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Comment by pydry | Hacker News Reader

>We can get far without worrying about the last 5-10%. The solutions for the last 5-10% could be fossil fuels in the short-term, long-duration storage as it matures, or easily storeable e-biofuels.

I think a lot of people truly dont get this.

Those days when the wind isnt blowing, the sun isnt shining and the batteries and pumped storage are depleted can be easily handled with, e.g. power2gas.

It's pretty expensive (per kwh almost as much as nuclear power) but with enough spare solar and wind capacity and a carbon tax on natural gas it becomes a no brainer to swap natural gas for that.

Nonetheless this wont stop people saying "but what about that last 5-10%?" as if it's a gotcha for a 100% green grid. It isnt. It never was.

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The article ignores hydropower. The numbers/prices look a lot better with solar + wind + hydro + battery.

Norway runs almost entirely on hydropower. Sweden has a lot.

Iceland runs on hydropower and geothermal.

Hydroelectric capacity is largely built out, so you can look at current generation mix to see how much it is likely to contribute.

In the US capacity is likely to go down (dams are expensive and many time old dams are removed instead of being rebuilt).

I’m happy to be wrong about this globally, but in my neck of the woods the readily exploited hydro resources are already exploited to 90% of their capacity and have been for 100 years. Hydro is in many ways the ultimate renewable energy, but that’s been true since electrification and we’ve been using it as part of the energy mix since then. I’d love to be wrong but my understanding is that there isn’t a huge amount of untapped new hydro capacity available without having severe impacts on ecosystems

Hydro in Norway goes very well with windmills in Denmark.

Very simplified:

Wind blows mostly in Denmark during the day, so Norway stops hydro during the day and imports electricity from Denmark's windmills.

During night the wind is mostly still in Denmark so windmills don't produce much and Denmark imports from Norway's hydro.

In this way you can stretch the capacity from hydro using windmills even though Norway isn't a good place for windmills.

Also what is probably used in your country is Pumped-storage hydroelectricity . During the day you pump water into the reservoir using wind/solar energy and discharge e.g at night .

Elsewhere in the country yes but lol not so much in the very flat part of Western Canada. I pulled out some topographic maps a few years ago and was quite dismayed at the lack of elevation change suitable for pumped hydro.

In the last decade or so hydro generation has grown about as much as solar and wind (they all basically grow about the same amount as global nuclear generation, hydro doubling and wind and solar growing exponentially from basically zero).

So it's not going to take off like solar but it's a big chunk of relatively clean electricity production and it's often basically a byproduct of managing water supplies. It also pairs really well with renewables as even without pumps it has a degree of flex and storage.

This is even more true with international grid connections. Europe in a cold spell? Solar countries import, wind & hydro export. Europe in a heat wave? Flip the switches the opposite direction.

And nuclear is already in the 5-10% range in the US, so if we just maintained that level, we could get carbon free.

No, you couldnt. Nuclear power is not dispatchable.

> Nuclear power is not dispatchable.

I mean it is, its just slower.

but if you have batteries, then you can divert the power to the batteries to keep them topped up.

While technically possible, given that the vast majority of the cost is capex and not fuel and given that it is already five times the cost of solar and wind when producing at 100% 24/7, setting literal piles of cash on fire might be more economic than using it to dispatch electricity.

If you're using it to charge batteries it's just five times more expensive than equivalent solar or wind.

French nuclear stations are roughly as fast as combined cycle gas (to turn off at least)

The point is, with enough battery, you don't need fast despatch for things like water/gas/nuclear, because the battery does that for you. In the UK the 11gwhr we have (about 1/2-1/3 of one hours consumption) is more than capable to do the balancing.

No, because most of that nuclear generation would be during times it wasn't needed. The residual 5-10% in the renewable + batteries world is highly nonuniform, utterly unsuited to being covered by nuclear.

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