4 ms·

What's the actual energy output on those? I know nothing about the physics, but from this picture (https://citylabs.net/nanotritium-betavoltaic-p200-series-pac

What's the actual energy output on those? I know nothing about the physics, but from this picture (https://citylabs.net/nanotritium-betavoltaic-p200-series-package-specifications/ https://citylabs.net/nanotritium-betavoltaic-p200-series-pac...), they get 100uW from 100Ci. Assuming the glow phosphors are 25 times more efficient than their conversion process(Google says 4% for beta batteries as the first result I can find) that's 625uW of light energy. I would imagine the phosphor is not 100% efficient so it's probably less. Assuming 20% efficiency for a green LED, that's 3.125mW of electrical input to replace it with an LED. Are they really that dim??? Over 15 years, that's around 200-400Wh of electricity one would need. I wonder what's better for the environment, the tritium or the batteries one could probably use instead for similar cost, since those signs seem to be $300. I suppose the tritium is not an issue on the production side because it's a byproduct? Unless the processing has nasty effects?

xkcd-sucks 3y ago
eh, tritium and its decay products float off into space unless incorporated into a heavier molecule (e.g. burning concentrated tritium into water). even then hydrogens are usually pretty labile and don't bioaccumulate unlike e.g. calcium/strontium/phosphorous. so the risk of exposure is negligible except maybe in manufacturing, and the risk of environmental accumulation is also negligible. with tritium/phosphor, the brightness is super dim but more than sufficient in actual darkness. it's simple, stable under extreme environmental conditions, and there's nothing microscopic or macroscopic to break besides the containment vessel itself. it lasts for decades and fails by dimming gradually (unless the containment vessel is broken at least). not sure about exit sign construction but the little bitty capsule form factor is quite resilient.. by contrast LEDs and electronics in general seem to be less tolerant of challenges (i.e. side reactions in the battery over 10 years at elevated temperature, it gets zapped by an electrical arc etc). also the manufacturing is just as nasty and the stuff is less likely to just float off into space

xkcd-sucks 3y ago

eh, tritium and its decay products float off into space unless incorporated into a heavier molecule (e.g. burning concentrated tritium into water). even then hydrogens are usually pretty labile and don't bioaccumulate unlike e.g. calcium/strontium/phosphorous. so the risk of exposure is negligible except maybe in manufacturing, and the risk of environmental accumulation is also negligible. with tritium/phosphor, the brightness is super dim but more than sufficient in actual darkness. it's simple, stable under extreme environmental conditions, and there's nothing microscopic or macroscopic to break besides the containment vessel itself. it lasts for decades and fails by dimming gradually (unless the containment vessel is broken at least). not sure about exit sign construction but the little bitty capsule form factor is quite resilient.. by contrast LEDs and electronics in general seem to be less tolerant of challenges (i.e. side reactions in the battery over 10 years at elevated temperature, it gets zapped by an electrical arc etc). also the manufacturing is just as nasty and the stuff is less likely to just float off into space