Taking Gradual, Tech-Enabled Steps towards Cleaner Power Generation

The relevance of thermal power plants and the need for cleantech
Decarbonisation is a global imperative today, and India has made ambitious commitments in this direction. There is a strong focus on renewable-based power, alternate energy sources, and energy storage systems. However, electricity demand will grow steadily, and renewable-based energy solutions will take time to attain the desired scale and efficiency.

Thermal power will thus continue to play a big and important role in fueling India’s growth story for at least another decade or two. The National Electricity Plan 2022-2032 (NEP) projects an increase in coal generation capacities over the next decade from current levels of 235 GW (in 2022) to 259 GW (by 2032). The New Energy Outlook by Bloomberg NEF projects an increment in coal-fired capacity of 52 GW by 2050. In terms of volumes, the NEP projects that thermal plants will contribute around 56 percent of the total power generation in the country by 2032.

As thermal power plants running on old technologies tend to generate pollutants such as particulate matter, nitrogen oxides, and sulfur oxides, it is essential to run them more sustainably.

The solution lies in adopting cleaner technologies that significantly reduce the environmental impact of thermal power plants on all fronts: land, water, and air. A few among them stand out for viability and effectiveness. Similarly, while renewable energy has a lower environmental impact during its operational period, the use of modern and innovative technologies will make it even cleaner and more efficient.

Flexible Operations: The coal-fired plants are typically designed for a minimum stable generation level of 60 percent. The intermittent nature of renewables and the steep ramp-up and ramp-down requirements during the evening and morning peak hours present a technical challenge for the coal-fired power. The plants need to operate at much lower minimum loads and have fast ramp-up and ramp-down rates.

The Central Electricity Authority has recently notified the regulations for the flexible operation of thermal units. These regulations require coal plants to operate at a minimum level of 40 percent load and achieve ramp-up rates of 3 percent per minute. These are stiff requirements, and enabling these operational flexibilities requires significant modifications to the boilers, including changes in the plant control systems.
 
Flue Gas Desulphurisation (FGD): FGD is a set of technologies used to remove sulfur oxides from exhaust flue gases. Using wet scrubbers, or the latest designs of dry scrubbers, more than 90 percent of sulfur oxides can be successfully removed.

In our experience operating an FGD-equipped coal-fired plant, we have seen a reduction in sulfur oxides in a similar range. FGD systems have been in use since the late 1960s, but it was only in 2017 that the Indian government made them mandatory for thermal power plants.

Installing FGD systems is a time-consuming process with challenges when retrofitting an existing coal-fired plant. Some of the materials required for implementing the technology, like borosilicate lining, titanium cladding, etc., need to be imported. Implementation of FGD entails a significant upfront capital investment and an increased operating cost. Despite a strong push from the government, the percentage of coal plants with FGD continues to be low, at around 5 percent.

Selective Catalytic Reduction (SCR): SCR technology is used to control the emission of nitrogen oxides in thermal power plants. Most of the plants in India have installed combustion modifications and low NOx burners to control nitrogen oxide emissions. With the tightening of emission norms, SCRs will become inevitable. The local manufacturing capacity for SCR components is limited and would need to be enhanced. BHEL has taken steps to set up SCR manufacturing capacities.

Hybrid Filters: A combination of electrostatic precipitators and fabric filters is a great way to reduce particulate matter emissions. Both are highly effective in removing soot, ash, and particulate matter from exhaust fumes before they exit the smokestacks in coal-fired power plants, so that the emission levels remain well below the statutory limit. In our experience, we have been able to contain the particulate emissions significantly below the emission norms by using hybrid arrangements. The downside is an increase in operating costs as the bag filters need periodic replacement.

Zero Liquid Discharge (ZLD): Power plants consume the most water among all industry sectors. In a ZLD facility, all the wastewater is treated within the premises and reused for dust suppression, horticulture, cleaning, and other utilitarian purposes. Although installing a ZLD system entails a high initial cost, it is a worthwhile investment, especially in view of the looming water crisis in the country. We have successfully reduced specific water consumption by increasing the cycle of concentration. We are also exploring the use of RO filters.

Robotic Dredgers: Robotic dredgers can remove silt, sludge, ash, and other settled solids from water reservoirs in difficult environments, including at power plants. This can increase the holding volume of water reservoirs. Besides, this helps in eliminating diving activities and thereby improving the safety of operations.

Solar Modules, with Robotic Cleaners: Although solar energy is a clean energy source, the modules that are used in its generation need to be regularly cleaned with water. However, most large-scale solar installations are in dry, hot regions where water supplies are limited. The use of robotic cleaners can reduce water consumption by almost 85 percent, allowing the rest to be used for community purposes and other essential activities. We have transitioned towards 100 percent robotic cleaning of all our solar assets.

Real-time Monitoring: Efficiencies in the clean energy sector can be improved with the help of advanced systems for monitoring and forecasting generation. These systems help in the early detection of slippages and the identification of opportunities to resolve production loss-related issues. A central monitoring facility (CMF), for instance, facilitates data from various OEM equipment being brought onto a single platform, which enables easier and real-time monitoring of wind and solar assets. The continuously updated data can be analysed to avoid operational challenges and improve output.

Challenges in the adoption of clean technologies and how to address them
The implementation of each of these technologies comes with its own set of challenges, including, but not limited to, high capital investment, concerns over the regulatory environment, a lack of skills to operate the technologies in the best possible manner, sourcing challenges, space constraints on a few occasions, and uncertainty about the outcomes.

It is thus clear that employing these technologies calls for a fair amount of groundwork, mostly in terms of creating organisation-wide awareness, building capacity, and aligning operational teams with the new, “greener” way of going about their work.

Looking ahead, Carbon Capture Utilisation and Storage (CCUS) technologies might come into play at some point, particularly for thermal power plants, but it will have to be an industry-wide movement to be feasible.

As of today, the upscaling of such technologies, the investments they entail, and the lack of clear policies on this front all present a challenge. Such ifs and buts notwithstanding, India’s power sector is certainly moving in the right direction, towards greener operations and cleaner energy for all. We should continue to be guided by the long-term vision, avoid knee-jerk reactions, and take gradual steps towards our nationally determined goals with clearly defined milestones and targets along the way.