According to shipyard Brødrene Aa high-efficiency, controllable pitch propellers are the best option for battery-powered vessels that operate around 20 knots.
Brødrene Aa recently launched Rødne's katamaran Rygerelektra from their shipyard located in a picturesque fjord on the western coast of Norway. Optimized design and the combination of light-weight materials and highly efficient controllable pitch propellers enable fully-electric transport on relatively long distances.
- The Rygerelektra is equipped with energy-efficient Servogear propellers and gearboxes. It has got two HD220 gearboxes, a 110 mm shaft, 820 mm propeller boss and 1475 mm propellers, Servogear service engineer Jørn Helge Glittenberg explains.
The Servogear expert recently made the vessel ready for sea launch by connecting the gearboxes with the shafts, mounting the propeller blades and filling the housing with grease. The next step is start-up and sea trials.
Owned by Rødne Fjord Cruise Rygerelektra will carry tourists from the coastal city of Stavanger and into Lysefjorden, with zero emissions, low noise and little vibrations. Among many attractions the guests will be able to see during the journey is the famous Pulpit Rock. Rygerelektra will also serve as a charter vessel.
- The experience for the tourists will be amazing. You will more or less only hear the sound of the boat sliding through the water. You can not come much closer to nature than this, Anders Rødne says, founder and owner of Rødne.
The Rygerelektra is 42 meters and can carry 297 passengers. It has the world’s largest battery system on this type of vessel, 2100 Kwh. The total cost of the project is 120 MNOK (11 MEUR) and supported by the governmental organization Enova with approximately 20 MNOK.
The katamaran is Rødne’s vessel number 20 from the Norwegian shipyard, and their number 14 in carbon fibre composite. Anders Rødne was present when Rødne picked up their first vessel from Brødrene Aa more than 50 years ago.
- I remember it as it was yesterday. It was a very nice Oregon Pine boat called Rygerøy. It was 53 feet, operating in 16-18 knots. We used it to transport kids to and from school between the island Finnøy and the nearby islands. I recall that the propellers were pretty noisy back then, he says.
Sustainable shipping
Today the propellers are designed to deliver as little noise and vibrations as possible, be energy-efficient, but still deliver necessary power when needed. In February 2020 the vessel was ready to leave the dry and warm surroundings in the production hall. Brødrene Aa use a rail based launch system and mother nature to deploy the vessel safely into the sea.
- Right now we are waiting for the high tide to occur. The propellers are exposed during this operation and we want to have as large margin as possible, Tor Øyvin Aa, the CEO of Brødrene Aa says.
Whereas you have to be careful with the large propellers before they are deployed into the sea, they are also key to utilize necessary energy from the batteries.
- Controllable pitch propellers are the right choice for a battery powered vessel that will operate in speeds around 20 knots. The large propeller blades ensure efficiency, and the pitch can be optimized to the load of the vessel, Tor Øyvin Aa explains.
Only two years ago Brødrene Aa delivered the Rygerdronningen to Rødne, a very efficient fast-ferry operating on traditional fuel.
- I am impressed with Rødne’s ambitious strategy for sustainable shipping. Investing in green vessels also help them cut operational and maintenance costs, Aa says.
Slow-charge at night, fast-charge at daytime
The upcoming summer the Rygerelektra will enter operation with an energy system from Westcon Power and Automation. The electric motors come from Ramme and the batteries from Zem. The captain and engine officer are eager to get the motors started.
- Only a couple of years ago I could never have imagined that we could make this journey only on batteries. We look forward to try the new technology out. We are confident that the energy system is reliable and will perform as expected, captain Joar Dalaker says.
- We will charge during the night and make two round-trips to Lysefjorden every day. We wil fast-charge between the two trips. This will give us enough energy to complete the journey with proper safety margins, machine engineer Svein Dyrdal adds.