Con Edison NESCAUM GHG Case Study - NESCAUM — …



Con Edison NESCAUM GHG Case Study

Sulfur Hexafluoride (SF6) Emission Reductions

Due to Con Edison Best Management Practices

Background

Sulfur hexafluoride (SF6) is a man-made gas that became commercially available in 1947. SF6 is the electric power industry’s preferred gas for electrical insulation, arc quenching and current interruption equipment used in the transmission and distribution of electricity. Generally, there are four major types of electrical equipment that use SF6 for insulation and/or interruption purposes: gas-insulated circuit breakers and current-interruption equipment, gas-insulated transmission lines, gas-insulated transformers, and gas-insulated substations.[1] It is estimated that for these applications the electric power industry uses about 80% of the SF6 produced worldwide, with circuit breaker applications accounting for most of this amount.[2]

SF6 is extremely stable and long lasting, with an estimated atmospheric lifetime of 3,200 years. SF6 is also a potent greenhouse gas (GHG). SF6’s 100-year global warming potential (GWP) designated by the Intergovernmental Panel on Climate Change (IPCC) is 23,900.[3] Recently a previously unknown GHG has been discovered (trifluoromethyl sulfur penatfluoride – SF5CF3) and scientists are hypothesizing that it may be a product of the breakdown of SF6 during arc quenching and current interruption. Without costly disposal methods that actually destroy SF6, it expected that all of the SF6 that has ever been or will ever be produced will eventually be emitted to the atmosphere.

SF6 emissions from the electric industry are the result of releases from properly functioning equipment (due to both static and dynamic operation), from leakage (due to old and/or deteriorated gaskets or seals), and when gas is either transferred into equipment or extracted from it for disposal, recycling, or storage. It would be possible but not practical to gauge the rate leakage of the equipment by either installing flow gauges on each piece of equipment or having a scale of some type at each position. In either case, the cost would be prohibitive. If scales were placed at each piece of equipment it would require station personnel to move cylinders to and from the equipment. This practice would/could lead to injuries. The accuracy of the scales would be questionable and the scales would require constant replacement. The addition of flow gauges would also introduce more potential leakage points.

Con Edison was the first electric utility to begin using SF6 instead of oil in circuit breakers as it offers significant savings in land use enabling substations to be installed in populated areas close to loads – a major issue in New York City. Since it began using SF6, Con Edison implemented efforts to reduce and monitor the amount of SF6 released into the environment from SF6-insulated equipment. Last year, Con Edison formalized and also increased its efforts with regards to SF6 management.

Executive Summary

This case study quantifies the emission reductions of SF6 due to Con Edison’s best management practices (BMPs) that are currently being implemented to meet its voluntary reduction commitment under the SF6 Reduction Program for Electric Power Systems to reduce SF6 by 20% from a 1996 baseline of 365,930 lbs (4,372,864 tons of CO2 equivalents) by 2005 (4% per year beginning in 2000).

On April 12, 1999 Consolidated Edison Company of New York, Inc. (Con Edison) entered into a Memorandum of Understanding (MOU) with U.S. EPA regarding the SF6 Emissions Reduction Partnership for Electric Power Systems. This formalized Con Edison’s commitment to responsible SF6 management, set reduction goals and requires the submittal of annual inventories to EPA (among other commitments). Companies that join the partnership agree to inventory its emissions of SF6, establish a strategy for replacing older equipment, implement SF6 recycling, ensure that only knowledgeable personnel handle SF6, and submit annual progress reports. EPA will act as a clearinghouse for technical information on successful strategies to reduce SF6 emissions.

From a 1996 baseline of 4,372,864 tons of CO2 equivalents, Con Edison reduced its use and therefore it emissions of SF6 by 695,371 tons of CO2 equivalents in 1998 and by 1,038,921 tons of CO2 equivalents in 1999. In 1997, Con Edison’s SF6 emissions increased by 445,257 tons of CO2 equivalents. Therefore, Con Edison’s net reduction in SF6 emissions from its 1996 baseline total 1,289,035 tons of CO2 equivalents.

Con Edison has accomplished this through a coordinated planning process that tracks SF6 from “cradle to grave”. Some best management practices that are being implemented include:

• establishing SF6 reclamation centers and the use of “gas carts” (recycling units) that enable Con Edison to recover, purify and reuse SF6;

• inspection and leak detection of all SF6 equipment using a laser imaging system and video;

• periodic internal inspection of SF6 equipment;

• a policy that SF6 is added to breakers only when a low gas alarm is received;

• monitoring and tracking of low gas alarms to prioritize work requests (i.e., sealing leaks or replacing equipment);

• SF6 cylinder weighing procedures to determine the quantity of gas used and that which is returned to the supplier.

Con Edison utilized the best available methodology to quantify emissions and reductions of SF6 as recommended by EPA in its guidance to participants in its SF6 Reduction Partnership for the Electric Power Industry. The method involves tracking the number of pounds of SF6 purchased annually. This method may introduce a degree of uncertainty to the calculation, but at this point it is difficult to assess.

Strategy Summary

This strategy quantifies the emission reductions of SF6 due to Con Edison’s best management practices (BMPs) that are currently being implemented to meet its voluntary reduction commitment under the SF6 Reduction Program for Electric Power Systems to reduce SF6 by 20% from a 1996 baseline by 2005.

Apart from the remote possibility of finding a substitute gas with the same or comparable qualities, the approach Con Edison is implementing is twofold: 1) to minimize SF6 releases and 2) reduce the amount of SF6 used. Con Edison is focusing on developing improved methods to quantify and stop leaks, gradual replacement of older equipment which normally leaks at higher rates, implementation of a sound overall policy of using, handling and tracing SF6, better pumping and storage procedures, and efficient recycling. To reduce the amount of SF6 used by its equipment, Con Edison has sought equipment that is manufactured tighter and more compactly (i.e., considered sealed-for-life electrical apparatus).

One of the larger profile strategies Con Edison is implementing to reduce SF6 use and emissions is the replacement of older circuit breaker equipment with higher leakage rates with new equipment.[4] For instance, although not directly included in the emission reduction estimate in this case study, Con Edison has included a line item in its 2000-2004 capital budget for the replacement of 138kV and 345kV circuit breakers. This line item is valued at $7,500,000 over five years. The highest priority units will be units that require frequent SF6 gas replenishment. Two circuit breakers with high SF6 gas leak rates have been identified and are scheduled to be replaced in the Fall of 2000. All equipment purchased is specified to be in accordance with the latest revision of ANSI standards for design and fabrication. The present standards call for SF6 leak rates of 1.0% per year. Con Edison specifies leak rates of 0.5% per year as part of its SF6 reduction plan.

Source Identification

Location Contact

Various Locations Dan Cunningham

Consolidated Edison Co. of New York, Inc. Consolidated Edison Co. of New York, Inc.

Substation Operations 4 Irving Place, Room 800

New York, New York 10003 New York, New York 10003

Phone: (212) 460-2066

Fax: (212) 387-2142

cunninghamda@

Baseline – Calculation

Subsequent to the guidance provided by EPA under the SF6 Emission Reduction Partnership, Con Edison agreed to select a baseline year to calculate a baseline emissions estimate between 1990 and 1998 for which the most accurate information on SF6 emissions is available. As a result, Con Edison selected 1996 as its SF6 base year. Con Edison estimates that during 1996 its emissions of SF6 were approximately 4,372,864 tons of CO2 equivalents. This estimate was determined from inventory records of the number cylinders purchased.[5] The reliance on inventory records is the most accurate and complete means available to Con Edison for determining its SF6 emissions in 1996.

The baseline was calculated using EPA SF6 Emission Inventory Reporting Protocol (see Appendix A for Reporting Form). The following data is necessary to use the protocol:

• SF6 gas in inventory at the beginning of reporting year;

• SF6 gas in inventory at the end of the reporting year;

• SF6 gas additions to inventory (i.e., purchases); and

• SF6 gas subtractions from inventory (i.e., sales or returns)[6]

Gas in inventory refers to the SF6 gas contained in cylinders (each SF6 cylinder holds 115 pounds of gas), gas carts and other storage containers.[7] In order to determine SF6 emissions the following equation was used:

Quantity of SF6 gas at the beginning of the year – the quantity at the end of the year + gas purchases – sales, returns to suppliers disposed of or recycled = SF6 emissions.

Demonstration of Surplus

Currently GHGs are not controlled at either the state or federal levels. As such, the SF6 emission reductions detailed in this case study meet the surplus criteria. Please note the following details below:

City Requirements

The NY City DEC requires that Con Edison report a leak of over 200 pounds of SF6 in NYC but does not require any specific emission reduction requirements for SF6.

Federal Requirements

On April 12, 1999 Consolidated Edison Company of New York, Inc. (Con Edison) entered into a Memorandum of Understanding (MOU) with U.S. EPA regarding the SF6 Emissions Reduction Partnership for Electric Power Systems. In that MOU, Con Edison agreed to the following voluntary measures: estimate baseline emissions during one of the years between 1990 and 1998; provide the total estimated nameplate capacity of SF6 of its SF6 bearing equipment in service; inventory and report its annual emissions of SF6; maintain records that can be used to verify the accuracy of the data reported (e.g., gas purchases and sale records and gas return to suppliers); develop a company wide policy for the proper handling of SF6 which will include to the degree technically and economically feasible commitments to: recycle and reuse SF6, establish a maintenance program to reduce emissions, institute a replacement strategy for equipment that are major sources and purchase equipment that minimizes or reduces leaks; establish an emission reduction goal; and share information about successful SF6 emission reduction processes and technologies.

1605(b) Reporting

At this time, this case study has not been reported to EIA’s Voluntary Reporting of Greenhouse Gases Program (1605b). Con Edison does plan on including its SF6 emissions in its direct emissions baseline in future GHG inventories that are reported to EIA.

Demonstration of Real

The amount of SF6 purchased by Con Edison has decreased since 1996 due to improved methods to quantify and stop leaks, gradual replacement of older equipment which normally leaks at higher rates, implementation of a sound overall policy of using, handling and tracing SF6, better pumping and storage procedures, and efficient recycling – SF6 emissions by Con Edison decrease as well.

Con Edison maintains records that can be used to verify the accuracy of the data reported (e.g., gas purchases and sale records and gas return to suppliers).

Quantification of Emission Reductions

From Con Edison’s 1996 baseline of 4,372,864 tons of CO2 equivalents, emission reductions from 1997-1999 were calculated using EPA SF6 Emission Inventory Reporting Protocol (see Appendix A for Reporting Form). The following data is necessary to use the protocol:

• SF6 gas in inventory at the beginning of reporting year;

• SF6 gas in inventory at the end of the reporting year;

• SF6 gas additions to inventory (i.e., purchases); and

• SF6 gas subtractions from inventory (i.e., sales or returns)

In order to determine annual SF6 emissions the following equation was used:

Quantity of SF6 gas at the beginning of the year – the quantity at the end of the year + gas purchases – sales, returns to suppliers disposed of or recycled = SF6 emissions.

Annual SF6 usage is assumed to indicate the level of SF6 emissions occurring at Con Edison owned facilities. To calculate emission reductions attributable to Con Edison’s BMPs regarding SF6, the 1996 baseline was compared to subsequent years (1997-2000). Table 1 illustrates the annual purchases, returns to suppliers and emission reductions from 1996 baseline levels.

Table 1: Con Edison SF6 Purchases, Returns, Emissions and Reductions

|Year |Number of |SF6 Returns (lbs) |SF6 Emitted (lbs)|CO2 Equivalent (tons) |Reductions from Baseline |

| |Cylinders | | | |(tons CO2 Equivalent) |

| |Purchased | | | | |

|1997 |3,506 |NA |403,190 |4,818,121 |(445,257) |

|1998 |2,676 |NA |307,740 |3,677,493 |695,371 |

|1999 |2,500 |9,309a |278,991 |3,333,942 |1,038,921 |

|2000 |2,878 |2,276 |330,855 |3,953,717 |419,146 |

|Net Reductions | |1,708,180 |

a. Con Edison begins weighing SF6 cylinders to determine unused portion of SF6 returned to supplier.

Data Integrity and Uncertainty

Currently, the best available methodology to quantify emissions and reductions of SF6 is to track the number of 115-pound SF6 cylinders purchased annually and the amount of gas returned to suppliers. This is the recommended method by EPA in its guidance to participants in its SF6 Reduction Partnership for the Electric Power Industry.

Prior to 1999, Con Edison did not have the cylinder weighing protocol in place. As a result, data from 1996-1998 assumes all of the gas that was contained in the cylinders that were purchased was used and emitted. This is simply not the case. All of the gas does not get extracted from the cylinder when discharged due to loss of pressure in the cylinder – some gas remains in the cylinder and gets returned to the supplier. Con Edison has estimated that historically between 20-40% of the gas remained in a cylinder following discharge. Note that weighing the cylinders increases the ability to gauge the remaining contents of the cylinder, which in turn also increases the total amount of gas that is used by Con Edison (i.e., in 1999 only approximately 3% of the gas remained in the cylinders and was returned to the supplier). In previous years, the unknown quantity of SF6 was sent back to the supplier after the pressure was depleted from the cylinder. This introduces a degree of uncertainty to the quantification of not only emission reductions but the determination of baseline emissions as well.

There is currently little verifiable data for estimating SF6 emissions from electrical transmission and distribution systems. A major driver of the EPA SF6 Reduction Partnership for the Electric Power Industry is to explore reduction strategies and share experiences as well as to develop more accurate methods of measuring emissions and reductions. Until the partnership results in more accurate methodologies such as utilizing an infrared camera to detect leakages and eventually determining the rate of SF6 leakage and expected emission reductions from particular strategies (such as EPA’s Natural Gas Star Program), this method serves as the most accurate available. Therefore, Con Edison believes there is a medium degree of confidence with the methods and results quantified in this case study.

Emission Reductions

From a 1996 baseline of 4,372,864 tons of CO2 equivalents, Con Edison reduced its use and therefore it emissions of SF6 by 695,371 tons of CO2 equivalents in 1998 and by 1,038,921 tons of CO2 equivalents in 1999. In 1997, Con Edison’s SF6 emissions increased by 445,257 tons of CO2 equivalents. Therefore, Con Edison’s net reduction in SF6 emissions from its 1996 baseline total 1,289,035 tons of CO2 equivalents.

Ownership

Con Edison has invested the monetary and manpower resources in the management of its SF6 usage, therefore it owns the right to any emission reductions that result from its activities with regards to the management of SF6 in its electricity transmission and distribution operations. To Con Edison’s knowledge no other entity can report on these activities or claim ownership of SF6 emission reductions on the Con Edison system.

Other Environmental Impacts

A reduction in SF6 use may also directly lead to a reduction in the formation of a previously unknown GHG– SF5CF3. Scientists are hypothesizing that SF5CF3 may be a product of the breakdown of SF6 during arc quenching and current interruption. Scientists estimate that SF5CF3 has a GWP of 18,000.

In addition, a reduction in SF6 use reduces the need to manufacture the product and therefore reduces energy and the associated fuel use required to produce SF6. Unfortunately, SF6 manufacturing energy use data is not available to Con Edison for inclusion in this case study.

Registration Statement

As a representative of Con Edison presenting this case study, I have personally examined the case study and believe it to be true and accurately represent the activities of Con Edison.

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[1] L.G. Christophorou, et al, Gases for Electrical Insulation and Arc Interruption: Possible Present and Future Alternatives to Pure SF6, National Institute of Standards and Technology Technical Note 1425, November 1997.

[2] Besides the use of SF6 by the electric industry, other uses of SF6 include: semiconductor processing, blanket gas for magnesium casting, reactive gas in aluminum recycling to reduce porosity, thermal and sound insulation, airplane tires, spare tires, “air sole” shoes, scuba diving voice communication, leak checking, atmospheric tracer gas studies, ball inflation, torpedo propeller quieting, wind supersonic channels, and high voltage insulation for many other purposes, such as AWACS radar domes and X-ray machines.

[3] This GWP means that 1 pound of SF6 reduced is equal to reducing approximately 12 tons of CO2.

[4] Older two-pressure circuit breakers can contain up to 2,000 pounds of SF6, while more modern breakers contain less than 100 pounds of SF6.

[5] Each cylinder contains 115 pounds of SF6 gas. From 1960 to 1994 the price of SF6 in quantity purchases remained basically constant at about $3.00 per pound. The current price of SF6 for quantity purchases in the U.S. varies from as low as $12 per lb to over $37 per pound.

[6] Prior to 1999, SF6 gas from cylinders was emptied into circuit breakers until the pressure in the cylinder was gone. As a result, Con Edison had no way of quantifying the quantity of SF6 remaining in the cylinder and subsequently returned to the supplier. Based on Con Edison’s calculations, it is assumed that historically between 20 – 40% of the gas remained in the cylinder and is ultimately returned to the supplier (23 – 46 lbs per cylinder). In 1999, Con Edison began weighing the cylinders before and after dispensing to gauge the quantity of gas remaining and returned to the supplier.

[7] A gas cart is a temporary storage device that is typically used to extract gas from or put gas into a piece of equipment which is having maintenance performed on it rather than venting that gas to the atmosphere.

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