The DOE Bioenergy Technologies Office initiated a collaborative research program between Oak Ridge National Laboratory (ORNL), the National Renewable Energy Laboratory (NREL), and Argonne National Laboratory (ANL) to investigate HOF in late 2013. The program objective was to provide a quantitative picture of the barriers to adoption of HOF and the highly efficient vehicles it enables, and to quantify the potential environmental and economic benefits of the technology.
High Octane Fuel
The Bioenergy Technologies Office of the U.S. Department of Energy Office of Energy
Efficiency and Renewable Energy sponsored a scoping study to assess the potential of ethanolbased
high octane fuel (HOF) to reduce energy consumption and greenhouse gas emissions.
HOF blends used in an engine designed for higher octane have the potential to increase vehicle
energy efficiency through improved knock suppression. When the high-octane blend is made
with 25%–40% ethanol by volume, this energy efficiency improvement is potentially sufficient
to offset the reduced vehicle range often associated with the decreased volumetric energy density
of ethanol. With this scenario in mind, the purpose of this study is to assess the ability of the fuel
supply chain to accommodate more ethanol at fuel terminals. Fuel terminals are midstream in the
transportation fuel supply chain and serve to store and distribute fuels to end users. The study
does not cover the impacts on ethanol and gasoline markets supply and demand or other parts of
the fuel supply chain.
This report summarizes terminal equipment, operations, statistics, and regulations. It serves
largely to provide a background on how terminals operate and opportunities for handling greater
volumes of ethanol. As a part of this study, the National Renewable Energy Laboratory
interviewed companies who own terminals and visited several terminals to gain insight into their
operations, how ethanol is handled, any issues with ethanol storage, and the potential for
terminals to store more ethanol.
This project looks at the potential of blending ethanol with natural gasoline to produce Flex-Fuels (ASTM D5798-13a) and high-octane, mid-level ethanol blends. Eight natural gasoline samples were collected from pipeline companies or ethanol producers around the United States.
The objective of this work was to measure knock resistance metrics for ethanol-hydrocarbon blends with a primary focus on development of methods to measure the heat of vaporization (HOV). Blends of ethanol at 10 to 50 volume percent were prepared with three gasoline blendstocks and a natural gasoline.
High-octane fuels (HOFs) such as mid-level ethanol blends can be leveraged to design vehicles with increased engine efficiency, but producing these fuels at refineries may be subject to energy efficiency penalties. It has been questioned whether, on a well-to-wheels (WTW) basis, the use of HOFs in the vehicles designed for HOF has net greenhouse gas (GHG) emission benefits.
The United States government has been promoting increased use of biofuels, including ethanol from non-food feedstocks, through policies contained in the Energy Independence and Security Act of 2007. The objective is to enhance energy security, reduce greenhouse gas (GHG) emissions, and provide economic benefits. However, the United States has reached the ethanol blend wall, where more ethanol is produced domestically than can be blended into standard gasoline. Nearly all ethanol is blended at 10 volume percent (vol%) in gasoline. At the same time, the introduction of more stringent standards for fuel economy and GHG tailpipe emissions is driving research to increase the efficiency of spark ignition (SI) engines. Advanced strategies for increasing SI engine efficiency are enabled by higher octane number (more highly knock-resistant) fuels. Ethanol has a research octane number (RON) of 109, compared to typical U.S. regular gasoline at 91–93. Accordingly, high octane number ethanol blends containing from 20 vol% to 40 vol% ethanol are being extensively studied as fuels that enable design of more efficient engines. These blends are referred to as high-octane fuel (HOF) in this report. HOF could enable dramatic growth in the U.S. ethanol industry, with consequent energy security and GHG emission benefits, while also supporting introduction of more efficient vehicles. HOF could provide the additional ethanol demand necessary for more widespread deployment of cellulosic ethanol. However, the potential of HOF can be realized only if it is adopted by the motor fuel marketplace. This study assesses the feasibility, economics, and logistics of this adoption by the four required participants—drivers, vehicle manufacturers, fuel retailers, and fuel producers. It first assesses the benefits that could motivate these participants to adopt HOF. Then it focuses on the drawbacks and barriers that these participants could face when adopting HOF and proposes strategies—including incentives and policies—to curtail these barriers. These curtailment strategies are grouped into scenarios that are then modeled to investigate their feasibility and explore the dynamics involved in HOF deployment. This report does not advocate for or against incentives or policies, but presents simulations of their effects.
This report evaluates infrastructure implications for a high-octane fuel, i.e., a blend of 25% denatured ethanol and 75% gasoline (E25) or higher (E25+), for use with a new high-efficiency type of vehicle. E25+ is under consideration due to federal regulations requiring the use of more renewable fuels and improvements in fuel economy. The existing transportation fuel infrastructure may not be completely compatible with a mid-level ethanol blend (blends above E15 up to E50). It is anticipated that a mid-level ethanol blend will face many of the same hurdles as E15, and a fuel above E25 will face additional barriers. Three questions need to be considered when introducing a new fuel to existing infrastructure: Is the infrastructure it compatible? Is it listed by a third party? Is it approved?
A significant amount of research and regulatory action has addressed these concerns with positive progress towards enabling the use of ethanol blends above 10% ethanol (E10) in existing and upgraded equipment. The U.S. Environmental Protection Agency’s Office of Underground Storage Tanks biofuels guidance allowed tank and associated equipment manufacturers to issue statements of compatibility (EPA 2011). This has resulted in the determination that the majority of existing tanks are capable of storing blends of up to E85 (a marketing term for high-blend ethanol [51%–83%]) or E100 (denatured fuel ethanol). Past research on ethanol fuels and issues with the introduction and use of ultra-low sulfur diesel led refueling equipment manufacturers to upgrade sealing materials in their products for safe and reliable performance over a range of fuels. However, although gasoline equipment is being designed to be more robust across a broader range of fuels, the Petroleum Equipment Institute stated that new stations are not opting to install E25 or E85 listed or manufacturer-approved equipment due to the greater cost of such equipment and the expectation of low demand for ethanol blends above E10.
The general consensus among industry groups and equipment manufacturers is that it will be easier and less costly to deploy fuel containing ethanol up to E25 than an E25+ fuel. Increasing the blend level will be met with reluctance by manufacturers, who have not yet profited from the development of E25 and E85 products. Equipment manufacturers interviewed in this study suggested a blend above E25 could use their E85 products. While this would be practical because this equipment is available, it is challenging for the marketplace as the price differential between E10 and E25 equipment is negligible compared with the price premium for E85-listed products. Table ES-1 summarizes estimated minimum costs for offering E10+ fuels at a retail station.
And while storage tanks may be compatible with these blends, a typical station will have three storage tanks: one dedicated to diesel and the other two storing regular and premium gasoline to offer regular, mid-grade (made by blending from the two tanks), and premium. In some instances, a station may have a tank dedicated to mid-grade storage that could be used to store an ethanol blend. Incorporating a new ethanol blend into the system presents a challenge to the station operator’s business model and cash flow. A station would need to decide between using an existing tank or adding a new tank.
Perhaps the most significant barrier is that stations are not required to keep records of equipment. This makes it difficult to determine if existing equipment is compatible with various ethanol blends. In addition, retail station owners have concerns about their liability in the event of misfueling. Small, independent retailers (which represent 63% of the stations) are unlikely to
Fact Sheet for High Octane Fuels: Challenges & Opportunities
The U.S. Department of Energy (DOE) is supporting engine and vehicle research to investigate the potential of high-octane fuels to improve fuel economy. Ethanol has very high research octane number (RON) and heat of vaporization (HoV), properties that make it an excellent spark ignition engine fuel. The prospects of increasing both the ethanol content and the octane number of the gasoline pool has the potential to enable improved fuel economy in future vehicles with downsized, downsped engines. This report describes a small study to explore the potential performance benefits of high octane ethanol blends in the legacy fleet. There are over 17 million flex-fuel vehicles (FFVs) on the road today in the United States, vehicles capable of using any fuel from E0 to E85. If a future high-octane blend for dedicated vehicles is on the horizon, the nation is faced with the classic chicken-and-egg dilemma. If today’s FFVs can see a performance advantage with a high octane ethanol blend such as E25 or E30, then perhaps consumer demand for this fuel can serve as a bridge to future dedicated vehicles.
Experiments were performed with four FFVs using a 10% ethanol fuel (E10) with 88 pump octane, and a market gasoline blended with ethanol to make a 30% by volume ethanol fuel (E30) with 94 pump octane. The research octane numbers were 92.4 for the E10 fuel and 100.7 for the E30 fuel. Two vehicles had gasoline direct injected (GDI) engines, and two featured port fuel injection (PFI). Significant wide open throttle (WOT) performance improvements were measured for three of the four FFVs, with one vehicle showing no change. Additionally, a conventional (non-FFV) vehicle with a small turbocharged direct-injected engine was tested with a regular grade of gasoline with no ethanol (E0) and a splash blend of this same fuel with 15% ethanol by volume (E15). RON was increased from 90.7 for the E0 to 97.8 for the E15 blend. Significant wide open throttle and thermal efficiency performance improvement was measured for this vehicle, which achieved near volumetric fuel economy parity on the aggressive US06 drive cycle, demonstrating the potential for improved fuel economy in forthcoming downsized, downsped engines with high-octane fuels.
Presentation at Biomass 2013 July 31 - August 1, 2013