HyPS BV
De Aaldor 8
4191 PC Geldermalsen
[email protected]
www.hyps.nl
+31 345 57 66 64
Harbour Tugs
How a hybrid system can improve your business
A case study by Rudolf van Heek
Are hybrids only green or do they have business potential?
A hybrid harbour tug is nice, green and silent for the environment, but what does it contribute to your
business? Quite a lot, as this case study of a medium sized harbour tug will show. A tug , equipped with a
hybrid system well dimensioned and managed for its operations, compared to a conventional tug, will
have a higher availability, potentially more turnover, lower fuel costs, less maintenance and a longer
lifetime of its main engines. These factors all contribute to a better P&L.
Conventional tug and operational profile
HyPS has compared a conventional harbour tug to a
hybrid alternative with the same performance.
Typically the conventional tug has 60 tons of bollard pull
delivered by twin propulsion lines of 1900 kW each. The
operational profile of the tug shows that it is berthed for
30% of the time. During operational hours the tug has
long low load operations mixed with medium load transit
and towing and very short periods of bollard pull. The
equipment is designed to provide bollard pull and in
practice suffers from low load operations. Under low
load diesel engines run inefficient, pollute internally and
to the environment, require more maintenance and wear out much quicker. The required frequent
maintenance results in income losses due to unavailability.
Design objectives for the hybrid tug
The hybrid tug is designed to strongly reduce the low load running hours of the main engines. The hybrid
combines diesel propulsion and diesel electric propulsion to deliver maximum power for bollard pull. The
diesel electric propulsion provides power for low and medium load circumstances, during which the main
engines can be switched off. A battery system is essential for peak shaving, fast electric response to load
changes and avoiding low load on the generators.
The HyPS hybrid tug
Based on the operational profile of a harbour tug HyPS has designed a system that consists of two 1500
kW main engines combined with two 400 kW electric machines. They are powered by two 400 kW
generators and supported by a 120 kW battery system and a management system that controls and
optimises the operational settings of all the elements.
This well configured and managed hybrid system is capable of avoiding most of the low load operations on
its engines. This leads to lower fuel consumption and less internal engine pollution. Consequently the
maintenance intervals are longer and the engine lifetime expectancy is much better. This results in a
decrease of both maintenance costs and engine depreciation. Moreover the increased availability creates
the opportunity for a higher turnover.
The operational effects
Where the conventional tug runs its main engines over 6000 hrs/yr. of which more than 5000 under low
load (<40%), the hybrid tug runs its engines less than 2200 hrs/yr. and avoids low load running.
Both factors, less running hours and less low load, reduce the need for maintenance considerably by that
contributing to a better availability and additional business.
Case study hybrid tug
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A comparison between the conventional and the
hybrid tug shows the following effects:
 The hybrid will generate more turnover
because it has a better availability.
 The hybrid will save on fuel costs because
the engines are more efficient when
properly loaded. Fuel consumption can go
up as much as 100% under low load.
 The hybrid uses more shore power,
because it charges its batteries when
berthed.
 The conventional tug has higher
maintenance cost due to more running
hours and also the effect of low load which
increase the need for maintenance.
 The hybrid’s main engines have less
depreciation because they run less hours
and wear out less quickly.
Assumptions on low load operations:
 Maintenance intervals decrease with 40%
 Engine lifetime decreases with 40%
All these effects add up to an operational difference of
around 400-500 k€/yr. (OPEX).
Is the hybrid system worth the investment?
The hybrid installation requires initial investment in additional equipment, but at the same time creates
savings on conventional equipment which can be smaller or becomes obsolete. Overall the investment for
the hybrid is around 900 k€ higher than its conventional alternative.
When looking at the payback period of the
hybrid we see that this is sensitive to the MGO
oil prices which have recently fluctuated
between 900 and 300 $/ton. The comparison
shows that at an oil price level of $400/ton the
payback period will be less than three years.
Should oil prices rise the payback period will be
even shorter. Assuming the tug will be
operated for an extended period the financial
benefits increase with time.
In this investment analysis the effects of the
reduced environmental impact is not
considered. However, the hybrid system will
enable the ship to operate cleaner and comply with stricter environmental regulations.
Conclusion
When focusing on CAPEX only a hybrid requires a higher investment. However the operational expenses
(OPEX) are more favourable for the hybrid. If the financial horizon exceeds 3 years the hybrid alternative is
definitely a sensible and financially attractive proposal. In order to achieve this it is conditional that the
hybrid system is dimensioned for its operational profile and managed according to its objectives.
So actually, greener operations and an attractive business perspective go very well together.
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