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Tesla heat pump / HVAC (non auto)

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I suspect for that scenario, at best, they might provide a premium outdoor unit that is quieter than the competition, and possibly a bit smaller or at least packaged differently (i.e. a tall rectangle rather than a large cube), to address the concerns you listed as being problems for getting one in your locality. Assuming they intended to re-use their existing designs, by going from AC to HVDC to drive ~400V heat pumps (but upscaled), you'd be adding extra inefficiencies in the conversion from AC to DC, so the HVDC compressor would need to be more efficient than a traditional one run from AC. Perhaps the efficiency might be gained as the average over time, by being able to run at different speeds.

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Now what if the DC power for that DC Heatpump does not come from the grid but from your power walls that also collect DC from your solar and the only loss is when converting from power wall to the home for the rest of the load?

See Tesla heat pump / HVAC (non auto) Thread #60 for more detail musings and further discussion (my homes spec/how things could be different / how Tesla could jumpstart new tech in DC home appliances / ...)
 
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The engineering thread is probably the best place for further discussion but I thought it important to have some discussion here so casual observers might get a better idea of what is actually involved. As a final note here I did some simple calculations and a reasonably efficient 20 cubic ft fridge uses 400kWh/year. If it's 80% efficient, (a guess on my part), that leaves 80kWh/year of waste energy x say $.20/kWh = $16/year of waste energy to recover.
All energy to the fridge is waste heat.
Efficency is how much energy is required to
  • transfer energy from the food to the room (which itself is also waste heat, until food is removed)
  • cancel the heat gain due to imperfect insulation
Any appliance's usage becomes waste heat in a closed system (other than endothermic cooking processes)
 
Maybe the innovation Tesla can bring is around using unconverted DC power collected by solar and power walls in a home HVAC/heatpump unit directly, skipping conversion loss for one of two two major energy consumers in my home.

Our home spec is
- northern California two level home with outside temperatures from 25F to 110F as the extreme winter/summer days
- 10kW solar (40 panels two 5kW inverters)
- 40kWh power walls (3)
- two Tesla home chargers in the garage
- Daikin One Heatpump, forced central air with two zones and two thermostats, inhibiting airflow with dampers to direct between zones

In our home the majority of power consumption happens from
- heappump heating and cooling - 240V AC 50A
- car charging - 2x 240V AC 50A (cars set to use 24A each unless in a hurry) typically at night from the grid for capturing low cost grid energy, sometimes at day from 10am-3pm to capture clean solar energy, i.e. leftover solar that would otherwise be sent to grid at low price time before 3pm
- clothes dryer - 240V AC
- stove - 240V AC
- dishwasher - 110V AC

Heating in clothes dryers and stoves is likely done with AC directly rather than converted to DC, but cars could charge off of DC.

Maybe Tesla could jumpstart DC home appliance technology by making a component utilizing their DC Heatpump design for redesigned clothes dryers, stoves and dishwashers?

Another thing I wonder about in heating/cooling homes is - the forced central AC does not result in evenly distributed heat in the home, i.e. the sun side of the house gets much hotter then the rooms on the other side while the thermostat sites in the middle. What if there was a way to exchange heat between rooms.

Also outside air temperature is sometimes already far past the goal of the AC/heatpump but because of the insulation the Heatpump spends extra effort to recondition the internal air instead of just exchanging air with the outside of the home. What if that could be automated as well.

If Tesla could leverage their Heatpump tech to solve any of these problems, energy efficiency could would be much higher and more energy would be left over for charging cars.
 
Curious what your power/$$$ savings have been since the switch over.
Really hard to tell because: Higher rate, removed all gas appliances, added a second fridge. And I can't go back far enough to get the last "stable" year.
Screenshot 2023-05-29 at 11.28.01.png
 

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Several of these "hurdles" are weird to me, as a Texan.

Perhaps in EU (and in older areas of North America, to be fair) you are looking at heat pumps to replace traditional heat sources for heating water for use in radiators, in floor heating, and such, rather than heating the air that flows through the central AC system.

For those of us with a central AC system, with ducting all over the place, we already have our heating and cooling systems intermixed, with regular AC systems having an evaporator either just before or after whatever the heat source is (i.e. electric resistive, natural gas). So switching to a heat pump involves replacing the AC system, and if you don't replace the furnace/blower unit, you also slave the old furnace to the heat pump for "emergency heat".

Many already have heat pump systems for heat, from when their house was built (or when they last replaced the entire heating/cooling system) in which there is likely still a resistive heat element as "emergency" heat (for faster warm up and/or if the outside temp drops below operating conditions for the heat pump), and the evaporator and condensor basically switch roles as the AC system runs in "reverse" to pump heat from the outside in, rather than outside in. AC systems are, after all, heat pumps - just traditionally one directional. "Heat pumps" are generally bidirectional heat pumps (or at least, one directional, but switchable, depending on how you want to define it).

So complaints about noise (we already have noisy outside compressors for cooling), space (it takes up the same space, more or less), piping (might sometimes require a change but usually can get away with the same piping, and even then most such houses aren't that hard to change out the refridgerant piping for), vibrations (our outside compressors/condensor/fan units are usually installed on concrete pads, sometimes with extra padding between the pad and the unit, which is typically separate from the house slab or other foundation support), and power draw (we already have high power connections for the AC, we're just running in reverse, so it's the same power more or less), sound weird from my perspective.

However, if you're in an area that never uses central AC, with at most quieter mini-splits or possibly nothing, and primarily needs heating, then that's certainly some potential for disruption I suppose, if you can solve the pain points for buildings that never had central AC. I'm not sure that Tesla has anything other than a willingness to engineer new solutions as an advantage, though, since they're not really inventing anything new, just packaging it smarter, with regards to heat pumps.

Other than as yet another premium expensive thing they can sell to higher end homeowners (i.e. like power wall and solar roof), I don't see much of a market for a Tesla branded central air system in competition with traditional central AC.

Perhaps they might be able to come up with a new way of doing things as a replacement for non-central air systems that use heated water or such to transport heat, but the way everything would scale up, to support a house sized load, and the lack of alternative heat sources to scavenge (even if you could scavenge heat from the stove or whatever, that's not useful to the stove's operation, and if the purpose is heating, then it's already helping heat it's immediate vicinity).

I suspect for that scenario, at best, they might provide a premium outdoor unit that is quieter than the competition, and possibly a bit smaller or at least packaged differently (i.e. a tall rectangle rather than a large cube), to address the concerns you listed as being problems for getting one in your locality. Assuming they intended to re-use their existing designs, by going from AC to HVDC to drive ~400V heat pumps (but upscaled), you'd be adding extra inefficiencies in the conversion from AC to DC, so the HVDC compressor would need to be more efficient than a traditional one run from AC. Perhaps the efficiency might be gained as the average over time, by being able to run at different speeds.

But I do think you've raised an interesting point of discussion - we don't all think of the same thing when we think of heat pumps and heating (or cooling) a building. Some of us expect central air, and a heat pump is just a fancy AC unit that can run backwards, and other than the cost to install the unit there's no material difference between them. Others, such as yourself, clearly have a different expectation, whether due to being a different climate, different local regulations, or so on. So there may be different markets better suited to different solutions, and thus a potential Tesla system (or systems, to address different markets), will have different competitive advantages (or lack there of) depending on what they're competing against, and trying to achieve.

When we discuss these things, we probably need to be clear as to what type of system we're envisioning, or half of us are going to think the other half are nuts and vice versa. :D
I do have a 45 year old house with a electrical resistive heating system with 18 kW in the basement. The heat is transfered by a loop system to radiators in the house. I was a few times in the US and I can understand that it sounds very strange for you to live without AC.
Where I live there were about 3 hot days per year with temperatures over 30 °C from 1870 to 1980. From 1980 to 2000 5 days and from 2000 to 2020 10 days. So here it is the other way round, when I talk to „experts“ that I want to cool the house with the heat pump, they find this idea very strange because is is not common here. Most people don‘t extrapolate.
 
No I don't because I understand it's useless to try and move small amounts of heat from various sources around a house.
Okay, so what you mean is that it's a simpler problem if you don't actually try to solve it. I agree that if you classify a problem as unsolvable then what's needed is nothing at all. Simple! Sounds like exactly what legacy auto has done for decades for heating/cooling in vehicles. Now Tesla has shown them up for chumps.

I doubt very much that Tesla will ever get into doing home HVAC unless they have a good solution to offer. Elon just fires people who tell him that "it can't be done".
 
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I do have a 45 year old house with a electrical resistive heating system with 18 kW in the basement. The heat is transfered by a loop system to radiators in the house. I was a few times in the US and I can understand that it sounds very strange for you to live without AC.
Where I live there were about 3 hot days per year with temperatures over 30 °C from 1870 to 1980. From 1980 to 2000 5 days and from 2000 to 2020 10 days. So here it is the other way round, when I talk to „experts“ that I want to cool the house with the heat pump, they find this idea very strange because is is not common here. Most people don‘t extrapolate.
Tricky bit about heat pumps, especially for people like you with resistive heaters, is that they are far cheaper to run for heating than said resistive heaters.

In the U.S. (and probably other places) there's this rating, called SEER (for Seasonal Energy Efficiency Rating). It's used for both air conditioning and heat pumps both; what it generally denotes is the ratio of heat energy moved into or out of a building divided by the energy used to move that heat. Typical SEER ratings are 15 and up; 24 isn't unheard of.

So.. If you're using 18 kW to heat your house in the winter (well, maximum, sure), how would you like to use 1 kW, instead, to heat your house? And how much money would that save you over a few seasons?

20 or 30 years ago in the U.S. heat pumps/air conditioning systems were generally used in places like Florida, for when the occasional below freezing cold front would come through and scare the heck out of the orange tree growers. Those heat pumps weren't all that great and at 20F (-6.7C) they had a hard time keeping up. Modern ones can handle -20F without much trouble and are used all over.
 
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Tricky bit about heat pumps, especially for people like you with resistive heaters, is that they are far cheaper to run for heating than said resistive heaters.

In the U.S. (and probably other places) there's this rating, called SEER (for Seasonal Energy Efficiency Rating). It's used for both air conditioning and heat pumps both; what it generally denotes is the ratio of heat energy moved into or out of a building divided by the energy used to move that heat. Typical SEER ratings are 15 and up; 24 isn't unheard of.

So.. If you're using 18 kW to heat your house in the winter (well, maximum, sure), how would you like to use 1 kW, instead, to heat your house? And how much money would that save you over a few seasons?

20 or 30 years ago in the U.S. heat pumps/air conditioning systems were generally used in places like Florida, for when the occasional below freezing cold front would come through and scare the heck out of the orange tree growers. Those heat pumps weren't all that great and at 20F (-6.7C) they had a hard time keeping up. Modern ones can handle -20F without much trouble and are used all over.
You may be conflating SEER and COP.
SEER is for cooling and is BTU/hr / W/hr .
1 Wh=3.4 BTU.
COP = SEER*0.293

Best HP has a SEER of 33
Highest SEER Heat Pump Revealed [2,126 Units Studied]
Best heat pumps max out at around a COP of 4.5: 1 unit of energy in, 4.5 units of heat out.

SEER vs HSPF vs (S) COP Heat Pump Ratings - How to Compare
 
Now what if the DC power for that DC Heatpump does not come from the grid but from your power walls that also collect DC from your solar and the only loss is when converting from power wall to the home for the rest of the load?

See Tesla heat pump / HVAC (non auto) Thread #60 for more detail musings and further discussion (my homes spec/how things could be different / how Tesla could jumpstart new tech in DC home appliances / ...)
Would necessitate adding an external DC bus to the Powerwall, the Tesla solar inverter equipment, etc...

But I actually think that would be great. I've always found it a bit silly that everything goes back to AC before turning into DC again (i.e. charging the car from a powerwall), but I understand this makes permitting and such much easier, even if it's less technically cool and lower efficiency.

I know some solar panels have inverters built in, does Solar Roof output DC or AC? Might be another thing that needs changing to create this shared DC power bus future.

But it would be pretty neat if Powerwall, Solar, the possible future heat pump/HVAC units, and a "DCFC" interface (with each power wall being only up to providing 7kW continuous, not going to be really faster than a good AC L2 unless you have several, but more efficient, probably) could all be tied together to a common DC bus, with either a single AC/DC unit to connect them all to the rest of the power system (the grid and the house).

If you wanted to be real fancy, maybe two AC/DC units, one to grid tie, one for the AC loads of the house - this would let you have always-on battery backed power with zero switching time when power fails, as it would be in an active AC to DC (to AC for AC loads) state all the time. Great for datacenters and people who don't mind paying a slightly higher power bill (which is probably lower than it would be thanks to solar, anyways...)
 
Would necessitate adding an external DC bus to the Powerwall, the Tesla solar inverter equipment, etc...

But I actually think that would be great. I've always found it a bit silly that everything goes back to AC before turning into DC again (i.e. charging the car from a powerwall), but I understand this makes permitting and such much easier, even if it's less technically cool and lower efficiency.

I know some solar panels have inverters built in, does Solar Roof output DC or AC? Might be another thing that needs changing to create this shared DC power bus future.

But it would be pretty neat if Powerwall, Solar, the possible future heat pump/HVAC units, and a "DCFC" interface (with each power wall being only up to providing 7kW continuous, not going to be really faster than a good AC L2 unless you have several, but more efficient, probably) could all be tied together to a common DC bus, with either a single AC/DC unit to connect them all to the rest of the power system (the grid and the house).

If you wanted to be real fancy, maybe two AC/DC units, one to grid tie, one for the AC loads of the house - this would let you have always-on battery backed power with zero switching time when power fails, as it would be in an active AC to DC (to AC for AC loads) state all the time. Great for datacenters and people who don't mind paying a slightly higher power bill (which is probably lower than it would be thanks to solar, anyways...)
The vehicle DC voltage is different from the solar DC voltage is different from the Powerwall battery's DC voltage. There will alway be conversion losses. AC lets things interoperate and AC breakers are also less expensive.

An online UPS, grid AC -> DC(battery) -> AC Loads carries double conversion losses all the time.
 
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All energy to the fridge is waste heat.
Efficency is how much energy is required to
  • transfer energy from the food to the room (which itself is also waste heat, until food is removed)
  • cancel the heat gain due to imperfect insulation
Any appliance's usage becomes waste heat in a closed system (other than endothermic cooking processes)
Since this discussion was fragmented between 3 threads I'll respond again here.

Yes you are correct, so $80 worth of waste heat per year at $.20/kWh or $.22 per day, i.e. still very little.
 
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DC heat pump isn't that special. Eg4 makes a mini split that is DC and AC, it can be powered directly from solar panels.

 
French buying for cooling rather than UK buying for heating?
Government subsidies/grants in England are way behind what’s available in Europe.
When looking at energy costs when running either a condensing gas boiler or an ASHP the price of electricity in the UK is a prohibiting factor as to why people aren’t having them installed.
With electricity 3 x the price of gas, and SCOP’s running at 3.4-3.6 then there’s no real difference.
 
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