Browsing by Subject "Energy harvesting"

Now showing 1 - 3 of 3
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    Improved Approach to Enforcement of Road Weight Restrictions
    (Minnesota Department of Transportation, 2013-11) Alexander, Lee; Phanomchoeng, Gridsada; Rajamani, Rajesh
    This project focused on the enhancement and evaluation of a battery-less wireless weigh-in-motion (WIM) sensor for improved enforcement of road weight restrictions. The WIM sensor is based on a previously developed vibration energy harvesting system, in which energy is harvested from the vibrations induced by each passing vehicle to power the sensor. The sensor was re-designed in this project so as to reduce its height, allow it to be installed and grouted in an asphalt pavement, and to protect the piezo stacks and other components from heavy shock loads. Two types of software interfaces were developed in the project: a) An interface from which the signals could be read on the MnDOT intranet b) An interface through a wireless handheld display Tests were conducted at MnRoad with a number of test vehicles, including a semi tractor-trailer at a number of speeds from 10 to 50 mph. The sensor had a monotonically increasing response with vehicle weight. There was significant variability in sensor response from one test to another, especially at the higher vehicle speeds. This variability could be attributed to truck suspension vibrations, since accelerometer measurements on the truck showed significant vibrations, especially at higher vehicle speeds. MnDOT decided that the final size of the sensor was too big and could pose a hazard to the traveling public if it got dislodged from the road. Hence the task on evaluation of the sensor at a real-world traffic location was abandoned and the budget for the project correspondingly reduced.
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    Novel Battery-Less Wireless Sensors for Traffic Flow Measurement
    (Center for Transportation Studies, University of Minnesota, 2008-11) Vijayaraghavan, Krishna; Rajamani, Rajesh
    This project presents a novel battery-less wireless sensor that can be embedded in the road and used to measure traffic flow rate, speed and approximate vehicle weight. Compared to existing inductive loop based traffic sensors, the new sensor is expected to provide increased reliability, easy installation and low maintenance costs. The sensor uses power only for wireless transmission and has ZERO idle power loss. Hence the sensor is expected to be extremely energy efficient. Energy to power this sensor is harvested entirely from the short duration vibrations that results when an automobile passes over the sensor. A significant portion of the project focuses on developing low power control algorithms that can harvest energy efficiently from the short duration vibrations that result when a vehicle passes over the sensor. To this effect this report develops and compares three control algorithms “Fixed threshold switching”, “Maximum Voltage switching” and “Switched Inductor” for maximizing this harvested energy. The novel “Switched inductor” algorithm with a dual switch control configuration is shown to be the most effective at maximizing harvested energy. All three of the developed control algorithms can be implemented using simple low power analog circuit components. The developed sensor is evaluated using a number of experimental tests. Experimental results show that the sensor is able to harvest adequate energy for its operation from the passing of every axle over the sensor. The sensor can reliably and accurately measure traffic flow rate.
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    Wind generated electricity using flexible piezoelectric materials.
    (2010-10) Morris, Dustin Lee
    Wind generated electricity using thin, flexible sheets of piezoelectric materials attached to flag like membranes termed bimorphs is presented. Piezoelectric wind generated electricity presents a simple, yet effective means to extract energy from the environment. The harvested energy would most likely be used to power wireless sensor networks and other low power applications where batteries would normally be used. Replacing batteries is inconvenient for the users of wireless sensor networks and consumers of other low power electronics. Recharging batteries with power extracted directly from the ambient eliminates the need for frequent battery replacement. Bimorphs are constructed with piezoelectric materials such as poled Polyvinylidene Fluoride (PVDF) and Lead Zirconate Titanate (PZT). Various thin, flexible polymers such as overhead projector film or ink jet transparency film make up the substrate. Several adhesives are researched to determine which can withstand the high strain levels over long periods of time. Bluff bodies were used to create vortex shedding; to increase the undulation amplitude of the bimorph and overall efficiency of the piezoelectric energy harvesting system. Due to the low source capacitance of piezoelectric materials and the low oscillation frequency of the bimorph, the source impedance is very high. In order to reduce the source impedance of the bimorph (increase output current), an inductor must resonate out some or all of the reactance of the piezoelectric. However, thousands of henries of inductance would be necessary to have a vast impact on piezoelectric source impedance. Hence, a quasi-resonant rectifier switching circuit is employed to reduce the source impedance of the bimorph. An energy harvesting circuit termed ‘Series Synchronized Switch Harvesting on Inductor’ (SSSHI) is implemented in order to maximize AC to DC power flow from a piezoelement bimorph to a storage capacitor. The circuit comprises of a peak-triggering circuit, inductor, switch, and regulated micro-power step-down converter powered directly from the piezoelement.