Is it possible to generate power from the cosmic microwave background radiation? The idea is building something like wireless charger
but source signal comes from CMB.
 A: Its temperature is only 2.7 kelvin. Anything else in nature is warmer. So the answer is no: it would violate the second law of thermodynamics.
@DilithiumMatrix asked for more explanation. I referred to the second law as in a Clausius-like form: "It is not possible for heat to flow from a colder body to a warmer body without any work having been done to accomplish this flow." 
So it costs energy to extract energy from the cosmic background. For the same reason as a ship cannot take thermal energy from the sea for propulsion.
A: I propose a way in which it might be possible to get power from the Cosmic Microwave Background, but it is probably beyond our current capability.  First, get your speed relative to the Cosmic Microwave Background up to something like 99% the speed of light (possibly even closer).  At some point, the incoming radiation ahead of you should then be blueshifted to the point where it produces a temperature like that experienced on Earth (and if you go much faster than that, you would burn up).  At this point, the part of the CMB behind you should be extremely redshifted, and produce even less than the 2.7K (not that this part would matter much).  
At this speed, the front end of an object should be heated, and the back end should be cooled (or rather radiate away almost all its heat).  I propose that this heat difference could be used to extract energy from the Cosmic Microwave Background using something like a Stirling engine, or perhaps even something like solar panels.
Usually, perpetual energy schemes like this don't work, but you aren't getting something from nothing in this case.  You would be extracting energy from the Cosmic Microwave Background radiation I believe. I invite people to point out anywhere this might be flawed, and / or study this idea further.  It is possible that extracting this energy would somehow slow you back down, and you would really be extracting energy from your speed relative to the cosmic microwave background, instead of from the cosmic microwave background itself.  If my proposal does work, it would seem to be a great potential power source for interstellar travel!
