How would you heat water using no electric equipment or fire source?

For example if a hurricane knocks the power out and you need warm or hot water?

Solar. Camping stores sell black bags to hold water to be heated by the sun for showering while camping. You can build a solar heater for your house by constructing a large shallow rectangular box with a glass top. In this box install copper pipe in a serpentine pattern. Paint the inside of the box and the pipe flat black. Connect the inlet of this to your fresh water and the outlet to your existing hot-water heater inlet. Position on your roof facing the sun. This will pre-heat your water and can save you energy costs when you do have gas/electricity.
trf7 years ago
Chemical reaction as in for example those hot hand packs that you can buy. Once exposed to air it makes heat.