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US companies are producing heat pumps that work below -20F

• sokoloff 4y ago
  > “additional efforts are needed to address common technical and market barriers to wider adoption by consumers – which include performance at temperatures of 5F and below, installation challenges, and electricity grid impacts during peak demand periods.” There are definite market barriers at play. In my house in New England, I tried to replace my aged boiler with an air-to-water heat pump (after carefully verifying, via experiments during a cold week in February, that my heat distribution would indeed work fine at a supply of 130°F). Only one company was even willing to come out and provide a quote and their quote was around 2.5x the costs of "put another boiler in", such that the payback period would be "literally never". If, after doing the research to find out about them and specifically seeking one out, I couldn't manage to make an air-to-water heat pump make sense, I doubt that very many of them are being sold. I suspect it's one of those items that, if more were sold, more firms would sell/install them, bringing the costs into the realm of economically reasonable (and lowering the risk of having a difficult-to-support heating plant in the decades to come).
  • CoastalCoder 4y ago
    My house uses a heat pump + oil-burning furnace. It gives a pretty good combination of efficiency, and ability to handle really cold weather.
    • toomuchtodo 4y ago
      I think this is most of the way to what the future looks like: a high efficiency heat pump with cogeneration, so you can still burn propane or natural gas for heat and limited power to drive the heating system in an emergency (and if you don't have gas service to the premises, you have either a propane tank [1] or an exterior outlet to hook up outside). You must have a solution for when utility power is down for substantial periods of time. During the winter storm that just passed, a friend in the Midwest called that their house had no power and was rapidly cooling. The utility could provide no ETA to resolution. I walked them through (over the phone) safely enough backfeeding enough power from a gasoline generator (outside, with the extension cord run through a basement escape window) into their furnace circuit to bootstrap the furnace (and run the blower fan) to keep the house warm so that the pipes didn't freeze and burst. If the HVAC system had had a small battery and some way to generate power from the heat it was burning, the gasoline generator would've been unnecessary. Perhaps an integrated thermoelectric generator [2]? A standby generator isn't financially practical for most folks ($6k + install). (EDIT: to the safety folks out there possibly concerned, the furnace breaker and main breaker were tripped, and the meter was pulled to prevent any chance of harm to electrical linemen from inadvertently energizing the utility line; take no chances with safety, do not attempt this at home) [1] https://www.amerigas.com/about-propane/propane-tank-sizes https://www.amerigas.com/about-propane/propane-tank-sizes [2] https://patents.google.com/patent/US5427086A/en https://patents.google.com/patent/US5427086A/en
      • Scoundreller 4y ago
        Problem is high efficiency furnaces/boilers require a powered vent, so they need quite a bit of power to operate. And then you’d need to circulate “cold” air/water against the heat exchangers. This usually adds up to several hundred watts.
      • sokoloff 4y ago
        For others interested in preparing for a situation like this, here's a video laying out in reasonable detail what to do.* https://www.youtube.com/watch?v=1JNuovFpCpQ https://www.youtube.com/watch?v=1JNuovFpCpQ * I don't like that they skipped putting a bushing or an NM clamp on the back of the box into the furnace, but otherwise the video looked sound when I watched it a couple weeks ago.
        • jchw 4y ago
          I've been waiting to do this in the event of a power outage; that said, I'm really curious what the current draw of my furnace blower will wind up being. There is a label that suggests it has a peak draw of 8.5A, but that seems like a lot. Still, it seems like a nice backup plan in the event of an outage, even if I only have a couple kWh worth of battery storage.
          • a9h74j 4y ago
            Many furnaces use third-party controller boards with well-known suppliers. You might find in the furnace manual that there are different wire-to-board permutations to allow different fan (interior recirculating blower) speeds. From home testing a few years ago, I recall RMS currents 50%-80% of peak rated draw, but could be mistaken.
          • mikeyouse 4y ago
            What's the model number of your furnace / blower? I've been doing a ton of research in this area as I'm remodeling my place and have several furnaces and duct loops to deal with. From what I've seen so far, unless your unit is super old, the 8.5A is almost certainly just a 'peak' startup current that's overstated as well. Your blower should say something like "1/3 HP" and from there it's straightforward conversion of 1HP = ~750W so a 1/3HP would be 250W. On a 120v service, that's 2 Amp. With maybe 15% efficiency loss, at peak speed, the blower motor wouldn't be drawing more than 2.5A. It could/will draw more than that to start, but literally just for a second or two.
    • wmeredith 4y ago
      Mine is the same with a gas furnace/heat pump combo. It's great.
    • jcadam 4y ago
      My house uses a NatGas boiler and in-floor radiant heat. It also has wood stoves for those -20F (or worse) nights when I need a little supplemental heat (or the power is out and the main heating system is offline). A heat pump would be a waste up here in Alaska esp given I don't need A/C. Just opening the windows and running some fans in the summer tends to do the trick for cooling.
      • throw0101c 4y ago
        > Just opening the windows and running some fans in the summer tends to do the trick for cooling. The problem with 'natural' ventilation is you also get things humidity, pollen, dust, etc coming in as well. One of the major advantages of mechanical ventilation (like HRV/ERVs, which cycle the air) is that things are tempered and filtered beforehand. Sometimes you also want to deal with individual variables: the temperature is fine, but the humidity is off.
        • jcadam 4y ago
          There's the expense of maintaining a central A/C, ductwork, etc., that I'd rather not deal with (not to mention electricity is expensive here). Yes, if the air outside is dirty (forest fires, volcanic eruption, etc.) you've got a point. HEPA filters can help some with this, I suppose. Humidity isn't usually a big issue here most days. If anything, it can be a bit dry (but not as dry as running an A/C would make it). Though, I do have a portable dehumidifier I use when I need to :)
        • a9h74j 4y ago
          Is filtering incoming air (for a mix) necessarily the norm, though? Even in the rare high-performance homes built on spec[ulation], my sense is that filtering incoming air might be omitted, in favor of a single filter acting on recirculation.
          • jcadam 4y ago
            And forced air can be quite dirty (dust/pollen/etc.) if you don't clean your ducts regularly.
    • euroderf 4y ago
      My use case is similar. The oil furnace feeds hot water into a network of radiators. My design goal is to maximize the electricity outage that we can make it thru without frozen pipes, and it has to be on a budget (so no generator or giant UPS). The house is mostly unoccupied (a second home). Operation in an outage has to be fully automatic - it needs an automatic transfer switch I guess. The typical indoor temperature is just 5.5C (42F) - this does not leave much margin for the house to cool down during an outage when outside is like -5C (or -10 or -20). But it turn out that an oil pump and a water circulation pump do not draw THAT much power, so if I can run them off backup power (say, a new car battery plus an inverter), it should last for some time before ice has any chance to form.
    • pridkett 4y ago
      I’ve got the same thing. I did a bunch of tests last year to figure out relative performance and costs of heating my house at various outside temperatures. This included doing fine grained electricity monitoring with an iotawatt and rough fuel oil usage using an ultrasonic sensor. Of course, now I’ve got a ton of data that I haven’t finished building my automation with. And, unfortunately, I’ve got an annoyingly bad Lennox iComfort for my heat pump thermostat and may have troubles building the automation anyway.
  • linuxftw 4y ago
    I recently spoke to a well driller that also does geothermal well drilling. He was telling me that the systems are more or less obsolete at this point, as the air-to-air units have such a high SEER rating that the ground loops really will never pay off.
    • benmanns 4y ago
      Is geothermal any quieter? I was assuming the ground loop pump would be quieter than the air-to-air fan.
      • sokoloff 4y ago
        There's no outside noise in a ground-source system (for all practical values of noise: it's just flow in insulated pipes). The pumps are nearly inaudible inside the mechanical room as well. Inverter-based air-source outdoor units are nearly inaudible during any time when your neighbors are likely to have their windows open. When the weather is uncomfortable enough to have the units need to run at high-speeds, they are no longer inaudible, but the neighbors are likely to have their windows closed.
      • zacharycohn 4y ago
        I'm looking at a system now that is 45 decibels - 10db quieter than my robovacuum which is one of the quietest in the market.
    • implements 4y ago
      What attracted me to geothermal was the year round availability of 50F water - easier to extract winter heat at that temperature, and you could create a simple fan / radiator ducted air cooling system for the summer. The latter would actually store summer heat in the ground, and could be powered purely by solar.
    • Bedon292 4y ago
      I have been doing a bunch of research into geothermal recently and this doesn't seem to match with what I have seen. But it probably also varies a lot by location and such. They appear to still be about twice as efficient as an air to air one, and have less parts and maintenance (no outside unit to deal with). Yes the initial install is a lot higher because of the drilling but that should last for decades. In the US there is also 30% rebate at tax time which helps cut the costs down a bunch too.
  • lizknope 4y ago
    I watch the PBS show This Old House which takes place in the Boston area. The plumber / HVAC guy Richard Trethewey is a fan both ground ("geothermal") and air source heat pumps including the air source heat pumps that work at 0F and heat water for radiant floor heating. I'm surprised that more companies aren't doing it there.
    • maxerickson 4y ago
      The majority of their projects are pretty high end (and they tend to want to demonstrate new technology, because it's more interesting).
      • throw0101c 4y ago
        For the 'project homes', perhaps, but if you're going to go through the effort of building new or re-doing an entire structure, you might as well use the latest and greatest stuff/practices/code. They also have many segments of smaller DIY jobs for simpler fixes/maintenance, e.g.: * https://www.thisoldhouse.com/plumbing https://www.thisoldhouse.com/plumbing
        • lazide 4y ago
          They most likely get funding (in the form of steep discounts or free equipment) from the equipment manufacturers to do those installs. They’re called demo homes in the trades. It’s a good way to buy a bunch of headaches if you do it on your own without manufacturer support.
    • panzagl 4y ago
      The 'cast' of 'This Old House' is mostly MIT MechE grads who figured out they could make more money doing renovations for Route 128 techies than burning themselves out working at their companies.
      • throw0101c 4y ago
        Oh yeah, Richard Trethewey and Tom Silva are definitely MIT guys: * https://www.thisoldhouse.com/21071273/richard-trethewey https://www.thisoldhouse.com/21071273/richard-trethewey * https://www.thisoldhouse.com/21071309/tom-silva https://www.thisoldhouse.com/21071309/tom-silva * https://www.thisoldhouse.com/cast https://www.thisoldhouse.com/cast
  • ableal 4y ago
    > their quote was around 2.5x the costs of "put another boiler in", such that the payback period would be "literally never". Doesn't that depend on the costs of both energy sources? Last year I made a similar choice, albeit at smaller scale, just for one water heater. Picked an electric heater with heat pump, also cost 2.5x more than plain electric, but 1/3 the energy cost. It will take a few years to pay back ...
    • sokoloff 4y ago
      > Doesn't that depend on the costs of both energy sources? Yes, it depends on the costs and efficiencies of the competing energy sources, the difference in capex, the annual building heat load, the projected lifespan of each source, annual maintenance costs, and the interest rate.
  • dashundchen 4y ago
    Was it a company that also did gas boilers? If it's not a company that solely does heat pumps, I have heard a lot of contractors will give outrageous estimates because gas is simpler for them and they don't want to do it without the huge markup. I had ground source heat pump installed with vertical wells in a city by a dedicated geo installer. The cost with tax credits came out not much more than a high end gas furnace and water heater. Going airsource would have been even more cost competitive, especially with the federal tax credits in place starting in 2023.
    • sokoloff 4y ago
      They did. To (only partially) guard against that, I made it clear that I wouldn’t be hiring them to hang a gas boiler. (That still allows them to prefer someone else’s gas boiler job over my air-source job, but at least prevents me bidding against myself.) And there definitely would be more labor, more piping, and more electrical work to switch to an ASHP; that’s part of the market forces problem that is hard to overcome with anything other than large price increases for gas or larger direct subsidies for switching.
  • chris222 4y ago
    Was it the company mentioned in the second half of this show: https://youtu.be/TlX5z32T1J4 https://youtu.be/TlX5z32T1J4 Air to water is pretty new technology for the U.S. As you mentioned most oil boiler hydronic systems are spec’d for a much higher temp (like 160 to 180F). I’ve been curious myself if you can salvage any of the existing baseboards with a 130F supply. I have a 5 head mitsubishi cold weather mini split installed last year but I am still keeping my oil boiler for now for domestic hot water and supplemental heat. If I could switch that to an air to water heat pump for a reasonable cost that would be nice.
• ethagknight 4y ago
  Anyone know how these pumps manage to squeeze enough heat out of ambient air to make it worth the while? -20 is down there! I understand how heat pumps work, but what's the differentiator?
  • contravariant 4y ago
    It helps if you look at it as temperatures in Kelvin, to bring something from 250K to 300K requires a 20% increase, which can be done by an ideal engine at an efficiency of 300/(300-250) = 6. Sure you can't ever reach that ideal but the upper limit is high enough to make it worthwhile. I'm not fully sure at what point it stops being worth it, but anything above 150K can get an efficiency of more than 200%, in theory at least, and 150K is way above any reasonable ambient temperature. As far as I know the ideal is not even that hard to approach it's just how to do it in small scale and quickly that is the problem.
    • fallingknife 4y ago
      What does an efficiency above 100% mean?
      • contravariant 4y ago
        It means you transfer more heat than work put into the system.
      • supertrope 4y ago
        Instead of burning fuel to generate e.g. 1500W of heat, a heat pump uses 500W of electricity to transfer heat inside generating the same 1500W heating effect.
      • Qwertious 4y ago
        It's a multiplier for the electrical input - if your heat pump is 400% efficient, then it means the electricity is being 100% turned into heat, plus 3x as much heat is being sucked in from outside.
  • 4y ago
• ape4 4y ago
  -29C for non-Americans. Its a prototype.
• brilee 4y ago
  I wrote up a brief discussion here on the boiling points of refrigerants https://www.moderndescartes.com/essays/refrigerants/ https://www.moderndescartes.com/essays/refrigerants/ The long and short of it is that if the heat pump works below -20F, then the boiling point of the refrigerant must be below -20F. This, in turn, implies a higher pressurization (as per the Clausius-Clapeyron eq) required in order to achieve a T_hot of 80F (or whatever output temperature you want. The higher pressurizations require more expensive components and compressors.
  • Scoundreller 4y ago
    Maybe I’m dumb, but aren’t compressors pressure-agnostic? They just add pressure, right? Other than needing to be a bit stronger to keep from bursting against the higher delta with the ambient atmospheric pressure like the rest of the components.
    • Cerium 4y ago
      In this case there is a higher delta between the system and the atmosphere as well as a higher delta between the hot and the cold side, which is what requires a stronger compressor.
      • Gibbon1 4y ago
        I had a HVAC guy mention that seals are problematic always with non hermetic compressors. Everything larger than a fractional HP system has a shaft seal between the compressor and the motor. Small systems being a pain because there is less refrigerant and no way to monitor the amount.
        • warmwaffles 4y ago
          There is a way to monitor it, but you'd need to put in T-Junctions and add a pressure sensor on the high and low pressure sides. You'd then need to rig up some system to read those pressures. But _you_ would be unfortunately the one that has to do it because I don't think there are any off the shelf solutions.
• pitaj 4y ago
  It was down to -8F (not including wind chill) a couple days ago here. I have a small, old house but I'm considering replacing the old system I have now with a heat pump. My concern is two-fold: - my house is not well air sealed - my house is not well insulated So I worry that I'll need an extremely oversized heat pump in order to have enough capacacity for the coldest days. I suppose having a backup heating source would prevent needing such a large unit. Plus it would provide some amount of redundancy of the heat pump were to fail in the winter. The question then is, should I use electric backup heat, or stick with my existing gas connection? Electric is simpler and there's no exhaust fumes or CO risk to worry about, but gas is still cheaper here I think.
  • coryrc 4y ago
    The best ROI is to insulate and air seal.
    • hn_go_brrrrr 4y ago
      And if you can only do one, air sealing is almost always preferable.
  • jebarker 4y ago
    We live in the Colorado Front Range in a 50 year old house that isn't particularly well insulated. We have a Mitsubishi high-efficiency air source heat pump distributing air through our existing duct work. We have electric backup inside the air handler. Last week it got down to -15F overnight. The heat pump ran throughout and there was only really activity from the electric backup during the occasional defrost cycle. We keep our house pretty warm too as we have a baby. In winter the heat pump seems to have no issues meeting our heating needs albeit at quite a bit higher overall utility cost compared to our old gas furnace. In summer the heat pump is much more efficient than our old AC unit and our solar panels cover >100% of our usage from ~April-Oct. Prior to installing the heat pump we did as much insulating as we could (mostly attic) and I think that was important for enabling the heat pump to keep up in the cold. The nature of the heating is lower level and continuous compared to the occasional blasting from a gas furnace, so you do want to prevent rapid leakage of heat from the house.
• PreInternet01 4y ago
  Having heat pumps that can operate during arctic freezes is of course, and pardon my pun, pretty cool, but I wonder which percentage of the consumer market actually requires this? Especially keeping in mind that your pump not actively heating its internal storage for a few hours every day is not a huge issue: it only becomes problematic when the external heat exchange is unavailable for 6-8 hours or so. Another comment in the article, regarding electricity grid impacts during peak demand periods, is more interesting to me. Currently, there is no mechanism whatsoever for heat pumps to automatically shift their grid draw (or re-delivery) to certain time slots, and/or to coordinate those slots with other units nearby. Both of these would greatly help to balance the grid, but won't be available until standardization gets off the ground and expensive retrofits are done. That's a shame, really...
  • eternityforest 4y ago
    It's usually about 35F to 22F daytime when I turn on the heater, so efficiency at low temperatures would be the main thing that matters. It doesn't get to -20F that often most years, but it does hover around -5F for days at a time on occasion. Current generation heat pumps are probably still worth it but ultra low temp performance would be nice.
  • therealcamino 4y ago
    There may be no existing, comprehensive central management of electrical demand from heat pumps but that doesn't mean there are no mechanisms whatsoever, because there are systems already for regulating AC demand. In our region of the US, residential customers can opt in to a system where the electric utility can remotely disable their air conditioning compressor during times of peak load, in exchange for discounts. There are agreements on how long that can remain in effect, which would probably have to be stricter for heating systems, and probably have other safeguards added. There are also non-centralized AC mechanisms through Nest thermostats, where they can pre-cool buildings early in the morning to spread load out more evenly during the day.
    • rainsford 4y ago
      Maybe just as important, whether or not there is a centralized mechanism for dealing with it, utilities already have exactly the same load problem with AC in the summer and have more or less figured out how to deal with that. It may be different in places where AC is less widespread, but in most of the US I wouldn't expect heat pump load issues to be much of a problem in the winter.
• moffkalast 4y ago
  Do we really need heat pumps that work that far into the negative? You can always turn on an internal resistive heater to compensate after all. Not quite something you can do on the other end though, when trying to cool with exceptionally high ambient temperature. It's such bullshit that the physics of this universe does not allow for resistive cooling.
  • eppp 4y ago
    Resistance heat is extremely expensive to operate. Burning something is cheaper.
    • moffkalast 4y ago
      Well it is technically 100% efficient which is more than one can say for most things, but it's true that heat pumps can be far better than that.
  • zdragnar 4y ago
    The problem is that if everyone comes off of fossil fuel heat and switches to heat pumps, you need a grid that is capable of delivering enough eletricity to power simultaneous resistive heating to every house... because every house is going to need resistive heating at the most dangerous time to not have any heat at all. These cold snaps tend to also coincide with extreme winds and other weather events that can take out power lines, so a stressed grid just compounds the issue.
    • jupp0r 4y ago
      On top of that, it's also the time when you need the most energy for heating because it's the coldest.
• a_square_peg 4y ago
  We need heat pump that work below -20F like we need an electric car that can go 1000 miles in a single charge - which is we really don't for the 99% of the use case. What's needed is a heat pump that's cheaper to install than gas furnace or oil boiler for the 80% of the population. On few days of the year when it's -20F or below, it's ok to use resistive heater as a back up.
  • Someone1234 4y ago
    Isn't the primary issue not the cost of installation, but rather the cost of the fuel? Natural gas in most of the US is far cheaper than electricity, and even if heat pumps are theoretically more efficient than natural gas (energy in:heat out), if the fuel is two or three times cheaper none of that matters.
    • onlyrealcuzzo 4y ago
      In most places in the US, in normal working conditions, Heat Pumps are 30%+ cheaper than a gas furnace to run. However, in some really cold places like Chicago, Minneapolis, etc - the days where current heat pumps are inefficient might be enough to make it cheaper to always run gas. OP is proposing to have both systems and only run the gas furnace on extreme days - which would lead to a ~30% reduction in running costs. I suspect the CapEx of having two heaters wouldn't make sense, though. It'd be better to just have a hear pump that can run efficiently at colder temps.
      • Scoundreller 4y ago
        I think it’s the opex of 2 grid connections that messes with the numbers. Depends on how your utility charges, but I feel like many/most sell you the gas roughly “at cost” and then some fixed monthly delivery/connection charge that covers their regulated rate of return on their network equity. Oil or propane supplemental heat might be cheaper than Natgas supplemental heat. My money is on wood pellet stoves for supp heat for those that don’t require full automation. Or maybe even dirty coal…
      • BobbyJo 4y ago
• yosito 4y ago
  Meanwhile, most people in the US don't even know what a "heat pump" is, and think that "air conditioners" are inherently wasteful and bad for the environment.
  • Scoundreller 4y ago
    It is kinda a concern with heat pump rollouts in Europe: now that people that didn’t have air conditioning before will have it and will adopt it. Having said that, too much of my EU family still thinks air conditioning makes you sick… and a lot of the latest germ theory (aerosol transmission or respiratory viruses) is confirming they might be right. Ugh. At least the rental cars usually have AC nowadays.
    • newZWhoDis 4y ago
      That’s absurd, AC doesn’t “make you sick”. What basis could anyone have for such a claim?
      • SoftTalker 4y ago
        AC evaporators and condensate pans can breed bacteria and mold. At best this can be smelly, at worst it can make you seriously sick. See the history of Legionnaires disease.
        • nottorp 4y ago
          If you have individual room split units you just clean them yearly or so. Just open the interior unit and spray it with the cleaning solution. Smells nice too :) Whole house a/c systems like the US has are an entirely different matter... don't know how you clean all those ducts.
          • anikom15 4y ago
            I’ve never seen anyone clean their A/C system.
• svdr 4y ago
  A nice explanation of the working of heat pumps from Technology Connections: https://www.youtube.com/watch?v=7J52mDjZzto https://www.youtube.com/watch?v=7J52mDjZzto
  • a9h74j 4y ago
    Great channel. Doesn't he lament that US installers are still charging "don't bother me" enormous premiums on heat-pump installs?
    • therealdrag0 4y ago
      Yep. And he’s installed, I believe, multiple split units himself.
• Scoundreller 4y ago
  I think the ultimate combo will be heat pumps + wood pellet stove as supplemental heat. Then you can cutoff the gas grid connection and its associated standby/account/blah blah charges. It’s a big sunk cost in a lot of places that messes with the economics of switching to heat pump as primary heat. Pellet stoves are semi-automated. Around 90% efficient. If you already have central heat pumps, you can install one and let your HVAC circulate the heat around. Can stockpile as much fuel as you want. Cheaper than oil or propane and not much more expensive than firewood once accounting for improved burn efficiency. Just need to empty the ash gray once a week or so, and dump a nice smelling bag in for every ~24h of operation. Relatively straightforward install: just need a wall to punch through and a standard power outlet. Minimal clearance requirements. Fun to watch the fire tornado. Big downside is they need some electricity (mainly for for the powered vent). Hit or miss when it comes to insurance companies that think explosive gas systems or high current electric devices are safer.
  • 2OEH8eoCRo0 4y ago
    Pellet stoves require electricity to run the auger. Also- nobody gives away free pellets but it's pretty easy to come by free wood people are giving away.
  • inthepipe 4y ago
    Gas heaters also have around 90% efficiency, I think. It seems like gas is strictly better?
    • Scoundreller 4y ago
      Depends on your constraints. The CO2 round trip is a lot longer for gas.
• deleted 4y ago
  [deleted]
• agentwiggles 4y ago
  My Senville mini split claims to work at temps down to -22F. During this recent winter storm, temps got down to about -10 where I am, and it managed to keep my garage around 50F. Nowhere near comfortable, but pretty damn impressive to be able to keep my relatively poorly insulated garage 60 degrees above the weather. I was quite happy that this storm occurred while I was in Christmas PTO, since my garage is my office. I could have made it workable with a supplemental space heater but it was nice not to have to!
• sneezesForAttn 4y ago
  We just installed a Solstice Inverter Extreme[0] before the the storm hit. The low in our area was -24F. The heat pump is advertised to work at -22F, but was still heating the house at the low. Efficiency and capacity are reduced with as the temperature drops. We have backup resistive heat in the buffer tank of our hydronic setup. It is early but we are happy with the performance during this first cold snap. [0] https://www.spacepak.com/solstice-inverter-extreme https://www.spacepak.com/solstice-inverter-extreme
  • maxerickson 4y ago
    What's the rough cost? (obviously there will be lots of variation based on the complexity of the install, but the ballpark is still interesting)
    • sneezesForAttn 4y ago
      About $10k for the heat pump. NPV is positive for 10 years compared to a propane boiler. This doesn't include installation, but it is doable for the advanced DIY homeowner. The entire system cost $25k + installation. Not cheap, but in our climate we heat 7+ months and it is worth it. The extended federal tax credits help, but our state does not do anything in terms of rebates.
• lizknope 4y ago
  I'd like to see an efficiency curve of this heat pump at -20F, 0F, +20F, +40F I have a heat pump that can be used for both cooling an heat along with a natural gas burner. The installer has set the system to use the heat pump at 40F and above and switch to natural gas at below 40F below based on the efficiency of the heat pump dropping at low temperature. My heat pump is a SEER 18 unit primarily for cooling in the US south so I'm sure a heat pump designed specifically for northern cold climates will be more efficient than mine at low temps but I'd like to see how much.
  • newZWhoDis 4y ago
    Well that installer cutoff was likely waaaaay too high. Your heat pump should be fine to 30F, maybe even 25F before needing gas. Modern systems are 24 SEER and good to -5, and these research units take that to the next level.
    • Majromax 4y ago
      > Well that installer cutoff was likely waaaaay too high. Your heat pump should be fine to 30F, maybe even 25F before needing gas One possibility might be that the unit lacks de-icing circuitry. If that were cut for cost optimization, the unit would still work fine for cooling and for moderate-temperature heating, but anywhere near 30F it would ice up and stop working.
    • bowow 4y ago
      Unfortunately only the very top-of-the-line (very expensive) variable speed compressor units are rated for anything close to 24 SEER / -5F (unless that's what you meant by modern systems).
    • rudedogg 4y ago
      > Well that installer cutoff was likely waaaaay too high. Your heat pump should be fine to 30F, maybe even 25F before needing gas. The parent post was saying it's cheaper to use natural gas at those temps, so that's why the installer did the cutoff there. You can look at COP numbers for heat pumps here: https://ashp.neep.org/#!/product_list/ https://ashp.neep.org/#!/product_list/
• Ottolay 4y ago
  The issue with heat pumps is that most of the ones currently being installed in South East of the US don't work well below +20F let alone 0F or -20F. Most of them are being installed with an electrical resistive backup heat, which is incredibly inefficient. The problem is when a cold spell like Christmas 2022, with temperatures down towards 0F. All the heat pump users switch to resistive backup heat and it overloads the electric grid and we get rolling blackouts. In my opinion, heat pumps are amazingly efficient at moderate cold temps, but they really need propane or wood heat backup for the really cold temperatures instead of resistive heaters.
  • haberman 4y ago
    What is inefficient about resistive heat? Isn't electricity->heat basically 100% efficient? Maybe you are saying that heat->electricity->heat is inefficient, since most electricity is produced from heat inefficiently. I always get tripped up by this, since I live in an area where almost all electricity is hydro. In that case resistive heating seems fine.
    • thatcherc 4y ago
      That 100% efficient figure is correct - you get one Watt of heat for one Watt of electricity. It's just that heat pumps can deliver 3 or 4 Watts of heat for each Watt of electricity (usually quoted at around 300% or 400% efficiency!). Compared to that, resistance heaters aren't as efficient. The explanation that made the most intuitive sense to me is that it takes less energy to move heat from one place to another (air at 273 Kelvin to air at 300 Kelvin, like a heat pump does) than it does to create heat from nothing (like a resistor does). That's why the heat pumps can get deliver more heat to you from the same amount of electricity.
      • haberman 4y ago
        That makes sense, but GP was calling resistive heating inefficient compared with propane or wood heat, which doesn't make sense to me.
• therusskiy 4y ago
  I am lost. Are heat pumps the same thing as split air conditioners that can heat air?
  • ARandumGuy 4y ago
    Air conditioners are heat pumps. They move thermal energy from the inside to the outside to cool a space. In this context, a heat pump refers to the same type of system, but in reverse. Instead of moving thermal energy from inside to outside, you're moving that energy from outside to inside. This can work even when it's cold out, because cold outside air still has a lot of thermal energy that can be moved. The main benefits of heat pumps for heating are twofold: 1) It's significantly more efficient then electric resistive heat, because heat isn't being generated, simply moved around. 2) Heat pump systems can be configured to work to both heat and cool a space. There are very few changes needed to make this happen, meaning that if you need AC, you might as well get a heat pump to do both jobs.
    • therusskiy 4y ago
      Most air conditioners I encountered (as a person from a cold country) had this option. The Samsung one I have works from -15C (which is really not that cold, but still). Is this the same technology just for even colder tempreratures?
  • deleted 4y ago
    [deleted]
  • zip1234 4y ago
    A mini split is usually a heat pump system although some of them use resistive heating. They have been getting much better in recent years.
  • Qwertious 4y ago
    Heat pumps are also known as "reverse cycle air-conditioners".
    • 4y ago
• sandworm101 4y ago
  Cool. But it hit -39c in my area a couple weeks ago. They still have some way to go.
  • Qwertious 4y ago
    If you run copper tubing underneath the frost line, a heat pump can still run at that temperature. Problem is, that's a whole lot of expensive construction for relatively minor energy savings. I hear they're doing it in Alaska, where it's used much more frequently once it's installed.
    • Marsymars 4y ago
      I’m notably south from Alaska and we had a frost depth of 3m a few winters ago. (Caused various problems with water pipes; city instructed many neighbourhoods to leave taps on 24/7.) Expensive to bury stuff below that depth.
      • sandworm101 4y ago
        Fort Mack? Ive spend some time in the prairies too.
        • Marsymars 4y ago
          Not even, Calgary. News article from 2019: https://www.cbc.ca/news/canada/calgary/frozen-pipes-homeowners-frosted-calgary-1.5051182 https://www.cbc.ca/news/canada/calgary/frozen-pipes-homeowne... As alluded to in the article, some people were still having to run their taps for weeks after the deep freeze was over due to the frost depth.
• hooverd 4y ago
  How expensive would it be to run source water to an entire neighborhood for heating and cooling? Have one heating/cooling plant and per building heat pumps.
  • projectazorian 4y ago
    This is called district heating and is not uncommon, some cities in the US have it (it’s used in Manhattan for example) but it’s more popular in Europe and Asia, especially in Scandinavia and former socialist countries. https://en.wikipedia.org/wiki/District_heating https://en.wikipedia.org/wiki/District_heating
    • hooverd 4y ago
      Lots of colleges have steam tunnels too. With individual heat pumps you probably lose some efficiency but the source doesn't have to get as hot or as cold. Doing a residential retrofit sounds like herding cats but in somewhere like Phoenix or Tucson the efficiency gains might be worth it.
  • mlsu 4y ago
    This is frequently done when you have a (very hot) boiler in a power plant or chemical process nearby. A natural gas turbine can't generate electricity very efficiently on even 212f steam, so instead of building some gigantic turbine to get that last bit out, you route the waste heat into a nearby neighborhood.
  • shagie 4y ago
    You are likely interested in Drake Landing in Canada. https://www.dlsc.ca/ https://www.dlsc.ca/ https://en.wikipedia.org/wiki/Drake_Landing_Solar_Community https://en.wikipedia.org/wiki/Drake_Landing_Solar_Community https://www.hpbmagazine.org/content/uploads/2020/04/15Su-Drake-Landing-Solar-Community-Alberta-Canada.pdf https://www.hpbmagazine.org/content/uploads/2020/04/15Su-Dra... It uses solar in the summer to charge a thermal bore which is discharged in the winter. That provides nearly all of the winter heat from the seasonal thermal energy storage. > In 2012 the installation achieved a world record solar fraction of 97%; that is, providing that amount of the community's heating requirements with solar energy over a one-year time span. The third link (the pdf) is the case study from High Performing Buildings on the design of the community. > At first glance, the tidy two-story houses lining two streets in a Canadian suburb look much like the thousands of other homes that surround them; but a district heating system that stores summer’s abundant solar energy to heat the homes during winter makes this community a global pioneer in heat storage technologies for residential space heating. Drake Landing Solar Community proves that such a system can deliver a large fraction (over 90%) of space heating with solar energy in a cold climate. The builder designed the 52 detached single-family houses to appeal to mainstream home buyers who want energy efficiency without sacrificing aesthetic appeal. > Drake Landing provides a real-world example of how conventional heat- ing fuel consumption for space heating can be nearly eliminated, reducing greenhouse gas emissions by more than 5.5 tons per house annually. This is made possible in the harsh 9,027 heat- ing degree day climate by using solar heat collectors with seasonal heat storage, energy-efficient house design and construction, and a low temperature district heating network to distribute the heat to the homes. Note that this isn't more cost efficient - it needs to scale up quite a bit more. > The project development team understood from the outset that the Drake Landing system was too small to be economically competitive with the extremely low cost of natural gas. However, subsequent feasibility studies show that larger systems of similar design can deliver solar energy at about half of the cost compared to Drake Landing, and additional work is underway to improve cost performance further.
• nashashmi 4y ago
  Can they work in pair with co2 capture? Assuming neg 20 deg is co2 liquid point ?
• throw0101c 4y ago
  -22F / -30C capable heat pumps already exist, e.g.: * https://www.spacepak.com/solstice-inverter-extreme https://www.spacepak.com/solstice-inverter-extreme
  • timbit42 4y ago
    Are these using resistive heating when it gets too cold for the heat pump to run, or are these heat pumps actually efficient down to -22F/-30C?
    • throw0101c 4y ago
      AFAICT, they're using the heat pumps all the way down.
• DIVx0 4y ago
  I recently bought some land in Minnesota on a lake. I really want to do a 'no compromise' off-grid setup. Water and septic wont be a problem but I am worried about the heat. I plan to install a huge solar array with a battery house. I'd like to run everything off electric, including the heat. I am in early days of thinking about this and I have time to plan. Anyone have insights on electric heat in ultra cold environments? I assume I can simply scale up a solar array and battery capacity to meet needs (dead of winter, with spans of cloudy days). The only fossil fuels I want on property are for equipment and if I must have it, a backup NG generator. I don't know anyone who runs heat pumps in MN, I'm sure there are some but most folks are burning NG or wood pellets. Electric heat seems relegated to secondary needs, like base boards or heated floors. *edit cloudy
  • inthepipe 4y ago
    What about a wood burning stove? That would be more reliable if you are truly off the grid.
  • Qwertious 4y ago
    Keep in mind that you don't need a traditional electrical battery for heat - storing heat directly is extremely cheap, you just need insulation and thermal mass (i.e. sand/rocks, any old crap will do). There are a fair few systems that use easy summer-solar to generate heat, store it for months at a time and then release the heat in winter. It scales up really well thanks to the cube-square law, which is a euphemistic way of saying it's hard to make a viable system that's really small. But if you're off-grid because you're in the middle of nowhere, then you can spare a few square meters anyway.
  • jupp0r 4y ago
    If you do some back-of-the-envelope math on this, you'll notice that this will be cost prohibitive to implement using batteries.
  • mrinterweb 4y ago
    I have a Mitsubishi Hyper Heat, and it operates to -13f, which would be unheard of in Western Oregon (where I live). So long as your house is well insulated, you'd likely be fine with a heat pump. Pay attention to R-Value for insulation, but if you choose the right materials, that goes a long way for heat storage. I know there exceptions in Minnesota where it can get considerably colder than -13f, but I don't know how long those super low temps are sustained. You would definitely need some sort of emergency heating system. An outdoor propane tank (the larger variety) and a propane heater would likely do the trick as an emergency backup. Not great for air quality in your house, but plenty of people use that as their normal heating.
• londons_explore 4y ago
  The needs of the homeowner and the needs of the grid are at odds with one another here. The electricity grid wants the highest possible efficiency on the coldest days, so that they can serve as many users as possible without building more infrastructure. The homeowner wants the average efficiency to be as high as possible over the whole season, to reduce heating/cooling costs. They don't care if one or two really cold days have bad efficiency, as long as the system has sufficient output to keep the house comfortable. Someone needs to use laws or incentives to align those two - because if every home owner used one of todays heat pump systems, then the electricity grid would fail on the coldest days of the year.
  • itake 4y ago
    If my power goes out (due to ice storms or hurricanes) and I need to rely on a local power supply (battery, solar panels, gas generator), I would like my AC to be as efficient as possible.
    • londons_explore 4y ago
      I didn't explain clearly... AC systems don't have a single efficiency number - they have different efficiencies depending on the indoor temperature, the outdoor temperature, and the number of kilowatts you want delivered. You can generally design any AC system to work efficiently at any specific combination of those variables - but if any variable deviates far from the optimum design point, efficiency will drop. So the real question is, not "I want an efficient system", but "I want an efficient system when it is 20F outdoors, because that's the temperature most of the year".
  • jnsaff2 4y ago
    Are there even heat pumps where efficiency goes down when the delta-T decreases?
    • londons_explore 4y ago
      Yes. If the cold side gets too hot, the pressure on the compressor input gets too high, which means the compressor is doing far more work with every stroke - and input electrical power goes up massively. The motor overheats and the thermal cutout stops it. When the motor is cutting in and out efficiency goes way down. This is an issue with fridges. When you buy a new fridge and first turn it on, it's called a 'pulldown'. The compressor gets far hotter than it ever normally gets in normal operation. Most fridges are only rated for 3 pulldowns in their lifespan - and if you do more than that and the fridge fails, they'll claim it isn't in warranty anymore. And in modern fridges, the software keeps track of how often so they can deny the warranty claim too...
• EVa5I7bHFq9mnYK 4y ago
  My AC runs just fine at -15C (+5F), the problem is when temperature swings between zero and sub-zero, it causes formation of the ice in the outer unit which can break the fan.
  • kwhitefoot 4y ago
    Some heat pumps designed for low temperatures have heaters to avoid the freezing of condensation.
    • EVa5I7bHFq9mnYK 4y ago
      It has this, but I'm talking about the area where the fans are rotating - it's not heated. Rarely, under conditions I described, ice forms there.
• the-alchemist 4y ago
  If you want an (entertaining) deep dive into heat pumps, I can recommend Technology Connection's https://www.youtube.com/watch?v=43XKfuptnik https://www.youtube.com/watch?v=43XKfuptnik and its followup, https://www.youtube.com/watch?v=MFEHFsO-XSI https://www.youtube.com/watch?v=MFEHFsO-XSI
• rohan_ 4y ago
  The furnace at my mother's house in Houston went out and I tried to get her HVAC guy to replace it with a heat pump. (The AC is 30 years old and also needs to be replaced) He clearly had no idea what a heat pump is and came up with the following excuses to not install a heatpump: 1. Heat pumps are only for extremely cold weather 2. The heat from heatpumps is too hot, they only install them at elder care facilities where they need extra heat 3. It's far more complicated than a furnace / AC setup, and will require a lot more maintenance. Not sure what this all means for the industry if common HVAC guys don't even know about heat pumps yet.
• lxmorj 4y ago
  Why not just use a natural gas or electric heating element to heat up the air coming into the heat exchanger when it's below the operating window? In most of the US below zero is a <10 day per year issue. Sure it's terribly inefficient on those days, but I'd bet it's cheaper than maintaining an entire secondary heating system.
  • timbit42 4y ago
    The US grid isn't capable of handling everyone running on resistive heating because traditionally many Americans have used fossil fuels or wood for heating. The US grid needs to be improved for this reason and also for EVs.
• NorwegianDude 4y ago
  How is this news? The last air-air heat pump I looked at was guaranteed working down to -35°C/-31°F.(Mitsubishi Electric UWANO 8700) Is this just the US being far behind when it comes to heat pumps or something?
  • doikor 4y ago
    At those temperatures that pump works at COP of 1. Basically it just switches on the resistive heating element it has for this case. What is being talked about here is having one that actually works as a heat pump at those temperatures instead of a resistive element. Though if you live in a place where such cold days only happen a few days per year tops this is just fine.
• moloch-hai 4y ago
  What no one tells you about heat pumps that work down to 10 degrees F, zero degrees, minus 10 degrees, is that you probably cannot get anywhere near enough BTUs out of your heat pump, at such an outside temperature, to keep your house above freezing. But it will draw a great deal of power getting what BTUs it can. As outside temperature goes down, the amount of heat input, in BTUs per hour (or kilowatts, really) needed to maintain a comfortable temperature rises linearly with the difference. When the difference is greatest, the heat pump can deliver least. So in practice, well above such temperature, your controller has turned it off, and is burning propane instead. Of course, the better-insulated your house is, the fewer BTU/hr it takes to keep it warm. Spending a lot on a beefy heat pump without making sure your insulation is in good shape would be a mistake.
  • timbit42 4y ago
    When the CoP goes to 1, the heat pump should shut itself off so it is not wasting power. That's what mine does. The electric baseboards I used before putting in the heat pump take over at that point.