Science News

Turning Sunlight into Steam

Sun, 25th Nov 2012

Dave Ansell

Part of the show 3D Printing Replacement Cartilage

Steam is useful for a huge number of purposes ranging from running steam engines to sterilising medical instruments, but producing it uses a huge amount of energy.  This is particularly a problem if you only want a small amount of steam, as most of the energy you use goes into heating the water before it becomes steam.

 Steam train on the Albbähnle branch lineNaomi Halas and collegues at the Rice Quantum Institute, Rice University have been improving the efficiency of this process, using a principle first used by Stevenson in his Rocket steam engine.  Stevenson did it by sending the gasses from his fire through small pipes, dramatically increasing the surface area of the heater.  Publishing in the journal ACS Nano, Halas et al have done it by spreading metallic nano-particles, each about a 20,000th of a mm across, throughout the water.  This creates an enormous surface area and can absorb light very effectively.  If you then focus sunlight onto the water the energy is absorbed by the particles and transferred to the water very quickly.

Even without optimisation, about 24% of the energy goes directly into producing steam.  This means that they can even produce steam directly from ice water.

The first place this could be used is for sterilising instruments in the third world, but it could be generalised to wherever there is plenty of sunlight and a requirement for steam.

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Very interesting. Could you use it for steam driven engines as maybe a locomotive? Like having some encapsulated 'see through box filled with water and those particles. It would be a very 'green' energy it seems? yor_on, Sat, 1st Dec 2012

According to the article, the method makes use of about 24% of the available solar energy. That is slightly more efficient than the best photovoltaic cells. However, it is much easier to transfer electric power from a source to the motor than to transfer steam to an engine.
Imagine a train with 1000 square meters of photovoltaics on top of its cars. They could send about 200 kilowatts to the engine. A typical electric locomotive is rated around 5000 kilowatts.
Imagine a train with 1000 square meters of steam panels on top of its cars. They could generate about 240 kilowatts of steam power, but much of that would be lost as the steam is piped to the engine. Besides, steam engines are less efficient than electric or Deisel.
A solar powered train would be very slow; it would just be in the way of much faster trains. Phractality, Sat, 1st Dec 2012

Yeah, guess you're right Phractality, but it took my imagination away. It would be a good good thing if we found ways to use nano technology for macroscopic endeavors. I have a really interesting link, if I now can find it?

Yep http://theconversation.edu.au/show-us-your-carbon-nanotube-artificial-muscles-3821 (2011)
And..  http://theconversation.edu.au/power-to-you-carbon-nanotube-muscles-are-going-strong-10747 (2012)

Wonder what you could do with this concept?
=

If we now will find the time to develop it?
(Seems too many still are putting their heads in the sand when it comes to Global warming.)
yor_on, Sun, 2nd Dec 2012

Put the "steam panels" along the track, Get the steam to feed a turbine and make electricity. Use that to run the train.

Even a reasonably efficient way of making steam is a useful thing it it avoids using non renewable energy. Bored chemist, Sun, 2nd Dec 2012

Sweet thinking BC, wonder how thick a layer of 'particles in water' need to be for optimum efficiency, utilizing the effect? And also if it is doable with a plastic material? Maybe one could make it as a sort of plastic carpet? And how to keep the water clear? yor_on, Mon, 3rd Dec 2012

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