Vibration from a Truck Bed
We once had a small development effort to evaluate the potential for harvesting energy from a truck bed to power a monitoring system. There appeared to be some decent energy available but the project didn't go too far due to funding. But it did let me get some pretty cool data!
I mounted a Slam Stick to the bottom of the truck bed and recorded a trip it went on which included highway travel.
Zooming in, there was pretty much always some healthy vibration.
There were also the occasional bumps from engine braking and potholes.
I found this spectrogram especially cool because there was some band of frequency content that was between 200 Hz and 400 Hz. The shape of that suggests it is directly proportional to the truck's speed and/or the engine.
The PSD and FFT
The PSD and FFT data suggest that a vibration energy harvester could potentially work although it would be generating microwatts of power in ideal conditions.