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Kia calls for more government investment in hydrogen

Discussion in 'General Kia EV Discussion' started by dpeilow, Sep 20, 2016.

  1. Siraff

    Siraff Well-Known Member

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    Not just that but overall cost and messing with drivers' hours, etc would make it a complete nightmare even in the best of cases. In reality a 38t+ truck is going to use a fair bit of energy. They tend to hover around the 4-6mpg area when cruising and each of those gallons has just over 50kWh in it. The usual driving stint is as close to 4.5 hours as possible so we'll say 4 hours minimum at 50mph average so 200 miles per stint. That's about 40 gallons of diesel or 2000kWh's in the first half of the day ignoring shunting/reefer power.

    I think there is a place for battery power in trucks but it's more supplemental than outright because that's what current tech allows.
    Have an electric motor powering the wheels on one drive axle and a (very) small diesel powering the other drive axle. There would be a secondary generator to act as a rex and a battery. The idea being the small diesel can power the truck for cruising speeds so it only needs to make an efficient 250hp or so. The electric motor would take feed from the battery and provide the other 250hp for acceleration and gradient pulls. The battery power would be partially supplied by charging while stopped, partially by regen and would have the generator to back it up as a last case is nothing else was available.
    The generator being the same power means the truck can never have less than 500hp available at any one time but also means it's using a much more efficient driveline for most of it's time - ev/rex equivalent while pottering through busy traffic, small diesel for long distance cruising and enough power/range to drag anything anywhere that a normal truck would be expected to do.

    Obviously you could size any of the units to suit use so long as the generator has enough power to completely feed the second motor if need be.

    Another option would be two generators and two electric motors either matched or a big and little. Add in a reasonable battery and pick a power level.
     
    Neilew likes this.
  2. BlackLeaf

    BlackLeaf Well-Known Member

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    Yes I agree, although I would go further and have no diesel on the drive axle but instead two (identical) electric motors, one on each drive axle. Then use regular diesel-electric propulsion as already well proven on the railways for the first axle. And Battery-Electric for the second axle. Keeps it nice and simple and makes the mass-production scale better.
     
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  3. dpeilow

    dpeilow Militant EV driver!

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    Your numbers don't take account of inefficiency in the ICE drivetrain.

    Looking at some of the power ratings of HGV tractor units, 250 kW seems to be about right. Assuming the usual depth of discharge on a 600 kWh battery gives 500 kWh usable, the truck could operate for 2 hours at 100% power. Of course they don't operate at 100% power all the time, so 4 hours operation doesn't seem out of the question.

    A 600 kWh battery using Tesla packs would be <3.5 tonnes. Losing the engine and ~1 tonne of diesel would offset some of this, so overall it's not ridiculous to propose such a battery or maybe even larger. It might be better to use a Lithium Titanate battery like the ABB flash charging bus, as they can be charged extremely quickly and have much higher cycle life. Such a battery would weigh around 5 tonnes but would not have the same conservative depth of discharge.

    It would be interesting to look at the business case to do a battery swap or even tractor unit swap every couple of hours, given the potential fuel savings. For a large logistics company, it doesn't seem daft to put in a network of swap stations.


    However this report suggests that >45% of HGV CO2 emissions are from long haul and international point to point deliveries and we already know how to deal with that...

    StobartRail 5.JPG
     
    Matt Beard likes this.
  4. BlackLeaf

    BlackLeaf Well-Known Member

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    Electrify the motorways and fit pantographs to the trucks :)
     
    Siraff likes this.
  5. Siraff

    Siraff Well-Known Member

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    Not quite sure how huge a system would need to be to cope with the loadings but I think that's by far one of the most sensible options if we ignore cost and places where there aren't motorways for large distances.
     
  6. Siraff

    Siraff Well-Known Member

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    250kW is around 330hp. It would be very unusual to see a truck of such low power regularly pulling 30+tonnes these days. That's more the kind of power level for an 18 tonner. For large loads it's usually at least 450+ with most being between 500 and 650 then a few higher again.
    I didn't bother going into thermal losses because some of that is regained by having free heat for the cabin and I also didn't bother adding on the energy use for a reefer/etc so it works both ways.
    I think you're stretching it more than a lot using a 330hp engine as an example then saying it's going to average 50% power over 4 hours. A 330 pulling a full size trailer even at 26t would be in the last dregs of what it could muster for quite a lot of the time and would also take longer to get where it was going on all but the most level runs.

    If you could drag it with an average of 165hp I think the companies would catch on and save themselves a bit of money fairly quickly.
    Of course this is all on a nice, flat road with very little change. Even a headwind on these things can cost you 40% again on the fuel bill.

    I don't think you've quite grasped just how power hungry they really can be.

    Next time you see something like an FH16 dragging a loaded freezer trailer up a hill at 56mph just have a think about the forces involved. That's upto 44t of 8ft wide, 14ft tall being hammered along while keeping well over 3000cubic feet of drumsticks icy and needs to be able to do that for 4.5 hours with some left if need be - sometimes in the rain/headwinds/whatever.

    I like the li-ti idea (best batteries about) but the 600kWh one is many, many miles off.
     
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