Power ministry panel offers tips to contain damage to thermal plants

It proposed ramping down to MTL and minimum load operation during solar hours and ramping up in the evening when solar generation declines

Finding that frequently ramping up or down electricity generation in high magnitude, and not minimum technical levels (MTL), causes wear and tear in coal-based power plants, a committee formed by the power ministry has recommended that plants operating at low loads should avoid this, with duties on this shared among all fitting units to balance operational stress.

 

The committee was formed by the Central Electricity Authority (CEA) to examine the potential damage to thermal power plants on account of flexible operations and also to examine the impact of two-shift operations in generating units.

 

The committee recommended: “Avoid consecutive ramp-up and ramp-down of the same units or plants; instead, select a group of units for ramp-up and another group of units for ramp-down.” It added that ramping schedules should be rotated among a pool of units or plants rather than assigned strictly according to the “Merit Order” to alleviate the stress exposure of individual thermal power plants and share the burden among a larger pool of units.

 

It proposed ramping down to MTL and minimum load operations during solar hours and ramping up in the evening when solar generation declined.

 

“The Merit Order Despatch (MOD) may be reviewed, if necessary, to adopt the above recommendations. This will reduce the O&M costs of power plants and extend their operational life,” the committee noted.

 

The panel also proposed introducing “ramping” and “stable-load” blocks to give thermal plants the time to gradually change and stabilise generation, reducing the cost of operation & maintenance (O&M) and extending their operational life.

 

Moreover, instead of using the thermal fleet for fine grid balancing, the same may be done from other sources, such as hydro power plants, gas power plants, pump storage plants, and battery energy storage system (BESS), the report added.

 

Last year, NTPC had expressed concern over two-shift operations and 40 per cent load flexing.

 

It had said that operating units below MTL was not feasible owing to issues such as the poor quality of coal and that it was experiencing high boiler tube leakages, frequent flame failures, and a significant increase in failures of generators and turbines over the past three years.

 

It also mentioned that repeated ramping up and ramping down were accelerating wear and reducing the lifespan of thermal units.

 

Speaking at the Bharat Electricity Summit in March, NTPC Chairman Gurdeep Singh had said: “If this continues, we may eventually be forced to take some of these machines out of operation, which would be counterproductive.”

 

Highlighting the need to consider alternatives, he said: “This could include developing plants specifically designed for flexibility, such as subcritical units that can be ramped up and down or started and stopped daily.”

 

The CEA committee also said that the existing compensation mechanism of the Central Electricity Regulatory Commission (CERC) should be expanded to cover the O&M cost of up to 5 per cent, along with compensation for auxiliary power, heat-rate and oil-consumption degradation.

 

A major recommendation is to enable two-shift operation by 2030 of 151 old coal-based units, totalling 34.5 Gw and aged 35 years or more, after a feasibility study. The CEA estimates this could extend their operating life by 12-15 years and provide the equivalent of about 27 Gw of storage capacity to the grid.

 

For fine grid balancing sufficient battery storage at certain specific locations may be installed, the recommendations said. Required changes in the regulatory framework can be made to implement the recommendations.

Additionally, the CEA has initiated a pilot study and data analysis at Tamil Nadu’s 5x210 Mw Tuticorin Thermal Power Station, and recommended further study at the 210 MW Wanakbori plant in Gujarat and the 2x67.5 MW Southern station in Kolkata.

 

“Conducting a pilot study is indispensable for assessing wear and tear impacts, determining appropriate compensation mechanisms, and addressing operational concerns in a structured manner. The initiation of the pilot at the earliest is critical to enable implementation of two-shift operations on selected units within the next two years, in line with evolving grid requirements,” the committee noted.

 

On the CERC’s directions, the National Load Despatch Centre identified candidate units and requested confirmation of unit readiness for two-shift operations. However, NTPC sought exemption from participation in the proposed pilot study, citing technical and operational constraints, reliability concerns, and comparatively high efficiency and environmental performance of its units.

 

The report also noted NTPC’s reluctance had hindered progress on examination of feasibility, empirical validation of damage mechanisms, delayed formulation of a regulatory compensation framework for two-shift operation.

 

The two-shift operation provides a low-cost alternative for integrating renewables compared to BESS. “The potential from two-shifting—acting as a virtual storage capacity of 27 GW—is about 34.5 GW, which can be developed for just ~30,200 crore to ~37,750 crore, whereas equivalent BESS capacity would cost approximately ~1,75,500 crores,” the report said.

 

The committee also recommended exemption from flue gas desulphurisation units for these old power plants, as they will operate to integrate green energy and stop generating during solar hours, thereby reducing their daily average emission of sulphur dioxide and others.

 

The increasing penetration of solar generation is leading to very low net demand during solar hours and a sharp rise in the evening, with the difference reaching about 82 Gw on certain days.