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0 pointstuetuopay5d ago0 comments

In this very specific case, battery storage would not have helped (in fact, it would have worsened the problem). One of the issues in the failure is renewables, but not because of intermittence. It's because of their ~infinite ramp and them being DC.

Anything that's not a spinning slug of steel produces AC through an inverter: electronics that take some DC, pass it through MOSFETs and coils, and spits out a mathematically pure sine wave on the output. They are perfectly controllable, and have no inertia: tell them tout output a set power and they happily will.

However, this has a few specific issues:

- infinite ramps produce sudden influx of energy or sudden drops in energy, which can trigger oscillations and trip safety of other plants

- the sine wave being electronically generated, physics won't help you to keep it in phase with the network, and more crucially, keep it lagging/ahead of the network

The last point is the most important one, and one that is actually discussed in the report. AC works well because physics is on our side, so spinning slugs or steel will self-correct depending on the power requirements of the grid, and this includes their phase compared to the grid. How out-of-phase you are is what's commonly called the power factor. Spinning slugs have a natural power factor, but inverter don't: you can make any power factor you want.

Here in the spanish blackout, there was an excess of reactive power (that is, a phase shift happening). Spinning slugs will fight this shift of phase to realign with the correct phase. An inverter will happily follow the sine wave measured and contribute to the excess of reactive power. The report outlines this: there was no "market incentive" for inverters to actively correct the grid's power factor (trad: there are no fines).

So really, more storage would not have helped. They would have tripped just like the other generators, and being inverter-based, they would have contributed to the issue. Not because "muh renewable" or "muh battery", but because of an inherent characteristic of how they're connected to the grid.

Can this be fixed? Of course. We've had the technology for years for inverters to better mimic spinning slugs of steel. Will it be? Of course. Spain's TSO will make it a requirement to fix this and energy producers will comply.

A few closing notes:

- this is not an anti-renewables writeup, but an explanation of the tech, and the fact that renewables are part of the issue is a coincidence on the underlying technical details

- inverters are not the reason the grid failed. but they're a part of why it had a runaway behavior

- yes, wind also runs on inverters despite being spinning things. with the wind being so variable, it's much more efficient to have all turbines be not synchronized, convert their AC to DC, aggregate the DC, and convert back to AC when injecting into the grid

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toomuchtodo5d ago

I agree with your detailed assessment, but importantly, I argue more battery storage would've allowed for the grid to fail gracefully through rapid fault isolation and recovery (assuming intelligent orchestration of transmission level fault isolation). Parallels to black start capabilities provided by battery storage in Texas (provided by Tesla's Gambit Energy subsidiary). When faults are detected, the faster you can isolate and contain the fault, the faster you can recover before it spreads through the grid system.

The storage gives you operational and resiliency strength you cannot obtain with generators alone, because of how nimble storage is (advanced power controls), both for energy and grid services.

> Can this be fixed? Of course. We've had the technology for years for inverters to better mimic spinning slugs of steel. Will it be? Of course. Spain's TSO will make it a requirement to fix this and energy producers will comply.

This is synthetic inertia, and is a software capability on the latest battery storage systems. "There was no market mechanism to encourage the deployment of this technology in concert with Spain’s rapid deployment of solar and wind." from my top comment. This should be a hard requirement for all future battery storage systems imho.

Potential analysis of current battery storage systems for providing fast grid services like synthetic inertia – Case study on a 6 MW system - https://www.sciencedirect.com/science/article/abs/pii/S23521... | https://doi.org/10.1016/j.est.2022.106190 - Journal of Energy Storage Volume 57, January 2023, 106190

> Large-scale battery energy storage systems (BESS) already play a major role in ancillary service markets worldwide. Batteries are especially suitable for fast response times and thus focus on applications with relatively short reaction times. While existing markets mostly require reaction times of a couple of seconds, this will most likely change in the future. During the energy transition, many conventional power plants will fade out of the energy system. Thereby, the amount of rotating masses connected to the power grid will decrease, which means removing a component with quasi-instantaneous power supply to balance out frequency deviations the millisecond they occur. In general, batteries are capable of providing power just as fast but the real-world overall system response time of current BESS for future grid services has only little been studied so far. Thus, the response time of individual components such as the inverter and the interaction of the inverter and control components in the context of a BESS are not yet known. We address this issue by measurements of a 6 MW BESS's inverters for mode changes, inverter power gradients and measurements of the runtime of signals of the control system. The measurements have shown that in the analyzed BESS response times of 175 ms to 325 ms without the measurement feedback loop and 450 ms to 715 ms for the round trip with feedback measurements are possible with hardware that is about five years old. The results prove that even this older components can exceed the requirements from current standards. For even faster future grid services like synthetic inertia, hardware upgrades at the measurement device and the inverters may be necessary.

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