Heat Engines Shrunk By Seven Orders of Magnitude

KentuckyFC writes "The vast majority of motors that power our planes, trains, and automobiles are heat engines. They rely on the rapid expansion of gas as it heats up to generate movement. But attempts to shrink them by any significant amount have mostly ended in failure. Today, the smallest heat engines have a volume of some 10^7 cubic micrometers. Now group of Dutch engineers has built a heat engine that is seven orders of magnitude smaller than this. The engine consists of a piezoelectric bar that expands and contracts in the normal piezoelectric way. However it also heats up and cools at the same time causing a thermal expansion and contraction, which lags the piezoelectric displacement. By carefully choosing the frequency of the driving AC current, the Dutch team found a resonant effect in which the thermal expansion and contraction amplifies the mechanical motion, making it a true heat engine. Operating the thermodynamic cycle in reverse turns the device into a heat pump or refrigerator. The total volume of the device is just 0.5 cubic micrometres."

Comments

what about my car...

[Azmodan]

Great, let's make this 500 times bigger and power my car!

Re:what about my car...

[Parlett316]

Yeah a Beowulf cluster of them

what is a cubic micrometer

[Anonymous Coward]

Can the physics gurus please put cubic micrometers in perspective for us common mortals? Is that as big as a grain of rice or a head of a pin?
10^7 micrometers is.... a spehrical cow? a toaster?

Re:what is a cubic micrometer

[IndustrialComplex]

Yes, someone explain how many of them would fit into the library of congress.

A metric assload.

Re:what is a cubic micrometer

[iapetus]

That's no help - most Slashdotters are American. What's that in imperial assloads?

Re:what is a cubic micrometer

[Thud457]

WRONG!

Library of Congresses are a perfectly cromulent unit of volume. Just because the necessary measurements to derive the value are not easily google-able doesn't invalidate that fact.

In the past, when deriving the conversion from Library of Congresses to BTU's, we've used the assumption that we're talking about the books that make up the Library of Congress, not the building itself. This is because, back in the mists of time, Library of Congresses were originally used as a measure of information in the collection of the Library of Congress.

Anyhow, as a back-of-the-envelope estimate, 29 million books at 1" x 10" x 8" gives us a value of ~50,000 cubic yards. That gives us a value of ((10^7) (cubic micrometers)) / (50 000 (cubic yards)) = 2.61590124 × 10-16 Library of Congresses.

Screw this "metric system" with it's plethora of different units for different quantities. I strongly endorse that everybody normalize on Library of Congresses for units of any quantity. Just imagine how it would simplify your life!

Re:what is a cubic micrometer

[RobVB]

It would be great if commercials were like this:

This car will drive 437 milliLibraries of Congress per nanoLibrary of Congress of gasoline! And with the low carbon emissions of just 4.3 picoLibraries of Congress of CO2 per microLibrary of Congress driven, it's great for the environment!

Did someone say pump?

[Anonymous Coward]

Can it be used for other things?

Beer cans?

[courteaudotbiz]

How many beer cans fit in a 0.5 micrometers refrigerator?

Re:Beer cans?

[AaxelB]

How many beer cans fit in a 0.5 micrometers refrigerator?

Depends. Are we talking micro- or macrobrews?

Re:Beer cans?

[Red Flayer]

How many beer cans fit in a 0.5 micrometers refrigerator?

You're thinking too small.

The correct question is, how many beer kegs fit in a 0.5 micrometer fridge?

Re:Beer cans?

[krnpimpsta]

You're thinking too small.

The correct question is, how many beer kegs fit in a 0.5 micrometer fridge?

0.00000000000000000852167911 beer kegs

If the fridge interior happens to be shaped optimally so that no space is wasted and the entire 0.5 micrometer fridge is filled with keg, then.. exactly 8.52167911 * 10^-18 beer kegs (if each keg is 15.5 gallons). [Incase someone wants to out-pedant me: Yeah, I understand you can't optimally shape a 0.5 micrometer fridge for a keg, when the size of 1 unit of keg > 0.5 micrometer fridge.]

Citation: http://www.google.com/search?hl=en&q=(0.5+micrometers%5E3)%2F(1+keg)&aq=f&aql=&aqi=&oq=

Re:Usefulness?

[Dunbal]

It is so small that it produces a very minimal amount of horsepower, which is not useful for any actual way.

      Unless of course you have several billion of them on a gram sized object. If you can't see the value in jet powered ants you should turn in your nerd card.

Re:Another way to save gas

[mcgrew]

If the heat were produced externally it would be a sort of Stirling engine. So I guess one this size would be Sterling sliver.

Re:Heat engine != internal combustion engine

[Rogerborg]

why emphasize that it is a heat engine?

Probably just trying to get some free publicity when California bans it.

Re:Usefulness?

[Qzukk]

How much of a temperature difference do you think you can find within the human body across a machine of a few micormeters (or even millimeters) in length?

That's what the 12" heat sink sticking out of your chest is for. That, and impressing the ladies.