Do you really believe a Bitcoin miner would accept being shut down for most of the day? - yes, as the hardware cycles have slowed down this has become more and more viable to use old hardware some of the time.

Instead of putting a Powerline there or building a smelter or something else, Bitcoin is easier and makes more money quicker. - I assume there is already a powerline to any wind/solar farm. The issue is the negative priced electricity. If you can't compete with a bitcoin miner that is always seeking the cheapest electricity regardless of location then maybe your project isn't economically viable. Its not like miners have a monopoly, just agree to pay more than they are willing to pay