laptops typically require 19 V DC for charging while commercially available peizoelectric sensors generate 10 mV to 100 mV DC per strike. practically voltage output from a peizoelectric sensor can be enough to power an LED. your project concept is amazing. you first need to make an estimate that how much voltage will be generated at the capacitor by an array of sensors placed under keyboard in a short span of time so that on average rate of typing on typical keyboard (which has 107 or 105 keys), what average DC voltage is obtained. That voltage will be needed to be amplified to make a charger circuit for the laptop battery. here 19V is only enogh for 3 and 4 cell laptop batteries. 6 cell or 8 cell laptop battery will require even more DC voltage ffor charging.

I am currently working on project involving piezoelectricity and I'm in need of some advice. I'm pretty much a beginner, but I've been doing lots of research. I just need input to help fill some gaps. The question I’m trying to answer is, “How much energy is produced when piezoelectric elements are placed on top of the keys of a laptop and what percent of the energy required to charge a battery does this represent?”

I’m going to go about answering this by collecting the following measurements:

What is the average amount of energy generated per keystroke on the piezoelectric-equipped key?

How much energy is stored per average keystroke on a piezoelectric-equipped key wired to a capacitor?

How much energy is generated and stored when the same procedure is used but with multiple keys wired in a circuit?

How does this amount of energy compare to the amount of energy required to charge a battery?

My first step will be determining the average energy generated per keystroke by a piezoelectric-equipped key. Next, I will wire an element on 1 key and connect this to a capacitor in order to measure the energy stored under these conditions. I will then link multiple keys with elements to a capacitor in order to see how they function as a unit. From there, I will build an entire prototype with piezoelectric elements embedded with the keyboard of a laptop. At the end of this, I will compare how much energy is generated to the amount of energy needed to recharge a battery to see how much potential there is for recharging it.

Some of my questions are:

What units should I be using to measure “energy”?

How can I ensure that each time an element is struck, it is with the exact same amount of force?

How can I directly compare the number of keystrokes it takes to charge a capacitor to how many it would take to recharge a battery?

What is a good type of battery to compare to given the scale of what I'm working with?

Any general feedback/corrections/advice?

Thank you so much for getting this far, I really appreciate any help :D