11 ms·
Pretty soon, heat pumps will be able to store and distribute heat as needed
- rekabis 9mo agoI 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.
- syntaxing 9mo agoSo…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 9mo agoIs 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 9mo agoTo 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 9mo agoGeothermal 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.
- stubish 9mo agoYou 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 9mo agoGround 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.
- fy20 9mo agoI 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.
- eande 9mo agoInteresting practical approach to actual build it. Did you do a cost analyses or RoI?
- bilbo-b-baggins 9mo agoSo… 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.
- rekabis 9mo agoPedantic 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 9mo agoThis 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.
- aidenn0 9mo agoI 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.
- BenoitEssiambre 9mo agoYeah 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/ https://steffes.com/ets/roomheater/ . They don't seem to have large models that could heat a house for months however.
- Neywiny 9mo agoThis 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 9mo agoIn 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. [1] https://www.youtube.com/watch?v=s-41UF02vrU https://www.youtube.com/watch?v=s-41UF02vrU
- syntaxing 9mo agoWith the adoption of sodium batteries, I wouldn’t be surprised if solar panel + sodium battery would outperform this system by a lot.
- belviewreview 9mo agoA 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 9mo agoAlso 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.
- belviewreview 9mo agoThe question is would it cost less over the long term than any other solution. My intuition is it would, at least for a lot of use cases, but it would need to be put into practice and studied to see if this is actually true.
- coffeebeqn 9mo agoThere’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 9mo agoEfficiencies 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.
- Havoc 9mo agoStarting to get more optimistic about our energy future. Things seem to be tracking pretty good
- hedora 9mo agoI 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.)
- direwolf20 9mo agoHeat pump heat is just heat.
- karussell 9mo agoI 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 9mo agoIt’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?
- ifwinterco 9mo agoIt sounds like you need more thermal mass, a traditional brick/stone house wouldn't have that problem
- chickenimprint 9mo agoSo it's a large version of those rechargeable hand-warmers?
- ZeroGravitas 9mo agoYes, 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 9mo agoIIRC 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.
- hnburnsy 9mo agoRelated, 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.
- cucumber3732842 9mo agoIs 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.
- hnburnsy 9mo agoHeat 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.
- sgc 9mo agoElectrical 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 9mo agoIf 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.
- RiceNBananas 9mo ago[flagged]
- chickenbig 9mo agoPerhaps I am missing something; this product already exists as the Sunamp Thermino. https://sunamp.com/en-gb/hot-water-solutions-thermino-range/ https://sunamp.com/en-gb/hot-water-solutions-thermino-range/
- ZeroGravitas 9mo agoIt 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.
- DrScientist 9mo agoIndeed. 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.
- Xylakant 9mo agoit 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 9mo agoI 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 9mo agoHouses 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
- metalman 9mo agothe 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.
- animal531 9mo agoWhere I live we need a way to store and distribute cold as needed.
- burnt-resistor 9mo agoStanford'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?
- Joel_Mckay 9mo agoThey are a very efficient way to get both AC and Heating: https://www.youtube.com/watch?v=7J52mDjZzto https://www.youtube.com/watch?v=7J52mDjZzto https://www.youtube.com/watch?v=7zrx-b2sLUs 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
- burnt-resistor 9mo agoPrivate 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.
- chankstein38 9mo agoThey 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 9mo agoI 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.
- sandinmyjoints 9mo agoWhy?
- cromka 9mo agoMouth burns or bites can lead to cancer
- deleted 9mo ago[deleted]
- Loughla 9mo agoAnd 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 9mo agoI 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.)
- jandrese 9mo agoI'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.
- Tor3 9mo agoI 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.
- stuaxo 9mo agoWhat did you heat with before?
- danielovichdk 9mo agoStones has the ability to store heat and keep cool. What's all this fuzz about ?
- Etheryte 9mo agoIt'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.
- ortusdux 9mo agoI was interested to learn about cold district heating recently, which is basically a municipal scale geothermal system. https://en.wikipedia.org/wiki/Cold_district_heating https://en.wikipedia.org/wiki/Cold_district_heating
- yowayb 9mo agoI went to Moscow in December several years ago and learned they've got one the world's largest district heating systems.
- xattt 9mo agoI 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 9mo agoIn 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.
- gwbas1c 9mo agoThe 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 9mo agoI 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 9mo agoBut 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.
- jcattle 9mo agoThat's the whole point of this, no? Heat pumps can't heat up a large amount of water quickly (like resistive heating can). So if you have a solar peak at noon, where either yourself are producing cheap solar, or there's cheap solar on the grid in general, then you want to use that cheap energy to store heat for later use (like showers in the evening/morning). So the way I see it, is that this material should be able to quickly store heat with the using the low temperatures that heat pumps provide, and be able to store it with minimal losses until it is needed.
- Epa095 9mo agoNot 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?
- 5ersi 9mo agoIt 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).
- thescriptkiddie 9mo agoone 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 9mo agoI feel stagnant water would be more annoying for maintenance than something like salt hydrates.
- Marsymars 9mo agoThere are also existing commercially-available residential units (e.g. Ecombi or Steffes) using ceramic bricks that are in the ~450 kJ/kg range.
- sbierwagen 9mo agoNote 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 9mo agoThanks 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.)
- jokoon 9mo agoI'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
- ryzvonusef 9mo agoPersians had a system since 400 BC: https://en.wikipedia.org/wiki/Yakhch%C4%81l https://en.wikipedia.org/wiki/Yakhch%C4%81l
- jaapz 9mo ago> 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.
- V__ 9mo agoWater (given enough volume) is a pretty good heat storage. https://youtu.be/Bm7L-2J52GU?t=270 https://youtu.be/Bm7L-2J52GU?t=270
- mock-possum 9mo agoIt can be a pretty good ‘battery’ too https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit...
- BrtByte 9mo agoIt's not that heat storage didn't exist, it's that this is closer to a "thermal battery" than a thermal flywheel
- BrtByte 9mo agoAn 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?
- labcomputer 9mo agoThat’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.