Mechanical Energy
From Captain of Industry Wiki
Mechanical Energy is a type of energy generated by High-Pressure Turbine[II] and Low-Pressure Turbine[II] that can be turned into electricity by a Power Generator or stored by a Flywheel.
It is transferred by shaft input/output and is NOT dependant on port polarity, which means it is possible to connect the energy receiving Power Generator's output to the input of a Turbine, as long as the "shaft" faces in the same direction.
Shaft has no mediator therefore it is necessary to place buildings sharing the same "shaft" direclty next to each other - connecting their "shaft" ports.