Design and Modelling of an Energy Aware Dynamic Management for Wireless Sensor Node with Dual Harvesters

Wireless Sensor Network (WSN) consists of a large number of spatially distributed low-power autonomous nodes equipped with sensors to cooperatively monitor the environmental conditions. The limited battery lifespan that is being used by a sensor node is the major bottleneck that restricts the extension of WSN application for its scalability and sustainability. Thus, the energy consumption efficiency remains the most prominent design criterion that need to be addressed urgently. There are two main research concerns on the energy-harvesting powered WSN, firstly is to reduce the node power consumption and the, secondly is to increase the harvesters' power to meet the minimum requirement of the node power consumption. In another word, it is to reduce the mismatch of the supply and demand of the node electrical power. Thus, an energy aware dynamic management model for wireless sensor node powered by dual harvesters is presented to deal with the mismatch. The first step of the research is to investigate the node power consumption profile. This is followed by investigating the electrical power supplies which are based on thermoelectric and piezoelectric as Hybrid Energy Harvesting (I-EH). The node is designed with a built-in main and backup energy storages to overcome the HEH energy gap issue. It features fast start up using a small capacitive energy storage as the main instantaneous power source. Whilst for wider energy gap coverage, a larger capacitance is used as the backup energy storage. To reduce the power consumption while not compromising the integrity of the signal transmission, the sensor node is improved with a novel energy-aware Event-Priority-Driven Dissemination (EPDD) algorithm. It is developed to make the sink station able to detect a missing node within the network. The function of the algorithm is to detect the energy sources availability and control the nodes' sleeping period accordingly. The empirical power profiling for each node and at system level were measured during active and sleep modes, which provides a useful data for designing low-power wireless sensor node. The node is designed and modelled using Matlab Simulink 2016 environment. The simulation results show an improvement in the node start-up time of less than 30s only with 48 hours of energy gap coverage, which is theoretically long enough to ensure that the node stayed active until the next phase of ambient energy to be available again. The experimental results are in good agreement with the simulation model. It is also found that the RF transceiver consumed the highest power of 24mW, followed by the microcontroller with 7.5mW and the sensor module with O. 16mW throughout the active period. During the sleep period, however, the microcontroller consumed a noticeable amount of power of 1.8mW compared to the other sensor node components. Moreover, it shows that energy at ideal cases where both energy harvesters, I-EH are operating at the same time, a power in the range of around 90 mW is generated which is more than enough to achieve the minimum requirement to operate a sensor node

Impact-Driven Energy Harvesting: Effect of Stress on Piezoelectric Bender

This research is experimentally characterized and evaluates the effect of stress on a piezoelectric transducer by employing different bending mechanism. Three forms of bender: flat, unstressed, and pre-stressed are being investigated for their maximum electrical charge generation subjected to the applied stress. These mechanisms were fabricated using 3D printer where the piezoelectric beam can be inserted in to maximize the applied stress onto it. Variable impact forces are being exerted to bend the piezoelectric transducer for generating an electrical power across its terminals when connecting to an external load. In this respect, a rectangular shaped piezoelectric transducer with the size of (70X32X0.55) mm manufactured by Piezo System utilized to empirically study the relation between the impact force and the electrical output from the proposed piezoelectric bender. From the experimental results, the instantaneous AC volt output at open-circuit improved gradually and reached saturation of 10VAC, 50 VAC, and 70 VAC for flat, unstressed, and pre-stressed piezoelectric bender respectively. It is also found that the output power increases from 4mW of that recovered by using a flat mechanism to a double when using that an unstressed bending mechanism, while under the condition of pre-stressed, the electrical power further increases to 53mW at the same impact force

Evaluation of Impact Based Piezoelectric Micro-Power Generator

This paper reports on energy harvesting from a mechanical impact by using a piezoelectric micro-power generator. An useful electrical power is generated when the impact of a human weight is applied on a piezoelectric disk transducer. An experimental set-up of a single foot step on piezoelectric disk for harvesting the impact energy was being conducted with variable forces and impact velocity. A 44mm diameter and 10mm thick of piezoelectric disk is sandwiched between two wooden plates to be used for transforming impact from foot step into electrical energy. A range of output power of 3.8μW up to 14.5μW was measured across a variable resistive load of 10kΩ up to 1110kΩ respectively for a single foot stepped onto the device. In another experiment, a varying of impact velocity is being applied to the piezoelectric micro-power generator

Application of Piezoelectric Energy Harvesting in Powering Radio Frequency (RF) Module

A radio frequency (RF) transmitter node powered with a cantilever based piezoelectric energy harvester is presented in this paper for wireless sensing applications. The piezoelectric cantilever (energy harvester) is tuned to its resonant frequency at around 290Hz, generates electrical output power from 29.5μW up to 0.57mW when driven with vibration excitation of acceleration levels of 0.01g and 0.019g respectively at resonance with external electrical load of 80kΩ. A shaker was used as a vibration source for the piezoelectric cantilever to simulate the vibration energy that can be found at many of household as well as industry appliances. An interface/power conditioning circuit with energy storage is used to accumulate the electrical energy generated from piezoelectric and then supply to power the RF transmitter node to transmit a chunks of data varies from 1 up to 10 Bytes at a certain times generated via a MCU to an RF receiving node at about 2.5m apart. The RF transmitter module was turning on for around 47 up to 102ms for each time transmitting 1 up to 10 Bytes respectively and then will be deactivated for a certain time varies from (2.5, 5, 7, and 10) second

Characterization Of Thermoelectric For Energy Harvesting On Low-Level Heat Sources

Electric power harvesting from thermal energy using thermoelectric (TE) has been getting popular as a potential electrical energy source to replace batteries due to its direct current output. The focus of this paper is on the investigation of low level thermal energy below 150C that generated from electronic devices and mechanical machinery, and using TE’s to convert the heat energy, which normally treated as wasted energy into a useful amount of electrical power to power up portable low power electronic devices. For this study, the TE module is subjected to a range of heat source using heating element that resemble the real temperature that generated from the real electronic devices and mechanical machinery. The quantity of harvested electrical power was reported. From the experimental results it can be observe that the voltage output is linearity proportion to the applied heat gradient on the TE faces. At a temperature gradient of 60 C, a voltage output of 4 V is measured. The voltage output can be increased by stacking the TE on top of each other, from 0.067V/ C for 1 TE to 0.093V/ C for 4 TE

Piezoelectric Pre-Stressed Bending Mechanism For Impact-Driven Energy Harvester

This paper experimentally demonstrates and evaluates a piezoelectric power generator bending mechanism based on pre-stressed condition whereby the piezoelectric transducer being bended and remained in the stressed condition before applying a force on the piezoelectric bending structure, which increase the stress on the piezoelectric surface and hence increase the generated electrical charges. An impact force is being exerted onto bending the piezoelectric beam and hence generating electrical power across an external resistive load. The proposed bending mechanism prototype has been manufactured by employing 3D printer technology in order to conduct the evaluation. A free fall test has been conducted as the evaluation method with varying force using a series of different masses and different fall heights. A rectangular piezoelectric harvester beam with the size of 32mm in width, 70mm in length, and 0.55mm in thickness is used to demonstrate the experiment. It can be seen from the experiment that the instantaneous peak to peak AC volt output measured at open-circuit is increasing and saturated at about of 70V when an impact force of about 80N is being applied. It is also found that a maximum power of about 53mW is generated at an impact force of 50N when it is connected to an external resistive load of 0.7KΩ. The reported mechanism is a promising candidate in the application of energy harvesting for powering various wireless sensor nodes (WSN) which is the core of Internet of Things (IoT)

Impact Based Piezoelectric Energy Harvesting: Effect of Single Step’s Force and Velocity

This paper reports an impact driven energy harvesting via employing a piezoelectric ceramic disc, in which a usable alternating electrical energy has been harvested via the mechanical impact of the human weight on the surface of a piezoelectric plate transducer. A prototype of a single human step piezoelectric plate impact driven harvester consisting of a piezoelectric transducer disc was tested on a hydraulic pressing machine with variable forces and impact velocities. In this experiment, a piezoelectric ceramic disc with a size of pallet 44mm in diameter and 10mm in thickness was able to transform the mechanical impact into an average output power of up to 14.5μW across a resistive load of 500kΩ, when a force of 0.75 kN with a velocity of 600mm/min is applied on i

Hybrid Energy Harvesting Scheme Using Piezoelectric and Thermoelectric for Wireless Sensor Nodes

This paper presents an evaluation of the effectiveness of a hybrid energy harvesting scheme for WSNs applications. Unlike common energy harvesting approaches that utilize a single microgenerator harvesting from a single source of energy, this hybrid scheme harvesting two energy sources which are ubiquitous from the ambient environment which are heat and vibration. The novelty of this work lies in the hybrid topology of an AC microgenerator and a DC microgenerator combined as a single energy harvester, where it will increase the chance of survivability of wireless sensor nodes. From the experimental result, it shows that the wireless sensor node powered via the hybrid energy harvester is able to survive in an environment where there are lack of mechanical vibration or heat emissions. Moreover, the study on the time required to fully charge an energy storage element is also presented with a 15mf-16v capacitor by an electrical input of 5V with two different topologies of the harvesters which are arranged in parallel and serial

Event Priority Driven Dissemination EPDD Management Algorithm For Low Power WSN Nodes Powered By A Dual Source Energy Harvester

This paper proposes a low-power wireless sensor node which is able to deal with energy harvesting mismatches. The hardware incorporates thermoelectric and piezoelectric transducers for a dual energy harvester, energy storage, microcontroller, sensor and wireless transceiver. The software incorporates an energy-aware Event-Priority-Driven-Dissemination algorithm to send data based on priority or event occurrence. This algorithm serves both to detect the availability of the energy source and to control the nodes’ sleep mode. The outcomes revealed that the hardware power was 0.16 mW and 2.13 mW in sleep and active modes respectively. Also, energy autonomy was comfortably achieved since the dual harvester energy was 90 mW when both sources were availabl

Finite Elements Method Simulation of P(VDF-TrFE) Piezoelectric Sensor for Internet of Things Application

This paper presents finite element method (FEM) simulation and internet of things application by using P(VDF-TrFE) piezoelectric sensor where there are mechanical vibration present on the piezoelectric material for batteryless sensors. Therefore, this simulation was conducted using COMSOL Multiphyisc 5.1 to study the resonance frequency, stress, displacement and load dependence for the P(VDF-TrFE) piezoelectric sensor. The optimized design of P(VDF-TrFE) piezoelectric sensor was tested in the step monitoring application by using the internet of things (IoT) system