Class stepping up with solutions for increasing fuel efficiency

DNV GL has developed a novel approach which overcomes the challenges of assessing on board energy efficiency DNV GL has developed a novel approach which overcomes the challenges of assessing on-board energy efficiency

Wendy Laursen explains how, with CO2 emissions measurement on the IMO agenda, class is developing new solutions for fuel efficiency.

A decision was reached at MEPC 66 to start analysing appropriate data collection methods for measures to enhance the energy efficiency of ships. A correspondence group will now determine what data should be collected.

Simon Bennett, director of external affairs at ICS, sees the move positively. “We are pleased because they broadly followed the advice which the industry had suggested which was to focus on the principals of establishing a global data collection system rather than getting dragged down into the detail – things that might come later such as energy efficiency indexing for individual ships. This is much more controversial and the industry itself is opposed to it, so by focusing on the data collection elements, it meant that they were able to make some progress.” He hopes it will satisfy European countries enough that they won’t develop a different scheme.

“People are saying ‘it’s only data collection’ but I don’t think those people appreciate the challenge that is going to be involved for the governments to actually set up a system whereby ships can transmit the information to flag states, and in turn that be centrally collected and analysed.”

Mr Bennett makes the point that shipping has been proactive in developing CO2 reduction measures through MARPOL Annex VI. It won’t be long before the impact of the energy efficiency design index (EEDI) will have had a positive effect on a large part of the global fleet, he says. The role of the ship energy efficiency management plan (SEEMP) is also often unstated. “That will have an impact particularly amongst many of the smaller shipping companies that aren’t amongst the big names and are outside of the geographical places you expect people to make progress. Basically, a lot of it is about managing fuel consumption. What shipowner wants to throw away money?”

Classification societies have been actively seeking ways to help. DNV GL has developed a novel approach which overcomes the challenges of assessing on board energy efficiency in a consistent manner. As a result, priorities for improvement can be determined accurately.

“Ship operations and environmental legislation have become more complex, and it has become increasingly difficult to assess or even define efficiency with consistency and accuracy,” said Rune Torhaug, director of  strategic research and innovation at DNV GL. “We have therefore revisited the basic and universal laws of thermodynamics to develop a methodology based on exergy, sometimes called available energy, which is a metric for describing the maximum useful energy that can be derived from a process, component or system.”

The methodology can be adjusted to suit newbuilds still in the design phase or operational ships, and it is designed to help managers make the most out of their SEEMPs. Using both on board measurements and the DNV GL modelling suite COSSMOS, energy losses throughout the ship including hull, propulsion power train, machinery and electrical systems are quantified and ranked. Even difficult-to-capture processes such as throttling and fluid mixing can be incorporated. With this ‘common currency’ for efficiency, DNV GL provides a way of energy management that will work for all ships and all system and components that convert energy on board.

The DNV GL report introducing the methodology includes an analysis of a waste heat recovery system. These complex systems can easily contain 70 components. “Through our exergy-based methodology, the true sources of useful energy losses were identified, revealing a picture far from self-evident. Subsequent optimisation in DNV COSSMOS yielded an increase in fuel savings that halved the payback time of the system,” said George Dimopoulos, senior researcher and project manager.

When the main engine of an Aframax tanker was analysed using operating data in combination with COSSMOS modelling, the true sources of losses were identified with greater accuracy than a traditional energy analysis, says Mr Dimopoulos. “In fact, the standard energy analysis failed to identify the turbocharger as being the second largest contributor to exergy loss.”

NAPA and ClassNK have demonstrated that the software system ClassNK-NAPA Green has generated fuel savings of 3.9% on a “K”-Line container vessel. The software was tested in full scale sea trials in January 2014 aboard an 8,000+ TEU container ship operating on a standard Mediterranean/Europe route. The full ClassNK-NAPA Green suite of systems were utilised on the voyage, including speed, trim, and voyage optimisation based on the ClassNK-NAPA Green dynamic performance model, and analysed against the captain’s voyage plan. Despite encountering heavy weather on multiple occasions over the course of the voyage, speed profile and voyage optimisation reduced the fuel consumption by 2.7%, while a further 1.2% savings was attributed to optimum trim, taking the total reduction in fuel consumption from the trial to 3.8%.

In addition it was found that the accuracy of the dynamic performance model – the self-learning component of ClassNK-NAPA Green – was extremely high. In terms of fuel consumption prediction the accuracy was as high as 99.6%, which ClassNK says is unprecedented in the industry.

“The results of ClassNK-NAPA Green’s full-scale voyage optimisation trials mark a landmark in the development of operational efficiency software,” said executive vice president of NAPA, Esa Henttinen. “If “K”-Line can save 4% in fuel costs for one vessel alone then the potential savings across its entire fleet is significant. Although software solutions to optimise fuel consumption are nothing new, the differentiating factor for ClassNK-NAPA Green is the software’s dynamic performance model. It tunes the ship specific performance model on a continuous basis to give very accurate, transparent and true performance statistics to improve voyage optimisation, trim optimisation and performance reporting with payback on investment realised within months. Full-scale proven bunker cost saving are significant and feedback to ship designs will improve newbuilds further.”

Classification society RINA has launched InfoSHIP EM, a real time tool for monitoring and optimising the hotel power demand on cruise ships. It is expected to produce hotel load energy savings in the order of over 10%, thus generating significant annual cash savings in fuel costs for a typical large modern cruise ship.

Paolo Moretti, head of the marine business line, RINA Services, said: “Around half the energy used by a modern cruise ship is for the hotel services. So if we can bear down on that we can produce substantial cost savings for cruise operators. InfoSHIP Energy Management is a tool which continuously monitors all the energy users in the hotel services and compares actual use with target values. A simple traffic-light graphic display alerts the ship’s staff to higher than target energy use, allowing them to take remedial measures such as load shedding or load shifting.”

InfoSHIP EM is part of the InfoSHIP Energy Governance suite developed by RINA and software house IB Software & Consulting. It collects live power consumption data from the hotel services, air conditioning systems, accommodation and lighting systems and galley and laundry services. Target values are set by calculation at the design or installation stage and then continuously updated by operational feedback and trend analysis. Target values are optimised according to the season and area of operation, the operational mode, either in port or at sea and the time of day.

“This system will pay for itself in under a year and is simple to install,” said Mr Moretti. “What it does is focus the engineers and technical department on the actual electrical power demand of hotel services. It allows them to make adjustments to operations or pre-set temperatures for the air con, for example. InfoSHIP EM gives the cruise ship operators the information they need to make sensible energy saving decisions, such as getting laundry done outside peak time, or changing air-conditioning patterns. It also provides real data to inform decisions on retrofit or updates to onboard equipment.”


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