Direct Current (DC) power networks enable ships to realize significant fuel savings, maximizing the efficiency gains of gensets, renewables and battery storage. Thorsten Strassel, Global Product Manager at ABB, explains why DC power is a priority for marine operators and fleets – and the new technology making adoption simpler.
What is DC distribution?
Direct current (DC) is a one-directional flow of electrical charge – alternating current (AC) periodically changes direction. In everyday life DC is commonly found in photovoltaic panels or in batteries storing energy or supplying electronic devices.
DC distribution has the potential to be a big energy saver. The growing number of renewables, battery storage systems, and power electronics used for motor drives and chargers all need to be connected.
Low-voltage DC system can reduce distribution losses and eliminate the conversion losses associated with AC distribution.
With electrical systems connecting increasing numbers of renewables, battery storage and power electronic based consumers from chargers to motor drives, DC distribution has the potential to become a big energy saver. DC distribution can also save a significant amount of raw materials as well.
Right now, shipping is the early adopter, using low voltage DC distribution as they implement diesel-electric propulsion. Fuel efficiency improvements of up to 20% are possible for a wide range of vessels.
Why is shipping adopting DC distribution?
DC distribution helps fleets improve costs, efficiency and environmental performance. Ships move more than 80 percent of global trade. Although shipping is energy efficient, the International Maritime Organization (IMO) has called for a 40 percent reduction in shipping’s carbon intensity by the end of this decade and 70 percent by 2050.
Electrification and energy efficiency improvements are part of the way forward. DC distribution can make the propulsion and the onboard operations more efficient, integrating batteries and green hydrogen fuel cells and maximizing the efficiency of electric motors in a sustainable way.
How do vessels use DC to achieve energy savings?
DC power systems enable ships to match the electrical output of onboard diesel-electric gensets with the power required for propulsion and other loads – without AC power’s strict constraints on operation points.
The same goes for on-board shaft generators, batteries and fuel cells. DC electrical architectures simplify the integration of battery storage and hydrogen fuel cell systems into the ship’s electrical system and help maximize their efficiency.
And, as vessels electrify more onboard functions, such as deck machinery, winch systems, and high-power pumps, battery storage systems are increasingly important sources of back-up power. DC systems and better protection devices also provide higher fault tolerance and energy savings for these functions.
What could be realistic energy-savings for a ship?
Fuel savings depend on the specific vessel’s onboard technology and mission/load profiles. For vessels with variable speed motors and onboard energy storage, DC enables them to match the generator speed more closely to the ship’s demands and shed peak loads. In these circumstances, 20 percent is a realistic target for fuel savings.
What technology advances are needed for ships integrating DC distribution?
Safety and control are fundamental requirements. Short circuit currents in new DC systems are not only higher – they can also build up 10-20 times faster. Managing this for large systems can require a complex mix of protection devices like circuit breakers, switches, contactors or power electronics like DC/DC converters.
ABB’s new all-in-one circuit breaker, the SACE Infinitus, provides a simpler way to protect and control DC systems. It can detect and respond to short circuit faults 100 times faster than traditional mechanical circuit breakers. This speed enables the SACE Infinitus to halt emerging short circuit currents almost instantly – and provide the high levels of service continuity and safety required in mission-critical marine applications.
ABB Review: Key technology to unlock DC distribution’s potential
This ABB Review article provides an overview of the SACE Infinitus and its benefits for marine and shipping applications. https://new.abb.com/news/detail/96069/one-of-a-kind
