[HN Gopher] Practical Power Beaming Gets Real
___________________________________________________________________
Practical Power Beaming Gets Real
Author : gmays
Score : 48 points
Date : 2022-05-26 18:15 UTC (4 hours ago)
(HTM) web link (spectrum.ieee.org)
(TXT) w3m dump (spectrum.ieee.org)
| h2odragon wrote:
| Cool stuff! I wonder what will be left after the bitter bites of
| reality for consumer products: consider that we still have actual
| engineering troubles with things like aluminum in house wiring,
| which we've been doing for >100 years now.
|
| "battery free cordless" desktop peripherals will be _nice_ , tho.
|
| Wonder what bandwidths the data overlays will be. If you're
| steering and modulating a beam for power, why not use it for
| signal at the same time?
| jotm wrote:
| Wifi is practical, too. But I prefer wired Ethernet whenever
| possible, even if it's hard.
| SemanticStrengh wrote:
| How much energy loss has the system? And what complexity curve
| fit its efficiency over length?
| c54 wrote:
| One of the big problems with the current power grid is
| transmission loss, resistance in electrical wires over long
| distances eat ~5% of the generated power. This makes it
| infeasible for example to have large solar installations in the
| American southwest transmit power to the Northeast.
|
| Does anyone know about theoretical minimum losses from this kind
| of power transmission?
| Retric wrote:
| Grid losses are generally well under 5% and many of them are
| reasonably independent of distance. Aka a town next to a
| nuclear power plant needs to step down voltage multiple times
| and that has associated losses even if power is only moving a
| few miles.
|
| So what matters isn't total losses but losses specifically
| related to the distance traveled.
| photochemsyn wrote:
| The article makes references to atmospheric conditions:
|
| > "Because of limitations imposed by the atmosphere on the
| effective transmission of energy within certain sections of the
| electromagnetic spectrum, researchers have focused on
| microwave, millimeter-wave, and optical frequencies."
|
| It seems likely that water vapor is the big issue, and that's
| pretty variable across a lot of regions, and fog and cloud
| formation would be an additional issue. Hence, this is probably
| going to be more for relatively short-distance applications
| (the demo they discuss is a few hundred meters) on Earth.
| However, in space-to-space applications this doesn't seem to be
| an issue. Maybe something like solar satellites in orbit around
| the Moon beaming power to Moonbase would be an option.
|
| For really long-distance energy transport on Earth, the
| transport of stored chemical or nuclear energy (hydrocarbons or
| uranium basically, or maybe iron?) are really the only
| plausible options.
| sandworm101 wrote:
| That depends. Is it cloudy? Has a bird flown through the beam
| path? These are lasers. Everything that can interfere or block
| a laser will interfere with this tech.
| kortex wrote:
| The article mentions a virtual optical fence that cuts the
| beam if anything impinges, so no roast pigeon with this
| system. Anything which the beam could couple to, haze, smog,
| etc, would definitely reduce efficiency for sure.
| lordnacho wrote:
| 5% per what distance?
| marcosdumay wrote:
| Yeah, you are not going to fix resistance losses by moving into
| wireless power transmission.
|
| But keep in mind that the transmission losses are at ~5%
| because that's a level that people consider economical. They
| could be higher, or lower. The losses also tend to be around
| that value for any power grid you look, it doesn't matter if
| it's a minuscule country or a continental one, people just
| improve their grid until it gets there.
| wcoenen wrote:
| > _resistance in electrical wires over long distances eat ~5%
| of the generated power. This makes it infeasible..._
|
| Electricity price differences throughout the USA[1] are much
| more than 5%, so a 5% loss does not (in itself) seem to make
| long distance transmission uneconomical.
|
| [1] https://www.energybot.com/electricity-rates-by-state.html
| db65edfc7996 wrote:
| Wait until he hears about the efficiency of an ICE. 5% losses
| for fixed infrastructure feels like not a big deal?
| droopyEyelids wrote:
| a current induction charger for a phone, that operates over
| about a millimeter of distance, is at best 70% as efficient as
| charging with a wire.
|
| The fact that this article omitted all details about
| efficiency, and omitted any numbers that we could use to
| calculate it, say it's probably not beating the standard
| induction charger's efficiency.
|
| I think this technology is more in the stage of "It's possible
| to do this!" rather than "it's practical to do this"
| hinkley wrote:
| Word games are common in advertising and that has spread to
| journalism as well.
|
| "it's impractical to shop for a house in a war zone" and
| "it's impractical to buy a house in San Francisco" are two
| very different definitions of "practical".
|
| It feels like that's what's going on here.
| kurthr wrote:
| Very roughly minimum loss is 50% for a far-field optical or RF
| system (near-field can be better), excluding the energy cost of
| building the transmitter/receiver systems themselves. Losses
| due to impedance mismatch make this difficult to improve. The
| most efficient light emitters are ~50% and the best optical
| photo-voltaics are also ~40%, which would get you to an 80%
| loss, ignoring atmospheric losses.
| jhgb wrote:
| > The most efficient light emitters are ~50% and the best
| optical photo-voltaics are also ~40%, which would get you to
| an 80% loss, ignoring atmospheric losses.
|
| Unless you have matched emitters and PV cells? For example
| [1] cites 53.4% conversion efficiency for monochromatic
| light. (The 40% figure was presumably sunlight conversion
| efficiency?)
|
| [1] https://ieeexplore.ieee.org/document/4922910
| sandworm101 wrote:
| Note that in all the pictures the receiver seems to be on a tower
| or at least above the emitter. No doubt this is a safety
| consideration. Nobody would dare test one of these things
| horizontally. And good luck with this anywhere near an airport.
| If they are worried about 1w handheld lasers, a 400w one aimed
| skyward will require a NOTAM every time you want to turn it on.
|
| The boiling tea thing goes back long before the Japanese team
| working on this tech. That is a reference to pre-WWII request
| from the British government for tech that could boil a few liters
| of water a distance: a death ray. That request eventually
| resulted in what we now today call radar.
|
| https://www.bbc.com/news/business-41188464
|
| >> "Suppose, just suppose," said Watson Watt to Wilkins, "that
| you had eight pints of water, 1km [3,000ft] above the ground.
| TameAntelope wrote:
| Just put them underground.
| bialpio wrote:
| At this point you might as well just put cables in the hole
| that you had to dig up, right?
| minsc_and_boo wrote:
| Wired cables still have electrical resistence.
|
| Better to beam power over buried vacuum tubes.
| bialpio wrote:
| > Note that in all the pictures the receiver seems to be on a
| tower or at least above the emitter. No doubt this is a safety
| consideration
|
| My understanding of the article is that the system has a safety
| mechanism built into it that cuts the beam off when something
| is detected in the path, so likely it's an issue with providing
| uninterrupted service rather than safety?
| csours wrote:
| When is this better than solar panels and batteries?
| elihu wrote:
| Powering/charging aircraft without them having to land.
| Ancapistani wrote:
| When your power source is a solar satellite in geosynchronous
| orbit, for starters :)
| rektide wrote:
| Highly tuned wavelength-specific photovoltaic sounds interesting.
|
| > _The receivers for optical power transmission are specialized
| photovoltaic cells designed to convert a single wavelength of
| light into electric power with very high efficiency. Indeed,
| efficiencies can exceed 70 percent, more than double that of a
| typical solar cell._
|
| I'm still thinking of the last power-beaming example, a Navy
| microwave-based one, which showed up a month ago (and in this
| article) & was hyped up but ended up being pretty crazy low end-
| to-end efficiency if you read the fine fine print. If these folks
| really can do real 50% end-to-end efficiency- major congrats to
| them.
|
| At some point, I think solar concentrators probably do make great
| sense. We already have some pretty big scale solar-thermal
| plants. These can have nice thermal storage capacity, for off-
| peak usage. The idea of launching some satellites & trying to
| point lasers or concentrators down at an on-the-ground collector
| seems more promising than microwaves, given what lukewarm at best
| efficiencies we've seen out of attempts to leverage microwaves.
| That said, the article itself contra-indicates:
|
| > _But there have been improvements in efficiency and increased
| availability of devices that operate at much higher frequencies.
| Because of limitations imposed by the atmosphere on the effective
| transmission of energy within certain sections of the
| electromagnetic spectrum, researchers have focused on microwave,
| millimeter-wave, and optical frequencies. While microwave
| frequencies have a slight edge when it comes to efficiency, they
| require larger antennas. So, for many applications, millimeter-
| wave or optical links work better._
|
| [1] https://newatlas.com/energy/us-navy-beams-1-6-kw-power-
| kilom... https://news.ycombinator.com/item?id=31128267 (245
| points, 33 days ago, 194 comments)
| gigel82 wrote:
| It starts interestingly enough talking about optical (which is
| proven possible though horrendously inefficient), but then goes
| into snake oil territory talking about charging mobile phones at
| a distance.
|
| I'm not an expert, so here's one explaining why wireless power is
| mostly bullshit: https://www.youtube.com/watch?v=MCyLO-1grEk
| JoeAltmaier wrote:
| I imagine beaming power to space (for powering space devices) and
| from space (from orbital solar power stations) would be pretty
| useful.
| petschge wrote:
| If you are doing solar anyway and need a decently transparent
| atmosphere to get power through, why not leave the solar panels
| on the ground?
| mNovak wrote:
| The article jumps between multiple experiments (some laser some
| microwave), but if you're interested in the the recent 10 GHz
| microwave experiment the authors were a part of (and which was on
| the HN frontpage recently) -- 1.6kW delivered over 1km -- the
| details were published in [1].
|
| Very relevant datapoint: the transmitter source was 100kW, fed
| into a 5.4m dish. The receiver array was 2x2m. The end to end
| efficiency, which this article pointedly avoids, is on the order
| of 1-2%, over 1km.
|
| [1]
| https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=966...
___________________________________________________________________
(page generated 2022-05-26 23:00 UTC)