Drives & Controls Magazine May 2023

36 n MOTORS May 2023 The jacket fits for hybrid Norwegian trawlers Shipping consumes around 370 million tonnes of fuel every year, and a single ship can emit as much carbon dioxide as two million cars. Electrified ships – including pure-electric and hybrid vessels – are therefore starting to enter service and the sector is predicted to be worth $16.2bn globally by 2030. A report by IDTechEx suggests there are already more than 100 manufacturers of electric ships around the world, with applications ranging from leisure to fishing and cargo. One of them is the Danish shipbuilder Vestværftet Aps which has shipyards in Denmark and Poland. It has recently built a pair of 50.5m-long and 12m-wide hybridpowered seine fishing vessels – the Elias Johan and the Bernt Oskar – that will operate from a base in Norway. Developing hybrid or fully electric ships requires significant differences in equipment and infrastructure compared to traditional vessels. Smart Automation, a Norwegian expert in integrated automation and hybrid power systems for ship makers, specialises in this growing niche. “The environmental impact of the shipping industry demands new solutions, and to meet this challenge, Smart Automation works with shipbuilders and owners to make shipping greener,”explains the company’s managing director, John Kåre Torkelsen. Most hybrid ships have two methods of propulsion – the most common pairing being a combination of a diesel engine and batteries. Depending on the design of the vessel, diesel direct-drive is used at high power, and diesel electric or pure electric is used at lower power. A challenge for these systems is the space they need on a vessel. Some recent retrofits of such systems have been fitted inside shipping containers for drop-in installation. In newly designed hybrid ships, reducing the footprint of the propulsion system is key to ensuring good ergonomics. “Space is always an issue on shipping vessels, so it was key that our system choice did not have a negative impact on the room on board,”Kåre Torkelsen explains. “For the Elias Johan and Bernt Oskar fishing vessels, we opted for a motor and generator that used a space-saving jacket cooling system, as opposed to a coil.” A jacket cooling system, sometimes called a flow generator, ensures that there is consistent flow of water across the surface of the propulsion motor to keep it cool. This saves space and reduces the need to dissipate heat. The water jacket cooling system used on the Norwegian fishing boats consists of water flowing in a zigzag circuit throughout the motors’frames. The system has a degree of protection suitable for aggressive, reducedspace, or high-temperature environments – ideal for the unpredictable conditions on board a fishing vessel. Crucially, the thermal exchange of the motor does not depend on the environment, and allows several combinations of torque with motor speed. However, space and cooling were not the only considerations when specifying the electric motors for hybrid vessels. The project required a motor that could also operate as a generator to provide the ships’ main source of electrical power. In operation, the motor is used only as an emergency take-me-home drive system, while the generator is responsible for powering everything from lighting, HVAC and refrigeration, through to the vessels’ navigation systems. Both vessels use significant battery energy storage systems. These store energy from the motor when the vessel is operating electrically, and will also be charged up when the vessel is operating in generator mode. The motors specified for the Elias Johan and Bernt Oskar were two 1.5MW models from WEG’s WGM20 range. Importantly, the motors were supplied with IP55 and IP56 protection, ensuring that they are protected against high-pressure water from any direction, dust ingress and immersion of between 15cm and 1m. Motors from this range can be supplied with marine industry certifications, such as Lloyds, Bureau Veritas, ABS and DNV, to ensure reliability. n A massive market is opening up for motors to power pure-electric and hybrid-powered ships. Two recent Norwegian hybrid trawlers are using 1.5MW motors with water jackets to save space and reduce the need to dissipate heat. The Bernt Oskar, one of two Norwegian fishing vessels with hybrid-electric propulsion systems