[HN Gopher] Future trains could provide carbon capture
___________________________________________________________________
Future trains could provide carbon capture
Author : noplsbecivil
Score : 72 points
Date : 2022-08-02 15:37 UTC (7 hours ago)
(HTM) web link (spectrum.ieee.org)
(TXT) w3m dump (spectrum.ieee.org)
| elric wrote:
| What's the market for this? Are parts of the US unable to
| electrify trains for some reason? Surely the easiest way to
| capture the carbon is not to emit it in the first place, and if
| you are going to emit it, you might as well do it in a stationary
| power plant.
| AnimalMuppet wrote:
| > Are parts of the US unable to electrify trains for some
| reason?
|
| It basically comes down to cost. The electric infrastructure
| costs per mile to install, and per mile per year to maintain.
| The benefits come per train. If you don't have enough trains
| per day, it's not economical to electrify.
|
| There are some places, like the Union Pacific around North
| Platte, where you'd think that electrification would be a
| natural. But the problem is that 90 miles east of North Platte,
| and 20 miles west of North Platte, the lines split, and the
| traffic density goes down. Switching between electric and
| diesel locomotives twice in 110 miles adds operating cost.
| kitten_mittens_ wrote:
| Even in Boston, the metro transit authority (MBTA) has talked
| about the options for full electrification of commuter rail
| costing 18 billion+. https://d2o8eokdkim9o8.cloudfront.net/si
| tes/default/files/20....
| AlgorithmicTime wrote:
| elric wrote:
| Not sure why AlgorithmicTime's comment is dead, so I'll reply
| here. Long distances are probably tricky to electrify. I don't
| know enough about US railroads (what little I know of US
| railroads comes from playing Ticket To Ride) to comment on the
| feasibility, but there are very long electrified railways in
| China and Japan, across difficult terrain. There is probably
| not much benefit in feeding electricity from regenerative
| braking back onto the overhead line if it's a very long segment
| with only one train (no one to use the power + transmission
| losses).
|
| I wonder at which point diesel becomes the cleaner option here,
| if ever. One the one hand, you have to lug a lot of fuel around
| over longer distances (or you need refueling infrastructure).
| On the other hand, transmission losses can be significant.
| lstodd wrote:
| Well, you up the voltage and go AC, losses then become
| manageable. The move from 1.5KV DC to 25KV AC in Europe was
| about that exactly (many caveats apply, but it's basically
| that, a solved problem).
|
| If it's a somewhat loaded segment, someone would be there to
| consume the regenerated power. If it's not loaded then yes,
| no point in electrifying it to begin with.
| [deleted]
| noplsbecivil wrote:
| After reading this article, I was wondering if a similar approach
| could be used on cars? Could the braking energy be used in a
| similar way? What about for trucks?
| johnday wrote:
| Surely it is more efficient to store the braking energy in cars
| for acceleration, which then reduces the amount of fossil fuels
| burned in the first place? (AIUI this already exists)
|
| In fact i'm not sure why that wouldn't also apply to the
| trains...
| stormbrew wrote:
| I assume the issue is trains that aren't electric, and I
| assume even most electric trains don't have significant
| energy storage on the train itself, so might not really have
| much to do with energy from breaking.
|
| It probably especially makes sense that freight trains
| running off fossil fuels won't even consume much electricity
| at all (just enough to operate instruments in the
| locamotive?), though presumably passenger trains could make
| use of it.
|
| Maybe there are barriers to electrification of some trains in
| some areas.
| pmyteh wrote:
| Most electric trains only have a small service-and-
| emergency battery and don't have significant energy
| storage. For AC electric locomotives it's now standard to
| return electricity to the grid when using regenerative
| braking; that's harder with DC electric traction but is
| done in some circumstances (in others, the generated
| electricity is dumped into heat via a resistor bank).
|
| The main barrier to electrification is the high upfront
| capital cost of the electrification works, set against the
| longer-term per-train return in lower fuel and
| locomotive/multiple unit costs. Lines which are not
| intensively used are difficult to justify electrifying on a
| financial-returns basis, and that probably includes most of
| the world's long-distance freight lines.
| jimktrains2 wrote:
| Nearly all fossil-fuel burning train engines (I think the
| exception being a handful of hydraulic engines in Germany?)
| are diesel-electric, which use the diesel engine to turn an
| electric generator to power electric traction motors.
| (Dynamic breaking is when those traction motors are used as
| generators, but that electricity is usually dissipated as
| heat immediatly.)
| Glawen wrote:
| Tramway are regenerating power and injecting them back in
| the grid when they brake. I think electric trains do it as
| well, the resistor grid is only used when not enough power
| in generated
| nope96 wrote:
| Ah, maybe this is how Snowpiercer drives itself!
|
| (A sci-fi show where the only remaining humans live on a train
| that circles the world, they never explain how the train has
| infinite fuel.)
| runarberg wrote:
| If I remember correctly, in the movie it was hinted that the
| train's mechanic (Wilford) invented a perpetual motion machine.
| I'm not sure if the original graphic novel or the TV shows
| suggests something similar.
| cpdean wrote:
| The thing I hate about this is it continues to belittle the
| severity of climate change as something that future society will
| fix for us.
| 2OEH8eoCRo0 wrote:
| Nobody wants to be told to buy fewer goods, ration meat, ration
| fossil fuels, etc.
| MattGrommes wrote:
| I always consider things like carbon-capture to be under the
| category of "We need to do all of the above". Capturing carbon
| at scale gives us more time to move to renewable energy, which
| is going to take longer than we have. So we need to do capture,
| and renewables, and reducing overall energy, and whatever else
| we can think of. If we had started moving to renewables and
| electrifying everything 30 years ago, carbon capture wouldn't
| be needed. But it is needed now.
| mdavis6890 wrote:
| I still do not understand how any human-developed carbon capture
| techniques is going to be better or more efficient than just
| planting a tree. A (living, growing) tree can capture quite a lot
| of carbon for almost no cost, directly from the atmosphere. More
| generally, vegetation biomass growth is carbon (and hydrogen)
| capture in action on planetary scale - almost for free.
| photochemsyn wrote:
| I think the example to look at is biological nitrogen fixation,
| vs. the Haber-Bosch process, which operates at high pressures
| and temperatures and therefore has a small area footprint. You
| can do biological nitrogen fixation with legume (pea, bean)
| crops in symbiosis with nitrogen-fixing bacteria nodules, and
| then compost the crop to generate a nitrogen-rich fertilizer,
| but this means devoting large fields to the process. The Haber-
| Bosch process in contrast can produce much greater amounts of
| pure ammonia in a single location.
|
| Haber-Bosch traditionally has relied on large fossil fuel
| inputs, but it's possible to get the hydrogen from the process
| via hydrolysis of water, powered by renewable energy (or
| nuclear), and use electricity instead of fossil fuels to run
| the high-temperature, high-pressure catalytic reaction (H2 + N2
| -> NH3).
|
| The same arguments apply to carbon capture and fixation: you
| can do it in an industrial setting, for example the North
| African desert (which doesn't support much plant growth), you
| could use seawater as the hydrogen source and plentiful
| sunlight and PV/concentrated thermal for electricity to drive
| the carbon capture (fans etc.) and the analogous version of
| Haber-Bosch (Fischer-Tropsch) for CO2 - CO + H2 ->
| hydrocarbons.
| elif wrote:
| Considering that most of the energy supply is currently going
| into brake pads, designing an efficient regen braking system is
| quite reasonable.
|
| Once we are on renewable energy, the efficiency argument will
| make it undeniably efficient.
|
| This drought is teaching us that "just grow a tree" is not
| always viable, and the resulting water crisis is also begging
| the question "with who's water?"
| fgeiger wrote:
| Who's water? Planting trees usually helps to prevent droughts
| because they keep water in the local climate with effects
| like shading the ground and containing rainwater (instead of
| the rain just washing down the next river). I'm that sense
| watering them is a good investment.
| NegativeLatency wrote:
| I read The Ministry for the Future recently and it was largely
| centered around the idea of a Carbon Coin (money based on how
| much carbon you sequestered or didn't emit).
| https://en.wikipedia.org/wiki/The_Ministry_for_the_Future
|
| Would be interesting to try it IRL, as you'd potentially have
| lots of different approaches being tried vs some kind of top
| down solutions
| bequanna wrote:
| From your source:
|
| > Specifically, a coordinated global round of unconventional
| quantitative easing through the issuance of a complementary
| currency, called the carbon coin, to be issued in proportion
| to the mass of carbon that is mitigated.
|
| That is just nuts.
|
| The result would be like every other time money is printed:
| Wealth flows to those that know how to game the system while
| inflation erodes the wealth and income of normal people.
| TremendousJudge wrote:
| Or at least create the hydrocarbons in a factory, sucking the
| carbon from the atmosphere, and using energy from renewable
| sources or something of the sort. This would be carbon neutral
| at least, and still allows liquid fuels to be used. I have
| never seen anybody invest into this research. Somebody please
| correct me if I'm mistaken here.
| noplsbecivil wrote:
| Not quite there yet, but https://solugen.com/ are trying
| L_226 wrote:
| Because trees cannot be grown just anywhere, they require
| specific [land, water, nutrient] conditions that also happen to
| be the same things that are already under pressure from our
| civilisation. This is caused by things like extensive monocrop
| agriculture, grazing etc. Furthermore, trees do not necessarily
| sequester carbon beyond their lifespan - the sequestration is
| an additional process that may or may not occur naturally.
| Think of old trees dying, falling down and decomposing vs old
| trees dying and being covered by mud.
| ch4s3 wrote:
| Photosynthesis is pretty inefficient and trees release the CO2
| when they rot, so they aren't great for long term storage. At
| certain phases of growth, forests are actually carbon positive.
| DAC can bind carbon to rock or pump it deep underground where
| it will stay potentially forever(on any meaningful human
| timescale). You can also directly account for the tons of CO2
| removed by DAC which makes it more used for carbon trading
| schemes that financially incentivize capture.
| njarboe wrote:
| Many trees, if they are not cut down, grow for hundreds of
| years. And trees are just great to have around in general.
| ch4s3 wrote:
| That's true, but they don't fix any more carbon after
| they're fully grown. I'm not against tree planting, but
| it's probably a bit oversold as a solution. Kelp probably
| presents a more interesting opportunity.
| tunesmith wrote:
| It's not either-or. Planting more trees is necessary but not
| sufficient.
| kitkat_new wrote:
| you only can plant so much trees, with no guarantee that they
| even will grow old; currently we do everything but increase
| tree "population", because instead of going vegan we have ever
| rising meat consumption demanding more and more land for
| agriculture.
|
| Even restoring all the forests that have existed pre the
| industrialization will not help much, because it only resets a
| small part of the emissions. All fossil fuel burned is still in
| the atmosphere, likewise increasingly more methane.
|
| Additionally, it's easily used for green washing.
|
| Plant trees -> Yai carbon is offset, can emit like before; then
| trees are cut down, burn or don't even grow, and the next
| company can plant trees at the same land
| jjk166 wrote:
| Trees capture carbon, but they don't sequester it. You need
| additional steps to prevent the biomass from decomposing. This
| isn't too hard, generally just burying plant material below
| enough earth will do the trick, but it's a substantial expense
| at scale.
|
| And scale is really the issue. All the world's forests combined
| currently absorb about 20% of CO2 humans currently emit. To go
| neutral, you're looking at planting around 12 trillion trees.
| Worse still, about 30% of Earth's land surface area are already
| covered by forests, so you can't simply expand the forests to
| get the required carbon capture.
|
| The only realistic way to achieve 100% carbon capture by
| biological means would be to seed algae blooms in the ocean,
| which for short term carbon uptake would work pretty well, but
| when that algae dies it is way harder to prevent it from
| decomposing, meaning you don't get long term sequestration.
| Further, you are talking about terraforming-level changes to
| marine environments all over the world. Beyond the catastrophic
| effects that can have on other species, the full effects of
| what that might do to us are impossible to fully predict.
|
| Artificial carbon capture might have higher capital costs since
| the equipment is not self replicating, but it can be orders of
| magnitude more efficient in terms of energy, CO2 capture rate,
| and land use requirement.
| njarboe wrote:
| Many trees live for over 500 years (Redwoods, Cedars, Douglar
| Fir, Oaks, etc.). They can be part of the solution of keeping
| CO2 levels down while our energy system is de-carbonized. Go
| ahead and plant trees. They are great in many other ways
| also.
| jjk166 wrote:
| Again, the real deal breaker is needing 1.6 earths worth of
| land. No one is saying planting trees is a bad thing, but
| there is no escaping the need for other methods of carbon
| capture.
|
| Trees tend to stop growing after about 150 years, so trees
| left standing longer than that will delay releasing the CO2
| they've already captured, but will not continue to capture
| carbon. Indeed you probably want to cull trees before their
| growth rates start to decline around the 100 year mark to
| maximize your carbon capture rate.
| robocat wrote:
| Do you have a link that summarises the "FAQ" answers you
| have made?
| adregan wrote:
| If you don't mind videos, these are a pretty good
| explainer: https://www.youtube.com/playlist?list=PLxlgF_E
| chG56YnW2bLDk-...
| runarberg wrote:
| Can't you just use the wood for something instead? I've seen
| a lot of innovative use for wood in large construction
| projects. For example, there was a recent proposal to replace
| the West Seattle bridge with a timber through arch bridge,
| and timber skyscrapers are apparently now a thing. This is
| especially true since concrete is a really polluting
| industry, and finding ways to use less cement is a pretty
| solid climate action.
| krallja wrote:
| There isn't enough wood used, by several orders of
| magnitude.
| [deleted]
| jjk166 wrote:
| There simply isn't that much demand for wood. It is already
| used extensively as a building material, but only a tiny
| fraction of the world's forests are used for lumber
| production. Indeed lumber production doesn't even make up a
| large portion of trees that humans clear. For context 12
| trillion trees of lumber would be enough to build 100 to
| 500 two story residential homes per human being on earth.
|
| Again, this doesn't really matter since this wouldn't
| physically fit on the planet.
| brnt wrote:
| Some say concrete should be replaced wholesale with wood
| (CLT). I imagine that would make a dent?
| ninju wrote:
| Of course the creation of concrete has its own
| environmental impact
|
| https://psci.princeton.edu/tips/2020/11/3/cement-and-
| concret...
| jjk166 wrote:
| Every year humans use approximately 9 Billion tons of
| concrete. The mass of 12 Trillion trees is approximately
| 1100 years worth of concrete. This much lumber would need
| to be used every 200 years or so.
| runarberg wrote:
| I see, so we are never going to be able to use trees to
| capture our current current CO2 emissions. However would
| it be possible to use trees (and other photosynthetic
| organisms) to capture our historic emissions in a mass
| global atmospheric cleanup efforts, after we've mostly
| gone carbon neutral? Or is that also like a 1000 year
| effort even if we became carbon neutral tomorrow?
| jjk166 wrote:
| If we stopped emmitting CO2 tomorrow, a realistic
| increase in number of trees (~1 trillion trees) would
| take about 900 years to return to pre-industrial co2
| levels. The more trees you plant, the faster it goes, but
| even if you cover the entire planet in forest (including
| places like Antarctica and the Sahara), you're still
| looking at centuries.
|
| Other organisms can be used as well, but again you need
| to sequester the carbon.
| runarberg wrote:
| Thanks. I appreciate your answers here. This is why I
| love HN. Getting answers to questions on niche topics I
| don't even know how to begin searching for.
| r_hoods_ghost wrote:
| Pretty much. I don't have the numbers but the phrase to
| always bear in mind is "fossil carbon." All that oil, gas
| and coal was once living bio matter (to a first
| approximation). Industrial civilisation has been
| predicated on us burning fossil carbon laid down over
| millions of years by earths organisms. It will take more
| than a few decades to remove the excess that we have
| pumped in, even if we reforest the earth, reduce the
| population and all become ascetics.
| kiliantics wrote:
| How are you arriving at the 12 trillion trees number? I think
| there are some less obvious ways that trees can capture more
| carbon. For instance, trees build soil over time. Much of the
| deforested land in the world has had its topsoil washed away
| without trees to hold it in place. That soil is also a form
| of captured carbon.
| nanomonkey wrote:
| Totally agree, woody biomass is being under utilizes these
| days. Gasification produces syngas which can be used to produce
| heat and electricity when wind and solar aren't producing. The
| biochar that is left over can be introduced into the soil to
| improve it's nutrient and bio-activity (terrapreta). This is
| essentially reverse mining of carbon and is stable for
| thousands of years in the soil. It also keeps the biomass from
| producing greenhouse gases from decomposition.
|
| Beyond trees, we should also be growing algae and other plant
| mater to sequester more carbon and produce oils, sugars and
| other useful ingredients for our lives. This can be done at sea
| or in areas where water is scarce and normal vegetation grows
| poorly.
| Ensorceled wrote:
| > could capture carbon dioxide for less than US $50 a metric ton
|
| We currently are emitting 50 BILLION tons per year planet wide.
| So a mere $2.5 trillion per year to solve the problem? And a lot
| of trains.
| guelo wrote:
| Doesn't it make more sense to capture the carbon from the train's
| diesel engine's tailpipe instead of trying to capture it from the
| air using fans?
| thescriptkiddie wrote:
| Trying to put mobile carbon capture systems on diesel trains
| seems absolutely foolish when electric trains exist. Just put up
| the damned wires, it will save money in the long run.
| TremendousJudge wrote:
| I really don't understand how carbon capture can make sense, in
| terms of thermodynamics. Burning hydrocarbons releases energy,
| plus carbon dioxide and water vapor. Capturing the carbon dioxide
| back would, in some way, require an equivalent amount of energy
| to be spent, right? Where is this energy coming from? In this
| case, it's actually mentioned in the article (unlike many other
| carbon capture proposals): add regenerative braking to trains --
| plus make the engines work harder by adding a lot of extra air
| resistance for the filtering system.
|
| Meanwhile, the European electric grid -- and therefore its
| electric trains -- is partly ran by burning fossil fuels (not to
| mention the manufacturing processes for the proposed batteries
| and filters). So you're burning carbon in order to get carbon out
| of the atmosphere -- there's no way that equation comes out as a
| net negative for emissions, there are inefficiencies everywhere.
|
| This is honestly one of the most compelling carbon capture
| proposals I have read, and it still doesn't make sense to me.
| What am I missing here? Why is this being taken seriously?
| kitkat_new wrote:
| the energy is coming from the sun.
|
| And you are right... even worse: putting carbon emitted back
| into the ground requires not only the energy gained through
| burning, but several multitudes of that.
|
| That's why not burning it in the first place is almost always
| better. Still, carbon capture is necessary, because there are
| things that are extremely hard to substitute. Further, if we
| don't go for negative emissions, we will have at least 4
| degrees of warming (even if we stop emitting now).
|
| Just watch out for greenwashing
| blueflow wrote:
| I feel you, the proposal is nonsense, thermodynamics-wise. The
| money on the project would be better spent planting trees.
| photochemsyn wrote:
| Artificial photosynthesis is absolutely required in several
| sectors, if you want to eliminate the use of fossil fuels.
| International air travel is the main example, so is space
| travel, and global shipping is a little behind. There's no way
| to fly passenger jets over the Atlantic and Pacific Ocean using
| battery power; the density is just too low. Likewise, if you
| want to have SpaceX continue to launch large methane-fueled or
| RP-1 fueled rockets without fossil fuels, capture of
| atmospheric CO2 and conversion to hydrocarbon fuel will be
| needed.
|
| It's also a way of storing energy for long periods of time,
| i.e. if you're in the near pole regions of a planet, and want
| to capture solar energy in the summer and use it in the winter,
| batteries aren't going to work on those timescales. Some other
| means, generally a stable chemical conversion, will be needed.
| Converting carbon dioxide to methane or gasoline, converting
| nitrogen to ammonia (a bit dirty), even converting iron oxide
| to reduced iron, are all possible methods of doing this.
|
| As far as converting atmospheric carbon dioxide to a form that
| won't eventually get back in the atmosphere, that's pretty
| difficult (you have to make limestone, CaCO3, or perhaps carbon
| fiber building materials, or even better, diamond).
| TremendousJudge wrote:
| I'm not against that point, as I mentioned in another
| comment, research into hydrocarbon synthesis is the only
| "carbon capture" scheme that makes sense to me, because it's
| not promising anything for free. "We'll use this
| solar/wind/nuclear energy to create fuels out of the air, and
| then we'll burn them later for less" makes thermodynamic
| sense, and as you pointed out, is necessary to continue some
| endeavors (and maybe to permanently remove CO2 from the
| atmosphere, at a huge cost).
|
| It's these "we'll use fossil fuel energy to pull carbon out
| of the atmosphere and store it" schemes that smell like
| perpetual motion machine trickery to me.
| ryan_j_naughton wrote:
| 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-
| trai....
| X6S1x6Okd1st wrote:
| Do trains always have a connection to the grid?
| j-pb wrote:
| 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 wrote:
| unholiness wrote:
| 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.
| energ8 wrote:
| 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.
| aftbit wrote:
| If you are already adding batteries to the train to capture the
| regenerative breaking energy, why not use that same energy to
| accelerate again, therefore saving the fossil fuel energy in the
| diesel generator? Surely that would be more efficient than DAC in
| a CO2 sense?
| NegativeLatency wrote:
| Or just go fully electric overhead like they do in northern
| european countries. Some of the ore trains in the far north
| generate a fair bit of electricity from regenerative braking
| that's then used by other trains going uphill or fed into the
| local power system.
| cinntaile wrote:
| These trains in case anyone is wondering.
|
| https://en.m.wikipedia.org/wiki/Iore
| NegativeLatency wrote:
| Thanks, I was looking for them but couldn't remember the
| name
|
| > From Riksgransen on the national border to the Port of
| Narvik, the trains use only a fifth of the power they
| regenerate. The regenerated energy is sufficient to power
| the empty trains back up to the national border.
| sandworm101 wrote:
| The flip side too is that the power generated by a braking
| train is more likely to be in the voltage range needed by
| other trains in the system. It is always better the use
| electricity locally and in the same voltage rather than
| convert it to grid power.
| tonmoy wrote:
| Because the motion of the train would alleviate the need for
| large power consuming fans.
| bragr wrote:
| Which just makes the train less efficient and need more
| power? These carbon capture systems only work when the input
| energy is free (both financially and carbon-wise), but it
| seems like there's better and more efficient for uses the
| dynamic breaking energy (electric or hybrid trains).
| elil17 wrote:
| Fans are inherently pretty inefficient. If you want to
| generate airflow across a surface, it's more energy
| efficient to move the surface than it is to move the air
| (assuming you have negligible non-fluid friction, which
| trains do). Motors can be over 90% efficient. With a fan,
| you have the efficiency of the motor and then, on top of
| that, the static efficiency of the fan, which is often less
| than 50%. We use fans when it's not practical to move the
| things we want to create airflow over (which is the vast
| majority of the time). Otherwise, we use the object's own
| motion. This is the principle behind ramjets.
| adeimantus2001 wrote:
| This absolutely reeks of tech grift for the aim of poaching
| valuable research dollars.
| digdugdirk wrote:
| How/why do trains not already recapture the energy created from
| braking?
| AnimalMuppet wrote:
| Electric trains do.
|
| For the rest, they don't because of lack of storage.
|
| A diesel locomotive has a huge engine block, a generator, a
| large radiator, and electric motors on the axles. You can turn
| the motors into generators when you want braking, but where are
| you going to put the electricity? All the space (and weight) is
| already used.
|
| Yes, they have batteries - enough to crank the engine when it
| has been turned off. Not enough to run the electric motors on
| the wheels, though.
| azdle wrote:
| > but where are you going to put the electricity?
|
| Bring back the tender[0], but fill it with batteries instead
| of coal. Or better yet, intermodal container shaped batteries
| that could be swapped for pure electric long distance trains.
|
| [0] https://en.wikipedia.org/wiki/Tender_(rail)
| detaro wrote:
| Modern electric passenger trains do - they can dump power back
| into the grid, and have enough motors to do a good chunk of
| braking with them (And e.g. for the German high-speed trains
| they plan the braking points such that they try to avoid using
| lossy brakes in normal operation).
|
| If you don't have a grid as "storage", you need to carry it,
| and that's a problem. And freight trains obviously only have
| motors in the locomotive(s) and do the distributed braking on
| the cars mechanically, so a good chunk is lost even if the
| locomotive can do it.
| [deleted]
| photochemsyn wrote:
| This seems like nonsense on a conservation of energy basis.
| Putting vents on trains would cost a similar amount of energy as
| using fans to blow large volumes of air (at ~400 ppm CO2) into
| carbon-capture systems, and the result would be to slow down the
| trains and cause them to use more fuel or electricity.
|
| Secondly, who is going to pay for this? If CO2 is going to be a
| valuable commodity itself, then that's because it's going to be
| used in an industrial process as a feedstock for fuel or material
| production. In that case, train operators might find this to be
| an interesting proposition, if the value of the captured CO2 is a
| good deal higher than the resulting increase in fuel/electricity
| costs needed to operate these trains.
|
| As far as industrial production, this doesn't look good either.
| It's far easier to just put large atmospheric CO2 capture systems
| right next to the chemical production system without having to
| haul trainloads of CO2 all over the place.
| smm11 wrote:
| Snowpiercer
| ZeroGravitas wrote:
| Trains can be fairly easily electrified (via overhead rails) and
| hydridized with batteries. Generally they're diesel electric in
| the first place, so you're just switching electricity source
| which makes it a smooth transition.
|
| So I feel this will lose to batteries, which can be use to brake
| at every motor, and so can be easily distributed along a train.
| (Though you don't need batteries for regen braking, you can feed
| the power back to the grid if you have a connection). And once
| you have a decent sized battery you can charge from overhead
| lines when available, which opens up other possibilities.
|
| https://www.alstom.com/press-releases-news/2021/9/alstom-pre...
|
| > The studies have revealed, for example, that a large proportion
| of the lines currently operated with diesel vehicles include non-
| electrified sections of well under 60 miles. The use of the
| existing catenary infrastructure allows battery-powered electric
| vehicles to be operated on these lines without major upgrades to
| the existing infrastructure. Extensive travel dynamics and energy
| simulations were also carried out as part of the project.
|
| A similarly wacky concept, that I perhaps like is shipping full
| batteries to places where energy is expensive via train. So
| charge up a train battery from solar as it travels east, then
| feed that back to the grid as you meet a post sunset peak.
| Possibly wouldn't make sense if you were to do it for it's own
| sake, but if you already have a network of battery trains that
| can time their charge, you can probably save a reasonable amount
| of money by optimising when/where you charge based on time of use
| and demand response events.
|
| Coordinated Demand Response of Rail Transit Load and Energy
| Storage System Considering Driving Comfort
|
| https://www.researchgate.net/publication/347975248_Coordinat...
| lstodd wrote:
| Batteries are no-go. Typical electric locomotive is like 5MW
| sustained for multiple hours. It wouldn't be able to pull just
| its own batteries for any reasonable distance.
|
| 60 miles of catenary is way cheaper than wasting energy pulling
| dead weight that batteries are.
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