DIY Nuclear Battery With PV Cells And Tritium

Nuclear batteries are pretty simple devices that are conceptually rather similar to photovoltaic (PV) solar, just using the radiation from a radioisotope rather than solar radiation. It’s also possible to make your own nuclear battery, with [Double M Innovations] putting together a version that uses standard PV cells combined with small tritium vials as radiation source.

The PV cells are the amorphous type, rated for 2.4 V, which means that they’re not too fussy about the exact wavelength at the cost of some general efficiency. You generally find these on solar-powered calculators for this reason. Meanwhile the tritium vials have an inner coating of phosphor so they glow. With a couple of these vials sandwiched in between two amorphous cells you thus have technically something that you could call a ‘nuclear battery’.

With an approximately 12 year half-life, tritium isn’t amazingly radioactive and thus the glow from the phosphor is also not really visible in daylight. With this DIY battery wrapped up in aluminium foil to cover it up fully, it does appear to generate some current in the nanoamp range, with a single-cell and series voltage of about 0.5 V.

A 170 VAC-rated capacitor is connected to collect some current over time, with just under 3 V measured after a night of charging. In how far the power comes from the phosphor and how much from sources like thermal radiation is hard to say in this setup. However, if you can match up the PV cell’s bandgap a bit more with the radiation source, you should be able to pull at least a few mW from a DIY nuclear battery, as seen with commercial examples.

This isn’t the first time we’ve seen this particular trick. A few years ago, a similar setup was used to power a handheld game, as long as you don’t mind waiting a few months for it to charge.

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The Thousand Year (Radioactive) Diamond Battery

The Holy Grail of battery technology is a cell which lasts forever, a fit-and-forget device that never needs replacing. It may seem a pipe-dream, but University of Bristol researchers have come pretty close. The catch? Their battery lasts a very long time, but it generates micropower, and it’s radioactive.

They’re using a thin layer of vapour-deposited carbon-14 diamond both as a source of beta radiation, and as a semiconductor material which harvests those electrons. They’re expected to be used for applications such as intermittent sensors, where they would slowly charge a supercapacitor which could release useful amounts of power in short bursts.

It’s being touted as an environmental win because the carbon-14 is sourced from radioactive waste, but against that it’s not unreasonable to have a concern about the things being radioactive. The company commercializing the tech leads with the bold question: “What would you do with a power-cell that outlasts the device it powers?“, to which we would hope the answer won’t be “Throw it away to be a piece of orphaned radioactive waste in the environment when the device it powers is outlasted”. We’ll have to wait and see whether devices containing these things turn up on the surplus market in a couple of decades.

Fortunately the carbon-14 lives not in cartoonish vats of radioactive green slime but safely locked away in diamond, about the safest medium for it to be in. The prototype devices are also tiny, so we’re guessing that the quantity of carbon-14 involved is also small enough to not be a problem. We’re curious though whether they could become a valuable enough commodity to be reused and recycled in themselves, after all something that supplies energy for decades could power several different devices over its lifetime. Either way, it’s a major improvement over a tritium cell.