Digitalising TPPs

Improving the operational efficiency and capacity utilisation of plants

Digitalisation of thermal power plants (TPPs) is paving the way for substantial improvements in the efficiency of generation. Deploying digital technologies increases capacity utilisation and fuel efficiency, while reducing emissions and operation and maintenance (O&M)  expenses, and helping make operations flexible. Digitalisation of TPPs primarily involves embedding sensors and smart devices in major plant components so as to increase safety, speed of operation and efficiency. Digitalisation improves power plant monitoring, fault prediction and optimisation of operations.

Digital surveillance and monitoring

Digitalising TPPs aids operators in monitoring the status and condition of all components in real time. It allows them to immediately identify, detect and repair anomalies and issues. In other words, real-time system-based surveillance of a plant helps operators identify and repair problems in time before they affect other subsystems. In addition, it also helps in isolating and ascertaining the exact machine or part that is malfunctioning, thereby saving time. These features have twofold benefits: reducing O&M expenditures, and improving the safety and security of plants.

Digitally linking critical power units to the monitoring stations of utilities can help in analysing huge amounts of fleet data for continuous monitoring and diagnostics of these assets. It can enable pro­active maintenance, helping reduce unplanned outages and thereby optimising costs and increasing the availability of the power assets of utilities. It can also have long-term benefits given that reliable and consistent monitoring automatically contributes to longer asset life.

The fault detection and diagnosis (FDD) system is a major monitoring system. It is equipped with sensors and advanced algorithms to detect, isolate and identify faults in real time. Primarily FDD systems identify whether a fault has actually occurred in a plant. Then, the system detects the exact component where the fault has originated and isolates it from the remaining subsystems. Such systems also identify the magnitude and time-variant behaviour of faults.

Another substantially useful monitoring technology is the steam and turbine evaluator, which aids in ensuring continuous and real-time availability of data regarding the quantum of stress accumulated by components. Steam turbines are subject to high pressure and thermal stress during load changes, as well as during start-up and shut-down of operations. Their longevity is determined by the cumulative effect of such stresses. A turbine steam evaluator helps in estimating the amount of stress in the system and predicting future stress.

Other monitoring technologies that can be incorporated in TPPs include acoustic emission monitoring, ultrasonic corrosion monitoring and vibration monitoring systems.

Prediction and analysis

Embedded sensors, real-time communication systems and centralised data acquisition systems can improve communication channels between complex plant components such as boilers, turbines, condensers and emission controlling equipment. A substantial volume of data can be harnessed to model, estimate, analyse and predict the behaviour of the plant and its subsystems over time. Additionally, this stream of data can be modelled and analysed using the cloud, artificial intelligence/machine language, neural nets, advanced process control, digital twins, etc. to accrue benefits that reduce O&M costs.

In recent years, several plants have been incorporating digital twins in their plant systems to optimise operations and to estimate and diagnose potential issues in advance. For example, a combined cycle gas turbine digital twin can prevent catastrophic failures through early fault detection and dynamic root cause analysis. Additionally, digital twins replicate the behaviour of real-time physical systems while communicating with the actual system in real time and making recommendations to improve plant operations.

Similarly, advanced process control (APC) systems collect data across several system-related parameters and provide predictive and prescriptive guidance regarding plant maintenance. These functions are specifically useful for TPPs that regularly flexibilise their operations, given that they help in predicting the necessity for component repairs by estimating the stress accrued from ramping up and down. Moreover, they take into consideration other factors such as steam flow rate, coal consumption and overall plant efficiency by modelling heaters, turbines, boilers and condensers to estimate short-term and long-term operational efficiency. This allows operators to take decisions accordingly and conduct repairs in advance, thus keeping O&M costs to a minimum.

Plant optimisation and efficiency enhancement

Deploying digital technologies in TPPs will help operators smoothly optimise different TPP assets while coordinating and aggregating different subsystems seamlessly. Effective optimisation of plant operations enables TPPs to increase output, lower variable costs, reduce emissions and improve flexibilisation capacity. There are several areas, such as process efficiency, auxiliary operations efficiency, emissions efficiency, and flexibilisation, where digitalisation can improve efficiency by optimising operations.

Improving process efficiency involves optimisation of TPP operations by enabling the use of minimal input to generate maximal output. For instance, digitalisation can help in optimising the heat rate in boilers such that it is as low as possible, while constantly maintaining operations with minimal variations in heat within boilers. This is accomplished by adjusting and optimising the heat rate in accordance with the data provided by steam and turbine evaluators. This is especially important in modern supercritical and ultra-critical TPPs where the margin for error is very low.

In an optimum power plant, efficiency depends on keeping the plant within a narrow range of steam cycle operating conditions. Lower error tolerance levels and volatility make it easier to maintain efficient generation. Optimising coordinated boiler/turbine control for grid frequency support can also be achieved using digital technologies. Additionally, utilising digitally connected systems will lead to enhanced operational coordination between coal transportation and boiler operations. Consequently, coal movement can be optimised using digital equipment, such that TPPs switch over to just-in-time coal procurement practices and operate seamlessly even during periods of declining inventory.

Power plants are, by themselves, large users of electricity due to an array of auxiliary systems such as pumps, fans, compressors and drives. Several TPPs are trying to optimise the operation of all of these energy-consuming components in a bid to increase plant efficiency. The two new focus areas for optimisation are flexibilisation of operations and emission-related activities. By using digital twins and APC systems, a TPP can maximise the efficiency of electrostatic precipitators and flue gas desulphurisation units, increase production of fly ash by-products, etc. Furthermore, the rise in renewable capacity in the coming years will eventually lead to the relegation of TPPs to providing firm power in the background in a flexible way. As such, the digitalisation of TPPs would also help in their flexibilisation by minimising heat loss, reducing damage from ramping up and down, predicting flexibilisation demand in advance, etc.

The way forward

Digitalisation of TPP operations can improve plant efficiency, reduce O&M expenditure, augment asset life, improve the safety of operations and reduce emissions, while being commercially viable. It is estimated to improve the efficiency of operations as well as capacity utilisation by 25-40 per cent, depending on the type of technology and the extent of digitalisation. Nonetheless, the risks, such as cybersecurity threats, lack of interoperable digital equipment and inadequacy of reliable supply chains for digital equipment, could constrain widespread digitalisation. Hence, it is vital for suppliers, gencos, governments, financiers and other stakeholders in the ecosystem to collaborate and devise a comprehensive roadmap to ensure digitalisation of TPPs.

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