The Oasis of the Seas debuted in December 2009 as the world's largest and most innovative cruise ship, featuring many cruise industry firsts. Energy efficiency and a low carbon footprint per passenger were central design criteria. The figures are impressive.
— MONDAY, 23 NOVEMBER 2015 BY DANFOSS DRIVES
The Oasis of the Seas is a massive, 361-metre-long (1187 ft) floating wonderland offering ‘WOW’ experiences. The Oasis is bigger and more versatile than its predecessors, but has still improved its overall energy efficiency by 15 % to 25 % and has a low carbon footprint per passenger. “We consider that the energy efficiency per passenger of the Oasis is some 50 % better than the average 10-year-old cruise ship,” says Harri Kulovaara, Executive Vice President at Royal Caribbean Cruises Ltd. (RCCL). “The benefits of scale are naturally one aspect, but the important thing is to realize how focused work in each area of energy consumption can lead to enormous savings,” he says.
Innovative HVAC solutions improve overall efficiencyAfter propulsion, HVAC (heating, ventilation and air-conditioning) is one of the main energy consumers onboard, accounting for roughly 30 % of the energy consumed. So a sophisticated HVAC monitoring and control system was designed for the Oasis, utilizing extensive expertise and knowhow. The ship owner reports savings of close to 30 %.
The entire air-conditioning systems onboard the Oasis and its sister vessel the Allure of the Seas to be launched in October 2010 are the result of a major cooperation project, with Finland-based Koja Marine as the main contractor. Koja Marine is known as a supplier of air conditioning systems to the world’s most exclusive cruise liners, and RCCL had asked the company back in 2004 to present its latest ideas and technologies for an optimized system.
Utilizing its extensive experience in advanced land-based installations, Koja Marine designed an energy-efficient system that provides maximum passenger comfort but occupies a small system footprint, so as to maximize the passenger areas and minimize the technical areas. The design of the HVAC plant, for instance, has been improved by moving many of the fan-coil cooling elements out of the air conditioning room and closer to the public areas, and modern technology is used to control air flows. The Oasis uses the latest AC room technology, with direct driven, frequency-controlled fans in the air-handling units and stainless steel casings, minimizing energy consumption and the need for service.
“The air conditioning system onboard the Oasis of the Seas uses no more power than that on the Freedom class vessels, which is a major achievement considering that the interior area is 43 % larger,” says Koja Marine Director Esko Nousiainen.
Vacon AC drives control temperature and humidityThe need for air-conditioning onboard varies depending on the specific function in an area and the number of passengers present. The 350 Vacon AC drives are a key technology that help Koja Marine meet this challenge, providing stepless speed control of the fan coil units.
Vacon AC drives control the temperature, ventilation and level of humidity in the public areas, ensuring better air quality onboard. The level of carbon dioxide is measured in the public areas, and the operation of the fan coils is adjusted accordingly with the help of Vacon AC drives, resulting in optimized energy consumption.Vacon AC drives are silent when operating since they require no large built-in fans, so the air conditioning system does not cause any disturbing noise. All this adds to passenger and personnel comfort.
The wide selection of factory-ready applications in the Vacon AC drives was a major benefit in the Oasis project. “The versatility of the applications enabled a wide use of the AC drives in various process control and monitoring tasks on the Oasis. A number of the field I/Os are connected to the Vacon I/O board: some are used for the vessel’s automation via the Profibus fieldbus and some for controlling the AC drives when the air-handling unit is controlled locally,” Mr Nousiainen explains.
Central Park, the large open area at the centre of the ship, is a major challenge for air conditioning. The air conditioning systems for cabins and public areas and the air conditioning automation system represent totally new technology, featuring a number of innovative solutions not previously applied on cruise vessels that improve overall efficiency.
Fan control via ProfibusThe Oasis of the Seas is the first cruise liner where the Vacon AC drives are connected to the air conditioning system via Profibus. The fieldbus technology reduces the amount of wiring and the number of connections, cuts the costs for installation, commissioning and service, and makes the system more resistant to malfunctions.
The fieldbus technology also offers almost unlimited possibilities for control commands and access to a wide range of measurement and control data on the process itself. Mr Nousiainen gives a practical example that directly relates to energy efficiency. “The Profibus fieldbus provides access to motor power values. The ship owner is therefore able, in real time, to monitor the amount of energy used by the process. Changes made by a passenger to the values in the HVAC automation system and their effect on energy consumption can be perceived instantly.”
Long-term cooperation with Koja MarineSince 2000, Vacon has supplied Koja Marine with thousands of AC drives that control the fans in Koja’s air conditioning systems used onboard some 20 luxury cruise liners — most of which are sailing in the Caribbean. Vacon’s scope of delivery to Koja Marine includes air-cooled AC drives up to 50 kW, mainly 380 - 500 V units in IP54 enclosures, providing a high degree of protection against humidity.
Working closely together, Koja Marine and Vacon have demonstrated their ability to provide reliable, high-performance and energy-efficient air conditioning technology to the marine and offshore industries, one of the most challenging sectors. “Cooperation with Vacon, during the Oasis project but in general as well, has gone well,” says Koja Marine Director Esko Nousiainen. “Vacon has addressed Koja’s views very well, for instance by changing the parameters and functions according to our needs. This also applies to Vacon’s new products, so that older generation drives can be replaced with newer drives.” He also appreciates the reliability of the drives and the technical support and service provided by Vacon. “The Vacon AC drives have operated reliably, and Vacon has resolved the minor problems that have occurred over the years quickly and in a spirit of cooperation. AC drive deliveries have caused no delays in commissioning our HVAC systems,” Mr Nousiainen concludes.
FactsFans used in air conditioning systems often use excessive amounts of energy. This is particularly true of a vessel featuring 2704 staterooms. Stepless speed control of the fans by means of AC drives allows considerable energy savings to be achieved. Koja Marine is also responsible for the air conditioning technology on the Allure of the Seas, which will be launched in October 2010. Koja’s fans are controlled by Vacon AC drives.
AC drives provide variable frequency power supply to the motor allowing the speed of the motor to be controlled in direct relation to the frequency. The ability to control the speed of the motor gives several benefits:
control of the output from the process to match the need
reducing the start-up current, making it possible to use smaller fuses and supply connections and reducing peak loads on the electrical grid
reducing the mechanical shock in start and stop situations
saving electrical energy compared to conventional methods of process control. In pump and fan applications, for instance, energy savings are typically 20-50 %.
Five times larger than the Titanic, the Oasis of the Seas is the largest and most revolutionary cruise ship in the world. Unique industry firsts include a neighbourhood concept - seven main themed areas providing pools, spas, an ice rink, a miniature golf course and a 750-seat outdoor amphitheatre, restaurants, and more.The Oasis of the Seas has altogether some 400 Vacon AC drives onboard, 350 controlling Koja Marine’s fan coil units and the remaining 50 controlling other applications on the ship.
Length (overall) 361 m (1187 ft)
Draught 9.1 m (30 ft)
Breadth, max 66 m (208 ft)
Air draft 72 m or 65 m with telescoping funnel pulled in
Gross tonnage, GT 225,282
Net tonnage, NT 242,999
Engine output, total 97,020 kW
Number of passengers, max 6360
Number of passenger cabins 2704
Crew 2165
This case story was originally released before the merger of Vacon and Danfoss Power Electronics was fully completed on 15 May 2015. The contact persons mentioned in the story may have changed. Future case stories on VACON® products will be released on behalf of the new organization – Danfoss Drives, one of the four business segments of the Danfoss Group.