You must log in or register to comment.

wwarnout t1_jef8ye5 wrote

How do supercritical CO2 heat pumps differ from conventional ones?


youreblockingmyshot t1_jeffctb wrote

The PSI is much higher on the coolant. Makes the unit more expensive and require a little more engineering. However it does make it so it can heat things much better. Like bringing water to just below boiling which normal heat pumps don’t do as efficiently/ at all.


Eokokok t1_jefp6rw wrote

It does not work more efficiently though - it offers higher end of output range but it has pretty bad efficiency cycle overall, specifically bad on low input (outside) temperatures.

No idea why everyone is so excited about those, given most building would benefit more from actually getting more thermo work done and not just changing the energy source in the first place for something that is not particularly efficient in the first place...


netz_pirat t1_jeg57p7 wrote

Eh, obviously not able to talk about other houses, but we went from 26000ish kwh worth of heating oil to 18000ish kwh of heat from the heat pump that is generated by less than 5000 kwh of electric energy. At least a third of that is supplied by our solar roof.

I don't think there is any thermo work that would reduce energy consumption of our house by like 90%.


Eokokok t1_jeg69n0 wrote

Great work done in worst order possible. Since obviously you are proud enough of it to come here with it you won't insulate. So you are still wasting money. And if you insulate your pump will have issues being significantly too big.

So no, you should insulate first either way, unless you have 700 square meters that would justify that energy need or live in Anchorage.


netz_pirat t1_jegdq60 wrote

You have to realize that people have limited money. Of course the best way to go would have been to buy the house, insulate the roof, the walls, change all windows and the heating at the same time.

But we can't afford that. So we start with the point that saves us the most money, is mandated by the government and subsidized by 50%.

At this point, we have costs for heating of about 1500€ a year. Upgraded roof insulation could bring that down to 1000, but would cost approx. 30k so it would pay for itself in 60 years at current prices, at that time I am 97. Walls have a similar ROI, Windows are worse.

Well insulate the roof when we redo the tiles, we'll insulate the walls when we renew the paint,... And when we are done with that, we probably approach end of life of the heat pump anyway.

Oh, and by the way, energy efficiency class C(after renos) or D (before the renos) is nowhere near as bad as you claim it is.


AcademicGravy t1_jeg2jjd wrote

It's exciting because of the refrigerant that is used. Most modern AC units use 410-A. Switching to CO2 is better in case the unit leaks gas (410 A has much higher global warming potential)


Eokokok t1_jeg35d6 wrote

Most modern, as in currently sold lineups of home range units, systems use R32, which has significantly lower impact than 410a while not being dreadfully inefficient in low temperatures...

So no, switching to CO2 is not really a way to go, it never was, is might be a great idea to sell heat pumps for users that need high temp, but those should not really be using heat pumps in the first place most of the time so yeah, great thing.


AcademicGravy t1_jeg3vvj wrote

R-32 is 675 times worse than co2 in regards to GWP. I would say that is a significant improvement. Also 410-A heat pumps are capable of heating down to -25 C so not really dreadfully inefficient in low temperatures.


Eokokok t1_jeg5f1f wrote

You have no idea how heat pumps work, do you...

I run installation company. I sell heat pumps for a living. I'm certified home and industrial heating/cooling systems technician. And with this intro CO2 pumps suck.

To put it simply - your average 10kW unit can produce that 10kW at output water temp of 35C and outdoor temp of 7C, CO2 lineup is sold with different 'scaling' so to speak, so it might get that 10kW output at 7C outside for water of 70C, but because it's inefficient it won't have COP of 4 but more in the range of 2,4-2,6.

And at -7 your normal pump gets still ~8,5kW of heat output but CO2 will get like 6 or less... And COP nearing standard electric heater. Even for not max output temperature.

Let me say this again and again - if you need a high temp pump you should insulate your building in the first place. Than buy low temp pump. If you don't have money for both you should insulate your building first and not waste time and money for high temp pumps.

So what is presented as great environmental move is just wasting limited resources on marketing gimmick that avoids addressing main issue being outdated building standards for insulation and heating installation.


AcademicGravy t1_jeg9kgz wrote

I am a red seal refrigeration and AC mechanic with 10 years of experience and I own my own HVAC company. I'd like to think I have a pretty good understanding of heat pumps.

I merely stated the purpose of using co2 over other refrigerants, I don't think you can argue co2 has a much better gwp than alternative gases.

I agree houses should be better insulated first before installing a heat pump. There is no high temp or low temp heat pump, I assume you mean installing a heat pump with higher BTU capacity vs using a smaller system.

A COP of an electric heater would be about 1. I've never heard of a heat pump with that bad of a COP lol.

Surely you know R-22 was considered a better gas than 410-A yet we switched for enviromental purposes. It may be the case that we do it again. It's not that big of a deal and I'm not really sure why you seem to hate the concept so much. Even if a co2 unit is less efficient the net effect on the enviroment is probably going to be positive, especially if we can focus on solar and other clean ways of producing electricity.


Eokokok t1_jegawli wrote

CO2 is better than other things GWP-wise, true, but it has no place in home installations given everything about it.

There is one place where it makes sense, system which accounts for probably most lost refrigerants while not caring about efficiency that much - car AC/pumps. And guess where they not actually use it forcing proprietary garbage 1234f...

So if CO2 is to be pushed for environmental reasons it should be used were power and efficiency is less of an issue than leaks, but hey, it's never about environment in the first place is it...


AcademicGravy t1_jegcukk wrote

Consider if every home was heated with a co2 unit. In that case there would be a lot of potential leaks but since it's co2 it's not that big of a concern. The units wouldn't be as efficient but if all our electricity was produced with renewables it wouldn't really matter.

If every unit was R-32 than yes it might be more efficient but leaks could cause some damage to the climate.

Tough to say for sure which one would be better for the enviroment but I think end goal currently should be co2 heat pumps and solar panels on every well insulated house. Don't think we have a better set up enviroment wise right now than that.


rafa-droppa t1_jeg9drv wrote

To me the interesting idea is industrial uses.

Take steel making for example, you have molten iron at one stage, then at a later stage you water cool it.

With further engineering you could pump the heat from the water cooling stage to heat the container of molten iron.

Obviously we're a far way from using heat exchangers to melt iron, but the point is if you can work out something like a preheat so you're heating the iron to 200F before melting it you can use a lot less energy, plus you save energy and water from the water cooling process.

So if you could reduce energy used in steelmaking by like 10% and water by 20% - that would be huge globally.


Kaeny t1_jegjvnp wrote

Is specifically bringing water to just before boiling the hard part due to temp controls or because physics?


youreblockingmyshot t1_jeh40fp wrote

Physics. Very energy intensive heating water and the compressed CO2 is better at dealing with the demand to get the water hotter.


ReddBert t1_jefhjpp wrote

Greenhouse factor of 1 (by definition), which is much better than current fluids (propane is coming up, which has a factor of 3 which is very good compared to the other fluids).

It is non-flammable and can be used indoors (unlike the above mentioned propane).


Mazzaroth t1_jeg8isx wrote

>Supercritical CO2 heat pump

This is a good article describing what is a sCO²


peadith t1_jeffk6c wrote

At a minimum, Way higher static pressure.


AcademicGravy t1_jeg2x9h wrote

Static pressure is usually used in the HVAC world as a measurement of air pressure within ductwork. I'm not sure if you mean the high side pressure of the system in this case maybe?


peadith t1_jegg2fk wrote

It would be a practical physical condition of operation, not jargon. What is the low side pressure of these systems when running?


AcademicGravy t1_jeh0dvv wrote

I guess I'm just trying to say if you are referring to the pressure on the high side of a refrigeration system using the term static pressure is very confusing. The low side pressure of these systems would differ depending on the conditions the system are in. The temperature of the air going over the coil for instance would change the pressure. The static pressure in the ductwork would also be a factor on the operating pressures of the low side.


skedeebs t1_jef6c3r wrote

I think this is great news, but I am very skeptical of attempts to predict the future based on "at current rates." Sure, at their current pace, my Washington Nationals would lose 162 games this year. They will lose a crazy number of games, but not that many.


myspicename t1_jefngop wrote

All relationships are linear! - Shitty financial and science journalism


Wizofchicago t1_jegxrrq wrote

I honestly haven’t been on a project that didn’t have them in over a year


DisasterousGiraffe OP t1_jeexlmi wrote

"In Europe, heat pumps enjoyed a record year, with sales growing by nearly 40%. In particular, sales of air-to-water models, which are compatible with typical radiators and underfloor heating systems, jumped by almost 50% in Europe. In the United States, heat pump purchases exceeded those of gas furnaces."


FuturologyBot t1_jef2ae2 wrote

The following submission statement was provided by /u/DisasterousGiraffe:

"In Europe, heat pumps enjoyed a record year, with sales growing by nearly 40%. In particular, sales of air-to-water models, which are compatible with typical radiators and underfloor heating systems, jumped by almost 50% in Europe. In the United States, heat pump purchases exceeded those of gas furnaces."

Please reply to OP's comment here:


rayhoughtonsgoals t1_jeff6qx wrote

But they are proving to lead to incredible running costs without buildings being ready or installation and design expertise beyond that hats available to many in places like Ireland.


II-TANFi3LD-II t1_jegxu7o wrote

Meh, gas is still currently more cost efficient. Unless you find yourself with excess free electricity from you're solar - reliably throughout the year, heat pumps will cost more to run.