By Christian Roselund
The organization that oversees reliability on the US electric grid has issued a report warning of an “elevated” risk of power outages this summer across the entire Western United States, and an even higher risk in the Midwest. The North American Electric Reliability Corporation’s (NERC) report was supported by another report providing similar warnings from California’s grid operator, even as Texas’ grid operator indicated that it has plenty of power for the summer.
Causes identified in the NERC and California Independent System Operator (CAISO) reports are complex. NERC’s Summer 2022 Reliability and Resources Assessment states that the primary driver of grid challenges across the West is a combination of severe drought conditions, which is reducing the output of hydroelectric generation, and extreme heat and wildfires. This drought is a contributing factor to the frequency and severity of wildfires, and in Texas to prolonged heatwaves.
For the Midcontinent System Operator (MISO) in the Midwest, NERC identifies several contributing factors including a long-standing failure to add sufficient reserve capacity and the loss of a significant powerline connecting its Northern and Southern regions. In all cases a changing resource mix, climate-driven extreme weather, and supply chain challenges all play a role in what may be the “perfect storm” for U.S. grids.
While climate-driven weather, and not renewables, is the primary cause of reliability concerns this summer, the shift to renewable energy intersects with this challenge in multiple ways. Specifically, NERC has identified the tendency of solar installations to “trip” offline during grid disturbances as a additional challenge to maintaining reliability. The report notes that this is often the result of lack of ride-through capability in inverters, which can “cause a minor system disturbance to become a major system disturbance.” NERC notes that these large-scale “tripping” events have been reported as recently as summer 2021. The organization has recommended various standards to make sure that inverters have the necessary ride-through capabilities.
Another place that solar comes up in the report is the circumstances on California’s grid. Southern California suffered extended outages due to insufficient power supply to meet demand during a heatwave in August 2020, and officials warn that this could happen again. Both the NERC and CAISO reports note that while the state has ample power from its widespread deployment of solar to meet demand during the day, as this output wanes in the evening there may not be sufficient resources to meet demand.
One challenge identified in both reports is the reduction in hydroelectric output not only in California but throughout the West as a result of the going drought. This makes it harder to import power, particularly when other grids are also at peak demand due to the widespread use of air conditioning. California’s regulators have been ordering the state’s utilities to procure unprecedented battery capacities, and CAISO estimates that 3,124 megawatts of battery storage will have come online between July 2021 and June 2022. However, it also warns that additions of batteries have not been enough to offset reductions in the state’s gas fleet.
A day before CAISO’s 2022 Summer Loads and Resources Assessment report came out, Governor Newsom revealed a new budget with $5.2 billion set aside for a 5-gigawatt Strategic Electric Reliability Reserve. This reserve could include existing generation that was scheduled to retire, new plants, new storage project, backup generation, and demand-side reduction programs that are visible to and dispatchable by CAISO.
Meanwhile, in Texas the grid operator is expecting solar to help keep the lights on. The state’s grid operator expects peaks to come between 3 pm and 8 pm and expects solar to contribute 81% of its nameplate capacity during this period.. Texas became the nation’s largest solar market in terms of annual installations 2021 and the 11 gigawatts of solar that the state has on its grid contributes 10% of expected capacity available to meet peak demand. However, the Electric Reliability Council of Texas (ERCOT) does not appear to have refined its methodologies to deal with the decline of solar output towards the end of this five-hour period. This could be a problem as the state comes to rely more and more on solar to meet peak demand.
It is notable that despite ERCOT stating that it has adequate capacity, NERC has warned that Texas could experience outages. NERC’s main concerns are prolonged heat waves that could stress the grid and cause reduced power from both thermal and renewable generation.
NERC singled out its strongest concerns for a grid with much less renewable energy generating capacity than California. MISO is running the lowest “reserve margin,” – the delta between capacity on its grid and its estimates of peak demand – of major any grid in the United States. NERC chided MISO for a repeated failure to add capacity, noting that this issue came up as early as 2018 and that between 2021 and 2022 MISO’s capacity declined.
While NERC rarely mentions specific generation sources in its report, MISO has been retiring coal-fired power plants at a rapid pace over the last decade. And while MISO has plenty of solar projects that have applied for interconnection, like other grid operators it is experiencing lengthy delays as it struggles with a higher volume of projects than it processed in the past. Furthermore, it is unclear how much MISO values solar’s contribution to grid reliability during peak demand, as each U.S. grid operator assigns a different value for this.
MISO appears to be banking on greater regional interconnection, but here extreme weather is again a challenge. NERC’s report notes that a transmission line providing 1,000 MW of “firm” power from its Southern region to its Midwest region was damaged by a tornado on December 10, 2021. This line will not be fully operational until the end of June 2022.
NERC notes that “supply chain issues and commissioning challenges” are also a concern where new generation and/or transmission is needed for reliability during summer peaks. The organization lists problems that are familiar to the solar industry, including product unavailability, shipping delays, and labor shortages, and singles out California and the Southwest as its areas of greatest concern.
Similar concerns were raised by Governor Newsom in a recent letter to Commerce Secretary Raimondo protesting the anti-circumvention investigation and warning that many of the solar and battery projects that were needed in the state were being held up. However, Commerce Secretary Raimondo has noted that the statute does not allow the agency to consider other policy priorities. While Secretary Raimondo named clean energy goals among these policy areas, electric system reliability may also be
Source: 2022 Summer Reliability Assessment (NERC)
Source: Summer Loads and Resources Assessment (California ISO)
Source: Seasonal Assessment of Resource Adequacy for the ERCOT Region (Electric Reliability Council of Texas)