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Long-Term Reliability of the National Electrical Grid


The previous 5 posts have described the national electrical grid, how electricity flows on The Grid, how it is organized, Missouri’s portion of The Grid, and the complex balancing act that operators of The Grid face every day. Finally we’re in a position to look at the 2013 Long-Term Reliability Assessment. This is an annual report published by NERC, the North American Electric Reliability Corporation. The assessment identifies 6 main threats to long-term reliability. I will describe each in turn.

  1. NERC Problem RegionsResource adequacy in several reporting regions will fall below reserve margin targets. Let me explain. NERC believes that each operating region needs to maintain a generating and transmission capacity that is 14.2% larger than anticipated demand in order to ensure reliability. In the TRE-ERCOT region ( most of Texas), generating capacity will be below the target level for the entire period from 2014-2023. In the MISO reporting region, (the upper Midwest), it will fall below the target level by 2015. By 2023, reserve capacity will fall below the target in several additional reporting regions. (See map at right.) Without additional generating resources, an increased likelihood of “load shedding” is possible. “Load shedding” means that they turn off electrical service to some customers or some regions in order to avoid having the whole system collapse. Typically, the outages rotate so the burden is shared among all customers. The MISO region includes St. Louis and other parts of eastern Missouri, so this threat includes us.
  2. High levels of variable generation may present operational and planning challenges. Let me explain. We saw in the previous post that operating The Grid is a complex balancing act: enough electricity has to be delivered to meet demand, but operators have to be careful not to damage The Grid by flowing either too much or too little electricity through any one part of it. In this balancing act, generating stations that supply ever-changing amounts of electricity are a nightmare! It is like a high wire aerialist: if there is a constant breeze, he might be able to compensate for it. But if the wind starts gusting, he is in real trouble! Yet, that is precisely what wind and solar energy do – they deliver constantly changing amounts of energy. We need these kinds of power sources to reduce GHG emissions, and they represent an ever-increasing portion of the energy supplied to The Grid. But the challenge of managing these constant fluctuations poses a threat to Grid reliability that will have to be managed.
  3. NERC Capacity ChangeFossil fuel generating stations are being retired, and additional stations will experience outages for environmental retrofits. Capacity retirements are projected to surpass 85 GW by 2023. Combined with the addition of variable generating sources, these retirements will present a challenge to the long-term reliability of The Grid. The chart at right shows projected capacity changes for The Grid as a whole through 2023.
  4. Increases in natural gas-fired generation may require enhancements to planning and operations. This threat comes primarily from deep reliance on a single fuel source: what if the supply of that kind of fuel is interrupted, or experiences a spike in price? Currently, natural gas generating capacity is 39% of all generating capacity on The Grid, and by 2023 it is projected to increase to 42%.
  5. Increased use of demand-side management (DSM) creates more uncertainty for system planners and operators. We haven’t talked about DSM in this series yet. DSM programs seek to “manage” demand for electricity by customers. This can mean simply reducing overall demand by measures such as energy efficiency. It can also mean temporary load shedding through the cooperation of electrical consumers. For instance, suppose that a particular industry has a specific process that consumes large amounts of electricity. They might agree to avoid running that process during periods of peak electrical demand. In regions where peak demand occurs on hot, sunny, summer days, they might run the process only at night. DSM is new, however, and system planners and operators don’t have enough experience with it to predict how it will affect demand very accurately. Thus, it presents a challenge to long-term reliability.
  6. The retirement of nuclear generating stations presents reliability challenges. The fleet of nuclear generating stations in the United States was built during a relatively brief period – no new plants have been started since 1974, and until 2013, no new reactors at existing plants had been started since 1979. Nuclear plants were originally commissioned for a lifespan of about 20 years. They have lasted longer than that, and their operating licenses have been extended. However, they are approaching the end of their lifespan, and concerns about nuclear power have increased since the Fukushima Daiichi disaster. It is possible that their operating licenses will not be renewed, resulting in a 10% reduction in generating capacity on The Grid. The uncertainty represents a wild card in efforts to plan for the long-term adequacy of The Grid.


North American Electric Reliability Corporation. 2013. 2013 Long-Term Reliability Assessment. http://www.nerc.com/pa/RAPA/ra/Reliability%20Assessments%20DL/2013_LTRA_FINAL.pdf.

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