Independent Study Shows Small NYPA Plants are City's Cleanest Power Sources

Peter Barden

November 6, 2003


NEW YORK—An independent review by a nationally recognized environmental consulting firm has found that the New York Power Authority’s (NYPA) six small power plants in New York City are the cleanest power sources in the city and that the units’ pending air-quality permits will be among the strictest in the nation for similar facilities.

“The analysis of mass emissions data from the NYPA small power plants (SPPs) compared to other operating facilities in the city indicates that the NYPA SPPs are the lowest emitters in the city for carbon monoxide, nitrogen oxides (NOx), carbon dioxide, sulfur dioxide, particulate matter and volatile organic compounds,” the report by M.J. Bradley & Associates of Concord, Mass., said.

Based on an extensive review, the firm said it was aware of only three other similar plants in the nation—two in California and one in Massachusetts—that operated under strict emissions limits comparable to those for the NYPA gas-turbine plants, which were installed in 2001 in time to help avert a projected power shortage that summer.

In addition, the Bradley analysis indicated that the NYPA plants reduce the need to run “higher-emitting” generation in New York City at times other than the highest-demand days, when all power plants presumably would be needed.

“If the NYPA SPPs were not operating, it is likely that emissions would be higher due to the need to seek power from higher-emitting plants,” the report said.

The 44-page report, supplemented by 50 tables and charts, was commissioned by NYPA and Communities United for Responsible Energy in cooperation with the Natural Resources Defense Council.  The consultant examined operations and emissions data from the last quarter of 2001 through the first quarter of 2003 for NYPA’s small natural-gas-fueled plants at Hellgate and Harlem River Yards in the Bronx, North First Street and Grand Avenue and 23rd Street and Third Avenue in Brooklyn, Vernon Boulevard in Queens and Pouch Terminal in Staten Island, as well as at Brentwood in Suffolk County.

The Bradley study determined that the small plants, at which NYPA invested a total of about $85 million in the most advanced available environmental controls, “consistently meet permitted emission limits during steady-state operating conditions, with only occasional exceedances occurring as a result of malfunctions.”

The study also noted that, as previously reported by NYPA, the strict emissions limits in the original air-quality permits issued by the state Department of Environmental Conservation were often exceeded during the review period at times when the generators were starting up or shutting down. 

Although the sophisticated emissions controls do not operate at maximum efficiency at such times, this was not reflected in the original permits because of a lack of operating experience with similar equipment at gas turbines anywhere in the nation.  The pending permits, now under review, include more realistic limits for startups and shutdowns while retaining the current standards for steady-state, or normal, operation.

The Bradley report found that all applicable air-quality standards and guidelines will be met “by a wide margin” under the new permits and that the small plants will have “the strictest NOx limitations, including those proposed for startup and shutdown periods, of  any similar facility ever permitted in New York State.” 

In addition, the consultant said it appeared that NYPA had accurately reported the frequency, duration, magnitude and cause of emission limit exceedances.

To analyze the environmental benefits of running the NYPA plants instead of others in the city, the study compared the operational patterns and the emissions of NOx—a major source of smog—for the small plants and several other facilities.

This analysis, carried out for two-week periods of high demand in the summer and winter of 2002, showed that the NYPA plants displaced output from the others on all but the highest-use days.  If extended over an entire year, the report said, the summer operational and emissions patterns would cut NOx emissions in the city by between 719 and 9,246 tons, depending on which units were displaced.  Though less, the annual reduction based on the winter displacement would be at least 288 tons.

The consultant said it expects the NYPA plants to continue operating at current levels because new plants planned or under construction in the New York City area “will only serve to meet the projected increase in demand.”  In addition, the report cited the absence of short-term transmission projects to ease current limitations on importing power to the city from outside the area.  The assessments were based on information from  the New York Independent System Operator, which runs the state’s power network.

The report noted that the NYPA plants in the city are used not only to meet peak demand for electricity, but also to serve “load pockets" that are often unable to obtain power from outside sources.

(For a copy of the complete report, please contact Peter Barden at 518-433-6734.)