A contra-rotating propeller pairs a coaxial aft propeller turning opposite to the forward one, recovering rotational energy for vendor and model-test gains of roughly 7.6 to more than 10 percent. Hurtigruten's Sea Zero zero-emission ship and SINTEF's 2025 testing of Brunvoll's CRP have revived a concept long held back by shaft-in-shaft complexity.
What it is and how it works
A contra-rotating propeller (CRP) arrangement places a second propeller on a coaxial shaft directly behind the first, turning in the opposite direction. The aft blades recover part of the rotational energy that the forward propeller leaves in its slipstream and benefit from improved inflow, according to SINTEF. The price is a shaft-in-shaft mechanical system, and the Energy Institute notes that cost and design complexity have historically kept CRP rare. A hybrid alternative avoids concentric shafts: ABB's CRP Azipod puts a steerable pod behind a conventional shaft propeller, with the shaft propeller carrying 60 to 70 percent of the load and the pod the remainder, per the ABB brochure.
Why it matters now
A propulsive gain of around 10 percent is one of the largest hull-independent efficiency levers available and dwarfs CPP blade optimisation, which Brunvoll puts at under 1 percent. That justifies mechanical complexity on battery or hydrogen ships where every kilowatt-hour counts. It is the logic of Hurtigruten's Sea Zero zero-emission coastal ship targeted for about 2030, for which Brunvoll is the main propulsion and autonomy partner; one proposal uses Brunvoll's CRP for its particularly high propulsion efficiency, and a tested configuration combined CRP with two pulling thrusters, according to Brunvoll and TechXplore.
Key players and products
Brunvoll, then Scana Volda, delivered its first CRP system in 2014 to Ugland Offshore's platform supply vessel Juanita, reports Maritime Informed. ABB's CRP Azipod has powered Shin Nihonkai Ferry's Akashia and Hamanasu, built at MHI Nagasaki, since about 2004 with 17.6 MW pods, per ABB Review, and was also selected for the superyacht Tuhura. A competing ferry arrangement has Wärtsilä supplying the forward CPP ahead of a pod, and CRP was earlier proposed as promising for LNG carriers. Sharrow Marine has developed a contra-rotating version of its toroidal propeller, according to New Atlas.
Figures that matter
SINTEF says more than a 10 percent increase over conventional propellers is possible and Brunvoll quotes gains above 10 percent. ABB's brochure claims "some 10%" for CRP Azipod, and one source reports 20 percent fuel savings for the Japanese ferries against earlier twin-screw ships on the same route. An academic CFD study of a ferry found 7.59 percent, in simulation only, per JARFMTS. All 2025 figures are model-test or vendor statements; no independent full-scale trial confirming Brunvoll's gain was found.
| Metric | Value | Source type | Source |
|---|---|---|---|
| Claimed CRP gain vs conventional propeller | more than 10% | vendor | Brunvoll |
| Possible gain after model testing | more than 10% | verified | SINTEF (model test) |
| Claimed CRP Azipod hydrodynamic gain | some 10% | vendor | ABB brochure |
| Fuel saving, Akashia and Hamanasu vs earlier ferries | 20% | trade-press | ABB Review via Wikipedia |
| Ferry CFD study | 7.59% | verified | JARFMTS (simulation) |
| Shaft propeller load share, CRP Azipod | 60-70% | vendor | ABB brochure |
| Pod rating, Akashia and Hamanasu | 17.6 MW | vendor | ABB Review |
| First Brunvoll CRP delivery | 2014 | trade-press | Maritime Informed |
Developments 2023-2026
- November 2025: SINTEF reported that a purpose-built measurement system had tested Brunvoll's CRP for Sea Zero, delivering data on performance and efficiency; Brunvoll's Jahn Terje Johannessen called the technology mature and ready for wider use, and Hurtigruten's COO said the design is more efficient than existing CRP arrangements.
- 2025: Hurtigruten published an updated Sea Zero design after model testing in Norway, reports CruiseMapper.
- Sharrow Marine unveiled a contra-rotating version of its toroidal propeller for smaller craft.
- A US patent, number 12097940, covering high-efficiency rotating equipment with a contra-rotating propeller was granted in the 2024-2025 period.
- No commercial CRP Azipod or Kongsberg CRP order dated 2023-2026 was found, and no count of CRP systems in service worldwide exists in the material reviewed.
Outlook
Hybrid CRP remains the only configuration with a multi-decade high-power service record, at 17.6 MW on the Japanese ferries, while mechanical CRP has stayed in the 1 to 10 MW offshore and coastal range. The final Sea Zero propulsion selection and shipyard contract were not found, so the first large mechanical CRP on a zero-emission passenger ship is still a plan rather than an order.
