Transportation's Role in Reducing U.S. Greenhouse Gas Emissions ...

Transportations Role in Reducing U.S. Greenhouse Gas Emissions: Volume 2
vessels, but has evolved into applications appropriate for larger commercial marine
vessels (Technical University of Denmark, 2006) and has been evaluated by the European
Commission’s BRITE technology program (European Commission, 2002) for larger vessel
applications.
The benefits of improved propeller design are maximized when coupled with control
systems that optimize engine performance based on vessel speed, propeller torque, and
propeller thrust.
Magnitude and Timing of GHG Reduction
Counter-rotating propellers improve fuel efficiency and reduce GHG emissions by 10 to
15 percent (IMO, 2009; Ämmälä, 2006; Wartsila, 2008). Add on devices such as propeller
nozzles can improve fuel efficiency by up to 5 percent (Rice, 2009; Hansen, 2008) while
propeller winglets can improve propeller efficiency up to 4 percent (Technical University
of Denmark, 2006; Lumin, 2005). Because some of these devices address the same drag
forces, combinations of these technologies will not necessarily provide an additive
reduction in fuel use. These technologies can be retrofit to existing ships, though some
configurations of controlled-pitch and counter-rotating propellers are easier to implement
for newly constructed vessels. Adding propeller nozzles and using propellers with
winglets can be implemented at any time. Because propeller technologies are relatively
easy to implement, it is unclear to what extent these technologies are being used in today’s
fleet, particularly with regard to the domestic U.S. fleet; therefore, quantitative estimates
of potential additional GHG reductions are not shown. Counter-rotating propellers are a
relatively new technology and it is likely that their use is not as extensive as controlledpitch
propellers, nozzles, or winglets.
Cost-Effectiveness
All of the propeller technologies discussed in this section are cost-effective for most vessel
operations due to reduced fuel consumption rates. Some of the lower cost options such as
use of propeller nozzles and winglets are particularly attractive to domestic tug and tow
boat operations, providing a pay back period less than two years (Ship Propulsion
Solutions, 2009). While counter-rotating propeller and controlled-pitch propellers are
higher cost options, they also are associated with larger fuel reductions.
Cobenefits
Significant cobenefits are not expected from these strategies, although criteria pollutant
emissions may be reduced in proportion to fuel use.
Feasibility
Many of these propeller technologies are relatively inexpensive to implement and
therefore require little assistance from policy-makers to encourage their use. These
technologies may be promoted through voluntary programs such as the EPA’s SmartWay
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