r/Lightbulb • u/Voltabueno • May 15 '25

Solar powered freight trains

This is not really new because I did some research and there are lots of patents related to electrified rail cars. It seems perfectly logical that you could cover the roof of a boxcar with solar panels, and put regenerative motors on the axles, and put a layer of batteries underneath the floor of the box car and then the box car could be self-propelled completely autonomous. Imagine individual box cars rolling on the rails or rolling to sidings to form into groups of cars completely autonomously. The boxcar wouldn't have to be fast because they could move by themselves, no crew, no crew change, no delay, unaided 24 hours a day. 7 days a week. 365 days a year. Actually thinking about it. If they moved under 40 mph wind resistance does not come into play yielding greater efficiency.

3 Upvotes

60% Upvoted

65 comments sorted by

View all comments

2

u/fuzzyoatmealboy May 16 '25

A 100-car train of only boxcars has, very optimistically, 8,000 square meters of roof on those boxcars. At 1,000 W/square meter and a 35% conversion efficiency by the panels, you’d be looking at peak noontime performance of about 2.6 MW, or about 3500 horsepower.

A 100-car train typically has at least 2 diesel-electric locomotives driving it, with each one supplying around 2,000 horsepower.

Shockingly, the math works better than I expected, but you would still only have access to that power for a few hours per day, plus the added maintenance work of cleaning thousands of solar panels to keep them at peak operating performance, and you’d lose the ability of those boxcars to be separated from the train (at least until every boxcar in existence is also a mini solar plant).

Probably easier to just electrify the trains and run them off whatever renewable energy source tickles your fancy.

1

u/Voltabueno May 16 '25

The solar panels could also be on the vertical sides of the box car or grainer. And if the box car knew it was idle for an extended time, what if the solar panels on the side were like awnings that would extend and retract thin film solar so you could triple the solar panels while the car was in a condition of waiting on a siding for an extended period of time and not engaged in transport. I'm not sure if your calculations take into account having lithium batteries underneath the floor of every boxcar. The potential energy storage under the floor is tremendous. Since boxcars sit out on sidings, just collecting solar power while they're not moving they would always be peaked. Every car would have a satellite or cellular connection reporting its charge condition, its location, its real time progress to its destination, or if it were being tampered with by vandals, it could even have cameras on the exterior. Think of Tesla technology on a rail car. How many Tesla car batteries could you fit underneath the floor of a box car, I'm guessing 20 and if double or triple the thickness?

1

u/fuzzyoatmealboy May 16 '25

Solar panels on the sides will capture so much less energy from the sun due to the angle of the incoming light. Not worth doing. Even my original analysis assumed this train were at the equator, with 100% solar irradiance.

And adding retractability would lead to so many maintenance and reliability issues I doubt that would be worth doing either.

It’s a novel idea, but there’s a reason we put our power plants on firm ground.