IEEE Electrification Magazine - September 2017 - 79

conditions. The thrusters and hydraulics are mostly
used during fishing, and the low power demand for
propulsion in this phase shows that the gear type used
by the small coastal fishing fleet is well suited for battery power. The operation of a diesel prime mover to
power hydraulics for deck machinery and thrusters will
produce excess power, which will have to be dissipated.
The prime mover will also operate in off-design conditions at low power, which will increase wear and specific fuel consumption.

Energy Usage

Operation Days

Time Usage

Summary

Hours per Day

1,200

1,000

800

600

400

200

0
0

Battery Steaming
Fishing
Steaming

(kWh)

Figure 5. The energy and time use during active days distributed among
operational conditions. In total, the figure shows 433 operational days,
and each pair of bars shows a single operational day.

Energy Consumers in Operational Phases
Steaming
Fishing
Battery
Steaming

35,000

30,000

20,000

15,000

10,000

5,000

25,000

Main Engine
Thrusters
Hydraulics

Standby

Total kWh Consumption
Figure 6. The total energy usage onboard the Karoline distributed
among operational conditions, and the main energy consumers shown
for each operational condition.

batteries consumes little power while it makes up most
of the working day.
The total energy use on each operation is presented
in Figure 6, which shows that steaming uses the most
energy. This operational condition is mainly powered
by the diesel generator, whereas fishing and battery
steaming consume approximately 23% of the total energy
in operational conditions that are mainly powered by
batteries. Figure 6 also shows the energy used by
hydraulics and maneuvering thrusters in the same

Electric power systems and propulsion are extensively
used in offshore vessels. Battery technology has now
reached a level that makes it attractive for installation
onboard these larger vessels but has also made it possible to benefit from electrification on smaller vessels.
The use of batteries is necessary on smaller vessels, as
the power demands are low, and diesel-electric configurations make little sense. Batteries can therefore be
used as buffers to power the entire vessel during lowpower fisheries operations. The electric power system
also makes it easy to measure and document the energy use and operational profile of these smaller vessels.
The data from the operational prototype show that
there is a definite benefit from battery technology, both
from an energy efficiency point of view, with only
required power used, and from a health and safety
view, with reduced exposure to diesel fumes and no
engine noise. The data from the Karoline show that batteries are not only useful as a diesel replacement or a
power buffer to meet peak demand but also for powering vessels in low-power states that arise from the
method of operation. An additional benefit of the time
spent on the battery compared with the conventional
direct drive configuration is the reduction in running
hours of the diesel generator compared with a prime
mover. The diesel generator will only operate when
there is a high power demand, which will be in the
transit condition. Although the transit condition is the
largest energy consumer, the vessel spends approximately 40% of the active time on batteries, which is
directly proportional to a reduction in diesel generator
running hours.

Acknowledgment
The project documenting the energy use onboard the
Karoline is supported by the Research Council of Norway
together with the Norwegian Fisheries Research Fund.

Biography
Karl Gunnar Aarsæther (Karl.Gunnar.Aarsather@sintef
.no) is with SINTEF Ocean, Trondheim, Norway.

IEEE Elec trific ation Magazine / S EP T EM BE R 2 0 1 7

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