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Heat Pumps – The Well-Tempered Future of A/Cs

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Re: Heat Pumps – The Well-Tempered Future of A/Cs

#241

Post by danans »

northwest65 wrote: post #234
ashayh wrote: post #232

The article mentions the most important point towards the end: “The better you insulate, the less heat you need in the first place,” No heat pump will help if your house is leaky or under insulated.

Sure they can, you can absolutely use heat pumps to brute force it, been there done that.

Not only that, but since a heat pump is at least 3x as energy efficient as the most efficient gas furnace, using one results in about 1/2 the E2E CO2 emissions as the gas furnace when the grid electricity being consumed is natural gas based. If you live in an area with abundant zero emissions electricity, then you are heating without any C02 emissions at all.

That said, we should do both heat pumps and insulate better.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#242

Post by tcfhgj »

Alupis wrote: post #194
Maxion wrote: post #188

Earlier quoted context omitted.

> It seems to me, there is no future where a heatpump can be the only source of in-home heating then. > > 1) Natural Gas is vastly cheaper in most/all of the US. > > 2) Homes still require an alternative heating source when temperatures drop to low levels (coincidentally when people need heating the most). > ... > I must be missing something here... Yes you are, your natural gas subsidized, i.e. government handout, i…

> Yes you are, your natural gas subsidized, i.e. government handout, i.e. you're not paying the real market cost. > Your energy grid is shit, which is why your electricity price is so high. Adding a heatpump solves this issue, or makes it worse?

Heat pumps power consumption can be modulated by energy providers and improve grid power stability.

In Germany you get way cheaper electricity prices if you allow this.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#243

Post by JumpCrisscross »

xattt wrote: post #214
chongli wrote: post #206

Earlier quoted context omitted.

We got a system for around $10,000 Canadian. But then there was a $5000 rebate. These things are quite expensive. I think the HVAC installers are making a large commission though. The actual equipment costs much less than that.

I have a sneaking suspicion that green rebates are being exploited by historically shady businesses (contractors and car dealers) by baking in the cost of the rebate into the final price. There’s a local lot with a used 2021 Ioniq with the usual “used car dealer” hand-lettered sign proclaiming the $5,750 provincial rebate. I’m also fairly certain the car had its price inflated by that much by the dealer, or will clim…

It’s naïve to assume 100% of a subsidy will fall on a consumer, though delays between purchase and subsidy help in that respect.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#244

Post by fomine3 »

simonblack wrote: post #142
jillesvangurp wrote: post #97

Earlier quoted context omitted.

This persistent myth just needs to go away. People use heat pumps all over Scandinavia, including in the arctic circle. They are extremely popular there. They were early adopters of this technology there decades ago. There are two popular varieties: - Ground source heat pumps. Those work pretty much anywhere; just dig below the perma frost and you are good to go on the northern tip of Canada, Alaska, Norway, or where…

Ditto Australia. We've been using 'reverse-cycle air-conditioners' for heating in Australia for decades. I'm puzzled as to why there is any debate at all on their use for heating. A heat-pump is far more efficient for obtaining heat than direct resistive heating using electricity. Many houses here use no other form of heating at all. And then at the press of a button, we get cooling in summer too. What's not to like?…

Heat pump dryer system is state of the art for efficiency. I saw some complains by American that it takes too long time for drying, but I don't know why they need to dry things so frequently.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#245

Post by ori_prior »

danans wrote: post #241
northwest65 wrote: post #234

Earlier quoted context omitted.

Sure they can, you can absolutely use heat pumps to brute force it, been there done that.

Not only that, but since a heat pump is at least 3x as energy efficient as the most efficient gas furnace, using one results in about 1/2 the E2E CO2 emissions as the gas furnace when the grid electricity being consumed is natural gas based. If you live in an area with abundant zero emissions electricity, then you are heating without any C02 emissions at all. That said, we should do both heat pumps and insulate bette…

Your numbers are off. Thermal power plants typically do have a thermal-to-electric efficiency of around 30% (40% max), so with your heatpump having an electric-to-thermal efficiency of an assumed 300%, you end up with basically no difference in CO₂ emissions.

Note that there are some misleading efficiency claims for gas plants around 60%, but those are not for thermal-to-electric efficiency but for generating electricity plus district heating from waste heat.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#246

Post by shusson »

cornstalks wrote: post #4
nottorp wrote: post #3

Isnt any a/c a heat pump though?

Yes, but typically “heat pump” is used to mean it can provide heating too, whereas standard “A/C” is a “one-way” heat pump that only provides cooling.

Interesting, I’ve never heard of that interpretation. Heat pumps have always been a technology to me. The same tech that is in everyone’s refrigerator.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#247

Post by sokoloff »

tharkun__ wrote: post #235
newZWhoDis wrote: post #224

Earlier quoted context omitted.

Almost certainly. Proper/modern heat pumps do not need heat strips until -20F or so

Agreed. Ours is at least 5 years old if not more now and was way cheaper. That said there is a difference between mini-split and something you hook up to internal ducting where your furnace used to be and prices have increased in the meantime. That said there was basically no difference in putting in an A/C only unit vs a combination. Technology wise it's the same so to speak just running in reverse in winter vs summ…

Mechanically, there’s a reversing valve and defrost elements and controls to turn an AC into a heat pump. (So, it’s small, but not zero, mechanical differences.)

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#248

Post by coderenegade »

nerdbert wrote: post #211
samtho wrote: post #49

Earlier quoted context omitted.

An A/C works almost identical to your refrigerator. Using a closed loop of refrigerant with specific thermal properties, it will remove heat from one side and emit heat from the other. If you are able to run this system backwards, you could in theory swap which side is a heat sink (the cold side) and heat source (the hot side). While a traditional A/C cannot do this, heat pumps can electronically switch which side of…

> Fun fact, a resistive heating device is a rare case of something being 100% electrically efficient in that all the energy it uses will be turned into heat My understanding is that you get considerably more heating per watt-hour with a heat pump than with resistive heating, though. I get that it's not creating that heat but moving it, but still that seems like even more efficiency from the perspective of energy cons…

The coefficient of performance of a heat pump isn't a measure of thermodynamic efficiency, because as you pointed out, a heat pump moves heat rather than creating it. That's why you get more heat per Watt-hour, because you aren't expending energy trying to make heat.

The closest analogy that I know of is in electrochemical processes where some of the energy input is allowed to take different forms. If you put in 85 units of electrical energy, 15 units of waste heat from a different process, and get 90 units worth of product, your process is 90% thermodynamically efficient, but has better than 100% electrical efficiency. In the case of a heat pump, measuring units of heat per Watt-hour is a bit like this in that some of the input energy (for the heat generation) has already been provided by a different process.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#249

Post by spiderice »

ashayh wrote: post #232

The article mentions the most important point towards the end: “The better you insulate, the less heat you need in the first place,” No heat pump will help if your house is leaky or under insulated.

You’re describing my situation. How do you de-leakify a house?

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#250

Post by Marsymars »

Phrodo_00 wrote: post #127
wcfields wrote: post #55

Earlier quoted context omitted.

Have to imagine that the niche market for making 40F/4C "cold" water from luke-warm tap water (if you live in an area that is so hot the tap water is warm) is fairly small.

Every fridge with a cold water tap is literally this (in addition of being a fridge and a freezer, obviously)

My Frigidaire fridge doesn't seem to have a water reservoir, so the water dispensed is room temperature. (And eventually tap-cold temperature.)
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