anywhere on Earth and not have to setup a logistics chain to facilitate it.
theoretical setups for receiver arrays for space based solar power beamed over microwave are very large, if you're going to go to the trouble to erect a big receiving array somewhere in an empty piece of land, you might as well just build a large ground mount photovoltaic system based on commodity 72-cell monocrystalline Si 400W rated panels.
[+] [-] chris_va|4 years ago|reply
[+] [-] ghostly_s|4 years ago|reply
How so? Wouldn't a space-based-solar facility need to transmit through the full height of the atmosphere which is much more than 1km?
[+] [-] Renaud|4 years ago|reply
I might be wrong and someone can do the calculation to prove me wrong, but I don't think there is any way you're going to power an army or even a single regiment with that (or even more than a couple of toasters).
First, Low Earth Orbit is at least 160km above the Earth. You could do it at 100km but now you have to fight atmospheric drag on top of everything else and constantly need to readjust your orbit to avoid burning up.
Forming a beam tight enough that it stays focussed on your small target is the first challenge. Talk about fraction of a degree. You'll get much worse energy loss just there, because your target will always be smaller than the energy spot. If you have to build large targets, then there is a point where it would be more advantageous to just use solar panels on the ground.
Second, since you'd be using a low orbit, you'd still be in the dark at night, so no power for you.
Third, the lower the orbit, the faster the satellite is going to zoom past in the sky. You'd need a constellation of these to constantly reshape their beam to all their targets. As their distance from the target increases, the power received will also vary a lot. It also means the satellite will have to know the precise location of the target at all times. Might be workable for a static unit, but if you're talking drone/autonomous system, then they will need a way to transmit this information somewhere, very, very accurately too so the beam can find it.
It's not something you could deploy anywhere in an instant unless you have thousands of satellites covering all areas of interest.
The solar panel size you would need to ensure some decent minimum power received on Earth would be pretty big. Say you have a super efficient solar panel that can get you 30% efficiency, you'd get max of 300W/m2. So you would need very large arrays of panels just to get a few kW on the ground.
Now if instead of solar panels you want to beam up energy to bounce from the satellite back to the target, you'd double your problem space: need lots of large emitters that would need to target a constellation of fast moving satellites. Not great unless you know you can deploy them exactly where they are needed, which probably limits the use cases in foreign territories.
So, I'd say this will remain a niche application on Earth, where the size of the transmitting arrays depends on the distance to the target, and will probably never go beyond a trial in space if they manage to convince someone to get funding for it.
[+] [-] sillysaurusx|4 years ago|reply
1.6kW deployed to any area in the world. I’m not sure how to visualize that, or what the implications are.
Could this power a drone indefinitely with no need to land?
[+] [-] egsmi0|4 years ago|reply
I suppose. But on the other hand, let's say "anywhere on Earth" is a PCB inside an attacking enemy jet fighter. I haven't designed any PCBs for the military, so I don't know what their standards are, but I can say every low voltage circuit I've designed would not appreciate even 10W being dumped into any arbitrary net...
[+] [-] ta8645|4 years ago|reply
[+] [-] hilbert42|4 years ago|reply
Do these people actually realize the likelihood of interference to RF and Microwave bands from potential intermodulation products that they'd cause? It would be an environmental disaster much worse than Musk's light-radiating satellites. I'd reckon that huge swathes of radio spectrum users includibg radio astronomers would be up in arms at such an outrageous proposal.
I've nothing in principle against such a proposal but it needs to be done in a part of the spectrum that will not cause interference to communications - and that will take considerable research and planning. For instance in the infrared or THz spectrum but even then we'd need to take great care for many reasons. (Recently, I've heard of experiments to detect neutrinos in the THz spectrum so that may also be ruled out).
I've strong thoughts about the inappropriate funding of this research in the 10GHz spectrum but I'll refrain from further comment for the moment.
Just let's say I've insufficient adjectives in my magazine to ensure a knockout.
[+] [-] geoduck14|4 years ago|reply
I think your A/C would be more - but I'm not certain
If you had Solar panels deliver this power, you could get similar power if you spent ~$1.5k on a panel 6.5 ft X 16 ft
[+] [-] cptcobalt|4 years ago|reply
Most (US) homes put outlets on a 15A breaker (sometimes 20A), which gives have 1.8 kW to play with. So this is less power than a typical home outlet.
> I think your A/C would be more - but I'm not certain
A/C definitely requires far more power—you have to deal a high peak load for motor start. Absolutely not happening with this setup.
The applications of this are rather curious, and definitely not for the any typical person. Probably defense, with a very short lead time, with the need for faster mobility?
> If you had Solar panels deliver this power [...]
Yes, definitely. And it can still be highly mobile: https://www.youtube.com/watch?v=VTiDklyEYaI (and once a setup is at a location, you could throw it on the back of a truck for some short-range transit. You'd just need to spread out the solar in each new place. FWIW, Solar and Microwave both have interesting yet different line of sight requirements.)
[+] [-] tapland|4 years ago|reply
[+] [-] willis936|4 years ago|reply
I'm not saying line-of-sight transmission is a great solution, but this is an impressive engineering demonstration with some limited battlefield application.
[+] [-] tuatoru|4 years ago|reply
Perovskites open the possibility of printing your solar cells on flexible films, so the panels can be unrolled like projector screens or greenhouse roofs, and rolled up again.[1]
10-15 kW of panels and suitable batteries would get you near 1.6 kW continuous.
This (microwave power beaming) is for battlefield applications, where mobility is primary.
1. Several groups are developing these. For example in Australia, https://www.csiro.au/en/research/technology-space/energy/Pho...
[+] [-] Neil44|4 years ago|reply
[+] [-] closeparen|4 years ago|reply
[+] [-] KaiserPro|4 years ago|reply
The question is, why is it important?
Well in the later part of Afghanistan war, significant time, money, and lives were spend shipping diesel around. If you can avoid that, you can save a shit tonne on logistics.
[+] [-] toephu2|4 years ago|reply
From the YouTube comments: Video carefully avoids to state that the overall efficiency of the system is 1.8%. Input power was 91.2kW at the TX antenna, out of which 1.65kW was produced at the receiving side. https://ieeexplore.ieee.org/mediastore_new/IEEE/content/medi...
[+] [-] walrus01|4 years ago|reply
1.0km and 60% efficient is not very impressive.
various parts of the DoD are very interested in things like hydrogen fuel cell generators, more advanced/efficient diesel generators, prepackaged photovoltaic power systems, etc. they fund and buy prototypes all the time. they're well aware of the problem in transporting liquid fuel around.
[+] [-] Terry_Roll|4 years ago|reply
At some point in the future it might become feasible to beam the energy down from a Low Earth Orbiting Satellite, which would transfer logistical costs into the preemptive side of accountancy instead of reactionary accountancy, but if they could do this from a LEO, then perhaps its also become a bit of a non ballistics weapon which may not be covered/restrained by current international agreements.
[+] [-] powersnail|4 years ago|reply
[+] [-] hilbert42|4 years ago|reply
Let's briefly look at some of the issues:
1. We need to carefully look at where that efficiency happens and then examine every place where loss of energy can occur, especially those that aren't stated. Let's take a brief look at some of the more obvious ones:
2. Conversion of energy into power suitable for generating microwaves at the transmitter. On earth, and assuming direct connection from the power grid, we need to consider losses in the power transformers and power supply or switching power supply, these days efficiency can be very high perhaps even 90% or more. As this equipment will be used primarily for military use, it would likely couple with diesel motor/generators suitable for use in the field, if so then I'd be surprised if the combo was more than 35% efficient at best (someone who knows up-to-date specs on these units correct me if necessary). If the unit is ultimately used in space then the conversion efficiency of its solar panels must be taken into account. As far as I'm aware no solar cell has ever reached 60% or over—even the best GaAs ones (from memory, this 60% figure would exceed theoretical 'quantum efficiency' figures).
3. Assuming no other loss at the power supply end (such as offline batteries, which are a distinct possibility in the field in military use) then we have to take the efficiency of microwave sources into account. I've not up-to-date figures on the latest 10GHz generators so I'd be guessing these figures, suffice to say that until recently generating microwaves was comparatively inefficient (unless magnetrons are used and they have messy and inconvenient HV power requirements).
4. Next comes the waveguides, antenna horn and focusing unit and the antenna (these, if optimized, could be quite efficient).
5. Now comes the path loss between transmitter and receiver. Exactly what that is remains to be seen. I've worked with microwaves and I can assure you that it is dead easy for the antennas be slightly off alignment and you receive almost no signal. For this scheme to work efficiently there would have to be some kind of efficient control system (servo/feedback, etc.) that keeps the TX and RX antennas in precise alignment. Moreover, at 10GHz a storm or a heavy rainfall downpour could kill the circuit altogether (I've actually seen this happen to the extent that only over a path of a half dozens or so miles that not only the fade margin, normally >30dB, on microwave links was exceeded but also the signals fell so low that the circuit was actually lost. Moreover, for reliability, two microwave links were run in parallel and both circuits failed for some 5 or 6 minutes until the rain cleared).
5a. Now the killer bit: as mentioned, commercial microwave links have huge fade margins to protect against variations in atmospherics and objects—planes etc., blocking the way. These links have what is known as AGC—Automatic Gain Control—to keep signals level. That cannot apply in power transmission; in practice, even a temporary path loss of 6 - 12dB (which could easily be expected) would essentially be catastrophic, that is effectively kill all received power at the receiver (they'd want to have pretty good battery backup and often in military operations that's not always possible, extra weight etc.)!
6. Now comes the horror bit (this could also apply to the generation of the microwaves at the transmission end). That is, the rectification of microwaves at the receiving end will generate considerable RF hash and noise. To be efficient, the diodes rectifying the incoming RF would have to have an f(t) of well in excess of that frequency and heaven help anyone operating a microwave receiver within many miles of the receiver (radio astronomers for instance). As the rectification diodes have to be near or on the antenna for efficiency, screening them to stop them radiating locally generated crap everywhere would be a near impossibility—remember your Fourier lessons, you're chopping sine waves up to get DC and that means harmonics—the more efficient the process the more noise generated! Any attempt to filter the hash and noise generated by the diodes would further reduce efficiency. This is the sort of scenario that spectrum managers and planners have nightmares about.
Whilst this isn't quite the same, here's an example that illustrates what can happen. I had an Amateur Radio friend who used to do moonbounce on 432MHz and he'd often complain to me that various LED lights (i.e.: diodes) in his neighbors' possession would interfere with his incoming reception to the point where on occasions he'd have to abort the exercise. Now keep this in mind, he raised this matter with me over 10 years ago when LED lighting was far less common that it is today.
Face the facts, much of this pronouncement is little more than spin. Likely the principle reason the video was made was to keep their funding masters happy. Little of it will fool the technical cognoscenti.
Also keep in mind that all 'niceties' are off during military conflicts, interference to services other than to the military's own communications equipment would likely be irrelevant (as we saw in WWII, the military was the principal user of spectrum, what it wanted it got).
As for a permanent space port 'broadcasting' power to earth the idea is ludicrous—that is, until thousands of questions about likely problems have been asked and that genuine engineering solutions for them are actually found.
Seems to me their PR department has taken a leaf from the wordbook used by social media and politicians—that's the one that redefines the word 'fact'!
[+] [-] gpm|4 years ago|reply
I wonder if you could use this for "aerial refueling" of an electric drone - might be a cheaper way to make small long-endurance vehicles than trying to stick ICEs in them (though it has the downside of "tethering" them to a ground station).
[+] [-] walrus01|4 years ago|reply
[+] [-] buu700|4 years ago|reply
If so, is there any possibility that it could also provide sufficient throughput to handle supersonic flight?
What if we spent most of the journey at a very high altitude, or even in/near LEO?
[+] [-] zw123456|4 years ago|reply
just look at the equation, physics don't lie.
mic drop
[+] [-] ncmncm|4 years ago|reply
In this scenario, the phased array transmitters would be placed randomly in a swarm. The receiver would broadcast a pilot signal, and they would all adjust their phase by the received pilot-signal phase and, implicitly, their position in the swarm. (Maybe the pilot signal is at exactly half or twice the transmit frequency, and a maser, so all its photons are entangled.)
I don't know how you arrange to quantum-entangle the transmitting elements and their emitted photons to the pilot signal and (this) to one another. The goal is for all their quantum amplitudes to interfere constructively only at the rectenna, and so deliver all of their energy there. Is there any necessary or enforcible relationship between the photon wave phase and its quantum amplitude?
For a decoupled swarm to stay together, each would need to be in a slightly different almost-circular orbit, continually milling about a common center. Alternatively, they could have hair-thin fibers tying them to near neighbors, and all orbit as a unit.
[+] [-] shadowofneptune|4 years ago|reply
I am not sure what the benefit of a small receiver would be for power transmission. The DoE system used the same 2.45 GHz frequency as a microwave oven, so the receiver was more like chicken wire than the receivers we are familiar with. They would have been very large to prevent overflying aircraft or birds from being fried by the transmission, and could maybe be placed on pylons over otherwise useful land.
[+] [-] jleyank|4 years ago|reply
[+] [-] R0b0t1|4 years ago|reply
To do this they probably beamed far more than 1.6kW. You need to heat the vapor in the middle and either go through it or move it out of the way.
Fun consequence of this, you can disperse clouds by pointing microwaves up. It doesn't take a massive amount of power either, but scales with power.
[+] [-] pfdietz|4 years ago|reply
[+] [-] nreilly|4 years ago|reply
[1] https://www.transferfi.com
[2] https://www.transferfi.com/s/TFI_Sense_WPN_Spec.pdf
[+] [-] SigmundA|4 years ago|reply
[+] [-] awslattery|4 years ago|reply
The use case here, however, is incredibly different. We'd typically be towing 2x 10 kW diesel generators with us, so this is certainly an interesting POC to follow.
[+] [-] kibwen|4 years ago|reply
What frequency is this specifically? I'm curious to know how people-safe it is in practice.
[+] [-] belter|3 years ago|reply
"5G as a wireless power grid": https://www.nature.com/articles/s41598-020-79500-x
[+] [-] nayuki|4 years ago|reply
[+] [-] t_mann|3 years ago|reply
[+] [-] verytrivial|3 years ago|reply
[+] [-] olliej|4 years ago|reply
[+] [-] stuckkeys|4 years ago|reply
[+] [-] cwillu|4 years ago|reply
[+] [-] KSPAtlas|4 years ago|reply