5 ms·

Regenerative breaking can already exist for trains without adding in the carbon capture [1]. Instead of adding batteries, and thus weight, the train supplies p

Regenerative breaking can already exist for trains without adding in the carbon capture [1]. Instead of adding batteries, and thus weight, the train supplies power back to the grid when it breaks. Thus, the cheaper source of energy described here can be achieved without the carbon capture, and consequently, we can use that power to power other things, reducing energy generation overall and reduce CO2 emissions. Thus, it seems like the primary benefit here is using the train's motion to replace the fans required for carbon capture and thus piggybacking on the energy already expended by the train to move. That seems logical, though it could be deployed irrespective of regenerative breaking. Basically we should do regenerative breaking regardless as it is just more energy efficient. Regenerative breaking can primarily be deployed in electric trains anyway as you use the existing motors to break the train, and in so doing, generate electricity from those motors. Adding electric motors and a battery to diesel trains JUST for carbon capture seems foolish. One question I had: how does this carbon capture change the aerodynamics of the train and thus its efficiency? [1] https://www.ctc-n.org/technologies/regenerative-braking-trains#:~:text=Train%20Regenerative%20Braking%20Introduction,reversed%2C%20slowing%20down%20the%20train https://www.ctc-n.org/technologies/regenerative-braking-trai....

energ8 4y ago
There might be an additional benefit for fossil fuel trains. Point source capture is usually more efficient than direct air capture. This isn't necessarily directly point source, but if the diesel exhaust is partially directed into the capture train, the CO2 concentration should be higher, and could have a more efficient CO2 capture.
X6S1x6Okd1st 4y ago
Do trains always have a connection to the grid?
- j-pb 4y ago
  Those trains yes, because it's the grid that powers them (through constantly connected overhead lines). There is not really the need to feed that energy back to the grid though, as there are plenty of other trains that are happy to gobble it up.
7erydyeioei 4y ago
Unless you're in a sufficiently carbon dense region (third world maybe) it seems exceptionally optimistic to assume the train will be able to power more than itself in either scenario. Not that it's not a good idea anyway but unless the train can cover itself with spare change leftover you're not going to be powering anything extra without creating waste.
unholiness 4y ago
Direct air capture is the holy grail of climate solutions. Its success would offer us a way to put the cat back in the bag, and see CO2 levels decrease. The problem is how absurdly expensive these things are. In the next couple decades, even being optimistic, it's hard to forsee a scenario where we've plugged enough holes in our infrastructure that direct air capture will be better or cheaper than doing more capture inside some existing pollution site, or replacing more fossil fuels with clean energy. But one day we will reach that point. And when we reach that point, anything to reduce the cost of carbon capture a little bit will help a lot. So yes, regenerative breaking connection is sort of a distraction. But improvements to DAC efficiency are very welcome, and improving airflow by mounting the mechanism on a high-speed train seems like it offers a big improvement.
aaron695 4y ago
hmryehbut 4y ago
Great. Now build out the infra… adding carbon to the air. The state of things leave little wiggle room for iterating on and disposing of one experiment after another Reducing consumption and industrial activity is a sure fire way to reduce carbon in the air But I expect we’ll avoid intentional figurative death for adults today and chuck the risk over the fence into the future as usual, given how people behaved when lockdown meant “no haircuts”.
samatman 4y ago
That's rather a lot of spelling braking as breaking to let pass without comment on a top post. I know this is very nearly content-free. Forgive me, it's a compulsion.
midoridensha 4y ago
>Adding electric motors and a battery to diesel trains JUST for carbon capture seems foolish. There's no such thing as a train propelled by a diesel engine. All "diesel trains" are diesel-electric. They use electric motors for propulsion, and for braking as well. Normally, there's a big resistive grid on the roof where the power is dumped.
- jayelbe 4y ago
  That's categorically untrue. Diesel-electric trains are not uncommon, but there are many, many trains driven directly mechanically or hydraulically by the diesel engines. Nearly rode on one these just yesterday: https://en.m.wikipedia.org/wiki/British_Rail_Class_150 https://en.m.wikipedia.org/wiki/British_Rail_Class_150
  - midoridensha 4y ago
    I stand corrected: some really backwards countries still have crappy old trains that run purely on diesel. In America, all the freight trains and diesel passenger trains are diesel-electric, and have been for many decades. And America isn't even much of a leader in passenger rail. I guess I shouldn't be too surprised about the UK; this is a country that still doesn't know how to make a single water faucet that combines hot and cold water.

energ8 4y ago

There might be an additional benefit for fossil fuel trains. Point source capture is usually more efficient than direct air capture. This isn't necessarily directly point source, but if the diesel exhaust is partially directed into the capture train, the CO2 concentration should be higher, and could have a more efficient CO2 capture.

X6S1x6Okd1st 4y ago

Do trains always have a connection to the grid?

j-pb 4y ago
Those trains yes, because it's the grid that powers them (through constantly connected overhead lines). There is not really the need to feed that energy back to the grid though, as there are plenty of other trains that are happy to gobble it up.

7erydyeioei 4y ago

Unless you're in a sufficiently carbon dense region (third world maybe) it seems exceptionally optimistic to assume the train will be able to power more than itself in either scenario. Not that it's not a good idea anyway but unless the train can cover itself with spare change leftover you're not going to be powering anything extra without creating waste.

unholiness 4y ago

Direct air capture is the holy grail of climate solutions. Its success would offer us a way to put the cat back in the bag, and see CO2 levels decrease. The problem is how absurdly expensive these things are. In the next couple decades, even being optimistic, it's hard to forsee a scenario where we've plugged enough holes in our infrastructure that direct air capture will be better or cheaper than doing more capture inside some existing pollution site, or replacing more fossil fuels with clean energy. But one day we will reach that point. And when we reach that point, anything to reduce the cost of carbon capture a little bit will help a lot. So yes, regenerative breaking connection is sort of a distraction. But improvements to DAC efficiency are very welcome, and improving airflow by mounting the mechanism on a high-speed train seems like it offers a big improvement.

aaron695 4y ago

hmryehbut 4y ago

Great. Now build out the infra… adding carbon to the air. The state of things leave little wiggle room for iterating on and disposing of one experiment after another Reducing consumption and industrial activity is a sure fire way to reduce carbon in the air But I expect we’ll avoid intentional figurative death for adults today and chuck the risk over the fence into the future as usual, given how people behaved when lockdown meant “no haircuts”.

samatman 4y ago

That's rather a lot of spelling braking as breaking to let pass without comment on a top post. I know this is very nearly content-free. Forgive me, it's a compulsion.

midoridensha 4y ago

>Adding electric motors and a battery to diesel trains JUST for carbon capture seems foolish. There's no such thing as a train propelled by a diesel engine. All "diesel trains" are diesel-electric. They use electric motors for propulsion, and for braking as well. Normally, there's a big resistive grid on the roof where the power is dumped.

jayelbe 4y ago
That's categorically untrue. Diesel-electric trains are not uncommon, but there are many, many trains driven directly mechanically or hydraulically by the diesel engines. Nearly rode on one these just yesterday: https://en.m.wikipedia.org/wiki/British_Rail_Class_150 https://en.m.wikipedia.org/wiki/British_Rail_Class_150
- midoridensha 4y ago
  I stand corrected: some really backwards countries still have crappy old trains that run purely on diesel. In America, all the freight trains and diesel passenger trains are diesel-electric, and have been for many decades. And America isn't even much of a leader in passenger rail. I guess I shouldn't be too surprised about the UK; this is a country that still doesn't know how to make a single water faucet that combines hot and cold water.