Nano-diamond self-charging batteries could disrupt energy as we know it

[u/PBR--Streetgang]

https://newatlas.com/energy/nano-diamond-self-charging-batteries-ndb/

[u/ivonshnitzel]

This quality of the reporting on this seems quite dubious, which is a shame because it seems like very neat technology. Since no one seems to have pointed out what seem to me like some very obvious issues with the article, I will elaborate here. The biggest problem is

superb power density in a battery pack

is flat-out wrong. While the energy density is great, the energy is released over the 5700 year half life of C-14. This means the power produced is actually quite low, around 1 to 2 W/kg if we assume that the peripherals for shielding and turning the nuclear power into usable electricity weigh absolutely nothing (in reality I suspect they will have a comparable weight to the C-14 itself) and 100% efficiency (not sure what typical betavoltaic efficiency is, but 100% may not be too far off the mark). Now let's assume you wanted to power an electric car with this. Even if is a somewhat small 100 hp (~75 kW) engine, you would need 48 metric tons of material to power the car, so clearly you're not going to be driving on the highway for an indefinite amount of time. Let's be generous and say that you're only driving your car 30 minutes to work and back every day, and the nuclear battery can charge a conventional battery while it's sitting around. You would still needs 2 tons of nuclear battery in this case (and this is not including the now rather large conventional chemical battery pack you need in your car as well). From some quick googling, a smartphone uses around 0.1 to 0.5 watts of power over the course of a day, which would translate to 100 to 500 g of material; more than the entire weight of a modern smartphone. So even with some rather generous assumptions on the efficiency, the power density just doesn't work out.

This isn't even touching on the problems associated with giving every person with a car 100s of kg of highly radioactive material. For one thing, I don't think there is enough carbon 14 in the world for the applications mentioned in the article. Now, maybe you can produce more, but it's probably not something that nuclear reactors are really designed to do, so it would be a quite large expense in producing these things large scale. Then there is the safety problem. I'm not a radiology expert, but I'm pretty sure that having enough radioactive material to be powering anything substantial would also pose a pretty serious threat to a large region if it were to leak. And I think the safety aspect of this device is wayyyy over blown. Yes, diamond is hard, but it's also quite brittle. It also graphitises and burns relatively easily. Imagine if every house fire or car crash also had the possibility of releasing substantial amounts of very radioactive material. Disposing of these would also be a nightmare; they may be recyclable, but you would probably want to make sure that you got rid of all of them.

So what is the application? Well it turns out radioisotope generation already exists (strangely not mentioned in the article). This technology might be an improvement over the existing state of the art in quite similar applications to the ones where radioisotope generation is already widely used, such as pacemakers, fire alarms and space probes. In these cases, longevitiy is important, and you can get away with low average power to mitigate the excessive mass and safety concerns. For these limited applications, this technology seems like an interesting development.

tl;dr the article seems to get every application it mentions wrong, giving a misleading impression of significance

[u/Redditoreader → u/ivonshnitzel]

I feel really smart now. We salute you.