The Bristol team is exploring how vibrations caused by machines such as helicopters and trains could be used to produce power. Vibrations from household appliances and the movement of the human body could also be harnessed in this way.
Commercial energy-harvesting devices already exist which, for example, use vibrations from industrial pumps to power sensors that monitor the pumps’ condition.
‘Vibration energy-harvesting devices use a spring with a mass on the end,’ explains project leader Dr Stephen Burrow, in the Department of Aerospace Engineering. ‘The mass and spring exploit a phenomenon called resonance to amplify small vibrations, enabling useful energy to be extracted. Even just a few milliwatts can power small electronic devices like a heart rate monitor or an engine temperature sensor, but it can also be used to recharge power-hungry devices like MP3 players or mobile phones.’
But existing devices can only exploit vibrations with a narrow range of frequencies. If the vibrations don’t occur at the right frequency, too little usable power can be produced. This is a big problem in applications like transport or human movement, where the vibration frequencies are constantly changing.
However, the Bristol team is developing a new type of device, where the mass and spring resonate over a much wider range of frequencies. This would enable a much wider range of vibrations to be exploited.
The team believes it can achieve this by exploiting the properties of nonlinear springs, which allow the energy harvester to respond to a wider range of vibration frequencies than conventional springs.
Energy harvesters generate low-level power on a similar scale to batteries, but without the need for battery replacement or disposal. They are also suited to applications where hard wiring would be impracticable, vulnerable to damage, or difficult to access for maintenance purposes.
Energy harvesters could be used extensively, for example to provide power for wireless monitoring and diagnostic sensors that generate data on a person’s heart rate, body temperature or blood pressure; or stresses experienced by engine components, structural elements in buildings etc.; or brake temperatures in railway rolling stock.
The three-year project, which will run until January 2011, is receiving nearly £200 000 (US$330 000) in funding from the UK’s Engineering and Physical Sciences Research Council (EPSRC).