Vegetable Oil: From Kitchens to Power Lines Jim_Kling
PhotoDisc Petroleum-based (mineral) oils are unglamorous, yet vital mainstays of industry. They are used as lubricants and coolants, among other applications. But they are nonrenewable, hazardous, and expensive to clean up spilled. Those drawbacks have industry considering alternatives, including vegetable oils from crops such as rapeseed and soybeans. An article in the March issue of Tribology and Lubrication Technology (1) describes the use of vegetable oils in one important application: electrical transformers, which transform voltage from the high levels, used to transport power over long distances with minimal loss of power, to the lower levels required for local use. Waverly (Iowa) Light and Power and California’s Sacramento Municipal Utility District (SMUD) have committed to using only transformers that use vegetable oils. The decision stems from several incentives. About 40% of existing transformers are contaminated with PCBs, mandating expensive environmental cleanups when spills occur. The U.S. Environmental Protection Agency requires that even PCB-free mineral oil spills be cleaned up. Vegetable oils can be used to retrofit existing transformers because they are fully miscible with mineral oils and perform the same cooling and insulating functions. Vegetable oils are gentler on the cellulose-based paper that insulates the transformer coils. Inevitably, atmospheric water finds its way into transformer oil, and residual acid in the paper catalyzes hydrolysis and degradation of the cellulose. Vegetable oils dampen that process because they have a greater capacity for carrying water than conventional oils. As a result, water tends to be drawn out of the insulating paper and into the surrounding oil, protecting the paper from hydrolysis. Tests performed by Cooper Power Systems, a manufacturer of medium- and high-voltage electrical equipment, showed that vegetable oils increased the lifetime of a similar paper five- to eight-fold. A SMUD-sponsored study suggested that in spite of their initial high cost, transformers using bio-based oils are 10–20% cheaper in the long run than conventional transformers because a typical transformer using the bio-based oil would last 40 years instead of 30. Vegetable oils could also make it possible to use smaller transformers and still handle sufficient current during peak demand times. Acid-catalyzed cellulose hydrolysis is accelerated by the heat produced by the flow of current through the transformer. Using an oil that limits water exposure could allow utilities to ramp up the current, transforming more power without reducing the lifetime of the transformer. Bio-oils are less of a fire hazard than petroleum-based oils. Although individual transformers rarely catch fire, they are so ubiquitous that a fire occurs somewhere just about every day. Mineral oil burns easily and can stoke such fires, but vegetable oil is far less flammable. These latest developments represent something of a revival for vegetable oils. Late 19th-century developers of oil-based transformers considered using vegetable oils, but they oxidized too quickly and had no price advantage over mineral oils. In the 1990s, new processing methods made vegetable oil more resistant to oxidation; and genetic engineering techniques promise to further reduce oxidation by increasing the content of oleic acid, an antioxidant. One soybean variety has an oleic acid content of 80%, as compared with the average of 18%. In an oxidation chamber, the oil lasted 192 hours. Conventional oil lasted just 7. Plant oils are well positioned for a takeover. In the United States, the glut of soybean oil has depressed crop prices. Companies like Cooper Power Systems and the agricultural commodity supplier Cargill hope that transformer life, fire safety, and environmental concerns could extend the demand into larger transformers and transmission lines. As production of vegetable oil increases, it should also gain a price advantage over mineral oil. (1) Fields, S. Powering up with bio-based oils. Tribology & Lubrication Technology 2004, 60(3), 30–35 (not available online). This article first appeared on May 17, 2004. Vegetable Oil: From Kitchens to Power Lines Make Microarrays Work for You Coming to the USA >From Sediment to Cement The Many Phases of Water Farm-fresh Feedstocks Copyright © 2004 American Chemical Society. All Rights Reserved. Terms of Use | Privacy Policy | Feedback | Au sujet de la ACS | Acerca de la ACS [Non-text portions of this message have been removed] ------------------------ Yahoo! Groups Sponsor ---------------------~--> Make a clean sweep of pop-up ads. Yahoo! Companion Toolbar. 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