| Description: |
Wireless sensors are typically powered by accumulators of limited capacity and are therefore naturally constrained in terms of energy usage. An increasingly common solution to prolong system lifetime and reduce the need for manual upkeep is to employ some form of energy harvesting, thus enabling the sensor to scavenge energy from its environment to replenish its energy reserves. Magnetic field energy harvesting (MFEH) has emerged as an attractive approach for power grid systems, and entails scavenging energy through induction from an ambient alternating magnetic field. The presence of large currents in electrified railways leads to the generation of stray magnetic fields that may also be employed to this end. Due the non-invasive nature of MFEH, the approach has the potential to be widely deployed as part of low-cost railway condition and environmental monitoring systems to increase lifetime and reduce maintenance requirements. This PhD project introduces MFEH for railway systems as a research space, featuring possibly the first published description of the concept. As part of an initial feasibility study, an accurate analytic model is formulated for the power output of a free-standing MFEH device and verified against simulation and laboratory measurements. The viability of MFEH for railway systems is then demonstrated by a first-generation prototype system placed in situ along Norwegian railway. A model of the Norwegian railway electrification network is derived as a tool to select an optimal deployment location for an MFEH device. It is demonstrated how this model can be used to inform the decision of where to place a system by quantifying the potential for energy harvesting at a locations along the railway. Based on lessons learned from the first prototype, a second-generation energy harvester is designed, simulated, constructed, and tested both in the lab and in the field. The second-generation device is deployed in the field for a considerable duration and shown to successfully power a small wireless sensor, thereby demonstrating energy-neutral operation of a typical application. |