this post was submitted on 31 Aug 2025
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The world's largest sand battery just went live in Finland (newatlas.com)
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[โ€“] blargh513@sh.itjust.works -4 points 1 month ago (7 children)

Maybe I'm dumb, but why are we still using steam turbines to turn heat energy into electricity?

There really isn't a more efficient process? Going from a heat source, transfer to water, change of state to gas, use hot gas + pressure to turn a mechanical generator/dynamo and THEN you get electricity.

There are so many failure points, maintenance points, and efficiency losses in that path.

We really have no means to convert heat energy to electricity? We do it with solar, we dont use sunlight to boil water.

What is missing here?

[โ€“] Hotzilla@sopuli.xyz 3 points 1 month ago* (last edited 1 month ago) (2 children)

Large scale three phase energy generation is always something rotating in sync with the grid. Easiest way to do that is to spin turbine+generator.

All nuclear, coal, biomass power plants just heat water to 300-800ยฐC and push it through turbine.

The thing is that it is really quite robust, and there isn't any other good solutions to it. They do have quite a lot of loss, but the cooled water after process (still over 100ยฐC) can be used in other industries or district heating improving the efficiency.

Hydropower just spin the turbine with water flow. Wind directly spins the turbine, which is good for efficiency. Solar panels are still quite inefficient, but because they just use space, they make lot of sense even with poorer efficiency.

[โ€“] antipiratgruppen@lemmy.dbzer0.com 1 points 6 days ago (1 children)

the cooled water after process (still over 100ยฐC)

Steam, right? Describing steam as cooled water seems somewhat odd to me, but it is indeed still water its gaseous form. So, cooled steam of water?

[โ€“] Hotzilla@sopuli.xyz 2 points 6 days ago (1 children)

Those are pressured systems, the water is kept in high pressure, which means it is liquid water. When it goes through turbine it it steam, usually superheated.

In industrial settings you can get water to 350ยฐC in liquid form, it just about the pressure.

Even the city wide district heating networks water is kept at 3 bar, which can keep the water at liquid for 133ยฐC in the winter time.

[โ€“] antipiratgruppen@lemmy.dbzer0.com 2 points 4 days ago

Oh, I didn't think of that. Thanks for the explanation.

[โ€“] Tweak@feddit.uk 1 points 1 week ago

Solar panels are still quite inefficient, but because they just use space, they make lot of sense even with poorer efficiency.

You can't really compare those efficiencies with each other, between different technologies.

With fuel, you're talking about how much energy per kg.

With wind, you're talking about how much energy per m/s wind.

With solar, you're talking about how much energy over the whole solar spectrum that gets through the atmosphere. However, a single junction p-n diode made of silicon is only meant to work at a specific wavelength, and will only get energy from around this wavelength, and as such could only ever get a maximum theoretical efficiency of ~36% of the total solar spectrum of light wavelengths. In the lab I think some have achieved ~33%.

You can get higher efficiency solar cells, but you have to use novel materials and have multiple layers of different p-n junctions. Short wavelengths first, these materials are transparent to longer wavelengths, which are absorbed by lower layers. With a theoretical infinitely layered solar cell you could achieve ~88% of the solar spectrum energy. In reality it's really hard to make a semiconductor diodes that fit certain wavelengths, leaving gaps in the spectrum even with multiple diode layers.

~30% for solar cells sounds ridiculously low compared to like, maybe, 70% for fuels. But it's a completely different measurement. Grid scale battery systems are mayb 98-99% - but that's just electrical energy in and electrical energy out over a short time.

There is no common denominator, but the solar energy is free.

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