Thursday, February 4, 2010

Green Vessel Design—environmental best practices

Excerpt from U.S. Coast Guard “Proceedings of the Marine Safety & Security Council” magazine, by Mr. Brian W. King, P.E.; Mr. Joseph Payne, P.E., LEED-AP; Mr. Ryan Roberts, P.E.; Ms. Christina Villiott, CPSM; all of Elliott Bay Design Group.

As naval architects and marine engineers, we have the opportunity to improve upon design practices and benefit the environment.

Minimize Use of Hazardous Materials and Environmental Contaminates
There are a number of programs that address the use and minimization of hazardous materials and containment. Per “Green Passport,” an International Maritime Organization program, vessel owners are required to maintain accurate records of the potentially hazardous materials that went into the construction of their ships. IMO also addresses issues associated with ship and equipment recycling.

Heating, ventilation, and air conditioning equipment offers an excellent area for improving a ship’s environmental performance. Newer systems are available with a low refrigerant charge per ton of cooling capacity, as well as low global warming potential and ozone-depleting potential.
Minimizing use of volatile organic compounds (VOCs) is another key factor. During ship construction and throughout a ship’s life, use of low-VOC products can improve the air quality of the surrounding community, as well as that of the future occupants of the vessel.

Maximize Use of Recycled and Recyclable Material
The environmental impact of a ship occurs in three distinct stages of its life: construction, operation, and disposal. Green considerations can be applied during vessel design, which will translate to improvements in the construction and operation of a vessel throughout its lifecycle, and provide for greener recycling at the end of the ship’s lifespan.

Steel and aluminum are readily recyclable materials, but improvement in recycling is necessary for many other materials throughout the ship. A key consideration is the design and installation of systems that prevent non-recyclable and/or hazardous materials from contaminating recyclable material.

Minimize Waste and Scrap
Much of the waste generated during construction can be reduced with careful production planning, weight control, and greater reliance upon detailed design and computer lofting of structure and piping systems.

To accomplish this analytic approach, state-of-the-art tools such as finite element analysis and computational fluid dynamics are used. At the pre-production and production stages of design, computer lofting is extensively used to plan for almost all of the structure of the ship, and increasingly in piping and wireways.

Maximize Use of Rapidly Renewable and Regional Materials
Rapidly renewable materials such as bamboo, linoleum, cork, poplar, and wool are generally accepted as having a natural replacement cycle of less than 10 years, so their use places less of a burden on our environment. Additionally, utilizing regional materials can reduce the energy required for their transport.

Minimize Air Emissions
Diesel engines that power a majority of the world’s fleet are responsible for carbon dioxide, sulfuric and nitrous oxides, smoke and particulate emissions, noise, and sensible heat leaving the stack. Positive change toward minimizing air emissions can lead to substantial environmental improvement. Areas for emission-minimizing opportunities include hull form optimization, speed considerations, diesel choices, and use of alternative fuels.

Minimize Energy Use
An often-overlooked aspect of the design is the location and placement of the appendages, such as the rudder, bilge keels, keel coolers, etc. If not aligned to the water flow over the hull, they can increase the drag by a surprising amount.

Increased hull and compartment insulation is another significant energy saver. HVAC requirements are typically the single-largest electrical load on ships. With the current high costs of fuel, the payback for better insulation can be measured in months. To maintain interior air quality, 20 percent or more of conditioned ventilation air is typically exchanged with fresh air from the outside. While this improves interior air quality, it also represents lost energy used to heat or cool the air. Much of this energy can be regained by installing fresh air heat exchangers, which heat or cool the incoming fresh air using the waste conditioned air it is replacing.

Much energy from fuel is lost as heat through the engine exhaust or for engine cooling. The ship designer can recover some of this lost energy by utilizing jacket water heat recovery to produce fresh water or for accommodation heating.

Photo: The harbor tug "ship docking module" design that is being adapted for hybrid drive. Photo courtesy of Elliott Bay Design Group.

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