Heat Pumps – The Well-Tempered Future of A/Cs • Hacker News Board

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#121

Post by chickenpotpie » Wed, Jul 05, 2023, 7:03 PM UTC

addisonl wrote: post #113

chickenpotpie wrote: post #110

Earlier quoted context omitted.

I understand how wet bulb temperature works just fine. You didn't need to write a snarky response to engage in this discussion. Now include climate change raising the temperature and changing the length and severity of monsoon season, continued development raising the heat island effect. It doesn't matter what the average wet bulb temperature over the entire coty over a long period of time. It matters what the peak w…

The entire south is at a much higher risk from wet bulb: https://www.iflscience.com/southern-us-reaches-dangerous-wet... so my point still stands, wet bulb isn’t an issue in Phoenix.

You didn't respond to any of my points at all. One area being at risk of something doesn't lower the risk in a different area.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#122

Post by triceratops » Wed, Jul 05, 2023, 7:49 PM UTC

wcfields wrote: post #55

LUmBULtERA wrote: post #13

Earlier quoted context omitted.

I always went with this description too, though oddly a "heat pump water heater" only works one direction, yet "heat pump" is still in its name.

Have to imagine that the niche market for making 40F/4C "cold" water from luke-warm tap water (if you live in an area that is so hot the tap water is warm) is fairly small.

It's not a niche market. Every office in the world has a water cooler.

The market for evaporative water coolers is niche, or probably only big in the developing world. Other than that water coolers use refrigeration aka a heat pump.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#123

Post by mindslight » Wed, Jul 05, 2023, 8:03 PM UTC

triceratops wrote: post #85

afavour wrote: post #72

Earlier quoted context omitted.

Heating is considerably more energy efficient than having to run ACs all over the place. And if you need to go outside when it's cold you can: you add layers of clothing. In Arizona, in the middle of summer, you could be buck naked and you'd still overheat (and get burnt, to boot).

> Heating is considerably more energy efficient than having to run ACs all over the place. That's actually incorrect. Heating takes considerably more energy. When you're cooling you're looking at a temperature delta of at most 20 degrees C/45 degrees F between outside and inside. When you're heating, it can be easily be twice that. Or even more, in parts of Canada or the Great Lakes states. Air conditioning is a heat…

> Air conditioning is a heat pump and can achieve up to 300% efficiency. Whereas most houses in cold climates use furnaces, which have at most 98% efficiency.

No. You can't directly compare "efficiency" numbers across different energy sources. My understanding is that the efficiency of gas powered electricity generation is around 33%, meaning that powering a heat pump with a COP of just under 3 will be of similar end-to-end efficiency as burning the gas directly in a condensing boiler/furnace.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#124

Post by mindslight » Wed, Jul 05, 2023, 8:10 PM UTC

londons_explore wrote: post #63

digdugdirk wrote: post #2

Well this was an oddly terrifying introductory paragraph for an IEEE article: "... half of Phoenix residents are at risk of an emergency room visit or worse if their electricity fails during a future heat wave, according to a recent study. Air conditioning is what keeps people there comfortable—and alive—a growing fraction of the year. The extreme heat already kills hundreds of Phoenix-area residents every year, a nu…

It raises the question of if we should deploy 'emergency coolers' - perhaps single-use barrels of some chemical that gets cold when a pull-tab is pulled. To be a workable solution, it needs to be more reliable/cheaper/more effective than just a regular gasoline generator powering a regular aircon unit. After a flood/hurricane/nuclear strike, they would provide enough coolness to keep people alive for a few days.

I believe the straightforward answer is to dig a hole. But it would certainly be interesting to calculate exactly how much cooling capacity you could get out of one or two 55 gallon drums of some endothermic precursors. Bonus points for being easily reversible when the electricity comes back on (like those sodium acetate heating packs).

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#125

Post by phpisthebest » Wed, Jul 05, 2023, 8:17 PM UTC

silisili wrote: post #86

phpisthebest wrote: post #59

Earlier quoted context omitted.

>>Same with cold weather, I 100% disagree with this... Heat is made by everything, waste heat is a byproduct of all modern things, and there are TONS of easy low cost ways to make heat even it is just as simple as burning something. Also the body makes head naturally so adding layers to trap this heat does not require continual inputs from an outside resource Cooling on the other hand is MUCH harder, and electricity…

For a young/healthy person, sure. But these aren't generally the at risk people in the first place. I grew up around the 38N parallel, gross enough to get too hot in the summer and too cold in the winter. Every winter people froze to death, just the same. It's not as bad as Phoenix percentage wise, but it's still a risk in the vast majority of places that people in the US live.

Of course people can and do die from cold, that was never my claim

My Claim is providing people with emergency heat is FAR FAR FAR FAR easier and cheaper than providing people with emergency cooling.

Do "at risk" people die in the north from the cold, absolutely but I am not sure how that means the cold is worse

As it stands right now, just from my daily activities my waste heat in my home makes my home about 10-15 degrees above ambient. Meaning in the winter if my target temp is 65deg, it would have to be 50 degrees or colder outside before I would even think about running my heat.

In the winter time that means my AC is working hard to not only combat the outside temp but the internal waste heat from computers, cooking, TV's, humans, etc.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#126

Post by gambiting » Wed, Jul 05, 2023, 9:11 PM UTC

jillesvangurp wrote: post #97

__MatrixMan__ wrote: post #15

I live in a colder climate where heat pumps are not popular. After talking with a number of HVAC people about this I was surprised to learn that despite being very similar to an AC system in principle, in practice converting an AC system into a heat pump system doesn't make economic sense--you end up just ripping one out and installing the other. I don't fully understand why this is the case, but I hope that there's…

This persistent myth just needs to go away. People use heat pumps all over Scandinavia, including in the arctic circle. They are extremely popular there. They were early adopters of this technology there decades ago. There are two popular varieties: - Ground source heat pumps. Those work pretty much anywhere; just dig below the perma frost and you are good to go on the northern tip of Canada, Alaska, Norway, or where…

Air source heat pumps are super popular in Poland too, this winter it was about -20C for couple weeks straight and not had any problems, toasty house without any issues. The key is that the heat pump exchanger really needs to be huge(ours is taller than a person) to get the heat out of the air.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#127

Post by Phrodo_00 » Wed, Jul 05, 2023, 9:14 PM UTC

wcfields wrote: post #55

LUmBULtERA wrote: post #13

Earlier quoted context omitted.

I always went with this description too, though oddly a "heat pump water heater" only works one direction, yet "heat pump" is still in its name.

Have to imagine that the niche market for making 40F/4C "cold" water from luke-warm tap water (if you live in an area that is so hot the tap water is warm) is fairly small.

Every fridge with a cold water tap is literally this (in addition of being a fridge and a freezer, obviously)

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#128

Post by Alupis » Wed, Jul 05, 2023, 9:15 PM UTC

elil17 wrote: post #48

nightski wrote: post #26

Earlier quoted context omitted.

The thing is (especially where I live) I'd still need a gas furnace. We regularly see -20F to -40F in the winter. While the 95% scenario sounds great, in practice still needing gas means we still need all the gas infrastructure. From my understanding natural gas burns pretty clean. The problem is leaks in infrastructure and drilling, which isn't going away because I buy a heat pump.

Although natural gas is "clean" compared to, say, coal, the advantage of a heat pump is that it uses less total energy than natural gas. That means it would be more efficient to run a heat pump off a natural gas power plant than to burn natural gas to heat your home directly.

People's AC summertime electric bills regularly get into triple-digits - it's not uncommon to hear someone with a moderately sized home having a $200-400 electric bill in the summertime.

However, even in the midst of winter, gas heating bills rarely climb above $100 monthly.

What am I missing here? It seems a heatpump, while more efficient, will cost significantly more to operate. Natural Gas is cheap... and clean enough.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#129

Post by rayiner » Wed, Jul 05, 2023, 9:21 PM UTC

jillesvangurp wrote: post #97

__MatrixMan__ wrote: post #15

I live in a colder climate where heat pumps are not popular. After talking with a number of HVAC people about this I was surprised to learn that despite being very similar to an AC system in principle, in practice converting an AC system into a heat pump system doesn't make economic sense--you end up just ripping one out and installing the other. I don't fully understand why this is the case, but I hope that there's…

This persistent myth just needs to go away. People use heat pumps all over Scandinavia, including in the arctic circle. They are extremely popular there. They were early adopters of this technology there decades ago. There are two popular varieties: - Ground source heat pumps. Those work pretty much anywhere; just dig below the perma frost and you are good to go on the northern tip of Canada, Alaska, Norway, or where…

The myth exists because the US is probably 10-20 years behind Europe and China in terms of HVAC and insulation technology. I recently had some reasonably high efficiency heat pumps installed at my house, and I’ve been very unhappy with the low temperature performance. It doesn’t even get very cold here—rarely below 5F (-15C) and a record low of -8F (-22C). The heat pumps I got (recommended by the well-regarded local HVAC company) operate at just 40% of rated capacity at 0F.[1] Meanwhile, Chinese and Japanese-made inverter driven heat pumps will happily go down to -5F at 100% of rated capacity, and -22F (-30C) at 80% of rated capacity.

[1] You can of course get a much larger heat pump to compensate, but that leaves the unit way over-sized for cooling loads.

Re: Heat Pumps – The Well-Tempered Future of A/Cs

#130

Post by web3-is-a-scam » Wed, Jul 05, 2023, 9:24 PM UTC

My 20 year old air conditioner recently died and I was looking into replacements. In my climate the temperature ranges from 40C in the summer, and -40C in the winter. After doing some research, it seemed pretty clear that having a furnace+AC was the way to go for my climate. Hardly a magic bullet technology.