After researching a lot on word "piezoelectric" , I think that your question can just be answered by the usual concept of "efficiency". So in this case when we hit "piezoelectric quartz" with hammer with the kinetic energy of 100 joules, we will probably get less than
100 joules of "electrical" energy out of the quartz. This is because no object is 100% efficient. Some of the kinetic energy is used up in vibrating the molecules and internal resistance , etc... I CANNOT say exactly how much less can be obtained (that depends on experimentation now ).