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.
Nearly rode on one these just yesterday: https://en.m.wikipedia.org/wiki/British_Rail_Class_150
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.
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.
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”.
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.
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.
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-trai....