Sunshine can do the same thing without burning wood. lol https://www.youtube.com/watch?v=nC_Ql5qVs4Q
Yep, lol was gonna post that one as well. But we're lacking that good yellow stuff here, esp in winter months.
But most have a woodburner in garden now or know how to get hold of one.
Rig it up, transfer water from ibc tank through it and into van perhaps. Can do so in evening night before, whilst eating your tea. Insulate your tank well and if eater is going in way above 100degrees, it will still be in high 80's by next morning.
Just takes a little thinking and effort outside the box.
Oh, and dont put your hand in the water to test it hahaha