Profit of shipping companies depends on the efficiency with which their operations are carried out at the sea. With increase in fuel and operating costs of vessels, ship owners and operators are trying hard to maintain their profit levels.
Efficiency of any ship depends on the quality of its crew and machinery onboard. Of all the machines, the main propulsion plant of the ship is of utmost importance as far as the overall efficiency is concerned.
It is a known fact that no machinery is 100% efficient i.e. when we give 100 % input or supply to run machinery, the output is less than that of the input. This is because of the loss of energy (mainly in the form of heat energy) while doing work.
In this article, we will discuss about five main types of waste energy utilisation systems which are fitted on ships and which use the lost energy from the machinery systems to perform other productive work, increasing the overall efficiency of the ship as a whole.
Turbocharger is a type of super charging equipment which gives excess fresh air to the engine cylinder during combustion. Turbocharger consists of a blower and a turbine assembly mounted on two ends of a shaft. The hot waste exhaust gases from the engine cylinder are directed on the turbine, which rotates the latter.
The rotation enables the mounted blower to suck excess air from the atmosphere and supply it to combustion chamber via cooler. As the quantity of air is increased, the amount of fuel injection can be increased, which in turn will increase the power.
Economiser is a type of boiler which is installed in the exhaust passage of the main engine and where the exhaust heat energy is utilised to generate steam from fresh water.
The exhaust of all cylinders is sent to the turbocharger, where some heat enthalpy is utilized to supply fresh air as discussed above. After passing through turbocharger, the hot exhaust gas with temperature above 300 deg C is passed over stacks of tubes wherein heated water is passed through a forced pump.
3) Steam Turbine Generator
Steam generation on ships is done using boilers and economisers which are provided in all ships. Generally the excess steam is dumped in to a dumping condenser, which is technically a waste storage for steam and energy. This excess steam can be utilised to generate energy when supplied to a turbine generator.
The steam is supplied at a pressure to a high speed turbine which is connected to an alternator shaft. The shaft thus rotates and after achieving a rated rpm, electrical power is generated. To understand how turbine generator works read here.
4) Fresh Water Generator
As the name suggests, the fresh water generator generates drinking water from sea water. The fresh water generator works on the principle that the boiling point of water can be brought down to reduce the pressure of the atmosphere surrounding it. Maintaining a low pressure, water can be boiled at low temperatures say 50 degree Celsius.
This low temperature is provided by the jacket cooling water of the main engine in which a portion of Jacket Cooling Water (JCW) is diverted to Fresh Water Generator (FWG) to produce fresh water. For complete working of FWG read here
5) Shaft Generator
Shaft generator is yet another machinery system where an alternator is connected over the shaft of the main engine. When the main engine is brought to its sea going speed, the shaft generator connected to the main bus bars of the switch board, supplies power to the ship.
This reduces the use of extra fuel in auxiliary generators as they are turned off when the shaft generator is working. To understand the working of shaft generator read here.
Do you know any other important heat recovery system used on ships? We would love to hear about it in comments below.