The ZeroCat 120 is an important first step in the development of non-polluting commercial vessels. It is optimized for an efficient sailing on one specific short haul route in Norway by use of lightweight materials and a catamaran design. Within limits, it may provide a scalable template, representing a very interesting concept to be developed.
Fjellstrand is a shipyard founded in 1928 at Omastrand, in the Hardangerfjord, on the west coast of Norway. Fjellstrand is a modern shipyard, which develops different products, like wind farm service and support vessels, offshore vessel and RORO ferries. The yard has approximately 100 employees, and a variable number of subcontractors. The yard facilities are around 7000 m2 of heated production halls, with a covered storage area of approximately 1100 m2. Fjellstrand is focused on being a leader in maritime renewable technologies and have received international recognition for their work, being nominated for “Offshore Renewables Award 2014” and winning the “Ship of the Year 2014” with the electric ferry “ZeroCat”. The “Ampere” has also won several other prizes from recognized maritime magazines and organizations. Ampere is a RoRo/Passenger ship operating as a fjord crossing car ferry, length 80 meters, width 20.8 meters, with a car capacity of 120 units and passenger capacity of 350. The basic principle is the energy system of this ferry, which is based on energy from the land, based on electric power grid. The power grid is in the Norwegian operation area solely hydropower. To reduce the energy consumption the vessel is built with a lightweight aluminum. The low weight makes it possible to optimize hull shapes and create a high efficiency propeller system. The ferry is of double-ended type and the hulls are symmetrical catamaran hulls with new developed type of thruster propeller. The energy consumption, for a fjord crossing with this ferry, is less than half of a standard steel ferry. In addition, the energy consumed is clean.
The electrically powered ferry was developed for submission to a competition organized by Norway’s Ministry of Transport. As a reward for winning the competition, the shipping company Norled has been granted the license to operate the route until 2025. Norled won the 10 years contract to build and operate the world’s first battery driven ferry on the Lavik-Oppedal route back in 2012. The ZeroCat is thought to crossings at a speed of about 10 knots. The ship’s batteries are recharged during breaks between crossings. It is the world’s first electric car ferry in which the energy is stored on lithium-ion batteries onboard, charged with hydropower from the Norwegian local power grid. Low energy consumption is crucial and all onboard systems are optimized for low energy consumption: heat recovery systems, cooling systems and other technologies, as LED lights and solar panels, work to decrease the general consumption. Special attention is given to the propulsion system, where all components have been evaluated for maximum energy efficiency. The ferry uses an average of one million liters of diesel fuel a year and emits 2680 metric tons of carbon dioxide as well as 37 metric tons of nitrogen oxides. This electric ferry does not discharge to the environment, neither greenhouse gases, CO2, methane or nitrogen oxides. Besides clear environmental benefits, the ferry runs with both lower operational and maintenance costs. The Lavik-Op pedal crossing in Sognefjorden is travelled with almost one million cars per year. The new ferry operate the actual route with 34 crossings a day, 365 days a year. The crossing covers a distance of 5.6 kilometers giving an operation profile of 20 minutes of sailing and 10 minutes at quay.
The amount of electric power required in such a short time is far beyond the capacity of the electrical grid serving in the village s of Lavik and Oppedal. The solution was to install battery buffers at both ports. These batteries can be continuously charged from the grid with 250 kW, then rapidly provide a quick dump to the ferry’s batteries. During night the ferry has a period of seven hours for top charging of the batteries. For one crossing under normal conditions operating at a speed of 10 knots, battery power of only 150-200 kWh is needed, thus providing a wide safety margin. Compared to a standard diesel ferry serving the same route, the electric ferry will save about one million liters of fuel annually, as well as preventing 570 tons of carbon dioxide from entering the atmosphere. The redundant battery pack onboard the vessel is of Li-ion type with good characteristics for rapid charge/discharge rates. It claims 10 m3 of space has a weight of 10 tons and is able to store one million Watt of energy. Under the circumstances specified for Lavik-Oppedal, the battery lifetime is calculated to approximately 10 years. To ensure safe operation, the batteries are of dry type with current and temperature surveillance in each control cell. In addition to the environmental benefits, the ferry’s operational and maintenance costs is lower compared to a conventional ferry. According to Siemens, ZeroCat can eliminate nearly 3000 tons of C02 emissions. Though it is only one ferry, it is an important step for a country where ferries are necessary for moving people and freight across short stretches of water and for that reason Norway has made numerous public commitments to reducing greenhouse gas emissions. Despite its status as a major oil and gas exporter, nearly all of Norway’s domestic electricity comes from hydropower, so battery-electric ferries offer a clear environmental benefit.
The vessel’s hull
The ferry is of catamaran type with both hull and superstructure of seawater resistant aluminum. Aluminum is used in large and high-speed crafts and has very good characteristics for vessels at lower speeds. Both hulls are of slender type with minimal resistance and they don’t need to be ballasted to meet stability requirements. Low weight and slender hulls mean less resistance in constant speed and energy saving in maneuvering operations. The hull shape and material result in energy savings of approximately 9.1% at 10 knots speed. The propulsion system is optimized with variable speed, controllable pitch and feathering possibilities with speed and hull lines as given parameters. During transit, the ferry runs on the aft propeller only, with the other in feathered position. The system results in energy savings of around 7%. The catamaran is propelled by two azipull Rolls-Royce thrusters driven by two 450 kW Siemens motors. The thrusters are mounted at each end of one hull and fitted with efficient slow turning propellers sufficient to drive and manoeuvre the vessel. The other hull only supports load. Both hulls are optimized to reduce drag, so the power requirement is as low as possible. The Rolls-Royce azipull propulsion system, which utilizes pulling propellers as opposed to conventional azimuth thrusters, helps the battery powered aluminum catamaran to reach its high efficiency standards. The ferry starts a working day with fully charged batteries and uses the frequent ten minutes stops at either side of the fjord for partial recharging. Then, during the night, the batteries are fully recharged. This regime is made possible by introducing a bit of smart net technology, boosting the local grid with batteries in each port for quicker recharging.
The future scenario
Passengers and crew comfort will increase due to cleaner environment and minimal noise. ZeroCat certainly stimulate the design and construction of new electric ferries, to cross fjords in Norway and everywhere in the world. For this purpose, Fjellstrand will continue the development of electric ferries and encourage the rest of the shipping industry to follow. To facilitate and speed up the process, national authorities play a great role: to drive new environmental friendly alternatives is essential a removal of the electricity tax for maritime transports, although domestic ferry operations do not represent a large proportion of the total emissions, but it is important to cut where possible. To improve the characteristics of one specific electric ferry is certainly a great step for the ship-owner. Even more important is to spread the knowledge and technology to the rest of the shipping industry, contributing to large reductions of pollution, worldwide.