5 ms·

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 actu

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.
  - bluGill 4y ago
    Winter is worse than summer, because Delta-t is much bigger. 130f to 70f is 60 degree difference, while -30f to 70f is 100 degrees difference.
    - fomine3 4y ago
      Also deploying solar will solve the problem in summer
altacc 4y ago
There's quite a big market for this, such as a lot of the Nordics, where -15C for a few days is common enough that not having heating then would rapidly become an issue as homes freeze quickly. At those temperatures you have heating on 24/7 to keep the cold at bay. Electricity costs on those cold days are indeed high due to the constant demand of heating.
rektide 4y ago
House heating tends to have controls from thermostats or other devices; I'd tend to look to them for grid-related time-shifting. I did run across a release on a new generation of a heat-pump hot-water heater, which does seem to have some kind of grid-shifting built in. A. O. Smith's Voltex AL, https://cleantechnica.com/2022/12/21/all-i-want-for-christmas-is-a-new-voltex-al-heat-pump-water-heater/amp/ https://cleantechnica.com/2022/12/21/all-i-want-for-christma...
- PreInternet01 4y ago
  > House heating tends to have controls from thermostats or other devices; I'd tend to look to them for grid-related time-shifting Not for heat pumps. In a typical configuration (large heat reservoirs combined with under-floor heating in a well-insulated house), temperature-setpoint changes take 12-24 hours to propagate. So, governing the (in-room) target temperature settings is unreliable/unpredictable. Whereas the in-pump storage temperature is a whole lot more manageable. The old advice "turn your thermostat down at night" therefore also doesn't apply to most heat pump installations -- in fact, it might be disadvantageous. "Select the average temperature you need and don't touch it" is much better advice. Need localized heat/cold? Use another solution for that...
  - a9h74j 4y ago
    > don't touch it" is much better advice Saw one heat pump controller discussed which had a curve set for demand vs outside temperature, and the "thermostat" was to set a delta relative to this.
mindslight 4y ago
The standard large buffer tank is 120 gallons, which stores about 20kBTU at 20F dT. So to last 4 hours you'd need your design heating load to be 5kBTU/hr, which I think is out of the realm of even new construction. You could raise the max water temp and install a few tanks to get in the ballpark, but that's an assumption that most systems won't have. Also I wouldn't be surprised if "operates down to -20F" includes reduced efficiency/output that already relies on the buffer/storage to compensate for.

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.
- bluGill 4y ago
  Winter is worse than summer, because Delta-t is much bigger. 130f to 70f is 60 degree difference, while -30f to 70f is 100 degrees difference.
  - fomine3 4y ago
    Also deploying solar will solve the problem in summer

altacc 4y ago

There's quite a big market for this, such as a lot of the Nordics, where -15C for a few days is common enough that not having heating then would rapidly become an issue as homes freeze quickly. At those temperatures you have heating on 24/7 to keep the cold at bay. Electricity costs on those cold days are indeed high due to the constant demand of heating.

rektide 4y ago

House heating tends to have controls from thermostats or other devices; I'd tend to look to them for grid-related time-shifting. I did run across a release on a new generation of a heat-pump hot-water heater, which does seem to have some kind of grid-shifting built in. A. O. Smith's Voltex AL, https://cleantechnica.com/2022/12/21/all-i-want-for-christmas-is-a-new-voltex-al-heat-pump-water-heater/amp/ https://cleantechnica.com/2022/12/21/all-i-want-for-christma...

PreInternet01 4y ago
> House heating tends to have controls from thermostats or other devices; I'd tend to look to them for grid-related time-shifting Not for heat pumps. In a typical configuration (large heat reservoirs combined with under-floor heating in a well-insulated house), temperature-setpoint changes take 12-24 hours to propagate. So, governing the (in-room) target temperature settings is unreliable/unpredictable. Whereas the in-pump storage temperature is a whole lot more manageable. The old advice "turn your thermostat down at night" therefore also doesn't apply to most heat pump installations -- in fact, it might be disadvantageous. "Select the average temperature you need and don't touch it" is much better advice. Need localized heat/cold? Use another solution for that...
- a9h74j 4y ago
  > don't touch it" is much better advice Saw one heat pump controller discussed which had a curve set for demand vs outside temperature, and the "thermostat" was to set a delta relative to this.

mindslight 4y ago

The standard large buffer tank is 120 gallons, which stores about 20kBTU at 20F dT. So to last 4 hours you'd need your design heating load to be 5kBTU/hr, which I think is out of the realm of even new construction. You could raise the max water temp and install a few tanks to get in the ballpark, but that's an assumption that most systems won't have. Also I wouldn't be surprised if "operates down to -20F" includes reduced efficiency/output that already relies on the buffer/storage to compensate for.