Monitoring freight trains along their journey remains an obstacle for the industry, especially when electrification of the infrastructure is not present. However, a new Chinese study is proposing a solution for energy self-contained systems to power tracking devices through energy produced by the trains themselves.
The system entails “a cooperative system of wind and vibration energy harvester that exploits train-induced airflow and track vibrations to generate electrical energy”. The electricity generated by wind and vibration is AC power, which the device can convert into more stable DC supply.
In simpler words, the airflow and vibrations created by freight trains can be stored and converted into energy which would then power monitoring devices installed on the trains. This makes it possible to keep track of train composition, the conditions of wheels and the state of the tracks even in those areas where electricity is not immediately available, the study argued.
How well does it work?
The tests run by the authors of the study showed some promising results. In a situation of airflow at 10 metres/second, with peak outputs of 40.87 mW. For the vibrations, they were set at a frequency of 20 per second with an amplitude of five millimetres, which are roughly the conditions of a freight under normal circumstances. This second method of harvesting energy is more time consuming and has a lower output than wind, with peaks of 26.21 mW.
When it comes to harvesting energy from the airflow created by the freight train, the storage unit is charged in 20 hours. On the other hand, charging time for the storage unit through vibration-produced energy was measured at 45 hours. Both charging times suggested in the study include the simultaneous powering of the monitoring devices. “The results indicate that the proposed system can harness multiple ambient energy sources to deliver stable and continuous power under variable conditions”.
Three requirements
Self-contained systems for rail freight would need to meet three requirements: diversified energy harvest, a compact design and simple deployment and maintenance tasks. The system proposed and tested by the Chinese study, led by the State Key Laboratory of Advanced Rail Autonomous Operation at Beijing Jiaotong University, seems to meet all of them.
The diversification of energy harvesting was ensured by using both vibration and wind to power the monitoring devices. The devices to install on the trains have a “miniaturised and lightweight design that facilitates installation”. And finally, the system also comes with an external shield that protects the internal components deployed for the energy harvesting and production.