There are three main scales of electrical power generation: Large-scale generation is what we’re most familiar with, using centrally-located power plants and wide-spread distribution systems. Micro-generation is when you locally or home-brew power, via say, solar cells, wind, or small hydro generation. The third type is known as nano-generation, which is when the devices that would normally draw power from a large-scale or micro operation, generate their own juice. As solar photovoltaics and power storage technologies improve and come down in price, nano-gen will increasingly become a viable option for some types of devices. Read more in this piece on Treehugger and this Clemens Betzel (of G24 Innovations) opinion piece at BBC.
