Milan, I am not sure which Piezo sensor will give you the best results, but i did find some links that may help you once you find your energy harvesting system:
http://newscenter.ti.com/2013-11-18-Ultra-low-power-circuits-to-enable-next-wave-of-energy-harvesting-design
http://www.ti.com/ww/en/analog/power_management/energy_harvesting/
http://www.edn.com/design/power-management/4422103/Fast-charging-a-supercapacitor-from-energy-harvesters
I hope that some of these can help you once you find your sensor solution.