Hot on the heels of the NanoBattery comes another contender for the crown of most astonishing graphene device this week. The latest thing to emerge from Hong Kong Polytechnic University, and challenger for the crown, is a graphene based battery that works on ambient heat. The device, which is still to be peer reviewed, works by capturing the thermal energy of ions in solution and converting them into electrical energy. As such it has the potential to provide a virtually never ending supply of electricity from heat sources such as the body, the sun and chemical and mechanical processes.
The battery uses to good effect the fact that ions in aqueous solution move with such a high velocity that several kilojoules per kilogram per degree are contained within their motion. Transforming that thermal and kinetic energy into electricity occurs when the high speed ions collide with the graphene inside the battery. The battery comprises an aqueous solution of copper chloride with a graphene strip stretched across a gold and silver electrodes and works because the high level of conductivity across the graphene makes it easier for the displaced electron to travel through the circuit than to travel through the solution. When the copper ion collides with the graphene strip the electron has two options, combine with the copper or pass through the circuit; the circuit is the easier of these two possibilities and so the current flows.
In theory the power output lasts for as long as their is sufficient heat to raise the temperature of the solution. The output voltage increases with a rise in temperature and with the addition of ultrasound, a result of the increase in the speed of the ions. And so too with an increase in the concentration of the copper chloride solution.
The promise of a never ending supply of electricity would transform the battery market if the team’s claims are shown to stand up to scrutiny. It is too early to say whether the battery can produce sufficient power to make the device feasible for everyday use, however the concept looks promising and the Hong Kong team are now engaged in further research to see how the output can be improved.