According to data by the Central Electricity Authority, the average emission rate of India’s coal-based power plants was close to 0.91 tonnes of CO2 per MWh in 2017-18. In absolute terms, the total emissions by the plants was 922.1 million tonnes (mt) of CO2 in 2017-18, compared to 727.3 mt in 2016-17. The thermal power plant (TPP) segment is, thus, trying to improve its efficiency through several initiatives with the Perform, Achieve and Trade (PAT) scheme being central to them. Notably, under PAT Cycle I, the thermal power segment as a whole contributed to meeting about 35 per cent of the overall target, which is the maximum contribution by any segment in the PAT cycle. A total of 13 mt of CO2 emissions was reduced by the segment. A closer look at the thermal power industry’s initiatives for improving energy efficiency…
Experience under PAT Cycle I
The TPP segment is one of the most energy intensive segments and also one of the eight segments that contributed to about 46 per cent of the total savings target under PAT Cycle I.
With the threshold of 30,000 tonnes of oil equivalent (toe) energy consumption, almost 88.6 per cent of the country’s installed thermal power generating capacity (as of 2011) was covered. The designated consumers in the thermal power segment were grouped under coal, gas and diesel. There were 144 designated consumers in the thermal power segment during the first cycle – 107 units are based on coal/lignite whereas those on gas and designated consumers constitute 33 and 4 respectively. The norms and standards were specified for the TPP segment, based on the deviations of the average net heat rate of three years (2007-10) from the designed net heat rate.
The TPP segment in PAT Cycle I achieved 3.06 mtoe against a target of 3.21 mtoe, which was a shortfall of 5 per cent from the assigned target. (It needs to be noted that the achievement of 3.06 mtoe relates to only 120 designated consumers, which carried out the monitoring and verification exercise and submitted the same to the Bureau of Energy Efficiency. These 120 designated consumers were given an energy reduction target of 2.58 mtoe. They have overachieved their target by 19 per cent.)
While most of the plants invested in the least payback period option of saving in auxiliary power consumption by changing to LED lamps, installation of variable frequency drives and stage reduction in pumps as per need, others realised the need for advanced technology. Some of the significant energy-efficient technologies and best practices adopted by the TPP segment’s designated consumers are the use of washed coal, dynamic coal balancing, intelligent soot blowing system, installation of waste heat recovery systems and steam turbines in gas-based plants as well as the installation of vapour absorption machines.
Future PAT cycles
At present, 208 designated consumers from the TPP segment under PAT Cycles II, III and IV are undertaking implementation of energy efficiency projects to achieve the assigned targets. PAT II covers 154 designated consumers with a savings target of 3.13 mtoe, PAT III covers 37, with a savings target of 0.4 mtoe, PAT IV covers 17 with a target of 0.237 mtoe.
Some key interventions that the TPPs are undertaking include the use of micro oil ignition system for improving the combustion efficiency and flame temperature, installation of dynamic classifiers for coal mills for improving coal throughput and fineness, installation of energy efficient electrical equipment, upgradation of cooling towers, installation of advanced rotary air preheaters and installation of online optimisation software.
Issues and concerns
That said, over the last few years, the thermal power segment has been facing a lot of issues. Low capacity utilisation, inconsistent quality and a lack of reliable availability of coal are the major impediments for meeting the targets. Further, recessionary trends are already putting a lot of pressure on the toplines and bottomlines of designated consumers. Also, decision-making by designated consumers is still based on “investment and payback” and not on “life cycle costing approach” leading to less efficient equipment.
Overall, energy security and CO2 emission reduction are two major concerns of the electricity system and the role of power plants in improving the efficiency would be critical to future energy security.