Caltrain's electric fleet more efficient than expected • Hacker News Board

Re: Caltrain's electric fleet more efficient than expected

#131

Post by fsckboy » Sat, Jan 25, 2025, 4:34 AM UTC

>regenerative braking on the new trains is generating and sending back to the electric grid approximately 23% of the energy consumed by the system

does this make sense? let's round that 23 up to 25%, and say brake energy regeneration is 100% efficient (it's not): one quarter of the energy put into the system comes back out? city driving in a car, you might have your foot on the brake 25% of the time (yes, that's not how it works, just think conceptually) but a train spends a lot of time running, and comparatively a small amount of time braking, and if you were to detach the engine from the train, one doesn't get a sense the train would roll very far unpowered, so while there's momentum to scavenge, it doesn't seem like 25% of the total

I'm just thinking, how do these numbers make sense?

Re: Caltrain's electric fleet more efficient than expected

#132

Post by jwagenet » Sat, Jan 25, 2025, 4:34 AM UTC

bluGill wrote: post #95

pm90 wrote: post #73

Earlier quoted context omitted.

Considering the anti transit attitude of most suburban dwelling Americans I am personally glad they are touting this.

Considering the bad transit options they get anti transit is the rational choice. Suburbs are dense enough for great transit but it is expensive and so nobody can afford to give it to them. Thus continuing the cycle of bad transit worth opposing as the waste of money it is.

Suburbs are absolutely not dense enough for great transit, and the per capita coverage is bad enough the expense isn’t worth it. They can get sparse bus or light rail coverage and thats it. Great transit offers coverage for stops every mile, preferably half mile. Systems like Caltrain and bart are great for regional rail, but anywhere serviced by them is generally not well enough connected that you don’t have to drive to the station.

Re: Caltrain's electric fleet more efficient than expected

#133

Post by erikgaas » Sat, Jan 25, 2025, 4:38 AM UTC

jeffbee wrote: post #126

erikgaas wrote: post #102

Earlier quoted context omitted.

The other important implication is how Caltrain could be routed through underground tunnels to Salesforce transit center. 4th and king isn't super nice and, correct me if I'm wrong, but it isn't well connected to other modes of transport. Maybe some muni buses.

4th & King has much better connections to transit and neighborhoods, and I hope they never build that tunnel.

Much better really? Looking at the muni map, pretty much all transit clusters around downtown. And bart doesn't even stop at 4th and King. You have to go to Millbrae for a close-ish transfer. Added to that the transit center is very close to the ferry building. And then you have golden gate transit. And it's a hub that has tons of space to accommodate a ton of transfers.

https://www.sfmta.com/maps/muni-service-map

Re: Caltrain's electric fleet more efficient than expected

#134

Post by mikepurvis » Sat, Jan 25, 2025, 4:38 AM UTC

fsckboy wrote: post #131

> regenerative braking on the new trains is generating and sending back to the electric grid approximately 23% of the energy consumed by the system does this make sense? let's round that 23 up to 25%, and say brake energy regeneration is 100% efficient (it's not): one quarter of the energy put into the system comes back out? city driving in a car, you might have your foot on the brake 25% of the time (yes, that's not…

Firstly, I believe the trains are EMUs, so every bogey is powered rather than having the whole thing hailed by an engine; this is actually a huge benefit of electric as the trains can accelerate to speed much faster when they’re all wheel drive.

But to address your main point, the rolling resistance of a train in motion is tiny; basically all the energy cost is at acceleration time— it probably cruises at like 5-10% power.

Re: Caltrain's electric fleet more efficient than expected

#135

Post by tbrownaw » Sat, Jan 25, 2025, 4:39 AM UTC

timewizard wrote: post #125

whyenot wrote: post #34

It's great, but it took more than 20 years to get here due to environmental reviews and shaky funding. ...and this was just re-fitting an existing, relatively short stretch of track! We (as Californians) have GOT to do better than this! There are huge infrastructure projects that we need to undertake in the coming years. We have got to cut the red tape and properly fund projects.

> more than 20 years to get here due to environmental reviews How thorough were they being? > We (as Californians) have GOT to do better than this! We pay more taxes than anyone else in the country. /We/ are doing our part. The administration needs to be held accountable. > We have got to cut the red tape and properly fund projects. We need to light a fire under the administration and someone needs to take a wrecking…

> /We/ are doing our part. The administration needs to be held accountable.

... By the electorate, who clearly aren't doing their part if things like this keep happening.

Re: Caltrain's electric fleet more efficient than expected

#136

Post by Animats » Sat, Jan 25, 2025, 4:39 AM UTC

That's good to hear. Especially since the electric trains accelerate so much faster than the Diesel ones did. Have you been next to one at takeoff? They're going about 40MPH before the train has traveled its own length. Probably limited more by standing passengers than power. Most of the energy used accelerating is recovered at the next stop, so the fast acceleration does not consume much energy.

Re: Caltrain's electric fleet more efficient than expected

#137

Post by ninetyninenine » Sat, Jan 25, 2025, 4:40 AM UTC

verteu wrote: post #89

ninetyninenine wrote: post #64

Earlier quoted context omitted.

It's fair. NYC is 8.8 million, bay area is 7 million. Tokyo is about double that. Not being negative. Being realistic. It's unfortunate that being realistic often is negative. Transit here is garbage. You either luck out and live and work near transit or you're like most people and have to drive. A couple million in energy savings doesn't mean anything compared to the amount wasted by cars.

Surely the relevant metric is population density?

You have the causal arrow backwards. A high density train network enables population density and high energy efficiency.

At current population density all of our lives would improve if a network as dense as the tokyo metro appeared in the bay area over night.

Re: Caltrain's electric fleet more efficient than expected

#138

Post by ninetyninenine » Sat, Jan 25, 2025, 4:41 AM UTC

Spooky23 wrote: post #124

ninetyninenine wrote: post #65

Earlier quoted context omitted.

If it's not magic why isn't it being done? That's the point. This news is rather pathetic strictly because a better scenario is NOT magic.

The economy is built around juicing home values. The costs make it too expensive for eminent domain and nimby people mobilize now.

Agreed, hence why the situation is rather pathetic.

Re: Caltrain's electric fleet more efficient than expected

#139

Post by hamandcheese » Sat, Jan 25, 2025, 4:42 AM UTC

justinzollars wrote: post #47

> With the agency expecting approximately $6 million annually in energy credits from the California Air Resources Board’s Low Carbon Fuel Standard Program the first year of electric service will have lower fuel costs than the previous diesel service Thats the key. Without the subsidy its more expensive and less efficient than carbon based fuel. In the long run we are worse off, because the subsidy can't last forever.

> Currently, Caltrain is providing that power to the grid free of charge as there is no legal requirement for the agency to be reimbursed for the energy generated.

With further investment in energy storage it sounds like they could nearly cover a lost subsidy.

Moreover, the improved service from electric (faster acceleration and better air quality) seem very worthwhile.

Re: Caltrain's electric fleet more efficient than expected

#140

Post by ninetyninenine » Sat, Jan 25, 2025, 4:45 AM UTC

ricw wrote: post #91

ninetyninenine wrote: post #65

Earlier quoted context omitted.

If it's not magic why isn't it being done? That's the point. This news is rather pathetic strictly because a better scenario is NOT magic.

It is. A bunch of Bart stops now have developments around them, just look at MacArthur in Oakland with its 40 floor residential building next to Bart.

How is that magic? That's good!

The problem is that Bart network will barely get denser. At the rate they're building it, your great great great great great grandkids will live in a bay area where most people don't need to jump on a car to get to work.

We can do better. It's not magic. But we don't. And that is pathetic.