... It looks amazing, but the amount of mechanical energy that a person involuntarily expends when pushing the button on a calculator, exceeds the amount of electrical energy required to energize electrical circuit of this device by at least 10 times!

Therefore, there is no need to use traditional batteries or solar cells to power up calculators!

It has been discovered that small electric charge generated in a spark from a simple mechanical piezolighter can provide all necessary energy for those calculators.

... It also appears that many other various electronic devices could work without batteries ...
                                ...just push the button or turn the lever...