A trio of researcher groups have developed a way to power tiny sensors with plants, including Harwell who specialize in extremely low powered IoT devices, Lacuna Space to help with satellite communications and Dutch grass enthusiasts Plant-e to provide a smart green thumb or two. This particular ‘fuel cell’ was a 50x500mm plant pot with grass, which was able to producedover 0.2 mW continuously, well as long as the plants were still alive.
That is not a lot of energy, but it is more than enough to send LoRa messages, an extremely low power, wide area sub-gigahertz networking protocol designed to let IoT devices communicate without reducing the battery life significantly. In this particular application, as long as your greenery is alive, your IoT device will be able to continue to power a sensor and report to home. This might not be as effective as a solar panel in the desert but is yet another way to monitor a variety of remote areas without much maintenance required.
In this demonstration for remote sensing/IoT applications it is not about the electricity yield of our plant-cells (which is very small), but what cool things you can actually do with it: now in wet nature anywhere around the world you could do measurements of which you receive data via a web interface for example, without ever having to visit the remote location to change batteries.