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

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

#151

Post by MengerSponge »

sbierwagen wrote: post #139
Marsymars wrote: post #130

Earlier quoted context omitted.

There are also existing commercially-available residential units (e.g. Ecombi or Steffes) using ceramic bricks that are in the ~450 kJ/kg range.

Note for the confused: Ecombi achieves this by heating the bricks to dramatically higher temperatures using conventional resistive heating elements, thereby storing more energy, even though the specific heat capacity of any ceramic material is dramatically inferior to that of water. But, as a result, Ecombi has a much lower system efficiency than a heat pump, since it's essentially just a space heater pointed at a ro…

I suppose that efficiency whammy is worth it if you can use it to smooth out the duck curve. If power rates go negative then you'd be a fool not to run a space heater pointing at a rock!

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

#152

Post by lstodd »

xattt wrote: post #120
yowayb wrote: post #114

Earlier quoted context omitted.

I went to Moscow in December several years ago and learned they've got one the world's largest district heating systems.

I am not sure if this is still the case, but up to 20 years ago, these were typically shut off in May-June to August for “maintenance” which resulted in a prolonged period of no hot water in apartments.

In Moscow? Never. It's been usually a month in soviet times, two weeks max nowadays, usually sometime in late June - early August.

edit: also on heating question - Moscow's electricity is provided by 40 or so big gas-fired steam turbine generator plants, about 10GWe total. District heating serves as cooling for all this power generation.

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

#153

Post by hippo22 »

gwbas1c wrote: post #84
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…

You're about 20 years behind. My heat pump is working great at 0F. It's 7 years old.

It really depends on how well your home is insulated. Heat pumps don’t work well on old, poorly insulated houses in cold climates. If they can keep up, which is a big if, the price of electricity generally dwarfs natural gas, even if the heat pump is running at 250-300% efficiency.

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

#155

Post by Tor3 »

stuaxo wrote: post #73
Tor3 wrote: post #66

Earlier quoted context omitted.

I had a heat pump installed in 2010. In a cold climate. Only used for heating. It paid for itself extremely quickly - less than three years. It's still going strong, in 2026. It's important to maintain it regularly, i.e. deep cleaning every two years or so. The first time I got a company to do it for me, and the technician taught me how to do it all by myself, so that's what I do. In any case having a professional do…

What did you heat with before?

Electric resistive heating, which is the main power source here (all hydro, until recently). Plus a wood stove in case of power cuts. We used that one quite a bit during cold spells before the heatpump came along. Now not much at all.

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

#156

Post by Tor3 »

manmal wrote: post #105
stuaxo wrote: post #73

Earlier quoted context omitted.

What did you heat with before?

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)

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

#157

Post by ZeroGravitas »

coryrc wrote: post #108
DrScientist wrote: post #34

Earlier quoted context omitted.

Indeed. In the UK there was a unfortunate trend of ripping out these energy storage devices and replacing hot water tanks with on demand electric hot water heating ( only heat the water you need ). And new builds often have no tanks ( as it saves space in the new tiny homes ). Very short sighted in my view - a very simple way to store energy and everyone uses hot water directly.

They don't work well with heat pumps. Heat pumps lose efficiency as the differential increases, so if you try to store heat in a tank, you quickly drop capacity and efficiency. Versus resistance, which is exactly as efficient at 0°C and 1000°C, and why those storage heaters used to make sense. (And storage is directly proportional to temperature differential above interior ambient)

Home hot water heating in the UK with heat pumps is about 250-300% efficient (slightly lower than the efficiency of home heating but still much better than resistive).

No one is storing 1000C water at home.

It is true that the temperature deltas affects efficiency. You can use the thermocline to draw from the cooler lower portion of the storage tank to push this further. Or less technically, just a bigger tank, though this has some tradeoffs.

In warmer countries they are set up differently can act as free air conditioning by extracting heat from indoor air at the same time as heating water.

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

#158

Post by Tor3 »

hippo22 wrote: post #153
gwbas1c wrote: post #84

Earlier quoted context omitted.

You're about 20 years behind. My heat pump is working great at 0F. It's 7 years old.

It really depends on how well your home is insulated. Heat pumps don’t work well on old, poorly insulated houses in cold climates. If they can keep up, which is a big if, the price of electricity generally dwarfs natural gas, even if the heat pump is running at 250-300% efficiency.

It's not really correct to say that heat pumps don't work well on old, poorly insulated houses in cold climates. That it's a heat pump is not the issue, that it's cold is not the issue, the problem is only that with poor or no insulation in a cold climate you'll need a huge heater (say, 10-15kW just for the living room). And domestic heat pumps are not designed for that range. If you could get one that big then it would work very well indeed.

If you have a poorly insulated house then the fix is to insulate it, which is what a lot of people are doing around here, with very hold houses. My house is less than 60 years old and very well insulated for the time, and it holds up even today - it's always warm, with the heat pump not even close to its max power.

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

#159

Post by IshKebab »

Xylakant wrote: post #61
DrScientist wrote: post #34

Earlier quoted context omitted.

Indeed. In the UK there was a unfortunate trend of ripping out these energy storage devices and replacing hot water tanks with on demand electric hot water heating ( only heat the water you need ). And new builds often have no tanks ( as it saves space in the new tiny homes ). Very short sighted in my view - a very simple way to store energy and everyone uses hot water directly.

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).

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

#160

Post by raffraffraff »

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).

I don't know why these aren't used more in building fabric. There's a youtuber who makes these phase change solutions out of various salt mixes aiming for the correct change temperature for a specific application. Eg he made panels for his shed roof (keeps it cooler in sun, warmer at night). Obviously this works better to smooth out large, reliable daily temperature swings, and offers little to someone in a constantly hot or constantly cold place.

I live in Ireland where night/day temperature swings are small. To cool my attic on a hot summer day I'd need to move that heat into a large water tank that gets used for laundry, cleaning, showers etc and is refilled from cold mains water. But fitting an air to water heat exchanger inside my attic would be a big expense and I would have to make sure I didn't freeze the attic.

Regular air to water heat pump could be hooked into my existing tank I suppose?

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