Logitech did this before, like 15 years ago, I actually have one tucked away. Very similar to the K750 they have been offering for a while. Charged on solar or artificial lighting, using a small coin-cell battery that can be replaced as it ages (few years). The older version had a larger solar panel (?) compared to this one. It was fine to use, average cheap office-style keyboard. But the lack of wires is an interesting idea.
For those that want the novelty and minimalistic appeal, that aren't picky about their keebs... and not many other qualities vs a standard board.