The role of coal-based power is changing rapidly with the increasing integration of renewables. Thermal power plants (TPPs), which were the main source of baseload power in the past, are now expected to play a supportive role to balance the variable renewable energy generation. These changes, coupled with tougher environmental norms and ageing thermal plant fleets, have posed challenges for utilities in terms of efficiency, generation and availability, thereby necessitating a move towards advanced operations and maintenance (O&M) practices.
As a result of the growing penetration of green energy, TPPs are required to undergo several rounds of load cycling by quick ramping up and ramping down. Owing to temperature and pressure changes in the process, plant equipment undergoes extreme stress, often leading to creep-related failures. With further increase in the integration of renewables, which are projected to meet 50 per cent of the country’s energy requirements by 2030 as announced by the prime minister at COP26, thermal utilities will be required to run their plants at technical minimum levels, though these were originally designed for baseload operation. This is likely to lead to unstable furnaces, high secondary heat rates and increased secondary oil consumption.
Moreover, the increasing stringency of emission norms for TPPs and the introduction of a penalty mechanism for non-compliant operations means that existing pollution control systems (such as electrostatic precipitators [ESPs]) need to be overhauled. In addition, with the installation of new equipment such as flue gas desulphurisation systems and NOx control systems, the capital and operational expenses of utilities are set to rise. In order to ensure smooth plant operations, it is imperative for gencos to implement effective O&M strategies.
Additionally, the ageing of power plants means that utilities need to invest in renovation and modernisation (R&M) for efficiency improvement. R&M can help utilities achieve an increase in generation by about 30 per cent and an efficiency improvement of up to 23 per cent. While the addition of 1 MW of generating capacity requires a capex of around Rs 60 million per MW, an equivalent capacity can be achieved by investing around one-third of this amount in R&M activities.
Best practices and technology trends
In recent times, new and innovative technologies are gaining popularity for efficient O&M. For instance, data analytics, machine learning and artificial intelligence can be used to track operating parameters for early detection of excursions or defects. Utilities can deploy data analytics tools for improvement of cyclic efficiency through the detection of energy losses. These tools can also help optimise the maintenance strategy by restricting unscheduled outages and eliminating unnecessary preventive maintenance. Equipment health monitoring can also be undertaken through real-time monitoring of critical parameters and condition monitoring. Further, robotics can be used for the detection of silting in underwater pipes, while drones can be used to measure the volume of coal piles and inspect bunkers.
On the fuel side, utilities often undertake thermal imaging of coal yards to reduce heat loss. In addition, pile age monitoring can assist in reducing heat loss and maximising heat value utilisation. Further, selective bunkering can help in the utilisation of low calorific value coal during technical minimum load.
Other key O&M practices include the use of gamma rays to detect ESP hoppers’ health, installation of exfoliation meters, furnace mapping for boilers and furnaces, usage of smart soot blowing, optimisation of cooling tower fans, and insulation surveys of critical piping and furnaces. Some common flexibilisation measures include optimisation of burners, reduced mill operation, application of advanced process control and predictive analytics, and enhanced digitalisation for boiler and turbine feed monitoring.
Cycling and part-load operation of TPPs close to technical minimum levels leads to thermal stress, component deterioration, poor heat rate and increased auxiliary power consumption, resulting in higher opex and outages, and consequent loss of revenue. Improved O&M practices such as real-time asset monitoring, along with data and predictive analytics, can help gencos mitigate these issues and ensure higher efficiency as well as cost savings. Gencos should undertake a thorough techno-economic analysis, as certain measures and technologies can entail significant capex, while others may be carried out through minor modifications.
In addition, the increased operational expenditure on account of a higher heat rate, wear and tear of components due to cycling, and oil consumption for frequent start-ups also needs to be factored in. In the near future, generation utilities need to scale up their O&M strategies manyfold in order to ensure sustainable operations in times to come.