Vibration Energy Touted As New Power Source

Vibration energy could provide a clean source of commercial electricity, that could be available within five years according to researchers at the University of Bristol.

Vibrations caused by machines, such as helicopters and trains – or even household appliances such as kettles – could be used to produce power, say the researchers, funded by the Engineering and Physical Sciences Research Council (EPSRC). Even the movement of the human body can be harnessed, they say.

The discipline is known as ‘energy harvesting‘, and has been around now for at least ten years, with some commercial devices already existing in specialised areas. For example, some industrial pumps already use vibrations in order to power the sensors that monitors the pumps’ condition, according to the team.

“It’s hoped that within five years ‘energy harvesting’ could be powering many more of our devices from heart monitors to mobile phones,” said the team.

“Vibration energy-harvesting devices use a spring with a mass on the end”, said Dr Stephen Burrow, who is leading the project. “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,” Dr Burrow said.

The team are being funded by EPSRC to the tune of just over £197,000 ($322,000) for the three year project.

The problem the team have to overcome is that currently, existing devices can only exploit vibrations that have a narrow range of frequencies (the frequency is the number of vibrations occurring per second). If the vibrations don’t occur at the right frequency, very little power can be produced and it will be too low to be useable.

In applications such as transportation, or even just human movement, the frequency of vibrations changes all the time, so the Bristol team are developing a new type of device where the mass and spring resonate over a much wider range of frequencies.

Essentially, it hopes to exploit the properties of non-linear springs over conventional springs as, when these non-linear springs are used in an energy harvester, the mass and spring no longer resonate at just one frequency but will respond to a wide range of vibration frequencies.

This, the team believes, will enable a much wider range of vibrations to be exploited and so increase the overall contribution that energy harvesting could make to energy supplies.

The thinking behind this concept is the energy harvesters will be able to generate low-level power on a similar scale to batteries but without the harmful side effects (i.e. toxic chemicals). They could also be used in applications where it is not easy to replace the battery, such as a heart monitor. Or they could be utilised for applications where hard wiring is impracticable, vulnerable to damage, or difficult to access for maintenance purposes.

Other real world applications of this technology include monitors for brake temperatures in railway rolling stock, or even to monitor the stresses experienced by engine components or structural elements in buildings.

“There’s a huge amount of free, clean energy out there in the form of vibrations that just can’t be tapped at the moment,” concluded Dr Burrow. “Wider-frequency energy harvesters could make a valuable contribution to meeting energy needs more efficiently and sustainably.”