4 ms·

Probably not. Spinning inertia and grid frequency are a core component of running a stable grid. Gives you a large store of energy that can absorb sudden spikes

Probably not. Spinning inertia and grid frequency are a core component of running a stable grid. Gives you a large store of energy that can absorb sudden spikes in demand or drops in supply, so systems have time to react before really bad things happen. The grid frequency is an incredibly useful communication tool that allows any piece of equipment to easily and accurately measure the current health the overall grid, and automatically make adjustments to help balance and improve the health the of the grid (either by increasing or decreasing load/supply). Because the frequency is set by physically large spinning turbines it means it’s also a direct and inseparable measure of total grid health, not something that’s dependent on another system to monitor and communicate grid health. It’s hard to overstate how much of our electricity grids depend on grid frequency, and one having thousands of systems monitoring and adapting to grid frequency, to remain as robust and stable as they are. In a DC world you don’t get that anymore, and keeping a grid balanced becomes substantially more complex requiring potentially unreliable side-channel communication to allow equipment on the grid to coordinate themselves. Its really hard to beat a system where one of it core fundamental attributes (frequency) needed for power transmission, is also the perfect attribute for distributed coordination of load and supply.

deleted 3y ago
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marcosdumay 3y ago
> Gives you a large store of energy that can absorb sudden spikes in demand or drops in supply, so systems have time to react before really bad things happen. Capacitors do the same for DC. They are also more efficient and reliable. The thing about a communication channel is true. But it will become true for AC after almost all of the generation becomes free of rotational inertia too (PV, modern wind, and batteries). And you need side-channel communication to decide what generator will take over what load right now.
- akira2501 3y ago
  > Capacitors do the same for DC. They are also more efficient and reliable. Yea.. but their failure mode can sometimes be a dead short. Engineering around this in a power delivery application is a severe hassle.
  - marcosdumay 3y ago
    Don't look too close at spinning wheels failure modes. The fact is that for most applications, there isn't enough technical difference to justify either of the options. It's all path dependency based on random choices made ages ago.
    - akira2501 3y ago
      > Don't look too close at spinning wheels failure modes. It's a sealed turbine, not a "spinning wheel." It's failure modes, while internally destructive, are often limited to the device itself, and trips are much easier to install and utilize in this path. Dead short DC failures have a tendency to destroy nearby equipment and start fires as well. You're also going to need a bank of capacitors, so you've multiplied your failure rate for each capacitor required. > there isn't enough technical difference to justify either of the options There's a massive amount of difference and AC is obviously justified. > based on random choices made ages ago. You don't seem to be aware of the history of the power grid and how we've arrived at the technology we have.
- avianlyric 3y ago
  Well this is what the article covers, Grid Forming Inverters, I.e. inverters that have the ability to behave like they’ve got inertia, and where the feedback loop between frequency and power output is tight enough they will naturally migrate to a stable grid frequency, rather than just bouncing around all over the place like normal Grid Following Inverts do if there isn’t enough spinning inertia in the system. So even in world where all power sources are coupled to the grid via inverters, it’s still possible to use the grid frequency as communication channel. Side channels that exist physically outside the grid will never be reliable and ubiquitous enough to replace grid frequency, for grid stability you need a feedback loop measured in nanoseconds to avoid scary oscillations in load and supply, that feedback loop needs to be faster than a microcontroller can manage, hence the reason why Grid Forming Inverters are more complex than normal Grid Following Inverters. After all the system you’re trying to monitor and keep stable naturally communicates at the speed of light, so it really isn’t possible to use digital systems to keep it stable. You need some sort of analog inertia (whether that’s spinning rotors, or clever analogue electronics doesn’t really matter) to handle the high frequency changes, and damp them enough for digital electronics to deal with the longer term drift. Also it’s not just suppliers that coordinate via frequency, it’s also loads. Anyone out there running a large semi-continuous, but interruptible loads (e.g. water pumps, large arc furnaces, heating systems, bulk EV charging etc) can usually get a discount on their energy prices, in exchange for voluntarily disconnecting their load if the grid frequency drops too far, allowing the grid to shed the least sensitive loads first, before it’s starts forcefully disconnecting more sensitive loads. > Capacitors do the same for DC. They are also more efficient and reliable. I don’t know who told you that, but capacitors aren’t even vaguely close to reliable compared to a spinning turbine. Not once you consider how many capacitors you would need to store an equivalent amount of energy as a spinning turbine. Super capacitors top out at about 4 Wh/kg, and can get up to 10 Wh/kg if you’re using hybrid capacitors (which basically a mix of a battery and capacitor). A flywheel energy storage systems are around 100Wh/kg. So at least one order of magnitude more energy per kg. So you need a lot of capacitors to replace the energy storage of a turbine. Once you’ve got that many very expensive capacitors linked up with the needed control electronics, I doubt it’s anywhere near as reliable (or cost effective) as a big spinning chunk of steel.

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marcosdumay 3y ago

> Gives you a large store of energy that can absorb sudden spikes in demand or drops in supply, so systems have time to react before really bad things happen. Capacitors do the same for DC. They are also more efficient and reliable. The thing about a communication channel is true. But it will become true for AC after almost all of the generation becomes free of rotational inertia too (PV, modern wind, and batteries). And you need side-channel communication to decide what generator will take over what load right now.

akira2501 3y ago
> Capacitors do the same for DC. They are also more efficient and reliable. Yea.. but their failure mode can sometimes be a dead short. Engineering around this in a power delivery application is a severe hassle.
- marcosdumay 3y ago
  Don't look too close at spinning wheels failure modes. The fact is that for most applications, there isn't enough technical difference to justify either of the options. It's all path dependency based on random choices made ages ago.
  - akira2501 3y ago
    > Don't look too close at spinning wheels failure modes. It's a sealed turbine, not a "spinning wheel." It's failure modes, while internally destructive, are often limited to the device itself, and trips are much easier to install and utilize in this path. Dead short DC failures have a tendency to destroy nearby equipment and start fires as well. You're also going to need a bank of capacitors, so you've multiplied your failure rate for each capacitor required. > there isn't enough technical difference to justify either of the options There's a massive amount of difference and AC is obviously justified. > based on random choices made ages ago. You don't seem to be aware of the history of the power grid and how we've arrived at the technology we have.
avianlyric 3y ago
Well this is what the article covers, Grid Forming Inverters, I.e. inverters that have the ability to behave like they’ve got inertia, and where the feedback loop between frequency and power output is tight enough they will naturally migrate to a stable grid frequency, rather than just bouncing around all over the place like normal Grid Following Inverts do if there isn’t enough spinning inertia in the system. So even in world where all power sources are coupled to the grid via inverters, it’s still possible to use the grid frequency as communication channel. Side channels that exist physically outside the grid will never be reliable and ubiquitous enough to replace grid frequency, for grid stability you need a feedback loop measured in nanoseconds to avoid scary oscillations in load and supply, that feedback loop needs to be faster than a microcontroller can manage, hence the reason why Grid Forming Inverters are more complex than normal Grid Following Inverters. After all the system you’re trying to monitor and keep stable naturally communicates at the speed of light, so it really isn’t possible to use digital systems to keep it stable. You need some sort of analog inertia (whether that’s spinning rotors, or clever analogue electronics doesn’t really matter) to handle the high frequency changes, and damp them enough for digital electronics to deal with the longer term drift. Also it’s not just suppliers that coordinate via frequency, it’s also loads. Anyone out there running a large semi-continuous, but interruptible loads (e.g. water pumps, large arc furnaces, heating systems, bulk EV charging etc) can usually get a discount on their energy prices, in exchange for voluntarily disconnecting their load if the grid frequency drops too far, allowing the grid to shed the least sensitive loads first, before it’s starts forcefully disconnecting more sensitive loads. > Capacitors do the same for DC. They are also more efficient and reliable. I don’t know who told you that, but capacitors aren’t even vaguely close to reliable compared to a spinning turbine. Not once you consider how many capacitors you would need to store an equivalent amount of energy as a spinning turbine. Super capacitors top out at about 4 Wh/kg, and can get up to 10 Wh/kg if you’re using hybrid capacitors (which basically a mix of a battery and capacitor). A flywheel energy storage systems are around 100Wh/kg. So at least one order of magnitude more energy per kg. So you need a lot of capacitors to replace the energy storage of a turbine. Once you’ve got that many very expensive capacitors linked up with the needed control electronics, I doubt it’s anywhere near as reliable (or cost effective) as a big spinning chunk of steel.