India’s power grid gears up for 21 June solar eclipse

New Delhi: With the solar eclipse scheduled for 21 June, India's electricity grid operators are preparing to manage the shock due to the sudden drop and surge in generation that the national grid would experience when the celestial event occurs.

To balance the upheaval, India’s hydropower stations are expected to play a key role as they provide the flexibility of a quick generation ramp up and down as they take the least time to switch on or off. This was evident on 5 April, when India pulled off a feat in electricity grid management during a 9-minute blackout, called for by Prime Minister Narendra Modi.

An annular solar eclipse occurs when the moon comes between the sun and the earth but doesn't cover the former completely, leaving the sun's visible outer edges to appear as a ‘ring of fire’. This leads to a drop in solar irradiance which impacts power generation. The expected drop in generation is expected to be around 11,943 mega watt (MW) on 21 June.

Eclipses occur every year, but annular solar eclipses are not common. India has experienced three solar eclipses in the past ten years—on 22 July 2009, 15 January 2010 and 26 December 2019.

"We need to prepare for low probability and high impact events such as this pandemic, cyber attacks, cyclones such as Amphan and now Nisarga, among others," said S.R. Narasimhan, director, system operation at state-owned Power System Operation Corp Ltd (Posoco) that oversees India’s critical electricity load management functions.

The eclipse this year also comes in the backdrop of the lockdown which has led to a drastic fall in pollution, thereby improving solar radiation. Apart from preparing for astronomical and weather factors, Posoco is also trying to factor in consumption pattern that could impact power demand.

A report by Posoco on 21 June solar eclipse, reviewed by Mint, said, “Electricity grids with such a significant penetration of solar capacity will be adversely impacted by astronomical events such as solar eclipse, due to variation in solar generation (reduction followed by rise in generation) and associated large ramp rates.”

India has 34.6 gigawatts (GW) of solar power, with an aim of having 100 GW of solar energy capacity by 2022. It is also one of the largest interconnected power grid, capable of transferring 99,000 MW of electricity from any corner of the country. It is also connected with Bangladesh, Nepal and Bhutan.

"Since August last year our teams have started looking at data sets pertaining to the eclipse from the IMD (India Meteorological Department) and ISRO (Indian Space Research Organisation),” said Narasimhan.

Any sudden change in demand pattern will impact the grid frequency. Global standards require that grid frequency be kept close to 50 hertz (Hz). India’s grid code calls for grid frequency to be between 49.5 Hz and 50.2 Hz. This will require close coordination between the grid operators and power project generators across coal, gas, hydro, nuclear and green energy sources run by the Centre, states and the private sector.

“It is expected that all India average demand may reduce by 2%-2.5% with instantaneous maximum reduction of 3%-3.5% and after eclipse it may increase by the same amount,” the report said.

“The eclipse pales in comparison to reduction in demand as compared to 5th April lights out. We saw a significant reduction in demand during the last annular solar eclipse that surprised us a bit,” said Narasimhan.

Along with the National Load Despatch Centre (NLDC) and state load despatch centres (SLDCs), the preparations being made also need to keep in mind that June is a monsoon month.

“It is also dependent on weather. As we move towards a high hydropower period, there wouldn’t be much flexibility. However, we have sufficient hydropower even for this,” Narasimhan added.

While extending the world’ severest lockdown in containment areas till June end, the government has considerably eased off restrictions in other parts of the country to restart the economy. Consequently, India’s power demand that had nosedived is slowly getting back to pre-lockdown levels.

“Based on previous solar eclipse event occurrences in India, it is expected that during eclipse on 21st June 2020, there would be depression in demand due to human behaviour. However, due to ongoing countrywide lockdown, due to covid-19, the reduction and increase in demand could be less compared to previous eclipses because temples, malls are closed and small commercial shops are either closed or opening on alternate days,” the report added.

India’s peak demand in FY19 was 168.74 GW and touched a record high of 183 GW in May last year. The country has an installed power-generation capacity of 370 GW.