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Batteries are now a viable option. They can pull power from the overhead lines or third rail when available and run on batteries when power isn't available. T

• stickfigure 8y ago
  For a single small passenger car without any grade, maybe. From that video: 90kw/hr of battery. At peak power output of 180kw, you could run that for 30 minutes. The ubiquitous GE Dash-9 used in freight service here in the US generates >3000kw and can run all day. They're also usually run in multiples to pull long heavy trains. I wouldn't expect to see battery powered trains in the US anytime soon, except maybe short passenger-only lines on the east coast (which are probably viable for electrification anyway).
  • Robotbeat 8y ago
    You, strangely, ignored the parent's point that you would just be using the batteries to reduce the amount of overhead wires you need, i.e. one would have opportunity to recharge several times a day. (It's not helpful to focus on the specifics of a proof of concept--unimportant in this discussion about what is feasible--versus the fundamental figures of merit of the technology... Unless one is prepared to make the case that the specifics are the limits of the technology.) There are 100MW power, 100MWh energy lithium ion batteries installed already (with 1GWh on the way). There's no technical reason you couldn't have battery powered trains. The "batteries are too weak" argument is dead.
    • creato 8y ago
      Can you even transfer close to 3000 kW through any overhead wires or third rail systems? It seems like 25 kV is the max voltage overhead lines run at. That's 120 A that you need to transfer through a sliding conductor. That sounds problematic to me, but I don't really know for sure...? And if you are proposing using batteries to reduce the amount of overhead wires you need, then the average power you need to transfer while connected to the wires increases, not decreases.
      • TylerE 8y ago
        The most powerful locomotives are all electric. Powerful freight locos have power outputs of over 13000kw
      • hvidgaard 8y ago
        If we take the hypothetical electric locomotive with a battery pack, it would probably decrease the peak load on the lines. You only need maximum power at acceleration and climb. The battery is perfectly capable at helping with the peaks, while recharging during the cruise when the power demand is low.
      • cardinalfang 8y ago
        A TGV can take over 12MW. It uses a single contact feeding the two power cars at each end of the train to avoid problems with oscillations in the overhead line at high speeds.
      • iggldiggl 8y ago
        To give some ball park figures, this is the default maximum current permitted per train according to national regulations: - UK conventional lines: 300 A @ 25 kV - UK third rail network: 6800 A @ 750 V - German conventional lines: 600 A @ 15 kV - German high speed lines: 1500 A @ 15 kV
    • stickfigure 8y ago
      I don't think you've run the numbers. A tesla powerpack is 50kw, 210kwh, and weighs 3500lbs. A freight train that would normally be pulled by four 3,000kw diesel electric locomotives would need 240 powerpacks, and could run for four hours before needing a full recharge. Those powerpacks would weigh 420 tons - the equivalent of say, four fully loaded freight cars, and cost around $25M (plus whatever the locomotives cost). The diesel-electric locomotives are a couple million each, ready-to-run. Ah hah you say, you only need the batteries between catenaries! How fast do you think you can charge those batteries? If you can charge the same as the full discharge rate, then you need 50% of your track to be electrified, and you need it every four hours (assuming you're willing to risk full discharge cycles). Trains don't move very fast, so that's pretty closely spaced. And even worse, you now need electrical infrastructure with twice the capacity - you need to charge the battery and move the train. Sure there's no technical reason you couldn't do this, but the economics are not looking good. Batteries are too weak.
      • kzrdude 8y ago
        420 tons of batteries sound like an insane resource consumption in terms or metals and rare earth metals.
      • daurnimator 8y ago
        Why assume 4 hours with a recharge? I'm thinking closer to max 15 mins without a recharge. This would allow skipping electrification in some tunnels; in rail yards; on track segments shared with non-electrified trains; and anywhere that it's too hard to run electric lines.
        • stickfigure 8y ago
          Sure... but now you're only saving a small percentage of the total electrification cost, and paying for increased cost, complexity, and maintenance of locomotives. It's not an obvious win.
        • Gibbon1 8y ago
          Far as I can tell he's also off by a factor of 4. Tesla 85hw battery pack 1200 lbs. 3000 kw X 4 hours = 1200 kwh. 1200kwh/85kw*1200 = 170,000 lbs. A GE/NS Dash 8 weighs in at about 390,000lbs