Mixed Signals
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Tuesday 2 October 2007, 12:09 PM
Radioactive laptops? Perhaps not...
Here's a story that's doing the rounds on the blogs - Scientists Invent 30 Year Continuous Power Laptop Battery.
The story is written in peculiarly convoluted prose, but appears to be saying that a breakthrough in nuclear energy technology means that we'll all be running around with magic batteries in mobile and laptop, in "two to three years". They'll be perfectly safe, will save the world, and will probably last longer than you will.
Sadly, no. As with the best techno-rubbish, there is a story in there, but you'll be pootling around the skies in jetpacks before you're powering your Dell from neutron decay.
That story is betavoltaics. This is a way of generating electricity much as solar cells generate power from photons, only by using high energy electrons generated from the beta decay of certain radio-isotopes. If you pick your isotope well -- the examples given use tritium, a radioactive form of hydrogen - the other decay products are inert, and in theory you can generate useful amounts of power for a reasonable length of time. As with every radioactive system, it has a half-life depending on the isotope; tritium's half-life is around twelve years, so every decade or so your battery will halve in power - but that won't change, no matter how little or much power you take out in the duration.
Beats Duracell, right?
Again, sadly, no. There are a few small problems.
One is that the sort of atomic structures that generate power when bombarded with high energy electrons are the sort that tend to fall apart when bombarded with high energy electrons. While solar cells have the same problem, it's to a much lesser extent. There's a lot of research into making materials that don't suffer so much, but it remains a serious issue.
Secondly, while it's true that a tritium-powered battery will eventually turn into an inert, safe lump of nothing much, and while it's also true that a modest amount of shielding will keep the radioactivity within the battery the while, there's the small problem that if you break the battery during its life the nasties come out.
Thirdly, they don't have a great conversion efficiency. Around 25 percent is the best you can get - which is pretty good, but leaves 75 percent sloshing around as heat. That means a 25 watt battery will get plenty warm.
Lastly, they're not very good batteries. Even the latest devices, which are very clever in the way they saturate a porous structure with the gas and thus usefully capture quite a large number of the energetic electrons, have an energy density of the order of twenty five watts per kilo. Lithium ion batteries, the sort you have in your laptop, manage 1.8 kilowatts per kilo. That's 72 times more bang per gram. Do you fancy carrying a battery 72 times heavier than the one you have at the moment, especially if it's hotter than a sixty watt light bulb?
Which is not to say that betavoltaics aren't useful. There are some interesting ideas for using small betavoltaic cells to constantly trickle charge more conventional batteries, which helps circumvent some of the capacity issues.
And there are plenty of places where it's difficult or dangerous to have to change or recharge the power source, and many of those only need small amounts of juice.
Those places do not currently include your lap. You may possibly be relieved to hear this.
PreviousComments on this post
I figured the story was "off" - thanks for the reality check.
Still, couldn't this principal be used on nuclear waste? In a nice Cradle to Cradle fashion, we turn the waste of the power plants into inputs to an additional power source. One that would last 20+ years. Sound cheaper/better than sending it to the depths of the Earth.
There is some science behind the claim, and it's being investigated by the University of Rochester at least. They have an article here: http://www.rochester.edu/news/show.php?id=2154 from May, 2005 about their research.
It sounds like someone just went a little crazy about the current application of the technology.
Llong - that principle has already been tried in fast breeder reactors. As a result, the UK now has an enormous stockpile -- 100 tonnes -- of plutonium and nothing to use it on. In any case, the sort of waste that you have to bury in long-term deep storage facilities is REALLY not the sort of material you want anywhere near you; it also doesn't decay to environmentally safe end products, at least not any time soon, and it tends to generate alphas and gammas, neither of which are as benign to humans as betas.
Cobes04 - there's nothing wrong with the betavoltaic principle; it's been known about for at least half a century, and as such things go it's very well understood. But for the reasons I've outlined above, as well as quite a few others, it's no good for the sort of things the original article was talking about.
I didn't do the sums for a 25 watt tritium-powered battery; someone on Slashdot did (hi, /,!) and came up with the figure that you'd need 800 grams of tritium for a 50 watt battery.
Doesn't sound much, but tritium is an isotope of hydrogen - the least dense gas in the universe.
Assuming that tritium has a density roughly equivalent to hydrogen - around 0.08 grams per litre - that means you'd need 100,000 litres of gas. Per battery.
That's what scientists call 'a lot', and 'difficult to fit into a laptop'.
Hmmmm....
Looks like a Yank already has a few patents in the battery technology.
http://www.rexresearch.com/nucell/nucell.htm#obit
And also one on how to turn the UK's mountain of Plutonium into something a bit more manageable using xrays....
Check out the pictures above the obituary of the scientist.
Seems his battery is 100,000 times more powerful than your explanation and gives off NO heat... uses magnetic fields.
Ta Ta!
Well... there's a lot that's odd about the Paul M Brown patent. A nuclear-powered self-resonant oscillator, fed by hundreds of grams of uranium and thorium, and generating nearly 10 kilowatts? Even if it works as advertised, that's going to be one dangerous machine to be anywhere near.
And the photodisintegration idea is, as far as I know, well known and very annoyingly utterly impracticable.
Comparing the 1800 W of the Li-ion battery with the 25 W of this battery is wrong. A laptop need less than 25 W to operate, therefore 1 kg of this battery will do. A Li-ion battery only has about 52 Wh of energy while this battery has an "endless" amount of energy. And therefore 1 kg of battery can supply 25 W during an infinite time. A Li-ion battery can supply the 1800 W only for seconds or 25 W for about 2 hours.
Another good point fv000...
Lith-Ion batteries need to be as large and heavy as they are because they "run down". A Lith-Ion battery that provided 25W of power could be made very small but would have a VERY short operating time before needing to be recharged. Many manufacturers offer "Extended" Batteries that provide 50-100% more operating time...and are 50-100% larger and heavier.
Laptops do indeed need only about 25W max of power to operate...
http://www.codinghorror.com/blog/archives/000562.html
http://michaelbluejay.com/electricity/computers.html
But can use much more...up to around 120W.
Breakthroughs in processor and hard drive technology are improving this dramatically...Laptops as a whole are becoming very efficient...so the idea of a laptop that consumer less than 25W of power is not unreasonable...in fact...there are some that are here now...
IE compare a new SSD Hard Drive to a traditional drive...there are SIGNIFICANT differences in power consumption. Not to mention advantages in weight, etc.
Other methods of reducing power on a laptop include reducing the screen size from the (relatively) massive 17" screens to something smaller say a 14 or 13.1" screen...which could represent a savings of approx 25-30 in power consumption.
Tritium has been used for years in other applications...Remember your glowing Swatch Watch?
http://www.physics.isu.edu/radinf/tritium.htm
The one thing I am not certain about is the battery size due to the density of the Tritium. But even at 800 grams or approx 1.76lbs...
Say for arguments sake that the battery must be 2kg or 4.4lbs.
Even given the significant weight increase for the battery...would some people be willing to sacrifice the weight for not having to plug in and charge up?
I'm sure someone will market at sell this...
It's too early to summarily dismiss this as being fanciful and farfetched.
I've got a torch with tritium glowtubes embedded in it, and very useful they are too. However, the amount of energy they produce is vanishingly small.
A tritium betavoltaic battery capable of powering a laptop, even in a hybrid form with some more mainstream secondary technology, is not practicable. Even if it could be made small (which it cant'), light (which it can't) and totally safe (which it can't), it would still be continually pushing out three times as much heat as electricity. Just think about the implications of that...
I think these could be great for the environment if they were developed further but from what i've read so far I just cant see these making it to the shelves, not at an affordable price anyway and surely if they generate as much heat as people say then they probably aren't safe. My laptop battery gets extremely hot after a relatively short time so i dread to think the heat these will produce!
Claire.
AKA:Spirulina Girl
At beginning of reading this article, it sounds interesting to me. Having thought it over, I feel it could not be a practical and commericalizable solution. What about safety? what if children misuse it somehow? Nowadays many people have laptops, how many of them have enough knowledge about its battery, its working mechanism? I have already heard several cases in which Dell or Sony laptop caught files due to battery problems. I even saw such pictures. I am more concerned with safety than the long-lasting feature. However, I think this article present a useful thinking. As llong pointed out, we might apply the thoughts into the nuclear waste processing. Good article anyway!
Frank, the Health Lover
its very ineresting,I want to have a the best technology for laptop battery,I think these could be great for the environment if they were developed further too.
