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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."
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.
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?
"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
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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
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.
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.