U.S. Navy’s DDG 1000, Incorporating an Integrated Power System, Will Make Waves

The future USS Zumwalt (DDG 1000) has begun sea trials in the Atlantic Ocean (Fig. 1). The largest destroyer ever built for the U.S. Navy and the first of three Zumwalt-class destroyers, DDG 1000 will be the first U.S. Navy surface combatant to employ an Integrated Power System (IPS) to generate the total ship electric power requirements, then distribute and convert it for all ship loads from common gas turbine generators. This power flexibility allows for potentially significant energy savings and is well suited to enable future high-energy weapons and sensors. The IPS is a unique design integrating a power system with fight-through power and allowing automatic reconfiguration if there is damage to the power distribution system.

Integrated Power System (IPS)

An integrated power system is an all-electric architecture that provides electric power to the total ship (propulsion and ship service) with an integrated plant. IPS enables a ship’s electrical loads, such as pumps and lighting, to be powered from the same electrical source as the propulsion system (e.g., electric drive). This eliminates the need for separate power generation capabilities for these loads. In commercial applications, this is known as the “power station” concept.

Anticipated benefits of IPS include:

• Fewer prime movers. Usually allows a reduction from a total of seven to five prime movers in the traditional gas-turbine surface combatant.
• Reduced costs of ownership. Results in significant fuel savings (15-19% in a typical gas-turbine combatant). Fewer engines installed results in less maintenance and manning.
• Naval architectural flexibility. Provides flexibility in locating prime movers, allowing space previously used for uptakes to be put to better use.
• Improved survivability and stealth. Quiet propulsion motors can better meet current acoustic requirements. Smaller main machinery spaces allow for improved damage control.
• Improved warfighting. Integrated power makes large amounts of power available throughout the life of the ship. This power can be reallocated to accommodate future combat systems. Advances in power conversion are making it possible to provide uninterrupted power, advanced fault isolation, and fight-through capabilities beyond what is currently available.

In a typical mechanical drive propulsion system, the propulsion prime movers are connected to long shafts running through the ship to large reduction gears that rotate the ship's propellers. With electric drive, the prime movers rotate electric generators that are connected through cabling to motor drives and electric motors that rotate a ship’s propellers. Electricity is the medium for transmitting the energy of the prime mover. It enables “cross-connecting” of any available prime mover/generator combination by breaking the physical link between the power generation and power utilization components.

IPS provides for all of a ship’s electrical needs, including propulsion and ship service loads. Traditional electric drives only provide for propulsion. They do not include power for ship service loads.

The Navy has used electric drive in many ships, including early aircraft carriers, a number of ships during World War II, and many of the current inventory of smaller auxiliary ships. In fact, the Navy is leveraging as much as possible from the cruise-ship industry, where nearly all new ships employ integrated electric systems. What is new and significant is the application of these concepts in a fully electrically integrated (no mechanical takeoffs for power) power system on a surface combatant. These ships have higher speed and lower noise requirements than any of the other ships, as well as large combat systems to support. Commercial cruise ships would be too big and too noisy for a surface combatant, and do not have a power system architecture to let them survive damage and continue to fight.