- cross-posted to:
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I like the idea and presentation, but I feel like he’s leaving out an important factor in heat pump technology.
The amount of energy used is based on the change in temperature on each side of the pump. So in a scenario when you’d need to actually heat a room, it will be extremely cold outside. So in order to heat a room, you would need to cool the outdoors by a proportional amount. The thermal mass of the outside air is large enough that you wouldn’t actually create a noticeable change in temperature, but the cooler it is outdoors, the harder it is to get the outside condenser coils cold enough to create heat indoors.
I’m pretty sure heat pumps are still more efficient than heat generators when it comes to residential climate control, but the levels of efficiency he’s measuring in this demonstration are not typical the efficiency in real-world conditions.
Modern heat pumps retain their efficiency down to pretty low temps, around -10 to -20 C AFAIK
I’m pretty sure heat pumps are still more efficient than heat generators when it comes to residential climate control, but the levels of efficiency he’s measuring in this demonstration are not typical the efficiency in real-world conditions.
Efficiency definitely drops as the temp difference increases, but at least with modern heatpumps, they generally can remain 150 to 200% efficient (compared to resistive heat) all the way down to -22f (-30c), based on this study which has a short summary available over on Wired.
For most of the world, it either doesn’t get down to those temperatures at all, or only does so for a relatively brief time. So for the majority, the sort of efficiency he’s demonstrating in the video is fairly accurate to what people who can afford the top-teir models from Mitsubishi would be able to achieve most of the year.
For less expensive heatpumps that aren’t rated to be as efficient at colder temps, they should still be able to achieve roughly 300% efficiency when averaged over an entire season (at least, basing that off of Technology Connections heat pump video and his location).
Thanks for doing the legwork on this - I was just going off my basic understanding of entropy and it’s nice to see examples of real-world experience and numbers.
I can nerd out about appliance efficiencies for days! (help), always glad to help spread the good word of that sweet, sweet COP (not to be confused with the bad type of Cop).
Tech Ingredients did a pretty great video about easily improving efficiency of solar panels by adding an enclosure and some box fans to the back of them, which seemed to have no real downsides, so I’m quite intrigued to see how he’ll drastically improve the efficiency of that air conditioner in his next video.
Nice to have it here, but due to the practical nature of the demonstration, I think this video could have flown better on c/technology or c/diy - or something of that sort. :)
But yep, moving heat is a lot smarter than creating it. :)
I figured since this wasn’t actually showing you how to convert an A/C system to be used as a heater in a practical way, and was just a demonstration of the principle/capability, c/DIY didn’t quite fit.
But I think you’re right, c/technology would be a good fit, and I’ll likely crosspost it over there in a day or two unless someone else gets to it first ^^
I want a how-to video on adding a reversing valve and control electronics to my existing HVAC.
Wouldn’t that require draining the system of refrigerant thus requiring a certified person?
Generally. They’re not add on devices. Would be cool if manufacturers had an incentive to make one but there’re too many models out there to make something universal. It would probably be custom if you could even do it at all
