When did Nikola Tesla discover free energy?

Nikola Tesla designed his "Power Tower" in the early 20th century as a way to create and provide free energy for the entire planet. Although his idea never came to fruition, he began construction of the tower in 1901.

Tesla envisioned the tower as a way to send electrical energy through the earth without using wires. According to his design, the tower would create the free energy, and small receiving units in each home could tap into this power source to provide all the energy needed. While this concept has never been completely abandoned, not enough is understood about electricity to make it work.