|
Environmental Benefits With Diesel Electric Power
September 14 2008
Interest for diesel-electric power within commercial shipping has increased in recent years, and the environmental gains are significant. With Volvo Penta's 16-liter engine, environmentally harmful emissions are just a fraction compared with traditional ship diesels. The traditional ship diesel is connected mechanically to the ship's propeller via a reversing gear and driveshaft. The engine's rpm is the only way to affect the propellers, and therefore, the ship's speed.
Electric-powered propellers
With diesel-electric power, the ship has a number (often four to six) smaller diesel engines that each drive a generator. The electricity produced powers one or two drive units located under the ship's hull. The drive units are "all-in-one units," with electric engine and propeller. And since they are turnable, they also handle the steering. In this respect, speed can be controlled through the electric engines in the drive units and by varying the number of diesel engines in operation. Since the electric engines have a low noise level and it is much easier to noise insulate diesel-electric generators than traditional marine diesels, such vessels as ferries equipped with diesel-electric power operate significantly quieter than comparable vessels with traditional propulsion.
"In applications with major variations in the vessels cargo and speed, diesel-electric operations often delivers better fuel economy as well as significantly lower emissions. These are two areas that are becoming increasingly important for the world's shipping companies and, accordingly, we foresee a strongly increasing demand for diesel-electric alternatives in current procurements," says Gerard Törneman, Product Planning Manager for marine commercial engines at Volvo Penta.
Eliminates sulfur and nitrous oxide
Instead of bunker oil containing sulfur, the engines in a modern diesel-electric system operate with the same type of diesel fuel used in, for example, trucks. Volvo Penta's D16 engines, which are a common alternative for diesel-electric operation, fulfill all environmental standards for commercial traffic, including the European standard for inland waterway transportation. Environmentally harmful sulfur emissions are a fraction compared with a traditional ship diesel and NOx emission are nearly halved compared with just a few years ago.
Number of engines to fit need
Every engine is at its optimum at a certain rpm. Operating at half speed can be uneconomical and result in sharply increased emissions.
With diesel-electric power, one of more engines can be completely shutdown. A ship with six engines can operates on three at full power and travel at half speed, with the best possible fuel economy and lowest possible emissions. For passenger ferries and supply vessels, which operate with varying cargoes and speeds, diesel-electric power offers major environmental advantages – often as much as 15% lower emissions.
Increased cargo capacity
The success for diesel-electric propulsion is not attributable solely to the direct environmental properties. As a result of being able to install the engines in any location, the cargo and passenger space is greater, which creates possibilities for more efficient seaborne transportation.
Safety is also enhanced, since the ship can continue to operate despite one or more engines being shutdown. There is no risk of drifting powerless if one engine breaks down. It is also possible to perform maintenance on the engines without any costly lay-up.
|
