Thermo-Electric Generators | Hacker News Reader

Thermo-Electric Generators

douglas-self.com

46 pointsbasicplus225 comments

Fascinating article, although I would quibble with the statement that Curiosity's is the "most important RTG in the solar system". While technically now beyond the heliopause, surely the cluster of 44 year-old RTGs powering the two Voyager probes are at least as important: at least to those of us who were fortunate enough to watch their journey slowly unfold from the beginning.

Here's the correct link for the modern stove/generator: https://www.bioliteenergy.com/collections#campstove-family

Here is my latest and totally optimized portable TEG-unit. It has old computer coolers on both side and self-powered fan on the cool side. 10 Watts.

As an example we have it on top of Camping Gas - burner and it produces more LED-light than those creepy and dangerous gas lanterns.

https://photos.app.goo.gl/7rarj5hLdeTwwgF59

I cannot find the picture of the candle-powered LED-light. It was even funnier, because it produced 5 times more light than the candles alone.

I'm interested to see it, but I have to verify for Google sh1t. Do you have it online somewhere else? Is it a self-built TEG?

Shows on incognito page. It is your problem.

No need to feel offended. I was sincerely interested in it.

> As an example we have it on top of Camping Gas - burner and it produces more LED-light than those creepy and dangerous gas lanterns.

They were definitely dangerous, but creepy? I have fond memories camping in the light of those little deathtraps.

You do not appreciate those much, when something on fire is your only source of light. I remember making a led light maybe 1985. It had 30 leds and you could barely read a book in the light, but I was extremely happy.

From the article:

"Unfortunately, Ohm's law was met with resistance."

I'm glad the Prussian minister of education eventually saw its potential and now it's a current theory.

If someone can come up with a way to get solid state thermo-electric generators to overtake steam generator systems in efficiency, there will be substantial uses for them, and the world will become a very different place.

  * Solid state stuff can be made much smaller, and has no efficiency benefit with size.
  
  * They can be used in reverse to make a temperature differential, or generate electricity by eliminating a temperature differential.

  * For example, your oven could use one to heat up.  But then when you're done with the oven, it could generate power again to cool down.  The only theoretical loss is the heat in the cooked food.

  * They replace all 'cooling fans'.  Anything hot can be cooled *while reclaiming energy*.

* They replace all 'cooling fans'. Anything hot can be cooled while reclaiming energy.

Nope, to reclaim energy you need a temperature difference. If you want that difference, best bet is to use a radiator with a cooling fan. Inserting a device between your heat source and your heat sink will decrease transfer of heat.

Doesn't something hot (in the way we colloquially use the word) have a temperature higher than the surrounding air/metal/whatever?

When you have a gradient and you want that gradient removed you can allow the gradient to do some work while it excuses itself. When you have time/throughput constraints that you can only achieve with a fan then yes, adding something extra in between will likely fail making up for the additional fan power required. But in the same way as you could do away with the fan by increasing the size of the radiator involved, you could also tolerate a gradient harvester in between, by making the radiator even bigger. No physical principle broken. Economic principles broken? That's another story...

> will decrease transfer of heat

for the same size of cooling fan + device. You can always increase the fan if it means you're also going to recover some energy.

I don't see why this wouldn't work tbh. Say your CPU is hot and the room is cold. The desire end state is that the CPU will reach room temperature, with the room being warmed up a little (let's not talk about getting the energy out of the room). There is no alternative to this end state.

To reach the end state, you can dissipate the heat of the CPU in the room "as simply as possible", OR you could transform some of it to electricity, and use the electricity to power some other device, say a desk lamp, and heat the room that way.

Yes. This currently a little impractical because all cpu are on edge of their thermal transfer capabilities, so adding such device would cause termal throttling. It's very possible, just not economical yet.

I took that to mean something more like "in cases where we already exhaust waste heat, you could reclaim some of that energy". That does seem doable, my refrigerator is a little heat pump in reverse, why not stick a Peltier on the coils on the back and charge a battery to run LEDs to light the inside?

TEGs aren't the only technologies that can do what steam does. There are closed cycle gas turbines, for example, which do not combust a fuel but rather use heat differentials to convert energy. There's also Thermoacoustic generators as well, which are quite efficient and interesting to boot. Both of these have practical efficiencies that are already much higher than TEGs.

Useful compendium.

The thermodynamic efficiency issue with ALL TEGs is that it's governed by the temperature difference (akin to Carnot), which with semiconductor TEG materials is VERY LIMITED. Thus the efficiency and yields are going to be low grade because of this. This is also why RTGs with plutonium (e.g. Voyager) are the pinnacle and always will be. The best on Earth will also be nuclear powered for the same reasons nuclear is best for power and rockets: higher delta T possible.

This video presents a good explanation of how they work: https://www.youtube.com/watch?v=zzGnNkOxdpI

Very interesting to read the history of these generators. I recently came across the modern thermo-electric generator that is mentioned at the end of the article. It's small and portable, you can cook on it, and also charge your phone. Might come in handy for my bicycle caravan.

Would be interested to see the progress of solar mapped against this.

They seem fairly similar tech, with broadly similar histories.

I wonder why life never evolved something like this? It seems like it would be useful for places with large day/night gradients or around volcanoes

Do you mean like solar-powered nighttime lighting where the "battery" is just a big rock and the "photocell" is a temperature drop because the sun went down?

That might take a bit of engineering to work well, but it's a pretty good idea :)

- need a hot side/cold side

- generates electricity, which isn't directly useful for most life

- fairly terrible efficiency

- and the big one: life evolved photosynthesis instead, which was so effective it transformed the atmosphere of the planet.

(There are some interesting "volcano powered" creatures living around thermal vents in the deep ocean, but they work by metabolizing chemical output instead)

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