Mechanical power generation using Earth's ambient radiation
24 comments
·December 7, 2025jcims
DIY radiative cooling paint from YouTuber NightHawkInLight - https://www.youtube.com/watch?v=N3bJnKmeNJY&list=PL1a2HkcVbm...
It has pretty impressive performance.
Tech Ingredients did one or two vids as well - https://www.youtube.com/watch?v=dNs_kNilSjk
Was thinking of whipping up a batch for my rv.
kumarvvr
This concept is used all over India to cool down homes that are on the top floors.
https://www.amazon.in/EXCEL-CoolCoat%C2%AE-Reflective-Coatin...
Basically, have a highly reflective white coat on your roof, to reduce temperatures by about 3 Degrees Celsius.
Almost all homes in Urban India are made from concrete and bricks, which can hold a lot of heat.
I myself have been in houses that use this to cover only some rooms of the house (mainly the bedroom), and the temperature difference is definitely noticeable. It also makes the room livable in the extreme hot summers in India.
phyzome
If anyone is interested in passive sub-ambient cooling (not for power generation, just for "free" cooling) I strongly recommend https://www.youtube.com/@Nighthawkinlight -- he has been doing a lot of experiments in this space and releasing recipes as he goes. Stuff you can do in your kitchen.
HPsquared
Somewhat different, but this reminds me of an approach that uses temperature gradients in the ocean to power a heat engine.
https://en.wikipedia.org/wiki/Ocean_thermal_energy_conversio...
jasonpeacock
OTECs are amazing, and step 1 of "The Millennial Project: Colonizing the galaxy in eight easy steps"[0]
[0]: https://en.wikipedia.org/wiki/The_Millennial_Project
There's a shore-based research OTEC in Hawaii, but the best is a floating, closed-loop OTEC in the ocean.
AstroNutt
Interesting link. I would think step 7 would come before step 6 though. I thought about this for a few minutes and can't come with a reason otherwise.
andbberger
wiki article states "Up to 10,000 TWh/yr of power could be generated from OTEC without affecting the ocean's thermal structure". which converts to about 500GW which... isn't that much
nine_k
This can't be correct.
10,000 TWh/y = 1e+7 GWh/y, divide it by 365.25 days/y to produce daily output of 27,379 GWh/day, then by 24 h/day to get pure power of 1,141 GW. It's still more than a terawatt, three orders of magnitude larger than the largest nuclear reactors.
pezezin
10 000 TWh/yr is one third of the current total electric energy generation of the whole planet, is not a small amount.
Source, page 39 of the full report:
https://www.iea.org/reports/global-energy-review-2025/electr...
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clickety_clack
In one of the later Foundation series books, Isaac Asimov had a whole world run on this.
coder543
Which book? Which world? I don't remember this, but it has been a few years.
kogasa240p
Since we're talking about stirling engines, I've always wondered how using geothermal heat for a larger stirling engine would work.
https://youtu.be/duuk_r--lqU?t=99
Even though the video uses the sun to heat the oil, I would think it would be feasible to use geothermal heat instead.
rriley
Great! Now I desperately need this Stirling engine for my morning coffee: https://a.co/d/6Ja2LeF
Video of how it works: https://www.youtube.com/watch?v=Q5QEBqjkNjo
AnimalMuppet
400 milliwatts per square meter? That's interesting that they can do it at all, but that level is completely impractical for real use.
15155
This is plenty of power to run a microcontroller and a radio (sporadically) with an energy-harvesting setup.
aetherspawn
> the generation of >400 milliwatts per square meter of mechanical power with a potential for >6 watts per square meter.
Keep in mind the power is fully mechanical so no electricity or control circuit is required. And based on the simplicity it seems like a good candidate to power something that you need to last 100 years with no maintenance for example.
abeppu
I think the "last 100 years with no maintenance" is not likely feasible with this approach. The top plate has a coating that supports high infrared emissivity -- and I think it would need to be regularly cleaned to work well. And you can't really prevent it from getting dirty by enclosing it b/c that both substantially changes the performance and moves the maintenance burden to cleaning the enclosure.
AnimalMuppet
Mechanical things don't usually work for 100 years with no maintenance. Bearings run dry, if nothing else.
ufocia
Air bearings always run dry without problems.
foxglacier
So what? It's research, not business. Surely you didn't expect they'd found a practical source of free energy that was ready to compete with solar but somehow nobody else bothered to try before?
nrhrjrjrjtntbt
It is interesting to know if it has potential (pun intended) for some use. Even if that is some very niche thing.
Vid of the engine in action, from the team that made the paper
https://www.youtube.com/watch?v=5VSmBl8Rv_o
This one shows that it is not as unbelievable as it sounds :)
https://youtube.com/shorts/9KuTdPGqhVo