10 ms·

This is not a battery, or a battery killer, and the author surely knows better. This is a distributed load bank, located in places the heat can be put to good u

This is not a battery, or a battery killer, and the author surely knows better. This is a distributed load bank, located in places the heat can be put to good use. Interesting idea though. The paper seems like it’s pushing a product instead of pushing concepts, because the applicability of this concept goes much broader than the article goes into, for greater benefit to the consumer. A heat pump (a compressor and some fans) can be switched on or off just as fast as a heating element, at least as far as the article is concerned. The water heater switch is a dead simple solution though, credit due for that. A bit of a rabbit trail here: A heat pump would not provide as much potential load, but it gives the flexibility of working for both heating and cooling, and also puts the electricity to better use. The key would be to put a cheap heat storage element in between the customer-premises heat pump and the final use, so that the utility can fire up the heat pump regardless of the customer’s need, and the customer has a huge bank of hot or chilled water at their disposal. Combined with a radiant floor heating system, and tied into a water-source HVAC system, this is a real energy efficiency boon by taking waste energy and getting it past the meter into the customer premises. Go ahead and throw a Steffes(tm) resistance heater in the water heater while we are at it. Have your cake and eat it too.

kragen 8y ago
> A heat pump (a compressor and some fans) can be switched on or off just as fast as a heating element, This is not true, and the article specifically addresses this. A heating element can be switched on and off roughly five orders of magnitude faster (100 000× faster) than a heat pump.
- ethagknight 8y ago
  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.
- IndrekR 8y ago
  This is not really an issue. Usually you have 4-5 seconds to react for the "hot reserve". Also for the known peaks you can preventively switch off the loads (it is amazing what happens at 7:02am when everybody switches on their kettle at the same time, even worse with water supply and flushing peaks). In addition such systems sometimes measure frequency deviation and switch off/on the load when it goes out of bounds. The result is that this works really well for fast balancing as soon as you have few hundred installed spots in one grid. And there is real money in it with ROI 1..3 years for the service provider. Disclaimer: my electronics engineering company has worked with research, design and engineering of such load balancing hardware
- adrianmonk 8y ago
  I'm not an expert, but I'd think letting external factors control the switching on/off of your heat pump would have two downsides: (1) efficiency, and (2) wear and tear. If you're talking about a heat pump used in air conditioning, at least, longer cycle times result in better dehumidification and higher efficiency. If you interrupt the cycle, you're effectively short cycling.
radicalbyte 8y ago
My father works in the heating world. He installed a large efficient storage water heater in the house which would basically warm the water in one go at 5am and provide it to the house all day. What I don't understand from the article is why this is being controlled by the grid? The US is a market system, can't I buy a smart immersion heater which can then react to real time pricing information? So I warm my water up at times when the grid are paying people to use electricity? That places the incentives correctly: a) The entity making the investment in a new heater also gets the financial benefits thereof. b) What's to stop your electricity supplier making your water 5% hotter every year to boost their revenues?
- benj111 8y ago
  "What I don't understand from the article is why this is being controlled by the grid? " Hypothetically if you bought your own you would need a smart meter so you're electricity company knew exactly when you had used power, there also needs to be a system to communicate to your smart appliance, to tell it to turn on. Neither of these really exist so I suppose its sensible for the utility to take ownership to iron out kinks, feel out how in works in practise and stuff. To clarify, smart meters do exist, I don't believe they have the accuracy of metering needed for this application though.
  - bdamm 8y ago
    The modern smart meters are quite accurate, much more accurate than the mechanical ones, usually to the ratepayer’s chagrin. The modern meters will pick up an induction spike from a noisy motor such as in an inefficient refrigerator or fan, where the older generation would not. How accurate does it need to be?
    - benj111 8y ago
      Its the time accuracy that matters, if its for frequency stabilisation then you need granularity in the order of seconds, rather than minutes as I believe smart meters are at the moment.
benj111 8y ago
I was trying to work out their attitude to heat pumps too. Its almost "they're too efficient, lets use something that uses more electricity" ?! I don't share your concerns with calling it a battery though, it stores energy. Combined with a peltier it could generate electricity with that energy. If it eases marketing, and gets this into peoples homes, I'm all for it.
throwawaycanada 8y ago
I did the math on this once. For residential it is not realistic due to the amount of water you would need to store. For commercial I think you would need a small lake.
- ethagknight 8y ago
  Correct, if you are trying to utilize it for a sole method of heat and cool. You will still need to dump excess / add additional through more conventional means, depending on local climate. To your underlying point, none of the added complexity is worth the effort unless a) the utility is paying you to take the excess load and/or b) someone really innovates on a slick, simple package.
amluto 8y ago
There are a couple downsides here. When sizing a climate control system of any sort, it’s nice to size it such that, at full output, it will be just barely sufficient for the worst case usage. If you use it for demand response and time-of-use optimization, you either need to size for a worst-case day such that it’s still powerful enough when it’s switched off at expensive times or you need to store heat or cold for multiple days. Second, while a simple-ish hydronic system is great for heat, it’s less ideal for cooling. You need to make sure that a cooling system can remove sufficient water vapor to keep a comfortable humidity or you need a separate dehumidifier. (Ideally every new building in a humid climate would have independent dehumidification anyway, so this is not a show stopper.). It’s also important to avoid condensation in bad places — if you cool your floor or ceiling much below the dew point, you have a problem.

kragen 8y ago

> A heat pump (a compressor and some fans) can be switched on or off just as fast as a heating element, This is not true, and the article specifically addresses this. A heating element can be switched on and off roughly five orders of magnitude faster (100 000× faster) than a heat pump.

ethagknight 8y ago
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.
IndrekR 8y ago
This is not really an issue. Usually you have 4-5 seconds to react for the "hot reserve". Also for the known peaks you can preventively switch off the loads (it is amazing what happens at 7:02am when everybody switches on their kettle at the same time, even worse with water supply and flushing peaks). In addition such systems sometimes measure frequency deviation and switch off/on the load when it goes out of bounds. The result is that this works really well for fast balancing as soon as you have few hundred installed spots in one grid. And there is real money in it with ROI 1..3 years for the service provider. Disclaimer: my electronics engineering company has worked with research, design and engineering of such load balancing hardware
adrianmonk 8y ago
I'm not an expert, but I'd think letting external factors control the switching on/off of your heat pump would have two downsides: (1) efficiency, and (2) wear and tear. If you're talking about a heat pump used in air conditioning, at least, longer cycle times result in better dehumidification and higher efficiency. If you interrupt the cycle, you're effectively short cycling.

radicalbyte 8y ago

My father works in the heating world. He installed a large efficient storage water heater in the house which would basically warm the water in one go at 5am and provide it to the house all day. What I don't understand from the article is why this is being controlled by the grid? The US is a market system, can't I buy a smart immersion heater which can then react to real time pricing information? So I warm my water up at times when the grid are paying people to use electricity? That places the incentives correctly: a) The entity making the investment in a new heater also gets the financial benefits thereof. b) What's to stop your electricity supplier making your water 5% hotter every year to boost their revenues?

benj111 8y ago
"What I don't understand from the article is why this is being controlled by the grid? " Hypothetically if you bought your own you would need a smart meter so you're electricity company knew exactly when you had used power, there also needs to be a system to communicate to your smart appliance, to tell it to turn on. Neither of these really exist so I suppose its sensible for the utility to take ownership to iron out kinks, feel out how in works in practise and stuff. To clarify, smart meters do exist, I don't believe they have the accuracy of metering needed for this application though.
- bdamm 8y ago
  The modern smart meters are quite accurate, much more accurate than the mechanical ones, usually to the ratepayer’s chagrin. The modern meters will pick up an induction spike from a noisy motor such as in an inefficient refrigerator or fan, where the older generation would not. How accurate does it need to be?
  - benj111 8y ago
    Its the time accuracy that matters, if its for frequency stabilisation then you need granularity in the order of seconds, rather than minutes as I believe smart meters are at the moment.

benj111 8y ago

I was trying to work out their attitude to heat pumps too. Its almost "they're too efficient, lets use something that uses more electricity" ?! I don't share your concerns with calling it a battery though, it stores energy. Combined with a peltier it could generate electricity with that energy. If it eases marketing, and gets this into peoples homes, I'm all for it.

throwawaycanada 8y ago

I did the math on this once. For residential it is not realistic due to the amount of water you would need to store. For commercial I think you would need a small lake.

ethagknight 8y ago
Correct, if you are trying to utilize it for a sole method of heat and cool. You will still need to dump excess / add additional through more conventional means, depending on local climate. To your underlying point, none of the added complexity is worth the effort unless a) the utility is paying you to take the excess load and/or b) someone really innovates on a slick, simple package.

amluto 8y ago

There are a couple downsides here. When sizing a climate control system of any sort, it’s nice to size it such that, at full output, it will be just barely sufficient for the worst case usage. If you use it for demand response and time-of-use optimization, you either need to size for a worst-case day such that it’s still powerful enough when it’s switched off at expensive times or you need to store heat or cold for multiple days. Second, while a simple-ish hydronic system is great for heat, it’s less ideal for cooling. You need to make sure that a cooling system can remove sufficient water vapor to keep a comfortable humidity or you need a separate dehumidifier. (Ideally every new building in a humid climate would have independent dehumidification anyway, so this is not a show stopper.). It’s also important to avoid condensation in bad places — if you cool your floor or ceiling much below the dew point, you have a problem.