Renovation and modernisation (R&M) has been recognised as a cost-effective option for obtaining additional generation and better output from existing thermal power units. R&M can improve the performance, safety and reliability of units, help in complying with the stricter environmental norms by reducing emissions, and enhance flexibility. Meanwhile, life extension (LE) works can extend the useful life of old thermal power units by 15 to 20 years beyond the original design. A centrally sponsored scheme was launched in 1984 for R&M and LE, which has benefited several thermal generating units over the years. R&M and LE works for seven units with a cumulative capacity of 997 MW have been completed as of September 2022.
However, R&M is no longer limited to plant performance improvement. With the country’s goals of reducing carbon emissions by 1 billion tonnes and lowering the emissions intensity of its GDP by 45 per cent by 2030, the installation of emission control equipment at thermal power plants (TPPs) has become crucial, necessitating retrofits. Further, given that coal-based power plants have to be made flexible to incorporate greater amounts of renewable energy, power plant owners need to undertake appropriate retrofits as well.
Needs and requirements
Emission norms compliance: The Ministry of Environment, Forest and Climate Change notified revised emission norms for SOx, NOx and particulate matter (PM) for TPPs in December 2015, mandating TPPs to install emission control systems. The deadline for compliance has been extended several times, and as per the last revision, notified in September 2022, for coal-based units that fall under Categories A, B and C, it has been set at December 31, 2024; December 31, 2025; and December 31, 2026 respectively. Further, TPPs retiring before December 31, 2027 will not be required to meet SO2 emission norms. Meanwhile, TPPs declared to retire before December 31, 2022 (Category A) or December 31, 2025 (Categories B and C) will not be required to meet the specified norms other than those for SO2 emissions. The environmental compensation to be levied on non-compliant power plants for operation beyond this timeline is Re 0.20 per unit, Re 0.30 per unit and Re 0.40 per unit for 0-180 days, 181-365 days, and 366 days and beyond respectively.
In order to meet these norms, flue gas desulphurisation (FGD) systems have been planned for 600 units aggregating 211.52 GW. As per the Central Electricity Authority’s (CEA) latest report, as of March 2023, FGD systems are now operational in 22 units aggregating 9,280 MW. State sector plants have planned FGD installations for 222 units aggregating 68,266.5 MW, while central sector plants have planned installations for 168 units totalling 67,250 MW. Sector-wise, bids have been awarded for 135 units in the central sector, 46 in the private sector and 38 in the state sector, representing 80 per cent, 17 per cent and 22 per cent of the total planned capacity, respectively. A total of 219 bids aggregating 100,430 MW have been awarded, accounting for 47.5 per cent of the total planned capacity.
Besides FGDs, other technology retrofits are also needed by TPPs such as electrostatic precipitators (ESPs) for controlling PM emissions. The CEA has published a comprehensive proposal explaining the strategy for the augmentation of ESPs for PM control up to 2024. NTPC has planned for R&M of ESPs aggregating 15,960 MW of capacity, out of which work has been completed for 12,100 MW, and is in progress for the remaining 3,860 MW.
Flexibilisation: TPPs need to be made more flexible in order to incorporate the growing share of renewables, which is targeted to reach 500 GW by 2030. In the near future, TPPs are expected to operate at an average minimum load of 40 per cent. For this, TPP units that have so far operated as baseload plants will need to be overhauled. R&M of TPPs can increase their ramp rates and help adjust to cyclic load variation.
The CEA has brought out a comprehensive report on the flexibilisation of coal-fired power plants, which highlights the operating procedure, challenges, retrofits and roadmap for achieving 40 per cent load operation. As per the report, flexible operation of such plants can be made technically feasible through upgrading and tuning controls. The report has further devised a phasing schedule with a minimum estimated time period of eight years for making 600 units flexible in order to achieve up to 40 per cent load and higher ramp rates. The complete refurbishment work is estimated to be completed by December 2030.
Conclusion
A holistic approach to R&M is needed to help power plants adapt to the emerging power sector requirements. A combination of policy, regulatory and industry efforts will be required to increase the uptake of R&M works.