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Green Shipping I Efficiency
Gen erating efficiencies from
thin air
Air lubrication systems are a credible technology for ships saving fuel,
and therefore costs and greenhouse gas emissions. {u$*afu S€8fu*rs*&em7d?
from DK Group describes the impact on the global fleet
6 hippingsperspective on clean technolotJgy is undergoing a sea change as the
industry begins to adopt innovative solutlons, driven by high fuel prices, impending
regulation and ongoing commercial pressures to increase efficiency and reduce operational costs. This shift in perception reflects the attitude that sustainability is gradually becoming accepted as a business imperative rather than just a brand-driven
luxury. As this behavioural change continues, so the opportunities and benefits that
can be delivered by clean technology will
grow alongside it.
Ofall the clean technology options, there
is a growing awareness in the industry that
it is air lubrication that delivers on its fuelsaving promises and can make a significant
positive impact on commercial operations,
emissions reduction and both the existing
and future fleet. As a result, air lubrication
providers are continuing to innovate and
demonstrate tangible results, both in test
facllities and increasingly on board ocean-
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reduced greenhouse gas emissions
super Micro Bubbles
Mid ship section
going vessels.
There are several solutions being offered
in varying stages of testing and development and that claim varying degrees offuel
and emissions savings, but trialling the
technologies and seeing demonstrable results based on commercial vessels in reallife operations is crucial to greater take-up.
DK Group's patented air lubrication technology, the
Air Cavity System (ACS),
to lubricate the flat
bottom area of ships and uses air bubbles
on the boundary layer of the vessel, thus
reducing frictional resistance between the
water and the hull surface, propulsion
power and therefore fuel costs
ACS is designed
Super Micro Bubbles
been shown to deliver fuel savings and
therefore emissions reduction of up to l0 7o,
dependent on vessel size and type. ACS is
designed to lubricate the flat bottom area of
ships and uses air bubbles on the boundary
layer ofthe vessel, thus reducing frictional
Less fuel consumpti-
on also results in
reduced greenhouse
gas emissions
resistance between the water and the hull surface. It is engineered to
place the bubble generator under the ship, enabling the technology to
create and maintain a rigid bubble carpet that is more realistic and
organic. Air cavities (chambers) are arranged at the front ofthe bottom
of the vessel. The chambers are then fiiled with air. The bubbles created have a specific structure and are then carried past the chamber
and into the boundary layer of the vessel. This significantly reduces
propulsion power demand and fuel consumption, and results in reduced greenhouse gas (GHG) emissions.
The size, geometry and number of cavities required depend on the
size and type of the vessel. Each cavity has its own independent compressor, pipe and control system. The process is controlled by DK
Group's patented software. Sensors inside the chambers monitor the
surface and relay information back to the air system on the amount
ofair needed.
The investment payback period for retrofit will range between 18
months and three years, and on a new build this payback period reduces to around six months. Downtime is minimal and no specialist
ship equipment is required, making this a relatively simple procedure
for most shipbuilding and repair yards. The ease of installation is a
critical factor in the mass adoption of any technology, and the low
order complexity of ACS means that instaliation is scalable in line with
the growing demands of shipowners looking to complywith incoming
emissions reduction regulation, as well as capture crucial fuel savings.
ACS as retrofit
There is only a small group of solutions in the market that can deliver double-digit fuel savings dependent on vessel size' When such
significant results are claimed, it is vital that they are substantiated with
credible and empirical evidence. This is particularly important given
the reported threat of a two-tier market, which is driving shipowners
to consider scrapping ships. However, this does not need to become a
self-fulfilling prophecy, as there are credible solutions available now
which negate this situation. The choice is simply not new build vessels
or scrap; there is an available alternative - retrofit technology.
Retrofit represents a significant opportunity for all shipowners to
access the commercial benefits of clean technology. Within air lubrication, DK Group's ACS is avail-able as a retrofit option as well as for
newbuild vessels. The structural design impact of ACS on the hull is
minimal and non-invasive, and can be compared to keyhole surgery
for a vessel - there is very little downtime and maintenance needed.
Given cur-rent concerns regarding a potential two-tier market, ACS
Retrofit can extend the lifetime ofa vessel, therefore reducing the need
to purchase new build vessels and maximising the potential of the
existing fleet.
As pioneers of retrofit air lubrication solutions, DK Group is solely
focused on enhancing its technology further, which is driven by invest-
ment in a comprehensive and ongoing R&D programme. Working
closely with hydrodynamic testing and research facility HSVA (Hamburgische Schiffbau-Versuchsanstalt) and classification society Germanischer Lloyd, DK Group has conducted 29 separate weeks of tests
ACS since its inception.
During the last two years DK Group and HSVA have worked together to test a full scale ACS, specifically to improve the cavity geom-
etry to increase the power savings as well as the cavity stability for
automating onboard operations. Testing spanned more than six weeks
and explored different cavities and conditions. This included varying
ship draughts and airflow rates. The total and the local friction forces,
the injected airflow rate, the water speed and the tunnel pressure were
measured continuously, whilst the cavity stability, the bubble tail behaviour and the bubble size distribution were documented and analyzed.
Air lubrication is an active system that requires power to provide
compressed air and for injection ofa certain airflow rate to the areas
lubricated. Test results therefore accounted for this power balance
of the tested ACS model.
The results of these tests have led to the impending installation of
ACS technology on a 12,580 dwt multi-purpose vessel owned by Danish shipowner and ship management company Dannebrog Group
which is due in the fourth quarter of 2012. The sea trials will again be
conducted by HSVA and overseen by Germanischer Lloyd both prior
to and after the conversion to estabiish and benchmark relative fuel
consumption and the associated emission profile.
Naturally the cost and exact saving depends on the individual vessel
to be
if ACS is planned for and installed as partof'a new vessel design.
However, as an example, applyingACS Retrofit-to
payback period of two years. For container ships, payback time is
tipically below two years. As impending environmental legislation
drives shipowners to use significantly more expensive distillate products
as of2015, retrofit and newbuild payback periods will reduce further.
As shipping embarks upon an exciting and challenging new era of
technological development, it will be innovative technologies that
combine cost savings with reduced emissions that will lead the way.
Proven air lubrication technologies such as ACS open the door to cost
savings, emissions reduction and an enhanced competitive advantage
at a time when shipping is undergoing significant change. Air lubrication is one of the most advanced of a new breed of clean technologies
that will play a fundamental role in shipping's future as environment
regulations grow and the industry commits to a more sustainable future.
Noah Silberschmidt
Managing Director, DK Group
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