Eric Jay Dolin, PhD,
EPA Program Manager
Since April 1998, the U.S. Environmental Protection Agency (EPA) has worked with the utility industry to voluntarily reduce emissions of sulfur hexafluoride (SF6), which is used as an insulating medium in electric equipment. As of Aug. 1, 2000, the SF6 Emissions Reduction Partnership for Electric Power Systems had 60 partners representing roughly 35 percent of U.S. net generating capacity. Each utility partner voluntarily committed to take economically and technically feasible actions to reduce emissions. Judging by the first year’s annual reports, submitted this past spring, the partnership is off to an excellent start. While, cumulatively, the partners reported significant emissions, it is also clear that through their actions such emissions will decrease over time. This is good for the environment and the bottom line.
SF6 is an extremely potent greenhouse gas, with a global warming potential of 23,900, over a 100-year time horizon. This means that on a per-unit basis, and over a 100-year period, SF6 is 23,900 times more effective at trapping infrared radiation than an equivalent amount of CO2. SF6 is also very persistent, with an atmospheric lifetime of 3,200 years.
The electric power industry uses a significant percentage of the SF6 produced worldwide annually. Ideally, none of this gas would be emitted to the atmosphere, either directly from operating SF6 equipment or as a result of losses due to maintenance and/or recycling activities. In practice, however, there are emissions from these sources. Utilities face not only environmental, but also economic incentives to reduce emissions since SF6 is a relatively expensive gas.
To join the partnership a utility must sign a Memorandum of Understanding (MOU), which details the responsibilities of EPA and the partner. EPA agrees to act as a clearinghouse for technical information on successful strategies for reducing SF6 emissions; provide partners with recognition for their achievements in reducing SF6 emissions; serve as a credible repository for data on the emissions reduction achievements of the partners; and work to obtain commitments from all electric power system operators to join the partnership. The MOU requires partners to do the following: inventory leaks of SF6 annually, using an EPA worksheet; ensure that only knowledgeable people handle SF6; establish a strategy for retiring older, leakier pieces of equipment; implement SF6 recycling; submit annual progress reports; and, 18 months after joining, establish an emissions reduction goal for the utility.
Partners range from very large utilities to very small. The following statistics are based on cumulative data across the partnership for the year 1999. There were roughly 530,000 pounds of SF6 emitted by the partners during that year. The mean annual emissions of SF6 from individual partners were roughly 13,000 pounds. The mean leakage rate was 10 percent (leakage rate is determined by dividing annual emissions by the total number of pounds of SF6 in the partner’s operating equipment). It is important to reiterate that these are mean values. Actual numbers for individual partners vary widely.
These numbers support EPA’s original assumption that many utilities have the potential to reduce their emissions of SF6 over time, especially when one considers that modern SF6 circuit-breakers are often guaranteed by the manufacturers to leak at 1 percent per year or less. The partners are all engaged in efforts to either maintain their low emissions rates or to reduce emissions over time. They are accomplishing this in many ways. Some have invested in recycling carts and SF6 management training. Others are replacing older, leakier circuit breakers with newer, tighter ones. Still others are using leak detection methods (e.g., laser systems and halogen sniffers) to detect where leaks are so that remedial action can be taken. Many are using all of these options to ensure that emissions are minimized. In the coming months, the partners will submit their long-term emissions reduction goals and EPA is confident that such goals will help set the partners on a course for further success.
EPA is sponsoring an international conference, SF6 and The Environment: Emission Reduction Strategies, on Nov. 2 & 3, 2000, in San Diego. There will be plenary sessions covering global climate change science, international greenhouse gas negotiations, international perspectives on SF6 management, and worldwide SF6 production and sales. The utility track will cover issues such as gas handling and management, recycling, gas mixtures, and case studies of successful programs. Three hundred to four hundred participants are expected, from the United States and around the world.
For more information on the conference and the partnership, visit www.epa.gov, or contact Program Manager, Eric Jay Dolin, at 202-564-9044 (email@example.com).