ALTERNATIVE PROPULSION SYSTEMS FOR SUPERYACHTS
HOWARD LOWEMEng CEng MRINA
Superyacht Claims Adjusters Association, 24 April 2019
CONTENTS
Why change?Traditional mechanical propulsionDiesel electricHybrid propulsionHybrid modes of operationHybrid system exampleMarine use of batteriesOther fuels – HydrogenSummary
What are the driving factors?• Regulations, IMO Tier III - NOx and SOx reductions • IMO initial strategy to reduce Greenhouse Gas (GHG) emissions by 50% by
2050 compared to 2008 (April 2018)• IMO target zero emission by end of this century• Owners who care about the environment, pollution, fuel consumption and
operating costs• 30-50% increase in fuel costs in the next decade• New technologies are now available for marine use
WHY CHANGE?
UNESCO-protected Norwegian fjords shall be free from cruise and ferry emissions no later than 2026
“The insight I have into the commercial shipping sector (as we operate both in the offshore supply field as well as deep sea fishing) has given me loads to think about when it comes to the development of my boats. Big motor yachts are, as it stands, some of the most inefficient vessels in the world when compared to heavy-duty commercial vessels and their lives at sea.”John Risley, Superyacht Times, 8th November 2018
TRADITIONAL MECHANICAL PROPULSION
Propulsion system is independent to power generation system on board
Shore power
Hotel load
Propeller & shaft
Reduction gearbox
Electric motor PTI/PTO
Diesel main engine
Diesel generator
Battery storage
Switchboard/electrical hardware
DIESEL ELECTRIC
No mechanical transmission to the propellers
Shore power
Hotel load
HYBRID PROPULSION“A thing made by combining two or more different elements”Significant change here is the addition of E-motors and combination gearboxes allowing electrical power to be used for turning the propellers (PTI) and also allowing the main engines to generate electrical power (PTO), battery storage has also been added to allow peak shaving
Shore power
Hotel load
Optional
HYBRID MODES OF OPERATION
Traditional Mode – E-motors on the gearbox are not engaged so propulsion power and generators remain separate systems, battery storage is being used for peak shaving
Shore power
Hotel load
HYBRID MODES OF OPERATION
Full speed Mode – total shaft power is provided by both main engines and E-motors on the gearbox, power generation is now combined with the propulsion system
Shore power
Hotel load
HYBRID MODES OF OPERATION
Cruise Mode – Main engines are able to provide propulsive power and also generate electric power for use on board hence all generators are off and battery system is used for peak shaving
Shore power
Hotel load
HYBRID MODES OF OPERATION
Eco Cruise Mode – Similar to the previous example however all propulsive power and electrical power is provided by a single main engine, significant speed and electrical power restrictions will apply
Shore power
Hotel load
HYBRID MODES OF OPERATION
Shore power
Hotel load
Economical Mode – “slow speed” – only generators are running to provide both electrical power for the hotel services and also to the E-motors on the gearboxes for propulsion, speed will be limited by the power of these E-motors
HYBRID MODES OF OPERATION
Silent Mode – all power is supplied by the battery system, very significant speed and power limits will apply as well as the length of time that the yacht can operate like this
Shore power
Hotel load
HYBRID MODES OF OPERATION
At anchor/in harbour Mode – shore power and/or a generator can be used to recharge the battery system, the yacht could also operate on just the battery system for a period of time depending on battery capacity and power demand
Shore power
Hotel load
Sunseeker yacht with MTU hybrid propulsion system
HYBRID SYSTEM EXAMPLE
2 x 1,947 hp12 cylinder diesel engines6 modes of operation
ADVANTAGES• Reduced fuel consumption• Improved loading on all diesel engines
(cleaner emissions) • Improved operational flexibility• Reduction in installed power and hence
space required• Reduced noise and vibration levels
DISADVANTAGES• Increased system complexity and
equipment costs• More components to maintain and
operate (crew factors)• Additional safety considerations with
batteries
HYBRID SUMMARY
• A battery is an electrochemical system that can store energy
• Can be retrofitted to existing yachts• Li-ion technologies now delivering
higher energy densities and reduced cost
• Battery system design needs careful consideration
MARINE USE OF BATTERIES
• Battery space – A-0 or A-60 compartment (machinery space)• Software for control and alarm & monitoring must meet class rules• Operation – crew need training, specific procedures and documentation• Maintenance – inspection of sensors, access to replace cells (safe disposal)• Classification societies take a risk based approach rather than a specific type
approval process for battery systems due to many different technologies and their continuous development
BATTERY – SYSTEM CONSIDERATIONS
Safety aspects to consider:• Cell failure• Internal or external short circuit• High temperature (ideal range 20°C -
30°C)• Excessive external heat or fire• Overcharge or overdischarge
Resulting consequences:• Gas development• Thermal runaway• Fire risk• Explosion risk
Other considerations in the marine environment: Grounding, collision, submersion risk
BATTERY – SAFETY CONSIDERATIONS
The use of battery storage to absorb peaks in power demand preventing intermittent operation of another generator
PEAK SHAVING
Hydrogen technology is now mature, safe and reliable and making its way into the marine industry • Fuel cell manufacturers are joining up
with marine integrators • Fuel cells are included in propulsion
for small vessels with low autonomy • Fuel cells are suitable for integration in
hybrid propulsion systems for yachts• Supply infrastructure is a challenge
and requires an industry wide effort
OTHER FUELS - HYDROGEN
Many fuel cell types exist using different fuels, but PEM type using hydrogen is most common• Low temperature chemical conversion
> 100 °C• Thermal efficiency 55% representing a
technology shift • Zero emission steam output• Modular (150 to 200 kW) & scaleable to
MW output
FUEL CELL BASICS
Gas: High pressure, 300 - 700 bar in carbon tanks (11kg of H2 per cylinder at 500 bar) 40ft container shown carries 1.15 tonnes of hydrogen at 500 barLiquid: 1 m3 of LH2 is 71 kg – Tank shown is 3 tonnes of LH2 with a storage volume of 42 m3
Fitting such volumes inside a yacht is a challenge, storage technology is available and marine type approved
HYDROGEN STORAGE - A CHALLENGE
• Hybrid propulsion is becoming available to help reduce emissions and fuel consumption
• Battery technology is now suitable for marine applications• Peak shaving is important for improving efficiency of new and existing yachts• New regulations will require changes to be made• Hydrogen technology needs to be verified in the marine industry through various
research projects • Changes in shore infrastructure remain challenging, particularly for H2 and LNG• Suitable training and operational considerations must not be overlooked
SUMMARY
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