[Bicycle Bob]

I've been planning to store engine heat for my micro-RV, and had spent decades waiting for Glauber's salt to hit the shelves. That's not going to happen in the foreseeable future, but paraffin has nearly the same heat of fusion and its temperature can be readily increased with stearic acid. I've been thinking of using a water muffler to recover the heat and steam from the exhaust, with a pump to circulate it to a tank containing mostly paraffin in thin plastic tubes. The coolant could also circulate to a similar tank. The wax would slowly melt, storing heat near the boiling point for water. To use that heat in your house, you'd only have to hook up two hoses, and circulate water to a radiator.