India’s energy mix has been rapidly changing with increasing renewable energy penetration in the grid. However, variability in renewable generation is unavoidable, which calls for flexible operations and cycling of thermal power plants (TPPs). Flexibilisation is the new paradigm in thermal power generation, which is aimed at handling the fluctuations in renewable supply by converting baseload stations into flexible generators.
Drivers for flexibilisation
The plant load factor (PLF) of thermal power stations has been continuously falling over the past decade. It has declined from 79 per cent in 2008 to 60 per cent in the current fiscal. This can be attributed to the demand-supply mismatch in the country and the substantial growth of renewable energy.
Energy demand has grown at a compound annual growth rate of 4 per cent over the past five years, while thermal capacity has grown at almost 11 per cent during this period, resulting in a demand-supply mismatch. Further, more than 8.5 GW of solar capacity has been added during the past two years. With the addition of 110 GW of wind and solar capacity as compared to around 65 GW of thermal power capacity by 2022, the PLF of TPPs is expected to fall below 47 per cent. Further, sliding solar tariffs are making coal uncompetitive. With solar tariff going below Rs 2.50 per unit, it is estimated that 60-85 GW of installed thermal capacity could face severe despatch risks.
An increasing number of power plants are expected to be despatched in the coming years. In order to stay competitive and achieve flexibilisation, baseload plants will be required to ramp up and shut down with greater frequency. In addition, they will have to operate on a lower technical minimum load, with shorter start-up time and more load cycles. In order to ensure that boiler operations can match the frequent ramping, optimum steam pressure and temperature will have to be maintained.
A number of utilities in the US and Europe have already initiated measures to improve the flexibility of TPPs. In the US, for instance, operational changes are being incorporated in power plant practices. On the other hand, utilities in Europe have opted for retrofits and modifications in plants. However, the key considerations when choosing between operational measures and retrofits are the design of the plant, the cost recovery mechanism and the useful life of the power plant. In most cases, a customised approach is required, which is a combination of capital retrofits and operational modifications.
Initiatives in India
Under the Indo-German Energy Forum flexibility roadmap, a task force has been set up in India headed by the director, operations, NTPC Limited. The task force is undertaking studies at two NTPC stations, namely, Simhadri and Dadri, to identify flexibilisation measures and carry out a cost-benefit analysis to determine their scale-up potential.
Meanwhile, Power System Operation Corporation Limited has carried out studies on the flexibility requirements of the Indian power system with a detailed analysis of the impact of renewables on thermal power generators in the country. Many international players such as Uniper and Steag have entered the Indian market to tap this opportunity and offer flexibilisation services.
Further, the Central Electricity Regulatory Commission has issued amendments to the Indian Electricity Grid Code regarding the technical minimum for thermal power stations. As per these, the technical minimum scheduled operation of a unit of an interstate generating station has been prescribed at 55 per cent of the unit’s installed capacity. The regulations specify that generators operating below 85 per cent of the installed capacity will be compensated in terms of the heat rate.
Challenges and the way forward
The flexibilisation of TPPs entails several challenges. It reduces the efficiency of plants and increases the risk of failures/trips due to frequent start-ups and shutdowns. Furthermore, it reduces the useful life of assets and increases the cost of operations. However, these challenges can be tackled with constant monitoring, analytics and automation. Utilities can develop an asset health index, adopt predictive analytics and implement customised dashboards to transform a looming operational risk into a competitive advantage.
Flexibility is a fundamental change for power plants. Utilities that fail to keep up with this trend may experience a loss in thermal efficiency and additional stress on their components. Utilities need to manage their assets through a least-cost option while responding to a changing market.
Based on a presentation by Rajesh Ivaturi, Partner, Energy Practice, Deloitte, at a recent Power Line conference