SIEMENS

Is that a ship? Or should it really be called a floating city? The luxury cruise ship Celebrity Solstice of the U.S. cruise line Celebrity Cruises has room for over 2,800 passengers and even features a 0.2 ha golf course. Inside this floating hotel there are ten restaurants and a theater that seats over 1,100 passengers.

That much luxury turns a trip into an unforgettable experience—but it also costs a great deal of energy. According to the Hamburg University of Technology, a modern cruise ship consumes between ten and 12 kWh per passenger every day for propulsion, air-conditioning, lighting, and the other amenities, which is equivalent to the energy use of a German household of three persons on land. Well aware of this discrepancy, the newest luxury liners, like the Celebrity Solstice, are turning to lighting systems from Siemens subsidiary Osram. The result: reductions in energy consumption and related CO₂ emissions of about 12 % — that represents 3,000 t of CO₂ reductions and $300,000 in savings per year. In addition, the such lighting systems reduce the total weight of the ship by up to eight metric tons.

On the Celebrity Solstice, light-emitting diode (LED) modules from Osram provide mood and accent lighting in the casino, discotheque, restaurants, and at many other locations on board. They create lighting effects that can't be matched by conventional lamps. Each module consists of 200 three-color LEDs, and the light they produce can be used to mix almost any color. At the same time, they consume far less energy. Compared with neon fluorescent lamps—one of the light sources used for accent lighting in the past — they consume approximately 60 % less power.

“LEDs are also smaller and lighter,” says Kristina Kaase of Osram Sylvania in the U.S. “And since they're not rigid and don't have a predefined color and shape like neon lamps, they're also easier to replace.” In the future, these innovative light sources will also be used for general-purpose lighting on ships — which is currently difficult because of a lack of global standards for such lamps. In the case of halogen bulbs, technical lighting parameters such as color, beam angle, and luminous flux are standardized, but there is still great variation in this regard among LEDs. “We're working with other companies on a standard,” says Kaase. “In a few years, LEDs will be very common in general-purpose lighting.”

There's a simple reason why dockyards and ship operators are so interested in energy-efficient lamps. On a cruise liner, up to 40 % of the fuel not used for propulsion is consumed by lighting systems. Energy-saving lamps can therefore make a big difference. On the Celebrity Solstice, for example, energy-saving lamps are used for general lighting in the cabins. These lamps use 80 % less energy than conventional incandescent bulbs and last up to 20 times longer. Highly efficient halogen bulbs from Osram are being used in built-in ceiling lights. They have a special infrared coating that transmits heat, which is inevitably produced, back to the filament, thereby reducing energy consumption by as much as 35 %.

Engineers have even tweaked conventional fluorescent lamps to bring their energy consumption down to a minimum. These are mostly used to illuminate non-public areas such as the corridors to the crew cabins and the engine room. All fluorescent lamps require ballasts that limit the flow of current. The conventional version uses a relatively inefficient coil, but on the Celebrity Solstice, electronic ballasts are used. Their circuits operate the lamps at a frequency of between 40 and 50 kHz instead of the 60 Hz mains frequency — that doubles the service life of the lamps and cuts their power consumption by up to 40 %.

But without a doubt the future of lighting belongs to LEDs and their younger siblings, organic light-emitting diodes (OLEDs), which can be integrated into window panes and mirrors as transparent light sources (see Pictures of the Future, Spring 2010, Organic LEDs). “Osram already offers the first OLED panels. They open up entirely new possibilities in accent lighting,” says Kaase. Since 2007, Osram has had an agreement with the Meyer Werft shipyard in Papenburg near Germany's North Sea coastline. Meyer Werft is one of the global market leaders in cruise ships and is the builder of the Celebrity Solstice. At the end of 2010, the two companies will launch a research project devoted to cabin lighting of the future, with LEDs playing a central role. And it isn't just the environment that stands to benefit from this. “With oil prices high, the somewhat greater acquisition costs of modern lighting technology can be paid for in only two years,” Kaase calculates.

The Power of Prediction. In addition to lighting, modern engines and equipment for controlling and monitoring on-board systems are also essential for reducing energy consumption. Cruise ships have very quiet, low-vibration diesel-electric propulsion systems. Four to six diesel engines, usually housed in pairs in separate rooms for safety reasons, drive generators that provide electricity for the propulsion system's electric motor and for equipment that consumes electrical power.

Power-management systems from Siemens switch individual diesel engines for the generators on or off depending on energy needs. This allows the active engines to usually be run at their optimal operating point, corresponding to between 85 and 90 % of maximum output. Systems of this kind are used on board the AIDAdiva and other cruise ships operated by AIDA Cruises, for example.

In the future, a predictive technology could also remove individual users of energy from the network for short periods and thus achieve an even higher level of optimization. “In order to handle load peaks, for example, we could shut down the refrigerated hold for a short time,” says Kay Tigges of Siemens Marine Solutions in Hamburg. “It's important that the entire system always operates as close to the design point as possible, because that maximizes efficiency.”

Using neural networks, developers want to make the system adaptive, so that it can learn from its data and give the crew recommendations for energy-efficient operation based on specific situations. It is conceivable, for example, to establish the sequence of operating situations in advance and then optimize power generation accordingly — by, for instance, partially shutting down wellness areas during public events like dinner or theater performances. “The system is currently under development, and a few cruise lines have already expressed interest,” says Tigges. One of the biggest power users on cruise ships is air-conditioning. Plenty can therefore be saved if individual units are switched on only when passengers are in the rooms.“