Harvesting renewable energy from heat

Tiny microgenerators that create power from heat could provide a lightweight, renewable alternative to batteries for wireless sensor systems.

SouthamptonUniversity researchers hope to develop a micro-machined generator that can produce a few milliwatts of power by utilising the contrast in temperature between two different metals.

The three-year government-funded project will particularly focus on using the thermoelectric microgenerators to produce power from humans. This could lead to reliable sensors for hospital patients as well as numerous applications in sports science. Miniaturised sensors that don’t need batteries could easily be attached to an athlete and would be lighter and unobtrusive.

According to project leader, Prof Neil White, harvesting energy from ambient sources in the environment such as heat could help reduce the reliance on batteries and wires.

‘In the future there will be sensors everywhere. For applications such as pollution monitoring for the sea, you will have to think how to power these systems using energy harvesting as it isn’t practical either to mains-wire them or change batteries,’ he said.

There are a number of advantages to using thermoelectric power generators for miniature applications because they are extremely reliable and have long lifetimes, said White. However, existing thermoelectric generators are relatively inefficient and current lab-based systems are too big for power portable sensors. The project will use advanced micro-machining techniques to develop a new generation of miniaturised microgenerators on a silicon substrate.

White said that the move towards developing low-power, long-life sensors — such as those embedded in buildings and bridges — means that the small amount of power produced by thermoelectric power harvesting is now becoming a viable energy source.

‘Even the few milliwatts we could get from a microgenerator could power radio frequency signals and microprocessors,’ he said.