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| What is the real story around heat pumps? |
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| m k:
--- Quote from: Zarhi on February 23, 2024, 08:26:26 am --- --- Quote from: m k on February 23, 2024, 07:46:00 am --- --- Quote from: Zarhi on February 22, 2024, 08:53:28 am ---That's is situation with air source heat pumps from this morning: Outside temp 2°C, humidity about 60%, clear sky, no rain, no clouds, no fog. Pictures taken 3-4 minutes after defrost cycle completion. --- End quote --- Looks can be misleading. The structure is what it is because air is not dense enough that lesser surface area would be enough. Actual operation happens between refrigerant and inner wall of the pipe. So the machine doesn't know that there is frost, generally it only knows that compression is fine or not. Condenser/evaporator can be insufficient when general operation changes from the normal sufficient operation. It can still be fine with visually not so fine looks. --- End quote --- Evaporator was fully clogged, no air passes at all. And fan operates at very high speed. In this situations heat pump works with COP slightly under 1. Heat dissipated in compressor are transferred to inside unit. Power needed for fan is lost. --- End quote --- Do you know defrosting periods between different humidity levels? Here air-to-air machine is now using 400W and easily maintaining +21C indoors when outdoors is +1C and humidity being >95%. Some visible frost has accumulated but operation of the machine is stable and unchanged. When humidity goes up the efficiency of radiation process goes down but it also becomes more powerful per square. If pump ignores that it may overuse the situation. But changing 0C water to 0C ice is equal to 80C temp difference of liquid, so having sort of ice on top of the surface is not a straight forward thing. |
| coppice:
--- Quote from: Siwastaja on February 27, 2024, 07:38:00 am --- --- Quote from: coppice on February 26, 2024, 08:27:01 pm ---Which Chinese unit do you have? --- End quote --- Amitime which I think is the second largest heatpump producer (after Gree). These large Chinese companies know how to get the basics quite right, they are not super sophisticated designs but then again a heatpump doesn't need to be. Whenever there are technological innovations that actually improve COP or performance (like inverter drive or EVI), first premium brands use them, then a few years later all the cheap ones adapt them too and make a big deal about it in their marketing, and then a few years later again it's just standard stuff and everybody forgets to even mention such technical details. --- End quote --- I don't know where Amitime are in the rankings, but I think they are quite small compared to Gree, Midea and Haier. The big guys have the volume to finance the R&D to both performance improve and cost reduce their designs. An overly complex design is is something of a red flag. Midea is a big brand name, but they also make heat pumps that carry other big names, like Toshiba and Carrier. Haier products carry various names, but I think they are names they own. --- Quote from: Siwastaja on February 27, 2024, 07:38:00 am ---You can clearly see air-to-water heatpumps are still quite niche compared to the ubiquitous air-to-air units which are better optimized for mass market. --- End quote --- I think that is compartmentalised. Until recently the main market for air-to-water heat pumps was big commercial systems, and I think those should be quite mature. Consumer heat pumps have been mainly air-to-air heat, and mostly cooling only. That market has been highly optimised. The growing market for reverse cycle and heat only models is gradually getting those optimised, too. |
| m k:
--- Quote from: m k on February 27, 2024, 11:28:45 am --- Here air-to-air machine is now using 400W and easily maintaining +21C indoors when outdoors is +1C and humidity being >95%. Some visible frost has accumulated but operation of the machine is stable and unchanged. --- End quote --- I left and upped the target temp 1C, came back few hours later and indoor temp was heading to 22.5C and machine used 1770W. Dropped the target down 1C, no real operational change and room temp kept rising. After an hour or so later indoor temp is near 23C and machine is using 1100W, outdoor temp being a bit above zero and humidity over 95%. After few minutes of defrosting indoor temp meter says 22.5C and next cycle start using 960W, bit later it's 1200W. Now indoor temp is 22C, pump is chilling and using 236W, outdoor temp is probably under zero and humidity around 90%. Few log things. We have 3 different m3 styles, thrown, piled and solid. Our last piled qubes were 80EUR, first more mixed and later more pine. Here dry piled m3 of birch is said to have 1700kWh and pine 80% of that. Once we chopped an oak and a maple, not big. Those were very difficult to burn, oak practically didn't burn by its own. Maple was burning but needed a hot base. I also had free wood once. We collected what harvester left behind, the area was some hundred meters aside and wet. Collected trunks were chopped with a guillotine style cutter with a claw for splitting, nice thing but can't do too thick trunks. Putting in a bent trunk can also be a bit bad for nearby flesh. For me chopped logs were too long so I had to still cut them afterwards, the pile was also there, in the woods, so some hauling was necessary. Just for the sake of it I estimated how much the big pile would have been cost if sold, it was over 100EUR/m3 a long ago, at least a double now. Most of the time was used for collecting trunks, it took many days even when tractor collected small piles to big pile, but good exercise anyway. I'd say that free can be pretty relative. |
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