Pre-Swirl Stator: Save Fuel and Reduce CO2
A Pre-Swirl Stator (PSS) is an Energy Saving Device (ESD) installed just ahead of the ship’s propeller to optimize the water flow to the propeller. This innovative system increases the propeller’s efficiency, resulting in fuel savings of 4 to 8%, depending on the ship type, operating profile, and sailing speed. By reducing energy losses in the wake flow, the PSS contributes to lower CO2 emissions and significantly reduced operational costs. Moreover, it offers a sustainable and cost-effective solution with a payback period of just two years or less, making it a highly profitable and valuable investment for many shipowners and operators in the maritime sector.
In 2023, Sam Shipping, a ship management company headquartered in Papendrecht, the Netherlands, decided to implement this technology on their coastal vessels, Marit and Myrte. This article explores the considerations behind this decision, the implementation of the PSS, and the improvements achieved through this innovative technology.
EEXI and CII Calculations for Energy Performance
Before Sam Shipping installed the Pre-Swirl Stator on both vessels, the company first conducted an EEXI (Energy Efficiency Existing Ship Index) calculation and a CII (Carbon Intensity Indicator) assessment. These analyses, carried out by our partner specializing in ship performance optimization, provided clear insights into the current energy performance of the sister ships Marit and Myrte. The EEXI calculation evaluated the overall energy efficiency of the ships, while the CII assessment focused on the carbon intensity per ton-kilometer.
Express Analysis: Feasibility Study for Ship Optimization
Although the Marit and Myrte complied with EEXI and CII standards, an initial exploration through an Express Analysis revealed opportunities to further reduce fuel consumption and CO2 emissions. Based on these findings, Sam Shipping commissioned our partner to conduct a comprehensive study focusing on improvements below the waterline. This analysis examined various aspects, including the bulbous bow and the potential of Energy Saving Devices (ESDs) such as the Pre-Swirl Stator for both vessels.
Our partner utilized advanced Computational Fluid Dynamics (CFD), a reliable and cost-effective method comparable to traditional towing tank tests. This technique digitally simulated both coastal vessels, considering their actual operating profiles and speeds. These simulations enabled engineers to precisely analyze the water flow around the ships and determine which modifications, such as an improved bow shape or the installation of a Pre-Swirl Stator, could enhance efficiency.
Results of the Express Analysis: Efficiency Improvements with PSS
The Express Analysis showed that installing a Pre-Swirl Stator (PSS) could achieve an efficiency improvement of more than 4% on both ships. Among the alternatives considered, the PSS proved to be the most effective choice for increasing efficiency and reducing fuel consumption, with a payback period of two years. Consequently, Sam Shipping decided to install the PSS, designed and supplied by our partner, on both sister ships, which has now been successfully implemented.
Looking for more inspiration? Visit our featured projects page and discover various practical examples of how ships can not only sail more efficiently and sustainably with Energy Saving Devices (ESDs) such as the Pre-Swirl Stator (PSS), but also with other innovative technologies.