Knowledge Base
People have lots of questions about our technology and how it works. Below are some of the most common questions we receive. If you have any additional queries, feel free to reach out.
Essential Information
What voltage does the diamond produce?
The Ni63 version has produced close to 1.9V.
The C14 is being optimised to achieve at least 2V.
What is the capability of the Diamond Battery versus a normal 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.
In comparison, a diamond beta-battery would be designed to last longer. The actual amount of C14 in each battery has yet to be decided but as a rough guide, one battery, containing 1g of C14 will deliver 15J per day (based on calculations extrapolated from Ni63 prototype). On the face of it, this is less than an AA battery. However, it will continue to produce this level of output for 5,730 years, so its total energy storage rating is very high (2.7TeraJ aka million million Joules).
What is the approximate volume of the battery?
The approximate volume of the prototype diamond devices we are working on are 10 mm x 10mm with a thickness up to
0.5 mm. This is the ‘active’ device and does not include the metallic contacts and wiring to complete the circuit or the casing that will enclose it.
What is the current rating over temperature?
We expect the current rating to be near continuous with temperature. We already know that as a detector material the diamond doesn’t require heating to work and we also know that it has good stability up to many hundreds of degrees. We have heat cycled the diamond structures to 750C to evaluate the material stability but have not yet tested their power output under such elevated temperature ambients.
Is the battery technology scalable?
In short – yes! Much like a normal battery consists of multiple cells we could also sum currents from multiple cells to increase the power output.
How far away from potential practical application is this process?
We are still at TRL 4 at the moment and currently seeking funding to take the concept forwards through a series of more complex and efficient prototypes. One route is to grow the isotopically layered C-14/C-12 diamonds in the lab from high purity gases. For this we require substantially larger quantities of C-14 methane than we currently have available. Another possible route is to grow Nitrogen-doped diamond in the lab and then irradiate it in a reactor 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. Equally, we can also infuse the diamond device with H-3 as well as or instead of C-14. Tritium has a shorter radioactive half-life (12.3 years) which means we can get more power out of device using Tritium but only for several decades.
Are these synthetic diamonds similar in appearance to those used in conventional jewellery?
No the diamond is in the form of a sandwich composed of thin layers each made up of large polycrystalline grains rather than the naturally formed single crystal diamonds found in jewellery.
What happens to the C-14 when it undergoes radioactive decay?
Carbon-14 decays to nitrogen-14 by beta emission. The beta particle is essentially a high energy (Average decay energy 50keV) electron and in our device this initiates a cascade of low-energy electrons which are collected by the outer electrode. Over time this leads to a build-up of nitrogen but doesn’t destroy the diamond structure because nitrogen is surprisingly soluble. Diamond has a solubility limit for substitutional nitrogen close to 2x10_18 cm–3 in CVD-formed diamond. It would take hundreds of years for this transformation to become noticeable on the performance of the device mainly because the majority of the current is generated in the bounding (and isotopically pure) ‘clean’ diamond layers.
How is current generated and how does it flow?
As explained above the beta particle released by each C-14 decay moves into the surrounding diamond structure creating 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.
What sort of costs are involved in processing the nuclear waste into diamond battery form?
The exact costs for waste processing are not known. However, cost estimates for disposing of the graphite waste are £46k/m3 for ILW and £3k/m3 for LLW. Therefore, if the waste processing to remove the C14 reclassifies the waste as LLW, then any cost under £43k/m3 will represent a saving to the UK taxpayer.
What type of scale will be required for commercial viability?
We are still at TRL 4 at the moment and currently seeking funding to take the concept forwards through a series of more complex and efficient prototypes. Commercial viability is an aspect that will be investigated through the project, in partnership with the Research and Development (RED) team at the University of Bristol and with the UKAEA.
Is there an optimum quantity of carbon-14 that provides the best power to weight ratio?
In short, yes there probably is as the cost of C14 is the largest part, and so increasing the C14 for little gain in power will not be economically viable. However, the exact quantity is still to be determined and will be investigated through the ongoing work.
How is power transferred from the diamond to the device it powers?
It is unlikely that the diamond battery will provide direct power to the 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.
Internship Opportunities
As a way to see if people are a good fit for our team we like to use internships as a tool for building understanding and doing some useful work at the same time. Please get in touch if you'd like to discuss opportunities.
Requesting a Demo
If you'd liken see a demo of one of our devices then please get in contact and we be happy to discuss a meeting.