Page 185 - Technology Roadmap Transportation

TECHNOLOGY ROADMAP: TRANSPORTATION

optimization of hull dimensions and form of a new system, thermal heat losses from the exhaust
vessel. gases of the engines can be either utilized for
driving turbines to produce electricity or for
4.2.9 Optimization of energy systems additional propulsion through use of a shaft
Energy systems that have the energy saving motor leading to less fuel consumption by
potential and which ultimately lead to emission the engines. The amount of heat that may be
reduction are discussed below in the following recovered from the exhaust gases is governed
paragraphs: by the type of engines used, the exhaust gas
temperature (allowable outlet temperature of
(a) Engine efficiency improvement: Engine exhaust gas heat exchanger being restricted by
efficiency in its whole range of operation, dew point of acid formation) and the sulphur
may be improved in various ways e.g. content in the fuel.
through design change, de-rating, long-stroke,
electronic injection, common rail injection, It may not be possible to retrofit such systems
two stage turbo-charging, variable geometry into existing ships. However, shipbuilders need
turbo-charging etc. However, the engine to be encouraged to incorporate such new
development is currently dominated by the technologies while constructing new ships at
upcoming requirements of IMO of reducing the design stage itself.
NOx – emissions. This, inherently, will reduce
fuel efficiency, because of lower combustion 4.2.10 Reducing on board power demand
temperatures and increased back pressure (auxiliary system and hotel loads)
as a result of exhaust gas cleaning systems. There are many different ways by which electric
Part of it, if not all potential improvements, power demand on board ships can be reduced.
may be consumed to compensate for the Some of these options are listed below:
effects of NOx – emission control. While a • By encouraging use of lighting appliances
further enhancement of fuel efficiency may be that consume less electricity and are heat
possible through development of diesel engine efficient.
technology, impending legislation suggests that
no overall contribution of the engine sector • By using energy efficient heating, ventilation
to reduce fuel consumption and GHG – and air-conditioning.
emissions from shipping may be possible.
• By using pumps and fans at variable speed
as per actual needs.
(b) Main Engine Tuning: In main engine tuning,
the most commonly used load ranges have • Use of variable speed electric motors for
to be determined and then the main engine control of rotating flow machineries, has
is optimized for operation at that load. This the potential to significantly reduce energy
measure requires a different engine mapping consumption.
for various engine loads and speeds. Further, • In pumping applications with variable flow
specific changes in the engine hardware rate requirements, variable frequency
such as changing the cam profile results in drives (VFD) provide an efficient control
improved efficiency. The fuel injection as well alternative to throttling (valve control) or
as ignition timing can be varied by the use bypass methods.
of anelectronic control units and sensors for
optimum engine performance. This measure • By using frequency controlled variable
can reduce overall fuel consumption although speed pumps instead of fixed rpm pumps
there may be a fuel use penalty under seldom (for cooling water and other systems with
– used full load operations. high utilization rate) substantial reduction in
energy consumption for the pumps can be
(c) Waste heat recovery: Approximately 27% of achieved.
energy produced through combustion of fuel
in main engine is lost in the exhaust heat. The 4.2.11 Energy generation from alternative fuels
basic premise of the waste heat recovery Fossil fuel is likely to prevail as the dominant
process is to redirect and to reuse this source of primary energy for the shipping industry
energy that would be otherwise wasted as of now and in the near future because of its
to the atmosphere or the engine cooling large-scale availability and widespread distribution
systems. With a waste heat recovery (WHR) network. However, environmental/financial

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