Energy harvesting solutions for railway transportation: A comprehensive review

Railways, as one of the most important forms of transportation, have been developed rapidly throughout the world. Meanwhile, the energy consumption and carbon emissions of railway transportation are noticeable in face of global climate changes. The increasing speed of railway brings higher requirements for safety and reliability, resulting in the continuous growth of the demand for the monitoring system. In scenarios without economic access to electrical power supplies, seeking energy harvesting for self-powered monitoring or other track-side electrical system is an effective way to reduce operation and maintenance costs. Fortunately, the last decade has witnessed significant advances in energy harvesting technology, which provides new opportunities for a green and intelligent railway. The vehicle-track system is surrounded by multiple energy sources, including vibration, wind, solar, thermal, magnetic field and acoustic energy, all of which can be used for energy har-vesting. Given the increasing interest in energy harvesting solutions in railway transportation, herein we present a comprehensive review of the research progress and representative works. The design and realization of energy harvesters for railway applications are surveyed in detail. On this basis, different types of harvesters are sum-marized and compared, and their application prospects are discussed. Moreover, the technical challenges of vibration energy harvesters including performance enhancements, coupling dynamics with the railway system and interface circuits are stressed. Finally, some suggestions are given to better fill in research gaps in future directions.