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

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

#271

Post by ori_prior »

philipkglass wrote: post #263
ori_prior wrote: post #257

Earlier quoted context omitted.

60% is feasible for e.g. nuclear and gas, if you use more than one turbine and there is a big constant temperature differential. This typically isn't the case for gas plants which are intentionally variable and often intended to be cheap to build. While at peak temperature, they might run at peak efficiency around the theoretical maximum of 60% (thermal to electric) with a multi-turbine assembly, typically efficiency…

I don't think that any nuclear reactor has achieved 60% thermal-to-electricity efficiency. In a water cooled reactor the hot side starts with cooler steam than a combustion-fired plant can generate so it's hard to reach really high efficiency. Reactors cooled with helium, molten salts, or liquid metal could theoretically do better but I don't think that any actually-built power reactors have reached 60%. The brand ne…

No, you are right, 60% is a theoretical maximum achievable maybe with supercritical reactor coolant. The actual maximum for existing reactors is somewhere just below 40%.

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

#272

Post by rapjr9 »

aurizon wrote: post #92

These gradient comfort guys want $5000 for an 8000 btu unit with a total weight of $150 pounds. Compressor and heat exhaust hand outside. Evaporator and fan/control hang inside, It has a SEER rating of 10. There are dozens of minisplits for $1000 that have a SEER from 19-24. I can see no reason why a close coupled mini split with a 1" armored electrical/freon joint could not be made. This is what a gradient comfort i…

This seems to be a much more reasonable unit, 10,000 BTU, does both heating and cooling via a heat pump, and it costs $700, although there are a lot of negative reviews:

https://www.amazon.com/dp/B09ZCZSSV8

$5000 is ridiculous for the Gradient Comfort 8000BTU window unit. The Soleus is the only other heat pump window unit I've seen for sale. Midea makes some A/C's that are more efficient because they use an inverter, but they don't do heating. There seems to be a market failure here, given that a bidirectional heat pump shouldn't cost much more than an air conditioner you'd think everyone would prefer a heat pump, especially since it would lower cooling costs and can do lower cost heating in the winter. But nobody is selling them at reasonable cost and quality. They could include a heat exchanger also to bring in fresh air without losing energy. But nobody makes such a thing. Maybe the barriers to entry in this market are high for some reason? Window air conditioners have always kind of sucked (too noisy, encourage mold, uneven distribution of cold, crummy temperature control). I wonder why. It seems wrong.

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

#273

Post by hedora »

spiderice wrote: post #249
ashayh wrote: post #232

The article mentions the most important point towards the end: “The better you insulate, the less heat you need in the first place,” No heat pump will help if your house is leaky or under insulated.

You’re describing my situation. How do you de-leakify a house?

I would start by blowing insulation into the exterior walls (assuming they don’t have any), and insulating the attic. Also, upgrade the windows to double paned or better.

Fixing unintended holes in exterior walls is probably also reasonably safe.

However, randomly plugging intended leaks without understanding how the house is supposed to breathe can lead to condensation issues (mold and rot), carbon monoxide poisoning (if you have natural gas) and radon poisoning (if that is a thing where you live).

If you want to do more than I mentioned above, consider hiring an architect, or reading up on house ventilation designs.

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

#274

Post by MivLives »

ashayh wrote: post #232

The article mentions the most important point towards the end: “The better you insulate, the less heat you need in the first place,” No heat pump will help if your house is leaky or under insulated.

The worst is when you rent. I live in an area that doesn't really expect much cold or heat. All the windows are single paned. The sun beating on the roof raises the top floor to the outside temperature plus 5 degrees. I can't fix any of it because I'm only here for a few years.

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

#275

Post by xenadu02 »

nsxwolf wrote: post #193

When I needed a new air conditioner a couple years ago I was quoted $17,000 for a heat pump. I can only guess at that point whatever energy cost savings it would bring would never be realized within the service life of the system. I went with a $6000 standard replacement AC unit.

Unless the installer was ripping you off those were not comparable units. I've seen the manufacturer MSRP sheets and the cost difference between heat pump and non-heat pump for the same unit is small. Nowhere near enough to account for $11k.

It sounds like they quoted you a bottom of the range 11 SEER A/C vs a top of the line multi-stage compressor variable speed blower 19 SEER heat pump system. Those are not the same thing.

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

#276

Post by [deleted] »

jillesvangurp wrote: post #119
__MatrixMan__ wrote: post #115

Earlier quoted context omitted.

I've been on zoom calls with two separate co-workers who are all bundled up because their heat pump can't handle the weather. It doesn't mean that the technology is inadequate in principle--probably their systems have some problem that competent HVAC installers know how to avoid. But its an unfortunate fact that there are places in the US where installers that recommend heat pumps can't be found for 100 miles. It doe…

Gas outages happened at a large scale in Texas when they were struggling with a bit of cold weather. When they needed it the most, it failed them. Coal plants also struggled. Both had challenges with supply of fuel and cooling water being disrupted. That kind of systemic infrastructure failures is on the rise in the US. There are all sorts of reasons why governance just isn't great in the US. But the reality indeed i…

[deleted]

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

#277

Post by nightski »

sokoloff wrote: post #255
__MatrixMan__ wrote: post #115

Earlier quoted context omitted.

I've been on zoom calls with two separate co-workers who are all bundled up because their heat pump can't handle the weather. It doesn't mean that the technology is inadequate in principle--probably their systems have some problem that competent HVAC installers know how to avoid. But its an unfortunate fact that there are places in the US where installers that recommend heat pumps can't be found for 100 miles. It doe…

> heavy snows cause power outages in places where tree limbs fall on overhead lines. If gas outages happen... well I've never experienced one. If I lose power, my gas boiler does me no good. A gas boiler will use pumps (and likely a power vent). A gas furnace will use a fan and a power vent.

It's a lot easier to keep a gas furnace running on a generator for an extended period of time than a heat pump.

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

#278

Post by nightski »

Maxion wrote: post #188
Alupis wrote: post #135

Earlier quoted context omitted.

It seems to me, there is no future where a heatpump can be the only source of in-home heating then. 1) Natural Gas is vastly cheaper in most/all of the US. 2) Homes still require an alternative heating source when temperatures drop to low levels (coincidentally when people need heating the most). So, even if a heatpump is technically more efficient in terms of emissions, the technology does not solve all of the probl…

> It seems to me, there is no future where a heatpump can be the only source of in-home heating then. > > 1) Natural Gas is vastly cheaper in most/all of the US. > > 2) Homes still require an alternative heating source when temperatures drop to low levels (coincidentally when people need heating the most). > ... > I must be missing something here... Yes you are, your natural gas subsidized, i.e. government handout, i…

Heat pumps might work at -40c, but all the efficiency gains are lost and it's going to cost a fortune.

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

#279

Post by zacharycohn »

cwkoss wrote: post #164
zamalek wrote: post #155

Earlier quoted context omitted.

Are you sure you aren't getting quotes for a ground-sourced (AKA geo) heat pump? We just installed a 4.5 ton (overkill for your sqft) 20 seer unit for $18000.

I got a very similar quote ($27k for ~2000sqft home) in seattle a few months ago. Salesperson said there is excess demand for both labor and machinery for heat pump installations in the past few months. I wondered at the time to what extent this is a regional phenomenon (seattlites are nerds who like energy efficiency) vs. supply chain issues vs. a sales technique. Interestingly, I learned that it will be too cold fo…

Let me guess - Greenwood? They came in 40-50% above all the other quotes I got.

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

#280

Post by notyourwork »

MivLives wrote: post #274
ashayh wrote: post #232

The article mentions the most important point towards the end: “The better you insulate, the less heat you need in the first place,” No heat pump will help if your house is leaky or under insulated.

The worst is when you rent. I live in an area that doesn't really expect much cold or heat. All the windows are single paned. The sun beating on the roof raises the top floor to the outside temperature plus 5 degrees. I can't fix any of it because I'm only here for a few years.

This is something to consider for a future rental property.
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