Technical upgrade and retrofit
One effective way of improving the energy efficiency of a ship is to upgrade ship-board technologies to more energy efficient ones. Upgrading of technologies is not a ship-board activity but nevertheless, the ship-board staff could always engage in proposing such technologies. For this reason, this topic is covered under this section. A number of technology upgrades can be considered for energy efficiency and emission reduction. It should be noted that applicability of such technologies will depend on ship type, ship size, operation profile and other factors (MariEMS 2017).
Devices forward of Propeller: The implementation of the new technologies on board of the ships of new building that bettering the energy efficiency, should be consider for the owner and the maritime administration. A new element to reduce the propulsion power is the MEWIS DUCT, that is a duct fitted forward of the propeller, and this duct drive to the flow of water to the propeller so reduce the power propulsion through of the wake field equalization, reduction of propeller hub vortex and contra rotating swirl, increasing the thrust and reducing the loss of rotational flow. With the fitted of this element it is possible to reduce the propulsion power till 8%. MEWIS DUCT is suitable to biggest ships like tankers that sailing to speed lower 19 knots (MariEMS 2017).
Devices Aft of Propeller: The elements fitted aft the propellers are the Boss cap fin that recapture some of the rotational energy losses. This element is easy to fit and suitable for ships with low speed. With this element can be increasing the propulsive efficiency till 5% and reduce till a 2% the consumption of fuel and therefore reduces emissions (MariEMS 2017).
Ducted propeller: The duct propeller is a nozzle where the propeller is placed and permit a higher and better supply of water inside of propeller, bettering the running of the same and the efficiency between 5-20% and reducing the power propulsion and the consumption of fuel. The only one inconvenience of the duct propeller it is an added device that increase the friction and the resistance to the flow. Other problem is the fouling of the nozzle and the propeller what oblige to higher to clean and maintenance (MariEMS 2017).
Fore-Body Optimization and Bulbous Bow: Another devices to reduce the propulsion power and therefore the fuel consumption are the fore-body that are forward bulbous that are generators of waves that Override the waves that are formed in the forward of the ship and increase the resistance to advance. Fitting this kind of device, it is possible to get till a 5% of reduction of fuel consumption (MariEMS 2017).
Waste Heat Recovery: The main and auxiliary engines exhaust to the atmosphere a big quantity of exhaust gases at high temperature, between 300-450ºC degrees, losing a lot quantity of thermal energy. Part of this thermal energy can be recaptured and used in a waste heat recovery to produce hot water for heating of the ship, and steam for move a steam turbine that move an AC alternator to generate electricity (MariEMS 2017).
High efficiency electric motors: In general the electric motors has a high efficiency, nowadays this efficiency is been bettering, and therefore, it is necessary in the new building ships to select the electric motors of higher efficiency and lower consumption. In the case of the ships in service, all electric motors that need should be replaced should be changed by a new and with higher efficiency (MariEMS 2017).
Fuel oil homogenizers: To take advantage of the fuel should be used a fuel homogenizer that reduce the quantity of sludge of the fuel, and therefore, to burn much more fuel in the boilers and engines. Fuel sludge may constitute up to 1% of fuel used on board. The sludge disposal is normally done either via burning on board (incinerator) or transfer ashore. The whole process is waste of energy and money. Finding ways of reducing sludge thus could be desirable (MariEMS 2017).