Getting ready for net zero by maximizing energy efficiency
Energy efficiency is key to remaining competitive
Vessels must be made as efficient as possible as soon as possible to remain competitive when tightening emission restrictions cause fuel costs to rise significantly. DNV has identified and categorized a wide range of measures that can be taken to enhance operating efficiency. Some of them can be implemented at virtually no cost; others require minor or major investments. The best measures to take largely depend on the age of the vessel, i.e. the expected remaining operating time. DNV recommends evaluating all the following options carefully and implementing those that have the best cost vs benefits ratio, i.e. represent the strongest business case. DNV offers comprehensive advice and resources for the decision-making process.
Operational measures
Operational measures relate to the way a ship or entire fleet is run. They mostly include behavioural changes and optimization measures to realize the full efficiency potential of existing equipment and systems. They are typically low-cost and quite effective in helping to keep the fuel costs as well as carbon emissions down. At the same time, however, they require focused management, digital performance management tools, and getting people throughout the organization involved and committed. Especially for vessels in operation with a limited remaining lifespan, these measures can achieve significant savings without incurring major investment costs. Many shipowners implement some of these measures to some extent but find it difficult to realize the full potential or are unaware that more can be done. DNV stands ready to help them identify additional potential for energy efficiency enhancements.
Operational measures: Optimizing machinery and system operation
• Optimization of auxiliary systems (such as electrical, water, low-pressure air, hydraulic, bilge, steam, ballast water, automation and control systems etc.) to ensure operation at optimum loads • Optimization of auxiliary engine loads to reduce number of engines running • Steam plant optimization to minimize fuel consumption by auxiliary burner • Main engine testing and tuning • Optimization of turbocharging at lower engine loads (exhaust gas bypass, EGB)
Operational measures: Optimizing hydrodynamic and propulsion efficiency
• Regular underwater hull cleaning during normal stops to minimize drag • Frequent propeller polishing to protect the surface and maximize efficiency • Trim and draught optimization for actual operating speed/draught combination • Autopilot optimization to avoid large-angle rudder movements • Better use of the combinator curve to optimize controllable propeller pitch settings and speed • DP optimization where applicable
Operational measures: Optimizing efficiency during voyages and in port
• Voyage planning, optimization and execution, avoiding waiting time, power variation and excessive speed • Improved fleet utilization to maximize transport work and reduce waiting/lay time • Selection of the best vessel size for the transport job • Improved capacity utilization by optimizing operation planning and execution, fleet composition • Speed reduction to operate at optimum energy efficiency • Minimizing time in port by optimizing port operations and coordination • Weather routing to minimize fuel consumption
Technical measures
While operational measures can achieve significant savings, combining these proven practices with investments in advanced technologies can enhance the operating efficiency of younger vessels and newbuilds much further, giving them the competitive edge they need to operate profitably far into the 2030s and 2040s. This section describes a number of key technical measures, not all of which are necessarily capital-intensive. This list is not exhaustive, and obtaining expert advice for specific ships can reveal additional opportunities for efficiency enhancements. The aim is to find the best possible combination of measures and devices that will maximize the benefits of the investment.
Technical measures: Machinery and systems
• Electronic autotuning enabling automated engine performance optimization • Waste heat recovery to generate electricity using fuel energy that is otherwise wasted • Auxiliary engine exhaust gas boilers for steam generation or water heating • Variable frequency drives (VFD) for pumps, fans and motors to control energy use dynamically • Shaft generator (PTO/PTI) for hotel/sea load to minimize genset operating times • Engine de-rating (turbo cut-out; cylinder cut-out; alternative mapping) • Variable engine speed/frequency control to enhance energy efficiency and flexibility of diesel-electric systems • Optimized cargo-handling systems to accelerate cargo operations and minimize energy consumption
Technical measures: Propulsion efficiency enhancements
• Propulsion improving devices (PIDs) / energy saving devices (ESDs) - before the propeller: ducts, fins, hull modifications to reduce slipstream losses - after the propeller: rudder bulb, rudder fins - high-efficiency rudder to reduce drag, increase thrust, regain slipstream losses • High-efficiency propeller design, ensuring it corresponds to actual speed/draught combination; propeller retrofit if appropriate
Technical measures: Hydrodynamic efficiency enhancements
• Air lubrication system to minimize viscous resistance • Low-friction and antifouling hull coating to reduce frictional resistance from marine growth • Optimized hull form and line design to minimize resistance, based on operating profile • Hull modification / bulbous bow retrofit to reduce drag • Deadweight increase within permissible limits to optimize transport efficiency
Technical measures: Alternative energy sources and general
• Biofuel-readiness to support use of drop-in biofuel to remain compliant • Shore power to minimize emissions in port and reduce overall carbon footprint • Battery hybridization for eco-friendly operation (if applicable): - Plug-in (using shore power) system for ships with frequent port calls - Non-plug-in (charging during voyage) system for peak shaving, load optimization and/or operation in sensitive marine ecosystems • Fuel cells and/or solar panels to reduce energy generation by combustion • Wind-assisted propulsion systems (WAPS), such as rotor sails or hard sails to reduce fuel costs and emissions • Efficient lighting system using LED luminaires and switching lights on as needed only
Technical measures: For improving operations
Advanced, smart on-board and remote monitoring and control systems can help reduce fuel consumption significantly by uncovering and utilizing hidden potential for further efficiency improvements. These broadly include: • Decision support systems • Performance management solutions • Remote monitoring systems
DNV resources provide proven data on efficiency enhancements
To screen for the most beneficial measures for a given vessel or fleet, DNV uses its Abatement Insight database of numerical data and customer feedback from numerous customer projects, especially more than one thousand decarbonization plans. The database contains key data for around 50 relevant technologies and measures shipowners can take to achieve Carbon Intensity Indicator compliance. As a neutral party, DNV makes every effort to provide realistic, experience-based information regarding costs (CAPEX, OPEX, expected benefits).
Making energy efficiency a topic of charter negotiations
For shipowners, decisions about efficiency-enhancing measures that reduce fuel costs and emissions are not only influenced by the age and operating pattern of the vessel in question but also by charter arrangements. While cargo owners seek to negotiate the lowest-cost charter contracts, shipowners naturally want to ensure a viable profit. In their negotiations with charterers, shipowners are encouraged to stress the importance of ensuring the long-term operability of ships. In 2023 DNV introduced the Vessel Technical Index (VTI), which reflects a ship’s technical performance relative to its initial state, thereby eliminating the influence of external operational factors. When used to measure, evaluate and verify the technical performance of operating ships, it allows the industry to determine the efficiency gains from all enhancement measures taken. The VTI is also meant to be used as a facilitator for the adaptation of charter contracts and negotiations so that energy efficiency measures pay off better for shipowners and charterers can rest assured that efficient vessels are being operated.
Conclusion
In summary, for the fleet in service, tweaking operational parameters and increasing crew awareness, combined with low-cost technical measures, is the recommended course of action. As for newbuilds, DNV’s advice is to do everything that can be done to make them as fuel-efficient as possible, and ready them for green fuels, so they will be able to operate profitably and competitively far beyond 2030. This includes both operational and technical measures. Major investments will pay back once the industry must switch to more costly low- or zero-carbon fuels. DNV can prepare short- and medium-term decarbonization plans based on the real-life experience data collected in its Abatement Insight database, applying the new Vessel Technical Index.