Rising Temperatures Expose Cities' Vulnerable Electrical Supplies

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A report (Climate Change and Infrastructure, Urban Systems, and Vulnerabilities) from Oak Ridge National Laboratory (ORNL) released last week highlights the many ways infrastructure critical to American cities is vulnerable to weather extremes -- with some vulnerabilities well beyond city limits (see Federal Report Warns of Costly Impacts to U.S. Cities from Changing Weather Extremes, WWF Climate Blog, 22 May 2012). That infrastructure includes the electrical supply, transmission and distribution systems. Extreme summer heat drives up electricity demand for cooling; and can strain the systems and increase the risks of very costly and disruptive blackouts.

The analysis cites two examples in Arizona in 2011 that illustrate the vulnerability of the electrical system under very hot conditions. The first relates to the threat posed to transmission lines by the Wallow Fire in June 2011. The fire was the largest in Arizona history and endangered the lines carrying power from the Springerville Generating Station, a 1,560 MWe coal-fired power plant in Springerville, Arizona:

"[T]he Springerville Generating Station ... provides critical power into the Tucson Electric Power Company, the Salt River Project, and Tri State Generation and Transmission. As part of emergency response, the cascading impacts of the station’s loss were modeled as the [wildfire] event unfolded. Consequence and forecast models tracked the wildfire threat and estimated the effects on the Arizona power grid if this generating station were to be taken off line. Analysis indicated that there was enough power supply reserve in the grid to avoid a blackout in Tucson, but the modeled case illustrated one kind of vulnerability of an infrastructure to a weather-related extreme event that could cascade in a similar manner."

Above: Wallow fire, 1 June 2011. Source: Brent Watcher IMET National Weather Service/US Forest Service. Posted by Sitgreaves National Forests

Arizona-Southern California Power Outages of September 2011

A second example cited by the ORNL report went well beyond models. It was a blackout that was triggered on 8 September 2011 by the loss near Yuma, Arizona, of a major transmission line that carries electricity from Arizona, through the service territory of the Imperial Irrigation District (IID) of southern California, to the San Diego area. It took only 11 minutes after the line was tripped before there was a complete blackout in San Diego.

The findings of a detailed investigation by the Federal Energy Regulatory Commission (FERC) and the National American Electric Reliability Corporation (NERC) were published last month (April 2012) in Arizona-Southern California Outages on September 8, 2011: Causes and Recommendations. The report attributes the outage to a range of factors, and notes the high temperatures in both states at the time, with "heavy power imports into Southern California from Arizona."

The day (8 September 2011) the transmission line failed around 3:30 pm was the hottest day that month for Yuma -- 113oF. The FERC/NERC report said electricity demand in the territory of the Imperial Irrigation District, a utility serving a large area east of San Diego, was "headed toward near-peak levels." In San Diego it was "a hot day during hours of peak demand," the third day of a heatwave with temperatures on 6 September reaching 97oF -- a record for the date and the hottest day of 2011 for the city.

The FERC/NERC report said:

"The outages affected parts of Arizona, Southern California, and Baja California, Mexico. All of the San Diego area lost power, with nearly one-and-a-half million customers losing power, some for up to 12 hours. The disturbance occurred near rush hour, on a business day, snarling traffic for hours. Schools and businesses closed, some flights and public transportation were disrupted, water and sewage pumping stations lost power, and beaches were closed due to sewage spills. Millions went without air conditioning on a hot day."

It was the biggest blackout in California history. A study by the National University System Institute for Policy Research provides a preliminary estimate that the costs of the power outage in the greater San Diego area may have been on the order of $100 million (see Preliminary Report on the San Diego Blackout Economic Impact, press release, 9 September 2011).

The Northeast Blackout

The following, excerpted from ORNL's Climate Change and Infrastructure, Urban Systems, and Vulnerabilities, discusses some of the impacts of the Northeast blackout of August 2003 (started on 14 August), another event associated with hot weather.

"Many issues observed in the San Diego outage of 2011 were also apparent in the August 2003 Northeast blackout. During this blackout, 50 million people in the Northeastern and Midwestern US and Ontario, Canada, lost electric power, but some of the most damaging effects came when water treatment plants and pumping stations were shut down, just as in San Diego. Areas throughout the region lost water pressure causing potential contamination of city water supplies. In Cleveland and Detroit, the water supply was severely diminished and contaminated because of inadequate emergency and back up power generators. Cleveland, Ohio; Kingston, Ontario and New York experienced major sewage spills into waterways. Cleveland, Ohio and Detroit, Michigan issued boil water orders affecting approximately 8 million people.

While some Northeast waste treatment plants overcame the loss of electricity and stayed in operation during the extended power outage, other areas were not as fortunate, as where power was lost at every water pumping station and treatment plant. Within hours of the blackout, water pressure in Cleveland had diminished and over one million customers were left without access to water. At the downtown pumping station, which is below sea level, water pressure remained for some time. However, treatment plants were still in the process of switching over to backup power, and they could not treat the water supply that was available. Three major wastewater treatment plants in Cleveland discharged millions of gallons of sewage into the Cuyahoga River and Lake Erie, polluting the beaches and causing serious environmental damage. While New York’s gravity-fed drinking water system fared well, the wastewater treatment system spilled nearly half a billion gallons of untreated effluent into New York Harbor over two days because pumps were offline.

While many cities believe they have adequate backup power in the case that one or two of the treatment plants and/or pumping stations are down by pulling power from separated substation and not investing in on-site power, they are unprepared for large-scale blackouts that cut off the whole city’s power supply. Adapting to these more frequent events for treatment plants and pumping stations could include either powerful backup generators or on-site power generation with no reliance on the local electric grid. To be successful in a large-scale blackout, the generators must be capable of running entire stations, at least at partial load. In Cleveland and Detroit, most pumping stations did not have enough power to operate their pumps, and treatment plants took up to 15 hours to fully restore their power."

For additional information, see: Report on the August 14, 2003 Blackout in the United States and Canada: Causes and Recommendations [PDF] (April 2004, by the U.S.-Canada Power System Outage Task Force Final.

The Potentially Massive Economic Consequences of Blackouts

Power Blackout Risks: Risk Management Options (November 2011), a position paper by the CRO Emerging Risk Initiative (supported by Allianz SE and 8 other re-insurance companies), warns of the economic impacts of blackouts. It cites estimates that the Northeast blackout of 2003 resulted in losses of $4.5-8.2 billion in the U.S. alone (not including Canada's losses). The initiative emphasized:

"Electricity is the backbone of each industrialised society and economy. Modern countries are not used to having even short power blackouts. The increased dependency on continuous power supply related to electronics, industrial production, and daily life makes todays’ society much more vulnerable concerning power supply interruptions. A brownout (reduced voltage) of some minutes or a similar blackout (complete failure of electricity supply) may cause some inconvenience at home such as having the lights turn off. But a blackout of a few hours or even several days would have a significant impact on our daily life and the entire economy. Critical infrastructure such as communication and transport would be hampered, the heating and water supply would stop and production processes and trading would cease. Emergency services like fire, police or ambulance could not be called due the breakdown of the telecommunication systems. Hospitals would only be able to work as long as the emergency power supply is supplied with fuel. Financial trading, cash machines and supermarkets would in turn have to close down, which would ultimately cause a catastrophic scenario."

More Frequent and Severe Heatwaves Will Increase the Risk of Power Outages

"Heat waves have become longer and more extreme," says the National Academy of Sciences in Advancing the Science of Climate Change: America’s Climate Choices (2010), adding that "it is very likely" that "heat waves will become more intense, more frequent" in the future.

"The likely increase in heat waves implies more peak load demands, stresses on the energy distribution systems and more frequent brownout and blackouts," says the ORNL in Climate Change and Infrastructure, Urban Systems, and Vulnerabilities. "These will have negative impacts on local health and local economies. "

The ORNL findings are consistent with those of researchers who reported on Climate, Extreme Heat, and Electricity Demand in California in the June 2008 issue of the Journal of Applied Meteorology and Climatology. They concluded that "[o]ver the twenty-first century, the frequency of extreme-heat events for major cities in heavily air conditioned California is projected to increase rapidly." They added that "present-day `heat wave' conditions may dominate summer months—and patterns of electricity demand—in the future" and that "[s]imilar increases in extreme-heat days are likely for other southwestern U.S. urban locations."

"By the end of this century, all model/scenario combinations indicate an increase in regionwide extreme temperature conditions of a severity associated with electricity shortages under the current configuration of the electric power system and patterns of demand," said the researchers.

Already, electricity reliability considerations are affecting business decisions. The researchers said:

"California’s electricity supply reliability problems in periods during which demand exceeds the available generating and/or transmitting capacity have already resulted in industries moving out of California to regions with a more dependable supply of electricity. In the future, this issue is likely to continue to plague California, the southwestern United States, and other heavily air conditioned regions in which electricity shortfalls occur."

WWF is sponsoring a competition among cities, the Earth Hour City Challenge, to encourage them to prepare for increasingly extreme weather and to promote renewable energy. U.S. cities that participate will receive resources and gain recognition for their efforts to curb carbon pollution and prepare their communities for the harmful consequences of climate change. Learn more about the City Challenge

Online Resources

Climate Change and Infrastructure, Urban Systems, and Vulnerabilities [PDF] (dated February 29, 2012; released May 2012). Report by Oak Ridge National Laboratory to the U.S. Department of Energy in support of the National Climate Assessment. 

Climate Change and Energy Supply and Demand.[PDF] (dated February 29, 2012; released May 2012). Report by Oak Ridge National Laboratory to the U.S. Department of Energy in support of the National Climate Assessment.

WWF Climate Change Blog:

World Disaster Reduction Campaign: Making Cities Resilient: 'My City is getting ready!' campaign

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