This particular author isn't an environmentalist as much as a low tech enthusiast.

Hence, solar and wind power generating electricity, which are clean and green technologies but are not "low tech" do not fit his particular niche interest.

Though the article was from 2018. I think he may have evolved slightly as solar PV begins to feel more like a bit of lumber or a steel girder or anything else you can pick up at a hardware store and so passes his somewhat fuzzy and arbitrary definition of low tech.