“When we take on a project like this, we are careful not to overpromise. In this case, however, we underestimated the impact — and were positively surprised by the vessels’ performance, which exceeded even our most optimistic expectations.
I would like to highlight the exceptional work carried out by our hydrodynamicist, Jahn Terje, and the team around him, whose efforts have been key to achieving these results. We are also grateful for the strong collaboration with Utkilen and Becker Marine Systems throughout the project”, says Mads E Melbø, Sales Manager Retrofit at Brunvoll.
The results are clear," says Jarle Hillestad,Head of Ship Management at Utkilen.
"With rising regulatory demands and increasing pressure to reduce emissions, it’s vital that we continue to optimise what we have. When we learned what Brunvoll could offer, this project quickly became a natural next step."
To identify the most efficient measures in terms of both energy and cost, Brunvoll’s team of hydrodynamicists applied their expertise, dedication, and problem-solving mindset to find the optimal solutions, with the project led by Jahn Terje Johannssen, Principal Engineer Hydrodynamics at Brunvoll. Working in close collaboration with Utkilen and Becker Marine Systems, they ensured that each measure was both effective and well aligned with the vessels’ operational profile.
Reducing a vessel’s service speed is, in itself, an effective way to lower energy consumption and emissions. To fully realise the potential savings, however, further optimisation steps may be taken. While this reduction is not directly attributable to Brunvoll, it was an important enabling factor for the other upgrades. The service speed was reduced from 14.5 knots to 12.5 knots.
The reduced service speed — combined with downgrading the vessel’s ice class from 1A Super to 1A — provided greater flexibility in the propeller design process. Brunvoll’s hydrodynamics team was thus able to develop a lighter propeller with significantly higher efficiency.
The gear ratio between the main engine and the propeller has been increased to lower the rotational speed of the propeller to match the new service speed and propeller design.
The Mewis Duct from Becker Marine Systems is an energy-saving device that enhances the inflow to the propeller. Tailored to the vessel’s hull shape, it ensures a more uniform inflow and improved operating conditions, thereby increasing propeller efficiency.
Both vessels were also sandblasted and repainted, further contributing to the overall efficiency gains. These improvements, however, cannot be attributed specifically to either Brunvoll or Becker Marine Systems.
The numbers and calculations presented here are according to Utkilen’s own data gathering and calculations.
The data presented in the following graph are from 68 days before and 68 days after the retrofit project took place. The dotted cyan line indicates the percentage difference in fuel consumption before and after the retrofit project.
Utkilen’s fleet operates primarily in Northern Europe, placing it under both EU and IMO environmental regulations, including FuelEU Maritime, the Energy Efficiency Existing Ship Index (EEXI), and the Carbon Intensity Index (CII).
For the CII, both vessels received a grade C for 2024, but projections indicate a improvement to grade A by 2025, with this high performance expected to be maintained through 2029/2030.
In terms of the EU Emissions Trading System (ETS), where costs are tied to fluctuating carbon pricing, the recent retrofit has already begun to generate measurable savings. Despite only 70 % of 2025 being eligible for reductions (due to the timing of the retrofit), Utkilen expects to save around EUR 200,000 in emission-related taxes that year. With carbon prices forecasted to rise further, the savings are projected to increase to approximately EUR 400,000 in 2026, underscoring both the environmental and economic benefits of the investment.
The payback time for Utkilen’s investment in energy-efficiency measures is estimated at approximately 3.5 years based on fuel cost savings alone. This calculation does not include the additional financial benefits expected from reduced compliance costs under FuelEU Maritime and the EU Emissions Trading System (ETS).
Every vessel has untapped potential. Our engineers are ready to assess your fleet and uncover opportunities to improve both energy efficiency and operational performance. Contact our retrofit team to discuss your options, contact information follows.
Sales Manager Retrofit, Brunvoll Volda AS
