Popular Mechanics (South Africa)
The radioactive diamond battery that will run for 28 000 years
IN LESS THAN TWO YEARS, YOU MIGHT BE ABLE to buy a smartwatch – powered with a radioactive diamond battery – that will outlive you and your progeny for generations. The potentially game-changing battery comes from the San Francisco-based start-up Nano Diamond Battery (NDB), which lauds its namesake ‘high-power diamond-based alpha, beta, and neutron voltaic battery’ for its ability to give devices ‘life-long and green energy’. Imagine: Just one battery could power your insulin pump or pacemaker for your entire life (with loads of time to spare). Or it could provide the juice for a space rover, collecting Mars regolith samples for decades without any human assistance.
Those are ambitious goals. So, could NDB’s bold claims actually become reality?
First, let’s dissect the specs. To build its Nano Diamond Battery, NDB uses layers of impossibly tiny, panelled nano diamonds (for context, one nanometre is one billionth of a metre). Diamonds have exceptional heat conductance, which makes them ideal for electronic devices. In fact, they are the best-known natural conductor of heat, according to a publication by the University of Houston’s College of Engineering – and are three to four times more effective than copper or silver.
Scientists cultivate these miniature diamonds using chemical vapour deposition, a process in which gases at extremely high temperatures force carbon to crystallise on a substrate material. That process, NDB admits, creates a cost bottleneck; making the special diamonds is energyintensive and expensive.
After all, they’re ‘artificially boron-doped diamonds,’ explains Yury Gogotsi, director of the AJ Drexel Nanomaterials Institute at Drexel University in Philadelphia. (Gogotsi has no affiliation with NDB.) That process produces diamonds with blue colour and higher conductivity than the average diamond. True blue diamonds (see sidebar) are naturally occurring on Earth, but they are rarer and even more expensive than artificial blue diamonds.
Once NDB has sourced the nano diamonds, the company combines them with radioactive isotopes from nuclear waste. Specifically, they use radioactive isotopes of uranium and plutonium, ‘which probably come from radioactive power plants’ waste,’ Gogotsi says.
From there, single-crystal diamonds – just a few square millimetres in size – move heat away from the radioactively decaying isotopes so quickly that the transaction actually generates electricity. ‘The decay sources deposit their energy on to the NDB transducer, which converts the kinetic energy of the incident radiation to electrical energy,’ says Nima Golsharifi, CEO of NDB.
You’re probably wondering what the catch is. There’s a diamond battery out there that really uses nuclear waste, lasts thousands of years, and involves layers of only the most minuscule diamonds?
It’s slightly more complicated than that. Each battery cell will produce only a small amount of energy, for one thing, so scientists must combine the cells in huge numbers in order to regularly power large devices – raising the cost a great deal, along with increasing the complexity.
Golsharifi touts the tiny size of the Nano Diamond Battery cells as an advantage for scalability, though. ‘Take the battery for a wristwatch, for instance – it consumes around two microwatts, [so] a much smaller NDB cell would be sufficient,’ he explains. ‘So if we need to power a different application, the number of stacked cells can be increased to meet the demand.’
Still, there’s the issue of wear-and-tear: Researchers implant the nuclear waste inside the diamond cells, which creates a natural structural weakness that, statistically speaking, will eventually fail in some of the cells over time, Gogotsi explains. When the Nano Diamond Battery becomes widely available in the future, there’s a chance that some of the cells will break or simply go to waste with the devices that they power.
‘This creates an issue of nuclear waste, which is inevitable if large numbers of batteries are used,’ Gogotsi says. ‘Some of them will eventually break apart. This may not be an issue in space, but will certainly be a concern on the surface of Earth.’
That doesn’t mean the diamond battery isn’t a worthwhile pursuit. If those issues are addressed, some possible applications for it include long-term-use devices such as hearing aids or pacemakers. ‘Take a child that gets a hearing aid implanted or an elderly person with a pacemaker; people shouldn’t have to go through the possibly traumatising surgery more than once,’ Golsharifi explains.
The batteries could even prove useful in space vehicles that need to run for years without help, NDB says. Take satellites, for instance. NDB’s claim that the battery lasts 28 000 years is based, in part, on these low-power space applications. Voyager – NASA’s iconic space probe, meant to study the outer solar system when it launched back in September 1977 – used three ‘Multi-Hundred Watt Radioisotope Thermoelectric Generators’ (MHW-RTGs) for power. Each generator’s power output began at just 158 watts, which is less energy than you’d need to power a household light fixture for a year.
And if enough of these diamond battery cells are combined, they could still power electronics here on Earth with higher energy demands, from LED displays on tablets to mobile phones. But for its first commercial product, NDB plans to introduce a smartwatch, with an expected launch date sometime this year. If that really happens, you could own one watch with a single battery and pass it down for generations without ever needing a replacement – talk about an heirloom.
Still, NDB plays its cards very close to the vest, divulging few of the nitty-gritty details about the Nano Diamond Battery (its power density, for instance). And, there aren’t even video demos of the technology yet. But the promise of the radioactive diamond battery is still very real, and NDB’s forthcoming smartwatch will tell us a lot about the feasibility of such technology in other applications. And we’ll be waiting – all we have is time.