First, let’s agree on the words ‘Free energy‘:
This term has two meanings:
1- system producing energy by itself or perpetual motion;
2- system producing energy from a non conventional source.
If we talk about a free energy device, according to the first meaning, Science considers – rightly – that such a system cannot work.
In contrast, if one speaks of a free energy device, according to the second meaning, such a system can function.
The confusion, voluntary or involuntary, of these two meanings of the term ‘Free energy’ is regrettable. Personally, I prefer to use the words ‘quasi-free energy’; which corresponds to reality.
Much of Tesla’s life was devoted to energy and it took him nearly 40 years to develop a quasi-free energy system. This system has not been patented.
Without trying to feed any conspiracy theory, it is a fact that Tesla had built a prototype of his quasi-free energy system and that it was not among the effects returned to his heir.