January 2020 marked a significant milestone. Both for India’s renewable power ambitions and for two of the country’s largest clean energy producers, Gurugram-based ReNew Power and Hyderabad-based Greenko Energies.

The two companies  won won The Economic Times Greenko, ReNew win world’s largest renewable-cum-storage tender Read more wind-and-solar energy projects floated by the Solar Energy Corporation of India (SECI)—ReNew was given 300 megawatt of projects; Greenko, 900 MW. The tenders were awarded on the condition that they supply power for at least six hours every day to meet peak demand in the mornings and evenings. SECI is in the process of selling the power to distribution companies.

The novelty here? The tender called not just for supply of electricity, but also storage—a key requirement for solar and wind power plants if they are to supply power during periods of high demand.

Now, there are several ways to store renewable power. The most prominent is pumped-storage hydropower pumped-storage hydropower Pumped-storage hydropower In PSH, water is pumped from a lower reservoir to an upper reservoir using cheap power from the grid during periods of low demand. And when the demand goes up, the water is released from the upper reservoir and power is generated using hydroelectric turbines. (PSH), a decades-old technology that accounts for 95% of all global electricity storage, according to the Institute for Energy Economics and Financial Analysis (IEEFA).

There are other storage technologies aside from PSH: flywheel energy storage, compressed-air energy storage, flow batteries, etc. However, it is the lithium-ion (Li-ion) battery that has emerged as the most popular and most promising for new projects. These batteries—also used in electric vehicles—are promising primarily because their average price has plunged 87% between 2010 and 2019 to $156 per kilowatt-hour kilowatt-hour Kilowatt-hour Unit of energy storage in a battery. (kWh), according to Bloomberg New Energy Finance (BNEF).

ReNew’s project, with its minimum storage of 150 megawatt-hours megawatt-hours Megwatt-hours Unit of energy storage in a battery. 1 MWh = 1,000 kWh. (MWh), will use this tech. It will be the first large-scale effort in India to use batteries to make clean power more reliable. Rival Greenko uses PSH, which faces issues with terrain and the availability of water.

A project such as this will be important to ReNew’s next phase of growth.