7 ms·

This will become more and more of a problem as buildings switch away from gas/oil heating and switch towards green heat pumps. Heat pumps are particularly bad

This will become more and more of a problem as buildings switch away from gas/oil heating and switch towards green heat pumps. Heat pumps are particularly bad in extreme cold weather. Their efficiency goes down a lot (sometimes 4x), at the exact time everyone needs to use them the most. To be honest, I don't think policymakers have considered this, so I suspect we'll see blackouts on cold winter days quite frequently, with grid operators being reluctant to build double the generation and transmission capacity for just a few hours per year when it's super cold across a wide area.

pifm_guy 4y ago
There are potential solutions... For example, heat pumps could be required to have a reserve storage tank containing enough heat for a day or so, and then at times when the grid is most stressed, they use the reserve heat reservoir rather than the grid. That could be enforced by building code, or by having a monetary incentive to those who have such a system, or a monetary penalty to those who use power on high demand days (although Texas taught us that people don't understand 'prices rise when goods are scarce', and instead see it as 'company jack's prices when I need it the most').
- jazzyjackson 4y ago
  never heard of a heat reservoir, what medium are we talking, water? salt?
  - Schroedingersat 4y ago
    Water is the best option for being driven from a heat pump over a few days in most cases. Phase change materials like sodium acetate or thermochemical systems like NaOH + water seem to work well on paper for long term storage, but haven't received much attention for some reason.
  - ulrikrasmussen 4y ago
    As far as I understand: Water is best for heat pumps because it has a high heat capacity and the operating temperature is below boiling point. Rocks and salt is used for high temperature storage.
- nullc 4y ago
  Water. Cost per joule is really good so long as you have room for the large insulated tank. You can use a heat pump to bring the water up to 180 degF, a fail safe mixing valve to use it to produce 120deg water for the baths and taps, and a heat exchanger for radiant heating loops. It's much more cost effective than batteries to the extent that your energy use is driven by heating demands. If the tank is inside the building envelope the lost heat from imperfect insulation still heats the space too.
ulrikrasmussen 4y ago
For shorter periods, this can be mitigated by local heat storage. You can store 3 days worth of heat in two large insulated pallet tanks filled with water and a heat exchanger. This will also allow owners of heat pumps to draw power when it is cheaper. The source is unfortunately both pay-walled and in Danish, but this engineer has built a cheap system that is on the way to getting commercialized. I'm definitely going to invest in it for my heat pump, as he claims it pays for itself in just 3-5 years: https://ing.dk/artikel/genbrugsplast-viden-vand-ingenioer-paa-vej-med-billig-loesning-varmelager-264208 https://ing.dk/artikel/genbrugsplast-viden-vand-ingenioer-pa...
- rwmj 4y ago
  Surely this takes up even more space - heat pumps themselves are already large enough that it's hard to see where we would put one.
  - eternityforest 4y ago
    Smaller spaces will need less. And very small spaces might need a low enough amount that you can afford phase change material and save even more space.
    - rwmj 4y ago
      In reality a lot of new houses are built to maximize interior space / number of rooms, and minimize lot size hence outside space.
a1371 4y ago
Not an issue. As someone who works on this issues with the very policymakers you are referencing, oh they HAVE considered this. In fact, this is among the reasons that the switch to heat pumps is delayed. Heat pumps can have back up electric heating elements to provide the heating in the extremes. You get a more resilient system than gas. If you have an oil based system, that's worse. There is no good reason to have an oil furnace nowadays.
- colatkinson 4y ago
  > Heat pumps can have back up electric heating elements to provide the heating in the extremes. You get a more resilient system than gas. Sorry if I'm misunderstanding, but wouldn't the backup electric heating elements require, well, electricity to function? I'm no fan of gas, but the idea of losing heating, phone service (the old copper wire systems could function even in a blackout), the ability to cook (since gas stoves are being phased out), and the ability to travel (EVs and some trains) because a transformer exploded is kinda scary. Like, we're putting all our faith in a system that is routinely knocked out by errant tree branches. Maybe we could do buried lines, but given infra costs in the US that sounds... expensive. Someone in another thread mentioned heat reservoirs of some kind, but I have no idea how realistic that is. Even if it buys a few extra hours, that'd improve things dramatically. From the sound of it, you're far more familiar with specific legislation than I, so maybe I'm totally off and all this has been taken into account. But having experienced an extended blackout and my family realizing we couldn't even boil water, I'm apprehensive to say the least. IMO it'd be nice to move away from fossil fuels without betting lives on ConEd doing repairs in a timely fashion.
  - antisthenes 4y ago
    The OP was trying to suggest that at some point the temperatures drop to the point where the heat pump is less than 100% efficient, whereas a backup resistive electric heating element is always 100% efficient. The problem with that is..like you mentioned, it still uses electricity.
  - rightbyte 4y ago
    > we're putting all our faith in a system that is routinely knocked out by errant tree branches. Ye ... one would have thought that JIT delivery would have gone out of fashion after Covid messed everything up. With e.g. wood pellet heating the energy is stored in your home already. No amount of tree branches falling in the wrong places will make you freeze to ice.
geysersam 4y ago
> This will become more and more of a problem Unless we do something about it. Better isolation. More renewables + storage and nuclear power. Continuing to use fossiles is not a viable option.
Saris 4y ago
I would say that only air source heat pumps suffer in cold weather, ground source versions don't really care what the air temperature is.
- brianwawok 4y ago
  But your house walls do. More heat is escaping so you demand more heat from your geo system.

pifm_guy 4y ago

There are potential solutions... For example, heat pumps could be required to have a reserve storage tank containing enough heat for a day or so, and then at times when the grid is most stressed, they use the reserve heat reservoir rather than the grid. That could be enforced by building code, or by having a monetary incentive to those who have such a system, or a monetary penalty to those who use power on high demand days (although Texas taught us that people don't understand 'prices rise when goods are scarce', and instead see it as 'company jack's prices when I need it the most').

jazzyjackson 4y ago
never heard of a heat reservoir, what medium are we talking, water? salt?
- Schroedingersat 4y ago
  Water is the best option for being driven from a heat pump over a few days in most cases. Phase change materials like sodium acetate or thermochemical systems like NaOH + water seem to work well on paper for long term storage, but haven't received much attention for some reason.
- ulrikrasmussen 4y ago
  As far as I understand: Water is best for heat pumps because it has a high heat capacity and the operating temperature is below boiling point. Rocks and salt is used for high temperature storage.
nullc 4y ago
Water. Cost per joule is really good so long as you have room for the large insulated tank. You can use a heat pump to bring the water up to 180 degF, a fail safe mixing valve to use it to produce 120deg water for the baths and taps, and a heat exchanger for radiant heating loops. It's much more cost effective than batteries to the extent that your energy use is driven by heating demands. If the tank is inside the building envelope the lost heat from imperfect insulation still heats the space too.

ulrikrasmussen 4y ago

For shorter periods, this can be mitigated by local heat storage. You can store 3 days worth of heat in two large insulated pallet tanks filled with water and a heat exchanger. This will also allow owners of heat pumps to draw power when it is cheaper. The source is unfortunately both pay-walled and in Danish, but this engineer has built a cheap system that is on the way to getting commercialized. I'm definitely going to invest in it for my heat pump, as he claims it pays for itself in just 3-5 years: https://ing.dk/artikel/genbrugsplast-viden-vand-ingenioer-paa-vej-med-billig-loesning-varmelager-264208 https://ing.dk/artikel/genbrugsplast-viden-vand-ingenioer-pa...

rwmj 4y ago
Surely this takes up even more space - heat pumps themselves are already large enough that it's hard to see where we would put one.
- eternityforest 4y ago
  Smaller spaces will need less. And very small spaces might need a low enough amount that you can afford phase change material and save even more space.
  - rwmj 4y ago
    In reality a lot of new houses are built to maximize interior space / number of rooms, and minimize lot size hence outside space.

a1371 4y ago

Not an issue. As someone who works on this issues with the very policymakers you are referencing, oh they HAVE considered this. In fact, this is among the reasons that the switch to heat pumps is delayed. Heat pumps can have back up electric heating elements to provide the heating in the extremes. You get a more resilient system than gas. If you have an oil based system, that's worse. There is no good reason to have an oil furnace nowadays.

colatkinson 4y ago
> Heat pumps can have back up electric heating elements to provide the heating in the extremes. You get a more resilient system than gas. Sorry if I'm misunderstanding, but wouldn't the backup electric heating elements require, well, electricity to function? I'm no fan of gas, but the idea of losing heating, phone service (the old copper wire systems could function even in a blackout), the ability to cook (since gas stoves are being phased out), and the ability to travel (EVs and some trains) because a transformer exploded is kinda scary. Like, we're putting all our faith in a system that is routinely knocked out by errant tree branches. Maybe we could do buried lines, but given infra costs in the US that sounds... expensive. Someone in another thread mentioned heat reservoirs of some kind, but I have no idea how realistic that is. Even if it buys a few extra hours, that'd improve things dramatically. From the sound of it, you're far more familiar with specific legislation than I, so maybe I'm totally off and all this has been taken into account. But having experienced an extended blackout and my family realizing we couldn't even boil water, I'm apprehensive to say the least. IMO it'd be nice to move away from fossil fuels without betting lives on ConEd doing repairs in a timely fashion.
- antisthenes 4y ago
  The OP was trying to suggest that at some point the temperatures drop to the point where the heat pump is less than 100% efficient, whereas a backup resistive electric heating element is always 100% efficient. The problem with that is..like you mentioned, it still uses electricity.
- rightbyte 4y ago
  > we're putting all our faith in a system that is routinely knocked out by errant tree branches. Ye ... one would have thought that JIT delivery would have gone out of fashion after Covid messed everything up. With e.g. wood pellet heating the energy is stored in your home already. No amount of tree branches falling in the wrong places will make you freeze to ice.

geysersam 4y ago

> This will become more and more of a problem Unless we do something about it. Better isolation. More renewables + storage and nuclear power. Continuing to use fossiles is not a viable option.

Saris 4y ago

I would say that only air source heat pumps suffer in cold weather, ground source versions don't really care what the air temperature is.

brianwawok 4y ago
But your house walls do. More heat is escaping so you demand more heat from your geo system.