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Atomic MEMS Battery has 50 Year Charge
notestein writes "Working for DARPA, a couple of Cornell researchers (Amil Lal, Hui Li ) have developed a battery that uses decaying nickel-63 to drive a flexing MEMS cantilever to generate electricity. They expect a production version to produce useful energy for at least 50 years."
The electricity generated would probably be of too high a voltage and too little current, similar to static electricity.
Well that's what I think anyway. :P
Ali
Ph33r m3!!!
There's plenty of anti-nanotech freaks, though. Google "grey goo" and you'll see what I mean.
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One detail conveniently left out of the article is how much actual *power* is generated by this device. If a 1cc device produces only 10mA sustained, you're far better off with standard batteries for most anything except devices that actually *require* a long-running power source, and don't draw any significant amount of current. Consider this: I use 4 1700mAh AA cells in my digicam. They're, what, 3-4cc each? So at 10mA per MEMS device, you get only 160mA from that same volume.
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A 1-kilogram chunk of Nickel 63 will give off about 25 Watts of pure beta radiation -- assuming that you configure it in such a way that the beta particles aren't reabsorbed by neigboring nickel atoms. Even assuming 100% efficiency, a battery capable of powering your laptop would weigh at least a few kilograms.
The quantity of energy you'd get would be less than the energy of a decaying isotope, which is not very much. Even with advances in technology, this can't be very much.
Actually, this turns out not to be the case.
Consulting Ye Rubber Bible, Nickel-63 liberates about 67 KeV per decay (quite low; decays are typically in the 1 MeV range). This gives an energy density of about 35 kW/hr per _gram_ over the lifetime of the battery. _Energy_ density is far higher than anything based on chemical reactions.
It's _power_ density that's low for most practical battery materials. With a half-life of 92 years, you get about 20 mW per gram released (actually a bit more than that at first; it _averages_ to this as it emits half its decay energy over the whole 92 years).
The nice thing about Nickel-63 is that the decay produces beta rays (high-energy electrons) and nothing else. This could be shielded by a thick sheet of plywood, or a thin sheet of lead. Most radioisotopes aren't nearly as friendly (there is usually gamma emission as the decay product sheds excess energy, which is difficult to shield against). [ObDisclaimer: I'm assuming that the lead also blocks the x-rays produced as the high-energy electrons smack into the shielding.]
The other nice thing is that the decay product is stable and is a solid (Copper), and so both inert and likely to stay in the battery. Carbon-14, the other "friendly" radioisotope that I can think of offhand, has a lower power density (though a higher energy density), and produces a gas as a byproduct (Nitrogen), which could eventually cause problems if allowd to build up near your MEMS devices.
(Doesn't Voyager and all other longterm probes to the outer solar system use beta emitter batteries?)
No.
Radioisotope Thermoelectric Generators (RTG's)
Three RTG's provide electric power to Voyager. The generators produce about 1800 watts of heat by the radioactive decay of plutonium. The heat is then converted to about 400 watts of electric power by thermocouplers. The RTG's are mounted on a boom to protect the scientific instruments from excess heat and radioactivity.
I see too many issues for commercial mass production:
1. Product timelife too long: consumer market requires frequent product renewal. Excessively long lasting products saturate and stifle market growth.
2. Waste disposal: one of the most expensive and not yet completely accounted for voice in economic balances. The security requirements on such waste would impose prohibitive costs on it (I guess).
3. Accidental environmental release:no one wants to get this stuff implanted in their lungs! So how can accidental/intentional product destruction be dealt with? Say a 1 Kg battery is destroyed in a fire, can we secure the radioactive plume? (guess what... no!) Depleted U was said to be safe yet there are cases of blood tumor amongst mil operators and civilians exposed to the waste developed malformations (Iraq).
I don't think/hope this material will ever get mainstream. In certain scientific apps like sat it can be a good solution (or even an alternative: solar panels degrade quickly because of micrometeor collisions and ion implantation) or efficient deep space probes.
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...is apparently what Americans had in the 1950s and 60s. Many projects sought to use atomic energy directly to power everyday items. A nuclear powered airplane was partially constructed but far too heavy to leave the ground. Also prototyped were a nuclear powered Bulova wristwatch, thermal underwear for diving impregnated with plutonium, and -- I am not making this up -- a nuclear powered coffee maker that would percolate for a century under its own power. Read article for all the details.