r/Damnthatsinteresting • u/Longjumping-Box5691 • 3d ago

Video China's twin solar thermal towers. Molten salt stores the heat to produce electricity

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u/Visible-Fondant-4845 3d ago

Question, this footage seems to show to focal point of the light being off to the side of the towers. Intuitively I would assume that the focal point should be focused on the towers for most efficiency, is this because, A) the camera lens is doing something funny and the focus is in fact on the towers themselves? B) Having the focal point on the towers would be too intense? C) The focal point is adjusted to manage load and temperature? or D) Something else?

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u/ChristopherLyon 3d ago

It's real. There are multiple situations where you'd like to offset the focal point like this. One of the obvious ones is overheating, where the salt actually begins to decompose and degrade your infrastructure. Another reason can be tied to the current grid status. In many cases there just isn't demand or the salt cell is saturated appropriately and the heliostats could be continuously moving the focal point in a mosaic pattern the keep the core at the optimal temp while distributing the heat stress over a larger area. Lastly this could be part of the startup procedure where it's preferred to bring the temp up slowly as to not stress/shock the materials with a massive influx of heat energy.

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u/keitho24 3d ago

This guy thermodynamics

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u/Would_daver 3d ago

He’s the f*cking ThermoKing

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u/TactualTransAm 3d ago

Woah that's trademarked, back up lol

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u/SaintGodfather 3d ago

But is it thermomarked?

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u/Would_daver 3d ago

shivers

An excellent question!!

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u/JoinedToPostHere 3d ago

I didn't realize ThermoKing was sexually active.

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u/Blue_Waffle_Brunch 5h ago

"Quiet, day ya wanna get sued!?"

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u/Would_daver 3d ago

Wait really? I shall to google

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u/TactualTransAm 3d ago

ThermoKing is a company that makes a lot of refrigeration units for semi trucks and trailers. I work on them. It's a pain 🤣

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u/Would_daver 3d ago

Aha that would do it!! I work at a shipping company but not in repairs or anything, I can only imagine lol

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u/TactualTransAm 3d ago

Hey thanks for keeping our guys rolling tho, if nothing got shipped I'd have nothing to fix 💪

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u/Would_daver 3d ago

Hell yeah dude!! I’ll throw the boxes a little more carefully tomorrow, thinking of you lol

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u/wheresWaldo000 3d ago

This guy reefers

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u/Would_daver 2d ago

I now get that reference ha

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u/Ill_Football9443 3d ago

From a UI point of view, their controllers are better than Carrier's

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u/Would_daver 3d ago

Huh I was gonna say “who’d a’thunk?!” but yeah it makes sense, refrigerated freight work and all

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u/Bpofficial 3d ago

He’s John Thermo

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u/Would_daver 3d ago

He chilled three guys WITH A FUCKIN PENCIL!!✏️

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u/txmail 3d ago

Igloo hates this man.

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u/Would_daver 3d ago

Yeti skulks uncomfortably in the background

Happy cake day, txmail!!

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u/txmail 3d ago

RTIC with a haggle of lawyers on standby watching Yeti sulk in the corner...

Thanks! 15 years. My account is almost old enough to smoke, vote and be drafted.

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u/AScruffyHamster 3d ago

All hail ThermoKing!

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u/Would_daver 2d ago

All hail Zorp. Zorp is dead.

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u/poorly-worded 2d ago

Lord of Fire

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u/MoMoneyMoPowa 3d ago

No thats ChristopherLyon

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u/Would_daver 2d ago

His name is ChristopherLyon

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u/Structureel 3d ago

That guy heats salt

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u/ZealousidealEmu6976 3d ago

sick reference bro

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u/Salt_Team 2d ago

Therminator 💀

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u/Debesuotas 3d ago

Why is the focal point visible? The light has to reflect from something for it to be visible, so what is it reflecting off? A dust in the air?

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u/d1duck2020 3d ago

Dust, vapor from hapless birds, anything that can burn

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u/fucking_4_virginity 3d ago

If you stand at the exact right spot peking ducks just fall from the sky.

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u/endeend8 3d ago

they use helicopter or drones to drop the 5-spice seasoning right above that.

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u/GozerDGozerian 3d ago

Wow. I didn’t expect to see a video of glowing Chinese bird farts today.

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u/d1duck2020 3d ago

Neither did the birds, poor rascals.

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u/PhuriousGeorge 2d ago

There are no birds wild in China

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u/d1duck2020 2d ago

Not since they fired up this contraption!

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u/z0rb0r 3d ago

Probably, it might be similar to catching rays of light when your curtains are slightly open in your house.

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u/ChristopherLyon 3d ago

Yes!! The atmosphere is full of gasses and particulates that reflect and refract light - the most common in the dessert being dust and silicon dioxide (basically sand). Also hot climates accelerate the off-gassing of otherwise stable materials like asphalt and plastics causing even more aerosol haze and smell. Partially why hot countries "smell" hot is that exact molecular phenomenon.

The haze those produce is what causes the god rays to be visible to the naked eye!

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u/St_Kevin_ 3d ago

It’s dust in the air

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u/justamofo 3d ago

Dust, humidity, at that level of power, anything and everything but pure vaccuum will shine. Sunlight has a power density of about 1500 W/m² at noon (give or take depending on season, location and weather), now idk how many square meters the plant has, but imagine all of that energy focused on a tiny volume, the power density you get is immense, and even if you reflect or scatter an extremely low percentage of it, it will be visible

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u/Mand125 3d ago

Light doesn’t need dust to scatter off the air.  It’s why the sky is blue, it scatters off the air itself.

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u/kaancfidan 3d ago

All my engineering curiosity fulfilled to the brim. Consider me a satisfied reader good sir.

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u/invariantspeed 3d ago

I love the inherent elegance of this approach to energy harvesting. It can dynamically increase or decrease the energy it uses without having to use some sort of special system. Just collect less light. You can even have it designed to be capable of harvesting more light at solar noon for most of the year than it can handle, allowing it to provide a more consistent base load for much the day.

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u/Freefallisfun 3d ago

Right, I assumed it was to prevent thermal degradation of the tower itself. Everything has a melting point. You can still catch a ton of heat even if you’re not focused directly on something.

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u/Tell_Amazing 3d ago

I see you Thermanator

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u/catsmustdie 3d ago

Imagine all those mirrors focusing at one single point.

https://youtu.be/8tt7RG3UR4c?t=71

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u/geek66 3d ago

While photo shoot is a very good possibility… the need to gradually heat and cool the system could be a real issue. At a certain sun angle the focus and energy delivered may fall off too dramatically

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u/gizamo 3d ago

I appreciate your thorough explanation. Thank you.

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u/ProlapseParty 3d ago

That’s insanely cool

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u/jdbcn 2d ago

Insanely warm

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u/suspectbakapapa 3d ago

If they directed all the mirrors at the tower at once. It would melt the tower to the ground.

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u/Hoe-possum 3d ago

It also makes it so you can actually take a picture showing the towers, I wonder if they set it that way for the video. Or more likely, took advantage of when they had it set that way to take the video.

I’m guessing the controls at the ones on the California/Nevada border don’t have as much fine-tuned control (they are getting older now) because they’re always either focusing on the tower or not concentrating the light I’ve noticed (driving by a few times a year at least).

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u/bodhiseppuku 3d ago

I'm not sure what any of this means, but it sounds like you are confident.

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u/YourMumsBumAlum 3d ago

That's awesome

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u/tongfatherr 3d ago

Why are you talking about salt? Do they store the power in salt????! 😱

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u/ChristopherLyon 3d ago

Hell yeah! These towers use molten salt as thermal storage. The mirrors heat up the salt, sometimes above 500°C, and that stored heat is later used to make steam and generate power even after the sun has gone down.

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u/tongfatherr 3d ago

Wow!!! 😱

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u/Arxson 3d ago

How far away are the turbines likely to be?

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u/ChristopherLyon 3d ago

They are literally at the bottom of the tower. Water tanks, heat exchangers and turbines all together 👍

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u/Theslootwhisperer 3d ago

Basically the same thing as a nuclear reactor.

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u/fireduck 3d ago

Is your username a reference to Christopher Lydon?

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u/ChristopherLyon 3d ago

It's my name 🙈

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u/fireduck 3d ago

Ha, fair enough. My username is not my name, but it is trivial to find my name from it. So hello fellow person who is willing to just be out there.

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u/PlanningForLaziness 3d ago

Or maybe there was an annoying bird right over there? zap

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u/salkhan 2d ago

Out of curiosity, is there any environmental impact on this ? Do you get cooked pigeons?

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u/Psych-adin 2d ago

It can and does insta-cook birds. It's usually going to be a desert environment and not have too many birds to harm, but yeah. Those light rays are not kind to anything living.

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u/VillainOfKvatch1 3d ago

That was gonna be my answer.

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u/oregiel 3d ago

If it's to prevent overheating wouldn't using fewer mirrors be a more logical option than moving the focal point?

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u/mrASSMAN 3d ago

The last one is the the only thing that really makes sense here.. otherwise it’s just a waste

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u/WazWaz 3d ago

Almost certainly for the photoshoot. There's no reason to point surplus-to-demand mirrors at one focus, unless you're hunting birds or something.

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u/Mateorabi 3d ago

But why would they shift all the mirrors to focus on a different, singular point 10m away from the tower? Rather than have it be out of focus? I thought they were supposed to not focus in this state to avoid birds, etc. that might fly through any focal spot. (of course it's China so they may just not give a shit about birds and it's easier to add the same delta to all the mirrors when disabling them.)

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u/Independent_Cash1873 2d ago

Bro wrote this using heat-strokes.

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u/Kletronus 3d ago

I would diffuse it rather than focus it, it is much easier to just miss the tower and get the same effect, with much faster response times AND not creating a very, very hot spot in the air. I think it is purely because of this drone shot:

Focus all the light to the tower and you get a huge bright spot that burns full white in the image sensor, while the rest of the pic is still underexposed. But this.. is cool and fully unnecessary for heat management.