Turbines on a chip: super "batteries"

[Dr Mordrid]

Link....

After a decade of work, the first millimeter size turbine engine developed by researchers at MIT should become operational by the end of this summer. The new turbine engine will allow the creation of smaller and more powerful batteries than anything currently in existence. It might also serve as the basis for tiny powerful motors with applications ranging from micro UAVs to children's toys. In the more distant future huge arrays of hydrogen fueled millimeter turbine engines could even be the basis for clean, quiet and cost effective power plants.
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The millimeter turbine technology is based on semiconductor manufacturing techniques. This enables the fabrication of complex micro parts and assemblies – devices with dimensions in the 1-10,000 micron size range with submicron precision. Such parts are produced with photolithographically-defined features and many can be made simultaneously, offering the promise of low production costs in large-scale production.
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On the commercial market, millimeter engines could also have a large variety of applications ranging from refuelable batteries for consumer products such as laptops, digital cameras and cell phones, to cheap micro engines which could be used for agriculture, Micro-Electro-Mechanical Systems (MEMS), sensors and even toys. Although industrial applications such as power stations made out of large arrays of millimeter size turbine might still be a distant dream due to the low efficiency level of the millimeter engine, It is not inconceivable that in the future more efficient millimeter engines will be able to allow for a competitive alternative to existing power manufacturing technology.
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[DukeP]

Pretty darn nice.

I remember some talk about flywheel batteries, using micro flywheels in vacum.

But I have a bit of trouble seeing how you can store energy in a turbine?

The toys tho. The toys...

~~dukep~~

[az]

I don't see power plants (in the traditional sense) happening: Where's the advantage over larger turbines? Efficiency is worse, and burning hydrogen is not efficient anyway. People nowadays think everything that somehow uses hydrogen in its power generation is environmentally friendly, as if the stuff grew on trees.

[DukeP]

Actually, it does grow on trees.

The very first action in the type II photosystem, is the splitting of water into an oxygen radical and hydrogen.

But Im teasing.

~~DukeP~~

[Dr Mordrid]

Micromotors connected to the turbines do the generation, and with their minimal mass and friction the power ratio is quite high. MIT has run the numbers and they're convinced it'll be commercial, and they're largely the ones who broke the lithium battery puzzle (being commercialized by A123 Systems - GM Volt, California's hybrid fleet going plug-in etc.).

DukeP;

Funny you should mention water splitting. A titanium disilicide (TiSi2) semiconductor for photovoltaics was recently announced by the Max Planck Institute that is wide spectrum, splits water and separates & stores the hydrogen and oxygen.

Splitting Water with Sunlight

(PhysOrg.com)

Hydrogen is one of the most important fuels of the future, and the sun will be one of our most important sources of energy. Why not combine the two to produce hydrogen directly from solar energy without any detours involving electrical current? Why not use a process similar to the photosynthesis used by plants to convert sunlight directly into chemical energy?

Researchers from the German Max Planck Institute have now developed a catalyst that may do just that. As they report in the journal Angewandte Chemie, titanium disilicide splits water into hydrogen and oxygen. And the semiconductor doesn’t just act as a photocatalyst, it also stores the gases produced, which allows an elegant separation of hydrogen and oxygen.

“The generation of hydrogen and oxygen from water by means of semiconductors is an important contribution to the use of solar energy,” explains Martin Demuth (of the Max Planck Institute for Bioinorganic Chemistry in Mülheim an der Ruhr). “Semiconductors suitable for use as photocatalysts have been difficult to obtain, have unfavorable light-absorption characteristics, or decompose during the reaction.”

Demuth and his team have now proposed a class of semiconductors that have not been used for this purpose before: Silicides. For a semiconductor, titanium disilicide (TiSi2) has very unusual optoelectronic properties that are ideal for use in solar technology. In addition, this material absorbs light over a wide range of the solar spectrum, is easily obtained, and is inexpensive.

At the start of the reaction, a slight formation of oxide on the titanium disilicide results in the formation of the requisite catalytically active centers. “Our catalyst splits water with a higher efficiency than most of the other semiconductor systems that also operate using visible light,” says Demuth.

One aspect of this system that is particularly interesting is the simultaneous reversible storage of hydrogen. The storage capacity of titanium disilicide is smaller than the usual storage materials, but it is technically simpler. Most importantly, significantly lower temperatures are sufficient to release the stored hydrogen.

The oxygen is stored as well, but is released under different conditions than the hydrogen. It requires temperatures over 100°C and darkness. “This gives us an elegant method for the easy and clean separation of the gases,” explains Demuth. He and his German, American, and Norwegian partners have founded a company in Lörrach, Germany, for the further development and marketing of the proprietary processes.

[Wulfman]

MIT has run the numbers and they're convinced it'll be commercial...

nothing against the MIT here (good track record), but still - they probably have the patent, who else should be convinced if not them?

mfg
wulfman

[Dr Mordrid]

You know darned well a spinoff company is coming. In fact that's what A123 Systems is - an MIT spinoff.

[Technoid]

so in the future my pda will occasionally have to be refueled and occasionally it will fart?

[az]

Your source actually says that the efficiency is low, so I don't see why you try to argue otherwise.

Of course it's interesting stuff, and developments like this could even lead to decentralized distributed power generation, but that has nothing to do with its unsuitability for large-scale power generation, and the fact that people seem to become drooling idiots believing in wonders when they hear the word hydrogen.

[Dr Mordrid]

Low now, but this is the model-T stage. And if you recover the generated heat what happens to the efficiency of larger arrays?

[Brian Ellis]

Actually, there isn't a great deal that is new here. It is just logical development of technology that has been on the go for nearly two decades and which you all have in your cars (at least unless you have a 5-year old banger!). I'm talking about the inertial switches that trigger the air bags which are made by a combined pico-mechanical and electronic device etched on a silicon chip, using the same technology.

Let's also get this straight, this is a gas turbine, in the sense that a gas under pressure will cause the rotor to turn. It is not a gas turbine as in a device that burns a fuel and produces energy by the expansion of said gas, as in a jet or turboprop engine. Nor can it be, as silicon undergoes phase changes at ~200°C. This will work on compressed gas and hydrogen would be the least efficient as the kinetic energy stored per unit volume/pressure would be proportional to the density of the gas. However, as the article states, the efficiency of such devices is abysmally low.

The "home" of micro-electro-mechanical systems is Sandia Labs in Albuqerque which has been working on them for more than a decade and has developed all sorts of complex mechanisms (including the 3-dimensional inertial air-bag triggers; first image here; these analyse the amplitude and direction of the shock and deploy the right air bag(s) in consequence). You can spend some time looking through the photo galleries on this site. There is even a video showing a spider mite being taken for a ride on a "large" wheel driven by a MEMS motor. I mentioned this video in an article I wrote for a techie journal about 4 years ago, so I know the technology was well advanced even then.

[Dr Mordrid]

It is not a gas turbine as in a device that burns a fuel and produces energy by the expansion of said gas, as in a jet or turboprop engine. Nor can it be, as silicon undergoes phase changes at ~200°C.

Uhhh...wrong. This is an internal combustion engine, not a gas pressure acutator. You obviously didn't read the whole article

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A different micro sized gas turbine was developed by researchers at the Swiss Federal Institute of Technology (ETH Zurich). This tiny turbine reached a size of several centimeters producing up to 100 watts of electricity for a period of several days. Pushing the technology even further, researchers at the Massachusetts Institute of Technology developed the building blocks for an even smaller gas turbine engine with a size of about 1 mm which they hope will be fully assembled and functioning before the end of 2007.
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According to Professor Epstein, millimeter sized turbines also have many of the same design considerations as large turbines including basic layout, mechanical stress, oxidation-limit etc. In some respects designing a micro size turbine is simpler than a conventional macro one since the microrotors of the turbine are very stiff, eliminating bending problems which occur on larger rotors. Thermal stress is also not an issue at these sizes as well as maintenance of any kind (you will never fix a micro turbine but simply replace the entire engine).


Q: What were the major problems you faced on this project? What problems you still face?

A: There have been few easy challenges but the two most difficult problems have been (1) understanding the interaction between manufacturing precision and rotor-bearing performance, and (2) managing the tradeoff between the design requirements (of the thermodynamics, combustion, stress, fluid flow, and electromechanics) with complexity of the manufacturing process. In other words, how to achieve the functionality needed in something simple enough to build. This remains our largest challenge.
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Q: What will be the first applications of the micro-engine and what will be its price?

A: 10-50 watts for high end laptops and military gadgets (MIT work is sponsored by the US Army). Obviously it must be competitively priced or will not survive long in the market place. Detailed pricing is beyond my competence.

[Brian Ellis]

Uhhh...wrong. This is an internal combustion engine, not a gas pressure engine.

The diagram clearly states otherwise. Even if the materials were able to resist the temperatures, a peripheral journal bearing would seize with differential expansion due to the thermal inertia of the rotor being much less than that of the stator. We are talking here of nanometer clearances.

Sandia have used low-pressure steam as motive force but never gases >1000°C.

I believe this to belong to the "pious wish" category at this stage.

[Dr Mordrid]

Read the text: its a gas turbine. They even describe refueling it as one would a lighter. They did say the bearings were tough, but that's why they're building it and we aren't.

Also; like a modern liquid rocket with regenerative cooling the fuel is likely cooling the works as it's pre-heated for combustion.

I also find a gas pressure device hard to reconcile with this;

[Wulfman]

in theory you could also use a liquid with low vapor pressure, and just use the overpressure of the developing gas within the contained "tank" to drive the turbine, right? I'm not suggesting that is the case here (imho the article does suggest a "real" combustion process), but it would console the "fuel" part with the "battery" design - did you notice that there is no mechanism for bringing the fuel directly to the turbine?

mfg
wulfman