India is Rolling Out Trains With Solar-powered Coaches That'll Save Thousands of Litres of Diesel (qz.com)

An anonymous reader shares a report: India's massive diesel-guzzling railway network is getting serious about its experiments with solar. On July 14, Indian Railways rolled out its first train with rooftop solar panels that power the lights, fans, and information display systems inside passenger coaches. Although the train will still be pulled by a diesel-powered locomotive, a set of 16 solar panels atop each coach will replace the diesel generators that typically power these appliances. The railways estimate that a train with six solar-powered coaches could save around 21,000 litres (5,547 gallons) of diesel every year, worth around $108,000. In 2014, Indian Railways consumed 2.6 billion litres of diesel, accounting for around 70% to the network's total fuel bill of $4.4 billion. The first of these trains will be pressed into service on the suburban railway network of New Delhi, one of the world's most polluted cities, before two dozen more coaches are fitted with similar rooftop solar systems. Retrofitting each coach with these system, including an inverter to optimise power generation and battery for storing surplus power, costs around $14,000.

Comments

Why not integrate with the locomotive?

[swillden]

I'm surprised that this isn't already integrated with the locomotive. The locomotive is almost certainly diesel-electric, so why did they have separate generators on the cars, rather than just drawing from the massive diesel generators in the locomotive? And if they add solar panels, to all of the cars why use them to charge batteries, rather than just feeding any excess juice to the locomotive, allowing it to burn a little less fuel to keep the train moving? I suppose this might result in a little bit of waste when the train is sitting still, so I suppose it's worth having enough battery capacity to capture that energy, but most of the time it's sitting still it's probably in a train station which could likely use the power.

Note that I know almost nothing about any of this stuff, so this isn't a "they're stupid for not doing that" post; I'm actually asking questions. I suppose the simple answer may well be "Because the locomotive isn't presently designed to do that".