The idea of micropower is a neat one, sure enough. We've been told that rooftop generators, using wind power or natural gas-fed fuel cells, will enable their owners to at the very least cut their electrical bills, and possibly even make money by selling current to the local grid. I have a feeling this technology will become feasible for institutional properties or large apartment houses within the next few years; homes, maybe not, because the fuel cell in question is the size of a truck trailer, and most home roofs aren't strong enough to securely hold such a large and heavy object.
But really, maybe I should be calling this stuff nanopower. Micropower is replacing your share of output from a power station that takes up many acres with a large generator that is the size of a truck; as micropower to regular power, so nanopower to micropower. I'm talking about replacements for batteries.
The problem with batteries is that they tend to be fairly large and heavy, compared to the amount of energy they store. Yeah, there are some technological solutions being explored in making batteries better. But hey, other solutions already exist.
One of them is, parallel to the development of the truck-sized fuel cell, a handheld fuel cell that runs on methanol. Samsung, for example, has such a device. It's a little slate sort of thing, and it's got a port in the side where you can slip in the little fuel tanks. I seem to recall reading that the designers believe each of their fuel tanks contains the equivalent of twenty fully-charged lithium-ion batteries. A larger unit, the size of a laptop, could power... well, it might power a laptop, or act as a power hub to charge several smaller devices. (Laptops might pull sixty watts at the very least, when they're working; mine, back when it worked at all, pulled over a hundred. Phones probably pull less than one, when charging.)
But you can go one step better.
Fuel cells are all good and awesome and such, but if you want your portable electricity, a fuel cell might not be as efficient or useful as, say, using some combustible fuel in a miniaturized turbine engine. MIT's Microengine Project uses hydrogen instead of methanol, but the principle is the same. It sounds like a crazy idea, but you can make the components through photolithography, the same technology used to make microchips and such; an article on Wired.com quotes Luc Frechette of MIT, who suggested that the power output of such a turbine could reach 20 watts. That article, as well as Johns Hopkins machinist lab admin and engineering professor Curt Ewing, have also suggested that the size of such engines would be comparable to things like coins or shirt buttons - not all that big. Heat dissipation is, of course, a problem; but at speeds of two million RPM or above, the problem of noise will be reduced by the inaudibly high pitch of operating noise. (No idea what the sound pressure might be like, though.) Due to the heat issue - and the fact that the engine exhaust has to go somewhere - Frechette suggested that a micro-turbine generator would probably not be a part of any appliance, but rather would be a stand-alone device connecting to other hardware by a nice, long wire.
I do have a solution, though, borrowed from the steam-powered prosthetic limb developed at Vanderbilt University. To quote:
The hot steam exhaust was also a problem, which they decided to handle in as natural a fashion as possible: by venting it through a porous cover, where it condenses and turns into water droplets. "The amount of water involved is about the same as a person would normally sweat from their arm in a warm day," Goldfarb says.
The exhaust from a hydrogen-burning turbine, a methanol-burning turbine, or even a steam turbine powered by peroxides, could be vented through such a cover, and a clever engineering team might either figure out a way to evaporate it or to collect it for some other use - say, supplying an internal heat exchanger with a working fluid, or drinking water, or whatever.
Now, what if you don't just want electricity but want motive force also, or instead? Now that's a question I just don't know the answer to. I thought: perhaps the miniaturized turbines would allow design of something like a chainsword? (For those unfamiliar, a chainsword is a fictional sword-like weapon with a bladed chain running along its edge.) Unfortunately, to build a chainsword, you'd probably need a power source pumping out three or four kilowatts, which means 150 to 200 micro-turbines. Even with their small size, that's a lot of them; and the reduction gears needed to take 2x10^6 RPM down to the 12,000 RPM of a typical chainsaw are going to be bulky (not to mention that they'll waste a lot of the engine power as heat and noise). So we won't be seeing any chainswords any time soon - at least, none that could be wielded one-handed.
Ah well, though. That's what I get for waiting so long between MSPWs.
(Other diaries in this series include a drug contraindication database, novel prosthetics, virtual worlds, robot safety, ye short fiction, the sociology of fictional places, steam-powered giant robots, thermal depolymerization, nuclear airplanes, psychic powers, transgenic bacteria that make useful compounds, lightning in a jar, neural interfaces, powered armor, sonic weapons, rapid prototyping, putting Mentos and Diet Coke to good use, life on life support, combining farming and electrical generation, pigeon pilots, cuttlefish behind the wheel, the hafnium bomb, and building a better skunk.)