Trackless Battery Trams

[Erik_Mag]

daveklepper

Most new light rail systems (overhead wire typical) and new rapid transit sytems (third rail typical) use 750V DC distribution, not 600V.

I seem to recall that the transition to 750VDC was getting started in the 1920's, so it's interesting to see the transition restarting. A good part of this is being driven by "wide band gap" (WBG) semiconductors (SiC and GaN), which require a lower margin of safety between operating voltage and breakdown voltage. For example, a silicon IGBT or FET with a 1200V breakdown rating would normally be operated at not more than 600V, while a 1200V rated SiC or GaN device ca safely be operated at 800V.

The factor of safety requirement is due to the damage caused by a cosmic ray induced neutron triggering a catastrophic breakdown in a device while holding off a potential near the breakdown voltage (e.g. FET in OFF state or reverse biased diode). WBG semiconductors are more resistance to adverse effects of high energy neutrons.

[daveklepper]

Most new light rail systems (overhead wire typical) and new rapid transit sytems (third rail typical) use 750V DC distribution, not 600V.  This has resulted from improvements in insulation and the trend  to computer-controlled AC motors.  Legacy systems, incliding DC commuter railroadds, stay with 600V, including new extensions.

[charlie hebdo]

Waiting for quantum batteries.

https://www.facebook.com/100064758788370/posts/pfbid02TTQCC55YrU3VSKRuShfyGNSDC5Ti799KfqQKS29RHD584A2Ut1ZY9xqEzhjD3r29l/?mibextid=I6gGtw

 

[Overmod]

Erik_Mag

#1 Choice of battery technology in tradeoffs between specific energy (w-hrs per lb/kg) and cycle life. Recharging at every stop suggests forgoing high specific energy batteries (Li-ion) for ultra-capacitors with cycle lifetimes now exceeding a million. Avoidance of Li-ion would also mean lower risk of battery fires.

That would be right, although I'd argue for ultracaps acting as a 'charge buffer' for a reasonably large chemical storage, with the option of iLINT-style hydrogen fuel-cell power away from wired charge points.  

#2 The charging stations will need to have a rather high peak power output with low duty cycle which would make the electric utility rather unhappy unless the charging stations have local storage.

The charging stations would be built like 'wayside storage', probably with shared capacity for utility purposes, and ought to be capable to tap any excess regenerated power to keep the chemical battery operational limits within the roughly 80-20 range that gives best chemical cycle life.  As with rail wayside, technologies other than battery or ultracap could be used, as neither weight nor envelope are critical -- I don't know how much interest there is in magnetic-bearing flywheel inertial storage, but it is an attractive way to source high-amperage current.

With the advent of EV's using 800V battery packs, propulsion systems that can run off of a 600V trolley are getting to be cheap. Makes me wonder if there is room for substantial cost redctions in LRV's.

Probably not until extremely large runs of common designs (like a light-rail equivalent of PRIIA) occur, or governments collude to get prices low.  I don't think there is any particular private market left in this country for either 600V direct or battery rail transit.

[Erik_Mag]

A couple of considerations/issues with the idea.

#1 Choice of battery technology in tradeoffs between specific energy (w-hrs per lb/kg) and cycle life. Recharging at every stop suggests forgoing high specific energy batteries (Li-ion) for ultra-capacitors with cycle lifetimes now exceeding a million. Avoidance of Li-ion would also mean lower risk of battery fires.

#2 The charging stations will need to have a rather high peak power output with low duty cycle which would make the electric utility rather unhapppy unless the charging stations have local storage.

With the advent of EV's using 800V battery packs, propulsion systems that can run off of a 600V trolley are getting to be cheap. Makes me wonder if there is room for substantial cost redctions in LRV's.

[charlie hebdo]

zugmann

 

 

charlie hebdo

The point is that it is much cheaper both in captal outlay and operational expenses.

 

 

And provides flexibility. 

It's funny, I just watched a video from a youtube "planner" that is against battery trolleys and wants the wired versions, because, who knows anymore. 

 

Follow the $ !!!

[daveklepper]

Battery buses exist that can recharg efficirerntly between each run.   Both Tel Aviv abd Jerusalem have about 25 each in operation.  I rode one in Jerusalem ntwice and reoported on the first ride in an earlier thread on this  Forum.

New York City has some, also.

[zugmann]

charlie hebdo

The point is that it is much cheaper both in captal outlay and operational expenses.

And provides flexibility. 

It's funny, I just watched a video from a youtube "planner" that is against battery trolleys and wants the wired versions, because, who knows anymore. 

[charlie hebdo]

The point is that it is much cheaper both in captal outlay and operational expenses.

[J. Bishop]

I see two issues.  First, if they share roads, they will shared congestion. If they are assigned a dedicated part of the road, that gives uplanes for auto and truck traffic. If a freeway is already congested, that is probably not an option.  So if they use private right of way, how does the cost of roadway compare with rail? 

Second issue is that using rubber tires on roadway is less energy efficient that steel wheels on steel rails. 

[charlie hebdo]

I have a former student living in Zhuzhou who says the stops seem similar to normal duration of buses.  Must be high voltage dc fast chargers.

 

[CSSHEGEWISCH]

The porblem might come in how long the trackless trolley would stop at each station to get a decent recharge.

[charlie hebdo]

https://www.weforum.org/agenda/2022/09/trackless-trams-help-revitalize-suburbs?utm_source=facebook&utm_medium=social_video&utm_term=1_1&utm_content=27383_China_trackless_trams&utm_campaign=social_video_2023

Recharge at each station stop.