HOF Car
A turbocharged gasoline direct injection vehicle is being modified to implement technologies such as high compression pistons to take advantage of the higher octane fuel.

High Octane Fuel Study

In vehicles designed for its use, high octane fuel blends have the potential to increase vehicle efficiency through improved knock suppression. When the high-octane blend is made with 25-40% ethanol by volume, efficiency improvements of 5-10% are sufficient to offset the reduced vehicle range often associated with the decreased volumetric energy density of the fuel (such as with flexible-fuel vehicles (FFVs) fueled with E85). The prospects for a high-octane, mid-level ethanol blend are attractive because it could be used legally in the 18 million FFVs currently on the road. Thus the current FFV fleet could provide an immediate market for the new fuel so that it is widely available as high-efficiency vehicles designed to use it are entering the market.

Project Details

The Bioenergy Technologies Office of DOE EERE has sponsored a “scoping study” to assess the potential of high-octane fuel (HOF) to assess its potential to reduce energy consumption and greenhouse gas (GHG) emissions, and to understand barriers to its successful market introduction. The goal was to provide information about the benefits of bringing this new fuel to the market, barriers to its adoption, and strategies for market introduction.

The current project, which began in late FY 2013 and culminates in early FY 2016, uses the combined expertise of Argonne National Laboratory, the National Renewable Energy Laboratory, and the Oak Ridge National Laboratory. It builds upon ongoing work at these national labs funded by DOE.

Task Descriptions

The HOF project consists of the following integrated tasks:

Efficiency Gains of HOF in Dedicated Vehicles: Quantify the fuel economy benefits of HOF at the vehicle level. Significant efficiency improvements are possible through a combination of improved engine thermal efficiency and improved system efficiency from downspeeding and downsizing.

Description of Properties for Engine Knock Resistance: Develop a description of fuel knocking resistance that considers octane numbers and heat of vaporization; include the development of methods of measuring the heat of vaporization of ethanol–gasoline blends.

Effects of HOF on Legacy FFVs: Determine the effects of high-octane gasoline blends, such as blends of gasoline with 25-40% ethanol (E25-E40) on legacy FFVs. Demonstrating a performance benefit in legacy FFVs would help in marketing ethanol blends for the legacy FFV fleet, which could bolster development of the infrastructure for fueling future vehicles specifically designed for this fuel.

Analysis of Energy and GHG Emissions and Modeling of Refinery Impacts: Conduct petroleum refinery simulations for various ethanol blending levels and HOF market shares. Evaluate the “well-to-wheels” energy and GHG effects of HOF use, accounting for vehicle efficiency gains, refinery operation changes, and the blending effects of ethanol.

Market Analysis: Identify and assess the economic, logistical, behavioral, and regulatory barriers to introducing HOF to the market and ways to address these barriers during a transition period. Stakeholders were engaged to help identify barriers and ways to overcome them and to estimate their potential impact on dedicated HOF vehicle sales and ethanol use.

Infrastructure Assessment: Work with stakeholders to assess the compatibility of mid-level ethanol blends with the existing storage and fueling infrastructure.

Evaluation of Cost Reduction Potential of HOF Blendstocks: Evaluate the potential to use natural gasoline as a low-cost blendstock for HOF.

Pertinent Findings and Outcomes

  • E25 and E40 would achieve volumetric fuel economy parity with today’s E10 with a 5 and 10% improvement in vehicle efficiency, respectively (i.e., fuel economy would be the same using HOF as today’s vehicle using E10, and so every gallon of ethanol used in HOF would displace a full gallon of gasoline.)
  • Fuel efficiency gains of up to 10% over E10 were demonstrated in vehicles with turbocharged, direct-injected engines. Operating engines in more efficient but more knock-prone conditions—through downspeeding, downsizing, and increasing the compression ratio—improves efficiency with HOF. The exact fuel economy benefit will vary depending on ultimate engine/vehicle design and driving conditions.
  • Measurements of heat of vaporization of ethanol blended with a range of gasoline blendstocks, including natural gasoline; show that there is little difference between the hydrocarbon components and that the major factors affecting ethanol blend heat of vaporization are ethanol content and temperature. Research is ongoing under other DOE programs to understand how octane number and heat of vaporization interact for fuel knock resistance.
  • Most legacy FFVs offer a performance benefit (i.e., improved acceleration) using HOF with no engine modifications required. This finding is a potential marketing pathway for introducing high octane mid-level blends, because they are legal to use in today’s FFV fleet. For “normal driving,” fuel economy using HOF was proportional to the energy density of the fuel.
  • The efficiency gain of HOF overwhelmingly overtakes the potential increase in refinery GHG emissions for HOF production, resulting in net GHG reductions by HOF.
  • Modeling further suggests that even under very aggressive market penetration assumptions, the availability of ethanol feedstocks does not limit the growth of the market. Fuel retailers’ willingness to invest in HOF equipment does limit market penetration in many scenarios. In scenarios where the latter is not a limiting factor, the construction rate of biorefineries (and technology advancement for second-generation ethanol) tends to be a limiting factor in early years, and HOF vehicle adoption tends to be the limiting factor in later years.
  • Modeling further suggests that even under very aggressive market penetration assumptions, the availability of ethanol feedstocks does not limit the growth of the market. Fuel retailers’ willingness to invest in HOF equipment does limit market penetration in many scenarios. In scenarios where the latter is not a limiting factor, the construction rate of biorefineries (and technology advancement for second-generation ethanol) tends to be a limiting factor in early years, and HOF vehicle adoption tends to be the limiting factor in later years.
  • The use of E25–E40 for producing HOF allows for greater market penetration of HOF than is available through E10 HOF.
  • Producing HOF with E10, E25 or E40 in petroleum refineries causes minimal impact on overall refinery efficiency. However, if HOF market penetration is significant, petroleum refineries will find it hard to meet the high demand for HOFs without the use of higher-ethanol blends (e.g., E25 and E40).
  • Based on our model analysis, optimized HOF vehicles can achieve a substantial market share (43 to 79% of vehicle stock by 2035) and can consume significant quantities of ethanol (up to 30 billion gallons per year). The extent of market success for the vehicles and fuel varies widely depending on the scenario and underlying assumptions.
  • Although the retail fueling station infrastructure is not inherently compatible with mid-level ethanol blends today, materials and equipment are available that are compatible with 25–40% ethanol blends. The cost of dispensing equipment is substantially less for E25.
  • Nearly all fuel terminals store ethanol and while there are no technical issues for storing more ethanol there are considerations including tank availability—nearly all are in use and a considerable amount are leased through long term contract to terminal customers. There could be space constraints for additional tanks and ethanol unloading facilities and the regulatory process for these additions are lengthy.
  • An empirical model was developed to estimate fuel properties using natural gasoline as a blendstock.
  • Natural gasoline is a potential low-cost hydrocarbon blendstock for FFV fuels and HOF, if blended with sufficient ethanol.

GHG reductions for two sets of vehicle efficiency improvement assumptions are shown.

Assuming 5% improvement in gasoline-equivalent fuel economy (mpgge) results in advanced E25 vehicles having volumetric fuel economy parity with today’s vehicles with E10.

HOF Chart
Well to wheel Greenhouse Gas analysis shows the reductions with GHG using HOF as a function of efficiency improvements, ethanol content and source

High Octane Fuel Content in KDF

Title Abstract Published
Compatibility Study for Plastic, Elastomeric, and Metallic Fueling Infrastructure Materials Exposed to Aggressive Formulations of Isobutanol-Blended Gasoline

The Energy Independence and Security Act (EISA) of 2007 is an omnibus energy policy law designed to move the United States toward greater energy security and independence. A key provision of EISA is the Renewable Fuel Standard (RFS), which requires the nation to use 36 billion gallons per year (...

2012
Experimental Investigation of Spark-Ignited Combustion with High-Octane Biofuels and EGR. 1. Engine Load Range and Downsize Downspeed Opportunity

The present study experimentally investigates spark-ignited combustion with 87 AKI E0 gasoline in its neat form
and in midlevel alcohol−gasoline blends with 24% vol/vol isobutanol−gasoline (IB24) and 30% vol/vol ethanol−gasoline (E30).
A single-cylinder research engine was used...

2012
Compatibility Assessment of Elastomeric Infrastructure Materials with Neat Diesel and a Diesel Blend containing 20 Percent Fast Pyrolysis Bio-oil

The compatibility of elastomer materials used in fuel storage and dispensing applications was determined for an off-highway diesel
fuel and a blend containing 20% bio-oil (Bio20) derived from a fast pyrolysis process. (This fuel blend is not to be confused with B20,
which is a...

2014
Experimental Investigation of Spark-Ignited Combustion with High-Octane Biofuels and EGR. 2. Fuel and EGR Effects on Knock-Limited Load and Speed

The present study experimentally investigates spark-ignited combustion with 87 AKI E0 gasoline in its neat form
and in midlevel alcohol−gasoline blends with 24% vol/vol isobutanol−gasoline (IB24) and 30% vol/vol ethanol−gasoline (E30).
A single-cylinder research engine is used with...

2012
Intermediate Alcohol-Gasoline Blends, Fuels for Enabling Increased Engine Efficiency and Powertrain Possibilities

The present study experimentally investigates spark-ignited combustion with 87 AKI E0 gasoline in its neat form and in
mid-level alcohol-gasoline blends with 24% vol./vol. iso-butanol-gasoline (IB24) and 30% vol./vol. ethanol-gasoline (E30).
A single-cylinder research engine is...

2013
The Impact of Low Octane Hydrocarbon Blending Streams on the Knock Limit of E85

Ethanol is a very attractive fuel from an end-use perspective because it has a high chemical octane number and a high
latent heat of vaporization. When an engine is optimized to take advantage of these fuel properties, both efficiency and
power can be increased through higher...

Ethanol Blends and Engine Operating Strategy Effects on Light-Duty Spark-Ignition Engine Particle Emissions

Spark-ignition (SI) engines with direct-injection (DI) fueling can improve fuel economy and vehicle power beyond
that of port fuel injection (PFI). Despite this distinct advantage, DI fueling often increases particle number emissions, such that SI
exhaust may be subject to future...

2010
Investigation of Knock Limited Compression Ratio of Ethanol Gasoline Blends

Ethanol offers significant potential for increasing the
compression ratio of SI engines resulting from its high octane
number and high latent heat of vaporization. A study was
conducted to determine the knock limited compression ratio
of ethanol - gasoline blends to...

2010
Compatibility Study for Plastic, Elastomeric, and Metallic Fueling Infrastructure Materials Exposed to Aggressive Formulations of Ethanol-Blended Gasoline

The Energy Independence and Security Act (EISA) of 2007 is an omnibus energy policy law designed to
move the United States toward greater energy security and independence. A key provision of EISA is the
Renewable Fuel Standard (RFS) which requires the nation to use 36 billion...

2011
Analysis of Underground Storage Tank System Materials to Increased Leak Potential Associated with E15 Fuel

The Energy Independence and Security Act (EISA) of 2007 was an omnibus energy policy law designed to move the United States toward greater energy security and independence.1 A key provision of EISA modified the Renewable Fuel Standard (RFS) which requires the nation to increase the volume of...

2011
Elastomer Compatibility to Gasoline Containing Intermediate Levels of Ethanol

The compatibility of elastomer materials used in fuel dispensers was assessed for a gasoline standard containing 0, 10, 17, and 25 volume percent of aggressive ethanol. Specimens of fluorocarbon, fluorosilicone, acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), silicone...

2010
Compatibility of elastomers with test fuels of gasoline blended with ethanol

This article summarises the compatibility of six elastomers – used in fuel
storage and delivery systems – with test fuels representing gasoline blended
with up to 85% ethanol. Individual coupons were exposed to test fuels for four
weeks to achieve saturation. The change in...

2011
Intermediate Ethanol Blends Infrastructure Materials Compatibility Study: Elastomers, Metals, and Sealants

The Energy Independence and Security Act (EISA) of 2007 was an omnibus energy policy law designed
to move the United States toward greater energy security and independence. A key provision of EISA is
the Renewable Fuel Standard (RFS) which requires the nation to use 36 billion...

2010
Preliminary Compatibility Assessment of Metallic Dispenser Materials for Service in Ethanol Fuel Blends

The compatibility of selected metals representative of those commonly used in dispensing
systems was evaluated in an aggressive E20 formulation (CE20a) and in synthetic gasoline
(Reference Fuel C) in identical testing to facilitate comparison of results. The testing was
...

2009