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Comment by Gwypaas | Hacker News Reader

How are you going to generate power with your fusion plant? Steam?

Coal and nuclear are uncompetitive simply from the cost of the steam side. Today you can just about give a steam plant free energy and it still makes a loss.

Solar or wind does not have this limitation. CCGT gas plants gets around it by having a turbine giving raw mechanical power and then utilizing the same awful steam side to get the last percentage points of efficiency at a much smaller required scale.

Unless you can step around the steam turbine I am not so positive on fusions future outside of incredibly small niches.

Coal still gets built where gas infrastructure does not exist, but that's about it.

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> uncompetitive ... cost of the steam side ... it ... makes a loss.

Huh? Whatever gave you idea that electricity production needs to be a profitable endeavor? The considerations for choosing technologies should be availability, sustainability, safety (of the plant, the population, the environment), etc. - the price of electricity can be set arbitrarily afterwards, and if there's a loss then taxes will cover it, or subsidies + taxes to cover those.

So, the question of whether to use steam or not is not a question of profit-and-loss.

Why would anyone subsidize nuclear instead of batteries?

(Well, I know why, and yes, they would favor nuclear jut after oil and coal. But it wouldn't happen for any good reason.)

Lets create a market of everyone installing solar and trying to decouple from the power grid because you're forcing them to use more expensive power?

I don't understand your comment. You seem to be indicating that I am somehow opposed the wide use of solar or that I support wide use of nuclear power - neither of which is the case. I'm just saying that steam turbines being "non-profitable" is not a consideration in whether or not to use them.

You're proposing using laws or tax payer money to subsidize certain power generation. That's bound to lead to issues, like for example the now cancelled Virgil C. Summer.

https://en.wikipedia.org/wiki/Nukegate_scandal

All economic systems (with division of labor) are arrangements in which the efforts and the products of people's work are channeled in certain avenues. Laws and taxes are just some particular mechanisms within such systems. You (or I) might find certain laws or taxes beneficial or detrimental of course.

Anyway, if the use of steam turbines is justifiable in terms of feasibility, efficiency, safety, costs (monetary or otherwise) etc. - then it is justifiable, period; and if it isn't, then it isn't. And the same goes for nuclear power plants. Otherwise you're arguing that we shouldn't use technology X because some US state is too corrupt to make it work. If that's your argument, I understand where you're coming from, but - USers should fix _that_ problem, not suggest that we forego the technology entirely.

Perhaps there's the possibility of nuclear power by direct conversion to electricity:

https://en.wikipedia.org/wiki/Direct_energy_conversion#Trave...

Are steam turbines truly so inefficient? Can you source that?

They run at 30-35% efficiency with a humongous amount of machinery to support them. Heat exchangers, pumps, condensers.

Compare that to the simplicity of a jet turbine where you get raw mechanical power out. They take pretty much the same engine as an airplane engine and instead of having the turbofan putting that shaft into a generator. That's all there is to it.

Today new built renewables are in most cases cheaper than the marginal cost of paid of existing coal and nuclear plants. Gas is on the edge.

That is the reality facing these investments.

>They run at 30-35% efficiency with a humongous amount of machinery to support them.

Oh wow, I didn't know that, yikes. Can link me a source to find out more?

From a super pro nuclear source:

> Nuclear plants currently being built have about 34-36% thermal efficiency, while one of the new reactor designs boasts 39%. In comparison, new coal-fired plants approach 40% and CCGT plants reach 60%.(4)

https://world-nuclear.org/our-association/publications/techn...

This is the reason for Pressurized Water Reactors (PWR). Then you can increase the temperature and through Carnot's theorem reach higher efficiency. But now you have a pressurized reactor with another host of complications...

Since a coal boiler is much simpler in construction than a reactor, and do not rely on water to slow down the neutrons causing the chain reaction, they can do more fancy stuff and use supercritical steam leading to the higher, but still not good efficiency.

Something I don't get...

Wind turbines are efficient (to convert mechanical wind energy into electric energy) between 20% and 45% (with a theoretical upper limit of 59%).

Solar panels between 15% and 22%.

Both with variable input energy.

So I am not sure how 34-36% thermal efficiency is so bad, especially for a near-continuous production (or at least, with a predictable thermal input)?

Because for a solar panel or wind turbine that efficiency is simply lost energy. Catching more is better but as long as it is economical it is fine.

For thermal power plants you need to spend money taking care of the waste head leading to more costs.

Fascinating, thanks for sharing!

The last coal plant in the US cost $600M to build. And the steam turbine and everything else required to turn heat into power comprises the majority of a coal plant.

And?

I don't understand this. What makes a steam plant so lossy when the source is basically free (ie nuclear)? Is the steam somehow expensive to produce?

Yes, steam is expensive to produce, utilize and cool.

What's the expensive part when you've got free heat?

Literally nothing. But the heat is never actually free. You have to build and run a bunch of infrastructure to turn the raw heat into steam. Even if you're iceland with "free" geothermal you need to spend money to capture the heat as steam.

If steam were free like the wind nobody would care.

Comparing efficiency is a really apples to oranges way to go about this and should be a massive red flag that someone has an axe to grind.

Comparisons across different forms of generation typically look at cost (in dollars, carbon output or any other metric you want) per energy over the life of the thing doing the generating or per some multi year period.

Yeah, that's why I was asking. Why do we even care about efficiency? All I care about is dollars per watt/hour.

https://www.lazard.com/perspective/levelized-cost-of-energy-...

The last coal plant built in the US cost $600M for 900MW. Most of the cost of a coal plant is the apparatus for turning heat into electricity (the turbine etc).

Even if you have free heat, turning that free heat into electricity is more expensive than solar electricity.

That's power, you want energy. What is the total cost in dollars per Wh?

The entire part where you need to build machines to gather, use and cool it down.

> Coal and nuclear are uncompetitive

In what sense are there uncompetitive? Do you take into account that they work on demand (and not only when wind/sun is available).

Try working on demand 20% of the hours since renewables easily without anything fancy reaches those levels.

Now your horrendously expensive plant became even more expensive.

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