CEA stresses on large scale grid integration of renewables

Taking into consideration the significant increase in the country’s wind and solar power generation during the last few years and also the government’s growing focus on green energy, the Central Electricity Authority last month released a report on large scale grid integration of Renewable Energy Sources.

Generation from RES in India is concentrated in a few states. According to the CEA, such generation cannot be termed ‘marginal generation’ and the variability factor requires serious thought.

The report by the CEA emphasises the need to facilitate large scale integration of variable RES in the interest of grid security. It however points out that with the country moving towards a tighter frequency band, balancing the variable RES is going to be more challenging.

Generation from renewable energy primarily depends on nature. In case of wind power, the determining factor is wind velocity. Solar power is dependent on sunshine.

The issue of variability in generation from RES can be addressed through improved forecasting techniques. Such techniques are at present evolving. As the share of power generated from RES increases, accurate forecasting of the output will assume more significance.

The CEA report lays stress on balancing the variable output of power generated from RES located in the few states through integration into the all India grid.

Currently, the country’s inter-state and inter-regional transmission infrastructure is being developed. It is expected that the five electrical regions are going to be synchronously connected in 2014. However, new transmission corridors will be required for evacuating green energy from states such as Tamil Nadu, Gujarat, Rajasthan and Jammu and Kashmir (Ladakh).

Taking into account the short gestation period of renewable energy plants, transmission planners in the country recognise that transmission has to lead generation and will require upfront investment. Accordingly, plans for transmission corridors required in the next five years have been firmed up and their implementation is underway.

As on August 31, 2013, the country’s total installed capacity stood at 2,27,357 MW. Of this, RES constituted 12.4 per cent or 28,184 MW. During 2012-13, the generation from RES was around 47 billion units constituting 5 per cent of the total all India generation of 959 billion units.

The CEA report points out that the country’s RES capacity is concentrated in five states — Rajasthan, Gujarat, Maharashtra, Karnataka and Tamil Nadu. Out of the five states, in Gujarat, Tamil Nadu and Rajasthan, the percentage of RES capacity in the total installed capacity is substantial. While in Gujarat it is 18 per cent, the RES capacity in Tamil Nadu and Rajasthan stands at 40.2 per cent and 26 per cent respectively. In all five states, the RES are predominantly wind and solar.

Gujarat, Tamil Nadu and Rajasthan together have 70 per cent of the country’s total wind generation capacity (18,500 MW). In solar, the three states lead with 91 per cent of the total capacity (1,500 MW).

The 12th Five-Year Plan envisages a capacity addition of 88,537 MW from conventional generation. An assessment made by the CEA reveals that a RES capacity addition of 32,000 MW is likely in the eight states of Tamil Nadu, Andhra Pradesh, Karnataka, Gujarat, Maharashtra, Himachal Pradesh, Jammu and Kashmir and Rajasthan during the 12th Plan period. Out of the planned 32,000 MW RES capacity addition, approximately 30,000 MW will come from wind and solar, the CEA estimates.

States deploy different methods to manage the variations in generation from RES. Tamil Nadu, for example, resorts to cutting down generation in the old coal-based power plants. Gujarat keeps a margin in its thermal and hydro generation to manage the variations of wind and solar generation. Rajasthan uses its coal and lignite based generating plants to balance the wind variability by reducing to the extent that they do not need oil support for steady flame in the boiler. The two gas-based stations in the state, Ramgarh (113 MW) and Dholpur (330 MW) are also used for balancing.

The CEA report highlights the importance of adopting accurate forecasting techniques with regard to generation from RES so as to ensure protection of the grid. It calls upon each state to assess its balancing capacity before entering into renewable energy purchase obligations, further adding that the respective buyer state of renewable energy should be responsible for maintaining its load-generation balance taking into account the revised forecasts of the renewable energy portfolios.

The report also suggests setting up of real time markets to provide a platform for selling surplus power or buying power when in deficit, technical and regulatory measures for enhancing the flexibility of conventional generation so as to increase the balancing capacity of the grid, establishment of Renewable Energy Management Centers equipped with advanced forecasting tools, smart dispatching solutions and real time monitoring of renewable energy generation, setting up of wind farms through competitive bidding to reduce tariff, regular monitoring of grid protection schemes, international cooperation for developing REMCs in renewable rich states, balancing capabilities using indigenous sources of conventional power, optimum development of enabling transmission infrastructure and capacity building of grid operators.

The report titled ‘Large Scale Grid Integration of RES – Way Forward’ by the CEA is based on inputs furnished by the states of Gujarat, Tamil Nadu and Rajasthan.