https://arstechnica.com/science/2024/07/the-hunt-for-the-most-efficient-heat-pump-in-the-world/
A new generation of engineers has realized they can push heat pumps to the limit.
A new generation of engineers has realized they can push heat pumps to the limit.
"These installers are reaching astounding levels of efficiency by taking extra care to design low-temperature heating systems that warm rooms without using excess energy."
I'd at first really like to find a plumber that does not look at me as if I was an alien creeping out of mud when I tellem that if the central gas heater breaks down completely I want a heat pump. There's really hard conservativism in that business here.
I live in a progressive state in the US and currently renovating a house. Holy crap they all fight me tooth and nail telling me what a horrible idea they are. Nothing but problems, always break, oh my goodness what if the power goes out, the grid cannot handle the load so don't do it. These old timers need to go away.
oh my goodness what if the power goes out
...then your gas or oil heater doesn't work, either...
Their point is use a small generator to power the gas heater where as a heat pump is 'impossible'.I mention a whole house battery is in my 5 year plan to which they laugh and say your house will burn down. I don't have the patience. I told them I'm an electrical engineer specialized in battery systems and to let me worry about the lithium fires. That shut him up fast.
I designed my heating system around a fairly efficient non-condensing NG boiler that takes 40W for the fan. I can run it and the circulators off my battery bank no problem, and handle a sustained power failure. But only because of the natural gas.
I've been integrating a water-water GSHP into it to provide summer cooling and a supplemental heat source from my solar panels. It works well, but in my climate (Rural Canada) I would be insane to completely remove my gas boiler IMO. Heating demand is just way too high on the sort of days where the power goes out. I've been working on plans for a wood boiler but insurance has put their foot right down on anything that burns wood in the last couple years.
Here in Canada we can't get lithium at a reasonable price so I have 10kWh of lead-acid (which as you know is actually 5). Doesn't go very far on a cold winter day with 4 hours of sun and snow on the panels!
On the upside I haven't had to hook my generator to my house in years, I'm really happy with my "grid-independent" system.
During last winter gas heater servicing I told the plumber to set the unit to 50°C heating water output so I could check if the heaters would get warm enough with a heat pump. 1,5 hours of discussion about old buildings and heat pumps resulted till he complied.
It was just a test setup that could be reverted any time.
I ended up figuring out how to do mine myself with a Mr Cool kit when the furnace died due to the fact that every hvac guy believed a 4th gen heat pump would be useless in the northeast us. It gets down to about 0F here once or twice a winter and the heat pump starts struggling to keep up around those temps but it still does its job.
Whoa, that's f* cold, but with your feedback I'm quite positive all this doomsday feedback I got can be ignored. Problem here is I'll be respnsible for uninterrupted heat and warm water for my tenants, too, so doing these calculations alone, for myself, would not bother me. But there's a ton of responsibility to care for the tenants, and I'd like a professional up for the challenge.
Are you in my state? HVAC peeps had little to no idea about heat pumps and claimed they were $20,000 to install and only rich people had them.
I would like to have someone installing the thing who is motivated like the folks in the article. Motivation=good work=probably an efficient system. But these seem to be hard to come by here.
"New generation of engineers" is a bit cringe. The old generation knew thermodynamics pretty damn well. All that's changed is they're using R290 refrigerants and variable speed compressors now, but those don't change anything from a physics perspective. COP is fun but it's not even the right metric to use from a policy perspective, just like MPG. And despite being unitless, COP suffers from the same exagerative effect as MPG numbers. What matters is the carbon associated with delivering BTUs to a home, so here you can have the ridiculous case of delivering more BTUs at a higher carbon cost achieving a higher SCOP than the same exact heat pump delivering fewer BTUs at a lower total carbon cost achieving a lower SCOP for a better insulated home, and the person with the higher SCOP bragging about it like a clown. At least when the government tests COP it's a standardized test so you can actually compared equipment (somewhat).
Regardless, nerds gonna nerd and no harm done (and I also track real time energy use of my heat pump, so I consider myself a nerd).
“New generation of engineers” is a bit cringe.
a new sense of urgency is more like it.
What really matters is the wattage needed to cool the space. That's really it. The less energy used, the less the strain on the grid, or the less solar capacity needed.
Wattage is power, not energy. But I still generally prefer carbon as a metric because that's the climate issue, so by focusing on it directly we can make more informed decisions. It also incorporates time of day/seasonal (peak) impacts implicitly, which also have profound effects on the grid, more than total energy used. The essence of our comments is the same though.
Not sure where you're located, but there are often significant incentives for heat pumps. If you're US and low/moderate income, there are big programs ramping up via the IRA that will cover a large percentage of the costs, assuming you're not in a total brain dead state.
Can you not afford an air conditioner? A heatpump is only marginally more expensive
For under $500 one can get a window heat pump. (They are likely as shit as the $200 window A/C.)
I own one. It's mounted in the wall not in a window but it's a unit that can be used either way. We have central heat and A/C but our heat is a gas furnace. We have an addition that wasn't on the central system and that's why we have the wall unit heat pump/AC. It works pretty well as long as it isn't bitter cold outside (-20 C/ -4F isn't too rare). Also that addition has terrible insulation. (edit to add that the addition also has an ancient gas heater built into one of the walls but it hasn't been used in decades. It has been tested though, it still works but it is scary.)
So I'm pretty happy with that heat pump and it is probably much more efficient than a space heater. But if I was really broke and just trying to survive a hot spell or a cold snap I'd more likely buy a $180 AC unit and a $20 space heater unfortunately.
Where? My $300 U shaped window AC is modern quiet, tidy and efficient, but I was reading about window heat pumps being $2-3k.
My wall mounted split systems were <$1000 AUD each, 3.5kw. Found a sparkie and a fridgie to do the install, set us back around $3000 for two systems installed.
Great units, added some wifi dongles and tied them into my home-assistant for remote / out of home control & scheduling.
Probably the best addition to our home currently, don't know how we lived here using pedestal fans and gas heating.
Well all conventional air conditioners are strictly heat pumps, but when we say heat pump everyone usually means bi-directional heat pumps - ones that can provide heating as well as cooling. My Amazon results are not that and I was recently reading about them coming to market starting at $2k.
This one is $449 and clearly states several times it can heat with a heat pump.
Maybe it is full of shit. I cannot say.
I saw 5 for air-air and was impressed. Then I see SCOP? Oh please. Why not change the scale again to make sure nobody knows what a good value is. Just like SEER on an air conditioner.
SCOP varies depending on environmental conditions!
Real COP or go home IMO. Watts out/watts in, no fudging numbers to confuse consumers again.
I'm just surprised there's no "AI heat pumps" yet.
Now that's something the world is really needed. (/s)
https://www.sciencedirect.com/science/article/pii/S2352484722012021
AI is the new rule 34.
Artificial intelligence (AI) models for refrigeration, heat pumps, and air conditioners have emerged in recent decades. The universal approximation accuracy and prediction performances of various AI structures like feedforward neural networks, radial basis function neural networks, adaptive neuro-fuzzy inference and recurrent neural networks are encouraging interest. ... Thus, complex multi-objective problems that require high precision solutions to optimize the cost and performance of ideal RHVAC are solved using artificial intelligence techniques (Mohanraj et al., 2012).
Granted, this is modeling, not implementation, but.
"Heat pump" is just the latest buzz word. If you look up how they work its literally just a regular air conditioner with a switch to reverse the air flow.
Compressing refrigerant, allowing it to absorb thermal energy from inside the house, pumping that refrigerant to an outside coil where it releases that energy, then compressing again. This is air conditioning.
Not saying it's not useful or whatever. But it's not some incredible new technology. You could accomplish the same functionality by installing your window unit backwards.
At the time of writing, real-time data suggests that for every kilowatt-hour of electricity Ritchie’s heat pump consumes, it delivers 5.5 kilowatt-hours of heat—a coefficient of performance, or COP, of 5.5.
You can easily almost double that if you're willing to break the pump in a few years.
But usually that's more expensive per BTU/other heat unit because the pumps are expensive. That's why I asked.
Double would be a COP of over 10. That's a stretch for an overbuilt GSHP and not even slightly feasible for air-air.
High COPs are usually easy on a compressor as they represent low compression ratios and low differential temps. For example I can hit around COP 7 in cooling on my scrap heap GSHP, with an evap temp around 10C and condenser temp around 20C. That's a high side pressure around 100 psi and only 30 psi of differential, "barely working" as far as the compressor is concerned.
The only way I know to get high COPs is to have an oversized condenser and a way to get your refrigerant below ambient, like evaporative, ground source or overnight radiant so you can get the compression ratio down, unless you know a secret in which case I'm not afraid to burn out a compressor or two trying it out!
I don't rember the details of how it works. I think it just reduces the torque or something? Maybe it doesn't work on newer pumps or they already do it.
Oh I think I know what you're talking about, abusing a minisplit by idling the inverter back too far. Effectively you have a hugely oversized condenser for the tiny flow, under the right conditions like a cool night you can get ridiculous subcooling.
But COP is irrelevant in this case because you've derated the actual BTU to near zero, you aren't moving any refrigerant.
Also yes this will kill your compressor because the minimum speed is set where it will get enough oil flow. Run it too slow, and it won't pick up oil and eventually seize up. You also could end up running the suction in vacuum which is also hard on compressors.
