US resource adequacy planning must account for more extreme weather: EPRI

Resource adequacy planning by US power grid operators has not kept up with the increasing frequency and intensity of extreme weather events and system operators should develop sophisticated modeling and scenario analysis to better prepare for extreme weather, the Electric Power Research Institute said Feb. 18.

"So much of our economy already rests on the electric sector, but as more of our economy becomes reliant on electricity, and our grid continues to integrate more low-carbon renewable resources, we must change the way we assess the reliability of our system," EPRI CEO Dr. Arshad Mansoor, said in a statement.

The comments were made amid a massive winter storm that knocked out power to millions in Texas, with 46 GW of power generation capacity offline on Feb. 17, and real-time wholesale power prices in the Electric Reliability Council of Texas market hitting $9,000/MWh, the systemwide offer cap.

RELATED: ERCOT ends rolling blackouts; 40 GW of generation out, prices at $9,000/MWh

ERCOT instituted rolling blackouts as power demand surged in the cold weather and outstripped generation capacity.

EPRI recently released a technical report about the impacts of extreme events on the grid in which scientists and engineers concluded that grid operator planning processes, including resource adequacy planning, typically do not consider extreme climate scenarios that a resilient power grid must be able to handle going forward.

Traditional planning processes do not represent how power grid resources actually perform under extreme conditions, EPRI said.

ERCOT's extreme winter power demand forecast was 67.2 GW, according to its Winter 2020-2021 Seasonal Assessment of Resource Adequacy. Power demand reached 69.2 GW on Feb. 14, according to S&P Global Platts data.

A little over 40 GW of generation remained on forced outage due to the winter weather event, ERCOT said Feb. 18. Of that, 23.5 GW was thermal generation and the rest was wind and solar power.

Total US gas production was down 17% on Feb. 18 or 15.2 Bcf/d to a total of 75.4 Bcf/d from an average prior to the storm of 90.6 Bcf/d, according to S&P Global Platts Analytics.

"It is possible that some level of rotating outages may be needed over the next couple of days to keep the grid stable," ERCOT said.

EPRI recommendations

With extreme weather events and limitations on natural gas availability occurring more frequently, the metrics and methodologies for addressing these events have not kept pace, EPRI said in the report titled Exploring the Impacts of Extreme Events, Natural Gas Fuel and Other Contingencies on Resource Adequacy.

As a result, it is necessary to understand events that can simultaneously impact multiple generating units and to develop metrics and methodologies to measure and plan for their impacts on resource adequacy, EPRI said.

The report offered six interconnected recommendations on tools to be developed:

1. Scenarios by region of high impact, common mode events, and estimate the probability distributions of the scenario's physical impacts and associated economic costs;
2. Regional Value of Loss Load studies that update and extend the available estimates of customer outage costs;
3. A modeling framework to combine an operational model of the natural gas pipeline network with a production costing power system model;
4. A disruptive weather classification system including intensity, geographic coverage, and duration directly targeted for use by the US electricity market;
5. Value of Load at Risk as a conceptual framework to address the shortcomings of the current resource adequacy metrics; and
6. A stochastic mathematical programming model for resource planning and pricing resource scarcity.

"A recognition of the rising frequency of common mode failures provides the opportunity to better understand when a combination of low output from variable renewable sources, uncertainty in output from gas generation, and disruptive weather can lead to widespread outages," EPRI said.

Mansoor said existing grid supply and delivery assets must be hardened for climate change scenarios regardless of generation type, as extreme weather events have adversely impacted all generation types, some more than others, relative to the output that was expected in the ERCOT resource adequacy planning.

Additionally, he said broader interconnection with other systems through new transmission will increase access to diverse resources and fuel supplies and "is a critical piece of a resilient grid that accommodates more low-carbon resources."