Sensors for small low-power mobile devices which never need battery change and charging could be on the horizon thanks to a more practical energy harvester developed by Siemens.
Siemens researchers have developed an Energy Harvester which can efficiently convert mechanical energy into electricity.
The tiny power plant can be integrated into other equipment like sensors, allowing true stand-alone operation without batteries or wireless power transmission. This can be especially useful in hazardous, isolated or portable environments.
The technology uses a spring-mass system that is a few centimetres long. It converts movements with various frequencies and amplitudes into electricity with a power of several milliwatts.
Mechanical energy can be derived from vibrations or other oscillations. The Energy Harvester differs from earlier developments in that it works with a wider range of frequency and amplitude, allowing it to take advantage of more sources of energy.
The Energy Harvester uses stacks of piezoelectric materials that Siemens Corporate Technology helped to develop in the 1990s as high-performance precision drives for vehicle engine injection valves.
These piezoelectric ceramics expand when an electric voltage is applied to them. However, when a mechanical strain is applied, these materials generate electricity, which is how the Energy Harvester converts mechanical movement to electricity.
The resonant frequency of the spring-mass systems adapts itself to the variable frequency of the ambient motion by changing its rigidity. The system can make use of small motions to generate power, and also increases its resistance to damage by impact.