For household-scale I only have a proposition regarding storing/generating heat, namely compost. A compost pile produces a surprisingly large amount of heat. I

For household-scale I only have a proposition regarding storing/generating heat, namely compost. A compost pile produces a surprisingly large amount of heat. If you run a hose through it you can have sufficiently hot water all winter. You could maybe use it to produce biogas and burn it in a turbine, but that's anything but household-scale. As for electricity you won't find anything better than batteries at the moment.