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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.
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.
Clean Cities Alternative Fuel Price Report, January 2018
3/29/2018
The Clean Cities Alternative Fuel Price Report for January 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 January 1, 2018 and January 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 1 cent from $2.49 to $2.50; diesel increased 20 cents from $2.76 to $2.96; CNG remained the same at $2.17; ethanol (E85) decreased 4 cents from $2.10 to $2.06; propane increased 5 cents from $2.78 to $2.83; and biodiesel (B20) increased 16 cents from 2.68 to $2.84.
According to Table 3, CNG is $.33 less than gasoline on an energy-equivalent basis, while E85 is $0.18 more than gasoline on an energy-equivalent basis.
Authors: Bourbon, E.
California Plug-In Electric Vehicle Infrastructure Projections: 2017-2025 - Future Infrastructure Needs for Reaching the State's Zero Emission-Vehicle Deployment Goals
3/27/2018
This report analyzes plug-in electric vehicle (PEV) infrastructure needs in California from 2017 to 2025 in a scenario where the State's zero-emission vehicle (ZEV) deployment goals are achieved by household vehicles. The statewide infrastructure needs are evaluated by using the Electric Vehicle Infrastructure Projection tool, which incorporates representative statewide travel data from the 2012 California Household Travel Survey. The infrastructure solution presented in this assessment addresses two primary objectives: (1) enabling travel for battery electric vehicles and (2) maximizing the electric vehicle-miles traveled for plug-in hybrid electric vehicles. The analysis is performed at the county-level for each year between 2017 and 2025 while considering potential technology improvements. The results from this study present an infrastructure solution that can facilitate market growth for PEVs to reach the State's ZEV goals by 2025. The overall results show a need for 99k-130k destination chargers, including workplaces and public locations, and 9k-25k fast chargers. The results also show a need for dedicated or shared residential charging solutions at multi-family dwellings, which are expected to host about 120k PEVs by 2025. An improvement to the scientific literature, this analysis presents the significance of infrastructure reliability and accessibility on the quantification of charger demand.
Authors: Bedir, A.; Crisostomo, N.; Allen, J.; Wood, E.; Rames, C.
Trip Energy Estimation Methodology and Model Based on Real-World Driving Data for Green Routing Applications
2/12/2018
A data-informed model to predict energy use for a proposed vehicle trip has been developed in this paper. The methodology leverages nearly 1 million miles of real-world driving data to generate the estimation model. Driving is categorized at the sub-trip level by average speed, road gradient, and road network geometry, then aggregated by category. An average energy consumption rate is determined for each category, creating an energy rates look-up table. Proposed vehicle trips are then categorized in the same manner, and estimated energy rates are appended from the look-up table. The methodology is robust and applicable to almost any type of driving data. The model has been trained on vehicle global positioning system data from the Transportation Secure Data Center at the National Renewable Energy Laboratory and validated against on-road fuel consumption data from testing in Phoenix, Arizona. The estimation model has demonstrated an error range of 8.6% to 13.8%. The model results can be used to inform control strategies in routing tools, such as change in departure time, alternate routing, and alternate destinations to reduce energy consumption. This work provides a highly extensible framework that allows the model to be tuned to a specific driver or vehicle type.
Authors: Holden, J.; Van Til, H.; Wood, E.; Zhu, L.; Gonder, J.; Shirk, M.
Life Cycle Energy and Greenhouse Gas (GHG) Emission Effects of Biodiesel in the United States with Induced Land Use Change Impacts
1/10/2018
Researchers conducted updated simulations to depict a life cycle analysis (LCA) of biodiesel production from soybeans and other feedstocks in the United States. The study addressed in detail the interaction between LCA and induced land use change (ILUC) for biodiesel. Relative to conventional petroleum diesel, soy biodiesel could achieve 76% reduction in GHG emissions without considering ILUC, or 66%-72% reduction in overall GHG emissions when various ILUC cases were considered. Soy biodiesel's fossil fuel consumption rate was also 80% lower than its petroleum counterpart. Furthermore, this study examined the cause and the implication of each key parameter affecting biodiesel LCA results using a sensitivity analysis, which identified the hot spots for fossil fuel consumption and GHG emissions of biodiesel so that future efforts can be made accordingly. Finally, researchers also investigated biodiesel produced from other feedstocks (canola oil and tallow) to contrast with soy biodiesel and petroleum diesel.
Authors: Chen, R.; Qin, Z.; Han, J.; Wang, M.; Taheripour, F.; Tyner, W.; O'Connor, D.; Duffield, J.
Notes: This Bioresource Technology article (Vol. 251 (2018): pp. 249-258) is copyrighted by Elsevier B.V. and only available by accessing it through Science Direct.
Navigation API Route Fuel Saving Opportunity Assessment on Large-Scale Real-World Travel Data for Conventional Vehicles and Hybrid Electric Vehicles: Preprint
12/22/2017
The green routing strategy instructing a vehicle to select a fuel-efficient route benefits the current transportation system with fuel-saving opportunities. This paper introduces a navigation API route fuel-saving evaluation framework for estimating fuel advantages of alternative API routes based on large-scale, real-world travel data for conventional vehicles (CVs) and hybrid electric vehicles (HEVs). The navigation APIs, such Google Directions API, integrate traffic conditions and provide feasible alternative routes for origin-destination pairs. This paper develops two link-based fuel-consumption models stratified by link-level speed, road grade, and functional class (local/non-local), one for CVs and the other for HEVs. The link-based fuel-consumption models are built by assigning travel from a large number of GPS driving traces to the links in TomTom MultiNet as the underlying road network layer and road grade data from a U.S. Geological Survey elevation data set. Fuel consumption on a link is calculated by the proposed fuel consumption model. This paper envisions two kinds of applications: 1) identifying alternate routes that save fuel, and 2) quantifying the potential fuel savings for large amounts of travel. An experiment based on a large-scale California Household Travel Survey GPS trajectory data set is conducted. The fuel consumption and savings of CVs and HEVs are investigated. At the same time, the trade-off between fuel saving and time saving for choosing different routes is also examined for both powertrains.
Authors: Zhu, L.; Holden, J.; Gonder, J.
Clean Cities Alternative Fuel Price Report, October 2017
11/29/2017
The Clean Cities Alternative Fuel Price Report for October 2017 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 October 1, 2017 and October 16, 2017, 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 23 cents from $2.26 to $2.49; diesel increased 29 cents from $2.47 to $2.76; CNG price increased 2 cents from $2.15 to $2.17; ethanol (E85) increased 11 cents from $1.99 to $2.10; propane decreased 6 cents from $2.84 to $2.78; and biodiesel (B20) has increased 19 cents from 2.49 to $2.68.
According to Table 3, CNG is $.32 less than gasoline on an energy-equivalent basis, while E85 is $0.24 more than gasoline on an energy-equivalent basis.
Authors: Bourbon, E.
Fuel Cell Buses in U.S. Transit Fleets: Current Status 2017
11/21/2017
This report, published annually, summarizes the progress of fuel cell electric bus (FCEB) development in the United States and discusses the achievements and challenges of introducing fuel cell propulsion in transit. The report provides a summary of results from evaluations performed by the National Renewable Energy Laboratory. This annual status report combines results from all FCEB demonstrations, tracks the progress of the FCEB industry toward meeting technical targets, documents the lessons learned, and discusses the path forward for commercial viability of fuel cell technology for transit buses. These data and analyses help provide needed information to guide future early-stage research and development. The 2017 summary results primarily focus on the most recent year for each demonstration, from August 2016 through July 2017. The primary results presented in the report are from five demonstrations of two different fuel-cell-dominant bus designs: Zero Emission Bay Area Demonstration Group led by Alameda-Contra Costa Transit District (AC Transit) in California; American Fuel Cell Bus (AFCB) Project at SunLine Transit Agency in California; AFCB Project at the University of California at Irvine; AFCB Project at Orange County Transportation Authority; and AFCB Project at Massachusetts Bay Transportation Authority.
Authors: Eudy, L.; Post, M.
Utility Investment in Electric Vehicle Charging Infrastructure: Key Regulatory Considerations
11/13/2017
The report provides an overview of the accelerating electrification of the transportation sector and explores the role of state utility regulators in evaluating potential investments by electric utilities in plug-in electric vehicle (PEV) charging infrastructure. The report identifies key considerations for regulators, including the amount of charging infrastructure needed to support PEVs, ways that regulators can help ensure equitable access to charging infrastructure, and opportunities to maximize the benefits of utility investment in charging infrastructure.
Authors: Allen, P.; Van Horn, G.; Goetz, M.; Bradbury, J.; Zyla, K.
What Fleets Need to Know About Alternative Fuel Vehicle Conversions, Retrofits, and Repowers
10/17/2017
Many fleet managers have opted to incorporate alternative fuels and advanced vehicles into their lineup. Original equipment manufacturers (OEMs) offer a variety of choices, and there are additional options offered by aftermarket companies. There are also a myriad of ways that existing vehicles can be modified to utilize alternative fuels and other advanced technologies. Vehicle conversions and retrofit packages, along with engine repower options, can offer an ideal way to lower vehicle operating costs. This can result in long term return on investment, in addition to helping fleet managers achieve emissions and environmental goals. This report summarizes the various factors to consider when pursuing a conversion, retrofit, or repower option.
Authors: Kelly, K.; Gonzales, J.
Biodiesel Basics
9/29/2017
This fact sheet (updated for 2017) provides a brief introduction to biodiesel, including a discussion of biodiesel blends, which blends are best for which vehicles, where to buy biodiesel, how biodiesel compares to diesel fuel in terms of performance, the difference between biodiesel and renewable diesel, how biodiesel performs in cold weather, whether biodiesel use will plug vehicle filters, how long-term biodiesel use may affect engines, biodiesel fuel standards, and whether biodiesel burns cleaner than diesel fuel. The fact sheet also dismisses the use of vegetable oil as a motor fuel.
Compressed Natural Gas Vehicle Maintenance Facility Modification Handbook
9/28/2017
To ensure the safety of personnel and facilities, vehicle maintenance facilities are required by law and by guidelines of the National Fire Protection Association (NFPA) and the International Fire Code (IFC) to exhibit certain design features. They are also required to be fitted with certain fire protection equipment and devices because of the potential for fire or explosion in the event of fuel leakage or spills. All fuels have an explosion or fire potential if specific conditions are present.
This handbook covers the primary elements that must be considered when developing a CNG vehicle maintenance facility design that will protect against the ignition of natural gas releases. It also discusses specific protocols and training needed to ensure safety.
Authors: Kelly, K.; Melendez, M.; Gonzales, J.; Lynch, L.; Boale, B.; Kohout, J.
Designing a Successful Transportation Project: Lessons Learned from the Clean Cities American Recovery and Reinvestment Act Projects
9/27/2017
The largest source of funding for alternative fuel vehicle and infrastructure projects in the U.S. Department of Energy's Clean Cities program's history came from the American Recovery and Reinvestment Act (Recovery Act). In 2009, the 25 cost-share projects totaled nearly $300 million in federal government investment. This effort included the involvement of 50 Clean Cities coalitions and their nearly 700 stakeholder partners who provided an additional $500 million in matching funds to support projects in their local communities. In total, those 25 projects established 1,380 alternative fueling stations and put more than 9,000 alternative fuel and advanced technology vehicles on the road. Together, these projects displaced 154 million gasoline gallon equivalents (GGE) of petroleum and averted 254,000 tons of greenhouse gas (GHG) emissions, while supporting U.S. energy independence and contributing to regional economic development. During post-project interviews, project leaders consistently cited a number of key components - ranging from technical and logistical factors, to administrative capabilities - for accomplishing an effective and impactful project. This report summarizes the high-level project design and administrative considerations for conducting a successful transportation project.
Authors: Kelly, K.; Singer, M.
Analysis of the Effect of ZEV Policies: State Level Incentives and the California Zero-Emission Vehicle Regulations
9/7/2017
This report assesses the effect of state-level policies on the sales of zero-emission vehicles (ZEVs) and plug-in hybrid electric vehicles (PHEVs). Two analysis approaches are applied. The first approach assesses the potential effect of state-level incentives through quantification of the monetary value of ZEV and PHEV incentives and comparison of these values to state-level sales of these vehicles. The second approach focuses on the effect of California ZEV regulations on sales in California and in the nine other states that have adopted these regulations. ZEV and PHEV sales in these ten states are projected through 2025 under a variety of scenarios based on the regulations and associated historic trends in sales and credit balances earned under these regulations.
