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To free the Baltic grid, old technology is new again

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Re: To free the Baltic grid, old technology is new again

#31

Post by chx »

As an aside, one of the most stunning proofs of how successful the European Union is happened with the grid. On 8 January 2021, the synchronous area of Continental Europe split into two, the system separation resulted in a deficit of power (approx. -6.3 GW) in the North-West Area and a surplus of power (approx. +6.3 GW) in the South-East Area,

The reaction speed was something to behold. The event happened at 14:05 CET, at 14:09 CET the Transmission System Operators (TSOs) were in teleconference but by then some 1.7GW capacity in France and Italy was dropped and 420 MW and 60 MW was activated in the Nordic and Great Britain. Customers barely felt it: only 70 MW in the North-West Area and 163 MW in the South-East Area were disconnected. By 15:08 the event concluded.

Yes, there was a mistake in the processes which led to the event in special circumstances but , I believe , the respected readers of HN know this all too well , the big question is what happens when an emergency hits. And those processes held up spectacularly.

Re: To free the Baltic grid, old technology is new again

#32

Post by jnsaff2 »

repelsteeltje wrote: post #30
jnsaff2 wrote: post #25

Earlier quoted context omitted.

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

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?

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.

Re: To free the Baltic grid, old technology is new again

#33

Post by jnsaff2 »

chx wrote: post #31

As an aside, one of the most stunning proofs of how successful the European Union is happened with the grid. On 8 January 2021, the synchronous area of Continental Europe split into two, the system separation resulted in a deficit of power (approx. -6.3 GW) in the North-West Area and a surplus of power (approx. +6.3 GW) in the South-East Area, The reaction speed was something to behold. The event happened at 14:05 CE…

https://www.netzfrequenz.info/allgemein/aufteilung-des-synch...

Re: To free the Baltic grid, old technology is new again

#34

Post by jillesvangurp »

formerly_proven wrote: post #3

> All nine of the Baltics’ synchronous condensers will have power-boosting flywheels, as she explains, equipping each installation with up to 2,200 megajoules of energy. Though 97% of that energy isn’t available to the grid as the name synchronous condenser implies.

It's not that much energy anyway. 1kwh is about 3.6 megajoule. 2200 times 9 divided by 3.6 is about 5.5mwh. This is obviously not intended as a battery but more as a very low latency control mechanism to control frequencies and voltages. You'd only be able to use it for very short bursts of energy probably in the order of a few seconds or minutes.

You'd use something like this while bringing online alternative sources of energy, which takes time. Of course a grid battery probably wouldn't need this as it would be similarly quick to come online. Which raises the question why they are going for synchronous condensers instead of grid battery. One doesn't exclude the other of course.

Re: To free the Baltic grid, old technology is new again

#35

Post by repelsteeltje »

jnsaff2 wrote: post #32
repelsteeltje wrote: post #30

Earlier quoted context omitted.

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?

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 protect…

> 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]

Re: To free the Baltic grid, old technology is new again

#36

Post by sidewndr46 »

Retric wrote: post #9
sidewndr46 wrote: post #7

Earlier quoted context omitted.

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

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.

Why would anyone use the term 'capacitor' to describe what is basically an alternator, a flywheel & an electric motor?

Re: To free the Baltic grid, old technology is new again

#37

Post by vGPU »

ViewTrick1002 wrote: post #2

This is why the common trope of "The grid can't function without the inertia from big heavy generators!!" detracting the rise of renewables is invalid. Synthetic grid strength has been available for a century. Today the research focuses on "Grid forming inverters". Taking the same principle as powering a home in island mode and stretching it to the entire grid allowing non-synchronous generators to provide the system…

Yes, the mechanism which can provide power for some 45 seconds is a generator replacement.

Sigh…

Re: To free the Baltic grid, old technology is new again

#38

Post by sheepshear »

sidewndr46 wrote: post #7
ViewTrick1002 wrote: post #2

This is why the common trope of "The grid can't function without the inertia from big heavy generators!!" detracting the rise of renewables is invalid. Synthetic grid strength has been available for a century. Today the research focuses on "Grid forming inverters". Taking the same principle as powering a home in island mode and stretching it to the entire grid allowing non-synchronous generators to provide the system…

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

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

Re: To free the Baltic grid, old technology is new again

#40

Post by jnsaff2 »

repelsteeltje wrote: post #35
jnsaff2 wrote: post #32

Earlier quoted context omitted.

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 protect…

> 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 technol…

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.

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