ENERGY HARVESTING DEVICE FOR POWERING ONBOARD CONDITION MONITORING MODULES IN RAIL SERVICE

摘要

Rail transportation plays an important role in today's economy by delivering a large quantity of goods and passengers to various locations throughout North America in an economic and efficient manner. Bearing failure is one of the leading causes of derailments that result in significant capital loss and in extreme cases tragic human loss. The two widely used bearing health monitoring systems are the Trackside Acoustic Detection System (TADS™) and the wayside Hot-Box Detector (HBD). These systems are reactive in nature and only give alerts when the bearings are nearing failure. To supplant that, a prototype wireless onboard condition monitoring system was developed by researchers at the University Transportation Center for Railway Safety (UTCRS). This onboard wireless system can detect bearing defects at their early stages of initiation so that proactive maintenance actions can be taken by the railroads and railcar owners. Due to the wireless nature of this system, a constant power supply is needed to ensure its continued operation. Currently, the prototype wireless system utilizes low-power circuitry that is powered by a rechargeable AA battery that can provide up to two years of operation depending on usage. Implementation of a suitable energy harvesting device can significantly increase the longevity of the batteries used in the wireless module, and in ideal operating conditions, generate consistent energy rendering the battery as a temporary energy storage device. The proposed energy harvesting device consists of thermoelectric generators, aluminum heat sinks, a switching boost convertor, and a battery management chip. This device was tested on a dynamic bearing test rig to assess the performance of the thermoelectric generators. To best simulate field operation conditions, the thermoelectric generators were placed on opposite sides of the bearing adapter; one exposed to direct forced convection while the other side is shielded by the adapter and experiences minimal convection. Thermoelectric generators were found to be an effective solution due to their ability to convert a temperature gradient into a usable voltage sufficient to charge the battery. The buck booster converter increases the voltage from the thermoelectric generators to 5-volts so that the battery management chip can regulate the voltage and efficiently charge the battery. This paper summarizes the performance of the thermoelectric modules under different operating conditions. The main goal of this project is to devise an energy harvesting device that allows the wireless module to be self-powered utilizing the heat generated from the bearing and the charge held by the battery as a hybrid power source.