In recent years, many industries are showing great interest in sustainable and digitalised societies, with concepts such as cyber-physical systems (CPS). In doing so, efficiency data collection on a large scale and in real-time has become a crucial point of concern. From the initial data acquisition to the data storage and communication component of a CPS, maintaining a sensible efficiency and accuracy is of paramount importance for a sustainable society. One type of technology that has been gaining attention for its application to CPS is energy harvesting, which is a device or system that allows for the generation of energy, usually in the form of electricity, from low-quality energy sources. These energy sources could for instance be vibrations, waste heat, or electromagnetic waves. Regardless of its method, the prospect of energy being harvested from sources that have been wasted until now is quite promising for the realisation of CPS. However, one of the key challenges of most energy harvesting technologies is its low energy output. Many of these harvesting methods either have low energy output or energy conversion efficiency. As a result, much of the research surrounding this topic is currently concerned with increasing the total energy output of energy harvesters. In this research, the authors propose a novel energy harvesting sensor with a possible application for a temperature data acquisition device. This can for instance be for monitoring body temperature, which is not only important for our society in terms of public health, but also a highly quantifiable measure for monitoring health. The proposed device utilises the magnetic properties of materials as the working principle in order to produce electricity from low-quality subject heat while simultaneously monitoring the temperature. When a magnetic material is subjected to an external magnetic field, the magnetic moments of the material align, thereby causing the material to magnetise. The degree of magnetisation, or magnetic susceptibility is characterised by Curie’s law as being dependent on the material temperature. As the material approaches its Curie Temperature, a magnetic phase change occurs, causing a corresponding magnetic flux change. By incorporating electromagnetic induction with solenoids, the magnetic flux change of a known probe material could be measured as a voltage. Thus, this phenomenon can be applied for an energy harvesting temperature sensor in the near range of a material’s Curie Temperature, as the voltage reading is representative of the magnetic flux change and thus the material temperature. By manufacturing a magnetic material that has its Curie Temperature around the target temperature range, the device has the potential to operate as a temperature sensor for various targets.
Past explorations by the authors have shown that the application of magnetic phase transition for a temperature sensor based on magnetisation change is especially promising in the phase transition temperature region around the Curie Temperature of the material. Furthermore, the potential of the proposed device as a temperature sensor has been investigated by developing a theoretical model for the sensing scheme. Here, much of the focus is on the energy harvesting aspect of the device. Namely, the main concern of energy harvesters, that is, the energy conversion efficiency is investigated to demonstrate that the proposed device has great potential even in comparison to other similar energy harvesting technologies.
