Comment by pedrocr | Hacker News Reader

Comment by pedrocr | Hacker News Reader

Parent Full thread

Here's a current R32 system by Daikin:

https://www.daikin.co.uk/content/dam/dauk/document-library/d...

SCOP is at 5.15 and that's a seasonally adjusted value. So over the entirety of the winter the unit is expected to deliver 5.15 units of heat for each unit of energy. The unadjusted COP is 6.27. For this unit operational limits are listed at -15C/5F and I think there are units that go quite a bit lower. I haven't looked at that much as -15C is plenty for us. And this is with air to air. With air to ground much higher efficiencies are possible.

For cooling it's even better, with the equivalent SEER at 8.75. The improvements have been so good that the efficiency scale is already at A+++ because the A standard has been so exceeded.

If you do not have temps below 0-5°C that might be true. Below the freezing point efficiency drops quite a bit.

"Name a source please" :)

Keeping 5x over the entire winter includes some pretty cold nights. And ground source systems can improve even this by quite a bit.

Nicely played :)

Here we go: https://industrialheatpumps.nl/en/how_it_works/cop_heat_pump...

or better this pic: https://www.researchgate.net/figure/Performance-map-of-the-h...

That seems to be for a 2006 Daikin model:

> The heat pump model is based on linear interpolation in a performance map retrieved from manufacturer data (Daikin Europe N.V., 2006).

And that model is half as good as the modern one I linked:

> The nominal coefficient of performance (COP) is 3.17 at 2/35ºC and 2.44 at 2/45ºC test conditions (i.e. air/water temperature) for full load operation.

And even then it gets a COP of 2 at -15C. So modern systems getting to at least 4 at -15C seems likely. This claims there are low ambient mini splits that maintain 100% efficiency down to -15C:

https://www.ecomfort.com/stories/1341-Keeping-Your-Mini-Spli...

That should cover most places but for really cold climates ground source heat pumps seem ideal. From what I've seen there are simple solutions where a single vertical hole is drilled with common well drilling machines and a single tube that has the loop inside is driven down. Makes it easier to retrofit and implement in small properties.

Reply on news.ycombinator.com