Leveraging Battery Energy Storage in Thermal Power Plants for Enhanced Flexibility, Reliability, and Emergency Backup

Power, the backbone of India’s energy system—accounting for around 48% of installed capacity and over 70% of total electricity generation—bears primary responsibility of managing these challenges. Thermal plants are required to operate at low loads during solar hours and ramp frequently leading to efficiency loss, higher emissions, equipment stress and increased maintenance. These challenges are particularly pronounced in the Indian context due to fuel characteristics and seasonal demand patterns. Indian coal typically has a high ash content in the range of 45–50%, which adversely affects combustion stability at low loads. Operational experience indicates that operation below 55% Technical Minimum Load (TML) significantly increases the risk of flame instability and flame failure, leading to boiler trips and forced outages. This risk is further aggravated during winter months, when system demand reduces and thermal units are required to sustain prolonged low-load operation. Consequently, deep turndown and frequent cycling pose higher operational and reliability risks for Indian coalbased power plants.

Integrating Energy Storage Systems (ESS) with thermal power plants presents a practical pathway to address these challenges while enhancing flexibility, grid stability and asset utilization. Considering the 2–4-hour storage requirement and the technical maturity of BESS,

NTPC, India's largest integrated power utility, has carried out a study focusing on BESS integration with thermal plants. BESS can help avoid low load operation, reduce frequent cycling, provide faster ramping support, shift energy to evening peaks and enable optimum utilization of existing thermal generation and transmission infrastructure. In the present context,

BESS can utilize Un-Requisitioned Surplus Power of thermal power plants for charging during solar and night hours, while in the future it can support operation at or above Technical

Minimum Load (TML), preventing backing down or reserve shutdown conditions. The energy stored during solar/night hours in BESS can be discharged for meeting the peak requirements of the grid. This peak discharge can defer new thermal capacity being setup only for peak requirements. The paper presents NTPC’s techno-economic studies on BESS integration with thermal power plants, covering sizing, configuration, integration schemes, operational impacts, economic performance, and tariff implications. The results show that BESS deployed under the

Add-Cap (Additional Capitalization) framework delivers competitive peak power with minimal impact on station tariff, while improving efficiency, emissions, availability, and system flexibility. The study also examines the use of a small, reserved Depth of Discharge (≈5% of

BESS capacity planned for flexibilization), required for maintaining for battery health, to provide emergency backup in thermal plants and office complexes without compromising the primary operational role of BESS. NTPC ongoing pilots for these multi-use applications provide practical insights and a model for scalable deployment.

In conclusion, BESS can transform thermal power plants from base-load generators into flexible, multi-functional assets that support renewable integration, enhance grid stability and offer a cost-effective pathway for system resilience and sustainable energy future. The studies done by NTPC and ongoing pilots provide a practical future ready framework for India and other countries facing similar operational challenges.