Plug-In Hybrid Electric Vehicles: How Does One Determine Their Potential for Reducing U.S. Oil Dependence?
12/1/2007
Estimation of the potential of plug-in hybrid electric vehicles' (PHEVs') ability to reduce U.S. gasoline use is difficult and complex. Although techniques have been proposed to estimate the vehicle kilometers of travel (VKT) that can be electrieid, these methods may be inadequate and/or inappropriate for early market introduction estimates. Factors that must be considered with respect to the PHEV itself include (1) kWh battery storage capability; (2) kWh/km depletion rate of the vehicle; (3) liters/km use of gasoline; (4) average daily kilometers diven; (5) annual share of trips exceeding the battery depletion distance; (6) driving cycle(s); (7) charger location; (8)charging rate. Taking into account PHEV design trade-off possibilities (kW vs. kWh of battery, in particular), this paper attempts to extract useful information relating to these topices. Costs per kWh of PHEVs capable of charge depleting (CD) all-electric range vs. those CD in "blended mode (CDB) are examined. Lifetime fuel savings of alternative PHEV operating/utilization strategies are compared to battery cost estimates.
Authors: Vyas, A.; Santini, D.; Duoba, M.; Alexander, M.
E85 Retail Business Case: When and Why to Sell E85
12/1/2007
Adding E85 to the product line of a fueling station has the potential to increase customers, differentiate the station, and it can be a profitable investment. The document identifies seven variables that make E85 profitable and weighs their influence using a model NREL created based on a discounted cash flow analysis. Since fuel throughput was identified as the most important project variable, guidance is offered to help the station owner assess potential E85 throughput.
Authors: Johnson, C; Melendez, M
Test Procedures and Benchmarking: Blended-Type and EV-Capable Plug-In Hybrid Electric Vehicles
12/1/2007
SAE J1711 testing procedures for plug-in hybrid electric vehicles (PHEVs) were issued in 1999. Since that time, full hybrids with larger plug-in battery packs (blended type) and a "range-extender" PHEV type have necessitated a new review of these test procedures. A full-charge test is given to a PHEV to find the capacity and to characterize the vehicle's operation. Driving statistics are useful in processing the full-charge test and in combining depleting with sustaining operation. But just as in the mid-1990s, the lack of refined prototypes with all-electric range capability slows the rate of progress in developing a suitable procedure.
Authors: Duoba, M.; Carlson, R.; Wu, J.
PHEV Hymotion Prius Model Validation and Control Improvements
12/1/2007
Argonne National Laboratory maintains vehicle simulation software, the Powertrain System Analysis Toolkit (PSAT). Because of the importance of component models and the complexity involved in setting up optimized control strategies, the models and controls developed in PSAT require validation. The highly instrumented Toyota Prius, including engine and half-shaft torque sensors, was tested in Argone's Advanced Powertrain Research Facilities, both in its original configuration and with the Hymotion L5 plug-in hybrid electric vehicle (PHEV) battery pack to provide the data needed for a thorough comparison of model results and test data. This paper describes the vehicle test results and explains the validation process on the basis of an analysis of the differences between the test and simulation results.
Authors: Cao, Q.; Pagerit, S.; Carlson, R.; Rousseau, A.
In-Situ Torque Measurements in Hybrid Electric Vehicle Powertrains
12/1/2007
For several years, Argonne National Laboratory has taken a leading role in the benchmarking of various advanced hybrid vehicles for the US FreedomCAR industry-government partnership. Early designs provided highly desirable direct engine torque measurement (with telemetry for non-contact signal acquisition) for steady-state and transient operation in an operating Prius powertrain. Newer designs have done away with a sizable spacer and left the powertrain configuration intact. This was made possible by creating a new flywheel damper unit that inforporates the torque sensor, thus the powertrain fits back together without body modifications. Tradeoffs such as signal dynamic range and filtering are challenges that have been addressed by newer generation designs.
Authors: Bohn, T.; Duoba, M.; Carlson, R
Sorting Through the Many Total-Energy-Cycle Pathways Possible with Early Plug-In Hybrids
12/1/2007
Using the "total energy cycle" methodology, the report compares U.S. near term (to about 2015) alternative pathways for converting energy to light-duty vehicle kilometers of travel (VKT) in plug-in hybrids (PHEVs), hybrids (HEVs), and conventional vehicles. For PHEVs, we present total energy-per-unit-of-VKT information two ways: (1) energy from the grid during charge depletion; (2) energy from stored on-board fossil fuel when charge sustaining. The report examines incremental sources of supply of liquid fuel such as oil sands, Fischer-Tropsch diesel via natural gas, and ethanol from cellulosic biomass. The report compares such fuel pathways to various possible power converters producing electricity, including new coal boilers;integrated, gasified coal combined cycle;existing natural gas fueled combined cycle;existing natural gas combustion turbines;wood-to-electricity;and wind/solar. Also considered was a simulated fuel cell HEV and a plug-in hybrid fuel cell vehicle.
Authors: Gaines, L.; Burnham, A.; Rousseau, A.; Santini, D.
On-Road Evaluation of Advanced Hybrid Electric Vehicles over a Wide Range of Ambient Temperatures
12/1/2007
Hybrid electric vehicles can provide increased fuel economy over convention gasoline powered vehicles but these advantages can be affected dramatically by wide variations in operating temperatures. To investigate cold and hot temperature effects on HEV operation and efficiency, an on-road evaluation protocol was defined and conducted over a 6-month study at widely varying temperatures ranging from -14 degrees C to 31 degrees C.
Authors: Carlson, R.; Duoba, M.; Bocci, D.; Lohse-Busch, H.
Advanced Lithium-Ion Batteries for Plug-in Hybrid Electric Vehicles
12/1/2007
In this study, electric-drive vehicles with series powertrains were configured to utilize a lithium-ion battery of very high power and achieve sport-sedan performance and excellent fuel economy. The batteries for these vehicles were designed to deliver 100 kW of power at 90% open-circuit voltage to provide high battery efficiency (97-98%) during vehicle operation. This results in battery heating of only 1.6 degree C per hour of travel on the urban dynamonmeter driving schedule cycle, which essentially eliminates the need for battery cooling. Vehicle simulation tests using Argonne's Powertrain System Analysis Toolkit (PSAT), whoed that these vehicles could accelerate to 60 mph in 6.2 to 6.3 seconds and achieve fuel economies of 50 to 54 mpg on the urban and highway fuel economy test cycles.
Authors: Nelson, P.; Amine, K.; Rousseau, A.; Yomoto, H.
Impact of Component Size on Plug-In Hybrid Vehicle Energy Consumption Using Global Optimization
12/1/2007
Plug-in hybrid electric vehicles are a promising alternative to gas-only vehicles and offer the potential to greatly reduce fuel use in transportation. Their potential energy consumption is highly linked to the size of the components. This study focuses on the impact of the electric system energy and power on control and energy consumption. Based on a parallel pre-transmission architecture, several vehicles were modeled with an all-electric range from 5 to 40 miles on the Urban Dynamometer Driving Schedule to illustrate various levels of available electric energy. Five other vehicles were created, with various levels of power and the same battery energy. The vehicles were then simulated under optimal control on multiple combinations of cycle and distance by using a global optimization algorithm. The results from each optimization were analyzed to highlight control patterns. The potential minimal fuel consumption that can be achieved by each of them is presented in this report.
Authors: Karbowski, D.; Haliburton, C.; Rousseau, A.
Plug-In Hybrid Electric Vehicle Control Strategy Parameter Optimization
12/1/2007
The fuel economy of plug-in hybrid electric vehicles (PHEVs) is highly dependent on All-Electric-Range (AER) and control strategy. Previous studies have shown that in addition to parameters influencing hybrid electric vehicles (HEVs), control strategies of PHEVs are also influenced by the trip distance. This study uses a pre-transmission parallel PHEV model developed with the Powertrain System Analysis Toolkit (PSAT). A non-derivative based algorithm called DIRECT (for Divided RECTangles), is used to optimize the main control strategy parameters. The fuel economy and main performance criteria of the PHEVs are compared for the initial design and final optimal design. An optimal control solution resulting from an extensive search of the entire design space can provide physical insight into the PHEV operation.
Authors: Rousseau, A.; Pagerit, S.; Gao, D.
PHEV all electric range and fuel economy in charge sustaining mode for low SOC operation of the JCS VL41M Li-Ion battery using Battery HIL
12/1/2007
Plug-in hybrid electric vehicles have been identified as an effective technology to displace petroleum by drawing significant off-board energy from the electrical grid. A plub-in vehicle is expected to operate in an electric-only or a charge-depleting mode over a large SOC window (60-80% of total operational SOC) for maximum petroleum displacement. The all electric range (AER) test quantifies the electric-only miles possible with the battery for a particular configuration and vehicle class. This paper describes the hardware-in-the-loop testing of a 41-Ah Li-ion battery designed for PHEV applications. Vehicle AER, temperature rise and battery performance in the charge-sustaining (CS) mode at low SOCs (35 to 20%) were evaluated. These tests indicate that CS operation at low SOC for an urban driving cycle has no effect on fuel economy. Thus, the lower limit set for SOC is a "life" decision, not a "performance" decision.
Authors: Shidore, N.; Bohn, T.; Duoba, M.; Lohse-Busch, H.; Sharer, P.
Vehicle Simulation Results for Plug-In HEV Battery Requirements
11/9/2007
Plug-In Hybrid Electric Vehicles (PHEVs) have the ability to drastically reduce petroleum use. The FreedomCAR Office of Vehicle Technology is developing a program to study the potential of the technology. The first step in the program is to define the requirements of PHEV components. As the battery appears to be the main tecnical barrier, both from a performance and cost perspective, the main efforts have been focused on that component. Argonne National Laboratory researchers have developed a process to define the requirements of energy storage systems for plug-in applications. This paper describes the impact of All Electric Range, drive cycle, and control strategy on battery requirements.
Authors: Sharer, P.; Rousseau, A.; Nelson, P.; Pagerit, S.
Life-Cycle Assessment of Corn-Based Butanol as a Potential Transportation Fuel
11/1/2007
Butanol produced from bio-sources (such as corn) could have attractive properties as a transportation fuel. Production of butanol through a fermentation process called acetone-butanol-ethanol (ABE) has been the focus of increasing research and development efforts. The purpose of this study is to estimate the potential life-cycle energy and emission effects associated with using bio-butanol as a transportation fuel. The study employs a well-to-wheels analysis tool named the Greenhouse Gases, Regulated Emissions and Energy Use in Transportation (GREET) model developed by Argonne National Laboratory and the Aspen Plus model developed by AspenTech. The study describes the butanol production from corn, including grain processing, fermentation, gas stripping, distillation, and adsorption for products separation. Our study shows that, while the use of corn-based butanol achieves energy benefits and reduces greenhouse gas emissions, the results are affected by the methods used to treat the acetone that is co-produced in butanol plants.
Authors: Wu, M.; Wang, M.; Liu, J.; Huo, H.
Biofuels: An Important Part of a Low-Carbon Diet
11/1/2007
New rules are being developed that will require fuel providers to account for and reduce the heat-trapping emissions associated with the production and use of transportation fuels. The purpose of this report is to ensure that we "count carbs" accurately, by explaining why we need a comprehensive accounting system for carbon emissions--one that measures global warming emissions over a transportation fuel's entire life cycle. We also need to "make carbs count" by creating performance-based policies that will reward low-carbon transportation fuels for their performance.