To address issues arising from the deadly mid-February winter storm which left about 4 million Texas electricity customers without service, some for days, Texas regulators on July 29 discussed potential changes to the Electric Reliability Council of Texas' scarcity pricing and outage scheduling rules.

The Public Utility Commission of Texas plans to discuss market design issues during an Aug. 26 workshop, and in a July 28 memo to the commission, Connie Corona, PUC deputy executive director, suggested that the commission issue a request for stakeholder feedback regarding potential changes to ERCOT's Operating Reserve Demand Curve (Project No. 51617).

The ORDC provides a way to calculate and administrative adder to systemwide prices to that increases as operating reserves decrease, so as to incentivize investment in generation, inasmuch as ERCOT has no capacity market.

In particular, Corona suggested asking stakeholders to offer suggestions regarding how the ORDC might be changed "to drive investment in existing and new dispatchable generation."

The February blackouts have been partly blamed on a lack of dispatchable generation.

At the suggestion of Commissioner Will McAdams, the PUC decided to allow commissioners to forward additional suggested questions to be included in the call for stakeholder feedback. Once the call for feedback is issued, stakeholders would have until Aug. 16 to respond, with a 10-page limit to filings.

Another factor in the February blackouts was that a relatively large amount of generation was on planned outage for maintenance.

Generation outage procedures

In response to Commissioner Lori Cobos' request for ERCOT's plans regarding how to ensure that planned outages do not inappropriately limit available capacity, ERCOT presented a proposal to revise its outage procedures.

Woody Rickerson, ERCOT vice president for grid planning and operations, said ERCOT processed about 26,000 resource outages in 2020, of which 60% lasted a day or less.

About 70% of those resource outages are forced or maintenance outages submitted with less than three days' notice, and as these involve resources that cannot physically operate, ERCOT has no way of rejecting them, Rickerson said.

Another 10% of planned outages are submitted with more than 45 days' notice, and current rules dictate that ERCOT cannot reject them, if that much advance notice is provided.

The remainder are a mix of planned outages, outage extensions and maintenance-level outages, of which some require ERCOT approval.

ERCOT proposes to change the second category, those submitted with more than 45 days' notice, such that ERCOT can "approve (or reject) within a defined timeframe as long as the approved aggregate amount of all outages is less than an allowable capacity for each day of the request," according to Rickerson's written presentation.

The goal would be to ensure that planned outages do not cause the amount of reserves to fall below ERCOT's new, more conservative, minimum reliability standards.

If a maintenance outage request is rejected, ERCOT may ask a resource owner to delay the planned work a week or two, Rickerson said.

Summer performance update

Commissioner Cobos also asked ERCOT to provide regular updates on its reliability performance over the course of the summer, and Kristi Hobbs, ERCOT's vice president for corporate strategy and PUC relations, responded with information about generation outages, which were excessive during a mid-June heat wave during which ERCOT called for consumers to reduce power demand.

For example, around 2:30 pm on June 14, ERCOT had 12.7 GW of generation on forced outage requiring repairs. Of that amount, about 9 GW was thermal, while the rest was renewable.

ERCOT's final Seasonal Assessment of Resource Adequacy for summer 2021 included scenarios with a high amount of thermal generation offline -- 6.2 GW versus a typical total of 3.6 GW -- and a 6.6-GW dip in wind output, leaving the wind fleet producing virtually none of the 6.7 GW expected load-carrying capacity of the system's 28 GW of installed and synchronized wind nameplate capacity.

A heat wave that struck Texas over the July 24-25 weekend resulted in peak demand of 70.6 GW on July 25, during which thermal outages were between 5 GW and 6 GW, Hobbs said. Demand peaked around 72.9 GW on July 26, Hobbs said, and thermal outages had fallen to about 4 GW.

On both days, wind output was low and solar output was high. During peak hours, 6 am to 10 pm, of July 25, wind output ranged from 2.4 GW to 11.8 with a median of 6.1 GW, according to ERCOT data. The peak-hour range on July 26 was 1.4 GW to 8.9 GW, with a median of 4.5 GW.

During daylight hours of about 8 am to about 8 pm on July 25, solar output ranged from 1.7 GW to about 6.5 GW with a median of 5.7 GW, and the comparable period of July 26 had a range of 2.8 GW to 6.5 GW with a median of 6 GW.