Coal-based power plants account for around 75 per cent of India’s thermal power generation and a significant share of carbon emissions. According to the latest data from the Central Electricity Authority (CEA), carbon dioxide (CO2) emissions from grid-connected power stations stood at around 846.2 million tonnes (mt) in 2015-16, compared to 805.4 mt in 2014-15. Therefore, improving the energy efficiency of thermal power plants (TPPs) has become critical. A look at some of the key initiatives taken to increase TPP efficiency…
The biggest national initiative driving energy efficiency in TPPs has been the launch of the Perform, Achieve and Trade (PAT) scheme in 2012 by the Ministry of Power. The scheme covers eight energy-intensive sectors, including TPPs. In the first cycle of PAT (2012-13 to 2014-15), 144 TPPs were covered, accounting for nearly 88.6 per cent of India’s installed thermal power capacity (as of 2011). The cumulative savings achieved by these plants were 3.06 million tonnes of oil equivalent (mtoe) as against the target of 3.211 mtoe, a 5 per cent shortfall. A total of 13 mt of CO2 emissions were reduced by these plants.
Some of the key energy efficiency practices adopted by these plants have been the use of washed coal, dynamic coal balancing, and intelligent soot blowing systems, as well as the installation of waste heat recovery systems in gas-based plants and the deployment of vapour absorption machines. The second cycle of PAT commenced in April 2016 with an expanded scope in terms of the number of designated consumers (DCs) covered in the TPP segment. An additional 22 TPPs have been covered in this cycle.
Replacement of old and inefficient plants
Another key initiative taken by the government for promoting efficiency has been the replacement of power plants of more than 25 years with new supercritical units. In July 2016, the CEA undertook an exercise to identify old and inefficient plants that could be replaced with more efficient supercritical equipment. As per the CEA’s assessment, of the total installed capacity of 32,830 MW operating for more than 25 years (as of September 2015) in the central and state sectors combined, around 22,170 MW could continue operations for a significant period of time. The units in this category have either undergone renovation and modernisation (R&M)/life extension (LE) works or will undergo it.
A total capacity of 7.7 GW was identified for retirement and replacement with 18.5 GW of supercritical units. As of April 2017, 4.3 GW of capacity has been retired. Meanwhile, there are around 13 projects aggregating 6,608 MW of capacity in the state sector that will be replaced with new 660 MW and 800 MW units aggregating 16,580 MW. In addition, there are two central sector projects aggregating 1,130 MW which will be replaced with new 660 MW units of 1,980 MW capacity. The proposals for the new units are at various stages of evaluation. Further, the government has formulated a policy on the automatic transfer of coal linkage (granted to old plants) to new plants in case of scrapping of old units and replacing them with new higher efficiency supercritical units.
Under the National Mission on Clean Coal Technologies, a research and development project is being undertaken to indigenously develop advanced ultra supercritical (AUSC) technology. The Indira Gandhi Centre for Atomic Research, NTPC Limited and Bharat Heavy Electricals Limited have signed an MoU for the development of an 800 MW AUSC indigenous demonstration plant. The ultra supercritical boiler aims to achieve an efficiency improvement of about 10 per cent over supercritical units. Further, a 20 per cent reduction in CO2 emissions at source and 20 per cent savings in coal consumption compared to a subcritical plant and 11 per cent compared to a supercritical plant are the targets proposed under the project. The efficiency of TPPs is also being enhanced through regular R&M initiatives. For the period 2017-22, R&M and LE works for 70 units totalling 14,719 MW in the central and state sectors are being considered.
A significant development with regard to promoting energy efficiency in TPPs has been the revision of environmental norms in December 2015. The revised norms aim at reducing suspended particulate matter emissions to 0.98 kg per MWh, sulphur dioxide (SO2) to 7.3 kg per MWh and nitrogen dioxide (NO2) to 4.8 kg per MWh. The revised norms have for the first time introduced SO2, NO2 and mercury, and go beyond the particulate matter norms. Different techniques are available to control the emission of these pollutants. These regulations are expected to lay more emphasis on clean coal technology-based methods such as coal washing, wet scrubbers, flue gas desulphurisation systems, electrostatic precipitators, low-NOx burners, etc.
As per projections by NITI Aayog, coal-based power is expected to remain the mainstay of power generation for the next couple of decades. In the backdrop of the Paris climate summit and the international community’s increasing pressure on developing countries to shift to a low-carbon energy strategy, India, one of the world’s largest carbon emitters, needs to devise newer ways of improving the efficiency of its TPPs.