New Delhi: India can produce a glut of solar power in the afternoon and still struggle to meet electricity demand after sunset. The problem is not always a shortage of generation. It is that electricity is being produced when it is available, not necessarily when people need it.
That is the gap energy storage is meant to fill.
On 4 November, the Union Cabinet approved Rs 14,500 crore in financial support for a scheme to develop 92 gigawatt-hours of grid-scale energy storage capacity by 2030-31. The programme is expected to support an estimated investment of Rs 97,600 crore and includes batteries, pumped-storage hydropower and emerging technologies.
The push comes as India expands its solar and wind capacity. But generating more renewable electricity is only part of the challenge. The grid also needs a way to hold on to surplus power and release it when generation falls or demand rises.
Why can’t the grid simply use electricity as it is produced?
Electricity supply and demand have to remain balanced almost constantly. Homes, offices, factories and transport systems draw power throughout the day, but consumption does not follow the same pattern as renewable generation.
Solar power, for instance, rises after sunrise, peaks around the middle of the day and falls towards evening. Yet household demand often climbs when people return home, switch on lights, fans and appliances, and begin cooking.
Wind power is less predictable still. It depends on weather conditions, which can change over hours or even minutes.
When renewable generation exceeds demand, some electricity can go unused or be curtailed. When generation drops but demand remains high, grid operators must rely on other power sources, including coal and gas plants, or draw electricity from elsewhere.
Storage helps bridge that mismatch. It takes in electricity when supply is plentiful and releases it when the grid needs it.
How do batteries store electricity?
A grid-scale battery works on the same basic principle as the battery in a phone, although it is built on a much larger scale.
When there is surplus electricity, it is used to charge the battery through an electrochemical process. When demand rises or renewable generation falls, the battery discharges and sends electricity back into the grid.
These systems can respond quickly, making them useful for balancing sudden changes in supply and demand, managing peak loads and stabilising the grid.
They are not designed to power the entire country for days on end. Their usefulness depends on how much energy they can store and how long they can release it. Batteries are particularly suited to short-duration storage and rapid grid support.
What is a water battery?
India’s new scheme also backs pumped-storage hydropower, which uses two reservoirs at different heights.
When electricity is available in excess, pumps move water from a lower reservoir to an upper one. The water is effectively storing energy because it can later flow downhill through turbines to generate electricity.
It is a little like charging a battery by lifting water uphill and discharging it by letting the water fall.
Unlike many battery systems, pumped-storage projects can hold large amounts of energy for longer periods. But they need suitable terrain, significant construction and careful assessment of environmental and water-related impacts.
The Cabinet scheme supports 60 GWh of pumped-storage capacity, 30 GWh of battery storage and 2 GWh from emerging technologies.
Can storage make renewable power reliable?
It can help, but it is not a complete solution on its own. Batteries and pumped storage must be supported by transmission lines, better forecasting, flexible power plants and a grid capable of moving electricity to where it is needed.
The government estimates that India will require 411 GWh of grid-scale storage capacity by 2031-32. The new scheme is intended to help meet that requirement, while also encouraging domestic manufacturing. Battery projects receiving support will have to meet a minimum 40 per cent domestic-content requirement.
The larger challenge is clear: building solar and wind farms can increase the amount of clean electricity India generates. But unless the country can store and move that power, a significant part of its potential will remain untapped.