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Pretty soon, heat pumps will be able to store and distribute heat as needed

sintef.no

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Re: Pretty soon, heat pumps will be able to store and distribute heat as needed

#161

Post by ifwinterco »

IshKebab wrote: post #159
Xylakant wrote: post #61

Earlier quoted context omitted.

it also reduces peak load - you can heat water up slower with a lower powered heater. I have a 35 liter warm water tank in my garden shed that pulls about 3.5kw - an equivalent on demand heater would need 14kw or more.

I don't see why that matters. You use the same amount of energy and the demand is smoothed out at grid scale (yes I know about tea in ad breaks).

Houses in the UK typically have 100A supply and the whole local grid is sized assuming people use relatively small amounts of electricity. If everyone gets an electric car and a massive heat pump, lots of local transmission will need upgrading

Re: Pretty soon, heat pumps will be able to store and distribute heat as needed

#162

Post by ifwinterco »

hedora wrote: post #10

I wonder if this can store any heat or just heat pump heat. If it can store any heat, it would help a lot to further reduce heating costs in our modern energy efficient house. Sometimes, in the winter, we get too much solar forcing, so if we don’t heat all, it can be 85F in the day in the house, but 60-65 at night. (We open the windows during the day, and don’t always close them at exactly the right time at night.)

It sounds like you need more thermal mass, a traditional brick/stone house wouldn't have that problem

Re: Pretty soon, heat pumps will be able to store and distribute heat as needed

#163

Post by darkteflon »

Tor3 wrote: post #156
manmal wrote: post #105

Earlier quoted context omitted.

Certainly not gas or oil, which are still cheaper to heat with than heat pumps.

Hm? Around here oil was never been in the same (low) order of magnitude. Those who installed oil heaters many decades ago regretted it quickly. And it's been illegal to use them for a couple of decades as well now. Gas has never been an option in my region, there's no infrastructure for that. We have used gas in Japan until now, but even that we'll be phasing out (I live in two places)

I’m in Japan too. Could you name the model you ended up going with? My heating bill in the winter is insane.

Re: Pretty soon, heat pumps will be able to store and distribute heat as needed

#164

Post by ryzvonusef »

jokoon wrote: post #154

I'm interested in storing cold, not heat Storing cold during the night is probably more efficient I thought about making ice blocks with a freezer on my balcony, probably not a good idea

Persians had a system since 400 BC:

https://en.wikipedia.org/wiki/Yakhch%C4%81l

Re: Pretty soon, heat pumps will be able to store and distribute heat as needed

#165

Post by jcattle »

5ersi wrote: post #109

It uses phase change (solid to liquid) to store heat at about 200 kJ/kg. Compare this to heating water in a boiler from 10c to 60c - stores 209 kJ/kg. So we already have an effective way to store heat which can work for decades without servicing and is also cheap to produce (in terms of money and energy consumption).

Does heating water in a boiler work well with a heat pump? How about a release of energy 10 hours later (peak solar at noon, to first shower the next morning)?

I actually don't know the answer. I'm just thinking that there must be more to it, if the answer was as simple as "just heat water".

Re: Pretty soon, heat pumps will be able to store and distribute heat as needed

#166

Post by Tor3 »

darkteflon wrote: post #163
Tor3 wrote: post #156

Earlier quoted context omitted.

Hm? Around here oil was never been in the same (low) order of magnitude. Those who installed oil heaters many decades ago regretted it quickly. And it's been illegal to use them for a couple of decades as well now. Gas has never been an option in my region, there's no infrastructure for that. We have used gas in Japan until now, but even that we'll be phasing out (I live in two places)

I’m in Japan too. Could you name the model you ended up going with? My heating bill in the winter is insane.

The model is not yet decided, we're in the finalizing stage with the building company. What we have been focusing on is a well insulated house, unlike the old one which has no insulation at all.. if we tried to heat that it would not only be extremely expensive, it's impossible to even heat the small bathroom with an electric heater. So instead you kind of get used to it. Took me a year to stop feeling like I was freezing, at 4C in the bathroom on February mornings. We have been using a gas heater (plug in the floor) in certain places on the ground floor, but we limited that as well. So, with an insulated, small house, we believe we will be able to keep the costs down, using heat pumps and heat exchangers, plus solar and battery (using the car battery).

Re: Pretty soon, heat pumps will be able to store and distribute heat as needed

#167

Post by yurishimo »

zobzu wrote: post #142
tempestn wrote: post #126

Earlier quoted context omitted.

Modern heat pumps are cheaper than oil for heating just about everywhere. They're cheaper than natural gas in most places, unless electricity prices where you live are particularly high.

in CA my natural gas is far cheaper than the heat pump sadly

In western europe today, I spend €10+ per day to heat my home (17 degrees mind you) with a gas powered boiler for radiators. I can run my mini-split on 18 degrees all day for a couple of euros. I moved here from the US in 2022 right after the full scale invasion of Ukraine so natural gas prices skyrocketed overnight.

I don't really understand what the aversion is to forced air climate control here other than "it's not as comfortable" which from what I've gleaned from other people is taken to mean noise/moving air/humidity. Coming from the southern US, I find all of those points to be a non-issue for me. I've slept with a fan on my entire life, so if I can shave off 50% of my heating costs for a few decibels of fan noise, sign me up!

Re: Pretty soon, heat pumps will be able to store and distribute heat as needed

#168

Post by globular-toast »

matwood wrote: post #67
jandrese wrote: post #62

I've been keeping an eye on heat pump water heaters for awhile, but right now they mostly make sense in warm climates. The big problem is they're still specialty products and marked up like crazy, but also they tend to use cheap components which makes them loud and prone to failure. If you run A/C for the majority of the year then they pay themselves back reasonably quick, barring early failure, but in colder climate…

I think a heat pump only for water isn't the right way to go. In the EU, new systems I see use a single heat pump for all heating and cooling in the house including heating water. I do miss my natural gas on-demand water heater from when I lived in the states though. Unlimited hot water was nice, and it took up almost zero space.

> I do miss my natural gas on-demand water heater from when I lived in the states though.

Isn't that what we call a combi boiler in the UK (and Europe?) I've recently moved from having a big hot water cylinder to a combi. The space saving is nice, but there are downsides.

Waiting for the hot water to come through is annoying and I'm often just wasting cold water waiting for it to come through hot. There is a "pre-heat" feature which would be nice, but then it would keep it warm 24 hours a day which is ridiculous. Maybe some better boilers can time the pre-heat. That would probably be close to perfect.

The other downside is it can only really supply one tap with hot water. So if someone is having a shower and someone else runs a hot tap it can be unpleasant. Requires some coordination between householders.

All in all I would definitely prefer a cylinder if I could afford the space it takes. Modern cylinders are incredibly efficient. I once turned the heating off for a week while away on holiday and when I came back the water from the cylinder was still tepid.

Re: Pretty soon, heat pumps will be able to store and distribute heat as needed

#169

Post by moooo99 »

jcattle wrote: post #165
5ersi wrote: post #109

It uses phase change (solid to liquid) to store heat at about 200 kJ/kg. Compare this to heating water in a boiler from 10c to 60c - stores 209 kJ/kg. So we already have an effective way to store heat which can work for decades without servicing and is also cheap to produce (in terms of money and energy consumption).

Does heating water in a boiler work well with a heat pump? How about a release of energy 10 hours later (peak solar at noon, to first shower the next morning)? I actually don't know the answer. I'm just thinking that there must be more to it, if the answer was as simple as "just heat water".

It does. However, the hotter the water becomes, the less effective the heatpump becomes. With anything beyond 60C becoming very inefficient.

With hot water tanks, they are unfortunately pretty badly insulated as well, with some of them loosing heat very quickly. Depending on how you plan on using that water, you also have to make sure the temperature never dips below ~60C to avoid legionella from spreading.

I actually think that heating your home slighly higher than you‘d usually do is the simplest and most effective approach, assuming it is properly insulated. Just rise the target temp for 1-2C when the energy is cheap and reset it once it isn‘t. Probably not as efficient, but extremely simple to implement.

Re: Pretty soon, heat pumps will be able to store and distribute heat as needed

#170

Post by masklinn »

jcattle wrote: post #165
5ersi wrote: post #109

It uses phase change (solid to liquid) to store heat at about 200 kJ/kg. Compare this to heating water in a boiler from 10c to 60c - stores 209 kJ/kg. So we already have an effective way to store heat which can work for decades without servicing and is also cheap to produce (in terms of money and energy consumption).

Does heating water in a boiler work well with a heat pump? How about a release of energy 10 hours later (peak solar at noon, to first shower the next morning)? I actually don't know the answer. I'm just thinking that there must be more to it, if the answer was as simple as "just heat water".

> Does heating water in a boiler work well with a heat pump?

Sure, heat pump hot water tanks are a thing. Air-to-water heat pumps are less efficient than air-to-air as they need to reach higher target temperatures, but it will be more efficient that straight resistive heating by a factor of 2 at low input temperatures, and 3+-ish at high summer temps.

The primary concern would be the quality of the tank’s insulation. I would hope HPHWTs are good on that but if you’re looking into that you probably want to double check the heat loss of the tank.

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