Clean Cities Alternative Fuel Price Report, April 2018
6/14/2018
The Clean Cities Alternative Fuel Price Report for April 2018 is a quarterly report on the prices of alternative fuels in the U.S. and their relation to gasoline and diesel prices. This issue describes prices that were gathered from Clean Cities coordinators and stakeholders between April 1, 2018 and April 16, 2018, and then averaged in order to determine regional price trends by fuel and variability in fuel price within regions and among regions. The prices collected for this report represent retail, at-the-pump sales prices for each fuel, including Federal and state motor fuel taxes.
Table 2 reports that the nationwide average price (all amounts are per gallon) for regular gasoline has increased 17 cents from $2.50 to $2.67; diesel increased 7 cents from $2.96 to $3.03; CNG increased 1 cent from $2.17 to $2.18; ethanol (E85) increased 15 cents from $2.06 to $2.21; propane remained the same at $2.83; and biodiesel (B20) increased 3 cents from 2.84 to $2.87.
According to Table 3, CNG is $.49 less than gasoline on an energy-equivalent basis, while E85 is $0.20 more than gasoline on an energy-equivalent basis.
Authors: Bourbon, E.
Airport Analyses Informing New Mobility Shifts: Opportunities to Adapt Energy-Efficient Mobility Services and Infrastructure: Preprint
6/12/2018
An airport is one of the most important assets for a region's economic development and connectivity with the rest of the nation and world. Key aspects for investigation of energy efficient mobility at airports is ground transportation including factors ranging from the infrastructure, mobility services, and associated revenues. Data is critical to understand the maturity of new mobility services that can inform both cities and airports on how to respond, approach, manage, and adapt to the challenges, opportunities, and uncertainties associated with shifts in new mobility that influence human behavior, energy-efficiency and sustainability strategies. One key question identified in this article is how quickly we are adapting to new mobility options - such as app-based ride-hailing and 'pooling' services - that may provide an opportunity to influence energy efficiency of ground transportation to and from airports. By starting with airports in the regions of four smart city finalists in the U.S. DOT Smart City Challenge, this paper focuses on key observability aspects of new modes and the rate of shifts in mobility patterns across San Francisco, Portland, Denver, and Kansas City. With the emerging megatrend of rising urbanization and rising air travel demand (a predicted doubling in demand by 2035), airports are expected to increasingly be on the front lines of adaptation to new transportation technology and services in terms of infrastructure investments, policies, and revenues. As airports have demonstrated the most potential and capability of any public institution to implement fees for new ride-hailing services, they are also a prime resource for collecting important data to help understand smart mobility transitions. Results focused on the shifts in revenues for ground transportation at airports offer one vantage point into the pace of transitions and adaptations in the new emerging mobility landscape, and present an opportunity to analyze how future adaptations could support more energy-efficient scenarios.
Authors: Henao, A.; Sperling, J.; Garikapati, V.; Hou, Y.; Young, S.
Total Thermal Management of Battery Electric Vehicles (BEVs). SAE Paper No. 2018-37-0026
5/30/2018
The key hurdles to achieving wide consumer acceptance of battery electric vehicles (BEVs) are weather-dependent drive range, higher cost, and limited battery life. These translate into a strong need to reduce a significant energy drain and resulting drive range loss due to auxiliary electrical loads the predominant of which is the cabin thermal management load. Studies have shown that thermal subsystem loads can reduce the drive range by as much as 45% under ambient temperatures below -10 degrees C. Often, cabin heating relies purely on positive temperature coefficient (PTC) resistive heating, contributing to a significant range loss. Reducing this range loss may improve consumer acceptance of BEVs. The authors present a unified thermal management system (UTEMPRA) that satisfies diverse thermal and design needs of the auxiliary loads in BEVs. Demonstrated on a 2015 Fiat 500e BEV, this system integrates a semi-hermetic refrigeration loop with a coolant network and serves three functions: (1) heating and/or cooling vehicle traction components (battery, power electronics, and motor) (2) heating and cooling of the cabin, and (3) waste energy harvesting and re-use. The modes of operation allow a heat pump and air conditioning system to function without reversing the refrigeration cycle to improve thermal efficiency. The refrigeration loop consists of an electric compressor, a thermal expansion valve, a coolant-cooled condenser, and a chiller, the latter two exchanging heat with hot and cold coolant streams that may be directed to various components of the thermal system. The coolant-based heat distribution is adaptable and saves significant amounts of refrigerant per vehicle. Also, a coolant-based system reduces refrigerant emissions by requiring fewer refrigerant pipe joints. The authors present bench-level test data and simulation analysis and describe a preliminary control scheme for this system.
Authors: Chowdhury, S.; Leitzel, L.; Zima, M.; Santacesaria, M.; Titov, G.; Lustbader, J.; Rugh, J.; Winkler, J.; Khawaja, A.; Govindarajalu, M.
State of the States: Fuel Cells in America 2017, 8th Edition
5/23/2018
This January 2018 report, the eighth in a series, provides a comprehensive analysis of state activities supporting fuel cell and hydrogen technology, including profiles of all 50 states with a catalog of recent installations, policies, funding, and deployments around the country.
Authors: Curtin, S.; Gangi, J.
Foothill Transit Agency Battery Electric Bus Progress Report, Data Period Focus: Jan. 2017 through Dec. 2017
5/16/2018
This report summarizes results of a battery electric bus (BEB) evaluation at Foothill Transit, located in the San Gabriel Valley area of Los Angeles. Foothill Transit is collaborating with the California Air Resources Board and the U.S. Department of Energy's National Renewable Energy Laboratory (NREL) to evaluate the buses in revenue service. The focus of this evaluation is to compare the performance and the operating costs of the BEBs to that of conventional technology buses and to track progress over time. Previous reports documented results from April 2014 through December 2016. This report extends the data analysis through December 2017. NREL plans to publish progress reports on the Foothill Transit fleet every six months through 2020.
Authors: Eudy, L.; Jeffers, M.
Electric Trucks: Where They Make Sense
5/1/2018
This report assesses the viability for North American Class 3 to 8 commercial electric vehicles to help the industry understand the many arguments for and against them. This report provides a foundation for understanding the key pro and con discussions of this rapidly evolving technology alternative to diesel powertrains.
Notes:
This copyrighted publication can be accessed through North American Council for Freight Efficiency's website.
Electric School Bus Pilot Project Evaluation
4/20/2018
This report provides an overview of a Massachusetts Department of Energy Resources pilot project to test electric school buses in school transportation operations. Through this project, three electric school buses were deployed at three school districts around the state and bus operations and reliability tracked for approximately one year. The project was designed to understand the opportunities and challenges associated with using electric school buses as a strategy to provide safe, reliable, cost effective school transportation. Key findings and recommendations are also provided.
The Dynamics of PEVs in the Secondary Market and Their Implications for Vehicle Demand, Durability, and Emissions
4/13/2018
California is one of the first markets in the world to have a significant secondary market for plug-in electric vehicles (PEVs). This study examines the status of the nascent secondary PEV market in California. It reviews who purchases these vehicles and how used PEVs are utilized. It also examines the role of PEV purchase incentives via surveys of used PEV buyers and by analyzing the purchase behavior for used vehicles nationwide and in California.
Authors: Turrentine, T.; Tal, G.; Rapson, D.
Determining Off-Cycle Fuel Economy Benefits of 2-Layer HVAC Technology. SAE Paper No. 2018-01-1368
4/12/2018
This work presents a methodology to determine the off-cycle fuel economy benefit of a 2-Layer HVAC system which reduces ventilation and heat rejection losses of the heater core versus a vehicle using a standard system. Experimental dynamometer tests using EPA drive cycles over a broad range of ambient temperatures were conducted on a highly instrumented 2016 Lexus RX350 (3.5L, 8 speed automatic). These tests were conducted to measure differences in engine efficiency caused by changes in engine warmup due to the 2-Layer HVAC technology in use versus the technology being disabled (disabled equals fresh air-considered as the standard technology baseline). These experimental datasets were used to develop simplified response surface and lumped capacitance vehicle thermal models predictive of vehicle efficiency as a function of thermal state. These vehicle models were integrated into a database of measured on road testing and coupled with U.S. typical meteorological data to simulate vehicle efficiency across seasonal thermal and operational conditions for hundreds of thousands of drive cycles. Fuel economy benefits utilizing the 2-Layer HVAC technology are presented in addition to goodness of fit statistics of the modeling approach relative to the experimental test data.
Authors: Jehlik, F.; Chevers, N.; Moniot, M.; Song, Y.; Hirabayashi, H.; Nomura, M.; Wood, E.
Influences on Energy Savings of Heavy Trucks Using Cooperative Adaptive Cruise Control
4/3/2018
An integrated adaptive cruise control (ACC) and cooperative ACC (CACC) was implemented and tested on three heavy-duty tractor-trailer trucks on a closed test track. The first truck was always in ACC mode, and the followers were in CACC mode using wireless vehicle-vehicle communication to augment their radar sensor data to enable safe and accurate vehicle following at short gaps. The fuel consumption for each truck in the CACC string was measured using the SAE J1321 procedure while travelling at 65 mph and loaded to a gross weight of 65,000 lb, demonstrating the effects of: inter-vehicle gaps (ranging from 3.0 s or 87 m to 0.14 s or 4 m, covering a much wider range than previously reported tests), cut-in and cut-out maneuvers by other vehicles, speed variations, the use of mismatched vehicles (standard trailers mixed with aerodynamic trailers with boat tails and side skirts), and the presence of a passenger vehicle ahead of the platoon. The results showed that energy savings generally increased in a non-linear fashion as the gap was reduced. The middle truck saved the most fuel at gaps shorter than 12 m and the trailing truck saved the most at longer gaps, while lead truck saved the least at all gaps. The cut-in and cut-out maneuvers had only a marginal effect on fuel consumption even when repeated every two miles. The presence of passenger-vehicle traffic had a measurable impact. The fuel-consumption savings on the curves was less than on the straight sections.
Authors: McAuliffe, B.; Lamert, M.; Lu, X.-Y.; Shladover, S.; Surcel, M.-D.; Kailas, A.
Effects of Heat of Vaporization and Octane Sensitivity on Knock-Limited Spark Ignition Engine Performance. SAE Paper No. 2018-01-0218
4/3/2018
Knock-limited loads for a set of surrogate gasolines all having nominal 100 research octane number (RON), approximately 11 octane sensitivity (S), and a heat of vaporization (HOV) range of 390 to 595 kJ/kg at 25 degrees C were investigated. A single-cylinder spark-ignition engine derived from a General Motors Ecotec direct injection (DI) engine was used to perform load sweeps at a fixed intake air temperature (IAT) of 50 degrees C, as well as knock-limited load measurements across a range of IATs up to 90 degrees C. Both DI and pre-vaporized fuel (supplied by a fuel injector mounted far upstream of the intake valves and heated intake runner walls) experiments were performed to separate the chemical and thermal effects of the fuels' knock resistance. The DI load sweeps at 50 degrees C intake air temperature showed no effect of HOV on the knock-limited performance. The data suggest that HOV acts as a thermal contributor to S under the conditions studied. Measurement of knock-limited loads from the IAT sweeps for DI at late combustion phasing showed that a 40 vol% ethanol (E40) blend provided additional knock resistance at the highest temperatures, compared to a 20 vol% ethanol blend and hydrocarbon fuel with similar RON and S. Using the pre-vaporized fuel system, all the high S fuels produced nearly identical knock-limited loads at each temperature across the range of IATs studied. For these fuels RON ranged from 99.2 to 101.1 and S ranged from 9.4 to 12.2, with E40 having the lowest RON and highest S. The higher knock-limited loads for E40 at the highest IATs examined were consistent with the slightly higher S for this fuel, and the lower engine operating condition K values arising from use of this fuel. The study highlights how fuel HOV can affect the temperature at intake valve closing, and consequently the pressure-temperature history of the end gas leading to more negative values of K, thereby enhancing the effect of S on knock resistance.
Authors: Ratcliff, M.A.; Burton, J.; Sindler, P.; Christensen, E.; Fouts, L.; McCormick, R.L.
Exploring Telematics Big Data for Truck Platooning Opportunities. SAE Paper No. 2018-01-1083
4/3/2018
NREL completed a temporal and geospatial analysis of telematics data to estimate the fraction of platoonable miles traveled by class 8 tractor trailers currently in operation. This paper discusses the value and limitations of very large but low time-resolution data sets, and the fuel consumption reduction opportunities from large scale adoption of platooning technology for class 8 highway vehicles in the US based on telematics data. The telematics data set consist of about 57,000 unique vehicles traveling over 210 million miles combined during a two-week period. 75% of the total fuel consumption result from vehicles operating in top gear, suggesting heavy highway utilization. The data is at a one-hour resolution, resulting in a significant fraction of data be uncategorizable, yet significant value can still be extracted from the remaining data. Multiple analysis methods to estimate platoonable miles are discussed. Results indicate that 63% of total miles driven at known hourly-average speeds happens at speeds amenable to platooning. When also considering availability of nearby partner vehicles, results indicate 55.7% of all classifiable miles driven were platoonable. Analysis also address the availability of numerous partners enabling platoons greater than 2 trucks and the percentage of trucks that would be required to be equipped with platooning equipment to realize more than 50% of the possible savings.
Authors: Lammert, M.P.; Bugbee, B.; Hou, Y.; Mack, A.; Muratori, M.; Holden, J.; Duran, A.; Swaney, E.
Development of 80- and 100- Mile Work Day Cycles Representative of Commercial Pickup and Delivery Operation
4/3/2018
When developing and designing new technology for integrated vehicle systems deployment, standard cycles have long existed for chassis dynamometer testing and tuning of the powertrain. However, to this day with recent developments and advancements in plug-in hybrid and battery electric vehicle technology, no true 'work day' cycles exist with which to tune and measure energy storage control and thermal management systems. To address these issues and in support of development of a range-extended pickup and delivery Class 6 commercial vehicle, researchers at the National Renewable Energy Laboratory in collaboration with Cummins analyzed 78,000 days of operational data captured from more than 260 vehicles operating across the United States to characterize the typical daily performance requirements associated with Class 6 commercial pickup and delivery operation. In total, over 2.5 million miles of real-world vehicle operation were condensed into a pair of duty cycles, an 80-mile cycle and a 100-mile cycle representative of the daily operation of U.S. class 3-6 commercial pickup and delivery trucks. Using novel machine learning clustering methods combined with mileage-based weighting, these composite representative cycles correspond to 90th and 95th percentiles for daily vehicle miles traveled by the vehicles observed. In addition to including vehicle speed vs time drive cycles, in an effort to better represent the environmental factors encountered by pickup and delivery vehicles operating across the United States, a nationally representative grade profile and key status information were also appended to the speed vs. time profiles to produce a 'work day' cycle that captures the effects of vehicle dynamics, geography, and driver behavior which can be used for future design, development, and validation of technology.
Authors: Duran, A.; Li, K.; Kresse, J.; Kelly, K.
Analysis of Fast Charging Station Network for Electrified Ride-Hailing Services. SAE Paper No. 2018-01-0667
4/3/2018
Today's electric vehicle (EV) owners charge their vehicles mostly at home and seldom use public direct current fast charger (DCFCs), reducing the need for a large deployment of DCFCs for private EV owners. However, due to the emerging interest among transportation network companies to operate EVs in their fleet, there is great potential for DCFCs to be highly utilized and become economically feasible in the future. This paper describes a heuristic algorithm to emulate operation of EVs within a hypothetical transportation network company fleet using a large global positioning system data set from Columbus, Ohio. DCFC requirements supporting operation of EVs are estimated using the Electric Vehicle Infrastructure Projection tool. Operation and installation costs were estimated using real-world data to assess the economic feasibility of the recommended fast charging stations. Results suggest that the hypothetical transportation network company fleet increases daily vehicle miles traveled per EV with less overall down time, resulting in increased demand for DCFC. Sites with overhead service lines are recommended for hosting DCFC stations to minimize the need for trenching underground service lines. A negative relationship was found between cost per unit of energy and fast charging utilization, underscoring the importance of prioritizing utilization over installation costs when siting DCFC stations. Although this preliminary analysis of the impacts of new mobility paradigms on alternative fueling infrastructure requirements has produced several key results, the complexity of the problem warrants further investigation.
Authors: Wood, E.; Rames, C.; Kontou, E.; Motoaki, Y.; Smart, J.; Zhou, Z.
Leveraging Big Data Analysis Techniques for U.S. Vocational Vehicle Drive Cycle Characterization, Segmentation, and Development. SAE Paper No. 2018-01-1199
4/3/2018
Under a collaborative interagency agreement between the U.S. Environmental Protection Agency and the U.S. Department of Energy (DOE), the National Renewable Energy Laboratory (NREL) performed a series of in-depth analyses to characterize on-road driving behavior including distributions of vehicle speed, idle time, accelerations and decelerations, and other driving metrics of medium- and heavy-duty vocational vehicles operating within the United States. As part of this effort, NREL researchers segmented U.S. medium- and heavy-duty vocational vehicle driving characteristics into three distinct operating groups or clusters using real-world drive cycle data collected at 1 Hz and stored in NREL's Fleet DNA database. The Fleet DNA database contains millions of miles of historical drive cycle data captured from medium- and heavy-duty vehicles operating across the United States. The data encompass existing DOE activities as well as contributions from valued industry stakeholder participants. For this project, data captured from 913 unique vehicles comprising 16,250 days of operation were drawn from the Fleet DNA database and examined. The Fleet DNA data used as a source for this analysis has been collected from a total of 30 unique fleets/data providers operating across 22 unique geographic locations spread across the United States. This includes locations with topographies ranging from the foothills of Denver, Colorado, to the flats of Miami, Florida. This paper includes the results of the statistical analysis performed by NREL and a discussion and detailed summary of the development of the vocational drive cycle weights and representative transient drive cycles for testing and simulation. Additional discussion of known limitations and potential future work is also included.
Authors: Duran, A.; Phillips, C.; Perr-Sauer, J.; Kelly, K.; Konan, A.