Well, sitting here in the dark, well dim, anyway, listening to the local radio coverage of our blackout. Feel sorry for our San Diego Trolley users and operators scattered around the system. Sounds like the commuter rails will be annulling a number of trains this evening probably because signal system backup batteries will be tanking in a hour or so.
Way fun!
That's why a number of the early trolley and electric railroad systems had a battery back-up. The batteries installed on the NYC Grand Central Terminal electrification were designed to support normal traffic for thirty minutes. For the SD Trolley, I'd say battery capacity should be enough for the train to reach the next station.
Another possibility would be a diesel locomotive with a pantograph, the purpose of which is to operate as a mobile substation.
- Erik
P.S. I was amazed how smooth, albeit slowly, the traffic was moving yesterday afternoon. Took me an hour to get home last night, maybe 22 minutes tonight.
Most of the storage batteries that were included in early street railway electrifications were not so much a back-up source of power as a way of balancing the load. The battery would handle part of the higher demand during rush hours and would be re-charged overnight when demand was low. The batteries were an early version of peaking plants.
The storage batteries for interurbans were intended more for load smoothing, as related in Ernest Gonzenbach's Engineering preliminaries for an electric interurban railway, though there was a hint at providing back-up. Many of the early interurbans generated their own power in a single power plant and had a single set of lines for transmission, so would have been vulnerable to power loss. FWIW, the Spokane and Inland Empire even had the batteries tied in with the AC portion of the electrification.
The batteries used with the Grand Central electrification were sized to provide full load power for one hour, which implies that back-up power was a major reason for installing the batteries.
There was an article that appeared recently Slashdot of all places about using flywheels to store the regenerated braking energy from rapid transit trains. My first though that ultra-caps would be simpler that flywheels, though the flywheels could provide full power for a few minutes rather than a few seconds in the case of ultracaps. A few minutes of power would be enough to ensure that the trains could make it to a station after a grid outage.
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