3 ms·

A simple practical example: my dishwasher start heating water is +2kW in an instance, my solar inverter take 2-3" to ramp up to +2kW. The home microgrid need or

A simple practical example: my dishwasher start heating water is +2kW in an instance, my solar inverter take 2-3" to ramp up to +2kW. The home microgrid need or the national grid or a battery inverter to avoid collapsing due to a too big frequency drop. The dishwasher have finished heating water, again a sudden -2kW, again I need to divert extra energy to the grid or a battery to avoid a frequency peak big enough to make the inverter disconnect. That doesn't really answer my question. If I have a home solar installation that can send up to 10KW into the grid, how is that any different than an EV battery that can send the same amount of power into the grid? I could see the problem if people were sending 100's of KW into the grid with EV batteries, but that's not the case, they're sending a similar amount of power that a home would use. 3kW slow charge is simply too low for most vehicles, they recharge but the battery might suffer I charge my EV at 1KW (9 amps at 120V), it's enough to recharge my 30 mile commute overnight. I'm not aware of any cars (in the USA) that have a minimum charge rate.

kkfx 4y ago
> If I have a home solar installation that can send up to 10KW into the grid, how is that any different than an EV battery that can send the same amount of power into the grid? Your system have a purpose: give you energy NOT stabilizing the grid. Your system (like mine) actually disturb the grid and that's why countries have regulations on them. The actual grid have issues ALSO due to the augmented presence of p.v. If you want to stabilize the grid with cars you do the very opposite, your system need not to give you energy using the grid as a kind of "energy buffer" but to be itself an energy buffer. Let's say we have such systems: at a certain point in time locally our domestic power plants see a sudden frequency drop, around 1Hz. As fast as they can they start pushing energy to the grid. All connected vehicles/plants. As a result the frequency peak in 2-3". Again as fast as they can all connected systems try to get energy from the grid to help the frequency going down. Again a network effect. The frequency drop. They reverse. In a minute you have generated enough oscillation that no one is able to keep the frequency, local grid segments got disconnected, all generators in the segment shut down. Few big enough power plants can coordinate themselves to monitor and decide, too many small and spread can't. Even with frequency shifting witch is the fastest and simplest way possible we can't. Trying proving the above: if you have a monitoring system fast enough, like an MQTT frequency sensors or a multimeter with frequency measure and graphing ability try to see a minute at night, with pv disconnected, no battery etc and a minute when it work. On grid ONLY you'll see a far more stable frequency. On p.v./battery you'll see a schizophrenic variation. Try to interpolate at a grid scale the resulting mess. If we just inject to the grid our inverters simply try to push energy watching frequency, they push less as the frequency goes up but nothing more. It's up to the big power plant regulating. Being one-direction only they generate disturbances but still something manageable at least at a certain scale. A bi-direction system I can't really say if it's sustainable nor I know if a far bigger presence of p.v. can be allowed... Edit: sorry, forgot a part, yes you can recharge and EV even at 100W but the battery do not balance cells, as a result it last less time. Witch means for instance 8 years instead of 10 of usable life. 7kW is generally the "needed mean" to balance for most EVs, normally you have such issue mentioned in the manual.
- Johnny555 4y ago
  Edit: sorry, forgot a part, yes you can recharge and EV even at 100W but the battery do not balance cells, as a result it last less time. Witch means for instance 8 years instead of 10 of usable life. 7kW is generally the "needed mean" to balance for most EVs, normally you have such issue mentioned in the manual. Can you show me an example, I looked at the owners manual for a few cars and none mentioned an issue with slow Level1 charging. Few big enough power plants can coordinate themselves to monitor and decide, too many small and spread can't. Even with frequency shifting witch is the fastest and simplest way possible we can't. My utility can already turn off my air conditioner during peak demand, why is it harder to turn off a 4000W load when they need more power than to turn on a 4000W battery when they need more power?
  - kkfx 4y ago
    I have no example at hand, but if you look at "lithium battery cell balancing" you find many sources, two at random A very generic article https://www.saftbatteries.com/energizing-iot/lithium-ion-batteries-use-5-more-tips-longer-lifespan https://www.saftbatteries.com/energizing-iot/lithium-ion-bat... A thesis who cite many balancing technique https://tel.archives-ouvertes.fr/tel-03584252/document https://tel.archives-ouvertes.fr/tel-03584252/document Another normal advise is not to charge at 100%, not because it's bad in general, the contrary it's NEEDED for a proper cell balance, but on cars have a potential issue, the very same who is an issue for the grid stabilization: when you ask for more power your battery and inverters do their best to give it, but when the demand drop, for instance because you have hit the accelerator then release it, there is an excess of power and on a battery-only system like a car you have no grid to push excess energy to nor you can shut down. As a result you divert excess back to the battery crating high DC ripple effects overheating and stressing the battery itself. > My utility can already turn off my air conditioner during peak demand, why is it harder to turn off a 4000W load when they need more power than to turn on a 4000W battery when they need more power? It's not an on-and-off problem but a how quick such on-and-off can happen. As I suggest try seeing your p.v. system when it works. Try see how the frequency spike constantly with p.v. inverter active and how stable is (normally) on the grid, try to se what happen when you start a big load and when it drop. To see that better, if you have lithium storage try to run exclusively on it+solar and see what happen. AC is veeeery nice for many aspects, but it's hard for others. Try to keep a grid at a certain frequency is NOT an easy business, trying to do so with a gazillion of small generators is next to impossible. Smartness is a modern hope we add in both regulatory capacity for generators and avoid sudden loads spikes because smarter loads can potentially advise generators before starting or stopping and eventually ramp up or down slowly. However so far we are in an uncharted territory with just very little experiments and nothing on scale.

kkfx 4y ago

> If I have a home solar installation that can send up to 10KW into the grid, how is that any different than an EV battery that can send the same amount of power into the grid? Your system have a purpose: give you energy NOT stabilizing the grid. Your system (like mine) actually disturb the grid and that's why countries have regulations on them. The actual grid have issues ALSO due to the augmented presence of p.v. If you want to stabilize the grid with cars you do the very opposite, your system need not to give you energy using the grid as a kind of "energy buffer" but to be itself an energy buffer. Let's say we have such systems: at a certain point in time locally our domestic power plants see a sudden frequency drop, around 1Hz. As fast as they can they start pushing energy to the grid. All connected vehicles/plants. As a result the frequency peak in 2-3". Again as fast as they can all connected systems try to get energy from the grid to help the frequency going down. Again a network effect. The frequency drop. They reverse. In a minute you have generated enough oscillation that no one is able to keep the frequency, local grid segments got disconnected, all generators in the segment shut down. Few big enough power plants can coordinate themselves to monitor and decide, too many small and spread can't. Even with frequency shifting witch is the fastest and simplest way possible we can't. Trying proving the above: if you have a monitoring system fast enough, like an MQTT frequency sensors or a multimeter with frequency measure and graphing ability try to see a minute at night, with pv disconnected, no battery etc and a minute when it work. On grid ONLY you'll see a far more stable frequency. On p.v./battery you'll see a schizophrenic variation. Try to interpolate at a grid scale the resulting mess. If we just inject to the grid our inverters simply try to push energy watching frequency, they push less as the frequency goes up but nothing more. It's up to the big power plant regulating. Being one-direction only they generate disturbances but still something manageable at least at a certain scale. A bi-direction system I can't really say if it's sustainable nor I know if a far bigger presence of p.v. can be allowed... Edit: sorry, forgot a part, yes you can recharge and EV even at 100W but the battery do not balance cells, as a result it last less time. Witch means for instance 8 years instead of 10 of usable life. 7kW is generally the "needed mean" to balance for most EVs, normally you have such issue mentioned in the manual.

Johnny555 4y ago
Edit: sorry, forgot a part, yes you can recharge and EV even at 100W but the battery do not balance cells, as a result it last less time. Witch means for instance 8 years instead of 10 of usable life. 7kW is generally the "needed mean" to balance for most EVs, normally you have such issue mentioned in the manual. Can you show me an example, I looked at the owners manual for a few cars and none mentioned an issue with slow Level1 charging. Few big enough power plants can coordinate themselves to monitor and decide, too many small and spread can't. Even with frequency shifting witch is the fastest and simplest way possible we can't. My utility can already turn off my air conditioner during peak demand, why is it harder to turn off a 4000W load when they need more power than to turn on a 4000W battery when they need more power?
- kkfx 4y ago
  I have no example at hand, but if you look at "lithium battery cell balancing" you find many sources, two at random A very generic article https://www.saftbatteries.com/energizing-iot/lithium-ion-batteries-use-5-more-tips-longer-lifespan https://www.saftbatteries.com/energizing-iot/lithium-ion-bat... A thesis who cite many balancing technique https://tel.archives-ouvertes.fr/tel-03584252/document https://tel.archives-ouvertes.fr/tel-03584252/document Another normal advise is not to charge at 100%, not because it's bad in general, the contrary it's NEEDED for a proper cell balance, but on cars have a potential issue, the very same who is an issue for the grid stabilization: when you ask for more power your battery and inverters do their best to give it, but when the demand drop, for instance because you have hit the accelerator then release it, there is an excess of power and on a battery-only system like a car you have no grid to push excess energy to nor you can shut down. As a result you divert excess back to the battery crating high DC ripple effects overheating and stressing the battery itself. > My utility can already turn off my air conditioner during peak demand, why is it harder to turn off a 4000W load when they need more power than to turn on a 4000W battery when they need more power? It's not an on-and-off problem but a how quick such on-and-off can happen. As I suggest try seeing your p.v. system when it works. Try see how the frequency spike constantly with p.v. inverter active and how stable is (normally) on the grid, try to se what happen when you start a big load and when it drop. To see that better, if you have lithium storage try to run exclusively on it+solar and see what happen. AC is veeeery nice for many aspects, but it's hard for others. Try to keep a grid at a certain frequency is NOT an easy business, trying to do so with a gazillion of small generators is next to impossible. Smartness is a modern hope we add in both regulatory capacity for generators and avoid sudden loads spikes because smarter loads can potentially advise generators before starting or stopping and eventually ramp up or down slowly. However so far we are in an uncharted territory with just very little experiments and nothing on scale.