I've been thinking about how to keep my EV ('94 Saturn SC2) heated in the winter. I like the idea of using the original heating components, just heating the coolant and using the normal controls.
I know I don't want to use cold outside air to mix in with the heater core to adjust them temperature. I plan to recirculate air only and use a variable speed water pump to adjust how much heat I get in the cabin.
An electric water heater is the simplest option, but it directly impacts range and I want to avoid this at all costs.
A gas/diesel/propane water heater would be compact and can effectively extract most of the energy from the fuel. However it goes against the purist's all-electric spirit and it requires periodic refilling.
Then I had a crazy brainstorm: Wax. Yes, wax. Standard everyday paraffin candle wax. No, I don't plan to burn it, I plan to melt it. I plan to melt about 50 lbs of candle wax while plugged in charging and extract the heat out of it during my commute.
The 50-lbs is a SWAG based on how much energy it takes to melt that much wax, about a 1KW electric heater running for 1 hour. I would extract all of that heat from the wax at about 160-180 degrees, whatever the melting point is for the wax I use. When the wax all solidifies the temp would then drop down below the wax's melting point. Hopefully my trip will be done before that and I will plug the car back in to charge and melt the wax again.
The plan would be to take a basic car radiator, enclose it in a plastic tank sized just right to hold 50-lbs of melted wax, which I figure to be about 8 gallons or so. The wax is a great insulator, so I want most of the melted wax close to radiator's fins or the wax will "freeze" onto the fins and the heat from the rest of the melted wax will not be able to get to the radiator's fins to heat the water to heat the heater core to heat the cabin air and ultimately to heat me. The radiator needs to be large enough to have 8 gallons of melted wax in a snug tank. Wax expands as it melts so the tank has to be able to flex a little. Thick insulation around the tank should keep heat loss minimal.
I would have an electrical heater in-line with the coolant system as well and as the car was charging the heater would heat the water up above the wax's melting point and the water pump would transfer that hot coolant to the radiator to melt the wax. The heater's thermostat could be set to 200 or so, like a nice warm engine.
In the morning the driver can turn on the car's heating system to heat the cabin up before disconnecting the charger and the electric heater. Then the heater only has to keep the cabin warm for the drive.
I know I can just carry an additional battery along with me that would hold 1 KWh or so of electric heat for the same weight as the wax, radiator, tank, pump and heater. Heck, I could probably carry 2 batteries! But what is the fun in that? Using wax as a "heat battery" just seems more cool to me, or should that be hot?
Wax would cost about $1.50 a pound, but I'm thinking of just recycling every old candle I can find instead. More eco-friendly to recycle old wax, I guess. I should be able to use the car's original radiator. I'm thinking of pouring the wax onto the radiator to solidify and make a mold around it in the shape I want for the tank. Then I can use something else to form a tank, a poured plastic resin, maybe? I can make a custom, sealed tank around the radiator and only leave the radiator's inlet and outlet. Next I would cure the tank, connect hoses and insulate the heck out of it.
If I go to all of this trouble it makes sense to just embed the heating elements inside the tank, right onto the aluminum radiator. Then I wouldn't even need to run the pump when I want to heat it up. I should embed the temperature probe for the thermostat in there as well, on the outside of the tank, to measure the wax's temperature and turn the heater of and on.
If I need extra heat on the trip I can run the heater off of the traction battery just as well, and I can do that also if I pull a generator-trailer for long trips, as I have dreams of doing one day.
So what do you think? Could it work?
Thanks for your input.