Is it feasible to transfer energy from power stations to communities via photons instead of electrons?

Question

Electrical wires are relatively inefficient in transferring energy--especially when the place of production is quite far from communities.

Would it be possible to transfer that energy via photons? I realize that to some degree photons react with atoms, but might there be a specific condition in which this would be feasible and even more efficient--such as a specific wavelength of the electromagentic spectrum which encounters little resistance from the atoms in air (and thus low energy loss).

This is often a hurdle for utilities when the source of power is far away from the communities, such as hydro electric dams. I'm not speaking about removing metal wires altogether, just when it may be practical.

Related article (edit): A startup in New Zealand has done this: https://interestingengineering.com/nz-startup-to-build-first-long-range-commercial-wireless-power-transmitter

The company is called Emrod and has a page discussing the technology here (re: https://emrod.energy/wireless-power/)

Answer 1

It's not really worthwhile in this type of situation. (It makes sense in other situations however ... like transferring power from the ground to an airplane or satellite.)

The two most plausible system types are:

(A) Microwaves / radiowaves: Emitted by an antenna, collected by a rectenna

(B) Visible / infrared: Emitted by a laser, collected by a photovoltaic cell.

But it won't work very well. The problems are:

Losses at the transmitting end: You can't turn electrical power into electromagnetic radiation with 100% efficiency in practice. For (B), the best you can possibly hope for is ~75% efficiency (link), but that's at pretty low power. I suspect that a huge gigawatt laser would be much less efficient. I'm not as familiar with (A); it might be higher.

Losses at the receiving end: You can't turn electromagnetic radiation into electrical power with 100% efficiency. I don't know enough to guess the actual efficiency, particularly since it depends on the intensity of the incoming radiation (for both (A) and (B)).

Losses in tranit: The question concerns free-space transmission, not waveguides (or fiber optics) (which have their own problems), so I'll address just that. For (A), you can use a phased array antenna to beam the energy to some extent, but it will still spread out enough to cause most of it to miss the target at any appreciable distance (certainly over 1 kilometer). For (B), you can beam a laser over a couple kilometers with a reasonable-sized receiver, but there would be significant losses (absorption and scattering) from dust in the air, humidity, fog, etc. See free space optical communications for more discussion of these practicalities in a slightly different context.

Too much power: Additionally, free-space optical transmission won't support that much power, like the gigawatts that might be produced by a power plant. Such an extremely powerful laser will probably ionize the air, which leads to absorption. It is also a safety hazard for many obvious reasons.

So anyway, electrical wires are the better, cheaper, and more efficient solution, except when they are literally impossible (like recharging drone airplanes, see link at top).

Answer 2

This has been researched somewhat as a possible means of transferring energy from orbital solar farms to the surface of the earth.

The problem for surface use is diffraction. It limits how narrow you can make the beam: Lasers and Collimation But that also gives you a straight beam, whatever frequency you use. That limits the effective transmission distance due to the curvature of the earth, unless you want to build a very expensive tunnel for your beam.

Radio broadcasts don't have this problem because they either diffract along the surface or reflect off the atmosphere. But they're broadcasts, not a point-to-point beam.

Then there's the safety issues. Not only is a powerful beam in free space a huge threat to anything along its path, but it's hugely dangerous if the aim is disrupted in any way (such as due to an earthquake). Or if a reflective object finds its way into the beam it can be a threat to anywhere in sight of it.

Answer 3

It's already happening. We call this process "radio and television". After you think about this it may occur to you that the relationship of power per square cm is markedly attenuated by the 1/r^2 relationship that is seen with distance between source and receiver. So all you get (after considerable amplification) is the mechanical waving of a speaker cone.

The other perspective is that the electrical power is also transmitted by photons since that is what is transmitting mechanical power from the generator armature to the generator windings. Furthermore photon transfer is occurring at every transformer stage in the process of electrical power distribution. It's the ability of wires to "focus" and "constrain" the flow of energy that makes this process effective.

Collimation of photons is discussed here. The size of the antennas would obviously be larger. (I haven't figured out how this would get hooked inot the AC electric power grid yet.)