Co-Optima Stakeholder Listening Day Summary Report
(U.S. Department of Energy) Bioenergy Technologies Office, in partnership with the Vehicle Technologies Office and DOE national laboratories, hosted a stakeholder listening day last June to concurrently investigate the optimization of fuels and vehicles. Formerly called “Optima,” this work is now called “Co-Optimization of Fuels & Engines” or “Co-Optima.” Outcomes from the listening day are now available online in the Co-Optima Stakeholder Listening Day Summary Report. See the report and visit the Co-Optima Web page for up-to-date information on these emerging efforts. READ MORE Download report
Excerpt from report: Co-Optima aims to provide DOE and stakeholders with the research and development (R&D) and analysis to enable (1) a definitive technical assessment of biofuel options that enable advanced SI engines, (2) new “market-pull” drivers that convey the value of advanced biofuels to consumers, (3) fuels that have lower greenhouse gas (GHG) emissions and expand the stable operating conditions for ACI (advanced compression ignition) drive cycles, and (4) a reduction of the technical barriers required for ACI vehicle market penetration. Co-Optima will also help enable the United States to meet 2013 Climate Action Plan goals on an accelerated time frame, serve as a catalyst to reinvigorate U.S. technology competitiveness, encourage job creation, provide lasting environmental benefits, and increase energy security.
The effort includes two thrusts:
Thrust I—Improve near-term conventional SI engine efficiency. High research octane number (RON) fuels enable more efficient, higher-performance operation via engine downsizing and boosting. Many biofuel blending components exhibit high RON and can be introduced into the market in the near to medium term for engines optimized to operate on those fuels. Fuel properties beyond RON, such as heat of vaporization, burn rate, viscosity, volatility, and energy density will also be characterized, and the complexity of their interactions mapped to evaluate the full value opportunity.
This thrust has lower risk relative to Thrust II because SI engines are in use today—although not tuned to take advantage of the potential new fuels.
Thrust II—Enable full operability ACI engines. Thrust II will provide the science and technology underpinnings needed to make new fuels compatible with commercially viable new ACI engine technologies. This engine platform, which includes kinetically- controlled and low-temperature combustion approaches, offers the promise of significantly greater thermal efficiencies with lower criteria-pollutant emissions, and presents attractive options for both light- and heavy-duty vehicles.
Fuel research will focus on low-GHG, advanced biofuel/petroleum blends. In addition, already-efficient,
conventional compression ignition (CI) engines can realize fuel economy increases enabled by improved,
low GHG-intensity fuels. Thrust II, to be conducted in parallel with Thrust I, presents a more complex technical challenge with higher potential risk and reward.
The research cycle for each thrust will include identifying fuel candidates, understanding their fuel characteristics and combustion performance, and determining market transformation requirements such as cost, GHG reduction, feedstock requirements, scalability, and infrastructure compatibility.
Isobutanol is an important fuel to consider due to its compatibility with current infrastructure, but
its importance as a building block for chemicals and higher-value products may diminish the case for its use as a fuel. There was considerable debate about how easy a move to higher ethanol blends and associated higher octane might be. Clarification is needed on the octane levels Co-Optima plans to target.
Concurrent Availability of Fuels and Engines:
Constant octane levels have prompted engine designers to be more creative; now it is time for octane to
play a bigger role in efficiency improvements. Cooptimization requires changes coordinated between
engine and fuel producers, which will rely upon market certainty as well as industry cooperation. When it comes to research octane number (RON), it will be necessary to consider factors including whether 100 RON is E10, E20, or E30; which fuel is right; and which fuel properties have the correct specifications. Some participants said that if 100 RON was available today, manufacture of compatible engines would be a given.
Identifying Combustion Mode and Fuel Candidates:
The goal of Co-Optima is to design the fuel and vehicle together to improve energy efficiency and reduce GHG emissions. A key function of Co-Optima will be to downselect technologies and fuel options, identifying the most promising scheme and associated fuel.
Participants also discussed the following:
• When new fuels are introduced to the market, the incumbent fuel is typically favored, due to engine changes required by new fuels. This may provide a convincing argument for using the same new fuel for Co-Optima’s Thrust I and Thrust II.
• An optimized system of fuels/engines might prove more tractable by blending fuels. Using two highly refined fuels (e.g., diesel and gasoline) can result in a less-refined fuel. However, the use of straight run gasoline and/or natural gasoline in advanced compression ignition engines may benefit refiners, and this fuel could be blended with ethanol to produce a high-octane fuel that also meets the needs of advanced SI engines. E0 is 50/50 regular/premium, but it is unclear if E0 meets drivability requirements.
• Ethanol has the distinct advantages of being present in the fuel supply now (comprising 10%
of gasoline) and being rapidly scalable. The fuel property requirements of naphtha with additives
would depend on the specific Thrust II technology. There is a diesel engine Thrust II technology
that is insensitive to fuel properties. Octane is controlled in the manufacturing process.
• If there is a very tight fuel specification, then the engines can be optimized for it. For example, more stringent diesel and biodiesel standards could improve heavy-duty engine fuel consumption and emissions. However, tighter specifications come at a well-to-tank CO2 and financial cost.
• All of the fuel streams need to optimize carbon reduction. Cultivation of different feedstocks produces different carbon footprints, but the fuels derived from these feedstocks are not significantly different.
• From the international standpoint, optimizing one engine in the United States would put pressure on other countries to adopt similar technology. READ MORE