A team of physicists and chemists from the University of Bristol have grown a man-made diamond that, when placed in a radioactive field, is able to generate a small electrical current. The development could solve some of the problems of nuclear waste, clean electricity generation and battery life.
Unlike the majority of electricity-generation technologies, which use energy to move a magnet through a coil of wire to generate a current, the man-made diamond is able to produce a charge simply by being placed in close proximity to a radioactive source. There are no moving parts involved, no emissions generated and no maintenance required, just direct electricity generation. By moving to encapsulate radioactive material inside the diamonds, we turn a long-term problem of nuclear waste into a nuclear-powered battery and a long-term supply of clean energy.
The team have demonstrated a prototype ‘diamond battery’ using Nickel-63 as the radiation source. However, they are now working to significantly improve efficiency by utilising carbon-14, a radioactive version of carbon, which is generated in graphite blocks used to moderate the reaction in nuclear power plants. Research by academics at Bristol has shown 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.
This technology is currently at a Technology Readiness Level (TRL) of 2 and the project team are taking the concept forwards through a series of more complex and efficient prototypes. One route being investigated is to grow the isotopically layered diamonds in the lab from high purity gases. Another possible route is to grow Nitrogen-doped diamond in the lab and then expose it to a high neutron flux inside a reactor core to grow-in the C-14 and subsequently deposit ‘clean’ diamond on the outside. This would achieve the same effect but without full isotopic purity. The team is about to do this with partners, Kyoto University, in the research reactor at KURRI in Japan.
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. Some of the best public suggestions have been collated in a blog post here.
A presentation featuring this technology was given by Prof. Tom Scott at the Cabot Institute's recent event: 'Ideas to Change the World'.
Below are just some of your suggested applications for our diamond battery. Have your own idea? Tweet us using #diamondbattery