Delhi Coal plant flexibility workshop – timely training for a challenged sector

Following our first workshop last week in Hyderabad, we ventured to Delhi to deliver the coal power plant flexibility toolkit training to even more utility operators on 20-23 June. Despite a local train strike, attendance in Delhi was even higher than in Hyderabad and the exchanges even livelier.

By Dr Lesley Sloss, Mr Stephen Storm (EPRI) and Mehul Tatia (CII)

Over the two workshops, we have delivered training to more than 170 delegates representing the majority of utilities, including NTPC, Adani Power, Tata Power, JSW Energy, Reliance Power, MAHAGENCO and Shree Cement. Together, these plants contribute to more than 40 GW coal-fired capacity in India.

As we move through this training exercise, it is becoming clear that the majority of Indian coal plants face the same technical challenges concerning increasing their flexibility. India intends to have up to 500 GW of variable renewable energy (VRE) by 2030.

With cost-effective energy storage a long way off and without any national option for peaking gas plants, coal powerplants are the only real option for India to maintain the dispatchable capacity to meet demand. But, as the country’s  new coal build also slows, there is an increased reliance on older subcritical plants, burning low-grade, high ash coals.

The current minimum technical load for Indian coal plants is 55%, but the Government of India is proposing to force this down to 40% within the next six months. At the same time, two-shifting (starting up and shutting down within a 24-hour period) will also be expected. This adds a significant strain to plants designed to burn at baseload and will inevitably lead to increased damage and lower efficiency of the coal fleet.

Through interaction with the delegates, Stephen Storm identified four key areas for Indian coal plants to consider if they are to achieve their flexibility goals.

Emissions:

• Growth of VRE is positive for the environment but increases the demand on conventional units to operate flexibly.
• More stringent air pollution control regulations and operating loads can result in lower thermal efficiencies and thus higher emissions.
• If units become less reliable, the results can be increased blackouts, decreased overall fleet efficiency, and they risk derogation from air pollution regulations. Thus, strategies for emissions reduction MUST consider flexibility and cost.
• If emissions monitoring systems are not measured or maintained properly, accuracy will be challenged. Uncertainties for NOx/SOx/Hg were observed during one of our site visits, validating the need for improvements in process, certification, and regulations. This will be addressed in our upcoming workshops on Continuous Emissions Monitors(CEMs) in Bhubaneswar and Bhopal.
• During our visits to the Ramagundan and Dadri coal-fired power plants, we observed innovative projects for heat recovery from the flue gas, solar heating of water being used by steam generators and even floating solar farms that operate with increased efficiencies and help keep thermal plant water supplies cooler yielding some improvement in efficiency. It is therefore clear that many Indian plants are setting new standards in terms of innovation in clean energy.

Generation cost

• Indian power plants operate with constrained budgets due to higher fixed costs with lower generation demand.
• Investment in performance upgrades and emissions retrofits may be required to meet the new demands for flexible operations.
• To achieve flexibility, market changes may be needed to ensure revenue for plants operating in support of the system. Additional market mechanisms such as capacity payments and ancillary services arrangements may help the market adapt to ensure sufficient capacity is always available to stabilise the grid.
• Optimising efficiency, deploying defence strategies, and applying fuel flexibility will be critical if the energy market does not incentivise flexibility and capacity.
• During this two week event, we learned that some stations have transportation costs within India that outweigh the cost of fuel. Thus, the challenges of flexible operations are even greater for units which are in geographically unfavourable locations for the supply of coal.
• The degree to which overall plant heat rate is affected by part-load operation depends on the part-load efficiencies of the individual system components as well as the type of fuel selected for use. Plant heat rate can vary significantly between full and low load. Thus, to interpret a plant’s thermal efficiency and evaluate the heat losses, you must have an accurate measurement of both turbine cycle heat rate and boiler efficiency to understand where the losses originate and to validate the potential for improvement when implemented. Continued focus in this area in India is vital.