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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

#211

Post by LunaSea »

Tor3 wrote: post #158
hippo22 wrote: post #153

Earlier quoted context omitted.

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 wo…

> If you have a poorly insulated house then the fix is to insulate it

I've been quoted prices to insulate my house that represent 50% of the original acquisition price of the house.

I would need to pay 0€ for both electricity and heating for the next 100 years for this to make sense at current prices.

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

#212

Post by mock-possum »

V__ wrote: post #193
jaapz wrote: post #191

> But storing the heat they produce has not been possible Many heat pumps are installed with a large insulated buffer of water (for ex. 300L), which stores heat pretty well? And homes that use underfloor heating in concrete can store heat pretty well too. Many people use that to heat up the home when energy is cheap and disable the heat pump when it is expensive.

Water (given enough volume) is a pretty good heat storage. https://youtu.be/Bm7L-2J52GU?t=270

It can be a pretty good ‘battery’ too

https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit...

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

#214

Post by BrtByte »

jaapz wrote: post #191

> But storing the heat they produce has not been possible Many heat pumps are installed with a large insulated buffer of water (for ex. 300L), which stores heat pretty well? And homes that use underfloor heating in concrete can store heat pretty well too. Many people use that to heat up the home when energy is cheap and disable the heat pump when it is expensive.

It's not that heat storage didn't exist, it's that this is closer to a "thermal battery" than a thermal flywheel

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

#215

Post by BrtByte »

chankstein38 wrote: post #57

They should've used lasagna. You could be in a tundra heating it over a fire and, as long as you get it sufficiently and consistently hot, it'll still burn your mouth 20minutes later.

It's actually the same physics: layers, trapped moisture, and phase changes holding onto heat way longer than you expect

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

#216

Post by labcomputer »

BrtByte wrote: post #213

An 85% round-trip efficiency and 4X smaller volume sound great, but how does the installed cost compare to just oversizing a hot water tank or running the heat pump harder during off-peak hours?

That’s essentially what they’re doing. The innovation is an engineered material having a specified temperature of phase change.

So the temperature swing is smaller (almost zero) so heat losses due to non-infinite insulation are reduced.

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

#217

Post by hippo22 »

footydude wrote: post #202
hippo22 wrote: post #153

Earlier quoted context omitted.

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.

> 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. I've got a 1930s semi-detached house (UK, north of England) - heated solely by a ASHP for both heating and hot water. Our Seasonal Coefficient of Performance is currently 3.47 (347% efficie…

The issue with poorly insulated houses in cold climates is not about efficiency. The issue is that the thaw cycle makes it impossible to actually come up to temp because too much heat is lost during thawing. Most of the UK isn’t really considered “cold”, which is probably why you don’t have this issue.

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

#218

Post by ProllyInfamous »

stratosmacker wrote: post #204
ProllyInfamous wrote: post #172

Earlier quoted context omitted.

I have two heat pump water tanks, one Rheem and one AO Smith (our local utility heavily-subsidizes these, with a net-cost less than a standard tank water heater ). They both are rated for annual kWH usage less than the US EPA yellow label can display (for their category of tanked water heaters , i.e. competing mostly with resistive heating models). Annually water heating is about 3% of my energy consumption.

Do you prefer one to the other? I’m in the market

The AO Smith (retail $1678) cost $250, after rebates (available to all SFH in any of TVA's power sellers, typically between Thanksgiving and NYE). With rebates the Rheem was $1000 (and is two years older).

Without rebates, they're similarly priced.

As far as reliability, they both have decent warranties and backup heating elements. Both heat water without internet connectivity. Similar performances (as far as heat output).

Overall, I feel the AO Smith is more customer friendly. Definitely easier to install:

1) AO has both top and side water connections; Rhm has one top and then one side connection (why?!)

2) AO's venting connections are far superior to Rheem's (which require custom/expensive adapters if installed in spaces on top... so much easier/cheaper to install into a closet. Rhm's top slit needs a $120 plastic adapter, and then ejects to the side (of a 24"D cylinder) [again: why?].

3) Rheem will not stay in ELECTRIC-HEAT (only) mode, for longer than two days — it automatically reverts to the prior heat pump option (which is annoying; you can use the app and set up a schedule to "force" electric mode... but then you have to use an app). AO stays in whichever mode you select.

4) AO is just nicer presentation. Despite a few obviously less-expensive components and design decisions... the AO is better thought-out. Just as an example, the Rheem has a threaded 3/4" socket for condensate, while the AO has a pre-installed (cheaper, too) drip tube.

5) The AO's electric vault is on the side (and not top) so a top leak is less likely to fill the conductors // corrosion. This is a better decision.

6) Rheem will likely last longer, despite being two years older. We'll see.

Either one will save you a lot of electricity + bonus dehumidification (while operating). I bought whichever was cheapest, the first time; now I would buy the AO even if ~$250 more expensive because the install is that much easier. This last rebate period I bought three =P

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

#219

Post by hippo22 »

Tor3 wrote: post #158
hippo22 wrote: post #153

Earlier quoted context omitted.

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 wo…

The issue with “just” insulating your home is that many homes weren’t designed with insulation in mind and thus it’s not a straightforward proposition.

For instance, masonry was a common building material and that is not easy to insulate. You need to add many inches of insulation on either the outside or the inside, both of which have complications.

Even in a basic stick framed house, you’re still talking about taking down all the exterior walls, likely involving removing plaster and replacing it with drywall. Plaster has a number of nice properties, so it’s sad to remove. And that’s not to mention the price of this work.

Finally, roofs need special consideration. Most roofs today need to be properly vented, which was not as much of a consideration when the houses naturally breathed. Venting today is often done with soffit vents. Yet on historic houses, soffits are typically one of the nicer details. It’s not trivial or cheap to install venting in such cases.

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

#220

Post by ifwinterco »

IshKebab wrote: post #190
ifwinterco wrote: post #161

Earlier quoted context omitted.

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

Right but unless everyone is drawing large amounts of power at the same time it doesn't matter if you use 1kW for 10 hours or 10kW for 1 hour. To the grid they look the same. One interesting case where "at the same time" actually does happen is overnight car charging. Some chargers are configured to start charging exactly when a cheaper tariff kicks in, which causes big transient issues for the grid. I think modern c…

Yep but while that is true at the level of the overall grid, actually the nearest part of "the grid" might be a local transformer that only serves 10-100 houses.

At that scale, it's definitely possible that you all plug in your electric cars and turn on your heat pumps more or less at once on a cold evening after work and start cooking your local transformer. Not my day job but I think it is a potential issue when everything is sized assuming ~2kW average demand or something

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