Energy Harvesting for Electronic Systems

University essay from Lunds universitet/Industriell elektroteknik och automation

Abstract: Energy harvesting enables products to become more self-sufficient of power and offers the possibility to avoid battery exchange and power cables. The performance and applicability of the most promising or popular small scale energy harvesting technologies are investigated in this thesis. The focus lies on the amount of potential energy that can be harvested and how limited the technology is to a specific environment. Different power management and energy storage methods are also examined. Two prototypes demonstrating different energy harvesting phenomena are presented. The first prototype is able to harvest an average of 152 μW at 302-346 lux using 4 AM-1417 photovoltaic cells with an area of 19.46 cm2. The 302-346 lux span is measured in indoor fluorescent office lighting. The second prototype uses a DC motor to harvest the energy from the motion of opening a door. It is possible to harvest more than 470 μJ from a single door opening with the prototype. This requires a minimum average revolving speed of 7.5 rpm during the door opening. The thesis concludes that photovoltaic cells are relatively easy to use in practice and that an environment with sufficient energy is not difficult to find. Piezoelectricity and vibration based electromagnetism has a low applicability due to the fact that the transducers only gain a useful power output at their resonance frequency. However, electromagnetic pushbuttons or rotation generators are proven to be useful. Thermoelectric elements are highly dependent on specific thermal conditions, making them applicable in some cases but hard to use as an all-round energy harvesting device. Radiofrequency energy harvesting is also investigated but it is concluded that this technology is not yet developed for practical use.

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