Renovation and modernisation (R&M) is a cost-effective solution for enhancing the generation capacity of existing thermal power stations (TPSs) and optimising asset management due to its affordability and swift implementation. Given the capital-intensive nature of new installations, in order to maximise generation from existing power stations and ensure optimal resource utilisation, R&M is a viable option. Apart from boosting generation output and enhancing availability, R&M and life extension (LE) of thermal power plants (TPPs) yield additional advantages such as prolonging asset lifespan, enhancing safety, bolstering reliability and fostering better environmental conditions.
Progress so far
Since 1985, R&M/LE works have been conducted on a total of 661 units, collectively amounting to over 82 GW of capacity. From 2012 to 2017, R&M/LE activities were performed on units totalling 7,200 MW, contrasting with 17,000 MW from 2007 to 2012. Between 2017 and 2022, up to December 31, 2023, initiatives were conducted on eight units, namely, Ukai only TPS (Unit 4), Wanakbori TPS (Unit 3), Kathalguri CCGT (Unit 3), Kathalguri CCGT (Unit 6), Koradi TPS (Unit 6), Obra TPS (Unit 12), Obra TPS (Unit 13) and Barauni TPS (Unit 6), with a combined capacity of 1,197 MW. This period saw a continuation of efforts to enhance the operational efficiency and lifespan of power units across various facilities.
Going forward, the Central Electricity Authority (CEA) has identified 148 thermal units, totalling approximately 38,150 MW capacity, as potential targets for R&M/LE initiatives. A phased implementation plan for R&M/LE across these 148 units has been developed in collaboration with central, state and private power utilities.
Need for R&M in TPPs
Over time, the quality of coal used in many TPPs across the country has degraded. This necessitates potential augmentation of various systems such as raw coal feeding, pulverisers, primary air fan and ash handling systems to maintain boiler capacity at its rated level, with improved efficiency. Further, with environmental regulations tightening, plants equipped with older environmental control systems may not align with current emission standards, necessitating either refurbishment or complete replacement. Compliance involves upgrading electrostatic precipitators, retrofitting flue gas desulphurisation systems (FGD), modifying combustion and implementing zero liquid discharge systems.
Furthermore, incorporation of a large volume of renewable capacity into the power system necessitates reducing minimum load levels (up to 40 per cent) and implementing high ramp rates in TPPs. Consequently, refurbishment of power plants may be essential to accommodate the new operational paradigm. Revamping all related support systems including handling, storage, milling and operational aspects (such as boiler modification and ash handling) to enable thermal units to effectively co-fire biomass in accordance with current policies and regulations is also necessary.
Selection of TPPs and business models
Candidate plants are chosen based on residual life assessment (RLA), condition assessment (CA), destructive test studies and energy audit studies, along with existing performance data. This evaluation encompasses components such as boilers, turbines, generators, transformers, motors, heaters, fans and pumps. It is crucial to assess the remaining lifespan of these components after approximately 160,000 hours of operation to mitigate the risk of severe failures.
For R&M consideration, units with an installed capacity of 150 MW or more employing a reheat cycle are targeted. Units operating for 8-10 years with gross heat rate deviations exceeding 15-20 per cent from the design gross heat rate, despite regular annual overhauls, are also cases for R&M. Meanwhile, once these units complete 20 years of operations, LE assessments may be initiated. With regard to the cost of R&M/LE&U works, it should not exceed 50 per cent of the engineering, procurement and construction cost of a new indigenous generating unit. If limited to BTG, the cost ceiling should be restricted to 50 per cent of a new BTG unit’s cost, with detailed techno-economic viability studies conducted. The payback period should be capped at seven to eight years.
Various feasible options exist for investment in R&M schemes, with potential for innovation, based on state/utility preferences. One common approach involves power utilities undertaking R&M/LE work via competitive bidding for equipment supply and erection contracts, adhering to government guidelines. Another option entails forming a joint venture between the utility and private/public entities, including equipment suppliers or financial institutions, to own, operate and maintain the power station, while executing R&M/LE projects. Under this model, the utility may not bear upfront capital costs, funding projects solely from realised savings. Alternatively, R&M/LE implementation can occur through contract nomination to a reputable service provider or competitive bidding, with flexible payment structures based on performance improvement over a specified duration.
Challenges in R&M 
Despite being a government priority for over three decades, challenges persist, hindering progress and discouraging gencos from engaging in R&M programmes. Establishing techno-economic viability requires thorough cost-benefit analysis and expert advice to create feasibility reports. Poorly defined scopes of work lead to skewed risk-benefit analyses, compounded by poor operations and maintenance practices threatening project sustainability. Design, procurement, execution and final acceptance face challenges due to process complexities. R&M designs need to integrate past experiences and technical specifications to meet environmental norms. Regulatory mechanisms must accommodate sequential equipment supply and focus on additional item availability. Shortages of skilled labour further delay R&M project completion. Further, the surge in the prices of base materials such as steel, cement, nickel, aluminium and copper has resulted in price escalation for essential items such as tanks, ducts, pipe racks and supporting structures.
Conclusion
As the government emphasises R&M/LE works and streamlines the supply chain, the market becomes more favourable for vendors, especially in complementary projects such as FGD. R&M is pivotal in addressing challenges in the power sector, particularly amid the transition to renewable energy. By reducing capital expenditure, R&M frees up resources for renewable energy integration and enhances reliability in the power grid. Embracing new technologies can facilitate smoother R&M processes, contributing to achieving net-zero goals. Despite the vast potential for R&M in TPPs, minimising delays between technical studies and project execution is essential. Regulatory support is crucial for fostering R&M activities, ensuring sustained progress in modernising and optimising the power infrastructure.
Aastha Sharma