Three Ways to Reduce Shipping's Carbon Footprint
By Jonathan Childs of GE Power Conversion
Reducing carbon emissions and fuel consumption is a major priority for the marine industry. According to the International Maritime Organization (IMO), shipping is a modest contributor to overall carbon dioxide (CO2) emissions as a method of transport. It emits about a tenth of emissions compared to the trucking industry and a thousandth of that from aviation, in terms of carbon emissions per ton per mile.
However, the sheer scale of the international shipping industry in comparison to these other modes of transport means that overall CO2 emission remains high. The most recent report from the IMO found that international shipping alone represents roughly 2.7 percent of global man-made CO2 emissions – almost the same as that emitted from the aviation industry.
As a result, organizations such as IMO are making strides to try to cut emissions in the shipping industry. For example, amendments to the MARPOL Convention in 2011 led to new regulations across the shipping industry, aimed at cutting CO2 emissions by 20 percent by 2020. These efforts are not limited to the private sector either; governments are increasingly attempting to cut down emissions across their navies.
Here, I have identified three key ways offshore, merchant and naval fleets can reduce their carbon footprints.
1) Installing electric power and propulsion systems
Electric power generation and propulsion is an essential factor in reducing carbon emissions, particularly on vessels with diverse operating profiles. This is because the more efficient electric motors and the variable speed operation of the propulsors can dramatically reduce fuel consumption. Ships using efficient electrical propulsion system consume less fuel and release fewer greenhouse gases to transport the same tonnage as mechanically driven vessels. Production of electrically propelled vessels has increased dramatically since 2004. In fact, in 2012 over 160 electrically propelled vessels were built.
As well as building ships with new electrical propulsion technology, there is an opportunity to upgrade the systems on vessels already in use. For example, the US Navy’s amphibious assault ship USS Makin Island upgraded its power generation to a GE hybrid electrical and gas propulsion system and estimated savings in excess of $15 million in fuel in its 7-month maiden deployment. The U.S. Navy, anticipates lifetime fuel savings in the order of $250 million.
It may also be necessary for some vessels to upgrade antiquated electrical systems. Electric motors have been on marine vessels since 1903, after all. In 2011 nearly 28, 000 merchant marine vessels were over 25 years old, and a further 15,000 are 15-24 years old – together more than 25 percent of the global fleet. Many of these old fleets will benefit from more modern and efficient electrical systems.
2) Upgrading core systems on existing vessels
First introduced in the 1960s to assist offshore drilling, dynamic positioning (DP) is now used in a wide range of vessels for different outcomes. Indeed, DP is no longer limited to maintaining a fixed position; it can also be used to ensure that a vessel sails on an exact track, which is useful for underwater construction or pipe laying for instance. Traditionally, dynamic positioning systems were fuel costly because it takes a lot of energy to keep a large vessel completely still, particularly on choppy waters.
However, there are several innovations which are being made across the industry to reduce the fuel consumption of DP systems. For example, new GE Power Conversion DP technology comes with an Energy Efficient Mode, which uses predictive software to anticipate position variation and therefore limit thrust changes when trying to keep a vessel still.
Other novel ways to further reduce carbon footprint whilst at the same time reducing equipment wear and tear and the frequency of machinery maintenance are also being considered. They include improving the control strategy, closed ring operation, energy storage and variable frequency generation. With all of these measures in place, this technology can save operators up to 10 percent in fuel usage which over time can significantly reduce a ship’s carbon footprint.
3) Streamlining hull and propeller design
Another measure ship builders can take to reduce carbon emissions is to streamline the design of ships so they can move faster in the water without using as much fuel. Hull form optimization is one route to reduce drag and streamline vessels, made possible by advances in technology that enable equipment usually stored in the hull to be rearranged.
The integration of GE’s compact podded thruster design, Inovelis, for example, can expect to yield fuel efficiency gains of up to 10 percent depending on the ship’s size and operational profile. Based on pump jet principles, it features fixed stator vanes and a nozzle that act together to guide the water flow across the impeller blades, substantially enhancing propulsion efficiency. The advantage of this type of design is so significant that it gives ship designers the potential to streamline aft hull shape and reduce capacity power plant – fewer number of cylinders or smaller engines - when designing offshore vessels.
Similarly, other innovations in propeller design can also save fuel. For example, a MAN Diesel & Turbo retrofit propeller installed recently on a Great Eastern Shipping vessel is expected to save the vessel 4 percent in fuel. These figures may not seem much, but when you consider the size of vessels and how much fuel they consume, it’s innovations like these that will propel the industry into a more fuel-efficient future.