Thermal power is one of the most energy-intensive industries in the country. It is estimated that a conventional power plant consumes up to 7 per cent of its own electrical energy to operate its systems. For a 1,000 MW thermal power plant (TPP), this translates to 70 MW of power that is generated but is not transmitted to the grid. The adoption of energy efficiency practices can help gencos reduce this power drain from TPPs.
The Ministry of Power’s (MoP) Perform, Achieve and Trade (PAT) scheme, launched in 2008, takes into account the energy efficiency potential of TPPs and has so far notified energy consumption targets for over 350 TPPs under four PAT cycles.
Under PAT cycle I (2012-15), 144 designated consumers (DCs) were covered in the TPP segment. With the threshold of 30,000 tonnes of oil equivalent (toe) of energy consumption, over 88 per cent of the country’s installed thermal power generating capacity (as of 2011) was covered. The total reported energy consumption of these DCs is about 104 million tonnes of oil equivalent (mtoe). At the end of the first cycle, TPPs achieved energy savings of 3.06 mtoe against a target of 3.21 mtoe, which was a shortfall of 5 per cent. In addition, about 13 mt) of carbon dioxide (CO2) emissions were also reduced.
In PAT cycles II, III and IV, 208 DCs from the TPP segment are undertaking the implementation of energy efficiency projects to achieve the assigned targets. PAT II covers 154 DCs with a savings target of 3.13 mtoe, PAT III covers 37 DCs, with a savings target of 0.4 mtoe, and PAT IV covers 17 DCs with a target of 0.237 mtoe.
TPPs are also undertaking energy efficiency improvements under the MoP’s renovation and modernisation (R&M) programme. The World Bank has financed the Coal-Fired Generation Rehabilitation Project for demonstrating energy efficiency R&M at coal-fired generating units aggregating to 420 MW by providing a $180 million loan and $37.9 million grant. West Bengal Power Development Corporation Limited’s (WBPDCL) Bandel TPS Unit 5 (210 MW) and Maharashtra State Power Generation Company Limited’s Koradi TPS Unit-6 (210 MW) were covered under the project. Haryana Power Generation Corporation Limited’s Panipat TPS Units-3 and 4 of capacity 110 MW each were proposed to be covered initially, but the utility later decided not to proceed with R&M citing financial viability concerns.
After the rehabilitation of WBPDCL’s Bandel unit, the life of the plant was extended by 15 years, the boiler was redesigned to burn coal of calorific value 3,300 kCal per kg against 4,500 kCal per kg earlier, the capacity of the unit increased to 215 MW, unit heat rate improved from 2,872 kCal per kWh to 2,345 kCal per kWh, auxiliary consumption reduced from 10.9 per cent to 9 per cent, and particulate emission in flue gases reduced to 74.5 milligram per normal cubic metre (mg per Nm3).
MSPGCL planned to achieve full load of the Koradi unit after energy efficiency R&M in May 2016. However, this was achieved only in October 2018. Though the unit experienced teething problems, the issues have now been resolved. The performance guarantee tests were successfully completed in April 2019 and as per the initial data, significant improvement has been observed in various operational parameters.
Energy savings in TPPs can be realised through simple measures with a short payback period such as switching to LED lamps, installation of variable frequency drives, and stage reduction in pumps as needed. Advanced technologies such as the installation of waste heat recovery systems and vapour absorption machines can further help in achieving greater energy savings by making the plant’s own major electricity consumption elements more efficient. Further, engine performance upgrades by deploying the latest turbochargers can provide higher pressure ratio capability, advanced valve timing, improved engine efficiency, optimised combustion and reduction in exhaust gas emissions.
Another critical area to improve energy efficiency in a power plant is its fuel system. The quality of fuel and proper upkeep of the fuel injection system can go a long way in ensuring energy savings. For instance, use of washed coal and dynamic coal flow balancing can help in combustion optimisation.
Further, with the use of well-planned data-driven solutions, TPPs can be operated more efficiently. The implementation of energy management systems is crucial as it helps to digitally monitor, control and optimise generation performance.
The way forward
Going forward, as the country moves to diversify its energy mix by including more renewables to reduce carbon emissions, gencos need to do their bit by ensuring optimum efficiency of their TPPs. The emissions from the Indian electricity sector have increased at a compound annual growth rate of 5.7 per cent from 727 million tonnes of CO2 (mtCO2) in 2013-14 to 961 mtCO2 in 2018-19. By implementing energy efficiency measures, the fuel wasted in generating energy can be saved, thereby curbing emissions in the long run.