I like the idea of using Paraffin as the source for heat storage and taking advantage of the phase change of the material for the added energy storage capacity. In looking at the heat storage capacity and the factoring in a usable phase change temperature I could see that holding a nice bit of heat.
the units get a bit wonky here, but bear with me
Heat for us is simplest in BTU (at least to compare to standard heaters). If using paraffin (the one I found at HobbyLobby has a melting point of 133 deg F which would correspond to paraffin -26 carbons) that would leave a heat of fusion of 256 kJ/kg to convert to BTU/lb we need to
256 kJ 1 BTU . 1 kg . 110.3 BTU
-------- * ---------- * -------- = ----------- of paraffin (this is only for the phase transition)
kg 1.055 kJ . 2.2 lb . lb
so that in addition to it's normal heat capacity which for a low melting paraffin is about .659 (
Btu / (lb * F))
If a batch of paraffin was taken from 50 deg F to 150 deg F and had a weight of 40 lbs we could expect
(100*40*.659)+(40*110.3) = 2636 + 4412 = 7048 BTU which is equivalent to an 800W electric heater for about 2.5 hours.
So backtracking for a bit here we would need roughly
[font=STIXGeneral,]100x[font=STIXGeneral,](0.659[font=STIXGeneral,])[/font][font=STIXGeneral,]+[/font]x[font=STIXGeneral,]([/font]110.3[font=STIXGeneral,])[/font][/font][font=STIXGeneral,]=[/font][font=STIXGeneral,]2730 (heat output from 800w heater for 1 hour)[/font][/font]
Which leads to about 15.5 lb of paraffin for 1 hour equivalent heat from an 800W electric heater (assuming you get to the system to 150 F and it drops to 50 at night, and no losses... lol)
When I get my trailer built I will plan on measuring the power input to interior temp comparison, but it would be interesting to see what other ppl think of using a small heater for their rigs.
p.s. if you see any errors in my calcs, let me know... with all the units and conversions + being rusty, there could be errors.