7 ms·

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. Thi

by c54 4y ago

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?

kurthr 4y ago
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 4y ago
  > 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 https://ieeexplore.ieee.org/document/4922910
droopyEyelids 4y ago
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 4y ago
  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.
photochemsyn 4y ago
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 4y ago
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 4y ago
  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.
  - soco 4y ago
    A cut off beam has an efficiency of zero, so every avoided pigeon is eating into the already meager efficiency of the system. But, good that scientists keep trying, maybe something good will come out of it later.
  - sandworm101 4y ago
    At these energies they would have to shut down in fog/rain. A single raindrop or snowflake could deflect enough light to potentially blind someone, or at least give them a permanent blind spot on their retina. A trillion raindrops passing through the beam would be statistically very dangerous for anyone, everyone, nearby.
lordnacho 4y ago
5% per what distance?
wcoenen 4y ago
> 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 https://www.energybot.com/electricity-rates-by-state.html
- db65edfc7996 4y ago
  Wait until he hears about the efficiency of an ICE. 5% losses for fixed infrastructure feels like not a big deal?
  - zdragnar 4y ago
    This seems like a very strange comparison to me. Why would you suggest that an ICE is a substitute for moving electricity from solar panels in the southwest to NE? The percentage losses are irrelevant, except in the context of substitutes. An ICE could be 1% efficient if the next best substitute cost 100x more to operate. Likewise, 5% losses in transmission might add up over very long distances to mean that it makes more sense to build wind in the appalachians or off-shore from NY than it does to power the NE with solar installs in Arizona. OR, beaming energy eating 50% while costing even more due to the amount of exotic materials in construction.
  - namecheapTA 4y ago
    Burning wood might be even less efficient than burning gasoline. But if wood was free, that makes it pretty efficient per dollar.
marcosdumay 4y ago
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.
deleted 4y ago
[deleted]
dontbenebby 4y ago
I'm actually trying to learn more about liquified natural gas right now. (Eg: if you can gather it sustainably, small batches, can that be used to supplement things other than solar like wood, wind, and hydro? If so shipping that around might make sense.) I don't know if you'll get many detailed numbers, I got the sense that's the real "business intelligence", not meta level ideas like the one I just expressed, when I was having a series of informal conversations about green energy.
- pjc50 4y ago
  > gather it sustainably From where? > small batches The capex cost of handling equipment ruins this. That's why so much natural gas is already flared. LNG efficiency in large modern plants appears to be about 80% per https://static.conocophillips.com/files/resources/smid_016_weldonspaperlngindustry.pdf https://static.conocophillips.com/files/resources/smid_016_w...
MobiusHorizons 4y ago
Short answer much much worse than wires. Most of these systems have less than 10% energy transmission efficiency .
bradknowles 4y ago
Only 5% transmission losses? I don't see how that could possibly prohibit large solar installations in the US southwest. Especially since we already have large solar installations in the southwest.
ben_w 4y ago
5% is a fairly trivial loss, especially as PV is usually cheaper than 95% the price of most non-renewable alternatives. The main limit to long distance, even genuinely global[0], electrical power grid is that it would take several years of current global metal mining to build. But we don’t have to do it all at once, so even this isn’t really a show-stopper. [0] 5% loss per Mm is 64% loss over 20 Mm with existing HVDC products, and yet because you can place the PV in the globally optimal location where it costs $US13.5/MWh at source and therefore $US37.5/MWh on the antipode, it’s still cheaper. But even for just the electricity worldwide today you need to think in terms of square meters of cross section, and that’s a lot of metal to mine.
- vitus 4y ago
  On top of that: HVDC scales because resistive loss in power transmission can be reduced quadratically by increasing the voltage (assuming fixed load, so current drops to compensate). (Loss is also increased linearly by transmitting more power through it. Thanks, Joule.) If your 5% loss per Mm is at 500kV, increasing that to 1MV (entering the territory of UHVDC) means that you're only talking 1.25% loss per Mm which translates to "just" 22% loss over 20Mm, or even just 5% over the ~4Mm that separates Phoenix and NYC. That tech exists. We just haven't begun to build it in the US. (There are plenty of obstacles beyond just the materials cost.)
  - BizarroLand 4y ago
    I wonder if we might live to see excess electricity being beamed to geosynchronous satellites and then redirected on the fly to locations that need them. That would be pretty awesome even with larger losses and allow better overall land resource usage. Imagine Solar Electricity from the Sahara being beamed to London during a heat wave to decrease the costs of running AC and saving lives.
    - ben_w 4y ago
      I’d be very surprised if that works out better than a really big wire, but it’s not inconceivable that a future post-scarcity government may prefer the aesthetic.

by c54 4y ago

kurthr 4y ago

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 4y ago
> 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 https://ieeexplore.ieee.org/document/4922910

droopyEyelids 4y ago

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 4y ago
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.

photochemsyn 4y ago

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 4y ago

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 4y ago
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.
- soco 4y ago
  A cut off beam has an efficiency of zero, so every avoided pigeon is eating into the already meager efficiency of the system. But, good that scientists keep trying, maybe something good will come out of it later.
- sandworm101 4y ago
  At these energies they would have to shut down in fog/rain. A single raindrop or snowflake could deflect enough light to potentially blind someone, or at least give them a permanent blind spot on their retina. A trillion raindrops passing through the beam would be statistically very dangerous for anyone, everyone, nearby.

lordnacho 4y ago

5% per what distance?

wcoenen 4y ago

> 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 https://www.energybot.com/electricity-rates-by-state.html

db65edfc7996 4y ago
Wait until he hears about the efficiency of an ICE. 5% losses for fixed infrastructure feels like not a big deal?
- zdragnar 4y ago
  This seems like a very strange comparison to me. Why would you suggest that an ICE is a substitute for moving electricity from solar panels in the southwest to NE? The percentage losses are irrelevant, except in the context of substitutes. An ICE could be 1% efficient if the next best substitute cost 100x more to operate. Likewise, 5% losses in transmission might add up over very long distances to mean that it makes more sense to build wind in the appalachians or off-shore from NY than it does to power the NE with solar installs in Arizona. OR, beaming energy eating 50% while costing even more due to the amount of exotic materials in construction.
- namecheapTA 4y ago
  Burning wood might be even less efficient than burning gasoline. But if wood was free, that makes it pretty efficient per dollar.

marcosdumay 4y ago

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.

deleted 4y ago

[deleted]

dontbenebby 4y ago

I'm actually trying to learn more about liquified natural gas right now. (Eg: if you can gather it sustainably, small batches, can that be used to supplement things other than solar like wood, wind, and hydro? If so shipping that around might make sense.) I don't know if you'll get many detailed numbers, I got the sense that's the real "business intelligence", not meta level ideas like the one I just expressed, when I was having a series of informal conversations about green energy.

pjc50 4y ago
> gather it sustainably From where? > small batches The capex cost of handling equipment ruins this. That's why so much natural gas is already flared. LNG efficiency in large modern plants appears to be about 80% per https://static.conocophillips.com/files/resources/smid_016_weldonspaperlngindustry.pdf https://static.conocophillips.com/files/resources/smid_016_w...

MobiusHorizons 4y ago

Short answer much much worse than wires. Most of these systems have less than 10% energy transmission efficiency .

bradknowles 4y ago

Only 5% transmission losses? I don't see how that could possibly prohibit large solar installations in the US southwest. Especially since we already have large solar installations in the southwest.

ben_w 4y ago

5% is a fairly trivial loss, especially as PV is usually cheaper than 95% the price of most non-renewable alternatives. The main limit to long distance, even genuinely global[0], electrical power grid is that it would take several years of current global metal mining to build. But we don’t have to do it all at once, so even this isn’t really a show-stopper. [0] 5% loss per Mm is 64% loss over 20 Mm with existing HVDC products, and yet because you can place the PV in the globally optimal location where it costs $US13.5/MWh at source and therefore $US37.5/MWh on the antipode, it’s still cheaper. But even for just the electricity worldwide today you need to think in terms of square meters of cross section, and that’s a lot of metal to mine.

vitus 4y ago
On top of that: HVDC scales because resistive loss in power transmission can be reduced quadratically by increasing the voltage (assuming fixed load, so current drops to compensate). (Loss is also increased linearly by transmitting more power through it. Thanks, Joule.) If your 5% loss per Mm is at 500kV, increasing that to 1MV (entering the territory of UHVDC) means that you're only talking 1.25% loss per Mm which translates to "just" 22% loss over 20Mm, or even just 5% over the ~4Mm that separates Phoenix and NYC. That tech exists. We just haven't begun to build it in the US. (There are plenty of obstacles beyond just the materials cost.)
- BizarroLand 4y ago
  I wonder if we might live to see excess electricity being beamed to geosynchronous satellites and then redirected on the fly to locations that need them. That would be pretty awesome even with larger losses and allow better overall land resource usage. Imagine Solar Electricity from the Sahara being beamed to London during a heat wave to decrease the costs of running AC and saving lives.
  - ben_w 4y ago
    I’d be very surprised if that works out better than a really big wire, but it’s not inconceivable that a future post-scarcity government may prefer the aesthetic.