Beating the heat: How ISO-NE prepares for summer peak demand

As the region gears up for a season of fun in the sun, ISO New England prepares for conditions unique to the hot, humid summer months. Peak demand brought on by warmer weather and an increased reliance on energy-intensive technologies, such as air conditioning, can create complex challenges for the grid operator.

To maintain a reliable supply of electricity to New England’s residents and businesses, the ISO’s System Operations team must rely on carefully planned procedures to increase power generation and curb consumption during periods when demand for electricity threatens to exceed available capacity and reserves. This situation can be due to an unplanned resource outage—when a transmission line or generator suddenly goes offline—or simply because of high electricity usage.

Factors that affect the grid

Temperature and dew point both play pivotal roles in determining demand on the system. The difference between a normal summer temperature of 90°F and heat wave conditions of 94°F can result in over 2,000 extra megawatts (MW) of demand. While the colder weather of winter also creates a dramatic rise in electricity usage, the summer peak is different because it extends throughout much of the day—when the ramp up begins by midday and stretches well into the evening. Instead of a typical two- or three-hour peak that occurs on a winter day, the hot summer weather usually creates six hours of consistently high demand. When this pattern of prolonged peaks extends over several days, the demand for electricity builds, and that often leads to stress on the system.

Pre-summer checklist

Each year the transmission and generation resources on the system prepare for summer by conducting maintenance and repairs that will ensure readiness for the high loads that hotter weather brings. Heading into the summer months, ISO New England closely monitors weather forecasts, fuel source availability, and other factors that may affect the grid to get a sense of what conditions system operators will be facing. The System Operations team takes special care to stay on top of these conditions and manage their impact on the system. A summary of expected demand and conditions of the grid is compiled into a summer outlook press release.

Actions before and during a Capacity Deficiency

As hot summer weather sets in, the grid operator keeps a watchful eye on changing conditions. The ISO issues a Morning Report and a Seven-Day Forecast that list expected demand, capacity, and reserves on a daily and weekly basis, respectively. These reports give stakeholders and the public a clear understanding of the grid’s available resources and advance notice of any possible challenges on the horizon.

Sometimes the grid experiences issues due to weather-related factors or unexpected maintenance requirements. In the event of abnormal system conditions, the ISO issues Master/Local Control Center Procedure No. 2 (M/LCC2). This notification alerts applicable power system operations, maintenance, construction, and test personnel, as well as market participants, that an abnormal condition has occurred or is expected to occur, and that they should cease any testing or maintenance that could affect reliability. While an M/LCC2 event is not an indication of a shortage of supply and reserves, most deficiencies are preceded by an M/LCC2 notification.

The grid can enter a “capacity deficiency” when available resources are insufficient to meet anticipated demand plus the required level of reserves. This can be due to a number of factors, such as the loss of a source of supply, issues with transmission facilities, abnormal system conditions, or even responding to requests from neighboring grids for assistance that would reduce New England’s reserves below the required margin. Because electricity cannot easily be stored, it’s crucial to protect capacity that’s being held in reserve. ISO New England maintains both 10-minute and 30-minute reserves—named for the capability of generating resources to deliver electric energy within 10 or 30 minutes.

If a situation jeopardizes grid reliability, the ISO has a series of long-established procedures it can employ. System operators can request assistance from neighboring power grids, draw upon 30-minute reserves, ask companies participating in demand-side resource programs to temporarily reduce electricity consumption, and ask the public to conserve electricity voluntarily. These actions are among the measures in ISO Operating Procedure No. 4, Action during a Capacity Deficiency (OP 4). Implemented in any order, they can be applied New England-wide, by state, or targeted to specific areas in order to maintain system reliability and preserve New England’s 10-minute reserves by providing generation and load relief on the system. While it’s always a good idea to conserve energy, many of these steps do not call for action by the public.

Information when you need it most

In addition to the open lines of communication between system operators and the region’s power plants, demand-side resources, and transmission owners, ISO New England posts information and frequent updates on power system conditions to its website. In the event of a capacity deficiency, the ISO provides OP-4 details in a number of places, including:

  • The Power Systems Conditions web page
  • The ISO Express dashboard
  • And if conditions require public requests for conservation, that information will be available on Twitter and through press releases

Readiness and reliability

While life in New England involves a certain amount of unpredictability when it comes to the weather, the ISO is prepared to address the challenges of seasonal extremes. By closely monitoring grid conditions and communicating information about the impact of weather and fuel availability, the ISO can direct efforts to maintain efficient operation of the system. Heading into this summer, one of the biggest concerns was uncertainty regarding liquefied natural gas (LNG) supplies in the Northeast Massachusetts/Greater Boston area. By proactively engaging with the power industry, gas industry, regulators, and environmental agencies through planning and communication the outlook has improved for LNG supply for the months of July and August. While the region has adequate fuel supplies for normal summer weather, extreme weather conditions or unexpected generator outages could still create local reliability challenges.

“As the grid operator, we’re capable of dealing with a wide variety of situations that could come up when demand for power is peaking,” says John Norden, Director of Operations. “ISO New England has the procedures, processes, and expertise in place to effectively resolve issues and ensure reliability of the bulk power grid.”

New England’s businesses and residents can also take steps to help keep demand in check. Simple measures such as raising air conditioner settings a few degrees, installing energy-efficient light bulbs, and turning off unnecessary lights, TVs, and other home and office equipment can have an impact.