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Tomorrow's T&D

The most economical energy savings might be found in grid efficiency.

Fortnightly Magazine - February 2010

the significant contributors of distribution losses are the no-load transformer core losses. To address this situation, the U.S. Department of Energy (DOE) issued a ruling on minimum efficiency for distribution transformers, which became effective Jan. 1, 2010. Before finalizing the ruling, DOE conducted an extensive analysis of tradeoffs between energy savings versus transformer costs, with all available (but practical) material options, including amorphous metal.

DOE estimates the standards will save approximately 2.74 quads [quadrillion British thermal units (Btu)] of energy over 29 years (2010 through 2038). This is equivalent to all energy consumed by 27 million American households in a single year.

Amorphous metal transformers (AMT) were developed in the United States under an EPRI program in early 1980 with General Electric (GE). Amorphous metals are a new class of material with a random atomic structure unlike regular metals, which are crystalline. Transformers built with these materials have about one-third of the core losses when compared to regular silicon-iron based core transformers, resulting in highly energy-efficient units. AMTs are slightly more expensive but have significantly lower operating costs than conventional units do, resulting in lower life-cycle (LC) or total ownership costs (TOC). During the next 15 years, more than 500,000 units were installed in the United States with a very satisfactory field experience. In the late 1990s, the demand for this product disappeared as restructuring ( i.e., deregulation) set in, resulting in all manufacturers abandoning the production of these types of units in the United States. However, the product has been very popular in India, China, Japan (in descending order of installations) and other countries.

As a result of the DOE ruling, there’s a renewed interest in the United States for AMTs. They’re a solution for U.S. utilities working to improve distribution system efficiencies, reduce their carbon footprints, and meet or exceed other environmental goals. This technology might be marginally cost effective at today’s fuel price without monetizing carbon. However, future scenarios that might include higher fuel costs and a carbon price would increase the effectiveness of this technology.

By 2038, DOE expects the energy savings from the standards to eliminate six 400-MW power plants (2,400 MW) and 238 million tons of carbon dioxide (CO 2). Using a 3-percent discount rate, the cost of the standards is $460 million a year in increased equipment and installation costs, while annualized benefits are $904 million a year in reduced operating costs.

However, had AMT been the standard, energy savings would have been 7.37 quads, a CO 2 reduction of 674 million tons, and generation elimination of 7,200 MW—triple the benefit compared to the current ruling.

Optimizing voltage also will yield substantial energy savings. Losses and end-use consumption are reduced when the voltage along the feeder is managed to be within the lower end of the standard supply service voltage band. This practice is called voltage optimization, or conservation voltage regulation (CVR). For many years, utilities have used voltage regulation to reduce demand during periods of peak consumption. While not a new concept, the practice of voltage regulation is now seeing renewed interest from