A Step Up

Digital solutions at TPPs get more sophisticated

The deployment of digital solutions at the boiler, turbine and generator (BTG) level has gained traction in the past couple of years in view of the increasing renewable energy integration into the grid and tightened emission norms for thermal power plants (TPPs). Besides, the digitalisation of power plants ensures efficient and cost-effective power generation. It helps generate plant-specific operational and contextual data, including operational history, unexpected degradation of plant equipment, etc. It also offers tailor-made countermeasures for performance improvement. With the introduction of machine learning, artificial intelligence (AI) and cloud computing solutions, power plant developers have been able to achieve greater sophistication in their digitalisation efforts and solve complex problems with ease.

Growth drivers

In the current power sector scenario, one of the key growth drivers for the digitalisation of TPPs is large-scale renewable energy penetration, which requires flexible loading of TPPs and poses a threat to electrical grid stability. Renewable energy sources are characterised by variability and uncertainty of power generation, resulting in ducking of the load curve. This lowers the plant load factor (PLF) of TPPs. With increasing renewable energy penetration, TPPs need to frequently ramp up and down power generation, resulting in poor heat rate, high auxiliary consumption, increased forced outages, higher operations and maintenance (O&M) and reduced equipment lifetime. The digitalisation of BTGs helps in maintaining operational efficiency under flexible power plant operations. A fleet-wide digitalisation of O&M practices helps TPPs meet these dynamic requirements. Meaningful inferences can be drawn from the operational data collected from different plant equipment through machine learning and AI as well as plant-specific algorithms that aid in maintaining plant performance under flexible operations.

Another driver for digitalisation of TPPs and BTGs is the increasing cost of complying with the environmental regulations. The revised norms are creating additional operational complexity in TPPs and straining their operating margins. Digital solutions can support and facilitate this transition to low-emission power generation through asset optimisation strategies that take into account emissions, abatement costs and equipment life.

Another benefit of digital solutions is better human resource management. Digitalisation offers immense potential for enterprise management through real-time network monitoring and reporting. Customised dashboards, business intelligence tools, digital work processes and blockchain-enabled transactions can help power generation companies move towards analytics and data-driven decision-making. Apart from this, digitalisation plays an important role in asset management at TPPs. Internet of things technology can enable power plants to undertake predictive maintenance, thus enhancing their reliability. It also enables augmented reality-assisted maintenance, and robot and drone-assisted maintenance.

Another function of digital solutions in a TPP is asset management. Remote monitoring systems and diagnostic centres play a crucial role in this. An interactive display is used for performance monitoring. It deploys advanced pattern recognition and machine learning to identify anomalies in the operation of power plant equipment. Besides this, data from various connected machines is collected and sent to the monitoring system through a secured communication channel.

On the power generation front, digital solutions ensure an optimal fuel mix in power plant boilers. This helps maintain an optimal cost of power generation. Further, boiler efficiency can be calculated in real time, which can then be compared for different fuel types, bed material and limestone consumption. Optimum boiler efficiency can be achieved by analysing the long-term performance of boilers using different inputs. Apart from this, digital solutions help in managing merit order despatch in multi-unit plants.

Digital solutions for power plants

The digitalisation of BTG equipment in a power plant entails the use of sensors, actuators, digital controllers and supervisory computers. Through feedback control loops, plant processes and performance can be monitored and appropriate control actions can be taken to maintain optimum plant conditions despite system disturbances such as changes in coal quality and load demand. Meanwhile, machine learning and AI can help derive meaningful insights from operational data and take corrective measures to maintain plant performance, reduce unplanned outages and downtime, and extend the operational lifetime of assets.

With digitalisation, power plant operations can be remotely monitored and modified based on performance parameters. Further, remote monitoring and external support can address key human resource and knowledge retention issues. Remote monitoring and diagnostic systems (RMDS) can be deployed for the monitoring of TPP assets. The RMDS system comprises an interactive display for improved operations. It also has an advanced pattern recognition feature that uses machine for identifying any anomaly in plant operations. One such project has been developed by Bharat Heavy Electricals Limited (BHEL). Under this, data from various connected machines is acquired and sent to the BHEL cloud platform through a secured communication channel.

One of the emerging digital solutions is a digital twin. An organised collection of physics-based methods and advanced analytics is used to replicate every plant asset. The digital twin uses algorithms and models of AI and machine learning  to predict the future performance of the plant. The digital twin creates a digital model to study the plant’s characteristics. It leverages big data for driving efficiency and generation. Another cost-effective digital solution useful in the power generation segment is 3D printing, which helps in maintaining spare-readiness with the help of additive manufacturing. This minimises the lead time for spare part manufacturing.

Often digital solutions help in addressing issues pertaining to plant performance. One such solution is the blade vibration monitoring system (BVMS). It prevents last-stage blade failure in turbines, which occurs as a result of electrical corrosion, corrosion fatigue, stress corrosion, water corrosion and equipment fatigue caused by material quality issues, load variation, etc. BVMS tracks the performance of turbines and helps in improving plant availability and reducing the unplanned shutdowns.

Another digital solution for power plants is an acoustic steam leakage detection system, which helps track steam leakages in boilers with the use of sensors on a sonic tube. In case the sound of the steam leak exceeds a preset limit, an alarm is set off and the registered contacts are alerted. Apart from this, BHEL is undertaking drone-based monitoring of projects. The company has also developed a model-based predictive control system for power plants.

Flexibilisation

On the flexibilisation front, digitalisation is essential for bringing down the levellised system cost of flexible power through forecasting and automatic generation control.

Condensate throttling is a widely used digital solution to maintain plant performance in a quick response load change scenario. In September 2017, a condensate throttling-based primary frequency control solution was commissioned at NTPC’s Dadri TPP (Stage II, Unit 6). When the condensate water control valves close, the demand for low pressure heaters reduces and extraction steam has to pass through the last turbine stages, thus increasing the turbine power output. This is the basic principle of condensate throttling.

Some of the other digital solutions for flexible power plant operations are boiler auto-tune; combustion stability advanced monitoring systems; online predictive tools for predicting failures, providing maintenance advisory and predicting cycling costs; lifetime assessment tools and coal analysers.

Conclusion

Layering existing systems with digital technologies not only helps in improving the operational performance of TPPs at minimum expenditure, but also enables practical upgrades. By allowing flexibilisation of power plant operations and real-time tracking of operational performance, digitalisation helps in maintaining the competitiveness of conventional power plants. In order to derive the full benefits of digitalisation at power plants, developers must utilise the plant performance data in every possible way to predict future scenarios, enhance efficiency and minimise unexpected downtime. However, the digitalisation of TPPs makes them more vulnerable to cybersecurity attacks. Thus, utilities need to proactively manage the risks facing data and physical assets, and adopt best practices to keep systems secure and up to date. Further, for the successful implementation of digital solutions at power plants, it is essential to undertake change management, provide adequate training to the workforce and carry out an organisational review. Besides, identifying the right technology partners and the best-suited digital solutions is crucial for obtaining the desired outcomes.

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