By Roland Piquepaille
According to this news release from the National Science Foundation (NSF), American researchers have developed a porous-silicon diode that "convert low levels of radiation into electricity and can have useful lives spanning several decades." The new 'BetaBattery' is more efficient than conventional chemical batteries and potentially cheap to manufacture. It uses a radioactive source as its fuel, the tritium, an hydrogen isotope. When the tritium releases electrons in a process called beta decay, the 'BetaBattery' generates electricity by absorbing these electrons. So far, the 'BetaBattery' doesn't deliver as much power as chemical batteries, but it could be extremely useful to power devices which have a long life and are difficult to service, such as structural sensors in bridges and satellites. Read more...Here is the description of the 'BetaBattery' concept.
Using some of the same manufacturing techniques that produce microchips, researchers have created a porous-silicon diode that may lead to improved betavoltaics. Such devices convert low levels of radiation into electricity and can have useful lives spanning several decades.
While producing as little as one-thousandth of the power of conventional chemical batteries, the new "BetaBattery" concept is more efficient and potentially less expensive than similar designs and should be easier to manufacture.
The battery's staying power is tied to the enduring nature of its fuel, tritium, a hydrogen isotope that releases electrons in a process called beta decay. The porous-silicon semiconductors generate electricity by absorbing the electrons, just as a solar cell generates electricity by absorbing energy from incoming photons of light.
This is not the first time that a radioactive element or even the tritium is used. The real difference of this new device is not its source.
The new cell will have a unique advantage -- the half-millimeter-thick silicon wafer into which researchers have etched a network of deep pores. This structure vastly increases the exposed surface area, creating a device that is 10 times more efficient than planar designs.
On the photo below, "Wei Sun of the University of Rochester holds the wafer test fixture the researchers used to test the new porous-silicon diode and its interactions with tritium gas. The diode is the dark wafer in the center of the top plate." (Credit: University of Rochester; BetaBatt, Inc.)
You can see a larger version of this picture and other images on this page at NSF.
And what will be some applications for these future batteries?
"The initial applications will be for remote or inaccessible sensors and devices where the availability of long-life power is critical," says Larry Gadeken of BetaBatt, [the only commercial entity involved in this research].
If the new diode proves successful when incorporated into a finished battery, it could help power such hard-to-service, long-life systems as structural sensors on bridges, climate monitoring equipment and satellites.
If you're interested by the subject, the research work has been published by Advanced Materials on May 3, 2005 (Volume 17, Issue 10, Pages 1230-1233), under the name "A Three-Dimensional Porous Silicon p-n Diode for Betavoltaics and Photovoltaics." Here is a link to the paper if you're a registered user (there is no abstract).
And please note that BetaBatt, from Houston, is already selling "a quarter size battery with a 12-20 year lifespan and mission critical reliability" based on its patent number 6,774,531 which carries the name "Apparatus and method for generating electrical current from the nuclear decay process of a radioactive material."
Sources: National Science Foundation news release, May 10, 2005; and various websites
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