We’re suckers for videos that explain dry-as-dust science in visually dynamic ways. General Electric’s “GE Show” bats one out of the park by explaining hybrid dynamic braking — a system that recaptures the energy from a train’s brakes that is usually lost — using magically animated statistics and artfully wrecked household objects.
The basic idea behind dynamic braking comes out of the Law of Conservation of Energy, which says that energy — like the kinetic energy of a moving locomotive — can’t be destroyed, only dissipated or transformed. Most braking systems are content to do the former, dissipating energy as heat. But that’s just wasting it. To visualize how much free energy is being thrown away, GE dramatized the effect by dropping normal-sized objects like baseballs, Christmas ornaments, and tomatoes into ballistic gel that absorbs the momentum.
Those crisply designed, floating statistics? That’s a measure of how much force the falling object imparts, via an equation you’ve surely forgotten since high school physics: Force=Mass X Acceleration. As the video notes, simply letting that energy dissipate away can get… messy.
GE’s dynamic braking system for trains works like that ballistic gel under the falling watermelons and bowling balls: it converts and stores some of the energy that’s usually lost as heat from normal brakes, and uses it to help power the train instead. But how much energy are we talking here? While all those dropped objects put together may not add up to much, a braking locomotive? That’s a lotta Newtons. (One Newton is equal to the amount of net force required to accelerate a mass of one kilogram at a rate of one meter per second per second.)
According to GE, “the energy dissipated in braking a 207-ton locomotive over the course of a year is enough to power 160 households for that year.” If you care to check their math, you can download a fact sheet on their Hybrid Locomotive here. As for us, we’re content to watch the exploding water balloon about 15 more times.