Emission Reduction: Tangible Benefits To Ships & The Environment

International shipping is regarded as the most carbon efficient means of transporting goods worldwide. Still, the industry accounts for some 3% of global carbon dioxide emissions. Norwegian companies are looking at new ways to reduce emissions and in the future attain carbon neutral growth.

Det Norske Veritas (DNV) believes that the industry can do a lot already now. The Norwegian classification company says the existing fleet could potentially reduce air emissions by 15% just through better operational practices using current technology. Ships can achieve this by optimizing engine performance, the trim for all drafts and speeds of the propulsion system efficiency, and improving voyage management.

DNV plans to help the maritime industry achieve these environmental goals by helping it measure its success. The company recently developed a set of abatement curves that plot the achievable emissions reductions against the estimated cost effectiveness. The new tool, the DNV Triple-E (Environment & Energy Efficiency Rating System Scheme), lets owners and operators set targets, monitor improvements, and document their success. The system can also demonstrate green performance to meet charters’ demands and help improve the bottom line by reducing fuel cost.

“Triple E is more than a rating system, although it does provide an auditable ranking of green performance,” said Tor Svensen, DNV Maritime Chief Operating Officer. “Our intention is to provide this as a tool to bring tangible benefits to ships and to the environment.”

“When looking into the future and taking into account that further reductions can be achieved by new technologies, I am convinced that the shipping industry will be able to attain carbon neutral growth,” he added.



 
There are substantial energy savings potentials and environmental benefits by using efficient HVAC systems.
© Marit Hommedal/Statoil



Operational & Technical Measures

There are two ways the industry can reduce emissions. One is through operational measures, such as cargo utilization, speed and routing. Wilh. Wilhelmsen, for example, has installed weather routing systems on board its vessels for more efficient route planning and safe sailing. The Norwegian shipping company is also currently testing an energy management test installation that helps crews optimise sailing conditions (speed, trim and energy consumption). It is part of Wilhelmsen’s goal this year to reduce its total fuel consumption as measured in g/tonnes/km by 4% compared to 2008.

The other way is to cut emissions through technical measures, i.e. hull design, propulsion system and engines. Örjan Götmalm, Wilhelmsen Marine Engineering Director for Innovation, believes the “low hanging fruits” are the savings from modifying heating ventilation and air conditioning (HVAC) systems.

In many ships, HVAC is the third most important system on board for people, machinery and precious cargo. Since the typical demand for air conditioning is often less than 50% of maximum capacity, there are substantial energy savings potentials as too often the HVAC system is inadvertently run "full blast with the hand brake on" all the time because little focus is directed towards lean HVAC operation.

“HVAC accounts for one third of energy use on a large passenger ship, so it’s not just about propulsion or hull shapes,” said Götmalm, speaking at Oslo Maritime Network’s seminar in October on ship energy efficiency.

A very common cabin HVAC system used on passenger ships is a single duct variable air volume (VAV) system that ventilates and controls the temperature in each cabin. One dilemma with this system is that if one air terminal device (ATD) increased the amount of air supply to a cabin, the adjacent ATD would suddenly be starved of air. This in turn required that the system operate on overcapacity where the excess supply air pressure would be throttled away in the ATDs, which is a pure waste of energy.

Wilhelmsen Marine Engineering has developed an ATD that compensates for varying duct pressure so that the correct airflow is always supplied to the cabin. This improves climate control and reduces energy consumption. This technology has been packed in a system called CabiNet and used in Aida Cruises’ new building series of five cruise ships. In this case, the CabiNet system is paid back in energy savings in less than two years at a fuel oil cost of USD 450 per tonne.


 
Tor E. Svensen, DNV Maritime Chief Operating Officer, belives that shipping will be able to attain carbon neutral growth in the future.
© DNV/Nina Rangøy, Nina Rangoy



Waste Heat Recovery

A different example is Norwegian company Present Water, which has come up with a totally unique solution for reducing greenhouse gas (GHG) emissions and recovering waste heat onboard ships. Traditionally, ships recover only about 5-8% of their waste heat generated by the propulsion system. Present Water claims that the full potential of 35-45% of waste heat may be recovered in near future.

Present Water’s partner company Seas is currently testing out a version of the Organic Rankin Cycle (ORC) that could convert heat to electricity at a temperature around 100˚ Celsius with more than 20% efficiency. Known as the Marine Exergy System, the process comprises both its partner companies patented ORC and Methanisation process (RCO2), as well as “off-the-shelf” exhaust gas scrubber and reverse osmosis technology. The company plans to commercialise the product by the end of next year, with the cruise industry as its initial target market.

The entire system enables 90% reduction of all GHG emissions with a fuel saving potential around 40%. The other major upside is that the process also treats the ballast water into freshwater so that it can be brought ashore for irrigation or industrial use, rather than treated and transported needlessly onboard tankers. More than 5-7 billion tonnes of ballast water are transported worldwide a year and represents a major threat to any marine environment, according to Geir Erik Samnøy, Present Water Managing Director.

“A holistic approach is needed to solve the major environmental challenges for the shipping industry,” said Samnøy. “As our company and partners have found a practical and process optimal solution for existing large cruise vessels, we strongly believe that the Marine Exergy system is well suited for most ship segments and power plants ashore.”




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