Navigant Research Blog

Improving the Performance of Hybrids

— April 23, 2014

The fundamental goal of a hybrid powertrain is to improve fuel efficiency by recovering kinetic energy from the vehicle as it slows down and storing it to reuse later.  Traditional vehicles convert that energy to heat in the brakes and then let it disperse into the atmosphere.  Hybrid electric vehicles (HEVs) generate electricity via an electric motor and store it in batteries or ultracapacitors.  The resistance of the motor slows the vehicle.

An understanding of how the hybrid powertrain works is helpful for drivers who wish to maximize their efficiency on the road.  Being careful not to accelerate too hard and slowing down steadily without using the foundation brakes are techniques that have been used since HEVs first went into production in the late 1990s.  As they became more popular, some original equipment manufacturers had to deal with complaints from drivers who didn’t achieve the promised fuel economy.  Some of the deficit was due to driving technique – if you hit the brakes hard when driving, then the regeneration cannot take place, and energy will not be saved for reuse.

Hills Ahead

The basic hybrid system will deliver more fuel economy benefits to drivers who understand how to get the most out of it.  But there are limits.  Once the battery is fully charged, no more energy can be stored, and the vehicle is then no more efficient than its conventional counterpart.  It’s very difficult for a driver to work out how to get around this limitation.

However, Mercedes-Benz has done just that with its latest Intelligent HYBRID operating system, which was introduced in the S-Class in summer 2013, and is now available in the new 2014 C-Class.  These cars use data from their navigation systems to look ahead for hills.  When the vehicle detects a downhill stretch coming up, it knows that the hill presents a good opportunity to capture energy, so it activates the electric motor to start draining the traction battery.  Taking more of the power from the electric drive means that the engine uses less liquid fuel, improving fuel economy.

This advanced technology is a first for the consumer market.  Another application that uses the latest digital map data is Audi’s adaptive headlight system, which can anticipate upcoming curves to better illuminate the road ahead without dazzling oncoming vehicles.  Continental’s eHorizon system optimizes gear shifting to best handle the upcoming terrain.  Mercedes is the first to offer map-based efficiency technology in consumer vehicles.

These innovations will undoubtedly benefit vehicle owners by delivering improved fuel economy in real-world usage.  However, the standardized tests used by government agencies to help consumers compare vehicles are unlikely to register an improvement because they do not include going up and down hills, and are typically conducted on a chassis dynamometer, or “rolling road.”  Another reason to reevaluate how comparison testing is done.

 

U.S. National Parks and Electric Vehicles: A Match Made in Heaven?

— April 8, 2014

The U.S. Clean Cities program and the National Park Service (NPS) recently announced nine new projects to deploy clean vehicles at U.S. national parks. These projects are part of the Clean Cities National Park Initiative launched in 2010. The nine projects mainly feature plug-in electric vehicles (PEVs) and hybrid electric vehicles (HEVs).  Around 21 vehicles will be installed through the funding, including some low-speed electric vehicles (EVs).  The projects also include the installation of EV chargers for park visitors. While any move to make the U.S. parks cleaner is welcome, the relatively modest ambitions of this funding effort reflect the challenge that parks present in the adoption of EV or HEV technology.

Parks have long been an attractive target for greener transportation. This is not only for symbolic reasons, but also for practical reasons. Diesel and gas vehicles are noisy and disruptive. Park vehicles may spend time idling, which is both an emissions problem and a cost concern given the large amount of fuel essentially wasted during idling. These factors would seem to make PEV and HEV technology a good option, but to date, deployments have largely been pilot or demonstration programs and there has yet to be a full-scale shift toward electric drives at the U.S. parks.

A Building Barrier

One major barrier has been the lack of truly commercial vehicles available. As discussed in the Navigant Research report Hybrid and Electric Trucks, most of the traditional truck original equipment manufacturers (OEMs) are offering hybrid versions in the larger trucks classes that are not applicable to the park service. In the truck category, parks would primarily utilize utility trucks, pickup trucks, or vans and trucks outfitted to transport passengers.  These would be vehicles in the Class 2b light duty category or medium duty Classes 3-5, where, until recently, there was more attention focused on producing electrified vehicles for delivery service.

Even though pickup trucks are among the top-selling vehicle in the United States, U.S. OEMs have tailed off production of hybrid pickups and only ever offered demonstration models of plug-in trucks.  However, in the past 18 months, there has been an uptick in companies focused on these class levels and in applications with some applicability to national parks. In January, U.S. startup VIA Trucks announced a major commitment by Canadian company SunCountry to place VIA’s plug-in vans into passenger transport services at Best Western hotels. VIA also develops plug-in electric utility trucks, which will be used at several electric utilities in a pilot project funded in part by the U.S. Department of Energy (DOE). U.S. company Odyne Systems will be delivering 120 utility trucks through the same DOE funding; the plug-in system allows utility workers to avoid engine idling by running equipment off of the battery.

Looking at the larger class of passenger buses that are used in national parks, the biggest push is coming from China’s BYD, which has been targeting parks and transit agencies. While most of the company’s orders are outside of the United States, BYD is making a strong push for the U.S. market. After winning bids in Los Angeles and Long Beach, California, the company began to face major backlash from activists and its U.S. competitors. The Long Beach order was recently canceled, although, evidently, the reason was simply a paperwork glitch. In any case, this environment would make it difficult for the NPS to adopt these buses until BYD becomes more established in the United States through transit deployments like the one in Los Angeles.

While increased vehicle availability will help make electric and hybrid options more feasible for any park looking to convert, the issue of the price premium still looms large. With hybrids costing well over 25% more than conventional vehicles and electric buses often reaching a 100% price premium, cash-strapped public services like the NPS will likely find themselves unable to make the switch even if they want to. Lower-cost options, like propane, continue to see uptake in national parks for this reason. This also explains why the Clean Cities National Park Initiative is still necessary to move these vehicles into U.S. parks.

 

Flywheels Offer Hybrids a Mechanical Advantage

— April 4, 2014

It is often assumed that all hybrid vehicles must use a battery for energy storage.  But the essence of a hybrid powertrain is not necessarily engine-off operation, but to provide more efficient transportation over a stop/start journey drive cycle.  The key factor in this mode is to be able to recapture large amounts of energy very quickly and then reuse it, which requires high power density.  While batteries typically have a high energy density, they often do not respond well to high charge rates and may not be able to capture all the available energy from regenerative braking.  Larger vehicles, in particular, have a lot of kinetic energy to store when slowing down.

So the focus for hybrid vehicles is often high power density rather than high energy density.  It is this factor (as well as the lower cost) that has led some manufacturers, particularly Toyota, to continue installing nickel-metal hydride batteries when the rest of the industry has shifted to the higher energy density of the lithium ion battery.  But there are other options for higher power density, if total energy capacity is not an issue.  Ultracapacitors are one alternative and Navigant Research has produced a report on another option: Hydraulic Hybrid Vehicles.  However, a new alternative technology based on the flywheel is now in testing.

Powerful and Economical

Volvo Car Group has recently been conducting testing in the United Kingdom of a flywheel developed by Flybrid Automotive (now part of Torotrak) to determine the potential for fuel savings.  Initial results show a performance boost of 80 hp while improving fuel economy by up to 25%.  The testing uses real-world driving data from public roads and test tracks in both Sweden and the United Kingdom.  Volvo has installed the flywheel system on the rear axle of a front-wheel drive passenger car.  Under braking, the vehicle kinetic energy is used to spin a 6 kg carbon fiber flywheel at up to 60,000 rpm.  When the driver wants to accelerate again, the energy from the spinning flywheel drives the rear wheels directly via a specially designed transmission.

The benefits for the driver are that the engine can be switched off during some braking and accelerating maneuvers, plus there is extra power available when needed to supplement the internal combustion engine.  The Volvo test vehicle is about 1.5 seconds quicker than the standard vehicle going from 0 to 60 mph.

Mechanics of Storage

The Flybrid system uses the mechanical motion directly to power the transmission, so there are no energy losses transferring from one format to another.  Another type of flywheel system, developed for motor racing by Williams Hybrid Power (and since April 1, part of GKN), uses a flywheel driven by an electric motor.  Instead of storing energy chemically as in a battery, the energy is stored mechanically in the spinning flywheel and then converted back to electricity to be used by the electric drive motor.

Both systems use the same mechanical energy storage format and have to address the same issues.  Safety and reliability are important, as is longevity.  Cost is also important, and at present, the flywheel is a lot cheaper than a battery.  It’s good to see some alternative solutions being adopted by larger companies, and this topic will be covered in much more detail in our upcoming report on vehicle efficiency.

 

Electricity Pricing and the Economics of EVs

— April 2, 2014

The hottest global market for plug-in electric vehicles (PEVs) is Norway, where PEVs accounted for nearly 5.5% of all light duty vehicle sales in 2013.  Success of PEV sales in Norway has been credited to the country’s attractive purchase incentives and tax breaks, which include exemption from all non-recurring vehicle fees, annual road taxes, all public parking fees, and toll payments, along with free access to bus lanes.  While these incentives are appealing, equal credit goes to the massive price gap between the costs of petroleum fuels and electricity in the country.

One of the most attractive aspects of PEVs is that driving on electricity is significantly cheaper than driving on gasoline or diesel.  While this is largely true in most markets, the price difference can vary significantly by market.  The most meaningful variables in fuel cost returns are the retail price of petroleum-based fuels, the residential rates for electricity (since a vast majority of PEV charging is done at the owner’s home), and the average efficiency of new conventional vehicles compared to PEVs.

The Turkish Premium

The price of retail gasoline and diesel varies sharply from country to country.  The starkest example is in Turkey and Iran: in 2012, a gallon of gasoline cost $9.61 in Turkey (highest in the world) and $1.25 in neighboring Iran.  Electricity prices are also vastly different from country to country; residential electricity rates per kilowatt-hour (kWh) in France, which gets 80% of its electricity from nuclear power, are half the rates as those in Germany.  The variation in prices for each fuel determines which markets offer the best returns for PEV owners.

The best returns on fuel costs in Europe are in Norway and the worst are in Germany.  If the average new light duty vehicle in Europe has an mpg rating of 35 and the average new PEV has a miles per kWh rating of 2.7, then on a per-mile basis, Norwegian PEV owners save $0.16 per mile while German PEV owners save only $0.05.  Given that Germany’s incentives for PEVs are far less attractive than Norway’s, it’s not surprising that the Scandinavian country (population just over 5 million) still put around 1,500 more PEVs on the road last year than did Germany (population just over 80 million).

State to State

Among U.S. states (average new vehicle mpg is now 25) the best returns are in Indiana ($0.11 per mile) and the worst are in Hawaii ($0.03 per mile).  Given current government incentives, maintenance cost reductions, an annual vehicle mileage of 12,000, and an average $12,000 premium for PEVs, a battery electric vehicle (BEV) driven in Indiana nets a return in less than 4 years – twice as fast as one driven in Hawaii.

Fuel Costs per Mile of Fuel, Select Regions: 2014

Pricing-Economics of EVs blog (04-02-14)

(Source: Navigant Research)

Because PEV returns are so varied, local utilities can significantly affect markets by introducing time-of-use (TOU) electricity rates specific to PEV owners.  TOU rates, which incentivize off-peak electricity usage, can drastically reduce per kWh prices for PEV charging.  Residential TOU rates are limited, for now, to a few utilities in the United States.  Their adoption, however, is a win-win for utilities.  TOU rates can increase utility revenue by making market conditions for PEVs better, thus increasing demand for electricity, and TOU rates shift the increased demand to manageable off-peak hours.  The final outcome is one in which utilities make more money and drivers save more money.

 

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