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ARB Expert ZEV Panel Bullish on Plug-in Hybrids

23 April 2007

The expert panel’s projections of achievement of global volumes. HEV = hybrid electric vehicle; PHEV = plug-in hybrid vehicle; FCEV = fuel cell electric vehicle; FPBEV = full performance battery electric vehicle; H2ICV = hydrogen internal combustion vehicle; CEV = city battery electric vehicle; NEV = neighborhood battery electric vehicle. Click to enlarge.

The expert panel convened in 2006 by the California Air Resources Board (ARB) to assess Zero Emission Vehicle (ZEV) technologies and then to advise the board has published its report, which will be considered at the upcoming board meeting 24-25 May in San Diego.

The year-long process—which included ARB’s ZEV Symposium last year (earlier post), resulted from the board’s direction to staff in 2003 to gather information to help determine whether or not a further adjustment to California’s ZEV program is warranted.

The ZEV Program. Created in 1990, the ZEV program required that 10% of new vehicle sales by large auto manufacturers have zero emissions, beginning with 1998 model-year vehicles. This ZEV requirement was included to catalyze efforts to commercialize sustainable transportation.

Manufacturers originally planned to meet the ZEV requirements with battery electric vehicles. The board modified the program in 1998 and 2001 to allow up to 60% of the requirement to be met with vehicles having extremely low emissions and specific attributes. In 2009, up to 85% of the requirements may be met with these vehicles. The most recent change in 2003 revised the percentage of ZEVs required to 11% starting in 2009, increasing to 16% in 2018. (An alternate path allows the requirement to be met by the production of specified numbers of fuel cell vehicles.)

The Expert Panel on PHEVs. The ZEV panel convened by ARB is chaired by Michael Walsh, and includes Dr. Fritz Kalhammer;  Bruce Kopf; Vernon Roan, Jr.; and David Swan. The panel’s work consisted primarily of extensive data collection followed by a critical assessment.

Overall, the panel determined that plug-in hybrids (PHEVs) are the most likely technology to reach large volume production the soonest.

It is the Panel’s opinion that PHEVs have the potential to provide significant direct societal benefits and are likely to become available in the near future. They may foster future mass market BEVs by stimulating energy battery development and conditioning mass market customers to accept plugging in...

The Panel’s projection is that PHEVs with modest energy storage capacity will be derived from HEVs and will proliferate rapidly, stimulating further development and cost reduction of energy batteries and leading to commercially viable PHEVs and, in the longer term, FPBEVs [Full Power Battery Electric Vehicles].

While PHEVs will continue to grow rapidly, as they have no functional limitations, FPBEVs will grow more slowly due to customer acceptance of limited range and long recharge time. NEVs [Neighborhood Electric Vehicles] are commercially viable now and will continue to grow, but will grow slowly due to limited functionality. CEVs [City Electric vehicles] will become commercially viable in Japan and Europe in the not too distant future due to lower hurdles for BEVs to overcome. CEVs may be offered in the US as energy batteries continue to mature, but growth will be slow due to functional limitations of BEVs in general, and the specific limitations of CEVs, especially urban freeway driving.

The intense effort on FCEVs [Fuel Cell Electric Vehicles] will result in technically capable vehicles by the 2015 to 2020 time frame, but successful commercialization is dependent on meeting challenging cost goals and the availability of an adequate hydrogen infrastructure. If that happens, FCEVs will grow rapidly, followed by some H2ICVs [Hydrogen Internal Combustion engine Vehicles], and some H2ICVs with FCAPUs [Fuel Cell Auxiliary Power Units].

As a long term ZEV outcome, the Panel can envision plug-in hybrid FCEVs, powered by sustainable electricity for shorter trips and sustainable hydrogen for longer trips.

The panel concluded that the major technical issue faced by PHEVs—in addition to the same issues faced by conventional hybrids—is the ability of the energy battery to endure the large number of deep cycles the battery must deliver over the life of the vehicle. (The largest overall issue is battery cost.)

A PHEV battery can operate in four primary modes:

  1. Grid-charging mode, which occurs when the vehicle is parked, is plugged into the grid and is charging the battery.

  2. Charge-Depleting EV only mode (CD-EV), which consists of discharging the battery during driving after being charged by the grid from a full state-of-charge (SOC) to a predetermined low SOC, allowing regenerative brake charging but not ICE charging.

  3. Charge-Depleting HEV mode (CD-HEV), which consists of discharging the battery during driving after being charged by the grid from a full SOC to a predetermined low SOC, allowing regenerative brake charging but not ICE charging (the ICE does supply power to the wheels when needed – similar to a HEV).

  4. Charge-Sustaining mode (CS), which consists of continuously varying the battery SOC between an upper and lower limit during driving, allowing both regenerative brake charging and ICE charging, the same as with a HEV, but around a much lower average SOC.

Battery cycle life when first operating in a charge depletion mode and then switching to operation in a charge sustaining mode around a relatively low average SOC is not completely known at this time. However, in the first laboratory tests, both NiMH and Li Ion medium energy/medium power batteries are approaching 2000 deep cycles when cycled in this mode.

Because a PHEV has an ICE to meet a portion of the vehicle’s range requirement and power demand, its battery can be smaller than a FPBEV, thus reducing the battery cost, weight and volume issues. However, because of their lower capacity, PHEV batteries are more likely to be fully discharged daily than FPBEV batteries, making cycle life requirements more severe...

Other technical issues for PHEVs flagged by the review panel include:

  • Definitions and standards for testing emissions and fuel economy.

  • Vehicle emissions if the internal combustion engine in the PHEV is forced to perform a cold start under high load.

  • Evaporative emissions if EV mode All-Electric Range (AER) is used.

The panel also considered a series hybrid plug-in configuration—i.e., similar to what GM proposed with its first Volt powertrain. The series PHEV can avoid the cold start emissions problem, but it requires a relatively large energy battery and a large, full performance, electric drive propulsion system, similar to a FPBEV or FCEV, according to the panel.

Compared to a FPBEV, it can use a smaller, more affordable battery and it does not have the driving range limitation issues. Compared to a parallel PHEV, it can operate the ICE at the optimum combination of speed and load necessary to achieve maximum efficiency (except for a short time for warm up), however, this efficiency advantage is reduced to some degree by a combination of generator, battery charging, battery discharging, and electric drive system efficiency losses before reaching the wheels. Compared to some other parallel hybrid systems, it is probably not suitable for vehicles intended for trailer towing.

Potential of battery technologies for HEV, PHEV and EV applications. Click to enlarge.

Battery Chemistries. The panel focused on three main ZEV enabling technologies: energy storage, hydrogen storage and fuel cells. On the energy storage side, the panel focused on batteries as the only viable energy storage option for zero and near-zero emission vehicles, at present and in the foreseeable future. The emphasis was on li-ion technologies because of their rapid technical progress and excellent potential to meet the energy storage requirements for full (including fuel cell) hybrid, plug-in hybrid, and full performance battery electric vehicles.

The panel also covered NiMH  batteries because of their near term importance for HEVs (including fuel cell HEVs) and their potential for PHEV applications. Finally, it examined the status of ZEBRA (sodium-nickel chloride) and lithium-sulfur batteries because of their near and, respectively, longer term potential for FPBEV applications. seems very likely that full exploitation of presently known and yet to be discovered advances in materials, chemistry and manufacturing techniques will result in Li-Ion battery technologies that combine substantially higher performance with longer life and yet more robust safety at lower costs. In mass production, these costs should permit payback through fuel cost savings for PHEVs and HEVs but also for FPBEVs, especially if fuel costs continue at high levels and vehicle technologies keep advancing.

However, realization of the ultimate performance and cost potential of the Li Ion “family” of battery chemistries for ZEV and near (including partial) ZEV applications is likely to take another decade.

Potential ARB Impact. Given that there is growing technical and market momentum towards PHEVs, there still remains the question specific to ARB as to how to categorize a PHEV for the ZEV program. The category selected makes a difference in the credits a manufacturer receives toward meeting the overall target specified by ARB.

Following the changes of 1998 and 2001, there are three categories of vehicles in the ZEV program:

  • Zero-Emission Vehicles (ZEV). Zero tailpipe emissions: battery electric vehicles, and hydrogen fuel cells.

  • Advanced Technology Partial Zero Emission Vehicles. (AT PZEV). These are vehicles certified to PZEV standards and employing ZEV-enabling technologies: e.g. hybrids or compressed natural gas vehicles.

  • Partial Zero Emission Vehicle (PZEV). Conventional vehicles certified to the most stringent tailpipe emission standards, zero evaporative emissions, and extended warranty.

ARB staff is recommending against allowing PHEVs in the pure ZEV category, preferring to place them in the AT PZEV group.

This recommendation is based on the original concern that PHEVs are not zero emission. Additionally, uncertainty exists regarding how PHEVs will be used (will they be plugged in consistently and throughout their life? Will all electric range be maximized under a wide variety of driving cycles? etc.).

...PHEVs being discussed today have more of a blended approach to using the battery pack. Like a conventional hybrid, the battery is used off and on throughout the driving cycle to assist the engine or drive in an all electric mode. Staff needs to learn more about how these blended PHEV strategies would be implemented and how they might impact air quality before recommending how they be treated in the ZEV regulation. For these reasons, staff does not recommend opening up the pure ZEV category as an incentive to bring PHEVs to market.

...however, that there are good reasons why manufacturers will produce PHEVs and there are adjustments to the regulation that could be explored that would facilitate this.


April 23, 2007 in Plug-ins, Policy | Permalink | Comments (18) | TrackBack (0)


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How were they, or any auto company, going to actually guarantee that 10% of their auto sales would be ZEVs? You can't force consumers to buy what you make. That kind of government mandate completely ignores the way the market works.

After having also read about this on EV world, I don't think "bullish" is an appropriate part of the title of this article. I don't think they give much hope for reasonably priced batteries of any type in the near term, if ever.

Here's something I have been thinking about, however. Boost the size of the motor on HEVs and increase the capacity of the battery as the price of the battery comes down. At some point and I am not sure what that point should be, add the plug-in future so that the battery would be topped up at the end of the day. This way, we can have continuous improvement without waiting for that magic day when we figure out how to bring the costs of batteries significantly down from the stratosphere.

In essence, this may very well be the Toyota strategy with the Prius and perhaps with their other offerings. Expect the next Prius to have both a more powerful motor and a larger battery with no increase in price. We don't have to wait for the magic bullet and can have meaningful progress now.

To reiterate, maybe a plug in makes sense even if you can only go about 5 miles or so in electric mode. I take it that it is not the ability to plug in that is expensive, but the batteries. Further, maybe there is too much emphasis on the electric only mode when the system is optimized with the blended approach.

From my point of view batteries are getting cheaper. Not because the price seams to be coming down, but because the batteries are progressively better and better. A 1500 cycle battery for the same price as a 300 cycle battery is a lot cheaper in the long run.

Curious that all these battery skeptics do not mention A123's product line or AltairNano. If the NanoSafe does what it claims - any large manufacturer US, Japan, China, EU could be tooling up for volume production right now. And you gotto wonder where is Delco, Union Carbide, Duracell, Panasonic, Sanyo etc. etc. etc. - disabling battery makers appears to disable the development process. Purpose?

How were they, or any auto company, going to actually guarantee that...

In exactly the same way that every auto company somehow manages to meet the CAFE number, 27.4mpg.


Exactly the same way? Really? That mileage figure is a fleet average, and all of those vehicles use ICEs. A BEV has a completely different drivetrain. This makes them a very different product, with their own set of shortcomings that are different from an ICE vehicle.

You're comparing apples to oranges. People do not view EVs the same way they do normal cars.

The fact remains that you cannot force anyone to buy them. GM or Toyota could spend billions on developing them, but if they flop in the marketplace, they won't reach that mandated ten percent figure.

And they don't view fuel efficient compacts in the same way they view inefficient SUVs/trucks. That being said, they still manage to meet CAFE standards, even if it requires purchasing cars from other manufacturers and rebranding them as their own. If there was a 10% ZEV mandate by law, they would use similar tactics to realize it, or not sell in the CA market.

That being said, the current administration was sympathetic to auto makers, and joined in the lawsuit against CA. In the end, CARB agreed to a comprehensive emissions portfolio that would result in better AQ than having 10% of all new vehicles sold be zero emissions.

It is a very good report to read through if interested about electric vehicles and especially batteries. Lot of good research put into them. However, I think they make quite unfair conclusions regarding to full battery EVs from their own findings.

Their comment on FBEVs in the summary: "It is the Panel’s opinion that FPBEVs are not likely to become mass market ZEVs in the foreseeable future due to the high cost for the battery not being recoverable with fuel cost savings and limited customer acceptance due to range and recharge time issues.".

What they say about batteries in the report itself: "The Panel’s investigation of vehicle energy storage systems focused on batteries as the only viable energy storage option for zero and near-zero emission vehicles, at present and in the foreseeable future. The emphasis was on Li Ion technologies because of their rapid technical progress and excellent potential to meet the energy storage requirements for full (including fuel cell) hybrid, plug-in hybrid, and full performance battery electric vehicles."

When they make economic calculation of li-ion powered FBEVs, they calculate how much costs would be for mass produced present batteries and ignore the possibility for cost reductions due to advances in battery chemistry. Another important factor is that these vehicles should get benefit from being ZEVs, air pollution is real and costly externality.

The report also makes an important point that there is not that much effort put into high energy li-ion batteries, which would be important for FBEVs. They have interviewed most important li-ium battery manufacturer's and it is very interesting to read about the differences between their technologies.

The first graph shown in this web page shows fuel cell vehicles as more likely to be in mass market before FBEVs. That is hard to believe when reading the report, which like so many other reports that are comprehensive on fuel cells (APS, National Academy of Science), has a long list of difficult challenges to solve before fuel cell vehicles can possibly make it, while batteries are technologically ready (too costly though). Although it is meaningful that major car manufacturers are putting much more effort to fuel cells than in batteries.

It strikes me that the range and refuelling times are hold to be an achilles heel of BEVs in the report. I would argue against this assumption. So many households have two cars and it is quite easy to rent one for occasional longer trips. With future ranges of FBEVs above 200 miles, I just don't see how the range would be a big problem when overwhelming majority of day trips is below 100 miles for 95% of people. Furthermore, the performance and ease of use of BEVs will add appeal to them and might be important factor when overcoming the initial investement in high cost batteries.

I can't believe auto makers are doing this. delaying the inevitable. ten years ago Toyota made the Rav 4 EV. and those cars are still running great today with over 100,000 miles on them. many gasoline cars made today don't even last that long without needing major work, so why not make EV's today. This is ridiculous. for now, I'm driving my Prius Hybrid by Toyota, and looking to add solar panels and a Plug-in option. The cars should be sold this way from the factory, this is ludicrous.

you can buy a FPBEV now here in italy , four doors , space for five
plus luggage , 80 miles autom , max speed 70 mph , all the options
pwr steering , pwr windows , cd player , etc , recharges to 50% capacity
within 45 mins , all for around 26000 dollars !
What are you all waiting for !

There's a lot wrong with the graphs they've presented.

PHEVs were being used on public roads here in Europe years ago (Audi Duo, Renault Electroad). Also the energy density of good 18650 LiIon is above 220 Wh/kg, not petering out at 180 as they suggest. And lithium-sulphur (although it has other problems) already exceeds 400 Wh/kg, yet they say they looked at this chemistry.

One wonders who they employ to do these "studies"?

Lithium batteries energy density potential seems to be underestimated at 160 to 185 Wh/Kg. The Electrovaya phosphate Series had already reached 225 Wh/Kg and their new lithiated manganese MN-Series are rated at 330 Wh/Kg and 650 Wh/L.

NB: The ARB graph must refer to specific types of Li-Ion such as A123 and Altairnano with quick charge capabilities but low energy density.

The Electroya Maya-100 BEV has about 220 miles autonomy with the earlier battery version and about 300+ miles with the new MN-Series.

The major limitations seem to be the long 5-hr charging time and the current high price.

jk wrote: "the range and refuelling times are held to be an achilles heel of BEVs in the report. I would argue against this assumption."

I think you're absolutely right, jk. There are a lot of two- and three-car households, and lots of cars that NEVER get driven more than 75 miles per day. Batteries have greatly improved since the days of the EV1. If an automaker puts out the right combination of features, range, and cost for a BEV, IMO there's a market.

For example something like the 5-passenger Prius II with a 100 mile range for under $35,000. That's a lot of money for a small car, so it has to use "Prius marketing." By that I mean it has to be immediately recognizable as an EV, not a converted vehicle (the EV1 also achieved that). It has to be made by a major car company, with a reasonable warranty, and it has to be sold, not leased.

I don't know if $35k is a realistic cost for 100-mile range, but it certainly sounds doable. To assume you have to go 300+ miles and refuel in 5 minutes is ludicrous. I certainly don't need that.


According to EV world, there will be a $30,000 Chinese built, full performance EV on the U.S. market about the size of a corolla within 18 months.

Do you have a link for that?
Not that I'm excited to buy a Chinese car, but if the other car makers won't make one, I will buy that car wether its made by my neighbor or by Osama himself (that's hyperbole folks).

I'm am SICK of waiting for someone to make a useable EV.

Though I'd prefer to pay less than 30K and have a small range (like 50 miles). Since that's ALL I NEED! I have a Prius if I need to go further. I'm so tired of this supposed need to go 300 miles on a charge and recharge in 5 minutes crap.

It's Miles Automotive(the 30K EV) and I saw one of their LSVs last Friday, Its a real car! not cheap and flimsy like some others.
I'm very intrested.

I'm ready to buy series hybrid technology like the GM Volt first release that presented 40 miles electric with an ICE for range extension, or as I like to look at it as a backup system. I DONT want a fuel cell car, they will just muck-it-up so that the consumer will have to use hydrogen to get the car to move, battery or not.

The auto manufacturers need pressure from law makers. Car companies don't want to put out low maintenance cars. What will their service departments do? Where will the money come from for their accountants to count?

They all know electics can be done now. They did it already in California!! GM even got rid of the evidence (EV1).

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