The piezoelectric effect is a fascinating thing limited in usage. It will produce High voltages but not high current.
Voltage is “potential” Current gets things done.
We typically use the inverse of the piezoelectric effect, applying voltage to a crystal to cause it to oscillate as a clock, because it is far more useful to take advantage of this phenomena than it is to apply pressure to the crystal in order to produce voltage.
The idea that we can use crystals for serious production of energy is shocking
Piezoelectrics are also used in those portable propane torches, of the type that Burnz-O-matic makes.
They have a finger operated trigger connected to an impeller so that when you press it down the impeller will strike a piezoelectric crystal, the voltage produces a spark in the nozzle of the torch which lights the propane. All the energy to light the torch comes from your finger pressing down on the trigger. With no batteries, the lighting mechanism will last virtually forever.