There is no single solution – no miracle solution – that will reduce energy demands dramatically on cruise ships tomorrow, according to the classification society experts interviewed by Cruise Industry News. Instead, the cruise lines should look at fuel savings from many aspects and work out their own best models. But with the proper approach, savings of up to 30 to 40 percent can be reached.
“If you increase speed, fuel consumption goes up,” said Andrea Cogliolo, technical sector manager at RINA. “Diesel-electric ships are usually designed to operate at about 20 knots,” he said, “but the last two to three knots require nearly full power. If you reduce the medium speed of your fleet, you can reduce fuel consumption significantly. It comes down to good planning.”
At Det Norske Veritas (DNV), Odd Arne Haueng, principal consultant and energy management practice manager, said: “Many captains are conservative when it comes to speed and passage management. They prefer to ensure their arrival time by speeding up at the start and slowing down or even waiting (hurry up and wait). This is expensive and burns more fuel than required. A speed reduction of only one knot can reduce fuel consumption by 5 to 10 percent.”
At Germanischer Lloyd, Dr. Pierre Sames, senior vice president of strategic research and development, said that most operators today have made moderate itinerary and speed adjustments, and because of the price of fuel, shipowners are more willing to spend money to gain efficiencies.
The best solution may be to change the culture onboard by creating awareness and acceptance of energy conservation, said Cogliolo. “This will require tools to allow the ship to monitor its fuel and energy consumption,” he said.
There is much to gain looking at operational aspects than throwing money at new technology, concurred Haueng, “Besides,” he said, “the demand for certain ship types is so great today that many yards have no choice but to use yesterday’s technologies to build faster and (for them) more profitably. As a consequence, a substantial number of ships being built today are constructed with ‘yesterday’s’ technology,” he said.
“If you can manage the technical and operations sides better via monitoring of perfomance and fuel consumption, as well as retrofit new technology, there are savings to be made on all ships,” said Zabi Bazari, technical manager of ship energy services at Lloyd’s Register (LR).
“There are many aspects to consider,” he said, “whether engines are run optimally, to ensure that they are in accordance with their original specifications, and in proper tune; or that hull and propellers are kept at a reasonably clean condition; that auxiliary machinery are run in a more load-optimized way; or that the energy demand side is better managed.”
Today, energy is generated from the reaction between oxygen and carbon. “Apart from nuclear, wind and solar power, we have no other chemical reaction except carbon to generate sufficient energy,” said Cogliolo.
While diesel electric is the most practical solution today, it may not be the most efficient solution, converting fuel to mechanical energy and to electricity, said Sames, who also noted the additional electrical equipment and machinery required. Direct drive would be most efficient for propulsion, he said, although the diesel-electric concept is more flexible for cruise-ship operations.
“The future must be fuel flexible,” said Bazari. “The owners must look inside the vessel for heat recovery, using the heat from the engines, and installing variable drive pumps rather than having to turn equipment on and off.”
Added Sames: “In pure economic terms, a fuel cell has higher energy efficiency than a diesel engine. In the future, the fuel is not likely to be hydrogen. Instead it can be a gas or a liquid synthetic fuel. We obviously know how to handle liquid fuels aboard ships. Pressurized gas tanks, however, are difficult to design into a ship environment.”
Solar power may be less attractive, at least for the foreseeable future. “Solar applications can presently produce 150 watts per square meter,” said Sames, “which means you need to cover 67,000 square meters to generate 10 MW. Even if you covered an entire large crude carrier with solar panels, you would only produce 2.5 MW.”
Nuclear power is attractive from a price point of view and ice breakers and submarines have been operating incident free for a long time, he said. One problem is public perception among passengers; another is the fact that few ports allow nuclear-powered ships to dock.
Meanwhile, cruise ships remain fairly boxy in shape. The reason is twofold: The shape allows for more efficient use of the hull and superstructure for passenger spaces, and secondly, there is not much to be gained from making cruise ships more aerodynamic, according to Sames, who said the density of air is one thousand times less than water.
Excerpted from Cruise Industry News Quarterly Magazine: Fall 2008
