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Jet Engine on a Chip
Roland Piquepaille writes "Today, our handheld devices are powered by batteries, which are heavy and inconvenient. Fuel cells are just arriving on the market as a replacement. But there is a new contender: micro gas turbine engines under development at the MIT. Engineers there shrunk jet engines to the size of a coat button. And their blades which span an area smaller than a dime can spin a million times per minute and produce enough electricity to power your PDA or your cell phone. While there are still a few hurdles to overcome, these micro turbine engines should be operational in two or three years, with commercial products available four years from now. These micro jet engines also have the potential to free soldiers or travelers from carrying heavy batteries. The engineers even think their engines on a chip could be used in poor countries to bring electricity there. This summary gives you the essential details about a technology which promises to free us to carry extra fuel instead of batteries."
...to increase our reliance on petroleum.
What about the noise created? Last time I was near a jet engine, it made quite a racket...
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How many years now have we been hearing about miniature turbine power sources? Too many. Just because some kids at MIT did it doesn't mean it's even close to being commercially viable, and even if it is viable doesn't mean anybody will adopt it. That aside, I do think it's a great concept and I hope it DOES eventually get adopted, especially if they can make the turbines run on vegetable oil :)
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If the fuel is a clean hydrocarbon, the exhaust will be CO2 and H2O. Using batteries pollutes too, you just don't see it right there because it's either at the power plant where your battery charger got it's energy from, or it's in the chemical pollution of used dead batteries, or both.
"a technology which promises to free us to carry extra fuel instead of batteries"
That's just what we need, more dependence on combustable fuel. Besides that I feel MUCH safer carrying around extra batteries then a highly explosive fuel.
I'd bet it is neglectible compared to the pollution caused by regular alkaline batteries that end up in the dumpyard.
At most the pollutants would be CO2 and some other carbon based compounds.
TSA Drone: "What do you have in that bottle?"
You: "Oh, it's just some gasoline for my laptop."
Sure...this technology will be a GREAT laptop power source for travelers...
This matters a lot, because small turbines suffer much more from viscous flow losses and heat-transfer losses than large ones. If a 50 W microturbine is 10% efficient, its waste heat will amount to 450 watts; if it is 5% efficient, the waste heat will be 950 watts! This could easily lead to them being banned from commercial aircraft, because the extra heat load and oxygen consumption would drive A/C loading too high (not to mention the discomfort of adjacent passengers).
Sustainability and energy independence essay
Compare with traditional rechargable batteries.
First, there is the one-time environmental cost of manufacturing the batteries. Making a battery requires fuel for mining equipment, transporting the materials, running the manufacturing equipment, and producing the electrolyte.
Second, there is the energy required to charge the battery. This energy comes from the power grid. Ultimately, it comes from burning fossil fuels in power plants. This energy must be transmitted via wires to an electrical outlet, turned into DC by a rectifier, and finally, used to charge the battery.
In other words, here's the energy path for the turbine:
Fossil fuel ---> Combustion ---> Turn turbine ---> Generate DC power
And for the rechargable batteries:
Fossil fuel ---> Combustion ---> Turn turbine ---> Generate AC current ---> Transform to high voltage ---> Transmit down wires ---> Transform back to low voltage ---> Rectify to DC power
Which do you think is more efficient?
Well, your cell phone only needs about a watt, a PDA about 2-10 watts, and your laptop about 20-100 watts. If you consider that cars produce kilowatts of constant power output, you should realize that the amount of exhaust shouldn't be anywhere close to what your car puts out.
Which is quite good, as they don't let you run your car on a plane. But using your numbers, 20 or so people using laptops on a plane would be the same as someone running a car in the passenger cabin. That's not good.
"Each disposable cartridge would pack as much energy as a few heavy handfuls of lithium-ion batteries."
We don't really want to carry larger and larger packages of energy on our person. As it is, we are seeing accidents like this one due to today's ordinary lithium-ion batteries. And I recently got a recall notice from Verizon about the kind of batteries used in my cell phone, so this isn't an isolated incident.
When someone tosses a 9V battery in their pocket and it gets shorted out by a coin, they are startled, yell, and pick the hot coin out of their pocket.
When a cell phone battery acts up, Shelley Kaehr got a handful of battery acid and set fire to the floor.
Multiply that by "a few heavy handfuls" and you start to get the possibility of really serious personal injury.
What we need are breakthroughs on the power consumption side, not ever-increasing power supplies
"How to Do Nothing," kids activities, back in print!
take a deep breath and blow on it.
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The primary difference is energy density. As fuels go, petroleum is the the most energy dense fuel short of nuclear. While there are attempts to find even denser fuels, none of the alternatives that have been investigated are stable enough or safe enough for use.
Javascript + Nintendo DSi = DSiCade
Can we please stop posting directly to stories on this guy's weblog? It's embarassing for Slashdot. The real news link you're looking for is:
here
Why not use a small tank of compressed gas (i.e., nitrogen) to drive the turbine? For small portable power, the inefficiency inherent in compressing the gas in the first place isn't that big of a deal.
-- "Makes Little Debbie look like a pile of puke!" - Moe Szyslak
Cept where did the energy come from to charge that 80% efficient battery? From your local gas turbine powerplant, which once you factor in the efficiency loss of the grid, will come out to much lower efficiency than your hand held gas turbine.
For as much as I love Slashdot, there exists little recourse for people who want their input on the site to be heard, even when its on as large a scale as the current hatred of Roland posts.
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Well, IAAEE (I am an electrical engineer) and I'm gunna have to say that the turbine is going to have to transform its output voltage somehow anyway. Not that transformers deplete much power at all, but still, it is almost certainly more efficient to use a transformer after the turbine than screwing with the turbine to produce different voltage / frequencies. Also, the tiny turbine is going to have to rectify to dc power also. AC power is the "natural" form of electricity produced by power plants. It always requires an extra step to get dc. Finally, there is an economy of scale involved. A small turbine is simply not going to be as efficient as a large one. I would expect one that small to be nowhere near as efficient as a power plant. I would expect that the difference in efficiency of turbines would more than equal out the benefit of avoiding transformation (which is a very efficient process, for good transformers at least).
The important question is actually, which one weighs more? Which one is cheaper to use? Seriously, who cares about the environmental effects. We have millions and millions of big engines in the form of cars, a few hundred thousand small gas turbines aren't going to matter much.
I submitted this story last night, and it didn't get posted.
Wow, what a tool. This guy has about 4 sentences of content on his blog and the rest is copied verbatim from the original article. That's pretty embarassing that Slashdot is potentially providing this guy with revenue.
Random is the New Order.
That's a good point. Hydrogen embrittlement is a serious issue with rocket engine design. I hadn't considered that it would be an issue with fuel cells. That may be why many laptop cells utilize methanol as a hydrogen storage medium.
Javascript + Nintendo DSi = DSiCade
Roland generally posts a link to an (interesting) article on a technology site and then paraphrases it under the guise of a 'useful summary'. He offers zero insight and could instead just submit the original article without his unnecessary boring commentary. It is filtered and it is bullshit.
KARMA TAG! You're it.
It takes energy to transport materials, ya know.
Candy-Coated Knowledge
Rubbish. It's because he submits articles linking to his blog, which essentially contains a summary of and a link to the real article, and yet slashdot sees fit to post lots of them.
He's driving traffic to his blog to increase ad revenue and his reputation (he's now working as a professional blogging consultant), and slashdot are helping big-time. If there's money changing hands, or it's a favour for a friend, then fine - but the slashdot guys really ought to tell us.
It's official. Most of you are morons.
But in this case Wikipedia is actually correct. Don't fall victim to logical fallacies, just because one entry isn't correct doesn't mean that ALL their entries are incorrect.
Gas turbines are inefficient by design, because they use combustion to produce power, and the combustion process is inherently inefficient from an energy transfer point-of-view.
I'm an environmental econ major, and we talk extensively about fossil fuels and alternative energy sources. The size doesn't matter... you're dealing with the 1st and 2nd laws of thermodynamics here, you get a little energy and a LOT of heat. Unless the mini turbines have somehow figured out how to turn all that excessive heat from the combusted fuel into energy they're gonna suffer the same problems of their larger brethren.
The only way to make gas turbines more efficient is to pump the excess heat from the exhaust into a steam turbine and gain a bit more bang for your buck... but I doubt we'll see any miracle breakthrough's on the combustion front, even though these mini turbines are intriguing.
Combined cycle generation overcomes these limits by using water as a working fluid for the gas turbine's "waste heat". Water is much easier to compress, you just condense it and run it through a pump. The condenser makes a vacuum, which further adds to cycle efficiency. Steam turbines can expand steam all the way down to vacuum pressures and nearly ambient temperature.
The working fluid, air, in a micro turbine is going to behave in a more compressible fashion than it will in a big turbine. It should be easier to compress and suffer fewer losses due to turbulence. This will partially be offset by increased viscous losses to walls and pipes, but those can be kept low with short paths.
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If you open up any copy of Encyclopædia Britannica you'll easily find articles you consider to be "biased." This is inevitable; Britannica is written by humans, and one man's "bias" is another man's absolute fact. No man willingly writes bias against his own judgment.
In the case of Wikipedia, it is not whether bias exists that matters. It is impossible to remove bias from human-made media. What matters is how that bias compares to those of other comparable media.
Well, IWAEE (I WAS an eletrical engineer), and I seem to remember that in the battle between AC and DC (between Tesla and Edison) for the power generators AC won not by being more efficient to produce, but by being more efficient to transport.
The DC generators do exist. Edison was proposing them, but the problem was that the losses in the Cu were forcing you to have the devices using the current close to the generator. Tesla solved that problem with AC. The existing DC generators could not be converted to AC (you cannot make a nice sine from a DC current of that power), so there you got AC generators.
Since most of the power generation happens far from the user, most of the power is generated by AC generators. However, if the distance is not the limit (as in cars, or here where you would power a laptop or some such) DC generators are an option.
However, you were correct about the efficiency of the small vs. large turbines.