Nuclear diamond batteries
Diamond is a semiconductor which can generate electricity when exposed to beta radiation, which comprises electrically charged particles (electrons or positrons). This effect can be used to make beta radiation detectors or as a source of electricity in its own right. Devices generating electricity from beta radiation are generically known as betavoltaics (Wikipedia). Such devices may use beta emitting isotopes such as Tritium (an isotope of Hydrogen) or isotopes of Nickel or Promethium.
Russian Nickel-63 battery
A 2018 article from the Moscow Institute of Physics and Technology describes work on a battery based on Nickel-63 which claims to achieve an energy density of 3,300 milliwatt-hours per gram, "which is more than in any other nuclear battery based on nickel-63, and 10 times more than the specific energy of commercial chemical cells". The battery has a power output of just under 1 microWatt.
The article also has a brief discussion of the history of betavoltaic generators.
Back in 1913, Henry Moseley invented the first power generator based on radioactive decay. His nuclear battery consisted of a glass sphere silvered on the inside with a radium emitter mounted at the center on an isolated electrode. Electrons resulting from the beta decay of radium caused a potential difference between the silver film and the central electrode. However, the idle voltage of the device was way too high — tens of kilovolts — and the current was too low for practical applications.
In 1953, Paul Rappaport proposed the use of semiconducting materials to convert the energy of beta decay into electricity. Beta particles — electrons and positrons — emitted by a radioactive source ionize atoms of a semiconductor, creating uncompensated charge carriers. In the presence of a static field of a p-n structure, the charges flow in one direction, resulting in an electric current. Batteries powered by beta decay came to be known as betavoltaics. The chief advantage of betavoltaic cells over galvanic cells is their longevity: Radioactive isotopes used in nuclear batteries have half-lives ranging from tens to hundreds of years, so their power output remains nearly constant for a very long time. Unfortunately, the power density of betavoltaic cells is significantly lower than that of their galvanic counterparts. Despite this, betavoltaics were in fact used in the ’70s to power cardiac pacemakers, before being phased out by cheaper lithium-ion batteries, even though the latter have shorter lifetimes.
Betavoltaic power sources should not be confused with radioisotope thermoelectric generators, or RTGs, which are also called nuclear batteries but operate on a different principle. Thermoelectric cells convert the heat released by radioactive decay into electricity using thermocouples. The efficiency of RTGs is only several percent and depends on temperature. But owing to their longevity and relatively simple design, thermoelectric power sources are widely used to power spacecraft such as the New Horizons probe and Mars rover Curiosity. RTGs were previously used on unmanned remote facilities such as lighthouses and automatic weather stations. However, this practice was abandoned, because used radioactive fuel was hard to recycle and leaked into the environment.
The Carbon-14 isotope is also a beta emitter and since diamond is a form of carbon and can be made synthetically it should be possible to produce devices in which diamond is both the beta source and the converter of beta radiation to electricity.
An article on the South-West Nuclear Hub website (via Internet Archive) reports that a prototype had been demonstrated using Nickel-63 but that the team was working to use Carbon-14.
Current generation in these devices is driven by the beta particle released by each C-14 decay moving into the surrounding diamond structure. This creates successive electron hole pairs due to inelastic impacts with other carbon atoms and generates a cascade of lower energy electrons that are collected at the metal contact to the diamond. In conduction terms, diamond is a semiconductor (like silicon) and like the operation of a silicon solar panel cell, electric current flows when valence electrons are given enough energy to be promoted into the conduction band.
Despite their low-power, relative to current battery technologies, the life-time of these diamond batteries could revolutionise the powering of devices over long timescales. The actual amount of carbon-14 in each battery has yet to be decided but one battery, containing 1g of carbon-14, would deliver 15 Joules per day. This is less than an AA battery. Standard alkaline AA batteries are designed for short timeframe discharge: one battery weighing about 20g has an energy storage rating of 700J/g. If operated continuously, this would run out in 24 hours. Using carbon-14 the battery would take 5,730 years to reach 50 per cent power, which is about as long as human civilization has existed. However, it is unlikely that the diamond battery will provide direct power to an attached device. More likely is that it will be associated with a capacitor that will be ‘trickle charged’ by the battery and then discharge at set intervals, to power devices at set intervals or to continually power low draw devices.
These batteries are envisaged to be used in situations where it is not feasible to charge or replace conventional batteries. Obvious applications would be in low-power electrical devices where long life of the energy source is needed, such as pacemakers, satellites, high-altitude drones or even spacecraft.
Professor Tom Scott talked about his team's work at the Cabot Institute Annual Lecture 2016 'Ideas to Change the World':
In his talk Scott talks about the problem of disposing of approximately 90,000 tonnes of radioactive graphite which was used as moderators in the UK's now-decommissioned Magnox reactors, such as the one at Berkeley in Gloucestershire (to which will be added the graphite in its AGR fleet as these are decommissioned). This material is classified as intermediate level waste. The Bristol researchers have found that "the radioactive carbon-14 is concentrated at the surface of these blocks, making it possible to process it to remove the majority of the radioactive material, reducing the cost and challenge of safely storing this nuclear waste. The extracted carbon-14 can then incorporated into a diamond to produce a nuclear-powered battery." (Of course the C14 component need not be used in this way: it could be disposed of separately to make disposal of the bulk of less-radioactive graphite easier.)
Energy density and power density
Nuclear diamond batteries have high energy densities, for example 3,300 milliwatt-hours per gram (i.e. 3.3 Wh/g) for the MITP Nickel-63 device above. For comparison Lithium-ion batteries have densities of 100-265 Wh/kg i.e. 0.1-0.265 Wh/g). However a Lithium battery can deliver its stored energy in a matter of hours whereas betavoltaic devices deliver theirs at an exponentially decreasing rate as their isotope decays. For example with Nickel-63, which has a half life of 100.1 years, half of its energy will be delivered over the first 100.1 years, half of the remainder over the next, etc. The average power output over the first century will be about 0.2 microWatts/g so a 40g cell (the weight of an 18650 Lithium cell) would give 8 microWatts. An 18650 Lithium cell could easily discharge at a couple of amps, which would give a power output of 8 Watts or so - a million times greater. So nuclear diamond batteries have very low power densities compared to chemical batteries.
An article in lifestyle magazine "New Atlas" claims "Nano-diamond self-charging batteries could disrupt energy as we know it"
The article contains a reasonably accurate description of the principle of operation of such devices:
The heart of each cell is a small piece of recycled nuclear waste. NDB uses graphite nuclear reactor parts that have absorbed radiation from nuclear fuel rods and have themselves become radioactive. Untreated, it's high-grade nuclear waste: dangerous, difficult and expensive to store, with a very long half-life.
This graphite is rich in the carbon-14 radioisotope, which undergoes beta decay into nitrogen, releasing an anti-neutrino and a beta decay electron in the process. NDB takes this graphite, purifies it and uses it to create tiny carbon-14 diamonds. The diamond structure acts as a semiconductor and heat sink, collecting the charge and transporting it out. Completely encasing the radioactive carbon-14 diamond is a layer of cheap, non-radioactive, lab-created carbon-12 diamond, which contains the energetic particles, prevents radiation leaks and acts as a super-hard protective and tamper-proof layer.
To create a battery cell, several layers of this nano-diamond material are stacked up and stored with a tiny integrated circuit board and a small supercapacitor to collect, store and instantly distribute the charge. NDB says it'll conform to any shape or standard, including AA, AAA, 18650, 2170 or all manner of custom sizes.
And so what you get is a tiny miniature power generator in the shape of a battery that never needs charging – and that NDB says will be cost-competitive with, and sometimes significantly less expensive than – current lithium batteries. That equation is helped along by the fact that some of the suppliers of the original nuclear waste will pay NDB to take it off their hands.
Radiation levels from a cell, NDB tells us, will be less than the radiation levels produced by the human body itself, making it totally safe for use in a variety of applications. At the small scale, these could include things like pacemaker batteries and other electronic implants, where their long lifespan will save the wearer from replacement surgeries. They could also be placed directly onto circuit boards, delivering power for the lifespan of a device.
However the article claims that such batteries could power mobile phones, electric vehicles, and even supply the world's entire energy requirements:
California company NDB says its nano-diamond batteries will absolutely upend the energy equation, acting like tiny nuclear generators. They will blow any energy density comparison out of the water, lasting anywhere from a decade to 28,000 years without ever needing a charge. They will offer higher power density than lithium-ion. They will be nigh-on indestructible and totally safe in an electric car crash. And in some applications, like electric cars, they stand to be considerably cheaper than current lithium-ion packs despite their huge advantages.
In a consumer electronics application, NDB's Neel Naicker gives us an example of just how different these devices would be: "Think of it in an iPhone. With the same size battery, it would charge your battery from zero to full, five times an hour. Imagine that. Imagine a world where you wouldn't have to charge your battery at all for the day. Now imagine for the week, for the month… How about for decades? That's what we're able to do with this technology."
And it can scale up to electric vehicle sizes and beyond, offering superb power density in a battery pack that is projected to last as long as 90 years in that application – something that could be pulled out of your old car and put into a new one. If part of a cell fails, the active nano diamond part can be recycled into another cell, and once they reach the end of their lifespan – which could be up to 28,000 years for a low-powered sensor that might, for example, be used on a satellite – they leave nothing but "harmless byproducts."
In the words of Dr. John Shawe-Taylor, UNESCO Chair and University College London Professor: “NDB has the potential to solve the major global issue of carbon emissions in one stroke without the expensive infrastructure projects, energy transportation costs, or negative environmental impacts associated with alternate solutions such as carbon capture at fossil fuel power stations, hydroelectric plants, turbines, or nuclear power stations. Their technology’s ability to deliver energy over very long periods of time without the need for recharging, refueling, or servicing puts them in an ideal position to tackle the world’s energy requirements through a distributed solution with close to zero environmental impact and energy transportation costs.”
Indeed, the NDB battery offers an outstanding 24-hour energy proposition for off-grid living , and the NDB team is adamant that it wishes to devote a percentage of its time to providing it to needy remote communities as a charity service with the support of some of the company's business customers.
Should the company chew right through the world's full supply of carbon-14 nuclear waste – a prospect that would take some extremely serious volume – NDB says it can create its own carbon-14 raw material simply and cost-effectively.
The company has completed a proof of concept, and is ready to begin building its commercial prototype once its labs reopen after COVID shutdown. A low-powered commercial version is expected to hit the market in less than two years, and the high-powered version is projected for five years' time. NDB says it's well ahead of its competition with patents pending on its technology and manufacturing processes.
Should this pan out as promised, it's hard to see how this won't be a revolutionary power source. Such a long-life battery would fundamentally challenge the disposable ethos of many modern technologies, or lead to battery packs that consumers carry with them from phone to phone, car to car, laptop to laptop across decades. NDB-equipped homes can be grid-connected or not. Each battery is its own near-inexhaustible green energy source, quietly turning nuclear waste into useful energy.
The article, and the "NDB" company it quotes, are making claims about power density which are simply not true; they are off by a a factor of millions.
Snopes assesses the claim that "Man-made, radioactive “diamond batteries” are capable of providing thousands of years of energy without a charge" as a mixture of true and false, summarising:
While the science underpinning the concept is valid, its application remains wholly theoretical at this point.
The idea of generating a virtually inexhaustible source of energy from radioactive material has long been discussed and, indeed, is already employed in a variety of non diamond-based technologies; “diamond batteries” are a theoretical application of this technology currently in development.
The concept of a “diamond battery”, which would be created synthetically from radioactive carbon-14 sourced from nuclear waste is, at this point, a theoretical idea and it is one that comes with myriad challenges not discussed in viral stories.
Snopes refers to an article in the World Economic Forum’s “Futurism” column based (with many errors) on Tom Scott's Cabot Institute lecture.
Sadly Snopes makes its own errors, claiming that "undisposable radioactive graphite" builds up "in containers that store spent nuclear fuel", and that Plutonium was used in betavoltaic heart pacemaker power supplies.
Footnotes and references
- Energy response of diamond sensor to beta radiation Modeste Tchakoua Tchouaso, Haruetai Kasiwattanawut, Mark A.Prelas; Applied Radiation and Isotopes; Sept 2018
- High power density nuclear battery prototype based on diamond Schottky diodes V.S.Bormashov, S.Yu.Troschiev, S.A.Tarelkin, A.P.Volkov, D.V.Teteruk, A.V.Golovanov, M.S.Kuznetsov, N.V.Kornilov, S.A.Terentiev, V.D.Blank; Diamond and Related Materials; April 2018
- Lithium-Ion battery Clean Energy Institute
- 0.5 * 3.3 Watt hours/gram / 100 years * 365.25 days/year * 24 hours/day = 1.8822E-7 Watts/gram
- It was used in pacemakers but Plutonium is not a beta emitter and it was used in Radioisotope Thermoelectric Generators