The innovations behind Saga’s Spirit of Discovery

Until recently, the company has been operating two cruise ships built in the 1980s. Spirit of Discovery will replace Saga Pearl II, which was sold earlier this year to make way for the new cruise ship. Saga Sapphire will be replaced by a sister to Spirit of Discovery, Spirit of Adventure, when it is delivered in 2020.

Saga Cruises newbuild director David Pickett explains the background to Passenger Ship Technology. “Saga Cruises was established on the back of the well-known holiday company and it has been extremely successful operating secondhand tonnage. It has a solid customer base of 25,000 people a year. When the company went public in 2014, it provided much better access to capital investment and so a new ship to build on the success on the current brand became a possibility.

“We looked at the requirements of a newbuild ship and spent a lot of time talking to customers, which led to the decision on the ship’s size. Our passenger capacity will jump from 25,000 to 45,000 a year in a couple of years, with the delivery of both Spirit of Discovery and Spirit of Adventure.”

Spirit of Discovery stands out in several ways. The first is its relatively small size, with capacity for 999 passengers.

Mr Pickett explains “Our ship is of quite an unusual size in the modern marketplace. There are not many ships of 999-passenger capacity. It was the right size for us, as the Saga experience is typified by small ship style, high standards of customer service and a friendly ship where there is a strong relationship between customers and crew. The ship is 236 m long, 100 m less than mega ships. We have a high crew to passenger ratio. Saga Cruises is a premium brand.”

Furthermore, these ships “give us the ability to give our customers what we cannot do on our current ships”; expand dining choices with three speciality restaurants, a full-size West End theatre and bespoke spa, gym and fitness facilities.

“Other reasons for doing this are the reliability and efficiency these ships offer and future proofing, because older ships are more costly to run. It allows us to reduce maintenance, comply with the latest regulations and it means we can be cleaner.”

Saga Cruises chose Meyer Werft shipyard to build its two vessels. Mr Pickett explains “This is the biggest investment Saga has ever made, and we wanted to minimise risks and produce a high-quality ship with a partner that provided a lot of added value. Meyer Werft impressed us and were able to bring a lot to the design. They have an unparalleled reputation for quality in the cruise ship market, so it was for those reasons we went to them. They were keen to utilise their smaller building hall, which has not been used for a full ship construction for several years, and have two streams of production – one for building mega ships and one for building ships of a more modest size. We took advantage of that.”

Mr Pickett explains that the best way to reduce the carbon footprint of a ship is to reduce fuel usage. He says “In terms of efficiency, the hull design was optimised for our modal speed, which is about 16 knots.

“We worked very closely with the naval architect Foreship on the hull side, who did a lot of basic design for us, and the shipyard itself has highly skilled naval architects who helped to develop the design.”

Innovative pod propulsion

He singled out the ship’s pod propulsion as being important for efficiency. Saga Cruises decided to use Siemens SISHIP SiPODs. Mr Pickett says “These are simple, reliable machines that are proven in service, but it is the first time they are being used on large passenger ships. We had a close relationship with Siemens to develop some of the controls around the pods. The ship is fitted with a Siemens switchboard and a Kongsberg power management system.

“Pods give a much better flow in the propeller and reduce the number of appendages and their effects on the hull. It is a very clean flow over with the propellers compared with conventional shafts and rudder arrangements. This also leads to better hull efficiency.”

Siemens provided not only the pod propulsion system but also the complete power and propulsion package, including the generators, power distribution and propulsion converters.

Explaining the benefits of the system, Siemens Marine head of sales Helmut Behrens told Passenger Ship Technology “It is a unique system with very good hydrodynamic efficiency as it deploys a permanent magnet motor. It is a motor with less auxiliaries and this leads to less failure sources and higher availability. On a traditional motor, you need additional equipment like the excitation system.

Furthermore, he explained that cooling the motor is accomplished by the surface of the motor housing being adjacent to the seawater. “So there is no enforced cooling of the motor needed as seawater used,” says Mr Behrens, pointing out that conventional products are cooled with chilled water. Therefore, Siemens’ pod propulsion system saves energy.

Explaining the major considerations, Mr Behrens says “From the beginning we collaborated with the shipyard to integrate the ship propulsion units into the hull, which is necessary for the hydrodynamic performance of such a vessel. This product is special and to have the optimum benefit in respect to efficiency it has to be properly integrated into the ship hull.”

Speaking about the benefits of using one supplier for the whole propulsion package, he says “We are a systems integrator so responsible for the whole power and propulsion plant. It is a big benefit for the operator to have one point of contact if something comes up.”

“Perfect manoeuvrability” is also a benefit of the propulsion arrangement. Mr Behrens explains “The traditional two shaft line configuration has at the aft end two shafts with the propellers, bow thrusters and a stern thruster. But in our case the propulsion units turn 360°, so they do not need stern thrusters and manoeuvrability is perfect. You have full propulsion power available for a sideways thrust.”

Spirit of Discovery is powered by four, nine-cylinder 32/44 common rail MAN engines, each producing 5,400 kW.

Each engine is fitted with selective catalytic reduction equipment, allowing the ship to be Tier III NOx compliant.

Four Yara scrubbers are fitted. Mr Pickett says “Yara is probably the leading manufacturer of cruise ship scrubbers in a developing marketplace. We wanted to go with an established and reliable partner with a large number of references. Yara scrubbers were compact enough to be able to work with a relatively small envelope within the exhaust stack.”

Mr Pickett also singled out the energy efficiency of the HVAC system, where Engie multi compressor chillers are used, each with six high-speed compressor units on its base frame enabling the demand from the air conditioning system and chill water to be matched very closely. Mr Pickett says “We are looking at this as an investment that is paying for itself. It is not something we started out to do – but we are looking to pay that off within three years, if not sooner.”

Enthalpy recovery wheels are fitted to the air handling units and fan coil units are located next to the cabins to optimise efficiency. “It means that they will be energy efficient, therefore not cooling down in order to heat up but very closely matching demand to the load,” says Mr Pickett.

Waste heat recovery focus

Mr Pickett said that waste heat recovery was an important part of the ship’s energy saving strategy. “We considered how we could combine different systems to use waste heat and reduce pumping energy.”

Highlights include:

Separating the pod cooling and thruster cooling system from the auxiliary low temperature (cooling) circuit allows the system to be optimised.
Having the pod cooling off in port saves at least 36 kW per hour pumping power.
A centralised heating water system combining heat recovery and air conditioning reheat system consumption supply, electric load, steam cooling water balance lead to 200 MWh per annum saved, through a 65 kW reduction in required pump power.

CO₂ is used for cold room refrigeration. Mr Pickett says, “We are using non-ozone depleting refrigerant and have to run at higher pressure than conventionally used with refrigerants but it allows us to be forward looking.” Indeed, not only will adopting -this zeroODP refrigerant save fuel, but it goes towards meeting the new EU F gas regulations.

When it comes to the ship’s interiors, Spirit of Discovery is described as British contemporary classic. Mr Pickett expands “We mean that the ship should be reminiscent of a good London modern hotel and be recognisably British cutting-edge design.”

Spirit of Adventure will also encompass this theme, but the two ships are being designed by two different designers – SMC Design for Spirit of Discovery and AD Associates for the second ship – each with their own take on these principles.

Mr Pickett says “We are a small cruise line, we will have a small number of ships and while we want continuity within the two ships, we also want to provide choice. Therefore, we are using different designer interpretations of overall guidelines and making changes to the dining and entertaining options.”

The two ships stand out as having the highest number of cabins for single passengers of any cruise ship today, with 20% of cabins designed for single travellers.

As well as very closely meeting customer requirements, Saga’s new cruise ships have been built using cutting edge technology and solutions that will greatly boost energy efficiency and reduce impact on the environment.

Spirit of Discovery main suppliers

Main engines	Man Diesel & Turbo
Electrical power and propulsion	Siemens
Stabilisers type s700-16.02m	SKF Marine
Transverse thrusters	Brunovoll
Low voltage electrical motors	WEG Germany
Boiler plant	Alfa Laval Aalborg
Boiler plant	Alfa Laval Aalborg
HVAC chiller plant	Engie Refrigeration
Advanced wastewater system	Wärtsilä Water Systems
Advanced wastewater system	Wärtsilä Water Systems
Dry waste treatment system	Wärtsilä Water Systems



Reverse osmosis plant	SLCE
Life, tender and rescue boat technical spec	Harding Safety
Fuel oil separator and lubrication oil separator	GEA Westfalia Separator Group
High pressure water mist system	Marioff Corporation
Centrifugal bilge water separator	GEA Westfalia Separator Group
Navigation and communication	Kongsberg Maritime
Black water vacuum collection system	Evac
Davits for life boats, tender and rescue boats	Harding Safety
Provision cooling plant	Noske-Kaeser
Fire detection and fire patrol system	Consilium Marine
Local area network	Lufthansa Industy Solutions
MES	Brude Safety
Anchor and mooring winches	Rolls-Royce
Shell doors, tender platforms, lifting platforms and loading hatches	TTS Marine
Low voltage switchboards	Sitte
Technical specification	Almaco
Turnkey installation of galleys and pantry equipment	Almaco
Air handling units	Systemair
Fire extinguisher system	MiniMax Fire Solutions
Paint - hull	Jotun
Paint - underwater	Hempel
Scrubber	Yara Marine Technologies
Ballast water treatment plant	Alfa Laval
WLAN systems	Lufthansa Industry Solutions
Loading computer	NAPA For Operations
EDG exhaust gas silencer	LUHE-STAHL
Plate heat exchangers	APV
Shell heat exchangers	Prang Apparatebau
Mechanical ventilation damper	SAGICOFIM
Pax fan coil units	Halton Marine
Weather protection components for air inlets/outlets	MAC Hamburg
Outfitting of outside areas	Maritec
Balconies and balcony sliding doors	SOMEC