Piezoelectric speaker element generates electricity

See how you can generate electricity with a simple piezoelectric element - a piezo electric speaker can be used to generate quite a lot of electricity, even one single element, mine created up to 3 volt, and could deliver about 2 mA. Now - Imagine an entire cluster of piezoelectric elements like this, and you could virtually generate power from people walking on them...if you carpeted your entire floor with it. ... https://www.youtube.com/watch?v=s3Ftl6n9Oq0