Read that again: a\u00a06-GW shortfall covered by 43\u00a0GW of batteries.<\/p>\n
Bennett\u2019s response to this rather obvious mismatch is to reframe the question entirely. Instead of asking whether batteries can cover peak demand windows \u2014 which is what they\u2019re designed to do \u2014 he converts the entire battery fleet into a\u00a0single energy metric: 77 GWh, which he says is \u200b\u201cequivalent to running a\u00a0single 1\u00a0GW thermal power plant for the duration of this three-day storm.\u201d It\u2019s a\u00a0striking comparison. It\u2019s also irrelevant to how batteries actually operate in\u00a0ERCOT.<\/p>\n
Nobody designs, operates, or dispatches battery storage as a\u00a072-hour baseload resource. Batteries are designed to shave peaks, provide rapid frequency response, and bridge the morning and evening demand ramps when solar output is low. A\u00a043-GW battery fleet can inject enormous amounts of power during exactly the narrow peak windows that Bennett\u2019s own Figure 2<\/a> identifies as the problem periods. During Winter Storm Heather, ERCOT\u2019s post-storm analysis<\/a> confirmed that batteries were \u200b\u201cpartially supplementing the lack of solar generation available\u201d during the coldest pre-sunrise hours \u2014 the exact scenario Bennett says they can\u2019t handle.<\/p>\n The thermal backbone he takes for granted<\/p>\n Perhaps the most revealing aspect of Bennett\u2019s analysis is what he doesn\u2019t discuss: the massive existing fleet of gas, coal, and nuclear generation that forms ERCOT\u2019s backbone. He projects 103,802\u00a0MW of firm winter output in 2030. That fleet \u2014 overwhelmingly fossil and nuclear \u2014 carries the grid through the vast majority of every storm hour in his model. The assumed thermal outage rate is only 12% \u2014 a\u00a0figure drawn from ERCOT\u2019s reliability assessments \u2014 meaning 88% of the thermal fleet performs through the modeled storm.<\/p>\n Bennett constructs a\u00a0scenario in which batteries fail by defining success as continuous 72-hour discharge, while simultaneously taking for granted the thermal fleet of 80-plus GW that keeps the lights on during the bulk of his modeled event. The batteries aren\u2019t replacing that fleet. They\u2019re supplementing it during the peak demand windows that the thermal fleet alone can\u2019t quite cover \u2014 which is precisely the role that ERCOT\u2019s system planning envisions for\u00a0them.<\/p>\n