Itamar Iliuk

Application of passive control to energy harvester efficiency using a nonideal portal frame structural support system

An analysis of a new energy harvester model is presented, based on a simple portal frame structure, considered a nonideal system due to the kind of excitation influenced by the response of the system, such as a direct current motor with limited power supply. The horizontal motion of the portal frame is considered under a nonideal excitation, and the approximated mathematical model of the system is obtained, considering the coupled oscillators. To model the piezoelectric coupling, the nonlinearities of the piezoelectric material were considered. A constantly sustained energy harvesting is essential for using these devices in real applications; for this, a control strategy is required. Passive control was obtained by means of a nonlinear substructure with properties of nonlinear energy sink. Numerical simulations were performed in order to find best values of control parameters. To check the robustness of the control strategy, an analysis considering uncertainties in the parameters of the model was performed, showing the efficiency of the passive control (energy pumping) in the suppression of the chaotic behavior, as well as the sensitivity of the control system to parametric errors. Passive control leads the system to a stable periodic orbit, allowing a more efficient energy harvest, due to the higher peak-to-peak amplitude of oscillation mean value. The passive control strategy eliminates the need for an active microcontroller to stabilize the system in a periodic orbit, improving the energy budget (harvested versus expended). The results show the displacement of the structure and the maximum power harvested by the device with and without passive nonlinear energy sink. It can be concluded that the application of passive control was successful. The control was robust and improved the energy harvested through the suppression of the chaotic motion, leading the system to a periodic orbit with stable amplitude of vibration, without damaging the structure.

Potential Application in Energy Harvesting of Intermodal Energy Exchange in a Frame: FEM Analysis

This paper presents a Finite Element Analysis (FEA) of modal energy exchange and harvesting in a simple portal frame structure. We consider both horizontal and vertical support excitations resonant first with the first mode (sway mode) and latter with the second mode (the first symmetrical mode). As 2:1 internal resonance is present between these two modes, the phenomena of mode saturation and energy exchange (modal coupling) may occur. Thus, energy pumped into the system through one of the modes, is partially transferred to the other mode, not directly excited. An evaluation of the energy available for harvesting in each of the considered mode is computed.

Thermal-hydraulic analysis under partial loss of flow accident hypothesis of a plate-type fuel surrounded by two water channels using RELAP5 code

Thermal-hydraulic analysis of plate-type fuel has great importance to the establishment of safety criteria, also to the licensing of the future nuclear reactor with the objective of propelling the Brazilian nuclear submarine. In this work, an analysis of a single plate-type fuel surrounding by two water channels was performed using the RELAP5 thermal-hydraulic code. To realize the simulations, a plate-type fuel with the meat of uranium dioxide sandwiched between two Zircaloy-4 plates was proposed. A partial loss of flow accident was simulated to show the behavior of the model under this type of accident. The results show that the critical heat flux was detected in the central region along the axial direction of the plate when the right water channel was blocked.

SOMMERFELD EFFECT IN A VIBRATION MODEL OF NON-LINEAR ENERGY HARVESTER EXCITED BY A NON-IDEAL ENERGY SOURCE

In this paper the variation of coupling parameters in a vibration model of non-linear energy harvester is analyzed. Increasing in linear and non-linear coupling parameters influenced the output of maximum power harvested. Sommerfeld effect occurs in passage by resonance. The system model is numerically simulated using ode45 of MATLAB.

Proposal of a Nonlinear Piezoelectric Coupling Term to Energy Harvesting Interactions

Nowadays, new technologies have triggered the needs of new energy sources, smaller and more efficient, so the research about energy harvesting has increased substantially. Several researchers have developed the conversion of wasted mechanical energy to electrical energy using piezoelectric materials as a transducer. This chapter proposes a mathematical model for the constitutive equation of a piezoelectric transducer. Experimental results involving piezoelectric elements were considered. The proposed mathematical model allows a considerably better description. The results are closer to those obtained in a real system, reducing inaccuracy of predictive behaviour of the piezoelectric energy harvesting system. In this work, the numerical simulations show a significant difference between results obtained with the proposed model and other models available in literature.

The Use of Wavelets Analysis to Characterize the Dynamic Behavior of Energy Transfer Vibrational Systems

This paper describes the use of wavelet analysis for identification of regular and irregular behavior of dynamical systems. We are focused in single and double-well potential energy harvesting systems that present either periodic or chaotic behavior. To identify the behavior of dynamical systems is of major importance in predicting possible energy harvesting from that system. Using Morlet wavelets, the oscillatory motions of a set of systems were identified with good accuracy. The visualization of the scalograms and global energy spectrum are very useful tools to validate the type of motion found, periodic, quasi-periodic or chaotic. Wavelet analysis can be used to find which amplitude and frequency of operation that generates more energy for each model. Wavelet analysis is a technique used as a tool to assist the validation of the presence of chaos in dynamic systems, together with well consolidated techniques as Lyapunov exponents and Poincare maps.Copyright