STEALTH 380 hybrid
objective The design objective of this craft is to provide a small, efficient passenger vessel with the lowest possible Carbon Emissions in anticipation of everincreasing environmental legislation, whilst at the same time providing levels of passenger comfort with reduced journey time comparable with current vessels. The STEALTH 380 hybrid is based on the proven efficient HYSUCAT (HYdrofoil SUpported CATamaran) hull used by the STEALTH 520 RUV, but extends the concept further with the introduction of a hybrid diesel-electric propulsion system. This innovative product should not only serve operators and users alike,
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but also avail itself of eco-friendly technologies that are de rigueur in today’s environmentally conscious society.
design concept The most significant factor in reducing operating costs and CO2 emissions is the reduction of the vessel’s fuel consumption – more specifically, a reduction in the fuel consumption per passenger per journey. Unfortunately, at present, propulsion systems technology has not developed enough to allow a simple solution to this problem. The design of the STEALTH 380 hybrid will use a combination of the following design factors to meet this requirement:
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efficient stealth hull technology The hull design is based on catamaran hulls as these hull forms give a characteristically soft ride (most notably in rougher water), a proportionally larger deck area for a given hull length (for increased passenger space) and a lower running resistance than a conventional monohull. Using the HYSUCAT principle, hydrofoils are used to assist in generating a high proportion of the lift required for the vessel to plane. As this lift is generated at higher efficiency values than the hull planing surfaces, the overall efficiency of this hybrid hull/foil combination is further increased.
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efficient low co2 emmisions engine technology Virtually all the work done to date on environmentally conscious propulsion systems relates to electric-powered sailing vessels or large, well understood, diesel-electric systems (which have been in use for 100-odd years) used in locomotives, large mining vehicles, certain types of tugboats, etc. The big difference with small-craft is the requirement to use batteries as a means of energy storage and PhotoVoltaic (PV) panels as an alternate energy source which is not possible on large instillations.
As the first commercial diesel-electric propulsion systems for small vessels are now commerically available, this technology-type will be used for the STEALTH 380 hybrid - the photo below shows and example of a Steyr Motor’s (Austria) hybrid propulsion package consisting of a 7kW electric engine (green) directly connected to a 185kW diesel engine (grey)
The automotive industry has gone another route and use an electric engine for low-power requirements and a smaller (than normal), conventional (petrol or diesel) engine for higher power requirements (longer distance or higher speed) – hence the term hybrid. 5
efficient propulsion technology STEALTH yachts have extensive experience with the use of large surface propellers for efficient high-speed propulsion. Electric motors produce a high output torque at low speeds. This requires a much larger propeller on any electrically driven boat compared to conventional motors. The disadvantage being that the propeller is over-sized for higher speeds. With the use of surface propellers, the unique requirements for both electric engine propulsion at lower speeds and diesel engine propulstion highspeeds can be uniquely combined to match the power output from a hybrid drive system!
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hybrid power concept The parallel diesel-electric hybrid system backs up the low-emission, electronically-controlled diesel engine with an independent electric propulsion motor. The propulsion motors are connected together and either independently or in combination they drive the propeller shaft. The advantage of this two-tier system is that it recognizes that the strength of the conventional diesel engine lies in its high-end output and does not compete with this – it adds a zero-emission, quiet electric engine to the power train for use in slow speed maneuvering and motoring when the use of the diesel engine is inefficient. The diagram, representing the Steyr Motor’s Hybrid Marine Propulsion system, shows the typical components installation. The chart indicates the various engines installed in comparative craft.
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modes of operation Electric power only: In low-speed electric propulsion mode, operation will be quieter with zero CO2 emissions. The diesel engines are not used and power is drawn from light-weight Lithium-based batteries. Operational speed will be 6 knots for a duration of two hours. This mode is intended for harbor use and slow approach and departure speeds in high traffic areas or environmentally sensitive areas. Diesel engine with electric engine driven as an alternator to charge batteries: This is the normal cruise mode at 28 knots in open water. The diesel engine operates at its most efficient point (lowest fuel consumption per unit power produced thus lowest possible CO2 emissions) whilst using the electric engine in “reverse� mode as a generator to charge the propulsion batteries. Diesel engine only: This mode will occur if no battery-charging and no additional propulsive power is needed but will not be a normal operating mode. 8
Diesel engine supplemented by additional power form the electric engine: This mode can be used where more power is needed than can be supplied by the main diesel engine – the output from the electric engine can be added to that of the diesel engine.
advantages There is no degradation of cruising (higher speed) operational performance as propulsion in this mode is from the normal diesel engines.
Alternative zero or low emission energy sources can be used for battery charging such as PV solar panels or shorepower when docked.
Electric propulsion will take over at precisely the point in the diesel engine power equation where it is becoming increasingly inefficient and specific fuel consumption in relation to output power is poor.
A supplementary advantage of this diesel-electric hybrid system is that a third auxiliary engine in the form of a generator is not added to the vessel for powering air-conditioning and other on-board electrical power systems – in the second operating mode described above (the normal operating cruise condition), electrical energy for these systems will be provided by the electric propulsion motor operating in “reverse� mode as a generator.
When in electric propulsion mode, there will be quieter operation, enhanced low speed maneuverability and other non-efficiency related benefits. Propulsion power will always be instantly available as it will be possible to run the vessel for several hours with the electric motors using battery power.
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environmental impact
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principle characteristics Length overall (LOA): Beam Maximum: Dry Weight:
11.8m 4.2m 7,000kg
38ft 6in 13’ 10” 15,400 lbs
Power: Drive system: Hydrofoil system: Speed: Capacity: Time on electric power:
2 x 280hp (185kW) Diesel plus 2 x 10hp (7kW) Electric STEALTH surface drive system Tandem hydrofoil set Maneuver (Elec) 6 Kts - Cruise 28 Kts - Max 34 Kts 2 Crew and 30 Passengers 2 hours
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contact:
www.stealth-technology.com This document is not contractual. All descriptions and illustrations are only indicative. We reserve the right to modify or improve our product without notice. November 2010