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

Clean Power Plants?

[Whiney Mac Fanboy]

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."

WTF? Where's the hydrogen coming from? May as well say In the more distant future huge arrays of kitten engines could even be the basis for clean, quiet and cost effective power plants."

Well, it could be!

Re:Clean Power Plants?

[Max Littlemore]

The hydrogen comes from the kittens, doofus!

Re:Clean Power Plants?

[TropicalCoder]

Even a thousand whispers can get pretty loud

I beg to differ. Wikipedia lists the sound pressure level of a whisper at 20 dBs. To calculate the sound of a thousand people whispering, we need to do 20 times log10(ratio). The ratio is 1000 whispers to one. log10 of 1000 is 3, so the SPL level of a thousand people whispering is only 3 time 20, or 60 dBs.

However, though wikipedia does not state at what distance the SPL level of a whisper was measured, usually we would imagine that it would be a person standing right next to us, or certainly within a meter. Clearly you cannot have a thousand people standing right next to you. Even within a meter of you, considering perhaps two people per square meter including yourself, within a circle of a one meter radius you have only about 3 square meters - room for 5 people besides yourself at the centre. To accommodate a thousand people, you would need a circle with a radius of over twelve meters. Most of those people are going to be at least 6 meters away from you. Wikipedia says "Note that the SPL emitted by an object changes with distance d from the object with 1/d.", so that implies that well over half of these people only contribute a fraction of their potential to the total sound level.

Beyond that, we have all these whispers generating an incoherent pattern of sound waves, sometimes reinforcing each other, and sometimes cancelling each other out, such that by the time this reaches your ears it has only a fraction of the energy that it would posses if everybody whispered in absolutely perfect unison, offset by their distance from you. In the end, the total SPL level is beyond my capability to calculate, but I would just guess that on a practical level it would not reach the level of a normal conversation between two people.

Now, if you want to hear something loud, consider the sound of a thousand hands clapping. Going by the previous example, it is easy to calculate. We begin with an estimate of the sound pressure level of one hand clapping... Oh oh...

Dare I say it? A cluster?..

[mi]

In the more distant future huge arrays of hydrogen fueled millimeter turbine engines

Imagine a, oh, whatever, cluster of these!..

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?

First practial use?

[TinBromide]

Who's willing to bet that within a week of these things becoming operational, they're put to use by some MIT nerds making a portable air hockey set?

What about our small neighbors?

[Loopy]

This is all well and good but what about all the little bugs that will get shredded in those little turbines? Are they going to paste millimeter-size warning signs? I think it's the least we could do for our tiny houseguests.

Moo

[Chacham]

Millimeter Turbins? Must be for really small Muslims.

Re:Moo

[philip_bailey]

Millimeter Turbins? Must be for really small Muslims.

Turbans are worn by Sikhs, not Muslims.

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...

Re:Yep...

[CrazyJim1]

Go put your fingers on a 100-watt lightbulb to get an idea of how much heat we're talking about... Ouch, you insensitive clod.

Re:Yep...

[tftp]

No, it means that you need to turn it on first.

Re:Seriously?!?!

[lendude]

Your humour well has run dry - commence drilling elsewhere.

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

Re:Wow, really?!?

[fireboy1919]

Yeah. Really silly, huh?

But, just for fun (since I can't remember), which law of thermodynamics does the production of power violate?

I'm looking at 'em, but I can't find a law of conservation of power. I'm sure that's the one you meant, though, right.

Hmm... I guess I'm going to have to walk to work tomorrow. My car is currently sitting in the driveway producing no power (since none of it's components are doing any work at all), and thanks to xaxxon's newly discovered law of conservation of power, that means it isn't going to be producing power in the future, since it's previous means of doing so was by using stored energy rather than any form of power.

Incidentally, I think I'm going to have to cut this post short. I imagine it's not going to be too long before somebody realizes that computers have nonconstant power systems and it stops working. I just pray nobody gets around to doing the same to all life on this planet.