The Atomic Battery  

This is only tangentially energy related (not that this has stopped you before, I hear regular readers muttering), but I thought Tech Review's article on batteries powered by low level atomic radiation quite interesting.

The advantage of these batteries is that they last basically forever, so they are handy in situations where it is difficult to change batteries once a device has been released into the wild. This is possibly more energy efficient than regularly replacing more common types of battery or even rechargeables for that matter. So perhaps would be post oil crash survivalists should consider stocking up if they hit the market in time.

Betavoltaic devices use radioisotopes that emit relatively harmless beta particles, rather than more dangerous gamma photons. They've actually been tested in labs for 50 years -- but they generate so little power that a larger commercial role for them has yet to be found. So far, tritium-powered betavoltaics, which require minimal shielding and are unable to penetrate human skin, have been used to light exit signs and glow-in-the-dark watches. A commercial version of the DEC Cell will likely not have enough juice to power a cell phone -- but plenty for a sensor or pacemaker.

The key to making the DEC Cell more viable is increasing the efficiency with which it creates power. In the past, betavoltaics researchers have used a design similar to a solar cell: a flat wafer is coated with a diode material that creates electric current when bombarded by emitted electrons. However, all but the electron particles that shoot down toward the diodes are lost in that design, says University of Rochester professor of electrical and computer engineering Phillipe Fauchet, who developed the more-efficient design based on Gadeken's concept.

The solution was to expose more of the reactive surface to the particles by creating a porous silicon diode wafer sprinkled with one-micron wide, 40 micron-deep pits. When the radioactive gas occupies these pits, it creates the maximum opportunity for harnessing the reaction.

As importantly, the process is easily reproducible and cheap, says Fauchet -- a necessity if the DEC Cell is to be commercially viable.

The fabrication techniques may be affordable, but the tritium itself -- a byproduct of nuclear power production -- is still more expensive than the lithium in your cell-phone battery. The cost is less of an issue, however, for devices designed specifically to collect hard-to-get data.