The Electric Reliability Council of Texas on May 6 said it expects power demand to set a record of 77.1 GW this summer, up from the existing record of 74.8 GW, but the reserve margin is forecast to be above the 13.75% target for the first time since 2017.
Also, ERCOT in its final Seasonal Assessment of Resource Adequacy for summer 2021 sees low risk of an Energy Emergency Alert, such as occurred during the mid-February winter storm when as many as 4 million customers lost power for various amounts of time, some for several days. Wholesale power prices also surged to the $9,000/MWh systemwide offer cap for almost that entire week.ERCOT North Hub forwards weakened in morning May 6 trading, possibly in reaction to the report. ERCOT North Hub July-August on-peak power fell $1.30 to about $468.65/MWh on the Intercontinental Exchange, and the ERCOT North Hub August on-peak package fell $2.90 to about $82/MWh.
ERCOT calculates the summer reserve margin this summer at 15.7%, up from 2020's 10.6%, and the highest since the summer of 2017, when the reserve margin was calculated at 16.9%. ERCOT includes the months of June through September in is summer assessments.
The reserve margin is the percentage by which expected peakload is exceeded by expected resources. The Public Utility Commission of Texas has set 13.75% as a target to ensure that a capacity-related blackout occurs no more often than one day in 10 years.
EXTREME SCENARIOS MULLED"While the risk for emergency conditions remains low this summer based on many of the scenarios studied, a combination of factors in real time, including record demand, high thermal generation outages and low wind/solar output could result in tight grid conditions," said Woody Rickerson, ERCOT vice president of grid planning and operations. "We cannot control the weather or forced generation outages, but we are prepared to deploy the tools that are available to us to maintain a reliable electric system."
ERCOT will visit certain power plants to review their summer weatherization plans, which will be the first time such visits will have been done for summer. Previous visits were for winter readiness.
LESS THAN 1% CHANCEFor this final summer SARA, ERCOT introduced three new extreme scenarios with less than 1% chance of occurrence. The mid-February winter storm was calculated as a "one-in-100 event," ERCOT said in its news release.
However, each of those "extreme reserve capacity risk scenarios would have resulted in total load exceeding available supply. The scenarios that would require rotating outages and the total load that would be unserved include:
**High peakload and thermal generation outages, low wind output, expected solar output: 3,947 MW unserved
**High peakload and thermal generation outages, low and and solar output: 8,072 MW unserved
**Extreme peakload and thermal generation outages, based on statewide heat wave, low wind and solar output: 14,584 MW unserved
"Looking ahead, the grid operator is monitoring new operational risks resulting from a changing resource mix," ERCOT said. "While tight grid conditions have historically been limited to the hours of highest electric consumption, ERCOT now sees the potential for tight conditions during low wind conditions, or during the early evening hours when solar resources come offline. As the capacity of battery storage increases in ERCOT, these resources are expected to help mitigate some of this risk."
FALL, MULTI-YEAR ASSESSMENTSERCOT also released its preliminary SARA for the fall of 2021 and its twice-yearly Capacity, Demand and Reserves Report, which showed more of a cushion between supply and demand.
The autumn report, which covers October and November, forecasts that the system would hit a seasonal peak of 62.7 GW in that season, while its resources would total more than 76.1 GW, yielding reserves totaling about 13.4 GW after deducting planned and typical forced thermal outages.
Under other, less likely but more conservative scenarios, the reserves could range from as much as 10.7 GW to as little as 708 MW. In the latter case, ERCOT would need to call on Emergency Response Service and other resources totaling 2.2 GW, but no forced load shedding would be required.
More extreme scenarios, such as high peakload and generation outages combined with low wind output could result in forced load shedding.
ERCOT's CDR report looks at five- and 10-year time horizons and calculates expected summer and winter reserve margins, given expected increases in generation capacity and load growth. ERCOT expresses greater confidence in the five-year report, which shows the following summer reserve margins, under the more likely scenarios:
