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Walmart showcases WAVE tractor-trailer at MATS; micro-turbine range extended electric vehicle with 45.5 kWh Li-ion pack

Walmart showcased its Walmart Advanced Vehicle Experience (WAVE) at the Mid-America Trucking Show (MATS) in Louisville, Ky. WAVE is a tractor-trailer combination that features leading edge aerodynamics; an advanced turbine-powered range extending series hybrid powertrain; electrified auxiliary components; and control systems.

The project aims to demonstrate a wide range of advanced technologies and designs Walmart is considering in an effort to improve the overall fuel efficiency of its fleet and lower the company’s carbon footprint. Although the prototype currently runs on diesel, its turbine is fuel-neutral and can run on compressed or liquid natural gas, biofuels or other fuels.

Walmart-advanced-vehicle-experience-wave-concept-truck
Walmart Advanced Vehicle Experience. Click to enlarge.

The prototype is the result of collaboration between Walmart and many vendors, including Peterbilt, Roush Engineering, Great Dane Trailers and Capstone Turbine.

Tractor. Walmart and Peterbilt have collaborated on aerodynamic, hybrid, electrification and alternative fuel projects in the past, each with incremental gains in fuel efficiency and emission reductions. The Walmart Advanced Vehicle Experience tractor combines many of these projects in a single vehicle.

Powertrain. WAVE is a Range Extending Series Hybrid that features a microturbine Range Extender generator developed by Capstone Turbine Corporation. The micro-turbine is fuel neutral and produces very low emissions without the need for aftertreatment. Turbines are also appealing because of their few moving parts, low maintenance requirements and lighter weight.

Range extending hybrids are a synergy between electric trucks and series hybrids, and their design reduces the energy storage size required for trucks to run on batteries alone.

With Walmart Distribution Centers now located closer to metropolitan areas, transport vehicles have shorter transit times to their delivery destinations. These shorter trips reduce the vehicles’ average trip speed and create more opportunities to recover energy through regenerative braking. The generator and energy storage on the truck are scalable based on the range desired.

Capstone also engineered the truck’s integrated hybrid drivetrain solution. The use of a hybrid powertrain allows the turbine to remain at optimum operating rpm, while the electric motor/energy storage handles acceleration and deceleration. A longer-range version of this powertrain would feature a larger turbine and smaller energy storage system.

WAVE-ops-modes
WAVE features three operational modes: charge, EV, and hybrid.
  • Charge Mode: When keyed on, the truck automatically detects the state of charge of the batteries and starts charging them, if needed, using the turbine engine. Charge mode can be manually selected if an operator wishes to “top off” the batteries prior to shutting down.

  • Electric Vehicle Mode: For use in urban areas, the truck will run on electric power alone until the battery state of charge hits 50%. At that time the turbine will automatically start and begin charging the batteries.

  • Hybrid Electric Mode: For maximum range, this mode runs the turbine continuously, only shutting down if the batteries run out.

Click to enlarge.

Vancouver (Canada)-based Corvus Energy is the Energy Storage System supplier for the truck. In each truck, there are 7 lithium polymer battery modules (96V) to provide 650 VDC for a total of 45.5 kWh. The system includes both the traction, braking, and control elements. The energy storage system is also used to supplement the generator and buffer the power for the accessory systems.

The batteries are sized to provide power for the truck’s systems when the vehicle is waiting for a few hours to drop off a load. Batteries also power the vehicle in a pure electric mode (w/o generator) for limited miles of stop and go driving, such as what might be found in a busy shipping terminal or traffic jam.

Component Electrification. With automobiles moving to electrified accessories such as power steering and air conditioning, this truck scales those systems up for use on a larger vehicle. These electrified components are used only when needed and at peak efficiency.

Aerodynamics. Designers used extensive computational fluid dynamics (CFD) analysis to optimize the truck’s styling. The truck’s shape represents a 20% reduction in aerodynamic drag over Walmart’s current Peterbilt Model 386. By placing the cab over the engine, the truck’s wheelbase is greatly shortened, resulting in reduced weight and better maneuverability.

Further, with the air-cooled microturbine, there is no need for a large radiator in front of the vehicle.

Walmart relied on product development supplier Roush Engineering to carry out the vehicle’s construction.

Trailer. The vehicle’s trailer, manufactured by Great Dane Trailers, offers a host of fuel-saving features. The trailer body is built almost exclusively with carbon fiber, including one-piece carbon fiber panels for the roof and sidewalls, saving nearly 4,000 pounds (1,814 kg) when compared to traditional designs. The trailer’s convex nose also enhances aerodynamics while maintaining storage space inside the trailer.

Other special features of the trailer include special low-amperage LED lighting strips, composite trailer skirts, aerodynamic disc wheel coverings, a Posi-lift suspension, and a one-piece, fiberglass-reinforced floor panel with a 16,000 lb (7,257 kg) forklift rating.

A number of vendor partners were involved in the design and creation of the Walmart Advanced Vehicle Experience. Key partners—in addition to Peterbilt Motors Company, Roush Engineering, Capstone Turbine Corporation and Great Dane Trailers—include Qualnetics Corporation; Allison Transmission; Transpower; New Eagle; Fiber-Tech Industries; Grote Industries, Inc.; Laydon Composites Ltd.; Isringhauser Seats; Graykon, LLC; Dometic Corp; RealWheels Corp; Corvus Energy; Parker Hannifin; Accuride; Milliken Chemical; SAF-HOLLAND USA Inc.; and Whiting.

In 2005, Walmart, one of the nation’s largest private fleet operators, announced its goal to double fleet efficiency by 2015. As of last year, the company had achieved an 84% improvement in fleet efficiency over its 2005 baseline.

Walmart is continually looking for innovative ways to increase our efficiencies and reduce our fleet’s emissions. The Walmart Advanced Vehicle Experience is a bold step in transportation technologies that, although not on the road in its current form, will serve as a learning platform for the future that will accelerate our progress toward our goals.

—Tracy Rosser, senior vice president of transportation at Walmart

Comments

Roger Pham

@Bernard,
The following reference, published in 2001, shows that:
"The evidence from numerous researchers suggests that the engine cooling system is responsible for between 10% and 15% of the overall vehicle drag."

http://books.google.com/books?id=36kg2DJiy7cC&pg=PA120&lpg=PA120&dq=cooling+drag+of+cars&source=bl&ots=JWgHECC9gs&sig=wCwN1iz9M88auKq8j0IAwhtE8aM&hl=en&sa=X&ei=AdI6U6z5HcLWyQGaiIDYCg&ved=0CGIQ6AEwCg#v=onepage&q=cooling%20drag%20of%20cars&f=false

That is, 10-15%, BEFORE aerodynamic optimization, that allows air to flow in and out freely of the radiator and the engine bay.
Aircraft engine cooling is much more efficient. Look at, for example, the cooling of the P-51 Mustang WWII fighter,in which air flows in thru a narrow NACA intake duct, compressed and slows down substantially while increasing in pressure substantially due to slowing down, according to Bernoulli theorem, takes up the heat from the radiator and expands, and exits thru the exit duct with increasing in volume due to the nozzle effect of the exit duct...and lo and behold...actually, adding to the thrust of the aircraft...essentially, the belly radiator of the P-51 aircraft is acting as a heat engine like a turbojet in principle, in which intake air is compressed as it slows down, heated to increase in volume, and exit thru a nozzle to re-speeding it to gain thrust, due to the expansion of the air from heating. Of course, the much colder air of 220 K degrees at the altitude that the aircraft is cruising in contrast to the temperature of nearly 350 degrees K of the radiator will add much more thrust than the much higher ambient temperature that a car or a truck is operating.

However, the above is to show that a proper cooling air intake, channeling, and exhaust may even add thrust to the vehicle, or at least, exacts negligible drag penalty. It's all in the aerodynamic design.

Bernard

Roger,

I guess that this is the closest you get admitting that you made-up a "fact". You've re-estimated from <1% to 15%. My sources say 1/3, but at least you are now within an order of magnitude.

Aircraft travel through colder air at much higher speeds. They also operate close to their design load all the time (operators hate empty seats). That makes the job of cooling them much different.

Back on the ground, I've read that some F1 cars have generated slight thrust from their radiators, but that this amount was negligible. The cooling system as a whole creates drag, of course.

Roger Pham

Look here, Bernard: "Cooling drag for an automobile is around 10-15% of vehicle drag..." however, the radiator with unrestricted airflow in and out is designed to handle ~120-150 kW of power, NOT for the 15 kW of power typically at cruise. If you would close the air intake so that only 1/10th of the air would enter the radiator at cruise, you will see that the cooling drag would only be around 1-1.5% of the total vehicle drag.

Now, a regular car's cabin is much smaller than the trailer of a semitruck in proportional to the engines...hence my original estimate of 1% or less.

That is when you don't count on the thrust gained when the entering air is heated and increase in volume and hence producing thrust in excess of the drag. A carefully designed exhaust ducting with variable opening (variable nozzle) can cause net thrust gain to offset the drag. Flap to adjust the nozzle sectional area for cooling air exit is a feature on all piston engine aircraft, no matter whether air cooled or liquid cooled engine. The same can be done for an aerodynamically-optimized semitruck to extract some thrust out of the heat of the radiator, to overcome the drag of the intake air.

gorr

I just bought capstone turbines stock (cpst) last week. Im glad that we begin to see them in media, the buyers will read about them and the stock will rise.
I bought the stock at 2.03 $, it is 2.15$ now. When I hear of them a month ago the stock was 1.88$ but I didn't have an online trading account set up but as soon as I open my account the first stock that I bought was capstone.

Now im looking for another stock to buy, I think of ballard fuelcell, is it a good buy in your opinion ?.

Bernard

Roger,

If you go back a few days on this site, you will see that Mercedes has implemented a closing radiator flap on the new C Class. Other manufacturers have done so before (Cruze Eco and Dart Aero for instance).

Mercedes only claims single-digit efficiency gains, and a good part of that is from heat retention on start-stop. If you really can get this down by an order of magnitude, contact them immediately. They will give you the keys to the kingdom and let you implement all of the "1000% improvement" technologies that you've suggested here over the years.

You are obviously a very smart guy, but you also have a tendency to wildly exaggerate. That's not helped by the fact that you never ever admit that one of your guesses is off the mark. That's too bad. I mostly ignore what you write (as I know many others do), but every once in a while feel the need to remind you that this site promotes ideas based on science and not just wishful thinking. It's nothing personal, and realistically, it's probably more my problem than yours. Carry on!

gorr

Capstone stock hit 2.26$ as of today.

http://www.marketwatch.com/investing/stock/CPST

Roger Pham

Bernard stated: "but every once in a while feel the need to remind you that this site promotes ideas based on science and not just wishful thinking."

That's is exactly the point of many of our posters here that we're debating WAVE's unfounded claim of higher efficiency than current diesel plus aerodynamic-optimization that can achieve 10 mpg. Look at the below link to see that Cummins and Peterbilt teamed up to improve efficiency of class 8 trucks by 54%.

http://www.autoblog.com/2013/03/20/supertruck-semi-achieves-54-percent-increase-in-fuel-economy/

"This particular Class 8 Peterbilt 587 uses a high-efficiency Cummins ISX15 engine and managed to average 9.9 miles per gallon over 11 runs over the 312-mile route between Fort Worth and Vernon, TX with a gross combined weight of 65,000 pounds. For comparison's sake, most modern trucks manage between 5.5 and 6.5 mpg. For most long-haul truck drivers, an increase in fuel economy of 54 percent would equate to a savings of around $25,000 per year at current diesel prices."

By contrast, a full-size pickup truck at 1/10th the gross weight can barely manage 20 mpg HWy cruise, or 1/5th the efficiency per wt. basis.
I would like to remind you again that it would be impossible to improve the efficiency of the Capstone 65-kW turbine to above 30%, neither the tank-to-wheel efficiency to above 24-25% using electric drive.
By contrast, turbocompounded diesel now can manage 48% thermal efficiency, while a manual transmission can achieve above 95% efficiency.

Please be reminded that optimism, within the bound of science and mathematic, is the prerequisite for higher achievements. Pessimists won't achieve much because they often fail to even get started.

Roger Pham

Also, the reason that aerodynamic optimizations to the cooling system have shown only single-digit gains in efficiency is because the cooling system only cause 10-15% of total vehicle drag. If one is to reduce this cooling drag by as much as 75%, one can only improve the total vehicle efficiency within a single-digit-percentage gain.

Bernard

Roger,

As the article above clearly states, these Walmart trucks are intended for short hauls from distribution centres to stores. Think of them as giant Priuses that efficiently use battery power in stop-and-go conditions and use a small turbine to recharge the battery packs.

Many here have suggested using turbines in hybrid cars, but they are too expensive and complicated for consumer vehicles. Walmart has done the maths and calculated that it can work in their favour in short-haul trucks for a specific use case. Just like hybrid buses can work in urban mass transit scenarios, even if they do not work for intercity (Greyhound) bus routes.
The flip side to this, of course, is that long-haul solutions do not provide an advantage in suburban mixed traffic.

Roger Pham

Good point, Bernard. If the turbine engine is only to be used occasionally, then the efficiency impact of it will not be significant. The space-age-alien style of design and the turbine engine coupled with a BEV electric drive train will sure turn a lot of heads and attract a lot of attention and good publicity for Walmart for being at the forefront of technological innovation...Score 1 for Walmart!

Other companies wanting an efficient short-haul city truck can simply add on an electric motor of about 100 kW of power, plus about 5 kWh of high-power battery to realize superior efficiency than what a large battery and large electric motor BEV setup can deliver, at much less cost.

For CO2-neutral energy source, bio-diesel can be used, or biomethane can be used as in Westport design bi-fuel NG/diesel engine using a little bit of diesel fuel for ignition of the NG, both fuels together in one injector, to realize much lower fuel cost with minimum engine upgrade cost.
When H2 filling infrastructure for the new wave of FCV will arrive, then H2 from RE sources can be used in place of NG or biodiesel or in any mixture thereof.

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