Hacker News Reader

Comment by samatman | Hacker News Reader

Renewables make grid reliability worse, especially wind, because the grid has to maintain a frequency, which is ultimately done with the inertia of huge rotating chunks of iron.

That's fine, as long as there are huge rotating chunks of iron. Nuclear can rotate the chunks, as can hydro and geothermal. Everything else emits carbon.

Europe is pretty tapped on hydro and geothermal, that leaves nuclear, or some very handwavey ideas of building a bunch of flywheels using resources which could be contributing to primary generation.

View on HN

Your info is out of date:

Inverters are solving grid issues at fraction of cost of spinning machines

https://reneweconomy.com.au/inverters-are-solving-grid-issue...

> Ian Christmas, head of engineering at Edify Enegy, told a Clean Energy Council large scale solar forum last week that the inverter tuning at four key solar farms – Whitsunday, Daydream, Hayman, and Hamilton – would address recently declared system strength issues in that part of the grid at one twenty-fifth of the cost of installing a synchronous condenser.

> He also said it could be done in a fraction of the time – around four months compared to fourteen months or longer for the alternative. “It’s significant enough (in terms of price and time) that it is a no brainer,” Christmas said.

Also note, synchronous condensers which you seem to believe are vaporware are a fine solution, just not as cheap.

Give everyone equal subsidizes under contract to deliver a set amount of energy on demand, with massive fines for contract breach. The market will then determine which ideas are economical viable, and which ideas aren't.

This is what my government (Sweden) is actually doing, with one difference. Rather than a liability contract, if the investment fail the government will simply repay the investors regardless if it managed to deliver energy. The government intention is that regardless if energy projects succeed or not, the energy sector shall have any money they say they need as long they continue to invest and build more capacity. That is how desperate the situation is.

This particluar tangent isn't about delivering energy. Most people seem to have accepted renewables have already won that price competition.

But there's various grid services which aren't just about delivering energy. There's a weird assumption that steam generator tech is automatically better at these things than modern inverter-based technology, but I'm not aware of any case where that is actually true.

> Most people seem to have accepted renewables have already won that price competition.

The big question that the crisis seems to highlight is if price competition is relevant. What people want is energy on demand when people want it, and the supplier want to demand as much money as the market can take. What energy cost to produce doesn't influence either of those two unless there is an overcapacity with multiple producers competing for the chance of selling.

When customers pay 10-100 times the production cost, and are happy to do so over the alternative of not having heating or open factories, then the issue that energy politics is trying to solve is not about finding the optimal technology that in theory is cheapest or best. Any technology that can solve either short term or long term is desired technology as long they actually get implemented.

> Most people seem to have accepted renewables have already won that price competition.

is that why they still get outrageous subsidies to be any kind of desirable to build?

Which specific subsidies and country are you talking about?

Offshore wind (which is more expensive than onshore or solar PV) is now built subsidy free:

https://www.offshorewind.biz/2022/08/02/subsidy-free-offshor...

UK offshore is currently paying a negative subsidy, a little bit earlier than this was predicted to happen:

https://renews.biz/62009/uk-offshore-wind-to-cross-negative-...

Short-term energy storage like the inertia on the grid is the tiniest problem with grid stability at 100% renewables. The energy in the spinning hunks of iron is tiny compared to even a small grid-scale battery, and the inverters on those batteries can provide a far better response to changes in grid frequency than the synchronous generators ever could. It's basically the one thing which is 100% not a concern with a renewable grid.

For what it's worth: France has 56 nuclear out of wich 28 were down on august 15th. https://www.rts.ch/info/monde/13306968-la-moitie-des-reacteu...

For what it's worth:

it took a worldwide pandemic slowing down the rate of schedules maintenance along with a rare, unexpected potential failure along with the consequences of 30 years of not investing in training new people in the nuclear sector for it to happen, and France is still doing just as well/bad as neighbouring countries (actually, Germany with their full renewabls push is doing much worse). It's relatively safe to say that it's not exactly a common thing.

And to add to that the country saving Germany and France from this mess is Sweden with its nuclear + hydro + wind (mostly nuclear+hydro though)

(and Norway too with its massive hydro capacity)

Because the European grid usually has less demand, more supply in summer and more demand, less supply in winter. This leads to EDF scheduling most maintenance and refueling for nuclear power plants in summer. This year was particularly bad because the normal summer maintenances were accompanied by 1. a bunch of delayed maintenances that didn't happen due to COVID-19; 2. a potential issue with welds in a safety cooling system which was found in 12 of the more recent reactors and required some unplanned shutdowns to investigate and (sometimes) repair.

> which is ultimately done with the inertia of huge rotating chunks of iron.

Not "ultimately", "incidentally". How do you think microgrids work without giant spinning masses? There's no technical reason wind or PV can't provide inertia, just need to program the inverters to help maintain frequency rather than just follow it.

Synchronous condensers as mentioned in the other grid solves for you, but there's loads of interesting research currently looking into running large scale grids without any synchronous components.

https://www.pv-magazine.com/2022/06/08/new-model-for-grid-fo...

Other options include this where they demonstrate that they can switch between synchronous condenser and generator mode. Allowing a Power 2 X plant to provide system stability when it is not needed.

> 2011: first synchronous condenser conversion, from a 473 MVA generator to a +360/-210 MVAr synchronous condenser, making it possible to change between generator and synchronous condenser mode, depending on the season;

https://www.modernpowersystems.com/features/featurege-synchr...

> which is ultimately done with the inertia of huge rotating chunks of iron

Grid-scale batteries are fabulous for maintaining frequency, and handling the inconsistency of renewables.

Synchronous condensers do just that, but they're essentially the same as a turbogenerator of the same VA rating, except with no input shaft.

Those are the flywheels I was referring to, yes.

Metals are energy intensive and we can't afford to build generator-equivalent machinery that doesn't generate.

A lot of other replies are deluded about the scale at which inverters can operate, but what else is new.

Synchronous condensers and grid flywheels are two different things, the former is synchronous, hence rpm locked to instantaneous grid frequency. These provide very short term stability, and are not energy storage (due to the small acceptable variance in grid frequency), and are normally used for dynamic grid-scale PFC. Flywheels are asynchronous and inverter-driven.

Reply on news.ycombinator.com