In 2012, the World Health Organization (WHO, Geneva, Switzerland) estimated that there are more than 1 billion people who lack fresh water. By midcentury that number was expected to swell to 4 billion. That bad news is good news for composites: Almost 60 percent of the world’s population lives less than 36 miles/60 km from a seacoast. Seawater desalination, therefore, is poised to become one of the main alternative freshwater resources in those regions. In fact, the market for products and services used to convert seawater into potable water was estimated to be about $2 billion (USD) in 2000. Market research firm The Freedonia Group (Cleveland, Ohio) predicts that the desalination market will expand to more than $18 billion by 2020.
Filament wound glass/polyester composites have quietly found application in several stages of the most-used seawater reverse osmosis (SWRO) desalination technique (read more about composites in seawater desalination in “Composites slake the worlds thirst,” under Editor’s Picks,” at top right). SWRO plants around the world use many miles of corrosion-resistant fiberglass-reinforced polymer (FRP) low-pressure piping as a distribution network, primarily over land, to carry seawater from to the plant, to distribute the potable water that is produced, to carry the brine (salt and impurities) back to the ocean, and for internal plant treatment piping and energy recovery devices. For aboveground applications, says Peter Kirkwood, managing director for ResiGlass Pty. Ltd. (Winthrop, W. Australia), helical filament winding on a fixed-length mandrel is most popular because it can be tailored to achieve the desired hoop-to-axial strength ratio by customizing wind angles, making it ideal for restrained joining, which features couplings, tie rods or other types of restraints. For underground pipes, continuous filament-wound pipe is generally used because it can be produced in a greater variety of lengths and diameters. Fiber-reinforced plastic also forms storage tanks and piping used in desalination plants to contain sodium hypochlorite (NaOCl) used in chlorination of desalination process water, and for sulfuric acid — very difficult to store in metal but readily handled in fiberglass/epoxy vinyl ester tanks and piping at ambient temperatures and concentrations below 50 percent, says Thomas Johnson, corrosion industry manager for resin producer Ashland Performance Materials (Dublin, Ohio).
Most importantly, the pressure vessels that encase reverse osmosis (RO) membranes are predominately filament wound FRP. Multiple RO elements can be encased within each pressure vessel, and the vessels are grouped together to use common pipes for feed water, fresh water and brine. Each grouping is called a train, and the trains are arranged in racks (see photo at left).
Doug Eisberg, director of business development for RO membrane service company Avista Technologies (San Marcos, Calif.) points out that filament winding on a precision mandrel produces a consistent inside diameter (ID) with a smooth surface. By comparison, a comparable metal pipe has neither — a critical factor when installers must ensure a tight fit on the end closures that seal the joint where the membrane and pressure vessel meet. In 2013, desal plants — once found only in oil-rich, but desert-dominated climes in the Middle East, continue to spread around the globe, with projects built, under construction and/or or planned along the coasts of Spain, Israel, Australia, Singapore, Algeria, and the U.S.
Meanwhile, electric utilities, particularly those in weather-beaten and/or hard-to-access locations are still overcoming their cautious approach to take advantage of fiberglass for power transmission towers, distribution poles and cross-arms, as well as the aluminum conductor cables they support.
Composite-reinforced aluminum conductor (CRAC) cables, conductors in which the traditional steel strength members are replaced with a pultruded continuous-fiber core, are designed by developers to reduce increase power-transmission efficiency by 200 percent, reduce cable weight and mitigate the phenomenon of thermal sag (heat-related elongation of steel conductor cores) that is often the culprit in power outages. Because CRAC cabling weighs less than steel-cored cable, it was, for more than a decade, expected to be an attractive alternative for upgrading power lines. An increased number of cables can be hung from each existing tower, increasing power transmission capability without the huge expense of erecting new towers or obtaining additional rights of way. Progress, however, had been slow. But in the 2012-2013 time frame, these high-temperature, low-sag (HTLS) composite-cored conductors finally took some leaps. Two U.S. companies have developed HTLS conductors for this $1 billion-plus business — a subset of the overall electricity transmission market valued at about $50 billion — using load-bearing composite cores with substantially lower CTEs than traditional ACSRs. By September 2012, CTC Global (Irvine, Calif.) had installed more than 9,200 miles/14,806 km of its hybrid carbon/glass fiber Aluminum Composite Core Conductors (ACCCs) in more than 220 projects worldwide. CTC has multiple qualified suppliers for composite materials, but typically it uses carbon fibers from Toray Carbon Fibers America (Flower Mound, Texas) and boron-free E-glass fibers from Owens Corning (Toledo, Ohio), with a proprietary epoxy resin system. Bryant says 1 ft/305 mm of a 0.375-inch/9.5-mm diameter core uses about 0.10 lb/0.45 kg of fiberglass, carbon and resin. CTC’s 9,200 miles of cable required about 4,857,600 lb (2,203,368 kg) of composite material.
3M Electrical Markets Division (Austin, Texas) has also seen widespread acceptance of its HTLS conductors. 3M’s Aluminum Conductor Composite Reinforced (ACCR) cabes are made using a metal matrix. By February 2013, 3M had about 1,600 miles/2,575 km of conductors in some 13 countries, covering all continents except Australia and Antarctica. In the U.S. project, Georgia Power, (Atlanta, Ga.), estimates more than $15 million were saved by using ACCR to upgrade 34 miles of 230kV power transmission line serving Savannah, Ga. 3M is doubling its manufacturing capacity at its plant in Menomonie, Wis., in response to demand.