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Comment by huijzer | Hacker News Reader

An individual inverter can usually switch in about 4 ms. A Tesla Megapack can go from 0% output to max output in 100 ms. Conversely, gas turbines (the fastest type of traditional power plant) takes about a minute to go from say 40% to 60%. Even in the fastest possible design, there is a mechanical rotor (kinetic energy) that has to change speed.

What I mean to say is that solar and batteries are likely an order of magnitude faster to respond to sudden demand changes. So I would expect a more reliable system when more solar and especially batteries are being added.

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> Even in the fastest possible design, there is a mechanical rotor (kinetic energy) that has to change speed.

The point of ramping up the power plant is to make sure that the rotor doesn't change speed (by e.g. burning more fuel to push it harder, because there's suddenly more load on it), and that can happen a lot faster than spinning up the rotor from scratch. Indeed a heavy rotor helps to stabilise the grid "for free" by acting as a flywheel (which, in a way, responds even quicker to the demand change than a battery can).

> An individual inverter can usually switch in about 4 ms.

A quarter of a 60 hz cycle or a fifth of a 50 hz cycle is really fast. For comparison, it takes a current limiting fuse around a half cycle to clear a short circuit current and a GFCI takes around two cycles to clear a ground fault.

I think you’re missing the point how turbine-generator works. The rpm speed has to stay the same, meaning the rotor speed doesn’t change. As long as you don’t have closed circuit you’ll waste that mechanical energy. If you meant starting from stand still position, then you’re right it takes couple minutes to pick up the load.

With that said, turbines responding in couple minutes are more reliable as a baseline when you’re planning load flow of as big as country or wider area. The basic reason is that you have source of energy under your control such as nuclear, water, gas, coal. You cannot have solar, wind as your baseline, I don’t want sound dramatic, but it’s kind of suicidal to do that. Solar’s ramping is not a win when you consider greater scale.

Reliable until it isn’t.

The entire grid is a statistical system where we define the acceptable uptime.

Renewables are as good as any other energy source bringing its own fuel, just need to take the variability into account.

https://www.nytimes.com/2022/11/15/business/nuclear-power-fr...

You’re correct that the system is statistical, and it’s planned accordingly. However, we cannot omit the fact that it’s the running turbine that responds faster to the unpredictable nature of the grid. The backbone of the grid, aka the baseline plants, are extremely responsive to unpredictable nature of the grid at a greater scale, with enough amount of safety margins to bring into service under unusual circumstances. I really don’t see, at least what we have in hand rn, that happening with solar or wind. Without strong baseline you’d experience supply demand imbalance, in engineering terms frequency decay, voltage collapse.

Which means nuclear is the worst companion imaginable. Since nuclear power needs to run at 100% 24/7 to only make an enormous loss.

Dispatchable nuclear power to complement renewables has never made sense.

It's amazing how every comment you make is the most boring ideological propaganda

Stating facts is “ideological propaganda”?

Work with the world, not against it.

These are lies you tell yourself and how you want people to see you. In a past discussion, you concluded by saying that those who support nuclear energy also support fossil fuels.

These are your ideological premises; you don't care about creating a better world, nor are you interested in facts and problems. You only care about your vision of things and making it prevail over others.

There's no need to know anything else to make any of your comments irrelevant. It's no coincidence that you are in every nuclear discussion, asserting how much you are against it.

Given how the rightwing conservative politics have shifted from pure climate change denial to harping nuclear as the non-solution to prolong our reliance on fossil fuels the link is clear.

Nuclear power derives its energy from the binding energy of ultra-heavy atomic nuclei, not fossil fuels. This energy can then be used to power electric cars, avoiding fossil fuel consumption. Furthermore, unlike wind and solar energy, nuclear power generation is not tied to the vagaries of weather, meaning that it doesn’t require burning millions of cubic meters of natural gas every overcast, calm day. For this reason, Russia historically was the largest single benefactor of Germany’s green euphoria: it prolongs fossil fuel reliance.

So often, emotional thinking leads to conclusions that are opposed to reality. You really have to watch out for it, if you want good results.

Your comments are coming across as lacking nuance ("nuclear is the worst possible...", for example).

Nuclear has a place depending on how you weigh specific factors in your grid design. It's zero carbon. It's hideously expensive, particularly in capex. It's generally quite reliable and its availability is mostly uncorrelated with that of solar and wind. it's modestly dispatchable - you can scale down to 60% or so in many designs. (A little lower but let's be conservative).

If you place high weight on zero carbon, nuclear is an (expensive) way to get through the night. It can work pretty well in a grid mix if your grid is large enough that the loss of one nuclear plant isn't a really big chunk of your power supply (since, obviously, you want enough redundancy to handle a certain fraction of generation failures at peak load).

Are solar+wind+batteries on a much better trajectory? Yes. But batteries are not there _yet_ for 24x7, though I think we all hope they will be in the reasonably near future.

He does not care about these arguments, what matters is that there is no room for nuclear power.

In a past discussion I talked to him about how one of the important things to do was to diversify, as China has a lot of influence on the whole renewable sector (solar, batteries, etc.)

Needless to say, that's not a problem for him. For him to hope that batteries are the future is already a sure thing, without the slightest doubt.

Hideously expensive and any plant announced today will not be online in time to have any material effect on our fight against climate change.

Which means funding diverted from renewables to nuclear will prolong our fight against climate change.

> Hideously expensive and any plant announced today will not be online in time to have any material effect on our fight against climate change

False, we have 26 years to decarbonize, all the time it takes to build any number of nuclear power plants in any country in the world.

> Which means funding diverted from renewables to nuclear will prolong our fight against climate change.

We can say the same thing about renewables. Then come and tell me you are not ideological... Where is the mathematical certainty that batteries at scale will be available everywhere and for everyone by 2050? If you come from the future, prove it to me and I will agree with you.

About 20 years from being announced. Compare with renewables taking 1-5 years depending on if it is solar or offshore wind.

Say 5 years for renewables.

This means that investing in nuclear will have 15 years of cumulative emissions before anything is curbed.

Meaning, even if the renewable options ends up solving only 80% of the problem it will take until somewhere 2080-90 for the “perfect” nuclear solution to have less cumulative emissions.

Even if renewables are completely unable to solve the entire problem we can invest in them and then in 2060 and still be ahead of nuclear power, and then choose it as the final solution.

Today it is simply lunacy proposed by the fossil fuel industry or people looking for the perfect solution rather than piecemeal solving the issue.

IANAEE (not an electrical engineer), but doesn't a gas turbine spin at a constant speed to drive a 60Hz generator, regardless of whether it's running at 20%, 60%, or 100% of capacity?

When there’s a load imbalance on the grid (more load than capacity), the turbines physically slow down as inertial energy is extracted from them. This causes the grid frequency to drop. It takes some time to ramp up production and speed up the turbine etc.

The maximum slow-down of the turbines (before the generator trips off-line, removing the load on it) is far less than you seem to assume. The article's graph shows the 60.00Hz grid frequency dropping...all the way to 59.92Hz. That's 0.1333%.

For an on-line gas turbine, the time to ramp up production is the second or few needed for the automated controls to open the throttle on the "Gas IN" pipe. It's basically a natural gas-burning turboprop jet engine, with the propeller replaced by a generator. (Yes, this can be less efficient in a combined cycle plant.)

The more interesting thing about rotating power plants is that they are routinely destroyed by transmission outages, because when a rotating generator is suddenly disconnected from its load, there are infinity terms in the equations that govern its motion and infinity isn't a thing you can resist. For steam turbines the control system has to slam the valve shut on the steam, otherwise the machine would overspeed, and closing that valve destroys some sacrificial part of the steam plumbing (hopefully). Steam power plants have to be inspected and repaired after disconnects and this is one of the numerous reasons why fission kinda sucks on the reliability front.

I don't see why there can't be load resistors (like locomotives use) to gracefully handle these sorts of situations.

Well if you can solve it, I imagine there's a lot of money to be made - and yet it hasn't been solved.

An SD40 locomotive can dissipate about 500kW that way, so you would need the equivalent of 2000 locomotives worth of resistors and fans to sink the 1 or 2GW or more that a fission power station produces.

If you wanted to do so continuously. If you're just handling an impulse you don't need so much, but it's gotta absorb a lot of energy quickly.

While the infinity terms may be a useful way to think about how the system loses stability, I think it's better to think of it in terms of energy: at any given time there's some amount of energy that's been injected into the system in the form of hot gas which hasn't been converted yet. Even a few seconds worth is a lot of energy, and if the electrical load is removed, that energy has to go somewhere.

This is true only if the protection does not operate as designed. They are NOT routinely destroyed by transmission outages. You have been misinformed. Rotating machines cannot overspeed instantly, as they have inertia.

Dozens of power plants blew up steam rupture disks during the 2003 northeast outage. EPA, FERC, and NYISO all mention this in their reports.

How many Tesla Megapacks are needed to replace a nuclear plant temporary outage? And for for long can they provide that power?

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