The Evening Is Hard: How Rails, Coal and Batteries Meet in the Power System

Introduction: Two Shifts in India's Grid

India's electricity system has two shifts. During the day, solar output is large and, as the Centre for Research on Energy and Clean Air (CREA) reported, the daily peak fell within solar hours on 62 of the 92 days of July to September. In the evening, when the sun has set and demand remains high, the system leans on coal, hydro, gas, nuclear and, increasingly, batteries. This piece connects the figures for each shift to the railway data on coal movement.

The Day Shift and the Evening Shift

The day shift: CREA reported that solar generation grew 39% on the year, that solar set a daily record of 705 million units on 30 September, and that installed solar reached 168 GW. It also reported that about 1,835 million units of renewable output were curtailed in July and August, 1,462 million of it solar. Curtailment means output that was available but not used. It is a small share of the quarter's total non-hydro renewable generation of 101 billion units, by our rough arithmetic under 2%, though the periods differ, so the comparison is indicative only.

The evening shift: Coal and lignite generated 351 billion units in the quarter, about 66% of generation, up 12.5%. CREA said battery storage of about 9.1 GWh was operational, with roughly 3 GWh more expected by December, and that storage supplied up to 5.5 GW during night-time peaks, up from 4.1 GW in the previous quarter. Peak demand reached 270 GW on 16 July. Batteries are growing quickly but from a small base: 5.5 GW is about 2% of 270 GW, by our division.

“The day is well supplied. The evening depends on a train.”

Fuel Logistics & Railway Transport Interlock

The fuel: Power-plant coal consumption stayed near 79 million tonnes a month from June to September, according to CREA, while dispatch to plants fell from 74 million tonnes in May to 66 million tonnes in August. Stocks dropped to 21 million tonnes by 30 September, 36% of the 58 million tonne normative requirement, and the number of plants with stocks below 25% of requirement rose from 32 on 22 August to 85 on 1 October. Simple subtraction shows why stocks fell: plants consumed about 79 million tonnes a month while dispatch in August was 66 million tonnes. If both figures describe the same month and the same plants, stocks would fall by roughly 13 million tonnes. The figures are CREA's, the subtraction is ours, and dispatch and consumption may be measured differently, so we offer it as an illustration and not a finding.

The railway: Indian Railways reported on 14 October that September freight loading was 135.35 million tonnes, up 6.14%, with coal loading up 9% and an average of 443 coal rakes supplied per day, up 11.6%. These are all-network figures, not figures for power-plant coal alone. The report did not explain the reason for the rise.

Are the two linked? The timing is consistent with a movement to restore coal to power plants as stocks fell. But the railway report does not say that, CREA does not say that, and many factors drive coal loading, including industrial demand and exports of other goods. We therefore put the link as a question for those who have the data, not as a conclusion. A reader should note the two sources measure different things: CREA's dispatch figure covers coal sent to power plants from all sources, while the railway's covers loading on its own network.

Three Observations on Grid Fragility

What the weak link looks like: Three observations follow from the figures, each of which can be checked: 1. The day is well supplied. Solar records and curtailment suggest midday supply sometimes exceeds what the grid can absorb. 2. The evening depends on fuel logistics. Coal supply to plants is a transport problem as much as a mining problem. 3. Batteries help but are small. They covered a small share of peak demand in the quarter.

What would help: our reading: More storage would move midday surplus to the evening, as the IEEFA findings in our Energy package describe: about 10.3 GW commissioned against a CEA target of 60.63 GW for 2030. Better coal logistics would reduce the risk of plant shortfalls. Both take time.

Implications for Businesses, Planners, and Knowledge Limits

What it means for businesses: A business with continuous operations should know its backup arrangements and ask its distribution company about outage history. A business with flexible loads can shift consumption to daytime hours, when power is abundant.

What it means for planners: The summer peak is over, but winter brings different pressures. The decisions made on coal stocks and storage in the next quarter will matter for next year.

What we do not know: We do not know whether outages occurred, how stocks have moved since 1 October, or the cause of the fall in dispatch. We make no forecast.