The role of thermal power plants (TPPs) is changing at a fast pace with the shifting fuel mix, led by the increasing share of intermittent renewable energy sources. TPPs, which have been the main source of baseload power in the past, are now increasingly expected to play a supportive role in the grid. Besides this, strict environmental norms and ageing thermal plant fleets have added to the challenges on the generation efficiency and power plant availability fronts. It is, therefore imperative for gencos to adopt advanced operations and maintenance (O&M) practices to align with emerging trends and requirements, and ensure efficient and uninterrupted operations. To this end, the deployment of new and innovative digital solutions such as digital twins, industrial internet of things, artificial intelligence and machine learning is gaining traction at TPPs. Developers are also deploying data analytics tools to improve cyclic efficiency through the detection of energy losses.
Need for O&M
With growing penetration of renewable energy in the power mix, TPPs are required to undergo several rounds of load cycling by quick ramping up and ramping down of their operations. In view of plans to meet 50 per cent of the country’s energy requirements by 2030 through renewables, thermal utilities will be required to run their plants at technical minimum levels, though these were originally designed for baseload operation. 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 revenue loss. 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.
Moreover, TPPs need to comply with stringent emission norms, especially considering the introduction of a penalty mechanism for non-compliant operations, which require operators to overhaul the existing pollution control systems. In addition, installation of new equipment such as flue gas desulphurisation systems and nitrogen oxide control systems will increase the capital and operational expenses of utilities. In order to maintain efficient plant operations in the emerging scenario, it is imperative for gencos to implement effective O&M strategies.
With the ageing of TPPs, utilities need to invest in renovation and modernisation (R&M) for efficiency improvement. R&M can help utilities achieve an increase in generation of 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 O&M practices
Most TPPs are being required to operate under minimum technical load because of the increasing integration of renewables. In order to maintain performance at low load, the use of secondary air damper control tools is gaining prominence. It helps in getting the best mill combination and maintaining an optimum boiler temperature. Optimisation of burners, reduced mill operation, application of advanced process control and predictive analytics, and enhanced digitalisation for boiler and turbine feed monitoring are useful to maintain plant performance during flexible operations.
The heat rate of a power plant is a crucial metric that directly affects the profitability of a firm. Heat rate degradation is caused by high energy drain valve passage, and therefore, it must be monitored frequently. Optimisation of cooling tower fans, cleaning of condenser tubes and monitoring the terminal temperature differential of heaters at regular intervals are being undertaken to improve the heat rate. One of the essential procedures at the fuel level is pile age monitoring, which helps decrease heat loss and maximise heat value utilisation. Further, advanced coal blending techniques are being undertaken to make the most efficient and cost-effective use of the fuel.
The use of gamma rays is gaining traction for monitoring emission assessing, assess electrostatic precipitator hopper emptiness and scheduling maintenance accordingly. Exfoliation meters are being used to monitor the deposition of oxide layers in coils. In order to identify metallurgical flaws, a small oil igniting system and a phased array of ultrasonic tests are being used. Further, an oxygenated treatment cycle chemistry programme can help decrease corrosion and iron carryover. Some of the other O&M practices that are increasingly being deployed include furnace mapping to evaluate boiler combustion and manage the furnace outlet temperature; deployment of equipment changeover tools to undertake scheduling of changeovers in accordance with SAP; cross-checking the air preheater intake for oxygen and carbon monoxide with a potable gas analyser for combustion optimisation; and the use of boiler tube leakage management, smart soot blowing, and insulation surveys of critical piping and furnaces.
In order to enhance the operational efficiency at a power plant, a strategy of maximal mechanisation with minimal manual work needs to be adopted. Electric impact wrenches, electrically powered 2T gantry cranes, electric-operated rotor stands, portable plasma cutting machines, battery-operated pick- and -carry cranes, or Teflon wheel-mounted fabricated trolleys are some of the examples of mechanisation. Apart from this, utilities should target and enhance key operational areas, while outsourcing non-important sectors to business partners that adhere to stringent key performance indicator monitoring. Inventory management should be implemented using vendor-managed inventories and an annual rate contract for fast-moving items.
Emerging trends in O&M
In recent times, new and innovative technologies are gaining popularity for efficient O&M. For instance, data analytics, machine learning and artificial intelligence are being used to track op-erating parameters for early detection of excursions or defects. Utilities are deploying data analytics tools for improvement of cyclic efficiency through detection of energy losses. These tools optimise the maintenance strategy by restricting unscheduled outages and eliminating unnecessary preventive maintenance. Equipment health monitoring is being undertaken through real-time monitoring of critical parameters and condition monitoring.
Utilities are also undertaking reliability-centred maintenance (RCM), which focuses on improving the reliability of power plants by providing insights on risk versus cost for the maintenance of a particular equipment. RCM employs preventive maintenance, predictive maintenance, real-time monitoring, reactive maintenance and proactive maintenance techniques in an integrated manner to increase the probability of the functioning of a machine or equipment in a required way that enables increased equipment availability, and reduces maintenance and resource costs. RCM focuses on reliability instead of availability. It follows a proactive approach to prevent failures, as compared to a reactive approach. RCM uses real-time data for analytics and predictions and identifies interventions for reliability improvement. It sends automatic notifications to the engineer when the health index crosses a certain threshold.
A robust maintenance strategy is based on root cause analysis of various kinds of equipment, generation loss and mean time before breakdown, thus optimising O&M. Based on the severity, frequency, detection rating and financial impact of the failure, failure modes and effects analysis of equipment is being performed. For essential equipment and operations, a zero-forced-outage plan is being developed. A preventive maintenance programme based on the equipment category is gaining traction, alongside strong condition-based maintenance.
Conclusion
In order to adopt an optimal O&M strategy, power plant operators need to undertake a thorough techno-economic analysis to identify the best-suited technology/solutions, as certain measures and technologies can entail significant capex, while others may be carried out through minor modifications. For this, 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 need to be factored in.
Adopting effective O&M methods has become essential in the coal-based power generating segment, given the constraints of a shifting fuel mix, flexible operation and tougher environmental and safety requirements. Employing the best O&M practices at TPPs not only help in achieving high levels of performance, but also maintain the health of the power plant equipment. Going forward, the adoption of O&M strategies and associated digital solutions is expected to pick up to ensure sustainable operations of gencos in times to come.
