The shaft generator on a ship is an excellent example of a waste heat recovery system, which not only utilizes the waste energy from the engine but also supplies the additional work to the propeller shaft when the main engine is underperforming.The shaft generator has two modes of operation:Power Take Off (PTO): The additional energy generated in the main engine is taken off by the shaft generator to produce electricity as an alternative to the four-stroke gen-sets; hence this mode is called PTO or Shaft generator mode.*PTO can improve ship EEDI figuresPower Take In (PTI): Power Take in (PTI) mode provides propulsion power to the shaft which boosts the main engine with temporary extra power. It can also be used as an emergency backup machinery to propel the ship to the nearest shore if the main engine goes out of operation, thereby increasing the redundancy factor. This mode is also known as shaft motor mode.*PTI can deteriorate the EEDI figures if used for increasing the ship’s speed