Overview

The expected service level of the winter navigation system has been set in the 1990’s when the current common Baltic assistance icebreaker fleet, between Finland and Sweden, took its form in size, number, and setup of different types of icebreakers. Since then, many changes have happened that impose challenges for and affect the performance of the winter navigation system, e.g., the merchant vessel fleet performance has changed, there are new bow shapes of the merchant vessels, increasing installations of offshore wind parks, climate changes, etc.

The objective of this work package is to study the effects of the current and future challenges of the winter navigation system, and to find the optimal icebreaker fleet composition with minimal overall environmental impact while still maintaining the required service level.

Task 6.1 – Development of an ice field dynamics model

There are many factors that influence the ice field. Climate change has caused mild winters to occur more frequently with windier conditions. The mild and windy winters cause the formation of slush barriers, ridges, and other deformed ice features more prominently than the historically normal, severe winters. Increased traffic also has an impact on the ice field dynamics, as every time the ice is broken, it is given space to move and deform, and during sub-zero temperatures the ice-mass increases, as wetted ice floes grow thicker, and bigger and open water patches freeze.

Also, the increasing number of offshore wind parks being planned in the Bay of Bothnia affects the winter navigation system not just by restricting the areas of navigation for the maritime traffic, but also via the ice field dynamics, creating substantially different conditions for the dynamics of the ice field and ice navigation compared to the current situation.

Therefore, in this task an ice field dynamics model will be created to describe the ice field behaviour due to the above-mentioned climate changes, increased traffic, and the offshore wind parks, and foresee and calculate possible consequences on the ice fields. The model will be used to predict and prepare for the effects of the current and future changes on the ice conditions and the winter navigation system, in order to maintain acceptable safety and service level.

Task 6.2 – Study on merchant fleet ice performance and suitability for icebreaker assistance

The efficiency of the winter navigation system is based on the assistance icebreaker fleet and individual icebreakers’ system level performance, and merchant vessel fleet performance, which is governed by the Finnish Swedish Ice Class Rules (FSICR). The FSICR took their principal form in the 1980’s and have proven to be well dimensioned for structural strength for merchant vessels but contain some performance related issues, which are magnified by the current environmental regulation factors and development of merchant vessels. The way these two factors function in balance, largely sets the safety and performance of the system.

Therefore, under this task, a desktop study on ice performance of the merchant fleet and suitability for icebreaker assistance will be performed to compare the ice performance of the merchant vessel fleet from today with the one from the 1990’s navigating ice-covered waters, and the impact of their performance on the icebreaker assistance. The scope of the study will cover trends in merchant vessel size and engine power, historical and current icebreaker assistance and towing speeds, changes in the need of icebreaker assistance, and the effect of different bow shapes of merchant vessels on suitability of towing by icebreakers as well as mitigating actions onboard icebreakers regarding difficulties in towing.

Task 6.3 Studies on icebreaker fleet composition of the future

Design and building of icebreakers are exceptionally challenging. The investments are substantial due to demands on reliable and robust machinery and hull construction as well as other special features, which make lifespans exceptionally long compared to other vessels. Changes in rules and regulations during these long lifespans are certain to be encountered and modifications to existing vessels are always expensive. Therefore, three studies will be conducted to investigate the icebreaker fleet composition of the future.

Firstly, a desktop study will be conducted to explore the future composition of the icebreaker fleet i.e., what sort of a combination of small and large icebreakers as well as other icebreaking resources it should consist of, to be able to keep existing safety and service level. In addition, it will study the effect of the different icebreaker combinations’ performances on the winter navigation system. The overall cost and environmental impact of the winter navigation system will be estimated and used to seek an optimum balance between the ice navigation performance of the merchant fleet, and the size and capability of the icebreaker fleet.

Secondly, the removable icebreaking bow concept developed and built for Lake Saimaa conditions in WINMOS II will be further studied in a possibly larger scale to fit the Baltic icebreaker fleet. This concept envisions a combination of a pusher vessel and a removable bow to increase the beam and possibly propulsion power of the pusher. The Baltic Coastal ice is more deformed than the ice cover in Lake Saimaa, which leads to greater stresses on the removable bow and the coupling as well as possibly greater power requirement for the pusher vessel. Thus, the study aims to further develop the concept by investigating how the more demanding conditions in the Baltic coastal area should be considered. The study will also include a review of the current fleet of suitable vessels for use as pushers for concept.

The benefits of the studied concept are significant. The pushers are typically tugs or other powerful but relatively small ships. Rather than combining different properties in one single vessel, one pusher vessel can be optimized in design for its own purpose (e.g., acting as a tug) and the ice breaking removable bow then gives it greater ice breaking capacity and allows it to break a wider channel to facilitate assistance of larger merchant vessels. The properties that give good icebreaking capabilities are often in conflict with good open water capabilities, which makes them difficult to combine in one design for a multipurpose vessel.

Also, another benefit is that the removable bow does not require any personnel itself but can be managed by the crew onboard the pusher, thus providing savings in personnel costs. Thus, the flexibility of the removable icebreaking bow concept allows increased icebreaking capacity of the icebreaker fleet with lower cost compared to a dedicated icebreaker.

Thirdly, a feasibility study will be made for measures to be taken to lower the environmental impact of the existing and ageing icebreaker fleet. The scope of the feasibility study will cover special analysis on lowering the icebreaker Polaris’ methane slip associated with LNG (Liquefied Natural Gas) usage. For this purpose, a battery pack retrofit for better engine load cases and other means of dealing with methane slip will be studied. In addition, the study will include analysis on alternative fuels for possible future conversions of existing icebreakers.