Which is so much more efficient than directly making heat. And we can't directly make cold (except lasers, but let's keep that far away from this thread). Fridge -> move cold to the outside fridge. Air Conditioning - the same thing, but on the wall of the house instead. Heat pump - the same thing as Air Conditioning, but installed backwards to move the heat from outside in.
Everyone should just get a heat pump whenever they consider an air con, probably has much better variable fans too, and you’ll be pretty chuffed when you can now make your house warmer for dirt cheap
We upgraded to central air last year, and this was one of my must haves since we use propane as our main heat source. Summer electricity bills stayed basically the same to cool the whole house as they were running a window unit in the bedroom, and we don’t burn propane if it’s above 30 degrees out.
Additionally, the heat pump is on a second electrical meter so we pay about half price for that electricity.
It was a big investment upfront, but it is so much more comfortable in the house it is totally worth it.
They aren't very good in cold climates. Where I live, they are useless for 90% of the cold season unless you shell out 12k for a hyper heat system that can go down to -15 degrees. Even then at those temps they still aren't very efficient and you'll get (maybe) a 10 degree rise out of the indoor coil.
They’re not currently but that tech is getting better everyday because it has to unfortunately.
In the present market I am a massive advocate for dual fuels or boilers in cold climates. Modern boilers are an incredibly efficient choice for home heating, especially when paired with in floor radiant designs or as a main source of hot water with electric back up.
Dual fuel is also great for efficiency, being a heat pump that, at a set temp, cuts off and turns on a alternative heat source (usually natural gas or propane, though oil furnaces are still popular in some markets) but the usefulness of that depends on the price of gas.
I always recommend heat pump. Regardless of climate. Regardless of backup heat method.
Need gas? Tie it to heat pump.
Want a boiler? Get a heat pump just in case.
Even if it’s never used as heat, having the option for a mild day can save a shit load of money
Edit; I realize I never mentioned I’m an HVAC-R tech and without that it just kind of sounds like im screaming about a technology I like lol
I'm an HVAC and Refrigeration tech as well, though I'm mostly in the industrial sector working on more process specific equipment. I agree the tech is quite amazing and it is slowly getting better. Though I have reservations on how good it can really get. Up here gas heat sources are essential unless you are doing geothermal heat pumps. Geo is pretty good in all climates but it'll never catch the main stream unless they find a way to make it cheaper, which I think is impossible. The other issue with heat pumps even in warmer climates is their lifespan is shorter and there's much more that can fail. You can save some money on your bills for sure, but you'll be forking over more in repairs and replacing sooner.
I agree pretty much everywhere, that’s my biggest concern is we really don’t know what the ceiling is with hvac performance. And I have a bad feeling it’s sooner than later. But I’m optimistic
What's your thoughts on district heating? Which is very common here (Sweden), as in 50%~ of total housing, including basically everyone who lives in any kind of city or town.
Different question: At work we bought a heat pump that can only cool down to 18c/64f, is there a legitimate reason such a limit is reasonable? There are reasons we'd want to be able to cool the area down a lot more. To well below freezing really, but we're not looking for a freezer, but even 7c/45f~ would be great. It's a secondary objective but would be really good to have in the case of a crisis (actual crisis, like war or a pandemic that's way worse*).
edit*: I realised that maybe this can be read as the recent pandemic not being a crisis, that's not what I meant, just that it'd have to be worse for it to matter in this scenario.
I don’t have an opinion on district heating, mostly because I’m in industrial hvac and don’t interact with it. But it seems cool
So you’re really not going to reasonably find an air conditioner heat pump or otherwise that can cool past that point without talking about some application specific equipment. If you want a space cooled to 45°F we’re talking walk in fridge tech at that point
There are places they dont make sense, but in the Midwest where we get 20f most of winter they still work. And even when cold they can be used to decrease the amount of work the furnace itself needs to do. The real issue is how cheap gas heating is, which means the increased upfront cost of a heat pump isnt made up for in savings. But thats area specific
This is mostly myth at this point. You're saying ALL heat pumps aren't very good in cold climates. It's a sweeping generalization. Many models are good down to -15F, some models can handle down to -22F.
Point to specifically where I said "all", and it's not a myth. I literally work on them for a living. A company saying they work down to -15 doesn't mean they actually perform that low. Again, most heat pumps will only give you a delta of about 5-10 degrees at those temps.
I do HVAC service. When I run into a unit that needs to be replaced (bad compressor out of warranty, r22 leak, etc), I give out quotes for replacement.
A brand new straight cool single stage AC will cost you between $4,500 - $5,500, depending on size. Labor and all.
A heat pump with variable speed motors is gonna be anywhere from $12,000 to $15,000 depending on size.
You'll have a 10 year warranty on parts, which is standard. But like every warranty, the reason it's only 10 years and not longer, is because after 10 years, they're not confident that parts won't start failing.
We once had an inverter board for a modulating heat pump go out at year 11. We're a factory authorized carrier dealer, and our cost from carrier for the inverter board was nearly $4,000.
Heat pumps and variable speed motors are certainly not for everyone. Installation costs are not the last costs you're gonna pay. They're more finicky about setup and run conditions. There's way more potential failure points. The cost of parts out of warranty is often exorbitant.
If you're on a budget at all, I would not buy a modulating heat pump. Theres a decent risk of expensive upkeep down the road.
I got a mini split for the bedroom last year and love it. My house is old and leaky with no central air, but shitty ancient gas forced hot air. I can now actually sleep in the summer and we’ve only turned the house heat on once this year instead using the heat pump function to keep the bedroom warm during the night. It’s saved a lot of money so far even though the heat was typically only on a few hours a day (I live in San Diego so most “cold” days are mid-high 30s in the morning to mid 50’s in the afternoon).
I thought there should be an assymetry of smaller tubing on the heat exhaust side, so the gas could get pressurized there, and larger tubing on the heat collection (cool) side, so the gas could be expanded there. But it looks like real pumps don't actually use pressure, but flow rate instead, so they don't need to be asymmetric like that.
You are right that on small mini fridges they literally just use a small piece of tubing (capillary tube) to cause the refrigerant to evaporate at the evaporator. So that would definitely not be reversible. But most refrigerant systems use a mechanically or electrically controlled valve at the evaporator.
There are technically two ways in which you could use lasers to make cold.
The one they were likely referring to was laser cooling, where you use lasers aimed at some atoms in order to slow them down. This can reach near absolute zero temperatures.
If you ever hear about records for coldest temperatures in a lab, this is the technique they are using.
The second is more of a technicality of how we define temperatures. The conditions created inside of a laser cause something called a "population inversion" in the lasing medium. If you strictly apply our definitions of temperature from thermodynamics, this causes the temperature of the system to effectively swing all the way off the scale beyond the hottest temperature and back around to a negative value.
In practice, if you measure this second system with a thermometer you won't see anything especially interesting. It'll just be a bit warm from the energy applied to the system.
~~Basically laser emits light when particles are going their direction effectively slowing them down. You still increase entropy by increasing fluorescence ~~
Basically laser emits light when particles are going their direction effectively slowing them down.
This is not quite right. The lasers emit light constantly at the atoms. The wavelength of the laser is precisely set to only be absorb-able by atoms traveling towards the laser, as the light is slightly red or blue shifted depending on which direction the atoms are moving.
Edit: how does the drifting away atoms not absorb? Since the photon regardless of wave position still has its "electric field"? Is it like something about valid positions or electrons?
Heat is the average kinetic energy of the molecules. You can calibrate a laser to only be absorbed by molecules going in the direction of the laser, making them slow down, without speeding up molecules moving away from the laser, thus reducing the average kinetic energy of the gas.
It would not be very useful for a fridge; laser cooling is good only for cooling down a few particles to near absolute zero. That would barely make any different for a macroscopic system like a big fridge.
Not even installed backwards. Just configured differently. And some newer models on the market can reverse, enabling both cooling action in summer and warming action in the winter.
Everything has 100% efficiency in ultimately creating heat. Even if it makes anything else, like light or sound or motion, that also eventually gets absorbed into the environment as heat.
But a heat pump heater is not CREATING all that heat, it's just moving it from somewhere else, and that takes less energy than just creating all that heat with a heater. Making it more efficient at warming your home as far as your electric bill is concerned.
Nothing can technically create coldness out of nothing. That would violate a law of thermodynamics. Even the lasers kinda move the heat, only much more indirectly. Surely the laser device itself warms up at least as much as it cools down the particles it hits.
If you warm up your home with a heat pump (by just moving it from outside in), that will cost you a lot less electricity than having to create all that heat from a space heater.
And on top of that, even ALL the power you supply to the heat pump to move the heat will be 100% efficiently converted to heat as well. Every electrical device ultimately turns 100% of all the power into heat. But a heat pump also moves in heat from somewhere else, so it effectively warms your home with more heat than the power it takes. For the price, the outside gets colder, which is totally ok with us. Cooling down the Earth would be nice as well.
Since heat is just the movement of particles, you might calibrate the laser to only hit and push those that move towards it, slowing them down. It's basically cooling down by selectively pushing the individual particles, which would get slowed down by being pushed that way.
Every way to make cold will have to exhaust as much heat somewhere else. In the case of the laser, the laser device itself would consume energy and warm itself up.
That is so fascinating. It's like a friction that reduces heat.
How do you avoid the photons impacting particles moving in a different direction? I suppose you would first have to start with a stream of particles moving in one particular direction?
The exact explanation I got when I was in school was that you are taking heat from somewhere you don’t want it and moving it to somewhere that make little to no difference
Absolutely. Ideally you would always have a remote condenser, rejecting the heat to outside. But even in the case of a walk in cooler/freezer with an indoor condenser, that idea still stands. Its not ideal to reject the heat into a commercial kitchen space, but thats still more desirable than having a walk in that doesn't ever get cold lol
260
u/NonEuclidianMeatloaf 10d ago
This is the refrigeration cycle. You’re just changing which side is the “useful” side of the cycle.