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High-potential energy-efficiency measures

Energy-efficiency measures are the backbone of shipping’s decarbonization journey. A case study for a typical large cargo vessel demonstrates fuel savings of USD 60,000 per trip from Brazil to Rotterdam today, if energy savings of 20% can be achieved. This slideshow highlights energy-efficiency measures with high savings potential from a new DNV guidance paper.

High-potential energy-efficiency measures

Why is energy efficiency important?

Why is energy efficiency important?

Energy efficiency has multiple benefits, both short term and long term. Short term: Energy efficiency can drive reductions in fuel consumption, leading to a direct reduction in CO2 emissions. This can help shipowners comply with regulations such as EU ETS and FuelEU Maritime, and result in cost reductions, both in fuel savings and in the avoidance of regulatory penalties. Long term: Energy efficiency will help to drive the large-scale emergence of carbon-neutral fuels. These fuels will be more expensive than conventional fuel types, so combining them with energy-efficiency measures will significantly reduce the cost differential, thus improving the business case for shipowners adopting them and encouraging greater uptake.

How energy-efficiency measures can enable the faster adoption of alternative fuels

How energy-efficiency measures can enable the faster adoption of alternative fuels

A typical large cargo vessel (in this example case a bulker) sailing from Brazil to Europe today would burn 600 tonnes of fuel, costing around USD 300,000. Achieving a 20% fuel saving through energy-efficiency measures would result in savings of USD 60,000, which strongly supports the energy-efficiency business case. In a future scenario where fuels like methanol are much more expensive, these savings could increase to around USD 1,200,000, making the energy-efficiency business case even more compelling. This figure excludes additional gains from regulatory costs (ETS, FuelEU, GFI). Such substantial savings also help close the cost gap between conventional and alternative fuels, further strengthening the case for their adoption.

Evaluating efficiency measures for your fleet

Evaluating efficiency measures for your fleet

A new guidance paper on energy efficiency looks at all energy-efficiency measures available today. Each measure and technology is explored and presented in detail. At DNV we recognize that the effect of each energy-efficiency measure varies depending upon a range of factors such as vessel type, size, age, location, and route. Every shipowner should think carefully about what the best solutions are for their fleet and, just as importantly, how this will work best on their balance sheet. Estimated OPEX and CAPEX costs are therefore also outlined for each measure, as well as suitability for different vessel types and characteristics. This slideshow presents an overview of efficiency measures with savings potential between 10 and 20%, which are ranked as large savings. The paper provides a more detailed analysis of each measure.

Hull form optimization

Hull form optimization

Hull form optimization is essential for fuel efficiency, impacting profitability, carbon intensity, and vessel value. A combination of parametric modelling, advanced computational fluid dynamics, and genetic optimization strategies can help to define the forefront of hull line optimization and maximize the overall performance of a vessel. Collaboration among all stakeholders ensures the best results, aligning design with operational goals. DNV’s extensive experience and innovative tools make it a leader in optimizing hull forms for various vessel types.

Shore power

Shore power

Shore power, also known as “cold ironing”, uses electricity from shore to meet onboard energy demands when vessels are docked, such as lighting, heating, cooling, and loading/unloading operations. This can remove the need to run the vessels’ generators while in port, thereby improving energy efficiency. This technology can also charge batteries for hybrid and electric vessels. However, providing shore power can strain the electricity grid, requiring significant developments and increased power production. Despite these challenges, shore power has been widely used since the early 2000s, particularly in RoPax and cruise vessels, offering substantial savings and environmental benefits.

Variable engine speed

Variable engine speed

Variable engine speed can significantly improve fuel efficiency by reducing specific fuel consumption at lower rpm, especially for engines driving generators. This approach is particularly beneficial for vessels with controllable pitch propellers and power take-off (PTO), allowing for optimized rpm and vessel speed. Implementing a rectifier in the electrical system enables variable generator rpm, either through a DC grid or variable frequency drive (VFD). Despite the challenges of retrofitting electrical systems, variable engine speed is a well-established practice in both marine and onshore operations, offering substantial savings and efficiency gains.

Speed optimization

Speed optimization

Speed optimization is a cost-effective method to reduce fuel consumption and carbon footprint by managing vessel speed through slow steaming, speed management during voyages, and just-in-time arrival. While market standards often dictate speed, owners and operators can influence it, balancing commercial impacts with cost benefits. A 10% speed reduction can lower fuel consumption by up to 27%, though total savings on a voyage basis typically range between 10% and 20% if the possible need for a larger fleet to carry out the transport work is considered too.

Bulbous bow retrofit

Bulbous bow retrofit

Bulbous bow retrofits are tailored to each vessel’s design and operating pattern, optimizing performance for slow steaming speeds and light draught conditions. This adjustment can yield efficiency gains of 2–15%, with no operational costs. The retrofit process involves advanced parametric modelling and computing capacities, ensuring robust design solutions. Close cooperation between owners, designers and shipyards is crucial for successful implementation, with DNV having extensive experience in delivering these retrofits to thousands of vessels.

Engine derating

Engine derating

Engine derating involves replacing components to improve performance at reduced load, typically for diesel-mechanic propulsion plants combined with slow steaming. This process can yield efficiency gains of 5–15% and reduce operational costs, though it requires significant investment and compliance documentation. Despite challenges, derating older engines can offer substantial savings and is often reversible, allowing engines to be restored to their original rating.

Waste heat recovery

Waste heat recovery

Waste heat recovery (WHR) converts rejected engine heat into useful energy like electricity or service heat. There are two types: exhaust WHR, which uses high-temperature exhaust gas and steam turbine systems, suitable for large ships and providing 5–12% efficiency gains, and low-temperature WHR, which uses low-grade heat sources and organic Rankine cycle (ORC) technology, ideal for smaller vessels with 2–5% efficiency gains. Integration depends on the vessel’s operating profile and heat source scale, with exhaust WHR requiring significant modifications and being best for newbuilds, while ORC systems are easier to integrate but less efficient. Both types help save fuel and reduce emissions, with system choice based on vessel characteristics and operational needs.

Weather routing

Weather routing

Weather routing improves energy efficiency by optimizing fuel consumption and ensuring timely arrivals. Key factors include waves, wind, and current, which affect resistance and speed. Routing relies on forecast data, with higher uncertainty for longer routes. It’s crucial for slow vessels, high sea states, and areas with strong currents, helping operators to avoid or take advantage of these conditions. Wind-assisted vessels benefit from wind routing for additional savings.

Wind-assisted propulsion systems

Wind-assisted propulsion systems

Suitable vessels that operate on routes with favourable wind conditions can benefit from wind-assisted propulsion systems (WAPS) as the different available technologies harness wind power to reduce fuel consumption and emissions. These systems use advanced aerodynamics, modern materials, and automation to enhance efficiency compared to traditional sails. However, implementing WAPS still presents some challenges, such as the high cost of investment, structural integration, operational safety, and regulatory compliance. Addressing these issues is essential for optimizing the benefits of WAPS in reducing fuel consumption and emissions. When it comes to energy savings, these are highly dependent on weather conditions, and while the peak can be quite high, the annual savings are lower. As such, WAPS may not be suitable for the whole global fleet, but it can be a suitable technology for some vessels and routes.

Dynamic positioning power system upgrades

Dynamic positioning power system upgrades

Dynamic positioning (DP) operations provide high savings potential for shuttle tankers and offshore vessels. DP requires station-keeping to be maintained after the worst-case single failure, typically involving multiple engines online at low load. Fuel consumption can be reduced with fewer engines online and closed-bus operation. Measures to achieve this include upgrading DP control algorithms, updating safety barriers, installing batteries, and using variable-speed generators. Despite high investment costs, vessels with fuel-efficient power configurations can achieve savings of up to 30%, with typical savings in DP mode ranging from 10 to 15%.

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