I am starting a new thread for discussion on this subject:

I'm planning to do a full VintageAir replacement on my S1 this winter, so I am interested in what you are thinking about.

I'm far from knowing how all this may work, but I think there's more to it than just reversing the flow of coolant. It's basically the same as a heat pump used in houses. You will need another expansion valve before the condenser when in heating mode and then bypass the other. Also, if it gets too cold outside, it won't be able to create heat.

I understand that you want to save space, but it seems to be a lot of work when you have a free source of heat already.

 

"it seems to be a lot of work when you have a free source of heat already."

I may be confused, but I thought that the car was to be electric. The motors do get hot, but it's not as convenient a source of heat as the coolant of an internal combustion engine.

There's no doubt that a heat pump is more efficient than plain resistance heating (or burning fuel) but as you say the efficiency increase is not much when the ambient gets very cold.

A good way to think about heat pumps when operating as heaters is that they pump heat with some efficiency (so much heat pumped from the cold outside into the warmer inside), and, if the efficiency is less than 100%, the electrical energy that didn't go into pumping heat is "lost" as heat. So even 1% efficient gives you 101% more heat than resistance heating, where it's all lost as heat. Of course the pump has to be located in the right place. IMHO.

 

oh, ya. I forgot that he was doing electric...

I found this animation that does a pretty good job of describing how a heat pump works.

 

Yes the car will be electric. I would think if you have the heater core and hot engine to warm the water, it would be best to stick with that design. I believe although havent read or checked explicitly, that the Vintage Air systems maintain the traditional style of heater core using hot water from the engine. bypassing the vacuum valve like Roger mentioned in my original post might be a worthwhile option since youre messing around with that system already.
If your heater core was dead and you really wanted an alternative, there are 12v heater elements you can buy (designed for electric cars) that would certainly fit and work quite well. If your winters are long you might consider upgrading your battery and alternator but otherwise they would work well.

As robert mentioned electric motors do get hot, not sure if its hot enough to warm the air, mine will use about 400-500watts of power at 60km/h, only a portion of that will become heat and considering a normal heater is in the vicinty of 2000 watts, its not much. Of course i could apply a lead foot, get home quicker and heat the motor more to improve my heating, although i doubt the police would appreciate that as an excuse to speed. There are systems that warm the water like a kettle for your heater core that i could use as a booster. Alternatively i could just install a heater element to warm the air but again as Robert mentioned, not very efficient.

system to heat water
EVTV Motor Verks Store: Hot Water Heating Kit, Cooling and Heating, glycolkit
(i think this example is intended for heating batteries in cold environments, i think i have seen cheaper options for cabin climate control.
air heater element
EVTV Motor Verks Store: PTC Space Heater, Cooling and Heating, heater
there are others but these will serve as an example.

 

This is an interesting question. I assume you've confirmed that none of the electric vehicles on the market use heat pumps?

I wonder, assuming that to be the case, that the problem is performance in very cold weather. The cars are presumably designed to serve anywhere. In contrast, home heat pump systems seem to be most efficacious in climates that aren't too cold. Otherwise, they require booster resistance heaters.

I should clarify that my comment on them always being more efficient than resistance heaters depended on getting the "wasted" heat into the cabin. That wouldn't be easy. When in AC mode, the wasted heat must be outside the cabin--the motor and compressor. To move these components inside the cabin when heat is called for, and back outside of it when cold is called for, would be obviously too complex.

I would think that the electric car makers will hone in on the optimum solution, particularly because overall efficiency is what they're all about.

 

If your motor creates enough heat, you could do like they did on the air cooled engines and have an air to air heat exchanger that would pull outside air (not from the engine bay, like the Corvair) over the motor and then pipe it into the passenger cabin.

Don't the batteries also generate heat?

 

Robert, There are a few solutions. A Tesla uses a resistance heater and a Nissan Leaf uses a 'heat pump' which i think is assisted by a kettle element warming the water that is circulated trough the heater matrix when the outside temp is not high enough. I honestly havent looked into these systems that much, theyre often conrolled by CAN (computer language) rather than buttons to turn things on and off, which complicates their use, im no IT guru.

Baudrate, the batteries will produce some heat but again i dont think it will be enough to sufficiently warm the water/ heater matrix etc.

I approached a local vehicle air conditioning company to ask their advice about using the reverse valve and they were little help. I think i need to see someone who does industrial AC/ refrigeration who might be more accustomed to modifying and customising systems rather than swapping parts.
That said, a $300 resistance heater is maybe a a fair financial compromise compared to a $150 valve plus whatever it takes to modify the system. Its cold enough to use a heater here for maybe one month a year plus intermittent use for defrosting the windshield. I'm feeling stubborn though, i want what i want!