The relevance of pumped storage projects

• A policy for promoting pumped storage projects will be brought out for electricity storage and facilitating smooth integration of the growing share of renewable energy.

Pumped Storage

• India has planned to create an ambitious 500 GW of non-fossil power by 2030.
• In around two years, from 2021 to 2023, it created some 23 GW of non-fossil generation capacity.
• Out of 10 GW added in eight months in 2023-24, 7.5 GW were wind and solar, pointing to how renewables will account for most of the new power generation that will be added in India
• Actual renewable power generation has crossed 10% of the total generation and its share will only increase many times.
• Indian policies have laid down that all the power that renewable sources generate should be used and their curtailment should be the last priority.
• State-of-the-art forecasting techniques have helped to predict more accurately how much renewable power generation varies in the course of a day.
• This has helped grid operators plan in advance how to increase or decrease power generation from other sources to provide steady power to the consumer.
• Hydro power generation can quickly ramp up or ramp down in a matter of seconds. Hydro helped to ensure there were no blackouts during the lights-off campaign during the pandemic, for instance.
  • Gas turbines come next. Coal and nuclear need hours of notice.
• Among energy storage methods thought of were scaling up batteries and pumping in compressed air into large caverns and then drawing on them to generate power when required.
• But, much of the energy storage adopted across the world today is pumped storage that uses water. These are like super large batteries but natural and use water.

India’s experience

• India has 3.3 GW of pumped storage. Main ones are Nagarjunasagar, Kadana, Kadamparai, Panchet and Bhira.
• China leads the world with 44 GW of pumped storage supporting 1,300 GW of wind and solar.
• India would therefore need to ramp up its pumped storage capacity by several times if it wants to meet its renewable power generation targets.
• Pumped storage is of two types: on river and off river. On-river is like any hydroelectric project supplied by a river.
  • Existing hydro projects could become pumped storage.
• Off-river projects are those that have two reservoirs at two different levels to which the water is pumped up or falls down to under gravity in a closed loop.
• Abandoned mines can, for instance, be converted to such reservoirs.

How Kadamparai operates

• In Tamil Nadu, at noon on a typical day in July, wind and solar can generate half of all power. This is among the highest in the country.
• But that power dwindles as the day progresses and drops to zero when the sun sets. Wind has its own vagaries too. The wind season is May-September.
• Tamil Nadu has peaks of around 17,000 MW to 20,000 MW on a daily basis.
• The Kadamparai plant near Valparai in Coimbatore district came up some 37 years ago before wind and solar of any scale was there.
• The purpose was to help balance the grid and the plan has come in handy when Tamil Nadu took the lead in renewable power generation.
• The same unit can function as a pump consuming electric power when it pumps water from lower to higher reservoir.
• When the Kadamparai plant is operating as a pump to store energy, it would need about an hour and half to switch to generating mode.
• When stopped, it would need about half hour to start and generating at full load.
• When solar generation stops and the evening peak load begins after 6pm, Kadamparai plant becomes a generator.
• Hydro can be quickly turned on if there is a sudden drop in power generation, such as in the case of an outage. Barring water for irrigation and drinking, hydro is used for power generation when demand peaks.