“DC power doesn’t transmit across long distances well. My solar array, inverters, and battery stack have to be somewhat close to each other. I’m sure the same is for grid battery storage.”
Agree on (battery) DC power not doing well at long distances, but grid-scale battery power ALWAYS gets inverted to 60 Hz, somewhere close, and then tied into the grid, and there are high voltage power lines running all over the country where it could tie-in. So why not invert the power near the batteries and tie-in next to a power line in the middle of Nevada, or wherever there are few people around?
“DC power doesn’t transmit across long distances well.”
Actually, for transmitting hundreds of megawatts of power very long distances (multiple hundreds of miles), it is ideal.
The problem with AC power is that a transmission line is big antenna. This doesn’t matter for house wiring, and probably isn’t much of problem for most local distribution, but it is for very long distance high power transmission.
For example, “the Pacific Direct Current Intertie (PDCI) is a 1354 km, ±500 kV, 3.22 GW, HVDC transmission line from northern Oregon to southern California” (https://newunivstudies.org/aec/electricity/hvdc/pdci/). Given that the wavelength of 60 Hz AC is about 4997 km, this transmission line is about 0.27 of 1 wavelength, or close to 1/4 wavelength.
Quarter wavelength antennas are perhaps the most widely used type in the world (being a good tradeoff between size and efficiency). Now 0.27 wavelength is hardly optimal, but it will radiate (inefficiently) at 60 Hz, thereby wasting a LOT of electrical energy by both radiation and wavelength mismatch losses.
That’s why a lot of new power distribution system, from Canada and Europe to China and Brazil, are going with High Voltage DC (https://newunivstudies.org/aec/electricity/hvdc/).
P.S. I visited the north converter station of the PDCI in the mid 60’s, and it was very impressive. When I was in that area in the 80’s, it was closed to the public (security reasons).