Super! some i had heard of and others not, right now trying to keep my motorhome warm at night is a challenge! i been using two upside down flower clay pots over night lights, funny i was just talking with Hive account@markwhittam yesterday about the copper coil around stove pipe, we were wondering can the heating of the water in the pipe move the water upwards to an insulated storage tank? great post, glad to have found you :-)