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

8 ST. JAMES’S SQUARE ST. JAMES’S

LONDON SW1Y 4JU, UNITED KINGDOM

T: +44 (0) 20 8050 5075 www.mayfairmarine.com

SUPERYACHT TECHNICAL CONSULTANTS