PLN Modifies Coal Mills at Power Plants to Boost Electricity Reliability

State electricity firm PT PLN (Persero) has modified several coal-fired power plants (PLTU) to prevent a recurrence of blackout incidents. The company carried out a retrofit, or technical adjustment, on existing generating units to enable them to consume low-calorie coal. PLN President Director Darmawan Prasodjo stated that the effort was a response to the declining production trend of medium and high-calorie coal above 4,500 kcal/kg, while the current larger supply trend is low-calorie coal. At least two PLTUs have been retrofitted, namely Suralaya 6 and 7, with the possibility of continuing at other plants. “We have carried out a retrofit on the Suralaya 6 and 7 power plants by changing their mills. Following the success of the retrofit at Suralaya 6 and 7, we are immediately conducting project feasibility studies at all PT PLN Persero plants,” he said during a Hearing Meeting with Commission XII of the Indonesian House of Representatives. Through the modification of the coal grinding equipment, the Suralaya PLTU is now able to use low-rank coal in the range of 4,100 to 4,300 kcal/kg, whereas previously the unit required a higher specification of 4,600 to 4,800 kcal/kg. “Because the supply of high and medium-calorie coal is increasingly depleting, we are making adjustments to our plants with the aim of preventing a recurrence,” he said. In addition to machinery adjustments, PLN is optimising plant operations during low-load periods between 00:00 and 06:00 WIB. Excess power generated during these hours is stored in a Battery Energy Storage System with a capacity of 4 GWh, equivalent to 500 MW, to strengthen power reserves. “This improves system reliability where there are still under-utilised plants that can be optimised to capture their energy,” he explained. The company confirmed that electricity conditions, particularly in Java, have returned to stability. PLN is committed to maintaining system reliability 24 hours a day to support public activities and sustainable national economic growth. “There have been no rolling blackouts in the Java electricity system since 21 June 2026. We will continue to jointly maintain and improve this condition through a system reliability strengthening programme,” he concluded.