Just saw this video about Tesla adding a heat pump in the new Model Y. It looks pretty compact. As a Series 1 owner in FL this got me to wondering if the package could potentially replace the standard heater box and with perhaps some additional real estate, provide A/C as well. I haven’t explored it any further than just this random thought, so please forgive the complete lack of thoroughness in evaluating the concept.
Here’s the video:
Your first, major, problem will be how to power it. The Tesla heat pump is entirely electric, and surely runs at something well north of 100V. The Model S battery pack is 375V…
Regards,
Ray L.
I believe the Tesla orange cables carry 400v DC. 12 volt battery just operates the SRS, airbags, windows, door locks, touchscreen, and interior/exterior lights which Elon Musk wanted to ditch for the Y - but it is still there.
If you’re trying to convert energy (fuel, electricity) to heat, then the heat pump is the way to go. The guys in the video were unclear of the concept, but electric resistive heating is, technically, completely inefficient–all of the energy is converted to heat, none to work. A heat pump might be 66% efficient–that means you get 3 units of heat pumped per unit of input energy. AND, you get another unit of heat, because the inefficiency ALSO generates heat. That’s if you are pumping heat out of the cold outside air into the car. Of course if you’re pumping heat out of the car into the hot outside air, then the efficiency reflects only the heat pumped out–extra warming of the outside hot air doesn’t count.
In an electric car, a heat pump is clearly ~3X or so more efficient than resistive heating (like a home heat pump, the efficiency depends a lot on the ambient conditions). Air conditioning always uses a heat pump, in any car (but the system isn’t reversible to provide heat in most of them). But, the caveat IMO is that heat from an IC engine is readily available and otherwise wasted. I suppose this might not be true with super-efficient turbos, but not so for the XK. Similarly, mechanical power is available to operate the compressor. There are certain advantages to having an electrically powered compressor (constant speed for example) but to get the electricity you need an alternator, which isn’t constant speed (except on a diesel-electric train) and therefore isn’t very efficient. But generally, an all-electric heat pump is impractical in a non-electric car.
I suppose one could have a “hybid” car where the XK engine provides motile power whilst a rechargeable battery pack powers a heat pump. IMHO.
A car needs ~ 20,000 BTU/hour for effective A/C. Even with an efficient heat pump more than 2KW of electrical power would be needed for the A/C. As I remember the E Type generators are about 65 Amps or 0.78KW. You would need to find room for a VERY big generator or maybe the Tesla battery pack to power an electric A/C system. That is after you find a place to hide a decent evaporator and fan in the passenger compartment. (The SII A/C evaporator/fan system is marginal at best.)
As a point of reference, the A/C system in a typical car has a capacity of 2-3 “tons”, which means it transfers the same amount of heat as melting a ton of ice to water in a 24 hour period. A ton of water is ~235 gallons. This is a LOT of heat! That capacity is more than adequate for a typical household A/C system. The solar load on a car is MASSIVE.
Regards,
Ray L.
Heat pumps are clearly more efficient for electric heat up to 27 degrees or something like that, been a long time since I contemplated one, below that they had to default to resistance heat. That’s good for most environments most of the time. I like that the same unit and both heat and cool and I think, not sure that some of the hybrids have electric AC already. The big advantage I see here over home systems is while the car is moving they can capture or dissipate a huge amount of heat. I doubt its a logical retrofit however, a lot of plumbing required. Its like taking a window AC unit blowing cool air in and hot air out in summer then in winter turning the thing around so it blows the cool air out and hot air in.
pauls