These SolarGaps prototypes are interesting ways to harness sunlight as it's being blocked. Note: the video is heavy on the promotion and light on the tech specs, but it's a neat idea.
Via their site:
SolarGaps are efficient enough to generate up to 100 watt-hours for every square meter when mounted outside, and up to 50 watt-hours per square meter when mounted inside.
For example, a three-room apartment with windows facing south will be able to produce up to 600 watt-hours or about 4 kilowatts per day. In an office or retail space, you can generate up to 10 times more.
Here's a less slick version from the founder: