As India works toward its target of 500 GW of non-fossil fuel capacity and 50% non-fossil-based installed capacity by 2030, improving grid flexibility has become a policy priority. (File Photo)India’s grid operator curtailed as much as 23 gigawatts (GW) of renewable energy between May and November last year to maintain grid safety and stability, as rising green power generation collided with the operational limits of coal-fired plants. The curtailment was largely necessitated because a significant portion of India’s coal-based thermal fleet is unable to operate below 55% Minimum Technical Load (MTL), according to a report by a committee of the Central Electricity Authority (CEA).Minimum Technical Load (MTL) is the lowest stable generation level at which a thermal unit can safely operate without shutting down. With renewable energy (RE) generation surging during daytime hours, a lower MTL is increasingly seen as essential to allow coal plants to back down further and accommodate green power. The report observed that heavy RE curtailment shows the urgent need for deeper thermal flexibility. Enabling two-shift operation and operation of thermal power plants at lower technical minimum loads below 55% is crucial to avoid renewable curtailment and ensure secure grid management, it added.‘Duck curve’ pressures, grid security concernsGRID-India, which manages national electricity grid operations, told the CEA committee that the growing share of renewable energy is intensifying the “duck curve” phenomenon in the Indian power system. This is marked by surplus renewable generation during mid-day hours and a steep evening ramp-up requirement of nearly 60 GW, posing operational challenges.Flagging grid security risks, GRID-India said that in May last year, system frequency remained above the Indian Electricity Grid Code (IEGC) operating band for nearly 20% of the time. Notably, the permissible band of system frequency is 49.900 Hz – 50.050 Hz.Sustained high-frequency conditions persisted for almost four hours during solar generation hours, reflecting the strain of surplus supply.“On May 25, 2025, despite backing down the national thermal fleet to approximately 58% and curtailing nearly 10 GW of solar generation through TRAS emergency down dispatch, system frequency still rose to 50.48 Hz, posing a serious concern for safe and secure grid operation,” the committee report noted, citing GRID-India. The data reveals that the highest renewable curtailment, over 23 GW, occurred on October 12, followed by over 16 GW on November 9. Curtailment exceeded 13 GW on September 28 and June 1, crossed 11 GW on May 31 and August 10, and was lowest at 4.6 GW on July 29. GRID-India informed the committee that the peak RE curtailment of 23 GW in October occurred during high solar generation hours, primarily due to the inability of several thermal power stations — particularly at the intra-state level — to operate at 55% MTL.Roadmap for flexibilityAs India works toward its target of 500 GW of non-fossil fuel capacity and 50% non-fossil-based installed capacity by 2030, improving grid flexibility has become a policy priority.Story continues below this adThe CEA has outlined a phased roadmap to enable coal-fired power plants to operate at 40% MTL by 2030. In addition, measures such as two-shift operations of thermal plants, deployment of battery energy storage systems, and expansion of pumped storage projects (PSPs) are considered essential to manage variability and reduce renewable curtailment.GRID-India also told the committee that while most inter-state generating stations and several state units have technically achieved 55% Technical Minimum Load, many generating units remain constrained from operating flexibly due to commercial and regulatory factors — suggesting that the challenge is not purely technical, but structural. © The Indian Express Pvt LtdTags:renewable energy