Woodland, NC made the news recently for banning any new solar farms. In a public meeting at the town council residents accused the solar farms of harming the surrounding vegetation and possibly causing cancer.
Meanwhile, in Japan farmers have been building solar panels above their crops without reducing yields. Turns out you can cover about a third of the area above plants without diminishing their growth.
They call it solar sharing and it is made possible because of the
“light saturation point.” The rate of photosynthesis increases as the irradiance level is increased; however at one point, any further increase in the amount of light that strikes the plant does not cause any increase to the rate of photosynthesis….
Based on the tests conducted at his solar testing sites in Chiba Prefecture, he [Akira Nagashima, the developer of the solar sharing system] recommends about 32% shading rate for a farmland space to reach adequate growth of crops. In other words, there is twice as much empty space for each PV module installed.
Source
www.renewableenergyworld.com/...
The Japanese are doing PV, the magic crystal, but there are other ways to use that solar real estate. Solar heating panels for greenhouses and floating row covers to produce a four season micro-climate and year round production is another possibility. I suspect that the growing number of rooftop urban farm operations will be looking into this and other possibilities.