3 ms·

this article is about using very high mass alternators to stabilize the grid's frequency

Retric 3y ago
The clearest term IMO is synchronous capacitors. They are in effect large flywheels that can operate as both an electric motor and a generator. Over time they are a net power drain for the grid, but as parent says offer synthetic grid stability independent of power sources.
- repelsteeltje 3y ago
  Very interesting. I'm wondering whether distance and "direction" are an issue here? That is: over large distances (how) would (light speed) latency translate into phase change if "downstream stabilization" suddenly becomes "upstream". (Sorry for asking such a poorly stated question that I really haven't thought through — I know very little about electricity and you seem to understand quite a lot about this subject.) Someone have a link to 101 power transmission? I find this fascinating.
  - jnsaff2 3y ago
    Good instinct. There is a site that measures frequency in several places in Europe and shows the phase difference. [0] The phase difference is not really about distance it's more about energy flows, where it's lagging there more power is used and where it is leading more power is generated. The flow will be from early phase to later. [0] https://gridradar.net/charts/map/map.html https://gridradar.net/charts/map/map.html
    - repelsteeltje 3y ago
      So I imagine phase difference can be a serious issue, or at least something that needs to be mitigated and monitored continuously (evidently). I'm assuming a DC power network intrinsically solves this (in case of solar energy). But how would current and voltage be stabilized in that case? Just huge capacitors? Chemical batteries?
      - jnsaff2 3y ago
        Frequency and phase difference are indicators of grid balance. Grid itself can't store energy, the generation and consumption needs to be in balance. If transmission balance goes out of whack more electrons want to flow to specific places and will always try to take the path of least resistance. Those paths (as in transmission lines) have their current capacity measured in Amps and when it gets too much their protective equipment in the for of active or passive circuit breakers will take them offline (trip) therefore moving the current down next best paths and further increasing the likelihood of trips. Voltage is regulated by changing the windings of transformers in AC-AC systems or by transistors/thyristors in DC coupled networks. Frequency has usually been regulated by spinning mass, a steam powered generator has a pretty large inertia and when it slows down there is a governor or other control mechanism to add energy to the generator via opening steam valves and maybe adding fuel. If speed goes too high it is also reduced. For large load changes there are further compensatory mechanisms. Like heavy industrial plants measure grid frequency and when it falls below lets say 49.9Hz then they will immediately trip themselves offline and shed a huge amount of load from the grid. They get paid for this.
        repelsteeltje 3y ago
        > Grid itself can't store energy, the generation and consumption needs to be in balance. So while there may be huge variance in on both sides (a sunny day, a wind gust versus switching on the AC a train leaving the station) the only way to adjust is open a valve add steam, fuel? Will that scale to when, say, 80% of electricity sources are weather dependent? Or is that the pumped hydro / big batteries / future technology stuff? [Sorry for going off topic, here]
        jnsaff2 3y ago
        Grids have many-many consumers and many generators. So switching on a single AC does not have a noticeable effect. There are however correlated events like the famous East Enders peak in the UK (daily TV show at the end of which a large number of britons go and make tea with their 2kW electric kettles). But weather can span large areas and the solutions can be roughly categorized as: - some form of energy storage: batteries, hydro (can be pumped), flywheels, etc - dispatchable power - gas fired turbines, coal or wood fired thermal plants, nuclear, etc - demand side response - time of use pricing (like nordpool spot market prices) or getting paid to switch off your AC during peak hours, etc. Traditionally we have had a grid management mindset of "generation adapts to load", everyone uses as much and when they need and grid/generation adapts to it. With only renewables the mental model of "load follows generation" could make sense, people (or rather peoples devices) get a signal when it is most beneficial to consume and when not to. I think the reality will be some combination of all of the above. Mostly renewables but also diverse set of renewables that are somewhat anti-correlated, like wind+solar plus distributed. The shortfalls could be filled with natural gas fired power plants. Some nuclear when/if built/available combined with smart cars and devices. V2G will get there eventually as well and then the car battery will have much more energy available than a typical home uses in a day.
    - jacquesm 3y ago
      Within reason. If you lead or lag too much it will cause trouble (either for you or for other consumers and in a really bad case for the grid equipment itself). That's why the grid will selectively island parts that are too far out of phase. Normally this should not happen though.
- sidewndr46 3y ago
  Why would anyone use the term 'capacitor' to describe what is basically an alternator, a flywheel & an electric motor?
  - callalex 3y ago
    It’s short term energy storage with rapid charge and discharge capabilities. Not all capacitors are electrolytic.
- connicpu 3y ago
  If we're going to use circuit terminology I think the physics of a flywheel are more like some kind of AC Inductor. DC Inductors resist changes in the flow of current, keeping current flowing even when circuit conditions change. It also helps that the parts of an inductor and flywheel that are in contact with the circuit/grid are coils of wire wrapped around an iron/magnetic core.
- jacquesm 3y ago
  Transformers also have some of that effect.
sheepshear 3y ago
I think the article should not have described a condenser as a generator. It's causing confusion.
ViewTrick1002 3y ago
Yep. There are also Shunt Reactors for managing voltage stability. https://en.wikipedia.org/wiki/Variable_shunt_reactor https://en.wikipedia.org/wiki/Variable_shunt_reactor
deleted 3y ago
[deleted]

The clearest term IMO is synchronous capacitors. They are in effect large flywheels that can operate as both an electric motor and a generator. Over time they are a net power drain for the grid, but as parent says offer synthetic grid stability independent of power sources.

repelsteeltje 3y ago
Very interesting. I'm wondering whether distance and "direction" are an issue here? That is: over large distances (how) would (light speed) latency translate into phase change if "downstream stabilization" suddenly becomes "upstream". (Sorry for asking such a poorly stated question that I really haven't thought through — I know very little about electricity and you seem to understand quite a lot about this subject.) Someone have a link to 101 power transmission? I find this fascinating.
- jnsaff2 3y ago
  Good instinct. There is a site that measures frequency in several places in Europe and shows the phase difference. [0] The phase difference is not really about distance it's more about energy flows, where it's lagging there more power is used and where it is leading more power is generated. The flow will be from early phase to later. [0] https://gridradar.net/charts/map/map.html https://gridradar.net/charts/map/map.html
  - repelsteeltje 3y ago
    So I imagine phase difference can be a serious issue, or at least something that needs to be mitigated and monitored continuously (evidently). I'm assuming a DC power network intrinsically solves this (in case of solar energy). But how would current and voltage be stabilized in that case? Just huge capacitors? Chemical batteries?
    - jnsaff2 3y ago
      Frequency and phase difference are indicators of grid balance. Grid itself can't store energy, the generation and consumption needs to be in balance. If transmission balance goes out of whack more electrons want to flow to specific places and will always try to take the path of least resistance. Those paths (as in transmission lines) have their current capacity measured in Amps and when it gets too much their protective equipment in the for of active or passive circuit breakers will take them offline (trip) therefore moving the current down next best paths and further increasing the likelihood of trips. Voltage is regulated by changing the windings of transformers in AC-AC systems or by transistors/thyristors in DC coupled networks. Frequency has usually been regulated by spinning mass, a steam powered generator has a pretty large inertia and when it slows down there is a governor or other control mechanism to add energy to the generator via opening steam valves and maybe adding fuel. If speed goes too high it is also reduced. For large load changes there are further compensatory mechanisms. Like heavy industrial plants measure grid frequency and when it falls below lets say 49.9Hz then they will immediately trip themselves offline and shed a huge amount of load from the grid. They get paid for this.
      - repelsteeltje 3y ago
        > Grid itself can't store energy, the generation and consumption needs to be in balance. So while there may be huge variance in on both sides (a sunny day, a wind gust versus switching on the AC a train leaving the station) the only way to adjust is open a valve add steam, fuel? Will that scale to when, say, 80% of electricity sources are weather dependent? Or is that the pumped hydro / big batteries / future technology stuff? [Sorry for going off topic, here]
        jnsaff2 3y ago
        Grids have many-many consumers and many generators. So switching on a single AC does not have a noticeable effect. There are however correlated events like the famous East Enders peak in the UK (daily TV show at the end of which a large number of britons go and make tea with their 2kW electric kettles). But weather can span large areas and the solutions can be roughly categorized as: - some form of energy storage: batteries, hydro (can be pumped), flywheels, etc - dispatchable power - gas fired turbines, coal or wood fired thermal plants, nuclear, etc - demand side response - time of use pricing (like nordpool spot market prices) or getting paid to switch off your AC during peak hours, etc. Traditionally we have had a grid management mindset of "generation adapts to load", everyone uses as much and when they need and grid/generation adapts to it. With only renewables the mental model of "load follows generation" could make sense, people (or rather peoples devices) get a signal when it is most beneficial to consume and when not to. I think the reality will be some combination of all of the above. Mostly renewables but also diverse set of renewables that are somewhat anti-correlated, like wind+solar plus distributed. The shortfalls could be filled with natural gas fired power plants. Some nuclear when/if built/available combined with smart cars and devices. V2G will get there eventually as well and then the car battery will have much more energy available than a typical home uses in a day.
  - jacquesm 3y ago
    Within reason. If you lead or lag too much it will cause trouble (either for you or for other consumers and in a really bad case for the grid equipment itself). That's why the grid will selectively island parts that are too far out of phase. Normally this should not happen though.
sidewndr46 3y ago
Why would anyone use the term 'capacitor' to describe what is basically an alternator, a flywheel & an electric motor?
- callalex 3y ago
  It’s short term energy storage with rapid charge and discharge capabilities. Not all capacitors are electrolytic.
connicpu 3y ago
If we're going to use circuit terminology I think the physics of a flywheel are more like some kind of AC Inductor. DC Inductors resist changes in the flow of current, keeping current flowing even when circuit conditions change. It also helps that the parts of an inductor and flywheel that are in contact with the circuit/grid are coils of wire wrapped around an iron/magnetic core.
jacquesm 3y ago
Transformers also have some of that effect.

sheepshear 3y ago

I think the article should not have described a condenser as a generator. It's causing confusion.

ViewTrick1002 3y ago

Yep. There are also Shunt Reactors for managing voltage stability. https://en.wikipedia.org/wiki/Variable_shunt_reactor https://en.wikipedia.org/wiki/Variable_shunt_reactor

deleted 3y ago

[deleted]