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Hybrid Commercial Vehicles

In urban applications, stop-and-go driving cycles offer many opportunities to recover and recycle braking energy, and in the heavy-duty vehicle market, hybrid vehicle technology is gradually finding specific applications.

Important obstacles stand against the adoption of innovative technologies, of which one of the most important is the lack of practical information coming from independent sources. The objective of these fact sheets is to inform those in the trucking industry about new and emerging advanced technologies that have been tested through the Energotest program (run by FPInnovations), which can help increase fuel efficiency and, at the same time, reduce the environmental impact of freight transportation in Canada.

Description

Hybrid vehicles use a second power source in addition to the normal internal combustion engine, which may be gas- or diesel-powered. There are two types of hybrid system architectures: serial (the engine propels the vehicle solely through the secondary motor) and parallel (the engine or auxiliary motor can propel the vehicle independently or in combination). Engine size can be considerably reduced since a computer determines the most efficient power combination at any given moment, depending on operating conditions and driver demand. Transmissions for the hybrid technology can be either automatic or automated.

Hybrid vehicles use regenerative braking systems, which enable them to recapture part of the kinetic energy normally lost when braking. This energy represents up to 40% of an engine’s output and it can be stored as electric energy (in batteries) or hydraulic energy (in hydraulic accumulators), which can be also charged by the main engine under certain circumstances.

This energy is then reused to power an auxiliary motor that assists the engine in certain conditions (launch, hill climbing, etc.) or to power auxiliary systems (HVAC or power take-off). The hybrid regenerative braking system could be used instead of, or alongside, an exhaust brake or retarder, to prevent brake fade and excessive brake wear.

Scope of Application

Hybrid vehicle technology is already a reality for urban applications where stop-and-go driving cycles offer many opportunities to recover and recycle braking energy, such as delivery, waste management, and public transportation. Hybrid technology has been available on light-duty vehicles for over 10 years and commercially available on Class 6 and 7 trucks for about five years. Hybrid vehicle technology is gradually finding specific applications in the heavy-duty vehicle market, with several manufacturers already offering Class 8 hybrid vehicles, and in the future it can offer an even larger potential for heavy-duty applications. This is because even though full-electric solutions are technically feasible for light- and medium-duty vehicles and might be available in the near term, Class 8 vehicles, due to the long distances they cover and the high amount of power they require, would always need more powerful and independent sources of energy.

Class 4 to Class 7 hybrid vehicles on stop-and-go duty cycles have shown overall fuel consumption improvement up to 40% in pick-up and delivery operations and up to 50% in utility operations. Class 8 hybrid vehicles on highway and regional hauling demonstrated between 4 and 10% fuel savings.

FPInnovations conducted a feasibility study on the concept of a Class 8 heavy-duty hybrid tractor-semi-trailer combination. Computer simulations showed that compared to conventional vehicles, and depending on the duty cycle, various hybrid versions would obtain fuel savings from 10-12% (for on-highway and regional duty cycles) to 30% (for off-highway duty cycles).

Another FPInnovations project evaluated two Class 7 hybrid vehicles, one operated by Agropur and the other by the Société des alcools du Québec (SAQ), two fleets that are members of Program Innovation Transport (PIT). The track tests conducted on a delivery stop-and-go duty cycle in the framework of the Energotest^TM 2010 test campaign showed 26 to 35% lower fuel consumption, compared to a similar conventional vehicle.

Return on Investment

The economic impact of the various fuel-saving measures is evaluated based on the payback period, which is calculated by dividing the total additional cost of a modification by the annual net savings it provides.

According to the information provided by the two PIT fleet partners, which operate both conventional and hybrid Class 7 similar vehicles, the hybrid versions were $40 000 more expensive than the corresponding conventional vehicles. According to the manufacturer, the Class 8 hybrid version would be $45 000 more expensive than the homologue conventional version.

The following is an example of a payback calculation for a Class 7 hybrid electric vehicle operating in stop-and-go delivery haul:

• The additional purchase cost for the hybrid vehicle is $40 000.
• Fuel savings of 35%.
• We assume an average annual mileage of 30 000 km for the vehicle, and an average fuel consumption for conventional trucks of 24 L/100 km.
• The annual fuel savings would be 2 520 L:
   
• At a diesel fuel price of $1.10/L, the annual savings would be: 2 520 L x $1.10/L = $2 772.
• The payback period would be: $40 000 / $2 772 = 14.43 years or 173 months.

The following is an example of a payback calculation for a Class 8 hybrid electric vehicle operating in an on-highway, regional haul:

• The additional purchase cost for the hybrid vehicle is $45 000
• Fuel savings of 10%.
• We assume an average annual mileage of 200 000 km for the tractor, and an average fuel consumption for conventional class 8 trucks of 34 L/100 km.
• The annual fuel savings would be 6 800 L:
   
• At a diesel fuel price of $1.10/L, the annual savings would be: 6 800 L x $1.10/L = $7 480.
• The payback period would be: $45 000 / $7 480 = 6.02 years or 72 months.

Tax incentive measures or government technology implementation funding programs would achieve a faster return on investment.

Specification Considerations

There are wide-ranging advantages to using hybrid technology: fuel economy and a reduction in greenhouse gas (GHG) emissions, increased range over that of pure electric vehicles, less noise when in electric mode, and driving comfort (automatic or automated transmission, additional electric power when accelerating or going up hills).

Diesel-electric or hydraulic hybrid trucks do not need any particular facilities or logistics to operate since they still have a conventional diesel engine, and the electric or hydraulic energy is generated and stored within the truck.

In terms of fuel consumption and GHG reductions, vehicle duty cycles providing the greatest benefits are those with a lot of braking and stop-and-go activity, therefore those operating mainly in an urban environment. Manufacturers commonly advertise savings of about 30%. Users report savings ranging from 5% to 30%, depending on operating conditions (ratio of urban/interurban travel, number of stops per kilometre, climate, etc.). Buyers considering purchasing a hybrid vehicle should have their duty cycle analysed to accurately gauge the potential savings.

Another way to save fuel in certain hybrid vehicles is to use the batteries to power the electric accessories. This makes it possible to reduce demand on the diesel engine when the truck is on the road, or to stop the diesel engine’s idling when the truck is parked and the driver needs power, for instance to heat or air condition the cab. There are also hybrid systems that can power equipment that is normally run off a conventional engine’s power take-off.

Driving a hybrid truck is very easy after some quick instructions. Once behind the wheel, drivers will not notice any significant differences compared with a conventional truck, other than a monitor indicating, in real time, the operating mode (electric, diesel, regenerative braking, etc.)

Regulatory Issues

There are no specific regulatory requirements, but the hybrid system’s weight increases tare and marginally reduces payload allowance.

Maintenance Considerations

Hybrid system components meet the same reliability and quality requirements as other components of a conventional vehicle. A hybrid truck can therefore be used in the same conditions. However, outdoor temperatures can affect fuel economy. Battery performance deteriorates when temperatures are too low or, conversely, when too high. Most manufacturers have implemented heating or cooling systems to minimize this inconvenience.

Like conventional trucks, it is possible to use alternative fuels, such as biodiesel, in a hybrid truck, provided that the diesel engine is compatible. The benefits of hybrid technology are therefore added to those of alternative fuel.

When it comes to a hybrid system’s specific components, such as electric, electronic, or hydraulic, most fleets already using the systems have not reported any problems with reliability resulting in increased maintenance. However, these fleets have only been using hybrid trucks for two to three years at the most.

Hybrid system components are readily available at dealers, like any other part.

Savings in maintenance costs have also been noted for certain mechanical components. Maintenance on brakes is significantly lower, due to less wear on the brakes because of regenerative braking. This wear can be reduced by up to 50% for specific applications such as garbage trucks.

The diesel engine is also used less overall compared with a conventional truck, and runs at lower power and torque levels since the engine can be assisted by the secondary motor. The result is not only less wear on the engine, but also less maintenance and more durability.

Lastly, the key to successfully adding hybrid trucks to a fleet is to have maintenance technicians who have received comprehensive training for this new technology.

References

Eaton Corporation. 2007. Hybrid power systems: Medium-duty pick-up/city delivery applications.

Eaton Corporation, Truck Components Operations, Kalamazoo, MI.

Frost & Sullivan. 2009. Total North American Class 6-8 truck hybrid powertrain systems market, #N37A-18.

Kendall, J. 2009. Heavy-duty hybrids. Truck & Bus Engineering Online, 27-Feb-2009. SAE International, Warrendale, PA.

Surcel, M.-D. 2010. Energotest 2010: Fuel consumption track tests of fuel-saving technologies. FPInnovations, Pointe-Claire, QC. Internal Report IR-2010-10-28. 93 p.

Surcel, M.-D., Michaelsen, J. 2010. Feasibility Study for a Heavy-duty Tractor - Motorized Semi-trailer Hybrid Electric Combination.Paper no. 2010-01-1932. SAE 2010 Commercial Vehicle Engineering Congress & Exhibition, October 5-6, 2010, Rosemont – Chicago, IL.

Date modified:

2012-03-12

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