Task 15, PHEVs, writing up report, studying financial viability of PHEVs

October 18, 2013 12:50 PM


Members of Task 15, Plug-in Hybrid Electric Vehicles (PHEVs), are currently writing up the final report for the initial phase of the Task. A follow-on phase is being considered and will be proposed at the IA-HEV Executive Committee meeting to occur in November 2013 in Barcelona, Spain.

U.S. participants in Task 15 continued to make use of the vehicle simulations done in support of the Task at Argonne National Laboratory (ANL). In brief, they estimated that the lifetime costs of U.S. ownership of certain types of hybrids (HEVs) and PHEVs will be lower than for conventional gasoline vehicles once U.S. gasoline prices reach $5.00/gallon (3.75 euros per liter). 

The ANL team examined the simulations of the types of electric drive powertrains that are most prevalent in the U.S. These include the input-split (IS), in which the power of the engine is split at the input to a planetary gearset before the two electric machines (generator and motor); output-split (OS), in which the power of the engine feeds into a generator which feeds into a planetary gearset and then the motor; and the all-electric-vehicle (AEV) powertrain which allows elimination of the generator and planetary gearset. The ANL team also studied two new cases of PHEVs derived from the HEV IS, which had 26 kW of peak battery pack power, far less than the other IS PHEVs previously simulated (~60 kW). The OS PHEVs simulated had 140+ kW of peak battery pack power.

The experts estimated the increase in initial retail price attributable to the battery pack versus the rest of the powertrain for each case. The simulations used Argonne’s BatPaC battery cost model and its Autonomie powertrain cost model. The investigation revealed that as peak electric drive power rose, the increase in the cost of the battery pack was moderate. However, the expense of the PHEV powertrain more than doubled when enough power was provided to assure all-electric operation under all driving conditions, including drag strip acceleration tests conducted by car magazines.

The evaluations indicate that there may be a range of peak power around 60 kW that is “just right” for IS PHEVs. This means that the 60-kW PHEV IS powertrains could represent the least lifetime cost to most owners, along with satisfactory everyday electric operations. Comparing the PHEV IS simulations at the 60-kW level of power to those at 26 kW showed only small changes in initial cost, but significant improvements in operating efficiency. The increased battery pack power of the 60-kW PHEV50 IS cases (with a 31-mile or 50-km all-electric range) allowed reduction in the power required from the engine, so the engine was “downsized,” helping reduce costs.

Total lifetime U.S. dollars/km estimates for various types of electric drive vehicles at the gasoline price of $5.00/gallon, 263 full charges/year, ten years of constant urban driving totaling 16,300 km/year, with inter-urban driving of 0 km/year (indicated in red), 1,510 km/year (yellow), or 3,810 km/year (green). Graph courtesy of ANL. (* AEV car rental costs included for long distance inter-city travel)

An implication of these findings is that an IS PHEV powertrain with a 50-kilometer all-electric range would be the least expensive driving option for intensively used vehicles when U.S. gasoline costs increase to $5.00/gallon (3.75 euros per liter). Electricity prices assumed were $0.15/kWh. Recent U.S. gasoline prices have remained below $4.00/gallon on average.

The analysis implicitly assumes that the automakers that produce IS HEVs can also produce derivative IS PHEVs, making use of the same electric machinery (for example, two of the leading-selling PHEV powertrains available in the U.S. today are essentially derivatives of IS HEVs). HEVs similar to the 26-kW IS HEV are increasingly successful in the U.S. at present gasoline prices, consistent with the U.S. analysts’ estimates made for $3.50/gallon gasoline. Finally, any IS HEV or IS PHEV was estimated to offer a lifetime cost savings relative to the conventional gasoline option in the $5.00/gallon gasoline scenario.  However, electric drive power levels greater than 26 kW would be needed to make IS PHEVs superior to 26 kW HEVs. The case of 60-kW HEVs was not examined.

Contributed by Mr. Dan Santini
Task 15 Operating Agent