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.
cromka 12 hours ago [-]
I was recently wondering if any particular type of food contributes to mouth cancer prevalence and I concluded that at the top of that list would be be lasagna and cherry tomato on a pizza/in a soup.
Loughla 11 hours ago [-]
And yet, if you make it like I do, there always manages to be one piece that is ice cold while the rest is shockingly hot. Even if you're start with warm ingredients.
Physics does not apply to lasagna.
Also I suck at making lasagna.
LoganDark 8 hours ago [-]
I don't know how you cook your lasagna, but cooking for longer at a lower temperature usually results in more even heating than cooking for less long at a higher temperature. (This is one of the reasons microwaves are so terrible at heating evenly.) If you're not already, that may help.
(I also imagine using the circulation in a convection oven might help as well. Also, preheating your oven! Even if it's a toaster oven.)
esseph 8 hours ago [-]
Microwave tip:
Use the power button to select a lower power level, and cook the food for longer.
goopypoop 7 hours ago [-]
toroidal lasagne microwaves better
stavros 7 hours ago [-]
Spotted the Brit.
goopypoop 5 hours ago [-]
u wot m8
dataflow 7 hours ago [-]
Only works adequately if your microwave is the rarer kind that actually lowers the power (inverter), instead of just switching between 100% and 0% repeatedly.
afiori 4 hours ago [-]
This should depend on the frequency of the switching, if it is every few seconds it should behave sorta the same
vel0city 6 hours ago [-]
I don't have the fancier inverter style. Setting a power level still works pretty well even though flawed. Drawing out the overall cooking time still manages to get things more evenly heated in the end when you give the food time to distribute the heat throughout the food.
Cooking food for 2 minutes at 50% power gives a noticeable difference in average temperature compared to cooking food for 1 minute at 100% power and waiting a minute.
And I don't always know what it decides to do as far as turning the magnetron on and off on its sensor modes, but it'll spend a while doing automated reheat and potatoes and what not and it'll be dang near perfect every time.
Don't get me wrong I'd love an inverter microwave, truly a better option. But its not like the duty cycle process has no impact.
chongli 6 hours ago [-]
It's funny, because the inverter microwave is actually cheaper to build nowadays. It uses a small switching power supply to generate the needed voltage to run the magnetron at different power levels. The older style duty cycle microwaves use a huge transformer to generate the high voltage, which makes them way heavier and more expensive due to all that copper.
vel0city 4 hours ago [-]
My microwave is over 20 years old and still working fine even with its computerized automatic modes. Modern versions of the product line are inverter based. Whenever this unit fails I'll probably replace it with the modern inverter version. I've used it at friends places, it's quite nice.
It's a GE Profile model FWIW. It seems like a good product line from my experiences. The matching oven has also been a good performer overall.
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).
jcattle 28 minutes ago [-]
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".
masklinn 6 minutes ago [-]
> 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.
moooo99 8 minutes ago [-]
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.
raffraffraff 1 hours ago [-]
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?
Marsymars 7 hours ago [-]
There are also existing commercially-available residential units (e.g. Ecombi or Steffes) using ceramic bricks that are in the ~450 kJ/kg range.
sbierwagen 5 hours ago [-]
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 rock. It only makes sense for jurisdictions with time-of-day variable pricing of electricity, and trades off simplicity and low initial purchase price for lifetime cost.
Marsymars 5 hours ago [-]
Thanks for the notes! I've seen them at other people's homes, but that's about the extent of my knowledge about them. (And I quickly googled a spec sheet to calculate a kJ/kg value.)
MengerSponge 4 hours ago [-]
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!
thescriptkiddie 9 hours ago [-]
one difference is that a phase change stores energy at constant temperature, which may be desirable given that heat pump efficiency is inversely proportional to temperature output temperature
LoganDark 7 hours ago [-]
I feel stagnant water would be more annoying for maintenance than something like salt hydrates.
chickenbig 1 days ago [-]
Perhaps I am missing something; this product already exists as the Sunamp Thermino.
It also exists, as described in the headline, as a tank of heated water.
The phase change stuff has positives like taking up less physical space but it's also a much less mature tech than storing hot water.
Nition 12 hours ago [-]
It's funny how useful water is for power generation.
There's heat storage as discussed here.
Or you can store cold water in a reservoir as a giant battery, pumping it up high when you've got excess power, and letting it back down to generate hydroelectricity from it later.
Or you can boil water to make steam that spins a turbine and use it to convert anything that can heat water (coal, oil, nuclear...) to electricity.
themafia 10 hours ago [-]
> It's funny how useful water is for power generation.
It's gravity that does the generation. Water is convenient because it's weight per unit of volume is very high. Higher than most things we can get our hands on and it's also exceptionally safe.
Since water isn't perfectly clean the main problem you face is corrosion. Which can take a great system and turn it into a nightmare of buried leaks and sudden problems.
As far as our options go it _is_ really convenient.
DrScientist 22 hours ago [-]
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.
coryrc 10 hours ago [-]
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)
ZeroGravitas 2 hours ago [-]
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 delays 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.
Xylakant 12 hours ago [-]
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.
IshKebab 1 hours ago [-]
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).
ifwinterco 1 hours ago [-]
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
a_better_world 12 hours ago [-]
My hot water tank once fell off the wall. On Christmas day. Expensive repair.
Hot water tank was in the basement, which was not insulated. So the mass of hot water contributed very little as a heat reserve for the house.
House was in a northern clime.
manmal 10 hours ago [-]
Those are great for buffering only a few hours though. That would help avoid the expensive electricity price peaks.
vee-kay 18 hours ago [-]
You are right in your analogy.
Earth's oceans and seas act as giant heat sinks.
And that means more trouble as global climate change impacts..
I went to Moscow in December several years ago and learned they've got one the world's largest district heating systems.
xattt 8 hours ago [-]
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.
lstodd 4 hours ago [-]
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.
Neywiny 1 days ago [-]
This is similar to nighthawkinlight's videos on phase change materials. It was very cool to see how his Ziploc bags of homemade goo helped regulate temperature.
schiffern 1 days ago [-]
In this work the authors use a ceramic-coated extruded aluminum heat spreader to improve thermal conductivity through the bulk PCM, but I wonder if the graphite flake+powder additive demonstrated recently by Tech Ingredients[1] would be a viable alternative? It might need a stabilizer (thickener) to prevent the ingredients from separating.
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 climates they make your house work that much harder to keep the space warm.
The most optimistic hope is that the government mandate will force enough demand that manufacturers can enjoy some economies of scale and actually try to compete on price. I don't think this will happen anytime soon.
lizknope 11 hours ago [-]
Ask This Old House had an episode literally yesterday where they installed a \
solar-assisted split heat pump water heater. There is a component that goes on the outside of the house but not on the roof which simplifies installation.
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.
globular-toast 15 minutes ago [-]
> 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.
luckystarr 11 hours ago [-]
While they are not as efficient or flexible, they are many times more efficient than resistive electric water heaters. I've installed one with in house air intake (due to construction reasons) in my house and it cooled down the basement by a few degrees (and removed air moisture as an added bonus). In summer the thermal capacity of the ground heats up the basement again, in winter it's a bit cooler, but it still works efficiently.
spockz 12 hours ago [-]
Which models are you looking at? I was still quoted separate pumps for floor heating and a boiler with the pump built in taking the energy from the air two years ago.
> The South Korean giant [Samsung] said its new EHS All-in-One provides air heating and cooling, floor heating, and hot water from a single outdoor unit. It can supply hot water up to 65 C in below-zero weather.
> Dubbed EHS All-in-One, the system provides air heating and cooling, floor heating, and hot water from a single outdoor unit. It is initially released for the European market, with a Korean rollout expected within a year. “It delivers stable performance across diverse weather conditions. It can supply hot water up to 65 C even in below-zero weather and is designed to operate heating even in severe cold down to -25 C,” the company said in a statement. “The system also uses the R32 refrigerant, which has a substantially lower impact on global warming compared with the older R410A refrigerant.”
thunfischbrot 12 hours ago [-]
Afaik heat-pumps in the EU can provide unlimited hot water–what am I missing?
Y-bar 12 hours ago [-]
Geothermal (and airbased) pumps theoretically do not have unlimited heating capacity. For example my pump (Daikin Altherma Geo 3) has a 180 litre water tank so it can ”only” supply 180 litres hot water at 65 degrees Celsius and takes about a minute to heat two additional lites.
So if I want to quickly scald myself in a 400 litre pool at fifty degrees I can’t. But if I had a gas heater that would be possible!
malfist 7 hours ago [-]
Depends on how you measure unlimited. My hot water heater can pretty much indefinitely supply hot water for a single shower head with a modern water saving design. It can heat faster than 1.2 gallons/minute
Tor3 12 hours ago [-]
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 doing it wasn't expensive either. And I clean the dust filters (very easy) every second week or so.
snuxoll 11 hours ago [-]
Installed mini-splits to replace the propane stove that heated my house, DIY job, so all it cost was the units themselves and some materials.
Propane bill (no natural gas, town of 500) from Oct 24 to Feb 25 (installed the mini splits that month) was $1200, for just heating.
My mini-splits are on a dedicated sub panel with an Emporia Vue 3 energy monitor. $604 in electricity consumption, and that includes air conditioning over the summer months.
For what it’s worth, our winter weather averages 25-35F with the occasional few days dipping to tens, single digits, and the occasional -10 freak; but these units just BARELY have a HSPF4 rating to classify as “cold climate” models. Still going to pay for themselves in 6 years without any tax credits, and 4 or so since I still installed them when they were available.
stuaxo 12 hours ago [-]
What did you heat with before?
Tor3 2 hours ago [-]
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.
manmal 10 hours ago [-]
Certainly not gas or oil, which are still cheaper to heat with than heat pumps.
Tor3 2 hours ago [-]
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)
darkteflon 50 minutes ago [-]
I’m in Japan too. Could you name the model you ended up going with? My heating bill in the winter is insane.
Tor3 27 minutes ago [-]
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).
tempestn 7 hours ago [-]
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.
zobzu 5 hours ago [-]
in CA my natural gas is far cheaper than the heat pump sadly
yurishimo 21 minutes ago [-]
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!
gwbas1c 11 hours ago [-]
You're about 20 years behind.
My heat pump is working great at 0F. It's 7 years old.
hippo22 3 hours ago [-]
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.
Tor3 1 hours ago [-]
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.
baggachipz 11 hours ago [-]
heat pump for house !== heat pump for hot water
Youden 11 hours ago [-]
I don't know what it's like where you're living but here in Switzerland it's completely normal to have one heat pump that does both. Here there's a lot of floor heating, which also uses water, so you usually just run one loop to the "boiler" (a water tank with a copper loop for the water from the heat pump to circulate through) and one through the floor and have a valve to switch which is running through the heat pump.
I got it in October so most of the time I've had it has been <10C. It's produced 806.3 kWh of heating for hot water and 6587.2 kWh for the floor heating. It consumed 302.7 kWh and 1801.4 kWh respectively, for a COP of 2.66 and 3.66.
gwbas1c 10 hours ago [-]
There's a lot of different heating systems: If your heating system uses hot water at any point, (baseboards, hydro-air, underfloor, ect,) using a single heat pump makes a LOT of sense.
Personally, I prefer an air-source heat pump hot water tank. It significantly dehumidifies my basement.
serpix 4 hours ago [-]
Yes, same thing. Heat pump to heat exchanger. This is over 39 years old tech and in common use around Scandinavia and mainland europe. This is ancient technology.
karussell 11 hours ago [-]
Why not?
jcgrillo 4 hours ago [-]
Mine are in climate zone 6. They're only a couple years old. The coldest temperatures I've run them at so far are -21°F and they kept the house adequately unfrozen. They'll maintain a COP of 2 down to 5°F IIRC. The hot water heater is an 80gal Rheem heat pump unit. No complaints there either. It would be pretty great to have some thermal storage though, temperatures in the dead of winter here are usually above 5°F during the day but drop well below zero at night. Blasting the heat pumps during the day to bank heat for overnight would be far more efficient.
newhotelowner 8 hours ago [-]
They marketing like it's an expensive tech, but it's pretty cheap.
We have been buying heat pump PTAC for the hotels for last 20 years, and price difference is usually 5% between with and without heat pump.
Seems like all companies are colluding with each other for marking up prices.
tempestn 7 hours ago [-]
We somewhat accidentally ended up with a good combo: we have a ventless heat pump dryer, and a heat pump water heater, also in the laundry room. So when doing laundry, the water heater cools the room while the dryer heats it, so they roughly cancel out.
As an aside, HP dryers are really elegant tech, and it's a shame they're not more common. They use the heat pump not just to heat the air in the dryer, but also to condense the moisture back out of it, so just the water can be drained away instead of needing to exhaust the air outside. So you need much less energy overall, and you don't need a dryer vent. The only downside is they're a bit slower, but ours has a resistive backup option for when you need clothes dry asap, so really it's just price.
zhivota 7 hours ago [-]
Heat pump dryers work at a much lower heat as well since much of the heating of a traditional dryer is lost out of the vent. The heat pump condenses the water out of the hot air so you don't lose the heat.
I've stopped needing to sort my clothes out as a result, I used to hate putting synthetics in a regular dryer because they get worn out so fast that way.
jonstewart 7 hours ago [-]
I bought a Samsung HP dryer a few years ago and it'd be great except for a terrible design flaw where lint gets trapped in its heat sink fins, turning into a soggy mess.
tempestn 5 hours ago [-]
We have a Whirlpool that I love, but they discontinued it a couple years ago with no replacement, and I can't imagine why. I guess most people just shop on price, so it didn't sell. Like I said, a shame.
stuaxo 12 hours ago [-]
They use them a lot in Norway, it's hardly warm there.
ortusdux 11 hours ago [-]
I'm in the northern US and am very happy with mine. I self-installed with a county rebate, so the total cost was a Saturday and $700. My old electric unit was EPA rated for $450/year, and the new one has averaged $170/year over 4 years, so I've already broken even.
themafia 11 hours ago [-]
> government mandate will force enough demand that manufacturers can enjoy some economies of scale
So you want the government to pick winners and you want to do business with a monopoly? This is the opposite of what you would want.
If the product saves me money, and it's _actually_ better, I will buy it in a heartbeat. If you're involving the government it's because one of those things isn't true.
enaaem 4 hours ago [-]
Gas infrastructure is expensive to build and maintain. Often times with tax money. What tend to happen in Europe is that they phase out gas by not building gas lines for new development.
Epa095 11 hours ago [-]
Not many numbers in there. I would be interested in some measure of energy and effect per volume, e.g how many kWh of heat are we talking about at e.g 1 liter, and how fast (kW) can it produce it?
gwbas1c 11 hours ago [-]
The article omits some critical details:
It says this is both a "heat pump" and also "storage" AND says that it will run when electricity is cheap or plentiful. Thus:
1: Where does it pump the heat from? (Or is this not really a "heat pump" and instead is using resistive heating?)
2: How long does it store heat? Is this something that will store heat on a 24-48 hour basis, or will this store heat during the spring / fall when longer days mean extra power from residential solar, and then use the heat in the winter?
3: Is the unit itself "warm" when storing heat? Or is the heat stored in a purely chemical way and needs to run through a catalyst or similar to get it back?
4: Can this be scaled up for general domestic heating?
---
Just an FYI: There are plenty of schemes with resistive electric water tanks to store heat when power is cheap.
mike-the-mikado 10 hours ago [-]
I would guess that is intended for a daily cycle, perhaps using air source heat pumps at times of day when the air temperatures are higher and electricity prices are lower, then using it as required.
As it works on phase change (e.g. think of melting ice) heat is added (or removed) without changing the temperature of the store (which, I guess, might be hotter or colder than where the heat is extracted or used).
gwbas1c 6 hours ago [-]
But how hot does the heat source have to be?
Depending on the needs, resistive heating can get hundreds of degrees hot, but the best heat pumps that I know of can only raise the temperature about 60 or 70° f.
IshKebab 10 hours ago [-]
1. The device is just storage. It would be paired with an air or ground source heat pump.
2. With good insulation you can easily store heat for a day which is all you need. You're never going to get close to storing summer heat for the winter. That's not impossible but not feasible for something this scale (and not cost effective at any scale).
3. You just heat it up and cool it down. There are no fancy chemical processes happening other than the phase change. It's exactly like a phase change hot/cold pack you can buy on Amazon.
4. I'm pretty sure this is designed for domestic heating...
It's kind of an obvious idea tbh. I don't think they've done anything super innovative... They made an aluminium heat sink..
npodbielski 4 hours ago [-]
> With good insulation you can easily store heat for a day which is all you need. You're never going to get close to storing summer heat for the winter. That's not impossible but not feasible for something this scale (and not cost effective at any scale).
This is ground basically. How deep varies but few meters underground you basically have average yearly temperature. You could pump heat from house to the ground to take it out from the ground during winter.
butvacuum 10 hours ago [-]
the only new thing- no matter how they do it- is putting it on residential instead of commercial or industrial installs.
my childhood public school took us to some big commercial building- I think it was Sears' HQ- and they proudly showed us the huge blocks of ice providing chill during the day.
tootie 6 hours ago [-]
Presumably it's air source and if it's indoors it will just be the air in whatever room it's in. That's how my ventless dryer works. I'm not sure what the implications are for taking heat from air that may have been heated by another heat pump are for efficiency. But also if it's summertime, they may be relieving load from your air conditioner.
jokoon 2 hours ago [-]
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
Starting to get more optimistic about our energy future. Things seem to be tracking pretty good
hedora 1 days ago [-]
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.)
ifwinterco 1 hours ago [-]
It sounds like you need more thermal mass, a traditional brick/stone house wouldn't have that problem
karussell 11 hours ago [-]
I think this can work and instead of that the heatpump pumps the heat into your house (when "solar is plenty") it would pump it into the storage. (I have a similar setup, but heat the water but of course this is rather limited)
unrelated: a simple technical solution to your window problem would be home assistant and a few sensors to notify you when the windows are open too long or open when too cold inside.
hedora 9 hours ago [-]
It’s more about predictive modeling: At what time + temperature do you close windows, given predicted cloud cover and overnight temperatures/wind?
Come to think of it, if we had a big salt slurry that transitioned at 72F in the floors, that would probably do the right thing. It’d create a step function making it hard to heat above 72, or cool below it.
I wonder how much density changes as these things transition. Would a static pool (mixed by freezing) work, or would it need a pump?
direwolf20 22 hours ago [-]
Heat pump heat is just heat.
hnburnsy 1 days ago [-]
Related, TIL the US is effectively banning residential electric resistance water heaters in 2029, with heat pump water heaters being the only type that can meet the new standards. Users will see a 2-3x in cost difference and a 3 to 8 year payback on savings.
amazingman 1 days ago [-]
This is exactly the kind of thing government is for, even though it's missing the other half: subsidies. At the very least buying heat pumps for the next 5 years should be tax deductible. Even better: a $2000 or similar rebate.
lm28469 21 hours ago [-]
> even though it's missing the other half: subsidies
It's a double edged sword. In my country everyone bought pellet stoves because of the subsidies, hundreds of companies popped up, now that the subsidies have been phased out, 90% of the companies went down, with their support and warranties of course. The 10% that managed to survive increased their prices, which is easy to do once 90% of your competitors went bust
People who thought they'd save money by having the government (their taxes really) pay the bill are waking up 5 years later with expensive maintenance, the first units are starting to fail and need to be replaced but they can't afford it without the 50%+ subsidies. Not to mention that the prices pellets goes up and down faster than your average shitcoin.
rayiner 20 hours ago [-]
The subsidies and rebates are a scam. The installers just jack up the prices until they capture the entire value of the rebate.
amazingman 16 hours ago [-]
This assumes the consumer doesn't know and can't look up the price of the hardware.
rayiner 16 hours ago [-]
The cost of installation vastly exceeds the cost of the hardware. And the installers will only warranty hardware you buy from them.
DangitBobby 1 days ago [-]
That's probably exactly what will happen.
Energy property - Heat pumps and biomass stoves and boilers
Heat pumps that meet or exceed the CEE highest efficiency tier, not including any advanced tier, in effect at the beginning of the year when the property is installed, and biomass stoves and boilers with a thermal efficiency rating of at least 75% qualify for a credit up to $2,000 per year. Costs may include labor for installation.
Qualified property includes new:
Electric or natural gas heat pumps
Electric or natural gas heat pump water heaters
Biomass stoves and boilers
These are credits that only work if you have owe federal taxes and they cannot be carried forward. I've seen estimates that 40-45% of taxpayers owe 0 or close to 0.
DangitBobby 19 hours ago [-]
You can also get considerable rebates if your state participates in the "Inflation Reduction Act Home Energy Rebate Program", especially if you are low income. My state is still working on rolling it out but hopefully many people who can't use tax credits will be able to take advantage.
Eh? If you have income you owe taxes, Uncle Sam just takes it before you even see it
JoblessWonder 11 hours ago [-]
I think something like 25% of the population reports 0 household income.
(I don't understand the implications, it was just surprising when I heard that.)
direwolf20 22 hours ago [-]
Federal taxes specifically.
seiferteric 11 hours ago [-]
The problem is, energy use is only one part of the equation. Often times new appliances that are more efficient end up being more prone to breaking due to more complexity and companies trying to cut costs to meet a price point. This leads to people needing to replace there appliances much more often which really makes me question how much energy is actually saved if you include the energy used to produce them...
reorder9695 24 hours ago [-]
I don't know about all heat pump systems, but mine at least requires the water tank to have a resistive immersion too. If the tank temperature gets below some threshold the heat pump refuses to work and turns the immersion on instead until it's warmed up enough.
Sabinus 1 days ago [-]
That's a Biden-Harris administration action. What are the chances that Trump deletes it as a 'Democrat/WEF climate hoax con job' as soon as he's made aware of it?
pkulak 1 days ago [-]
If you're making plans 3 years out in the US, you're a fool.
AlexandrB 11 hours ago [-]
The problem with heat pumps replacing electric heaters (in cold climates) is that the waste cold air gets dumped into the house and needs to be heated again. Generally, electric water heaters are expensive to run compared to gas ones, so people use them in places a gas heater is not possible to install (e.g. no way to vent the exhaust). This also means that the heat pump would have nowhere to vent cold air.
This kind of thing is why I don't like bans like this. The specifics matter a lot.
grigri907 5 hours ago [-]
Your heat pump ought to be venting the cold air outside in the first place. If you're pulling the heat for your water out of your conditioned air, yeah you're in a losing battle.
cucumber3732842 1 days ago [-]
Is that 2-3x before or after the plumber marks it up?
What an exceptionally moronic thing to ban, the market solves this naturally. Resistance heaters are 100% efficient whatever fraction of the year is heating days. So if that's 1/2 the year and the water heater can't last 16yr because of water quality the heat pump heater will never pay you back.
This reminds me a lot of the time some jerks in west coast desert states convinced the feds to regulate plumbing fixtures so that eastern "we take from the river and put back in the river" municipalities that have more water than they know what to do with have to suffer through low flow everything.
beAbU 19 hours ago [-]
Heat pumps are effectively more than 100% efficient fyi. You put 1000W of electricity in, you get 2500W of heat going into the water. (Numbers are only illustrative)
Running cost of heat pumps for heating is much much lower than resistive heating.
hnburnsy 1 days ago [-]
Heat pump water heater (hybrid/HPWH, e.g., 50–65 gallon equivalent): Unit prices range from ~$1,500–$3,000+ (most common models $2,000–$2,500), with total installed costs $2,500–$5,000 (higher if electrical upgrades or space mods needed). Average retrofit/install often lands around $3,000–$4,000.
lm28469 22 hours ago [-]
And for small households they virtually never pay for themselves before they die or need expensive maintenance... It only makes sense if you use a lot of water or if your electricity is very expensive. In my case it's even worse, with solar panels and self sufficiency they literally cannot break even
sgc 1 days ago [-]
Electrical upgrades are almost always required, and price is more like 7k-9k around here. It's going to be seriously painful for a lot of people.
dashundchen 1 days ago [-]
If you were in the market for an resistive electric heat pump, you likely had the service for it already. A heat pump version will almost always require less power.
sgc 15 hours ago [-]
My bad, read too quickly. I was thinking of the forced change over from gas water heaters, which is already happening in the California Bay Area and will only expand.
quickthrowman 20 hours ago [-]
If you currently have an electric resistive water heater, a heat pump water heater with the same heating capacity will use 3-4x less power, which means you can use a much smaller circuit.
A 6kW 240V EWH uses 25A, it’ll need #8 wire and a 35A or 40A breaker.
An equivalent HPHW would use 1.5kW at 240V, or 6.25A. You can use #14s and a 15A breaker.
drhike 11 hours ago [-]
Ehh 120v models exist. My 65 gal runs fine on a standard 20a breaker.
direwolf20 22 hours ago [-]
Is the heat pump heater taking heat from inside or outside the house?
lm28469 22 hours ago [-]
Depends on the model, but a lot use the air from their own room, that's why they can't be installed in small rooms. Models pulling the heat from outside are more expensive and require more labor obviously, and they don't make a lot of sense for places that are bellow 0c multiple month a year as the COP will drop to 1.x and you will most likely need extra electricity for the anti frost cycles
AlexandrB 11 hours ago [-]
But dumping the waste cold air into the house when it's below 0C outside doesn't make much sense either.
wffurr 10 hours ago [-]
You already dump waste hot air into your kitchen from the refrigerator during the summer. Is this much different?
It does seem a little silly to have these chains of heat pumps all working in various directions. I read about "cold district heat" in a sibling comment which circulated lukewarm water to use as a heat sink or source with heat pumps. Maybe something similar could be done with a water or refrigerant loop through the house. Probably not economical to do all the plumbing though.
lm28469 8 hours ago [-]
> you already dump waste hot air into your kitchen from the refrigerator during the summer. Is this much different?
Heating water is very energy intensive, fridges are a rounding error compared to water heaters
bethekidyouwant 9 hours ago [-]
A hot water heater takes much more power than a fridge
aaaalone 23 hours ago [-]
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rekabis 1 days ago [-]
I would love to see a bus-sized version for year-long temperature moderation. Like, drop house heat into it during the summer so it can re-heat the house over the winter, and pull all the heat out of it by Spring so that it can cool the house over the summer.
Bus sized because that amount of thermal mass is bound to take up a lot of space, but capable of being buried so that it doesn’t actually take up property space.
fy20 1 days ago [-]
I ran the numbers for this a while ago. I live where we have proper winters (currently -22c). I wanted something simple just with solar thermal and water pumps (no heat pump). Sand batteries work at an industrial level, but for domestic use you want something simple so that means just water.
A 100m3 (100,000 litres or 26,500 gallons) cylindrical water tank (approx 5x5m) buried and insulated with 50cm of XPS could provide around 4000kWh of deliverable heat throughout winter. Which would be more than enough for heating and domestic hot water for my house.
In the summer you'd use solar thermal to charge it to 85c. In the winter you'd run water through underfloor heating and discharge it to 35c (so you just need a mixer valve and pump).
The structural engineering part of it isn't actually that complicated (with a garden on top, not a house). You can buy plastic water tanks of that size, it just needs to be buried and have XPS foam placed around it.
Because it's volume, it scales up well. An extra one meter in each direction would increase the volume by around 60%, but you have a lower overall heat loss, so the heat capacity would more than double.
The important part of it is the XPS foam though, without this the loses are too great and you don't retain any heat. This is why insulating your foundation and slab is so effective.
bilbo-b-baggins 1 days ago [-]
So… store heat in an insulated swimming pool 10ft deep, 30ft wide, and 90ft long, at 185F, above the service temp for XPS foam, got it, ok. At least you could also use it to sous vide an entire cow.
eande 1 days ago [-]
Interesting practical approach to actual build it. Did you do a cost analyses or RoI?
rekabis 16 hours ago [-]
Pedantic Pete here:
• The centigrade is capitalized when used after a number. There is also a singular glyph for the entire degree-centigrade convention: ℃.
• There are also superscript numerical characters to use with volumes, without having to use formatting: m³.
UTF-8 is fun! As is automatic text replacement, once you have the appropriate triggers set up.
Xylakant 12 hours ago [-]
This exists, in german it's called Eisspeicherheizung. You have a few cubic meters of water buried in a concrete bunker and you use a heat pump to pull energy out of the water until it freezes. The system not only uses the thermal mass of the water, but the thawing/freezing energy which is higher than the energy required to heat water by 1degree by a factor of 80 - meaning if you freeze 1kg of water, you need to pull out enough energy to heat one kg of water by 80 degrees.
You can then use a heat pump that's optimized for the expected temperature range and you don't even need to insulate your water storage tank - you actually want the cold in winter to seep out into the surrounding soil, free energy.
In summer you have cold storage for your AC.
BenoitEssiambre 5 hours ago [-]
Yeah I always wondered if I ever switched to solar panels, would there be a way to accumulate heat to be used in the Canadian cold months that have little sunlight? The closest I found was electric thermal storage based on heating bricks. They can accumulate more energy than water since they can go to higher temperatures. For example these say they go to 1300°F or 700°C https://steffes.com/ets/roomheater/ . They don't seem to have large models that could heat a house for months however.
syntaxing 1 days ago [-]
So…geothermal? I wish this was possible too but I don’t see how it will work scientifically. Water is one of the chemicals that have one of the highest thermal mass/specific heat (maybe 1/3 of salt hydrates). Even then, you have to bury a crapton of water underground. This design mentioned in the article is more for short term, like 12 hours storage (since they’re accommodating for solar in nighttime)
Neywiny 1 days ago [-]
Is geothermal not the opposite of that? My understanding was that the geothermal MO is that there's virtually infinite thermal mass in the earth so it won't heat/cool, not that you heat/cool your local chunk
syntaxing 1 days ago [-]
To a certain extent, yes. The reason why the water is there is because the thermal flux of the ground is low, so the large mass of water provides a strong buffer. But you can’t cheap physics. You would need a crap ton of salt hydrate to accommodate a whole season of heat needs, even if you don’t factor in thermal loss from the container.
rekabis 16 hours ago [-]
Geothermal needs either a horrifically expensive vertical bore hole going down a few hundred metres, or a good acre of land for laid-down piping. I have neither the money nor the horizontal space. So I am thinking something compact that needs to go only about 6-10m vertically into the ground (so I can hide it fully underground with about a metre of soil on top), and take up the horizontal space of 4 parked cars. I have more than enough room and cash to have that cube of space dug out.
And being on an alluvial plain, if I filter out all the rocks larger than a pea, a good 90+% of what is dug out can immediately be trucked away.
aidenn0 11 hours ago [-]
I live in a climate where, for most of the year, the daily high-low temperature range includes 20C, so I'd like a whatever sized one is needed to average that out, and run most of the year without any active heating or cooling.
stubish 1 days ago [-]
You seem to be describing ground sourced heat pumps. If you wanted, you could insulate a a chunk of foundation or earth to avoid heat loss. But just the ground under your building seems to work well enough.
rekabis 16 hours ago [-]
Ground sourced heat pumps need either a horrifically expensive vertical bore hole going down a few hundred metres, or a good acre of land for laid-down piping. I have neither the money nor the horizontal space. So I am thinking something compact that needs to go only about 6-10m vertically into the ground (so I can hide it fully underground with about a metre of soil on top), and take up the horizontal space of 4 parked cars. I have more than enough room and cash to have that cube of space dug out.
And being on an alluvial plain, if I filter out all the rocks larger than a pea, a good 90+% of what is dug out can immediately be trucked away.
syntaxing 1 days ago [-]
With the adoption of sodium batteries, I wouldn’t be surprised if solar panel + sodium battery would outperform this system by a lot.
belviewreview 1 days ago [-]
A heat pump gets more heat from a given amount of electricity than if the electricity is use for resistive heating. So the ideal design is solar cell + sodium battery + heat pump.
gpm 8 hours ago [-]
Also when the temperature differential is lower, so ideal might be solar -> battery (to time shift to warmest outdoor temperature) -> heat pump -> thermal battery (to time shift to when you need heat).
Does seem like a lot of added complexity (and likely machinery cost) though.
Youden 10 hours ago [-]
Even LFP batteries can work out better.
I live in Switzerland where these are available. A Cowa 58 [0] costs CHF 4692 [1] and stores up to 13.5kWh. If you're heating the water with a heat pump, that's ~6kWh of electricity, so ~CHF 782/kWh.
I'm in the process of installing a 33kWh battery and the battery + inverter cost CHF 13600 in total for just the hardware, so ~CHF 482/kWh.
If you add solar panels, the inverter does double-duty producing AC from both the battery and the panels. The battery does double-duty producing both hot water and allowing you to use solar energy outside the times when the sun is shining.
That said, having ordered a heat pump recently and being in the process of having solar + batteries installed, the amount of electrical work needed for the solar/battery install is substantially higher than was needed for the heat pump and here, the labour costs quite a lot, pushing the upfront cost difference even higher.
I think that's where these heat storage things fit in: they have a much lower upfront cost. No matter how cheap the battery, for it to be useful in a Swiss residence, it needs to output a substantial amount of 3-phase power (3-phase is standard here, even in most apartments), which means you need to spend a couple thousand Francs on an inverter and electrical work. These heat storage devices are quite cheap and don't even need someone qualified to handle refrigerants, I imagine they could be installed by a normal plumber.
That reduced upfront cost makes them far more accessible than electrical batteries, at least for now.
Climates that need a hot tank of water to buffer for heat pumps, will not have meaningful solar panel output during winter. Or do you mean, just load the battery when electricity is cheap? A tank of water is 1k max, probably 10% of a sodium battery.
coffeebeqn 23 hours ago [-]
There’s also solar thermal panels that heat up a liquid circulating in the system and cut out the need for a battery - and can just store the heated liquid.
mrguyorama 12 hours ago [-]
Efficiencies and effects are at the point where taking a photon, converting it into an electron, and using that electron to pump heat is more efficient than turning that photon perfectly into kinetic energy.
Similarly, in mild weather, it is more efficient to burn hydrocarbons and turn it into electricity to run a heat pump than use that hydrocarbon for it's heat energy directly.
Pumping heat is more efficient than making it.
Xylakant 12 hours ago [-]
Thermal solar panels have the advantage of being very simple and surprisingly effective. But if you're lacking space to put up both solar cells and thermal, you can use combined panels which have a solar cell with a backing thermal system. The interesting thing is that these combined panels outperform solar cells even when it comes to electricity generated because solar panels loose efficiency as they heat up, so cooling them actually improves efficieny. Combined panels are much more expensive, though.
karussell 10 hours ago [-]
The problem with thermal solar panels is that you can use its heated water only if it gets warmer than the water in your system, which is not always the case, especially in winter.
Compared to nearly 100% usable energy from normal solar panels.
Furthermore if you have a heatpump you can convert this electric energy into heat energy with a factor of >3 (COP).
Marsymars 6 hours ago [-]
Yeah but if you're in a northern climate your solar panels are only generating like 10% of their summer capacity in the winter anyway due to sun hours/angles... winter is just tough for capturing solar energy in general.
animal531 21 hours ago [-]
Where I live we need a way to store and distribute cold as needed.
Joel_Mckay 8 hours ago [-]
They are a very efficient way to get both AC and Heating:
Unless you live in a cold climate, they are worth it for a discounted energy bill =3
burnt-resistor 20 hours ago [-]
Stanford's cogen plant has an underground "ice cube" for campus/municipal chilled water infrastructure. Perhaps scaling something like that makes sense or perhaps to use an absorption heat pump (AHP) that can operate like and the reverse of an Einstein–Szilard refrigerator?
chickenimprint 1 days ago [-]
So it's a large version of those rechargeable hand-warmers?
ZeroGravitas 1 days ago [-]
Yes, it's the same tech. There's been products on the market for a while even though this press release tries to spin it like it's new and linked to heat pumps.
mrexroad 12 hours ago [-]
IIRC BMW used to have a form of this in their cars about 25-30 years back so that the hvac would be able to blow heat before the engine coolant was up to temp after sitting overnight.
burnt-resistor 20 hours ago [-]
Private equity / Wall St. megacorps want to sell you complex systems that are fragile, unaffordable by the 99%, have short warranty periods, wear out quickly, require cloud logins and proprietary maintenance parts, and are mandated by law.
GFL buying a simple resistive-heated clothes dryer, furnace, or tanked/tankless water heater in 2030.
metalman 22 hours ago [-]
the idea is theoreticaly good, but as it depends on sealing incompatable materials apart, there will be problems, and issues with disposing of failed units.Dry sand works as thermal storage without any issues, and only needs more space, competition will be stiff.Water also works, and ordinary off the floor systems can be used with no modifications.
The only advantage the system will have is in places where space constraints combine with the desire for fancy solutions and ecobabble.
RiceNBananas 1 days ago [-]
[flagged]
danielovichdk 12 hours ago [-]
Stones has the ability to store heat and keep cool.
What's all this fuzz about ?
Etheryte 12 hours ago [-]
It's all about efficiency. You can store heat in anything, but the question is for how long and how much energy can you get back out later. The first part is easy and how we got ovens and stoves, the second part can be pretty tricky depending on your requirements. Large scale energy storage sometimes uses massive amounts of sand for example, but they heat it to hundreds of degrees which is not really feasible in most settings.
Rendered at 09:05:07 GMT+0000 (Coordinated Universal Time) with Vercel.
Physics does not apply to lasagna.
Also I suck at making lasagna.
(I also imagine using the circulation in a convection oven might help as well. Also, preheating your oven! Even if it's a toaster oven.)
Use the power button to select a lower power level, and cook the food for longer.
Cooking food for 2 minutes at 50% power gives a noticeable difference in average temperature compared to cooking food for 1 minute at 100% power and waiting a minute.
And I don't always know what it decides to do as far as turning the magnetron on and off on its sensor modes, but it'll spend a while doing automated reheat and potatoes and what not and it'll be dang near perfect every time.
Don't get me wrong I'd love an inverter microwave, truly a better option. But its not like the duty cycle process has no impact.
It's a GE Profile model FWIW. It seems like a good product line from my experiences. The matching oven has also been a good performer overall.
https://www.youtube.com/watch?v=aEAHLFvD3v4
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 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".
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.
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.
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?
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 rock. It only makes sense for jurisdictions with time-of-day variable pricing of electricity, and trades off simplicity and low initial purchase price for lifetime cost.
https://sunamp.com/en-gb/hot-water-solutions-thermino-range/
The phase change stuff has positives like taking up less physical space but it's also a much less mature tech than storing hot water.
There's heat storage as discussed here.
Or you can store cold water in a reservoir as a giant battery, pumping it up high when you've got excess power, and letting it back down to generate hydroelectricity from it later.
Or you can boil water to make steam that spins a turbine and use it to convert anything that can heat water (coal, oil, nuclear...) to electricity.
It's gravity that does the generation. Water is convenient because it's weight per unit of volume is very high. Higher than most things we can get our hands on and it's also exceptionally safe.
Since water isn't perfectly clean the main problem you face is corrosion. Which can take a great system and turn it into a nightmare of buried leaks and sudden problems.
As far as our options go it _is_ really convenient.
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.
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)
No one is storing 1000C water at home.
It is true that the temperature delays 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.
Hot water tank was in the basement, which was not insulated. So the mass of hot water contributed very little as a heat reserve for the house.
House was in a northern clime.
Earth's oceans and seas act as giant heat sinks.
And that means more trouble as global climate change impacts..
https://www.earth.com/news/ocean-warming-broke-records-for-4...
https://en.wikipedia.org/wiki/Cold_district_heating
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.
[1] https://www.youtube.com/watch?v=s-41UF02vrU
The most optimistic hope is that the government mandate will force enough demand that manufacturers can enjoy some economies of scale and actually try to compete on price. I don't think this will happen anytime soon.
https://www.youtube.com/watch?v=uqyAWkXXt3A
https://www.neshw.com/residential/solar-heat-pump-water-heat...
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.
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.
Is it something from nefit by any chance?
https://www.pv-magazine.com/2026/01/29/samsung-releases-new-...
> The South Korean giant [Samsung] said its new EHS All-in-One provides air heating and cooling, floor heating, and hot water from a single outdoor unit. It can supply hot water up to 65 C in below-zero weather.
> Dubbed EHS All-in-One, the system provides air heating and cooling, floor heating, and hot water from a single outdoor unit. It is initially released for the European market, with a Korean rollout expected within a year. “It delivers stable performance across diverse weather conditions. It can supply hot water up to 65 C even in below-zero weather and is designed to operate heating even in severe cold down to -25 C,” the company said in a statement. “The system also uses the R32 refrigerant, which has a substantially lower impact on global warming compared with the older R410A refrigerant.”
So if I want to quickly scald myself in a 400 litre pool at fifty degrees I can’t. But if I had a gas heater that would be possible!
Propane bill (no natural gas, town of 500) from Oct 24 to Feb 25 (installed the mini splits that month) was $1200, for just heating.
My mini-splits are on a dedicated sub panel with an Emporia Vue 3 energy monitor. $604 in electricity consumption, and that includes air conditioning over the summer months.
For what it’s worth, our winter weather averages 25-35F with the occasional few days dipping to tens, single digits, and the occasional -10 freak; but these units just BARELY have a HSPF4 rating to classify as “cold climate” models. Still going to pay for themselves in 6 years without any tax credits, and 4 or so since I still installed them when they were available.
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!
My heat pump is working great at 0F. It's 7 years old.
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.
I have one of these: https://cta.ch/en/private/products/ah-i-eco-innen
I got it in October so most of the time I've had it has been <10C. It's produced 806.3 kWh of heating for hot water and 6587.2 kWh for the floor heating. It consumed 302.7 kWh and 1801.4 kWh respectively, for a COP of 2.66 and 3.66.
Personally, I prefer an air-source heat pump hot water tank. It significantly dehumidifies my basement.
We have been buying heat pump PTAC for the hotels for last 20 years, and price difference is usually 5% between with and without heat pump.
Seems like all companies are colluding with each other for marking up prices.
As an aside, HP dryers are really elegant tech, and it's a shame they're not more common. They use the heat pump not just to heat the air in the dryer, but also to condense the moisture back out of it, so just the water can be drained away instead of needing to exhaust the air outside. So you need much less energy overall, and you don't need a dryer vent. The only downside is they're a bit slower, but ours has a resistive backup option for when you need clothes dry asap, so really it's just price.
I've stopped needing to sort my clothes out as a result, I used to hate putting synthetics in a regular dryer because they get worn out so fast that way.
So you want the government to pick winners and you want to do business with a monopoly? This is the opposite of what you would want.
If the product saves me money, and it's _actually_ better, I will buy it in a heartbeat. If you're involving the government it's because one of those things isn't true.
It says this is both a "heat pump" and also "storage" AND says that it will run when electricity is cheap or plentiful. Thus:
1: Where does it pump the heat from? (Or is this not really a "heat pump" and instead is using resistive heating?)
2: How long does it store heat? Is this something that will store heat on a 24-48 hour basis, or will this store heat during the spring / fall when longer days mean extra power from residential solar, and then use the heat in the winter?
3: Is the unit itself "warm" when storing heat? Or is the heat stored in a purely chemical way and needs to run through a catalyst or similar to get it back?
4: Can this be scaled up for general domestic heating?
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Just an FYI: There are plenty of schemes with resistive electric water tanks to store heat when power is cheap.
As it works on phase change (e.g. think of melting ice) heat is added (or removed) without changing the temperature of the store (which, I guess, might be hotter or colder than where the heat is extracted or used).
Depending on the needs, resistive heating can get hundreds of degrees hot, but the best heat pumps that I know of can only raise the temperature about 60 or 70° f.
2. With good insulation you can easily store heat for a day which is all you need. You're never going to get close to storing summer heat for the winter. That's not impossible but not feasible for something this scale (and not cost effective at any scale).
3. You just heat it up and cool it down. There are no fancy chemical processes happening other than the phase change. It's exactly like a phase change hot/cold pack you can buy on Amazon.
4. I'm pretty sure this is designed for domestic heating...
It's kind of an obvious idea tbh. I don't think they've done anything super innovative... They made an aluminium heat sink..
This is ground basically. How deep varies but few meters underground you basically have average yearly temperature. You could pump heat from house to the ground to take it out from the ground during winter.
my childhood public school took us to some big commercial building- I think it was Sears' HQ- and they proudly showed us the huge blocks of ice providing chill during the day.
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
https://en.wikipedia.org/wiki/Yakhch%C4%81l
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.)
unrelated: a simple technical solution to your window problem would be home assistant and a few sensors to notify you when the windows are open too long or open when too cold inside.
Come to think of it, if we had a big salt slurry that transitioned at 72F in the floors, that would probably do the right thing. It’d create a step function making it hard to heat above 72, or cool below it.
I wonder how much density changes as these things transition. Would a static pool (mixed by freezing) work, or would it need a pump?
It's a double edged sword. In my country everyone bought pellet stoves because of the subsidies, hundreds of companies popped up, now that the subsidies have been phased out, 90% of the companies went down, with their support and warranties of course. The 10% that managed to survive increased their prices, which is easy to do once 90% of your competitors went bust
People who thought they'd save money by having the government (their taxes really) pay the bill are waking up 5 years later with expensive maintenance, the first units are starting to fail and need to be replaced but they can't afford it without the 50%+ subsidies. Not to mention that the prices pellets goes up and down faster than your average shitcoin.
https://www.tn.gov/environment/program-areas/energy/state-en...
(I don't understand the implications, it was just surprising when I heard that.)
This kind of thing is why I don't like bans like this. The specifics matter a lot.
What an exceptionally moronic thing to ban, the market solves this naturally. Resistance heaters are 100% efficient whatever fraction of the year is heating days. So if that's 1/2 the year and the water heater can't last 16yr because of water quality the heat pump heater will never pay you back.
This reminds me a lot of the time some jerks in west coast desert states convinced the feds to regulate plumbing fixtures so that eastern "we take from the river and put back in the river" municipalities that have more water than they know what to do with have to suffer through low flow everything.
Running cost of heat pumps for heating is much much lower than resistive heating.
A 6kW 240V EWH uses 25A, it’ll need #8 wire and a 35A or 40A breaker.
An equivalent HPHW would use 1.5kW at 240V, or 6.25A. You can use #14s and a 15A breaker.
It does seem a little silly to have these chains of heat pumps all working in various directions. I read about "cold district heat" in a sibling comment which circulated lukewarm water to use as a heat sink or source with heat pumps. Maybe something similar could be done with a water or refrigerant loop through the house. Probably not economical to do all the plumbing though.
Heating water is very energy intensive, fridges are a rounding error compared to water heaters
Bus sized because that amount of thermal mass is bound to take up a lot of space, but capable of being buried so that it doesn’t actually take up property space.
A 100m3 (100,000 litres or 26,500 gallons) cylindrical water tank (approx 5x5m) buried and insulated with 50cm of XPS could provide around 4000kWh of deliverable heat throughout winter. Which would be more than enough for heating and domestic hot water for my house.
In the summer you'd use solar thermal to charge it to 85c. In the winter you'd run water through underfloor heating and discharge it to 35c (so you just need a mixer valve and pump).
The structural engineering part of it isn't actually that complicated (with a garden on top, not a house). You can buy plastic water tanks of that size, it just needs to be buried and have XPS foam placed around it.
Because it's volume, it scales up well. An extra one meter in each direction would increase the volume by around 60%, but you have a lower overall heat loss, so the heat capacity would more than double.
The important part of it is the XPS foam though, without this the loses are too great and you don't retain any heat. This is why insulating your foundation and slab is so effective.
You can then use a heat pump that's optimized for the expected temperature range and you don't even need to insulate your water storage tank - you actually want the cold in winter to seep out into the surrounding soil, free energy.
In summer you have cold storage for your AC.
And being on an alluvial plain, if I filter out all the rocks larger than a pea, a good 90+% of what is dug out can immediately be trucked away.
And being on an alluvial plain, if I filter out all the rocks larger than a pea, a good 90+% of what is dug out can immediately be trucked away.
Does seem like a lot of added complexity (and likely machinery cost) though.
I live in Switzerland where these are available. A Cowa 58 [0] costs CHF 4692 [1] and stores up to 13.5kWh. If you're heating the water with a heat pump, that's ~6kWh of electricity, so ~CHF 782/kWh.
I'm in the process of installing a 33kWh battery and the battery + inverter cost CHF 13600 in total for just the hardware, so ~CHF 482/kWh.
If you add solar panels, the inverter does double-duty producing AC from both the battery and the panels. The battery does double-duty producing both hot water and allowing you to use solar energy outside the times when the sun is shining.
That said, having ordered a heat pump recently and being in the process of having solar + batteries installed, the amount of electrical work needed for the solar/battery install is substantially higher than was needed for the heat pump and here, the labour costs quite a lot, pushing the upfront cost difference even higher.
I think that's where these heat storage things fit in: they have a much lower upfront cost. No matter how cheap the battery, for it to be useful in a Swiss residence, it needs to output a substantial amount of 3-phase power (3-phase is standard here, even in most apartments), which means you need to spend a couple thousand Francs on an inverter and electrical work. These heat storage devices are quite cheap and don't even need someone qualified to handle refrigerants, I imagine they could be installed by a normal plumber.
That reduced upfront cost makes them far more accessible than electrical batteries, at least for now.
[0]: https://www.cowa-ts.com/uploads/files/Dokumente/Datenblaette...
[1]: https://nettoheizungshop.ch/Cowa-COMPACT-Cell-58
Similarly, in mild weather, it is more efficient to burn hydrocarbons and turn it into electricity to run a heat pump than use that hydrocarbon for it's heat energy directly.
Pumping heat is more efficient than making it.
Compared to nearly 100% usable energy from normal solar panels.
Furthermore if you have a heatpump you can convert this electric energy into heat energy with a factor of >3 (COP).
https://www.youtube.com/watch?v=7J52mDjZzto
https://www.youtube.com/watch?v=7zrx-b2sLUs
Unless you live in a cold climate, they are worth it for a discounted energy bill =3
GFL buying a simple resistive-heated clothes dryer, furnace, or tanked/tankless water heater in 2030.
What's all this fuzz about ?