| Nuclear batteries! | | Date Created: Sep 02, 2004, 03:22 PM |
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| Just opened my issue of IEEE Spectrum, the professional magazine for electrical engineers. (See online version at http://www.spectrum.ieee.org/.) I found two articles inside: one on cold fusion (really) and the second on nuclear batteries. Both articles deserve at least some discussion in our class, but my reaction to the two articles were very, very different. Cold fusion often makes me cringe (and I have many interesting stories about my casual investigations into this and related phenomenon). As an addicted laptop and cell-phone user, the possibility of nuclear batteries was tremendously exciting. |
| The fundamental point of the articles is that the energy density that can be stored in the nucleus is so very much larger than can be possibly stored chemically in an equivalent weight of molecules and atoms. In nuclear power plants, the rate of energy release due to fission or fusion nuclear reactions is controlled and is large. In nuclear batteries, energy is released during the natural decay of radioactive materials. The energy release needs no control (other than through the selection of the material) and is generally very slow. |
| The authors describe an ingenious nuclear micro-generator that uses a beta-emitter to charge a MEMS cantilever connected to a piezoelectric crystal. Alternately charging and discharging the cantilever beam performs work on the piezoelectric crystal and generates power. A few microcuries of tritium provides an energy equivalent of 2400 Li-ion batteries of the same weight. Of course, energy density is just part of the picture. How much tritium would be required to provide the continuous power for my laptop (that has a 50 Watt-hour Li-ion battery that runs for 4 hours in normal use)? The answer from the article is: the needed 150 grams of chemical energy storage for the Li-ion battery can be replaced by 0.06 grams of tritium plus the mass of the MEMS devices needed for energy conversion.) |
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