In the Indian power sector, a substantial increase in renewable energy capacity has been planned, which would significantly alter the energy mix and the energy market scenario in the country. The rapid increase in renewable power capacity is expected to create a more volatile residual load due to its fluctuating nature. To balance the variable electricity supply from renewable energy sources, coal-fired power plants need to be more flexible with the ability to frequently start up, meet major and rapid load changes, and perform frequency control duties, making them reliable power sources for safe and stable operation of the grid.
The government is, therefore, working on policy initiatives that promote grid stability. In February 2023, the Central Electricity Authority (CEA) notified the regulations for flexible operation of coal-based thermal power generating units aimed at enhancing the flexibility of thermal plants. The CEA had earlier issued the draft guidelines in July 2022.
As per these guidelines, the appropriate load despatch centres will schedule all coal-based thermal power plants up to a minimum power level (MPL) of 55 per cent. Further, the appropriate load despatch centres may schedule all coal-based thermal power plants up to the MPL of 40 per cent to support the operation of must run stations. The regulations also stipulate a minimum rate of loading or unloading of 5 per cent per minute for supercritical and ultra-super critical units.
A look at the key highlights of these regulations…
Major highlights of the regulations
The regulations will apply to all coal-based thermal power generating units owned or under control of the central government or state governments or owned by any private company, connected with the grid and to load despatch centres.
As a general requirement according to the draft, the coal-based thermal power generating units need to be designed or suitably retrofitted to comply with these regulations for a full range of ambient and environmental conditions prevailing at the site.
All plant equipment and systems will need to comply with the provisions of statutes, regulations and safety codes, as applicable.
- Flexible operation: The regulation states that the implementation of flexible operation will be as per the phasing plan specified by the authority. All load despatch centres will schedule the coal-based thermal power generating units under their jurisdiction on the basis of their flexible operation capabilities as specified in the regulations.
- MPL: The coal-based thermal power generating units will have flexible operation capability with an MPL of 40 per cent. The generating units that are not capable of achieving an MPL of 55 per cent will achieve the same within one year of the notification of the regulations. Further, the generating units that are not capable of achieving an MPL of 40 per cent will achieve the same as per the phasing plan.
- Ramp rates capabilities: The coal-based thermal power generating units will have a ramp rate capability of minimum 3 per cent per minute for operation between 70 per cent and 100 per cent of the maximum continuous power rating. For operation between 55 per cent and 70 per cent of the maximum continuous power rating, the units will have a ramp rate capability of 2 per cent. The generating units will have to comply with this regulation within one year of the notification of the regulations.
In addition, coal-based thermal power generating units will achieve a ramp rate capability of minimum 1 per cent per minute for operation between 40 per cent and 55 per cent of maximum continuous power rating as per the phasing plan.
Conclusion
While the flexible operation of existing coal-based power plants has been identified as a promising measure for balancing the fluctuating renewable power, there are a few concerns raised by the industry.
One of the issues is the financial feasibility of upgrading/renovating old plants/ small size units to make them more flexible. Several aspects need to be addressed at the policy and regulatory levels, including the recovery of expenditure involved such as capital expenditure and operating expenses in line with lower technical minimum, recovery of loss of residual life and implementation timelines. The necessary shutdown periods and the recovery of fixed costs during the shutdown period must also be adequately considered.
Despite these concerns, it is expected that the notified regulation will allow coal-based power plants to adjust the net power fed into the grid.
Akanksha Chandrakar
