Have you ever been asked to sign a nondisclosure agreement so you can participate in Beta testing?
Have you ever heard about the shenaniagans surrounding the NiMH battery for the EV1?
This video has interviews with the inventor expressing his disappointment of how things were handled after he sold controlling share to GM. GM did not initially use the NiMH and instead used a inferior battery pack. After the NiMH was implemented and found to be a success GM sold controlling interest to Chevron-Texaco. Why would they buy it and then not produce it?
The video also gets into some debatable conspiracy theories regarding oil and auto companies protecting their interests.
If you want to dismiss conspiracy theories because you simply believe business interests would never do such a thing note that it is documented that GM and other companies were convicted in the "National Lines Conspiracy" of buying control of and then dismantling streetcar and electric train services in 45 US cities.
I can't claim any examples of technological suppression regarding free energy but I also cannot dismiss the possibility.
I'm also not claiming that we will find a way to produce something from nothing, but imagine if you had never heard of photovoltaics, or photons for that matter, and someone told you they could get electricity from the sun.
It's just foolish to think that we have discovered it all. Can you really believe that we are at the zenith of our understanding?
One thing that comes to mind for me is how the Earth has a dynamic magnetic field around it which we can actually measure and observe yet we do not harvest any energy from it even though it actually can move things in our world. Sure the force which turns a compass needle is minute but who has ever been knocked over by a photon?