IEEE Electrification Magazine - September 2017 - 76

large energy surplus because the
prime mover is operating while the
vessel is working at a zero or low
speed. This energy surplus is dissipated as heat in a trolling gear or
by reducing the usage of a controllable pitch main propeller. This
variation in power demand and
energy dissipation should be
exploitable to achieve better overall
energy efficiency, and this will require
a machinery arrangement that does
not use the prime mover as the
single energy source.

Diesel-electric
power systems are
popular onboard
vessels, which
have large variations
in loads but
maintain a constant
load for a relatively
long time.

Electric Marine Power
Systems
Electric power distribution onboard larger ships has
been employed in diesel electric solutions where a set of
generators is used to power the ship, with various generator configurations used for different power levels.
Diesel-electric power systems are popular onboard vessels, which have large variations in loads but maintain a
constant load for a relatively long time. Diesel-electric
solutions require a generator to be running at all times
because they contain no power buffers. This prevents
operation in a full electric mode event, although the
power distribution and propulsion systems, in principle, could be used in such a mode. Diesel-electric solutions are popular in the offshore sector for standby
vessels and have been adapted in ocean-going bottom
trawl and longline vessels. The installation of additional
generators is cost prohibitive and impractical onboard
the smaller vessels in the coastal fleet. The operation of
the fleet's popular fishing gears also indicates that there
are low power demands during fishing, which could be
satisfied by batteries in combination with a conventional engine for transit.
The automotive industry has led the development of
battery-powered transportation. Hybrid cars have become
a common sight on the roads, and the popularity of fully
electric cars is increasing with both manufacturers and
customers. The shift toward battery technology in the
automotive sector has been driven by both technological
development and government policies. The full electric
car has demonstrated advantages beyond energy use,
such as reduced emissions, noise reduction, and system
simplicity. The marine sector is a conservative sector;
hybrid energy systems with batteries are a new concept,
and fossil fuel is the preferred energy source. The Norwegian fisheries fleet is diesel powered; the continued reliance on diesel fuel is motivated by demonstrated system
reliability, its energy density, and the practicality of refuelling at longer intervals.
Electrification of a diesel-powered ship requires more
than an electric power source. An electric power

I E E E E l e c t r i f i c ati o n M agaz ine / SEPTEMBER 2017

distribution system, from energy
production to propulsion, is a prerequisite for electrification of
vessels. The use of batteries is,
therefore, the second step in electrification, which can improve dieselelectric solutions by eliminating the
need for continuous diesel generator operation when energy de mands may be met by stored
electric energy. Developments in
battery technology have led to the
availability of solutions that are
now attractive for installation aboard
ships. Examples of battery-based
energy systems include the fully
electric Ampere ferry, battery-based
power buffers for the offshore vessel Viking Energy, and
part of a hybrid propulsion system in the coastal fleet in
the case of the vessel Karoline.
These three examples highlight the versatility of electric power distribution and batteries: once an electric
power distribution system is available, batteries may be
included to provide some or all of the power needed.
This article focuses on the use of an electric power distribution system and batteries to cover the energy demands
onboard smaller vessels such as the Karoline during lowpower operations such as fishing trips.

The Karoline: A Hybrid Coastal Fishing Vessel
The fishing vessel Karoline was built by Selfa Arctic as
an operational prototype for battery technology applications onboard smaller fishing vessels. The vessel contains a 190-kWh battery pack, which may be charged
from either a shore connection or by a diesel generator
onboard the vessel. When the batteries are charged on
the shore, the fossil fuel consumption is reduced and
replaced with inexpensive renewable energy because
hydroelectric power is the dominating electrical energy
source in Norway. The vessel is configured with a Siemens electric power distribution and propulsion system together with a battery pack from Corvus and a
diesel generator from Volvo Penta. The diesel generator
is operated in a serial hybrid configuration, where the
diesel generator only delivers electric power and is not
mechanically connected to the propeller. The Karoline is
rigged as a traditional coastal fishing vessel, apart
from the power system, and operates mainly gillnets
on the coast outside of the island Vannøya in the north
of Norway. The vessel is based approximately 2.5 h at
7.5 kn from the fishing ground. The approximated
operational profile for the vessel is 4-5 h steaming and
3-4 h of fishing activity. Gillnet fishing consists of
deploying a chain of nets from the boat and subsequently hauling them back onboard the vessel at low
speeds with mechanical assistance. The combination

Table of Contents for the Digital Edition of IEEE Electrification Magazine - September 2017