How power outages can be avoided when solar generation is erratic

During the December 26th solar eclipse, Karnataka's solar power generation dipped by 90% at one point. Given that even clouds can interrupt solar power generation, and given our increasing dependence on solar, how do we deal with this problem?

During the solar eclipse on December 26, the solar power generated in Karnataka dropped sharply for an hour. At the time, over 18% of the state’s power demand was being met through solar energy.

Currently, the Bangalore Metropolitan Area Zone (BMAZ) draws around 20% of the state’s energy. Given this, much of Bengaluru’s energy demand can potentially be accommodated by solar power alone (Bengaluru gets power from the same grid that supplies to the entire state).

With the commercial operation of the world’s largest solar park (2050 MW) at Pavagada in Tumkur district recently, Karnataka now has the highest capacity of solar plant installation (7174 MW) in the country. Overall, India plans to commission around 100 GW of solar power plants by 2022 and to step it up by 2030.

The solar eclipse episode points to the need for proper planning to ensure that electric generation, transmission and distribution utilities are prepared to handle fluctuations during unforeseen circumstances. Even sudden clouds over large solar plants can cause a dip in power in the grid, as happened during the eclipse.

This is a concern as the nation moves pro-actively towards solar generation. If managed inadequately, this can result in power cuts and even grid collapse, causing nation-wide power outage.

So, given our increasing dependence on solar power, how do we prepare for such eventualities?

Dip in power generation during eclipse

As per Karnataka State Load Dispatch Centre data, available in the public domain, the generation from solar plants dropped sharply for one hour from 8.30 am onwards, on the day of eclipse.

At 9.30 am, solar power generation was a mere 400 MW, as against 4,000 MW on normal days. Thereafter, from 9.30 am till 11 am, solar generation rose sharply. This is contrary to the usual pattern, of power generation increasing linearly from 7 am to 12 pm.

Change in demand patterns too

Similarly, there was also a change in the demand pattern. Instead of state demand peaking at 10 am as usual, there was significantly higher peak demand at 12 pm.

The peak demand in the state in December was around 11,000 MW, but during solar eclipse an unusually high demand of 12,847 MW was recorded. This, incidentally, is an all-time high in the recorded peak demand in the state.

The reasons for the record peak demand post-eclipse could be the increase in domestic consumption for water heating (for post-eclipse bath), and the use of irrigation pump-sets with farmers stepping out after the eclipse. (In Karnataka, about 37% of power is consumed by the agriculture sector.)

Similarly, the reduced demand in the morning could be due to change in human behaviour in rural areas during solar eclipse. Or due to pre-emptive load reduction by grid operators — through power cut for a few consumers — to balance the state demand with power generation available during the time of the eclipse.

Reserve Generation essential

Supplying uninterrupted power to consumers is a major challenge for grid operators in such circumstances – the deficit in supply would have to be met through existing conventional generation plants like thermal, hydro, and nuclear. Usually hydro generation plants, which can maximise their production in a short span of time (due to faster ramp rate) are used to compensate for the deficit. 

Although the state is blessed with a good number of hydro-generation plants (3,650 MW) to handle such situations, even this would not be enough to compensate for the shortfall in solar generation during eclipse and similar events.

As we march relentlessly towards a renewable future, we need to look at a sizeable and flexible reserve generation capacity, with faster ramp rate systems like hydro-generation and battery storage, to handle the variation in power generation due to solar energy intermittency.

The availability of a transmission network that would allow for the transfer of power from power-surplus regions to the affected regions during such instances, is also important. This can be done only if a thorough transmission-planning analysis is carried out while integrating solar power into the grid.

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