MIT's Millimeter Turbine to be Ready This Year

Iddo Genuth writes "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."

Comments

Huge arrays?

[Hektor_Troy]

Doesn't turbines get more efficient as they grow in size? I mean, it's not like you'll see power plants use hundreds of tiny steam turbines - they use a few huge ones.

Or am I missing something completely fundamental about the ones MIT's made here?

Yep...

[Goonie]

This microturbine research pops up on Slashdot every year or so.

The thermal efficiency is the real killer - according to this post, the expected thermal efficency is somewhere between 3 and 8%.

That's problematic for two reasons - one, a plant made of thousands of these would use way more fuel than one using a conventional piston engine and one generator, and, two, for small-scale apps it means you end up with a massive pile of waste heat to dispose of. As somebody put it - if you want 10 watts of power, that means 100 watts of waste heat to dispose of. Go put your fingers on a 100-watt lightbulb to get an idea of how much heat we're talking about...

Something about the numbers doesn't add up...

[GameMaster]

Let me see if I get this straight:

He says that he expects the initial products to be about 500-700 Watt-Hours/kg. and to, potentially, go as high as 1200-1500 Watt-Hours/kg. in the distant future.

My understanding is that this thing is supposed to run off of Hydrogen. It'd almost have, to as many consumer electronics are run indoors and most other fuels I know about give off toxic fumes when used in combustion engines.

Hydrogen has an energy density of ~33.3 Watt-Hours/kg. ( http://hypertextbook.com/facts/2005/MichelleFung.s html/ )

Now, assuming that the weight of the turbine (~4mm square) and packaging is negligible, most of the weight is fuel. In that case, we are looking at an efficiency of 1.5% - 2.1% for the initial models and 3.6% - 4.5% for the extreme upper end of what this guy thinks is foreseeable with this technology. 1.5% - 4.5% efficiency? That's horrible! Remember, pure hydrogen doesn't exist naturally on this planet. You had to spend large amounts of energy in the first place to produce the hydrogen that will be stored in these batteries (how exactly they plan on storing it I don't know because even the best, present day, techniques leak like a sieve because of the extremely small size of the hydrogen molecule).

Don't get me wrong, I can see where people would want something like this. The potential energy density compared to the compact form factor would open up new possibilities for portable equipment. There in lies the problem. The instant gratification of this technology will be almost impossible to fight. If every piece of small electronics had this kind of power source, cell phones, PDAs, laptops, etc. would become leaps-and-bounds more powerful and, at the same time, would be consuming energy at, potential, an exponentially higher rate.

The only way I can see this not becoming ubiquitous is if some other technology, like batteries, beats it to that energy density level. I don't think that's likely to happen because, even at these miserable efficiency rates, liquid fuels still have a massive lead in energy density over even the most promising, potential, battery technology known.

I hope there is an error in my math. Another possibility is that, as is so often the case, the author of the article doesn't have a clue of what he's talking about and had warped the facts of the story. The fact that he has suggested the possibility of replacing full-sized power plants with massive arrays of these turbines gives me hope that that's the case. If any of you have a correction for my math, please let me know.

-GameMaster