EPRI Hybrid Electric Vehicle Working Group: HEV Costs and Emissions

Hybrid electric vehicles (HEVs) are attractive options for increasing vehicle fuel economy and reducing emissions of criteria pollutants and greenhouse gases. Two automobile manufacturers have already introduced HEVs, and other manufacturers are planning to introduce their own models.

One available HEV combines mass reduction (also applicable to conventional vehicles) with idle-stop, regenerative braking, and electric-drive assist to achieve a fuel economy more than 2.5 times the current Corporate Average Fuel Economy (CAFE) standard. The second HEV combines idle-stop, regenerative braking, electric assist acceleration, and continuously variable transmission (CVT) to achieve a fuel economy of more than twice the current CAFÉ standard, qualifying as a super ultra-low emissions vehicle (SULEV).

Other designs are also possible. Hybrids that are designed to have all-electric travel capability through use of grid electricity could qualify as zero-emissons vehicles (ZEVs) if operated only on electricity for a sufficient percentage of total miles driven. Compared with all-electric vehicles, such HEVs would not be limited by the energy-storage capacity of their battery packs and thus would not be limited in driving range. The technical feasibility, economic affordability, fuel saving potential, and emissions benefits of a full range of HEVs need to be evaluated.

New Working Group Formed

The Electric Power Research Institute (EPRI) has formed an HEV working group (HEVWG) to undertake an unbiased, scientifically based evaluation of three widely varying hybrid options. The group conducted a literature search to confirm that others had not undertaken similar work.

The HEVWG sought support from the following organizations:

• Electric Utilities
• EPRI
• New York State Power Authority
• Southern California Edison - Southern Company
• Auto Manufacturers
• General Motors (GM)
• Ford
• California Air Resources Board (CARB)
• South Coast Air Quality Management District
• University of California at Davis
• U.S. Department of Energy (DOE)
• Argonne National Laboratory
• National Renewable Energy Laboratory (NREL)

In addition, other utility companies and Volkswagen of America are kept informed of HEVWG work.

Results

After evaluating the state of current knowledge, the HEVWG established an analysis framework and evaluated three types of vehicles: a small car (Saturn SC), a midsize car (Chevrolet Lumina), and an SUV (Chevrolet Tahoe). Within each vehicle platform, the HEVWG simulated a conventional vehicle (CV), a parallel HEV with no all-electric range and no capability to recharge battery from electric grid (P0), a parallel HEV with 20-mile all-electric range with capability to charge from electric grid (P20), and a parallel HEV with 60-mile all-electric range with capability to charge from electric grid (P60).

The group used NREL's ADVISOR model to characterize each vehicle and Argonne's GREET model to estimate upstream emissions. The group developed a base methodology for estimating HEV retail price equivalent and used Argonne's methodology. Separately, a consultant estimated market penetration potential through consumer focus group and a market penetration model. The group developed alternative scenarios (such as lower battery cost, longer battery life, more annual driving) and assessed HEV market penetration.

The results show that HEVs have much better acceleration capability at low speeds, but a lower passing capability at high speeds (Table 1). The HEVs would use less fuel (Figure 1) and would emit fewer full fuel-cycle pollutants (Figure 2). The vehicles would cost more (Figure 3), but they still could have substantial market penetration if widely available (Figure 4).

Table 1. Simulated Acceleration Times for a Mid-Sized Car   Acceleration Time (s) Speed (mph) CV P0 P20 P60 0-30 3.5 3.1 3.0 3.0 0-60 9.3 8.7 8.8 8.9 40-60 4.6 4.2 4.2 4.3 50-70 4.5 5.2 5.1 5.2

Figure 1. Well-to-Wheels Energy Consumption

Figure 2. NOx + ROG Emissions (Well to Wheels)

Figure 3. Estimated Vehicle Prices Under Alternative Methods (Mid-Sized Car)

Figure 4. Estimated Market Penetration (Mid-Sized Car)

Future Plans

A report on the work performed is being prepared. A second phase of the project is being proposed under which alternative hybridization strategies will be investigated. This phase will expand the vehicle price-estimating task by seeking information from electric-drive component developers.