If you got it running on solar, then fuck why not?

Monero mining isn't about making bank, I mean, you could hit a 0.6 XMR reward block, that potential is every 2 mins. So, ~120 USD potential every 2 mins.

Pooling is probably better, but hell, if you've got old hardware lying around and some sort of 'free energy' source, then why not use it? opportunity cost?