In what manner? I can't say I have an opinion about the way DC lighting looks, but if it made for easier work with the solar power of an already custom-beyond-reason job, why not?

You can "feel" AC - not the power but the sounds that it creates inside devices. There is a resident "hum" from most mains AC devices, particularly energy bulbs, linear tranformers, CRTs, switch mode power supplies, heating, appliances etc.

If you're all DC with LED lighting etc, there is no 50/60Hz hum any more.

You genuinely don't notice it until it's not there any more.

It probably does feel different. To him. Please don't blame people for their feelings or force them to over-analyze or rationalize them. We're all human. It would be different if he was writing a scientific paper on the subject, of course.

Anecdotal data point: I can see it. Not when looking directly at a light but on my peripheral vision it is very noticeable at times. I'm pretty sure lots of people are able to perceive it but do not mind.

NB: I'm in Europe and the AC is 50Hz.

Same here, flickering goes from noticeable to disturbing.

I'm also far too sensitive about this kind of details, solarization of plasma panels, dithering of 6bit lcd..

This is not true.

Try the following experiment. Find a mercury-vapor street light or other mercury vapor light. Holding your eyes straight ahead, quickly move your head to one side or the other. You will actually see the flicker. If you can find one, you can do the same experiment with a drive-in theater from a distance of, say, a mile. However, that is a much lower rate--24 frames a second.

I think the same effect can be observed with sodium lamps.

Florescent lighting is worse. While it also goes on and off 120 times a second when being fed with 60-cycle AC, there are often sub-harmonics that give amplitude changes at a lower, more easily perceived frequency.

So it is not unreasonable that one can observe AC power cycles, even if only occasionally.

I don't know about "feels", unless he has some serious synesthesia issues, but it's far from unheard of to be able to see it.

Speaking from personal experience, I have two data points to contribute. I have been able to see a flicker quite clearly from my peripheral vision coming from an LED christmas light fixture. I remember this clearly as it was so distracting that I had to reposition my body during the conversation to face away from it entirely. In another instance, it was noticeably irritating the first few minutes I ever sat in front of a television in Europe (being used to the higher refresh rate in the US).

Is he not referring to the flicker that AC lighting has which some people can see (at least out of the corner of their eye)

Most AC-DC converters are switching power supplies that switch on and off at very frequency (ie. 10kHz). When you have 2 switching supplies close together they can introduce some interesting harmonics, especially if they aren't shielded well.

Likely, he switched out incadescents for some other lighting type and if he was using flourescents you can definitely hear it.

Put into context, the initial drive to go off grid and build something like this was due to his employer bringing in fluorescent lighting and not permitting employees to use their own lights. He quit his job over this. So clearly lighting is a big deal to him and I wouldn't doubt that this environment feels much more peaceful than a cubicle with fluorescent lights. He also claims that he can see flicker in fluorescents as well as incandescents.

Listen to a house during a blackout. Nothing to hear.