I’ve delved before into what it would take to convert the world’s car fleet to battery power with our current battery technology (spoiler: lots and lots of cobalt).
(Comments from Blogger)
2016-02-06 by Titan
Excellent article! The series hybrid design makes so much sense that I can’t believe it isn’t being done today. 100kWh sounds about right. Going over mountain passes you could deplete the battery to help the weak (250hp) diesel engine and then recover most (80% or so) of the energy going down the other side of the mountain.
2016-02-07 by protomech
A lithium titanate 100 kWh pack would be very heavy - figure around 1500 kg. Still may be okay if the tractor weighs 10000 kg, but will have to fit it somewhere.
Model S (2500 kg) uses somewhere around 0.5 kWh per 100 m elevation change. A 2000 m climb in a 30000 kg trailer would require somewhere around 120 kWh of “additional” energy beyond steady-state travel. A constant 6% grade would run for 33 km.
At 70 km/h - similar to what diesel trucks run today on steep grades - the truck would need to supply about 35 kWh for steady-state driving (70 kW) and 120 kWh for elevation gain (240 kW). Assuming 80% pack usage and 200 kW generator, a 70 kWh pack would be sufficient, assuming the navigation was aware and charged it to full prior to the ascent.
On the descent - assuming constant 6% grade - the truck would likely have to use a blend of friction and regenerative braking (absorb ~170 kW to maintain 70 km/h speed = 85 kWh total, ~290 kW to maintain 100 km/h speed = 90 kWh total).
Since uphill depleted the pack by ~55 kWh, downhill recovery at 70 km/h would completely fill the pack and require the use of friction brakes.
Worth noting this is an outlier - most interstate elevation gains will be substantially shorter or less steep (6% is max for new interstate construction) which would allow a 70 kWh pack to deliver almost all of the benefits of a 100 kWh pack, with reduced weight and slightly reduced cost ($6000 less expensive at $200/kWh, which isn’t a lot).
2016-02-07 by Titan
One thing to think about is that a smaller pack can’t supply or accept power as quickly as a larger battery. It may be necessary to have a larger battery just for the charge/discharge rate.
2016-02-07 by Russell Graves
Protomech - thank you, that’s an awesome bit of math I’d not done for the post! I sort of handwaved at it, but it sounds like a 100-200kWh pack would handle almost anything in terms of grade power, and a smaller pack would be useful for the vast majority of needs.
Titan - the power handling is one of the reasons I mentioned lithium titanate by name. It’s capable of both providing a lot of power and sinking a lot of power - most of the modern cells don’t think twice about discharging and charging all day long at a 10C rate, and the battery can provide a lot more power as needed. A 10C rate on a 100kWh battery pack is 1MW worth of charge or discharge (about 1350hp), which should be plenty for a loaded semi.
The cycle life of lithium titanate cells is also excellent - a pack should last the lifetime of the truck. The downsides are mostly relating to size and weight (and to a smaller amount cost), but those matter less in a truck that’s expected to run a million miles and is already going to be heavy for traction purposes.
I agree that you’d need a larger pack, especially for soaking regen energy, if you went with a more common lithium chemistry. But LTO is just about perfect for this application.
2016-02-08 by Unknown
Instead of a series hybrid with its power conversion losses I would suggest using a direct drive hybrid system similar to the one in the Koenigsegg Regera, it seems like it would be a perfect fit for long haul trucks.
2016-02-24 by Unknown
A massive battery pack can be split up for charging
So a battery only semi can have up to 10 chargers giving it a time equivalent to a tesla
On the hybrid
A steady speed motor can be tuned to extreme efficiency. So is a good choice
Also a battery bank can take over the refer on the trailer
Good math.
2016-03-06 by dygituljunky
Running off of a battery pack constantly isn’t necessarily the best solution.
http://w3.siemens.com/topics/global/en/electromobility/pages/ehighway.aspx
The Siemens system I linked to uses overhead wires to provide a way to turn off the generator in a series hybrid.
2016-03-09 by The Seeker
What do you think of hydraulic hybrids? Eatons had a prototype truck a few years ago, and the EPA had a development program.
2016-03-09 by Russell Graves
They’re certainly interesting, but I’d be very surprised at this point if they outperform electric hybrids. The hydraulic system had the advantage of being purely mechanical, which is useful if you don’t have control electronics that can handle large amounts of power. However, in 2016, we’ve got that worked out, and we have battery chemistries that can take a lot of charge and discharge current.
2016-03-28 by Unknown
Hi Russell, I have had the exact same basic design rolling around in my head for a long time (including the destination and terrain aware GPS system a critical component) and have come to virtually the same conclusions as you. One thing that could be added to the system for overall power unity are a bank of super capacitors. Super capacitors are light weight and have the ability to absorb charge very quickly, much faster than a battery can. So adding this element can give power somewhere to go when the vehicle needs to slow quickly. Super capacitors also have the ability to return supply big bursts of power, ideal for getting back up to speed after a full stop.
As for the main power unit there are a lot of new engine technologies that are coming to market some reaching reported thermal efficiency of up to 52% http://www.motivengines.com/
Here is another promising engine tech, the opposed piston engine and its light modular design http://ecomotors.com/
And though some will say that this guy and his power amplification technology is a nutter, I think it may be worth looking into as there is a lot of suppressed tech out there. If this tech is real and can be commercialized it solves all power issues out there. Thus the reason to suppress this type of tech. Groundbreaking Discovery: Man Solves Tesla's Secret To Amplifying Power By Nearly 5000%
Then there are all the Stanley Meyer patents with relation to resonant frequency water fracture technology and the high voltage low amperage production of Hydrogen and Oxygen. http://www.rivendellvillage.org/Stanley_Meyer_Resonant_Electrolysis_Cell.pdf
If these exotic techs are too much to wrap your head around then one can look at waste-heat recovery systems that can be teamed with any type of ICE or turbine engine system to recover some of the lost heat to steam and a secondary power unit. http://www.calnetix.com/access-energy-thermapower-orc-systems This link does not show a vehicle optimized system but gives an idea of what is possible with development.
These are just a few ideas that I have for long haul trucks to improve efficiency. Feel free to contact me. I would love to be become more actively involved in this field.
Allan
electrifiedtruck@gmail.com
2016-06-17 by Russell Graves
Long haul trucks are very long lived, and require levels of proven reliability that are hard to achieve without serious miles on the road.
I expect we’ll see more over time, but the battery technology has only, in the past 5 years or so, hit a point where this is even feasible, and trucks are on the road far, far longer than just 5 years.
2017-11-22 by EugeneGTI
Would be curious of your thoughts on the Tesla truck 
2017-11-23 by Russell Graves
I think they’re going to have to prove they can build a reliable, maintainable vehicle for it to have much of an impact. Enough companies have ordered small test fleets that it will be really obvious in a hurry how they hold up and how they’re maintained.
Fleets won’t go for the “Well, you have to take it to the Service Center for everything…” style maintenance Tesla has gone with so far, but I don’t think that’s a huge hurdle (just a mental jump for Tesla).
But, really, it’s going to come down to how reliable the whole vehicle is. I’m not particularly concerned about the drivetrain - Tesla has done a very, very good job with the engineering on the battery pack, power electronics, and motors (the bulk of “motor replacements” were almost always because it was quicker to just swap the unit out for a minor issue than to pull it apart and fix the lubrication issue). It’s rare to see an issue with those. The rest of the cars, on the other hand, are a hot mess in terms of things actually working and lasting - and that’s with fairly careful owners proud of their $100k toys. A daily use fleet truck gets treated an awful lot rougher, in much worse conditions, and I’m somewhat skeptical that Tesla actually understands that well enough to build a machine for it.
I will be interested to see what the actual power consumption numbers are, compared to my estimates. One thing I didn’t consider in my estimates here is cooling drag - the diesel demonstrator still requires a lot of cooling airflow, and I don’t know how that compares with the total drag of the combo.
Another area that will be interesting is how the Tesla semis handle gusting crosswinds in terms of range - that really, really increases the drag on most vehicles.
2018-08-08 by Unknown
I think you have taken the wrong approach here. you need to have the batteries in the trailer with Solar panels on the top of the trailer. This way the trailer can be parked and a charged trailer can be attached and the off the truck goes again.
The trailers can be charged at the depots or via the solar on the roof (all be it at a much slower pace). If you can get 600 miles out of a charge on the trailer you would be able to have regional depots where fright is handed off to charge and the truck is kept in almost constant motion.
2018-08-09 by Russell Graves
Solar panels on a trailer are mostly a waste of weight, and (worse for stability) weight up high. And they are aimed wrong for everything but peak summer, and even then aren’t exactly right unless you’re very far south.
Solar panels on a vehicle are, almost always, the wrong answer. Put them on the ground where they’re able to be the lazy lizards they like to be, soaking in the sun.