Electric ship initiatives offer flexibility, increased warfighting power
By RICHARD R. BURGESS, Managing Editor
In many warships, a mechanical
drive system is used for propulsion.
The engines are mechanically connected to reduction gears, which
are connected to the propeller
shafts. The engines also mechanically power generators or motors
that drive generators to provide
electrical power throughout the
ship. Auxiliary generators are commonly used to produce power.
With conventional mechanical
drive, a ship is restricted in design
to a layout in which the engines
and reduction gears are typically located in the lower
aft hull. One advantage of electric drive is that the
engines and generators can be located almost anywhere in the ship, connected to the drive motor by the
transmission wiring. The flexibility allows a designer
more freedom in designing survivability into a ship.
The fact that the propeller shaft is rotated by a quiet
electric motor rather than a mechanical reduction gear
also reduces the acoustic signature of a ship.
A hybrid electric drive is a combination of the two
concepts in the same propulsion system, whereby the
operator has the option of using electric or mechanical
drive, depending on the speed and fuel efficiency
desired. The concept is used in modern automobiles,
such as the Toyota Prius.
San Diego-based General Atomics and DRS
Technologies, Parsippany, N.J., are teamed “to explore
technologies to improve fuel efficiency,” Petersen said.
“The goal of the hybrid electric drive project is to
reduce fuel consumption, leading to reduced dependency on fossil fuel.
“Further, the hybrid electric drive system could
increase mission effectiveness through longer time on
station,” he said. “Their project entails developing
hardware to be tested at the Philadelphia DDG 51
Land-Based Engineering Site.
The Navy’s electrical ship programs are benefiting from innovative industry participation.
■ The concept promises greater ship fuel efficiency and flexible
energy for future weapons.
■ Superconducting and permanent magnet motors compete for
■ Power transmission and switching technology present challenges.
With the help of industry, the Navy is maturing the solutions proposed for the challenges of electric ship technology, a transition that promises flexible design options, greater fuel
efficiency and sufficient power for the mission systems
of the future.
With innovative concepts such as hybrid drive,
more powerful electric motors and generators, and
greater electrical storage capacity and distribution, the
Navy is designing and building ships to capitalize on
“Across the Navy, from basic science to in-service
applications, initiatives are being established based on
technology gaps and needs,” said Capt. Lynn Petersen,
deputy program manager of Electric Ships for the
Navy’s Program Executive Officer for Ships. “New ship
designs are taking into account the benefits of all electric and hybrid drive technologies.”
Electric drive is a propulsion arrangement in which
a ship’s engines — typically gas turbines, steam turbines or diesel engines — power an electrical generator. The generator, in turn, powers a large electric
motor, which is connected to the propeller shaft.
Generators also provide power to the ship’s combat
systems, lighting, heating, air conditioning, elevators
and other missions and “hotel” requirements.
SEAPOWER / MAY 2009