Ferreira, S., S. Valtchev, F. Coito, and M. Mudrov,
"Mechanical vibration using piezoelectric material",
Proceedings - 2017 International Conference on Optimization of Electrical and Electronic Equipment, OPTIM 2017 and 2017 Intl Aegean Conference on Electrical Machines and Power Electronics, ACEMP 2017, United States, Institute of Electrical and Electronics Engineers Inc., pp. 681–686, 7, 2017.
AbstractPiezoelectric energy harvesting has received great attention over the last 20 years. The main goal of this work is to discuss the potential advantages of introducing non-linearities in the dynamics of a beam type piezoelectric vibration energy harvester. The described device is essentially a cantilever beam partially covered by piezoelectric material with a force electromagnetically applied to the beam. Through experimental tests it has been confirmed the benefits of introducing non-linearities in these types of systems.
Gonçalves, {J. T. }, {C. I. } Camus, and {S. S. } Valtchev,
"Solar thermoelectric system with biomass back-up",
Technological Innovation for Smart Systems - 8th IFIP WG 5.5/SOCOLNET Advanced Doctoral Conference on Computing, Electrical and Industrial Systems, DoCEIS 2017, Proceedings: Springer New York LLC, pp. 358–369, 1, 2017.
AbstractWith the objective of having a solar thermoelectric system, running for 24 h a day along the different seasons of the year it is necessary to dimension the adequate storage and back-up systems. The choice of the back-up source of energy depends on how sustainable the power plant should be. In this study, the choice was the use of biomass in order to have a 100{%} renewable power plant. The selected site was the Alentejo region (Portugal). The local Direct Normal Irradiation (DNI) data was used to simulate with the System Advisor Model program (SAM) considering a solar system with north field and molten salt storage. The system needs no back-up during three months in a year. The use of biomass pellets is a viable alternative because it makes the power plant 100{%} renewable and dispatchable without loss of energy due to over-dimension of the expensive solar field and molten storage system.
Cavalheiro, D., F. Moll, and S. Valtchev,
"TFET-Based Power Management Circuit for RF Energy Harvesting",
IEEE Journal of the Electron Devices Society, vol. 5, no. 1: Institute of Electrical and Electronics Engineers, pp. 7–17, 1, 2017.
AbstractThis paper proposes a Tunnel FET (TFET)-based power management circuit (PMC) for ultra-low power RF energy harvesting applications. In contrast with conventional thermionic devices, the band-to-band tunneling mechanism of TFETs allows a better switching performance at sub-0.2 V operation. As a result, improved efficiencies in RF-powered circuits are achieved, thanks to increased rectification performance at low power levels and to the reduced energy required for a proper PMC operation. It is shown by simulations that heterojunction TFET devices designed with III-V materials can improve the rectification process at received power levels below-20 dBm (915 MHz) when compared to the application of homojunction III-V TFETs and Si FinFETs. For an available power of-25 dBm, the proposed converter is able to deliver 1.1 $μ }\text{W}$ of average power (with 0.5 V) to the output load with a boost efficiency of 86{%}.