First, it's conduction electrons in a metal that move back and forth due to an EM wave. No problems, they are very good conductors because they have so many near free electrons.
Second, the photons may be low energy, but unless there's enough of them to have the necessary power or electric field you can't get enough current, or electrons to move, to detect something. So you need enough of them, might as well analyze it using classical EM
Third, a 1 km wavelength is a frequency of 300,000 HZ, or 300 KHz. It's in the so called the LF, low frequency band, and often have used tall monopole antennas (like the ones you see on a highway from afar). Called mast antennas. They use vertical E polarization, and usually propagate mostly as ground waves, with little attenuation for hundreds and thousands of miles because their long wavelengths makes them diffract over almost all obstacles and hills and mountains. There can be other antenna forms, including just a long wire, and short ferrite loop antennas that are just a foot or so long; see some of the other forms in the second reference below.
The large antennas usually aided by some coils or loads at the bottom to get a reasonable impedance can work pretty efficiently. The largest such antenna finally collapsed in Poland in 1991, it was for a 1.3km wavelength, and was 646 meters high. It was half a wavelength, and most of the LF antennas are so-called electrically short because they are half a wavelength or less. When much less they are less efficient, but are used. See mast antennas at
https://en.m.wikipedia.org/wiki/Mast_radiator
LF has been used for radio navigation (the Loran C system, other ground, air and over water), emergency communications, long wave radio, submarine communications, clock radio, and other things. It works, the antennas are not and don't have to be that efficient, just long enough to have some varying E field. See more on LF at https://en.m.wikipedia.org/wiki/Low_frequency
