Technology in-depth
While the basics of the technology are very simplistic with groups (we call them cells or fields) of transducers, a rectifier to get from alternating to direct current and some electronics to stabilise the harvested power. To gain more efficiency and effectiveness in all sorts of environments some more challenges arise.
FPGA and 'micro harvesting'
By adding some intelligence to it, by using an FPGA for instance, we can dynamically configure the transducer field to be more serial or parallel connected to reduce the resistance on the board itself, providing more usable power. In certain situations we've seen complete blocking of the transducer field when dB-levels where very high (95dB+) - for instance when measuring outside a car driving over 100 kilometres per hour.
At first we've got stable results around 300mV, which was the first usable power source, this is comparable with the micro infrastructure of solar cells. For instance when using special power conversion chipsets or coupled inductors (by Analog Devices, RECOM or Wurth Electronics for example), that have been developed for thermal or solar energy, we can convert the power towards 3.3 or 5V.
While using larger cells of transducers with a 'field' of rectifiers, we've managed to get directly usable voltage levels around ~5V. Stabilising these inputs using capacitors and we have quite usable power. We can easily group these sources into a more used 12V bus with some linear regulators and again inductors.
Sensors to monitor external factors
There are a lot of external factors that influence the results of the harvesting; like air pressure, temperature and humidity. Also the angle of the transducers towards the waves makes a difference. In our development process and on the soon to be available development board a lot of sensors are included to monitor these.
Power usability and storage
The easiest way of getting a perfectly stable power source is obviously storing the irregular power source coming from the harvester; (super)capacitors are an option for this, but batteries are the even better choice. We've developed a tiny battery charger system that can cope with the low and irregular voltages and currents coming from our harvesters to charge 3.7V batteries (LiPO or Lithium).
More information
When this information makes you hungry for more information, test reports, electrical schematics, access to our development boards and what not...
You might be an engineer (or student) and willing to help us in our journey to make sound pollution a usable thing; please don't hesitate and contact us to gain access!
