3 ms·

You clipped out the qualifying phrase, “as far as the article is concerned”, dumping a few extra MW of electricity for 30 mins or a few hours. I don’t see a nee

You clipped out the qualifying phrase, “as far as the article is concerned”, dumping a few extra MW of electricity for 30 mins or a few hours. I don’t see a need presented in the article to rapidly switch a heating element on and off a few 1000 times a second.

benj111 8y ago
Grid frequency stabilisation would require that. I'm not actually sure that that would be the major problem. A heat pump is basically a motor, which can cause a lot of noise in electrical circuits. I'm not sure you would want 1000s of electric motors turning on in unison. I wouldn't like to say whether that is a solved/solvable problem though.
- throwawaycanada 8y ago
  I don't think frequency stabilization would require that. Unless there is some complex approach I simply can't imagine.
  - benj111 8y ago
    You don't need it to switch on and off 1000s of times a second (is that what you're referring to?) you need it to switch fast enough that it could do that though. If it takes too long you would get brown outs and surges.
- Dylan16807 8y ago
  > Grid frequency stabilisation would require that. The grid has a lot of inertia and a motor can go from full load to none, or from no load to extra-high startup load, in a fraction of a second. So we're back to "just as fast" for this use case.
  - benj111 8y ago
    "The grid has a lot of inertia" Where does the inertia come from? I understood inertia in the grid to come from turbines and motors spinning up and down, which seems to be different from what you're suggesting? Capacitance in the wires?
    - Dylan16807 8y ago
      The inertia largely comes from all the turbines and synchronous motors that stay connected. With something like a heat pump compressor, you're connecting or disconnecting it completely with the flip of a switch. It's also an asynchronous motor and unable to feed power back into the grid at all, it's a pure load.
      - benj111 8y ago
        Ok I don't understand how that kind of inertia would help in this situation. If a turbine is running, and supply and demand are at equilibrium, if you then added another load, that inertia wouldn't help maintain equilibrium, it would slow down spinning up the turbine hampering that goal, wouldn't it? To put it another way. Say if energy use jumps X%, inertia may make up Y% difference in the short term, you'd still have to put in more than X% in the slightly less short term, and it would take longer to make up the Y% shortfall. Is the Y% shortfall not big enough to be important here.
        Dylan16807 8y ago
        > Ok I don't understand how that kind of inertia would help in this situation. If a turbine is running, and supply and demand are at equilibrium, if you then added another load, that inertia wouldn't help maintain equilibrium, it would slow down spinning up the turbine hampering that goal, wouldn't it? If you add more load, you start dragging down the frequency. The more inertia you have in the turbines, the less the frequency is impacted. I'm not sure what you mean by "spinning up a turbine" in this situation. Do you mean to produce more power? You don't spin turbines faster to do that. > To put it another way. Say if energy use jumps X%, inertia may make up Y% difference in the short term, you'd still have to put in more than X% in the slightly less short term, and it would take longer to make up the Y% shortfall. Is the Y% shortfall not big enough to be important here. Yes, you have to make up the deficit. But the alternative means having a brownout. In a choice between "drain some inertia to cover the increased load, then overproduce by .1% to refill the inertia" and "don't cover the increased load, voltage freefalls until load drops", I prefer the former.
IndrekR 8y ago
Maximum switching resolution is about 10ms in Europe (50Hz) and 8ms in the states (60Hz). As you usually switch at the zero crossing. In real life it is usually two-three orders of magnitude longer due to calculation and communicaton overhead.

benj111 8y ago

Grid frequency stabilisation would require that. I'm not actually sure that that would be the major problem. A heat pump is basically a motor, which can cause a lot of noise in electrical circuits. I'm not sure you would want 1000s of electric motors turning on in unison. I wouldn't like to say whether that is a solved/solvable problem though.

throwawaycanada 8y ago
I don't think frequency stabilization would require that. Unless there is some complex approach I simply can't imagine.
- benj111 8y ago
  You don't need it to switch on and off 1000s of times a second (is that what you're referring to?) you need it to switch fast enough that it could do that though. If it takes too long you would get brown outs and surges.
Dylan16807 8y ago
> Grid frequency stabilisation would require that. The grid has a lot of inertia and a motor can go from full load to none, or from no load to extra-high startup load, in a fraction of a second. So we're back to "just as fast" for this use case.
- benj111 8y ago
  "The grid has a lot of inertia" Where does the inertia come from? I understood inertia in the grid to come from turbines and motors spinning up and down, which seems to be different from what you're suggesting? Capacitance in the wires?
  - Dylan16807 8y ago
    The inertia largely comes from all the turbines and synchronous motors that stay connected. With something like a heat pump compressor, you're connecting or disconnecting it completely with the flip of a switch. It's also an asynchronous motor and unable to feed power back into the grid at all, it's a pure load.
    - benj111 8y ago
      Ok I don't understand how that kind of inertia would help in this situation. If a turbine is running, and supply and demand are at equilibrium, if you then added another load, that inertia wouldn't help maintain equilibrium, it would slow down spinning up the turbine hampering that goal, wouldn't it? To put it another way. Say if energy use jumps X%, inertia may make up Y% difference in the short term, you'd still have to put in more than X% in the slightly less short term, and it would take longer to make up the Y% shortfall. Is the Y% shortfall not big enough to be important here.
      - Dylan16807 8y ago
        > Ok I don't understand how that kind of inertia would help in this situation. If a turbine is running, and supply and demand are at equilibrium, if you then added another load, that inertia wouldn't help maintain equilibrium, it would slow down spinning up the turbine hampering that goal, wouldn't it? If you add more load, you start dragging down the frequency. The more inertia you have in the turbines, the less the frequency is impacted. I'm not sure what you mean by "spinning up a turbine" in this situation. Do you mean to produce more power? You don't spin turbines faster to do that. > To put it another way. Say if energy use jumps X%, inertia may make up Y% difference in the short term, you'd still have to put in more than X% in the slightly less short term, and it would take longer to make up the Y% shortfall. Is the Y% shortfall not big enough to be important here. Yes, you have to make up the deficit. But the alternative means having a brownout. In a choice between "drain some inertia to cover the increased load, then overproduce by .1% to refill the inertia" and "don't cover the increased load, voltage freefalls until load drops", I prefer the former.

IndrekR 8y ago

Maximum switching resolution is about 10ms in Europe (50Hz) and 8ms in the states (60Hz). As you usually switch at the zero crossing. In real life it is usually two-three orders of magnitude longer due to calculation and communicaton overhead.