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Wednesday, 19 November 2014


Another way to look at it is that batteries have very low energy density.

Yup. I worked on a feasibility study, back in the 90s (when chips took more power, and batteries were about the same as they are now) for a system of wirelessly-updated supermarket shelf tags. Had to run on self-contained power for a few years.
Can we power it using photovoltaics and the overhead lighting?
Can we put a Tesla coil in the middle of the store?
Can we use RTGs?
Turned out a lithium coin cell was our energy budget... and, with a clever protocol for only turning on the radio at prearranged times, we could just about meet the requirement, using the ASIC technology of a Swiss company that specialized in digital watches (which, back then, people still thought were a pretty neat idea).
The follow-on project (implementation) never went anywhere, but the study was certainly educational.

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