Engineering Institute Corrosion-Enabled Powering Approach for Structural Health Monitoring Sensor Networks Scott A. Ouellette, David Mascareñas, Michael Todd (advisor) Results Sensor Node Architecture Structural health monitoring consists of an integrated paradigm of sensing, data interrogation (feature extraction), and statistical modeling that results in a strategy to assess the performance conditions of a structure. Clearly, sensor networks play a central role in this paradigm, as such networks typically perform much of the data acquisition, information management, and even local computing necessary to enable the overall functionality of the strategy, increasingly in a wireless mode. In many applications, particularly in remotely located civil or mechanical infrastructure, power provision can become a limiting factor. The usual powering strategy for wireless networks is a battery, but batteries require replacement, as their useful shelf lives often do not exceed the intended service of their host structures (e.g., decades). Energy harvesting has emerged as a class of potential network powering solutions whereby one form of energy available on the structure (e.g., thermal, solar, mechanical) is harvested and converted to useful electrical energy. The objective of this work is to investigate the harvesting of energy from galvanic corrosion that typically occurs naturally in many structures. Specifically, this study considers corrosion between magnesium and graphite rods embedded in a concrete structure immersed in seawater. The energy was evaluated by connecting a.1F capacitor and measuring the voltage charge over time (during the corrosion process). A carbon fiber admixture was introduced to the concrete host to improve electrical conductivity, and the power increase was calculated from voltage measurements. The batteries were connected in parallel to a 50F capacitor, and a linear gain was observed. The investigation concludes that the voltage levels achieved (~1.5V) may be naturally integrated with a booster circuit to provide CMOS voltage levels suitable for sensor network powering in some applications. Abstract Structural Health Monitoring Paradigm Experimental Setup 1V Concrete Battery Integrated Voltage Booster Circuit 3.3V THINNER Sensor Node Ambient Active Filtering/Noise Reduction State-Space Embedding FRF Mode Shapes Prediction Error Wavelets Kolmogorov-Smirnov Distance Distribution + Threshold Kurtosis/Variance Excitation Structural Response Conditioning Feature Extraction Statistical Comparison Metric Conclusions & Future Work Concrete Batteries have a high potential for providing energy to low-power sensor nodes. Develop and test a boost converter circuit. Test long-term durability of concrete batteries. Experiment with carbon fiber tow lengths to optimize battery power / voltage output. Energy from corroding batteries power 4F super- capacitor connected to voltage threshold switch. Voltage provided by concrete batteries is boosted to 3.3V and filtered through another threshold switch with a 2.7V cut-off. Once voltage on 4F super-capacitor reaches minimum threshold of 1V, energy is released to boost converter. Concrete batteries are immersed into continuous supply of seawater to utilize chloride ions. Seawater serves as the electrolyte for the galvanic cell, and a fresh supply is vital for the electron flow. The data was acquired by connecting the batteries to an Agilent Digital Multimeter remotely accessed by a laptop computer. Agilent Intuilink data acquisition software was used with Microsoft Excel to gather time-series values for voltage charge on varying capacitors for each battery type. Raw data was then processed using MATLAB. Voltage Comparison Charging.47F Capacitor Connected in Parallel Minimum voltage for boost converter Voltage data was collected from the 4 types of batteries created. The Magnesium / Graphite (Mg/Gr) performed better than the Aluminum / Graphite (Al/Gr) as expected. Note: addition of a carbon fiber admixture (wCF) boosted the power of both types of battery. The best battery from the voltage test was then compared to a control battery (I.e. no concrete). The power of each battery was calculated at approximately 1mW. Finally, the 3 Magnesium / Graphite (wCF) batteries were connected in parallel to see if a linear gain could be achieved. The total power was calculated as 3.3mW as predicted. E = 0.5*C*V 2 Energy Harvesting and Data Collection Typically structural data is collected with a wireless network. Oftentimes a large number of sensor nodes are placed in dificult to access locations (I.e. underwater pilings, ship hulls, ballast tanks). Solar energy harvesting techniques are unsuitable for marine structures such as pipelines, levees, dams, oilrigs, and piers. The sensor network should have a maintenance- free lifetime equal to that of the structure. Why not harness the power of corrosion? Magnesium Rod (anode) Graphite Rod (cathode) Concrete Cylinder / Porous Barrier Seawater Line V