Productive Product: The city of Sacramento will soon test a system for regenerative braking on its light-rail trains. The idea is to capture the heat energy that exits trains when they're braking, and redirect that energy back into the grid. Similar technology is already used in hybrid cars, so this isn't too experimental, and therefore the prospects look good for taking it into production. Notes the Sacramento Bee: "Other than increased reliability, riders probably won't notice much after the energy system is installed. The energy storage device will be housed in an inconspicuous 10-foot cubicle close to existing stations. Besides hooking the system up to overhead wires, no further retrofitting of trains, tracks or stations is expected. Maintenance costs should be low since there are no moving parts."