NYC Heads to Hottest July Ever, Taxing Power Grid (Correct)

(Corrects consumption to conservation in 15th paragraph.)

If it feels hotter than it’s ever been in New York, that’s because it is.

New York’s Central Park is heading toward its warmest July on record after two heat waves this month, the National Weather Service reported. Extreme heat pushes aging power systems to their limits, increasing the odds of breakdown, according to grid monitors.

“The grid system was built a long time ago, and the population has increased dramatically across this part of the country, and energy demand has gone up accordingly,” said Jim Rouiller, a senior energy meteorologist at Planalytics Inc. in Berwyn, Pennsylvania. “July may not be the top, but it is going to be in the top five, and this is over 130 years worth of observation, so it is outstanding heat.”

In August 2003, bad equipment and operator error at an Ohio power plant triggered an outage that left about 50 million people in eight U.S. states and Ontario without electricity for as long as four days, according to a U.S.-Canada Power System Outage Task Force report issued in 2004.

“Weather was not the root cause, but it was a contributing factor,” said Jay Apt, executive director of Carnegie Mellon University’s Electricity Industry Center in Pittsburg. “On days of high demand, the system is closer to the edge than it is on days of low demand.”

Monthly Average

The average monthly temperature in Central Park has been 81.6 degrees Fahrenheit (27.6 Celsius) so far, warmer than the record set in July 1999 of 81.4, said Matt Scalora, a weather service meteorologist in Upton, New York.

The higher-than-normal temperatures have driven up electric power use around the U.S., including in New York, which recorded its third-highest hourly peak load of 33,542 megawatts on July 6 when temperatures reached a record 103 degrees in Central Park.

The highest hourly peak load was 33,939 recorded on Aug. 2, 2006, according to a statement by New York Independent System Operator in Rensselaer, New York, a not-for-profit corporation responsible for operating the state’s bulk electricity grid.

Just before the 2003 outage, peak demand in New York was 28,634 megawatts, said Kenneth Klapp, a spokesman for the ISO. The failure knocked 22,934 megawatts offline and left 5,700 still going to customers. Load levels for New York’s ISO had actually gone down in 2003 from a year before, according to the company’s annual report.

In 2003, New York had about 35,800 megawatts of installed capacity, Klapp said. For 2010, it has 38,970, according to an ISO statement. More than 7,823 megawatts of capacity has been added since 1999, Klapp said.

Pushing Limits

The system generally works, said Apt, who is also professor of technology at Mellon’s Tepper School of Business and its school of Engineering and Public Policy.

“The chances of it not working are very small, and even on a hot day they are very, very small,” he said. “But they are slightly higher on a hot day with lots of demand than they would be on an April day where it is nice and cool with the windows open.”

A heat advisory was issued for New York City today, where the temperature in Central Park was 90 at 3 p.m. after three straight days above 90, according to the weather service. The definition of a heat wave is three consecutive days with temperatures of 90 degrees or higher.

“We have been well above normal for the month,” said David Wally, also a meteorologist in the Upton office. “We will have above-normal temperatures through the week.”

Conservation Urged

High temperatures prompted Consolidated Edison Inc., New York’s power utility, to ask customers to curb electricity use, and the Suffolk County Water Authority, the largest on Long Island with 1.2 million users, to ask for water conservation.

The water authority set a record for usage of 500,000 gallons per minute when temperatures reached into the 100s two weeks ago, said Chairman James Gaughran.

“Which is huge,” Gaughran said. “There seems to be a psychology to water your lawn more when it gets hot outside.”

The above-normal temperatures have been driving coal and natural gas consumption as electric demand jumps when people turn on fans and air conditioners.

Nationally, about 46 percent of electricity is generated using coal and 23 percent using natural gas, Energy Department figures show.

Earlier this month, a heat wave gripped New York and the rest of the U.S. Northeast, driving temperatures into the 100s for several days and setting daily records across the region. The Central Park readings came within 3 degrees of the city’s highest temperature on record, 106 on July 9, 1936, according to the weather service.

Global Highs

Around the world, above-average temperatures have been recorded in Europe and Asia as the Jet Stream, which divides and mixes warm and cool air, modulating temperatures, has stayed at far northern latitudes, Rouiller said.

This has allowed warm air to push farther north and has prevented much in the way of relief for the Northern Hemisphere, he said.

The world last month posted its warmest June on record and its warmest average temperatures for April to June and January to June, according to the National Oceanic and Atmospheric Administration. Global temperatures in June were 61.1 degrees, or 1.22 degrees higher than the 20th century average of 59.9, according to a NOAA statement.

Since June 1, the cooling degree days value in Central Park has been 602, or 178 above normal, according to the weather service.

Degree-Days

Cooling degree days, calculated by subtracting a base of 65 degrees from the average daily temperature, is a value designed to show energy demand, according to the weather service. The higher the value, the warmer the weather, and thus the more energy is probably consumed to cool homes and businesses.

In Philadelphia, the value since June 1 has been 708 or 253 above normal. In Atlanta cooling degree-days totaled 787 or 165 above normal and in Houston they were 948 or 137 above normal.

A high temperature of 92 degrees is forecast for Washington, Baltimore and Philadelphia today and 91 in Boston, according to the weather service.

Elsewhere in the U.S., an excessive heat warning continues to be in effect in Oklahoma, Arkansas, Kansas and Missouri, where temperatures will reach into the high 90s and feel as though they are actually closer to 110 degrees or more, according to the weather service.

In some locations, temperatures, when combined with humidity, will feel as hot as 115 degrees, according to the weather service. An excessive heat warning is issued when forecasters expect several days of high temperatures and humidity.

To contact the reporter on this story: Brian K. Sullivan in Boston at bsullivan10@bloomberg.net.

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