2 ideas, one is solar, and while that might be a common idea, the way in which energy is collected, stored, and used would be of interest. Loss from heat, such as the heat made by inverters is considered a waste heat. Yet this waste heat can be used for other things. Even human sewage is a usable product, if used properly for energy production. Another idea, and 1 other is the hydrogen/air fuel cell, which is in current use, by the way with an efficiency of +85%, or waste nuclear pellets for a heat to electricity power source using thermocouples. The biggest thing for nuclear pellets is how to keep them locked up so that natural disaster, or terrorist act could not open up the generator to expose the pellets, or make the effort extremely tedious and long term in effort such as to make it not worth their time.