26 mpg for a HDV with a probable GWR of ~20,000 lbs is real good!
I wonder when will our "soccer mom's" 6000-lb SUV at ~14mpg rating will ever get even close to this? With GM's dual-mode hybrid's 40% improvement in efficiency, expect under 20 mpg. I know, I know, acceleration performance costs mpg's, and the main reason for the 14-mpg ability of the SUV is that humongous 350-450 hp engine driving a 6,000-lb vehicle. While the same 400-450-hp level is sufficient for a 80,000-lb 18-wheel tractor trailer!

The solution for meeting future fleet CO2 goal is right under our nose: reduce acceleration performance in exchange for higher mpg's, fewer hi-tech wizardry to save money and energy at the same time.

May be there should be an addendum to the CAFE regulation, limiting maximum acceleration performance 0-60 mph time to SLOWER THAN 12-14 seconds for passenger-class vehicle, excluding police cars. More safety, too, since this will keep the boy-street-racer at home in his X-box 360 instead of on the road!

May be there should be an addendum to the CAFE regulation, limiting maximum acceleration performance 0-60 mph time to SLOWER THAN 12-14 seconds for passenger-class vehicle, excluding police cars.

Oh, come on, Roger; this is silly. If you want better gas mileage then legislate that. Limiting acceleration to a snails pace will never fly.

@ George -

any limit on acceleration would indeed be impossible to police. However, the Japanese kei car class proves that it is quite possible to create demand for small econoboxes using market externalities like license fees and parking restrictions.

That particular class definition wouldn't make sense in the US, but the idea could be adapted. For example, a strictly limited number of hybrids was given carpool exemptions in California, which did boost demand for the vehicles.

0-60mph @ 12 seconds is pretty fast, not snail pace. My GM Caprice 1978 MY (Impala), 5.6 liter V-8 with 4Barrel Carburetor, was one of the faster vehicle in its days, capable of 0-60 in 12.6 seconds, and it felt pretty fast, compared to 1.5 liter imports having 0-60 times @16-18 seconds. I can feel by back pressed against the seat. I had to retard the engine timing to prevent engine knock since I used cheap 87 Octane gas. Check out the Nissan Sentra of similar model year , circa 1978-1980, you'l find 0-60 around ~18 seconds, and that was perfectly adequate. Even the highly touted Honda Civic (CVCC) in those days were real fast at ~12 seconds 0-60.

If EPA can test a car for mpg, it too, can test a car acceleration performance by flooring the gas pedal to see how fast it will go. Any car capable of accelerating faster than the regulated limit will be subjected to "high-performance tax", severe enough to discourage that wasteful capability.

@ Roger Pham -

and every manufacturer would ship their cars artificially neutered so tuning shops could get the power back up again.

Either you pick a parameter that's hard to change substantially - like vehicle length and width, as with kei cars - or you make fuel seriously expensive as in both Japan and Europe.

Hi Rafael,

Thanks for your thought on the subject. Admittedly, this idea of mine is rather silly and not the smartest.
Testing for CO2/km or mpg or liter/100km would be the standard. But, then, one would argue that bigger car that can hold more people should have different standard requirement.
The EPA should test the vehicle as available randomly in the dealer's lot, not as supplied by the company. Anything the tuning shops can quickly do to improve the car,or "deneuter" it, the EPA can do the same to see if their rules can be easily violated.
In the Far East, the strategy is to tax heavily higher-displacement cars, and this has been working, but it can also be argued that the little mighty mite powerhouses have been stuffed with all kinds of costly performance boosting wizardry which, in the end, will be costly and won't save gas that much!

Alas, this is not a perfect world and there's no perfect rule.

At this point in history a breakthrough on batteries is either just around the corner, or already here and in need of economies of scale.

Leadership on replacing ICE with electrics or PHEVs is what is needed. Vote.

Elliot,
PHEV or BEV won't work for Heavy Duty Vehicles (HDV) as featured in this article, for the obvious reason of high cost and weight of the battery pack.

PHEV and BEVs are more suited (economically speaking) to HDVs than passenger vehicles because a far greater proportion of the operating costs of HDVs are fuel, and so potential savings from switching to electric are much greater.

A typical 40-tonne goods vehicle will go 100,000 miles a year at only 8 mpg. Here in the UK that would cost around £56,000 in diesel. As the electricity for the electric version would only cost around £14,000, the operator could save £40,000 per year, making back the cost of a 1MWh battery pack in around 6 years.

Clett,
You've got to indicate what type of battery used and how much the battery electricity will cost per kwh factoring in the amortization cost of the battery as well as the cost of grid electricity per kwh.

As it is now, battery electricity will cost a lot more per mile driven than petroleum fuels. Plus, what is the range and recharge time of the BEV? And what percentage of the battery weight and volume will cut into the cargo carrying capacity, hence decreasing productivity?
Do the math, Clett!

http://mysite.wanadoo-members.co.uk/ecotech/hgv1.htm

i need info on batteries.

Clett,
I have a different set of data for 80,000-lb tractor-trailers: I got 0.33 mi/kwh instead of the 0.6 mi/kwh on your referred website. This is how: Most truckers reported 5 mpg for their 80,000-lb rig. One gallon of diesel fuel has 37.5 kwh of thermal energy, and at 42% thermal efficiency of the turbodiesel truck engine, one gallon is equivalent to 15.75 kwh of shaft work output.

Due to the electric-motor-batter having an aggregated efficiency of ~75% at the motor's shaft for lithium battery, the amount of battery required would be higher, so 0.33 mi/kw x .75 = 0.24 mi/kwh of electricity from the battery!

For a 700-mi daily range, you will need 700/0.24mi/kwh= 2916 kwh of battery. For A123 Lithium battery at ~125 wh/kg, the battery weight will be 2916 kwh/0.125khw/kg= 23,333 kg weight of battery! Let's say $500/kwh, you'll be paying 1.5 Million USD for those batteries.

Clett, this is over twenty three tons, or 51,000 lbs, battery weight for a 80,000-lb vehicle. This will reduce your payload to ~15,000 lbs the most.

Like I said, Clett, DO THE MATH! Don't believe everything you've read on the NET.

Oh, Clett,
in the UK, you guys are using Imperial Gallon, while in the US, we use US gallon which has smaller volume, ergo the discrepancy from what the truckers got here @ 5 mpg to what the UK truckers are getting (~7 mpg). But, the number of mi/kwh ought to be the same. So, 5 mile/US gallon = 15.75 kwh at engine shaft. This is equal to 0.333 mi/ kwh at engine shaft. The mi/kwh at the wheels will be slightly higher, due to losses in the transmission, albeit small. The electric truck version will also need a transmission, albeit a simpler one, but still suffer from some losses in the transmission as well.

The easiest way to convert between miles per gallon and miles per kWh is to look at a vehicle that has a gasoline, diesel and electric variant (mainly hobbyist conversions). For example, a gasoline Golf will do about 40 mpg (UK), a Golf TDi will do 50 mpg (UK), but an electric conversion Golf would manage about 5 miles per kWh if using lithium.

So to get miles per kWh from mpg, a general rule of thumb is to divide gasoling mpg by 8, or diesel mpg by about 10.

Our HGVs get about 7-8 mpg (UK), so should manage 0.7-0.8 miles per kWh on electric.

For a 700 mile range, you'd need 875 kWh, which if using 200 Wh/kg Electrovaya packs would weigh in at about 4.4 tonnes, or 10% the weight of the vehicle. If using the Manganese series 330 Wh/kg Electrovaya packs, the HGV battery would come down to 2.6 tonnes.

http://www.greencarcongress.com/2007/01/electrovaya_to_.html

In terms of potential costs of lithium-ion, please refer to this document, page 34:

http://www.transportation.anl.gov/pdfs/TA/149.pdf

Which shows that a 8 Wh standard 18650 battery currently costs about $1.70 to manufacture ($212/kWh) if using expensive cobalt chemistry. Electrovaya's manganese chemistry should be a good bit cheaper than this.

Clett,
Please realize that the VW Golf's engine has much lower thermal efficiency than a typical tractor-trailer rig, at 18% for gasoline and ~25% for the diesel version, while the large tractor-trailer runs its engine much at the time at its optimal thermal efficiency of 42% by constantly shifting gears to optimize the engine's torque load.
In the case of the Golf, 50 mpg (UK) means that the car travels 50 mi while consuming 45 kwh of thermal energy per Imp Gallon, or 1.11 mi/thermal kwh, while in electric mode, it consumes 4.1 mi/kwh (Per the website), implying a thermal efficiency of 1.11/4.1 = 27% ? Not quite, since there is ~20% loss in the electric version via the battery-controller-motor route, you have to multiply the 27% by .80 to get 22% ? . This is a 22% thermal efficiency at the wheel, which correspond well to our estimation of 25% engine efficiency, with 3% thermal efficiency loss via the transmission. See, the real number is far from easy or simple.

If you would apply the correction factor of 25/42 for the two different vehicles having vastly different engine's thermal efficiencies, you would divide 7.5 mpg(UK) by 12.8 = .58, according to the website, and multiply 25/42 = 0.35 mi/kwh. BTW, when you said the Golf can travel 5 mi/kwh, does this means kwh at the motor shaft, or at the battery output terminals, or at the grid socket going into the charger? Since there are losses for each step of the way, one cannot size the battery pack unless one would assume that 5mi/kwh from the battery terminals.

So, for 700-mi range at 0.35 mi/kwh, you will need a battery of 2000 kwh capacity. Since GM is using A123 battery at ~125-130 wh/kg in order to have sufficient durability and cost-effectiveness for the long haul, you should do the same, or else GM would have chosen lighter and cheaper battery chemistries.

So, at 2000 kwh, your pack will weigh 15,625 kg, or 34,375 lbs, or 17 tons out of the truck's 40 tons capacity. See how much loss of productivity this would be! For a payload capacity of ~32-33 tons from the truck, the battery has now decreased the payload capacity to over 1/2!

"the VW Golf's engine has much lower thermal efficiency than a typical tractor-trailer rig, at 18% for gasoline and ~25% for the diesel version"

This is not correct. VW report 42-43% peak thermal efficiency for their 1.9 TDi engines and (unlike gasoline) high efficiency is available over a wide operative map.

The 4.1 miles per kWh reported on the website is for lossy lead-acid based conversions. Newer lithium-ion has 98%+ efficiency and Golf-sized vehicles with LiIon installed easily go 5 miles per kWh.

There is an easy way to decide whether the claimed 0.6 miles per kWh is realistic for an HGV. Assuming an average speed of 60 mph, the HGV would travel 60 miles in 1 hour and therefore consume 60/0.6 = 100 kWh of energy. Average power for 60 mph is therefore 100 kW, or about 140 horsepower. Is 140 hp enough to keep an HGV moving at 60 mph? They do have much higher peak power outputs but that is to cope with grade, so I think it is.

Remember we already have electric delivery trucks here in the UK (Modec). They are reporting 1.4 miles per kWh on the worst duty cycle (fully-laden, stop-start use), while equivalent diesel vehicles manage around 15 mpg for the same cycle, so the EV/diesel conversion seems accurate.

Clett,
Don't be fooled by the claim of peak efficiency of a car engine. Due to the fact that cars are always grossly overpowered in comparison to HDV trucks, car engines do not get to operate it their peak efficiency regime during normal cruise. I've given you the PROOF that the Golf's engine operates at only ~25% efficiency in the last posting. I'll now repost that part here:

>In the case of the Golf, 50 mpg (UK) means that the car travels 50 mi while consuming 45 kwh of thermal energy per Imp Gallon, or 1.11 mi/thermal kwh, while in electric mode, it consumes 4.1 mi/kwh (Per the website), implying a thermal efficiency of 1.11/4.1 = 27% ? Not quite, since there is ~20% loss in the electric version via the battery-controller-motor route, you have to multiply the 27% by .80 to get 22% ? . This is a 22% thermal efficiency at the wheel, which correspond well to our estimation of 25% engine efficiency, with 3% thermal efficiency loss via the transmission. See, the real number is far from easy or simple.

Truck engines,on the other hand, must operates at peak efficiency during cruise since fuel cost is a major operational expense for any carrier company.

>"Remember we already have electric delivery trucks here in the UK (Modec). They are reporting 1.4 miles per kWh on the worst duty cycle (fully-laden, stop-start use), while equivalent diesel vehicles manage around 15 mpg for the same cycle, so the EV/diesel conversion seems accurate."

Due to braking regeneration of energy and low speed travel, city duty cycle actually gives much higher mpg for electric vehicles than for ICE. The Prius manages 61 mpg for city but only 51 for hwy. The Honda Civic Hybrid manages 49 mpg for city and 51 for hwy, whereas the gas Civic does much poorly in city driving than hwy.

A 15-mpg-city driving will translate to a ~23-25 mpg hwy driving for a typical ICE vehicle. A 1.4-mi-kwh city BEV will go less far for hwy, may be 1 mi/kwh hwy driving, while making 23-25 mpg hwy in the diesel ICE version, so for diesel HDV, you must divide the hwy mpg by 25 in order to get the mi/kwh for the electric version! (while for LDV diesel, divide hwy mpg by 12.8 as per the website)

OK, let's talk about highway miles per kWh only. I reckon 0.6 miles per kWh at 60 mph, which is equivalent to an engine output of 100 kW.

The question is: is 100 kW sufficient to propel a 40-tonne HGV at 60 mph? If it is, then 0.6 miles per kWh is correct.

Let's do the maths for power required at 60 mph. There are two main components to drag, aerodynamic and rolling resistance. The power to overcome these can be calculated using the following formulae:

Aero = 0.25 x p x v x v x v x Cd x A
[Cd=0.52, p=1.293, Frontal area A=9]

Rolling = Cr x m x g x v
[Coefficient of tyre rolling resistance Cr=0.0061, m=40,000 kg, g=9.8]

I have chosen to use the figures for coefficients etc taken from a comprehensive recent review of real-world HGVs:
( http://www2.vito.be/cost346/files/346_119.pdf Page 102,104)

Using values for a typical 40-tonne HGV gives power requirements at 60 mph (26.5 metres per second) of:

Aero = 0.25 x 1.293 x 26.5 x 26.5 x 26.5 x 0.52 x 9 = 28,152 W = 28 kW

Rolling = 0.0061 x 40,000 x 9.8 x 26.5 = 63,367 W = 63 kW

So total power required to propel a 40-tonne HGV with maximum payload at 60 mph is 91 kW. This is equivalent to 0.66 miles per kWh, which is in good agreement with the other method of calculation.

Clett,
So, for the VW Golf weighing at ~2900 lbs, or 1.3 tonnes, then the rolling resistance power would be: 1.3/40x63= 2.04 kW...Rolling resistance does not vary much with the size of the vehicles, only with the quality of wheel bearings used and the ratio of the wheel size to bearing size, and tyre rolling resistance. For aerodynamic power, the general rule of thumb at 60 mph for aerodynamic resistance is almost equal to the rolling resistance for a typical passenger car, so the total power required to propel the Golf is only 4 kW at 60 mph? You know that that's too low, because then, the car will be capable of 15 mi/kWh, and we know that that is not in keeping with the real-world number of 4.1 mi/kWh.

It matters not what type of battery is used to get the 4.1 mi/kWh, if the mi/kWh is taken at the battery output terminal.

A much more reasonable number of <0.3 mi/kWh for the 40-tonne HDV truck will result in the Golf capable of 7.1 mi/kWh, which is closer to reality, given the fact that truck tyres are inflated to ~100 psi and thus having lower rolling resistance.

Again, Clett, double check your math for the HDV numbers, or try to obtain real-world numbers for HDV from a trucking company.

Since we already know the operating thermal efficiency for truck's turbo-diesel engine at close to ~42% for hwy duty cycle, and truck's hwy mileage at ~7 mpg (UK), retro-calculation of this will give you the kWh requirement at the engine shaft. Dividing this with the efficiency of the motor-controller and you will get the actual kWh of electricity at the battery terminal required per mile.
Thus, 45 kWh/Imp gallon x .42 /7= 2.7 kWh/mi at engine shaft, dividing this by 0.8 efficiency factor for motor-controller will give you 3.375 kWh/mi at battery terminals, or 0.29 mi/kwh for sizing of the battery pack, so this is right on the ball.

"Clett, double check your math for the HDV numbers, or try to obtain real-world numbers for HDV from a trucking company."

The HDV numbers I used are from real-world existing vehicles as per the cited technical review paper.

You are wrong to compare the aero/rolling resistance between a passenger car and a HGV in the way you have. The coefficient of rolling resistance of an HGV is much lower than that of a road car, which uses tyres more optimised towards grip, handling and comfort.

The golf you suggest uses tyres with a Cr of around 0.015, whereas the HGV can use tyres offering a Cr of 0.0052. This would give a power at 60 mph for a Golf of:

Aero = 0.25 x 1.293 x 26.5 x 26.5 x 26.5 x 0.34 x 2.2 = 4,499 W = 4.5 kW

Rolling = 0.015 x 1,500 x 9.8 x 26.5 = 5,843 W = 5.8 kW

Total power for the Golf at 60 mph is 10.3 kW (14 hp), or about 5.8 miles per kWh.

The math does add up for both the HGV and the Golf!

Clett,
Truckers I've talked to all said that they need to use 1/2 to 3/4 power to maintain cruise. These vehicles are rated at ~450 hp, so it takes ~200 kW or so to maintain cruise, not the lowly number of 100 kW that you're stating. How do you argue against real-world testimonies from real truckers? How do you argue against the calculation method using well-known engine operating efficiency rating? Eitherway, the numbers matched in my method.

The energy wasted in the suspension due to uneven road surface is not accounted for from just the rolling resistance alone. The heavier the vehicle, the more energy will be wasted in the suspension heating up.

Also, the following is a link to the official Caterpillar site for the C13 engine, rated at 430-470 hp. The mfg recommend at 65 mph for a 80,000-lb truck or under, the engine to be run at top gear at 1400 rpm at 1650 lb-ft of torque, equivalent to 430 hp. This my friend, is pretty close to 200 kW power requirement to cruise at that speed.

http://ohe.cat.com/cda/files/378804/7/LEHT4569-09%20HR%20P2.pdf

This a direct quote from that pdf file:

"For the best balance of performance and fuel
economy, spec axle ratios and tire sizes
according to the following:
• 80,000 lb GCW or less
430 hp, 1650 lb-ft:
1400 rpm @ 65 mph (105 km/h)
test methods.

This is proof enough...real-world recommendation from engine maker themselves.
Look at the engine torque and hp curve on the preceding pages : if only 100 kW is needed for cruise at 60mph, then the mfg would have recommend setting the rpm at 850-900 instead of 1400 for cruise at 65 mph, since maximum 430 hp is smack at 1400 rpm!

The Caterpillar pdf indicates what maximum power of engine you should choose for each vehicle, it does not indicate what power output will be at 65 mph because although it suggests using 1400 rpm for optimum efficiency, it does not say how much throttle is used at that speed.

Engines for HGVs must be capable of outputting much more than the power required for cruising because it takes vastly more power to accelerate a 40-tonne load or to haul it up even a modest gradient than it takes to pull it at steady state speed on the flat.

I think only about a third of the rated power would be used at cruise, or about 100 kW. All of the remaining power that CAT suggest you should buy is required for accelerating or going up grade. Proof of this lies in the fact that a steady 60 mph will net 7-8 mpg, while stop-start traffic every 100 metres yields less than 1 mpg.

For example, look at how much power it takes to haul a 40-tonne load up an average 1:30 gradient at 60 mph: That's 0.87 ms-1 vertical, Power to overcome gravity only = mgv = 40,000 x 9.8 x 0.87 = 341 kW. This is why HGV engines are grossly oversized compared to the amount of power required to propel them at 60 mph on-the-flat.

Clett,
If only 100 kW is needed for level cruise at 60-65 mph, then the C13 engine will need to turn only 900 rpm at cruise at 60-65 mph, and still has a good margin for further acceleration, given the fact that at 100 kW, or 134 hp, the C13 engine will need to turn only ~750 rpm. Turning the engine at 1,400 rpm when only 900 rpm is needed is never done in the trucking industry because this wastes a lot of fuel and increases engine wear. Just check this out with any trucking company.

Unlike a passenger car, these trucks have a lot of gear ratios in their transmission, something like 12-15 gears to shift in order to put the engine at the point of maximum thermal efficiency. Driving these trucks, you would want to shift to the tallest gear ratio as soon as cruise speed at level grade is reached in order to conserve fuel and to reduce engine wear at higher-than-necessary rpm's. To accelerate, you will need to downshift, since cruising at tallest gear ratio means that you don't have much torque reserve left for acceleration, but when you downshift, the engine torque will be magnified by the transmission, giving you the needed force at the wheel for acceleration. A CVT or IVT would be nice to avoid gear shifting, but the torque requirements of these trucks much exceed any conceivable CVT or IVT design known today. The large number of gear ratios of the transmission and the prompt upshift-downshift in response to torque load demand simulate the main advantage of a CVT, with much lower transmission internal friction in comparison to a CVT.

Accept it, Clett, truckers told me that their 80,000-lb rigs need 1/2 to 3/4th of ~450-hp engine power for hwy cruise, and that their rigs average about 5 mpg (US) or 6 mpg (UK).
This translates to ~200 kW of power for cruise at 60-65 mph, and that this is equivalent to ~0.25 mi/kWh with 80%-efficient motor-controller, or ~0.29 mi/kWh for trucks that can make 7 mpg (UK) according to your website.