Answer:
The second law of thermodynamics.
Step-by-step explanation:
The global transfer of energy from fuels to electricity is about 35% efficient is most likely a consequence of the second law of thermodynamics. This second law states that as energy is transformed more it is wasted, also that the entropy of a system remains constant or increase, but never decrease over time. That is why is impossible to convert heat energy to mechanical with 100 % efficiency.
Therefore, in the production of electricity, a minor part of chemical energy (from fuels) will be transformed into energy and the rest will be lost to the environment, mostly as heat, to satisfy the second law of thermodynamics.
I hope it helps you!