The vessel being built in Poland for the Estonian State Fleet will be the country’s first fully electric passenger ferry and will employ next‑generation contra‑rotating propeller (CRP) units from Finnish propulsion specialist Steerprop.
New CRP design aims to boost efficiency and ice performance
Two Steerprop SP 25 CRP propulsion units with permanent‑magnet motor drives will be installed on the 95‑metre ferry, which is designed by LMG Marin. The company says its updated CRP arrangement maintains high thrust levels while improving mechanical efficiency compared with conventional single‑propeller setups. That combination has been highlighted as particularly valuable for vessels that must operate in ice, open water and windy conditions despite limits on propeller diameter.
The CRP configuration uses tandem propellers on a single shaftline — a push and a pull propeller — which Steerprop argues delivers greater thrust and can attain equivalent thrust with lower power input, contributing to reduced energy consumption and emissions.
“The latest development delivers unique efficiency and thrust performance,” said Markku Miinala, Steerprop’s Cruise & Ferry Segment Director, adding that the design gives an even greater advantage for ships operating in ice conditions.
Mechanical innovation and lubrication change
A notable technical change in the new generation of CRP units is the standard use of pressure lubrication on the smaller units. By dispensing with immersion lubrication, Steerprop reports a reduction in mechanical losses and an efficiency improvement of roughly 3.5 percent, which it says enhances operating economy.
The SP 25 units can be integrated with a range of power systems, including diesel, hybrid or fully electric arrangements, giving ship designers flexibility when pairing propulsion hardware with different energy architectures.
Vessel power and ice class
The ferry will be equipped to run primarily on shore‑supplied renewable electricity stored in a 3MWh battery system. Auxiliary biodiesel generators are included to offer extra power during extreme weather or emergencies. The hull will meet Ice Class 1B standards, enabling operations in light ice conditions.
- Propulsion: 2 × Steerprop SP 25 CRP units with permanent‑magnet motors
- Length: 95 metres
- Battery capacity: 3 MWh
- Ice rating: Ice Class 1B
- Efficiency gain: ~3.5% through pressure lubrication
Context and implications
Steerprop already has an established footprint in Estonia; four double‑ended ferries operating on the Saaremaa and Hiiumaa routes use CRP propulsion. The adoption of the newer CRP generation on a fully electric ferry reflects broader industry momentum toward electrification and more efficient propulsion systems, particularly for short‑sea and passenger ferry operations where shore charging is feasible.
For shipowners and operators in northern waters, the combination of higher propulsive efficiency and improved performance in ice can lower fuel or energy consumption and reduce emissions from auxiliary engines. Pressure lubrication’s reported efficiency improvement, while modest in percentage terms, can contribute to lifecycle operating savings when aggregated over years of service on a busy ferry route.
The ferry under construction at the Polish shipyard CRIST SA represents a step in marrying battery storage and electric drive trains with propulsion hardware optimised for harsh marine environments. Its design choices — including a sizeable battery, backup biodiesel gensets and an ice‑capable hull — underline the pragmatic approach many operators are taking to balancing emissions reductions with operational resilience.
As more shipbuilders and propulsion manufacturers experiment with contra‑rotating systems and electrified powertrains, regulators and classification societies will continue to evaluate how such technologies perform in service. The Estonian project provides an example of how component‑level innovation (propulsors and lubrication systems) can be paired with system‑level changes (battery power and shore charging) to advance decarbonisation in the maritime sector.
