Navigant Research Blog

Electric Turbochargers: The Next Big Thing in Fuel Efficiency

— October 23, 2014

The key to the next major advance in internal combustion engine fuel efficiency could well be the electric turbocharger.  At a recent fuel economy technology showcase at the U.S. Environmental Protection Agency (EPA) National Vehicle Emissions and Fuel Lab in Ann Arbor, Michigan, Valeo showed off the motor-driven turbo it will supply to an unannounced automaker.  The first production applications are scheduled to begin arriving in 2016, according to the company.

The aggressive expansion of fuel efficient technologies, such as electrification, multi-speed automatic transmissions, and engine downsizing, has played a major part in increasing miles per gallon.  The average fuel economy of the American new light duty vehicle fleet has improved by almost 25% over the past decade.  Meanwhile, gasoline direct injection and turbocharging have enabled engineers to cut engine displacement by 30% or more without sacrificing the performance that drivers have come to expect.  As of the 2014 model year, approximately 75% of Ford gasoline and diesel engines globally are turbocharged while 85% of Volkswagen engines are boosted.

Response Time

Part of the concept behind boosted engines is to use smaller engines with turbochargers that provide performance on-demand.  There has always been an inherent time lag, however, between the time the driver presses the accelerator and the generation of enough extra exhaust gas to spin up the turbo and provide boost.  Mechanically-driven superchargers eliminate much of the lag at the cost of substantial friction at higher speeds.

Replacing the exhaust-driven turbine side of the turbocharger with an electric motor provides a number of advantages, most notably in packaging, responsiveness, and operational flexibility.  One of the fuel economy benefits Valeo highlights is the combination of an electric turbo with the cylinder deactivation – i.e., the ability to shut off multiple cylinders under light loads in order to improve fuel efficiency.

The fuel savings achieved by shutting off unneeded cylinders can be quickly lost when driving on roads that aren’t completely flat.  Even a mild grade can cause an engine to switch back to running on all cylinders in order to produce enough torque to maintain speed.  “With an electric turbo, the engine management system can request small amounts of boost on-demand to increase torque while climbing a grade while keeping as many as half of the cylinders inactive,” Ronald Wegener, application engineering manager with Valeo, told me.  “This can yield up to a 10% improvement in efficiency.”

Valeo has developed versions of the device for both 12V and 48V electrical systems so that the turbo can also be used as part of a mild hybrid system during off-throttle conditions.  Intake air flowing through the compressor drives the motor to generate electricity, charging the battery.  Audi is using this as one of the two forms of energy recovery on its Le Mans-winning R18 e-tron race car.  Many of the current crop of Formula One cars have also adopted this approach.  Earlier this year, Audi announced that the next-generation Q7 TDI, scheduled for model year 2016, would be its first production application of the technology.

Shrinking Engines

Electric turbochargers also provide packaging benefits to engine designers.  Traditional turbos require complex plumbing to route exhaust gases to the turbine side of the turbo and feed the boosted intake charge to the other side of the engine.  Disconnecting the turbo from the exhaust allows designers to place the turbo wherever it fits best for packaging and performance.

Executives and engineers agree that while electric vehicles will gain market share in the coming years, internal combustion engines will likely remain the dominant powertrain choice in the transportation space at least through the 2020s.  With engines continuing to shrink, it seems likely that electric turbochargers will account for a growing share of the boosted engine market in the next decade.

 

In Ethanol, Cellulosic Coming To Push out Corn

— October 20, 2014

The last few months have been big for cellulosic biofuels in the United States.  The first of three commercial-scale cellulosic ethanol plants to come on line this year, Project Liberty, opened in Iowa in September.  In July, the U.S. Environmental Protection Agency (EPA) expanded the definition of the cellulosic biofuel pathway to include biogas used for transportation via compressed natural gas (CNG), liquefied natural gas (LNG), or electricity.  At full capacity, Project Liberty will produce 25 million gallons annually; the two other plants scheduled to open this year will run at 25 and 30 million gallons, respectively.  If the plants are successful, this could be the beginning of cellulosic ethanol supplanting corn-based ethanol’s hold in the U.S. biofuel market.

Cellulosic ethanol’s major advantage over corn-based ethanol is that its feedstock is organic material waste rather than food/grain.  This avoids controversial issues regarding food vs. fuel, and minimizes the conversion of arable land to farm land, which experts contend makes cellulosic ethanol far more environmentally sustainable and less politically divisive than corn-based ethanol.  The disadvantage of the fuel is that it’s ethanol.

Flat Gas

Ethanol’s end market is gasoline, primarily used for light duty vehicles in the United States and Brazil.  It can only supply up to 10% of the fuel in a vast majority of the vehicles in use in the United States due to regulatory constraints and reluctance on the part of automakers and fuel retailers to adopt higher ethanol-gasoline blends.  If gasoline consumption in the United States was growing, this aspect wouldn’t be a problem, but it’s not.

In Navigant Research’s reports, Global Fuels Consumption and Light Duty Vehicles, it is estimated that light duty vehicles account for 94% of gasoline consumption in the United States.  Over the next 10 years, the light duty vehicle fleet will become far more energy efficient, thanks to vehicle electrification, vehicle lightweighting, and engine downsizing.  The end result is that the amount of gasoline-ethanol blends consumed in 2023 will likely be 12% less than 2014 levels.

The Cellulosic Edge

Consumption of ethanol is driven by the Renewable Fuel Standard (RFS), which mandates specific volumes of biofuels be blended into the fuel supply.  The standard is adjusted each year to reflect anticipated industry production volumes by biofuel pathway, so that biofuel producers can be assured their product will be purchased by blenders.

Given cellulosic ethanol’s sustainability appeal over conventional ethanol, and the limited market in which these pathways compete, and despite the high cost of cellulosic compared to conventional ethanol, it’s likely that annual adjustments to the RFS will ensure that cellulosic production feeds into the U.S. fuel pool at the expense of conventional ethanol.  That means that the EPA may be inclined to lower conventional ethanol mandates against increases in cellulosic capacity – making cellulosic more valuable to blenders than conventional ethanol.  As a result, conventional U.S. ethanol will likely become an export fuel, going to foreign markets that currently make up a little over 45% of the global market.

 

Car-Free in Colorado: Living with an E-Bike

— October 20, 2014

After years of vehicle ownership, I decided about 3 months ago it was time for a change of pace.  Literally.  Tired of the plethora of (and seemingly continually rising) costs associated with owning a vehicle (parking, maintenance, insurance, repairs, registration fees, gasoline, etc.), I sold my car and used part of the funds to purchase an E3 Vibe electric bicycle (e-bike)  for $1,500 from Currie Technologies.  An e-bike is a traditional pedal bicycle with a battery pack that stores electricity, an electric motor for propulsion, and a user control attached to the handle bars for modifying the level of electrical assistance.

(Source: Currie Technologies)

Living in Boulder, Colorado certainly makes this transition much easier than in most U.S. cities.  An excellent bicycling infrastructure, a local carshare program, and comprehensive transit system all contribute to an excellent environment for going car-less.

Cost Analysis

With an upfront cost of $1,500, the e-bike will pay for itself after one year of avoided car insurance and gasoline expenses.  My monthly gasoline and insurance charges were about $130 combined ($80 for insurance, $50 for gas), totaling $1,560 per year.  This is more than the brand new e-bike cost itself, without even delving into the additional avoided costs of vehicle registration fees, parking, maintenance, and repairs.  Just as an example of potential additional costs of owning a vehicle, it’s estimated that in Colorado, the average cost of a common car repair (parts & labor) was $348.17 in 2011.

What about the operating costs for e-bikes? While many organizations estimate the cost of fully charging an e-bike from $0.10 to $0.20, other conservative estimates project that it costs just under $0.25 to charge an average e-bike battery from empty to full.  For me, this would happen about twice a week, since I’m usually charging the battery from half to full power 4 times per week (a 6.3 mile commute round trip usually drains the battery to a little over half power).  Using the conservative estimate of $0.25 to fully recharge the battery, electricity for recharging my e-bike would run about $26 per year ($0.50 multiplied by 52 weeks).  This (wishfully) assumes no winter in Colorado.  With a more realistic projection of biking to work three-quarters of the year, this reduces the annual charging cost to under $20.

Electric Hum

When the weather isn’t suitable for biking to work, I take the bus with a complimentary bus pass from my employer.  However, since I do need access to a vehicle on occasion, I have become a member of Boulder’s carsharing program, eGo CarShare.  So far, I am averaging about $20/month in rental fees, amounting to $240 per year.

Overall, becoming an e-bike owner has not only provided significant financial relief, but has also been an incredibly enjoyable experience.  I bike more often and travel longer distances than I would typically go on a traditional bike.  In addition, I get to confuse other cyclists with the humming sound of a 250W electric motor.

 

Truck Fuel Economy on the Rise

— October 20, 2014

The U.S. Environmental Protection Agency (EPA) has just published its 2014 fuel economy trends report, and though the news is generally positive, some potential storm clouds remain on the horizon for manufacturers.  While the overall average fleet fuel economy hit a record 24.1 mpg for the 2013 model year, the monthly update from the University of Michigan Transportation Research Institute (UMTRI) showed a 0.5 mpg drop in September 2014, equal to the 2012 to 2013 annual increase.

The long-term trend has definitely been upward.  Last year represented the eighth increase in the past 9 years for the American new vehicle fleet.  Automakers will have to maintain this momentum if they expect to hit the 2025 corporate average fuel economy target of 54.5 mpg.  Fortunately, attendees at a fuel economy technology showcase at the EPA emissions testing lab in Ann Arbor were all publicly confident that the targets were achievable.

As for the sudden drop in September, that can be explained by what are likely temporary market conditions that led to a significant uptick in full-size truck sales at General Motors (GM) and Chrysler.  As the 2014 model year drew to a close, combined sales of the Chevy Silverado and GMC Sierra jumped 46%, aided by incentives of up to $4,500.  Ram sales were also helped along by retail incentives of up to $3,000, as well as the popularity of the new Ram 1500 EcoDiesel.

From Steel to Aluminum

Sales of Ford’s F-series trucks were essentially flat, as the automaker began the transition to its all-new, aluminum-bodied 2015 F-150.  It appears that GM and Chrysler are hoping to grab some market share in the financially lucrative big truck segment in hopes that Ford would stumble in the complicated transition from steel to aluminum trucks.

At this point next year, even if truck sales continue to climb, we’re unlikely to see a similar drop-off in fuel economy, thanks to new technology in the segment.  The weight savings and new power plants for the Ford trucks are projected to deliver up to 20% better fuel efficiency than the steel-bodied versions.

Chrysler and GM also have to meet the new fuel economy standards.  Ram pickups are already available with ZF 8-speed transmissions, and GM is adding its first 8-speed automatic transmission to 2015 pickups with a 6.2-liter V8.  As GM ramps up production of the new 8L90 transmission, it will probably get paired with other engines as well.  GM and Ford also have a joint development program to produce 9- and 10-speed transmissions for trucks and other vehicles in the next few years.

Diesel Debuts

Chrysler is also building on the success of the 28 mpg Ram 1500 EcoDiesel by doubling production to 20% of its total production volume of trucks in 2015.  Ford is still awaiting final EPA certification on the 2015 F-150, but the 2.7-liter EcoBoost V6 is also expected to get a highway rating in the upper 20s.  GM’s new midsize Colorado and Canyon pickups are already rated at up to 27 mpg with a gasoline V6, and a diesel version is coming some time in 2015.  Ford is also offering a diesel engine option in the new Transit full-size vans that replace the E-series this year.  Ford will likely be closely following the sales trajectory for diesel engines in the Chrysler and GM trucks, as well as the next-generation Nissan Titan and Toyota Tundra, which will both be available with a Cummins-sourced 5.0-liter diesel V8.

With the huge sales volumes of pickup trucks in North America, lightweighting, advanced powertrains, and automatic stop-start, trucks will make a big contribution to reducing fossil fuel use in the next decade.

 

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