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MIT Combines Carbon Foam and Graphite Flakes For Efficient Solar Steam Generati
rtoz (2530056) writes Researchers at MIT have developed a new spongelike material structure which can use 85% of incoming solar energy for converting water into steam. This spongelike structure has a layer of graphite flakes and an underlying carbon foam. This structure has many small pores. It can float on the water, and it will act as an insulator for preventing heat from escaping to the underlying liquid. As sunlight hits the structure, it creates a hotspot in the graphite layer, generating a pressure gradient that draws water up through the carbon foam. As water seeps into the graphite layer, the heat concentrated in the graphite turns the water into steam. This structure works much like a sponge. It is a significant improvement over recent approaches to solar-powered steam generation. And, this setup loses very little heat in the process, and can produce steam at relatively low solar intensity. If scaled up, this setup will not require complex, costly systems to highly concentrate sunlight.
SpongeBob Square Solarpanel?
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Could it be used for de-salination
I hadn't previously heard of this MIT' before. I hope we see good things from them.
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“There is still a lot of research that can be done on implementing this in larger systems.”
Translated;
“There is still a lot of research that MUST be done TO IMPLEMENT this in larger systems.”
If its boiling water I suspect it won't get too gunked up, except possibly for the bottom-most layers I suppose.
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They found they were able to convert 85 percent of solar energy into steam at a solar intensity 10 times that of a typical sunny day.
> if scaled up, this setup will not require complex, costly systems to highly concentrate sunlight.
So, mirrors are costly now - does that imply that this carbon foam stuff is cheaper to produce than a sheet of polished stainless steel? If so that *is* promising.
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Also - bleach. Doesn't take much to render water unfit for life, and if you're capturing the steam (presumably under pressure) then you're likely dealing with a closed-loop system, with the carbon absorbing virtually all of the sunlight vital to algae growth.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
Didn't RTMF... What happens when it gets all gunked up with algae?
It seems fouling would be a big problem in an open system. If you had a closed system, sandwiched the material under a glass plate and circulated pure water or some other fluid in a closed system, with a heat transfer means on a bottom plate, then maybe that would make a usable system. But that would also reduce efficiency by some amount.
Only if you are boiling pure water, otherwise you will likely get mineral deposits and such rather quickly.
that's what I came to post.
the inefficiencies of steam-powered power-plants are in the moving parts of the rankine cycle. this device helps create the steam (one of the four major parts of the rankine cycle), but we can't harness it to do work.
The summary states "if scaled up, this setup will not require complex, costly systems to highly concentrate sunlight". But the video itself says that all of their testing was done with light at 10x normal solar intensity. In other words - you still need concentrated sunlight, you won't be able to set this beaker out in the bright sunshine and expect it to start boiling. The authors contrast it with solar power towers that concentrate sunlight to 100x or 1000x, but it still sounds like you'd need concentration of some sort.
> the inefficiencies of steam-powered power-plants are in the moving parts of the rankine cycle
No, the inefficiencies of the Rankine cycle come from fundamental laws of thermodynamics and are inherent to all heat engines.
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The quickest numbers I could find say that at the scales of large power-plants, the generator is very efficient, but the turbine not so much, around 50%. This would put the system as a whole at around 40% efficency sunlight -> electricity. That's competitive with the best solar voltaic systems tested in the lab, and 50-100% better than practical systems on the market. Assuming their system really does scale up to power plant sizes, of course.
Water in a typical closed steam system is managed with various chemicals, and not simply pure water. That is because even with pure water, you will always get some interaction with the system elements and oxygen or whatever gases are present. Methods for managing that have been optimized for large steam plants. Who knows what would "get into the water" even in a closed system with this material and whatever others are required.
I wouldn't assume you can produce high pressure steam with any velocity through this foam. It appears very fragile, and would probably get torn apart by even a low flow approach. If true, that makes a direct closed system approach unlikely. If not true, it still would appear to require a huge exposure area to produce any usable output, which presents significant flow management and collection problems.
So, not all slashdotters are as lost on the matter as you may suppose.
The most efficient way to do that is to reduce CO2 in the air.
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