General > General Technical Chat
What is the real story around heat pumps?
Siwastaja:
--- Quote from: Marco on February 23, 2024, 09:19:52 am ---Defrost circuitry can be very stupid.
--- End quote ---
"Circuitry" might be a wrong choice of words in 2000's because it's software on a microcontroller. Circuitry is almost always pretty much the same, outdoor air temperature sensor + evaporator coil pipe temperature sensor.
There are three classes of defrost logic:
(1) Very stupid, which works
(2) More sophisticated, which still hopefully works
(3) Those that fail more often than once in a blue moon
The simple and reliable baseline is just following the temperature difference between outdoor air and evaporator coil pipe. Once the evaporator is blocked by ice, it gets internally colder and colder, which triggers defrosting, which runs until evaporator coil temperature exceeds some high threshold (e.g. +40degC or something) - after the ice has melted, evaporator temperature rises quickly.
Stuff like minimum and maximum time between defrosts is usually added. It doesn't need to be rocket science, and while fancier solutions could provide small COP advantages by defrosting just at the right time, the risk of doing it way too often or way too rarely increases with complexity.
tom66:
Don't actually expect to "win" any debate on this forum regarding climate change or renewable energy. Goalposts shift, data is ignored, ears are plugged, bullshit is spread. We are heading for climate catastrophe because most humans are fundamentally selfish and cannot conceive of problems outside their immediate interests. Or because that people can't comprehend existential threats. Whatever it is, it's not good.
nctnico:
--- Quote from: tom66 on February 23, 2024, 07:37:02 pm ---Don't actually expect to "win" any debate on this forum regarding climate change or renewable energy. Goalposts shift, data is ignored, ears are plugged, bullshit is spread. We are heading for climate catastrophe because most humans are fundamentally selfish and cannot conceive of problems outside their immediate interests. Or because that people can't comprehend existential threats. Whatever it is, it's not good.
--- End quote ---
Well, you have to define those 'existential' threats. IMHO the threats are way overblown as the earth and humanity have seen far worse events (like massive vulcanic eruptions, meteorites and ice ages). With today's level of technology there is a lot more the human race can do to remedy effects than ever before. I've been around long enough to notice the climate is changing myself (while carefully keeping in mind that memories typically compress the time frame). I've also been around long enough to know humanity can put serious and effective measures into place to remedy and reverse damage done to the environment. IOW: don't worry too much, it will be OK.
Siwastaja:
--- Quote from: tom66 on February 23, 2024, 07:37:02 pm ---Goalposts shift, data is ignored, ears are plugged, bullshit is spread. We are heading for climate catastrophe because most humans are fundamentally selfish and cannot conceive of problems outside their immediate interests. Or because that people can't comprehend existential threats. Whatever it is, it's not good.
--- End quote ---
In the end, UK remains one of the few outliers where natural gas is 1/4th of the price of electricity. But most of the Earth's population uses heatpumps just fine, because they are hugely popular in most of Asia. Only in the UK, and to some extent, US, heatpumps are conspiracies and scams and whatever. 95% of the planet has no problem with them at all.
In this discussion again heatpumps are being compared with PV. I have to again note that both are fundamentally similar, they suck freely occurring energy delivered to us by the big lightbulb called the Sun. The exact pattern is slightly different, and because heatpumps do something PV does not, namely harvest solar energy stored within the planet, and I mean not only stored overnight, but also in annual timescale, it is highly valuable, and the value compared to using e.g. li-ion batteries to do the same time-shifting is many orders of magnitude better. The limitation of course then is that the output comes in form of heat, so it can't do everything, but it totally can replace low-temperature heat that would be produced in some other way.
coppice:
--- Quote from: Siwastaja on February 23, 2024, 07:45:34 pm ---In the end, UK remains one of the few outliers where natural gas is 1/4th of the price of electricity. But most of the Earth's population uses heatpumps just fine, because they are hugely popular in most of Asia.
--- End quote ---
So, where in Asia are heat pumps popular for heating? There are many millions cooling homes in hot climates, but very few of those are reverse cycle and can heat a home.
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