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How a heat pump works

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Re: How a heat pump works

#251

Post by elil17 »

nicoburns wrote: post #55
nashashmi wrote: post #16

Earlier quoted context omitted.

They are not more energy efficient than burning gas. Edit: since i am getting downvoted to oblivion, let me fight back here. I genuinely wished heat pumps would be more efficient and in theory they can be. I would love to not generate heat and just use the outside heat energy and compress it down into a smaller location. But compressing and decompressing is not an energy efficient task. It takes a lot of work. Mechan…

Well of course when talking about efficiency you have to specify what you are being efficient with respect to: what's most energy efficient might be different to what's most cost efficient which might be different to what's most carbon efficient. Cost is going to vary greatly on the electricity and gas prices in your area, so it's hard to give a definitive answer there. With regards to energy efficiency, my understan…

Yes, heat pumps do win. They win even more when you consider that the energy mix is not 100% fossil fuels. Globally something like 15% of energy comes from renewables or nuclear, plus 20-ish % from natural gas which is, as you said, 50-ish % efficient in turbine power plants.

Re: How a heat pump works

#252

Post by elil17 »

sbradford26 wrote: post #135
snuxoll wrote: post #104

Earlier quoted context omitted.

> this is a no brainer in milder climates which is why I have a heat pump and no gas furnace here in FL even though I have gas to the house for other uses. They're a no-brainer in every climate. Newer heat pumps can handle fairly cold temperatures (-13°F) pretty easily, there may be a loss in efficiency but in the majority of the world it doesn't stay that cold. A few days of lower than normal efficiency, and at wors…

So heat pumps do lose efficiency at lower temperature such as -13F but the much bigger issues is loss of capacity. If you look at the curve of available heating capacity of a heat pump versus the heating needs for your house that tend to be a bit of a mirror image. When it is warmer out your house needs less heat but heat pumps have the highest capacity they will have. As temps drop the house will require more heat w…

In cold climates, systems have backup electric furnaces.

Re: How a heat pump works

#253

Post by Volundr »

rootusrootus wrote: post #237
bobthepanda wrote: post #211

Earlier quoted context omitted.

They are also kind of a 2 in 1 appliance, in that they can run in reverse and cool your home, and are much more efficient at that than traditional ACs. In the US where AC is common, summer is generally peak electricity usage. I suspect this will become true in Europe as well with the heatwaves becoming a regular occurrence.

> they can run in reverse and cool your home, and are much more efficient at that than traditional ACs. I'd love to see a source on that. There is very little technological difference between an air conditioner and a heat pump aside from refrigerant reversing valves that allow changing which end is the condenser and which the evaporator.

A heat pump is an air conditioner that can run in reverse. Put another way, an air conditioner is a marketing term for a specific kind of heat pump. Your correct that there is no inherit efficiency different. Perhaps what was meant is that they are much more efficient than traditional resistance heating?

Re: How a heat pump works

#254

Post by Kirby64 »

rootusrootus wrote: post #237
bobthepanda wrote: post #211

Earlier quoted context omitted.

They are also kind of a 2 in 1 appliance, in that they can run in reverse and cool your home, and are much more efficient at that than traditional ACs. In the US where AC is common, summer is generally peak electricity usage. I suspect this will become true in Europe as well with the heatwaves becoming a regular occurrence.

> they can run in reverse and cool your home, and are much more efficient at that than traditional ACs. I'd love to see a source on that. There is very little technological difference between an air conditioner and a heat pump aside from refrigerant reversing valves that allow changing which end is the condenser and which the evaporator.

I think as a general statement it's true, however the causal reason for that is not because they're heat pumps, it's because of the market for heat pumps is different.

If you poll the current installed base for HVAC, I suspect you'd find that the (vast) majority of systems are minimum SEER rated (i.e., least efficient) systems, so SEER 13/14 (just became SEER 14 this year).

In comparison, if you're already paying the premium for the heat pump system, likely you also pay an additional premium for a higher SEER unit. Also, what I've seen when doing some online shopping that most heat pump systems marketed seem to be higher SEER. Likely, because the cost associated with additional heat pump stuff drives into a higher end market where you 'might as well' make them higher SEER as well (with inverter compressors, variable fan speeds, etc).

Re: How a heat pump works

#255

Post by WatchdogReset »

boringg wrote: post #7

What is going on? Is there a global push to get everyone to switch to heat pumps. It seems that there is heat pump content everywhere. Clearly there is a push. I understand that its for climate benefits but it feels very coordinated. edit: didn't realize the attention I would get. Let me add someone answered my question -- a good product market fit and people talking is probably where the push came from. That said HV…

My two cents, I just tried to show this free course on my site, because heat pumps are an interesting topic. There is also others courses like this : https://hvac-learning.com/courses/air-handling-units-technol...

Heat pump as every heating or cooling devices, have pro and cons. This is where HVAC knowledge is nice to have, in order to have the best solutions. For example, the maintenance / obsolescence are an under estimated point when it comes to environment and savings

Re: How a heat pump works

#256

Post by ccooffee »

scrollaway wrote: post #246
ccooffee wrote: post #206

Earlier quoted context omitted.

> even captain planet cartoon showed air conditioners being bad for the environment That seems like it was a useful simplification for a children's cartoon, but things aren't that black-and-white. 1. Without air conditioning (or some other method of cooling and humidity control), almost all high-occupancy buildings would reduce their effectiveness as a work-place or living-place. OSHA has guidelines about office temp…

Are cooling blankets a thing? Like, a not-a-scam thing?

I don't know how well they work. I have a sibling with one that they use frequently, but that sibling is a bit odd. (I think the blanket circulates water through it, but I've never really asked.) Their use may just be due to a placebo-esque effect.

Re: How a heat pump works

#257

Post by kenmacd »

vikingerik wrote: post #214
Nihilartikel wrote: post #132

Earlier quoted context omitted.

If I can spend 1 joule to transfer two joules of enthalpy from outside to inside, then that is 200% efficiency. Burning 1 joule of gas would give you 1 joule of heat in a perfect world. That is what a non pump does.

Where exactly does that first spent joule go, thermodynamically speaking? Is it also converted to heat within the electromechanicals of the heat pump?

To add to the other answer, if you calculate the absolute limit on performance for heating and cooling using the Carnot cycle, the 'heating' case is always going to be '1' higher than the cooling case, because you also get to use the 'work' heat.

Re: How a heat pump works

#258

Post by nicoburns »

titannet wrote: post #228
gabrielhidasy wrote: post #65

Earlier quoted context omitted.

They literally are more efficient than burning gas, a good heat pump can do over 300% efficiency (KWs of heat in your house vs KWs of electricity used) while a furnace can only hope to get 100%. Even if the heat pump is fed from gas power plants (which burn gas with about 50-60% efficiency, more if the waste heat is reused), they are still using less gas for the same amount of heat than directly burning it.

If that where there would be no discussion about the switch to heat pumps. But it isn't. In old houses (bad insulation, old radiators) and edge cases ("winter") heat pump are not just inefficient they may not be able to heat the house at all (unless extremely oversized). This is a huge problem in Europe where a house is expected to last a 100 years, in many areas much more.

It's true that good insulation and sufficiently sized radiators are important. But it's not like those things can't be upgraded in existing houses. In fact, if we're talking about energy efficiency then insulating houses should likely be the first action taken.

Re: How a heat pump works

#259

Post by LazyMans »

energ8 wrote: post #244

I have seen repeated claims of heat pump CoPs improving over decades. Can anyone summarize or provide links to what improvements are being made? Compressor technology? refrigerants? Fans to move heat? all of the above? Where is the path from here?

I can provide a likely incomplete summary of the improvements.

Compressors themselves have gotten much more energy efficient, although I'm not sure the impact on CoP is all that great since and waste heat from the compressor is being deposited in the home anyway. Variable speed compressors are the most efficient you can get pretty much.

Refrigerants have improved in someways, but not really in others. Since heat pumps could be running with exterior temperatures that are quite low, with the system under pressure, some refrigerant blends would have less than desirable vapor pressures leading to problems running in very low temperature conditions. For the most part, the changes to refrigerant blends have been related to their Global Warming Potential (GWP).

Expansion valves are a very important piece of a refrigerant loop, these used to be fixed orifaces. Nowadays these are dynamic, meaning they can increase efficiency of the system by metering the flow based on system load and other characteristics. These are called TXVs or Thermostatic Expansion Valves. Electronically controlled expansion valves are now hitting the market further increasing efficiency.

Finally there is the design of the interior and exterior coils. I dont think materials have changed much, but the surface area has changed. You may noticed a 2 ton unit from 1997 is about 1/4th the size of a 2 ton unit from 2022. More surface area on the coil for the exterior unit lets you extract more heat from the air without burning a ton of energy running the fan super hard.

Interior air handlers have probably improved some as well, variable speed motors, etc. Variable speed really is nice because you can get much more consistent temperatures in the home and wont get blasted in the face with heat from vents when a regular system cycles on and off.

Re: How a heat pump works

#260

Post by Freestyler_3 »

energ8 wrote: post #244

I have seen repeated claims of heat pump CoPs improving over decades. Can anyone summarize or provide links to what improvements are being made? Compressor technology? refrigerants? Fans to move heat? all of the above? Where is the path from here?

refrigerants (though some regulations have negative impact on this), Optimizing (DC motors and computers with sensors figuring out what is the best setting), Absorbing waste heat from the process, Insulation, Materials that stay more clean or self clean.
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