In the past, bulk carriers used diesel mechanical propulsion. With the development of electric propulsion technology, many advantages have been achieved, such as high redundancy, flexible equipment layout, energy conservation, and reduced exhaust emissions. After long-term research, the Japanese shipowner Mukaishima Dock Company has decided to build an electrically propelled bulk carrier, mainly used for steel transportation in the inland waters of Japan. This ship ushered in a new era of electric propulsion for bulk carriers. 
 

The electric propulsion system on Mukaishima Dock bulk carriers is integrated by the 712 Research Institute in Wuhan, China. With its high-level technical capabilities and professional knowledge, 712 Research Institute stands out from fierce competition among many globally renowned companies and local Japanese companies, and has been selected as the supplier of electric propulsion systems for Mukaishma Dock bulk carriers. Considering Vacon's good reputation and advanced ship electric propulsion system application solutions, 712 Research Institute and Japanese shipowners have chosen Vacon as the supplier of main propulsion devices and thruster drives.

environmental benefit

The main propulsion system and thrusters of this bulk carrier (with a total tonnage of 499 tons) are equipped with variable speed electric propulsion, which is energy-saving and environmentally friendly. The high level of automation and flexible maneuverability reduce fuel consumption, improve the comfort of crew life, and make the number of crew required for management much smaller than traditional bulk carriers.

Compact for harsh environments - Danfoss VACON ®  NXC frequency conversion cabinet

This ship is equipped with two main thrusters and one bow thruster. The main propulsion motor has a power of 375 kW and a rated speed of 1800 rpm. The power of the bow thruster motor is 200 kW and the rated speed is 1800 rpm.

The main propulsion drive adopts a 12 pulse air-cooled Danfoss VACON ®  The NXC frequency conversion cabinet and bow propulsion drive use a 6-pulse air-cooled Danfoss VACON ® NXC frequency conversion cabinet. Two sets of 12 pulse main propulsion drivers form a quasi 24 pulse structure to reduce harmonics and meet the classification society's requirement for THDu<5%. Due to VACON ®  NXC frequency conversion cabinet adopts VACON ®  The NXP series has the same technical platform, thus achieving a modular and compact structural design.

Heat dissipation is designed by Danfoss VACON ®  The core issues of NXC frequency conversion cabinet; The frequency conversion cabinet has undergone comprehensive and rigorous testing to ensure long-term service life in harsh environments. The frequency conversion cabinets of the main thruster and bow thruster are located in the lower hull, which places high requirements on the floor area and heat dissipation of the frequency conversion cabinets. VACON ®  The NXC frequency conversion cabinet can operate reliably under these conditions. Through the built-in ship application software, VACON ® The NXC frequency conversion cabinet has fast torque and power limiting functions, as well as power control mode, making it very suitable for the working conditions of electric propulsion.

In addition, due to the main propulsion device and bow thruster frequency conversion cabinet being equipped with braking units and braking resistors, the energy regenerated by the motor can be dissipated in the braking resistor through the braking unit when the ship suddenly slows down or stops in an emergency.

Mukaishima Dock's electric propulsion bulk carrier, with a total tonnage of 499 tons and a deadweight tonnage of 1800 tons, was built at the Qingdao Shipyard located on Jimo Island, Shandong Province, China. The ship began construction in March 2010, was launched in September, and underwent sea trials in November 2010. This environmentally friendly bulk carrier also receives special subsidies from the Japanese government.

Other electric propulsion projects

In its first year of operation, Mukaishima Dock's bulk carrier attracted widespread attention and interest from Japanese media and shipowners. The initial design goals of reducing fuel consumption, reducing exhaust emissions, energy conservation, and environmental protection have been achieved and verified in operation. In terms of fuel consumption, the ship ranks fifth among 100 similar ships in Japan.

The electric propulsion system of this ship works very reliably. Japanese shipowner Mukaishima Dock is very satisfied with this and plans to order other bulk carriers of this type, equipped with an integrated electric propulsion system from 712 Research Institute. The preferred propulsion driver is Danfoss VACON ®  NXC frequency conversion cabinet. In summary, the successful construction of this ship highlights the promising market prospects for bulk carrier electric propulsion.

 

Characteristics of electric propulsion system

The electric propulsion system can allow the same generator set to simultaneously support propulsion and other requirements, enabling more flexible new arrangements and more effective integration of ship energy consumption systems. Therefore, ships can be redesigned to expand the passenger and cargo space below the deck. Almost all newly built large commercial ocean going vessels are electrically propelled, including many large cruise ships such as Queen Mary 2.

Bulk carriers, bulk carriers, or bulk carriers are commercial ships specifically designed to transport unpackaged bulk cargo such as grains, coal, ore, and cement in cargo holds. Since the construction of the first specialized bulk carrier in 1852, its economic benefits have driven the development of these ships, leading to a continuous increase in their size and complexity. Today's bulk carriers are designed to maximize payload, safety, efficiency, and withstand harsh operating conditions. Today, bulk carriers account for 40% of the global merchant fleet, ranging in size from single person small bulk carriers to giant mining vessels capable of carrying 400000 deadweight tons (DWTs).