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California’s AQMD to Acquire and to Test Plug-in Prius

The Southern California Air Quality Management District (AQMD) has decided to acquire and to test an Energy CS plug-in Prius (earlier post) in addition to the fleet of 35 Priuses it is converting to hydrogen-fueled combustion engine-hybrid drives (earlier post).

This plug-in project complements another plug-in hybrid (PHEV) initiative by AQMD in testing five PHEV commercial vans (the DaimlerChrysler Sprinter).

The decision came during the AQMD board meeting in May; the district is now awaiting production and delivery of the vehicle.

The rationale for the project mirrors larger discussions in the sustainable transportation marketplace about hydrogen and nearer-term steps.

A more near-term solution [than hydrogen] is to rely on well-developed, lower-cost technology, specifically lithium-ion batteries and hybrid electric drive technology.

This battery-dominant strategy increases battery capacity and electric motor utilization to provide true zero-emission miles, which increases vehicle range, reduces fuel consumption, and decreases the role of the engine or fuel cell. When used in ICE vehicles, the battery-dominant strategy also decreases tailpipe emissions.

Because the battery packs must be grid-recharged to fully utilize the electric motor and zero-emission range capability, these vehicles are called plug-in hybrid electric vehicles (PHEVs).

AQMD Plug-in Prius Costs (not including the car)
PartnersCost sharePercentage
* plus in-kind cost of vehicle
(in-kind development)
(funding & in-kind development)
(funding & in-kind demonstration)
(in-kind performance testing)
Santa Monica
(in-kind demonstration)
Valence Batteries
(funding & in-kind development)
(in-kind emissions testing)
AQMD requested*$130,00025%

Overall costs for the project—which will ultimately result in the deployment of four plug-in hybrids for testing—are estimated to be some $539,000, borne by AQMD, EnergyCS, CalCars, Clean-Tech, Southern California Edison, Valence Batteries, the City of Santa Monica, and CARB.

The basics of the project are as follows:

  • EnergyCS will engineer, design, and optimize of the PHEV replacement system, using a Valence Saphion lithium-ion battery pack (with approximately 9 kWh of energy storage) to replace the OEM NiMH battery.

  • Once the system has been designed and tested, the demonstration phase will consist of installing the system on test vehicles to further optimize the system and ensure the emissions are maintained at SULEV levels.

    These vehicles will be demonstrated by CalCars, the City of Santa Monica, EVO Transportation Corp., and the AQMD, with each entity providing a vehicle as in-kind cost-share. The entire project is anticipated to conclude within one year of initiation.

  • Clean-Tech, a transportation integrator, will assist in the design migration from demonstration to commercialization, with a focus on eventual sale as a conversion system. (Clean-Tech and EnergyCS have created EDrive, a joint venture to commercialize the plug-in technology. Earlier post.)

  • The technical goals of the project include optimization of battery performance and life, maintenance and expansion of the EV mode, double the fuel economy of the conventional HEV, and seamless driver experience from a standard Toyota Prius.

AQMD’s staff recommendation was enthusiastic about the potential:

Successful completion of this project will result in growing recognition of the business value of PHEVs and increase consumer demand for PHEVs. This project also has the potential for wide application if commercialized due to the popularity of the Toyota Prius vehicle.

Increasing zero emissions miles [i.e., miles under electric drive] and doubling the fuel economy of the current Prius population would have dramatic effects on air quality, greenhouse gas emissions, energy diversity, and technology advancement.

Furthermore, the conversion system may also have application to other Toyota hybrid vehicles, namely the Ford Escape HEV which uses the Toyota technology, as well as the hydrogen hybrid conversions authorized by the Governing Board in March 2004 as part of the “Five Cities” hydrogen ICE project.

(A hat-tip to Jack Rosebro!)




it would be nice if they dedicated one prius to a natural gas, hybrid, conversion - and then compare well-to-wheels efficiency (and polution) for natural gas, and hydrogen derived from natural gas.


i remembered this old table of projections:

discussed here:

basically it looks like the well-to-wheels efficiency of natural gas hybrids run around 16%, significantly above H2 ICE efficiencies.


The hydrogen Prius reminds me of the statement that a camel is a horse designed by a committee. It seems intended to bolster the DoE line that hydrogen looks like a winner. If that theory is true it's a case of 'we'll pay for the hot dog and only charge you for the mustard'. For now that is.


Regarding the earlier comments, a few comments: (1) the hydrogen Prius is not a DoE project, but a California state government feasibility study project, and (2) a major design problem with natural gas-fueled vehicles is that the fuel cylinders take up a lot of room, while a major design problem facing hybrids is...the battery pack and electronics take up a lot of room.

A natural gas-fueled hybrid, while a nice dream, would be hard to design with any usable cargo space, and passenger cars without cargo space do not sell. That's why we've not seen many NGV hybrids.

A natural gas hybrid city bus, however - tanks on the roof - might be worth a try.


is hydrogen actually easier to store than natural gas?


If we are lucky batteries will improve enough to make the entire issue mute... but we cant count on it and with global warming and climate change id rather not count on a bajillion square miles of plantlife providing my fuel. In the shotrun im sure lot of fuels will run rampant.. same as happened the last time they were groping for a fuel to power cars.... and again its gona be fun finding out what happens next. Odd isnt it that both times it was at the end of an era and the start of a whole new much odder one?

Ron Fischer

Hydrogen is much harder to store than natural gas. The H2 molecule is smaller, seeps through and into materials and weakens welds in high strength steels (google: hydrogen embrittlement). The gas is very low density, takes more energy to compress. Analyses of converting natural gas pipelines to hydrogen are not promising (20% higher energy loss H2 vs CNG pipeline).


that's what i figured. i guess my question was to get jack thinking along those lines ... and there are certainly a few natural gas cars, for example the honda civic gx, that show it can be done at a low price point.


Good point about climate change affecting biofuel reliability as I see signs of problems locally. However isn't natural gas going to peak 10 years after oil? That's within the life of a car built today. The cost-benefit calculation for the pressure tank and system needs to factor this in. It might be a case of going for the least problematical option.


Good point about climate change affecting biofuel reliability as I see signs of problems locally. However isn't natural gas going to peak 10 years after oil? That's within the life of a car built today. The cost-benefit calculation for the pressure tank and system needs to factor this in. It might be a case of going for the least problematical option.


Aussie, you just put your finger on the reason why I think the plug-in hybrid is the key to future-proof transportation.  The main thing it needs is a battery pack which can be upgraded after manufacture; the source of its electrical energy, the grid, is updated continuously and the car implicitly updates "its systems" along with it.

Jim White

The problem I see with using the Prius as a PHEV is its relatively small electric motor. My understanding is that the electric motor is not large enough to power the car to highway speeds.


My understanding is that the limitation is on RPM of the motor/generator between the engine and differential, but I could be wrong.  Regardless, the Prius+ can still derive economy benefits from electricity even at speeds where it has to run the engine.


aussie, i think the important thing is to burn that natual gas where it is most efficeint (maybe in busses and trucks more than cars) as it gets more expensinve and scarce, rather than reform it into even more expensive hydrogen.

but, the "hydrogen economy" has a big lobby these days, and as they are having trouble with fuel cells, they're falling back to "internal combustion hydrogen" as a stopgap.


It isn't that hard to generate methane(primary component of natural gas) from biomass. There are already tens of thousands of biogas digesters in India. Biogas digesters were widely used to treat sewage in pre 1950 American cities. Widespread use of antibiotics killed the methanogenic bacteria so other treatment techniques are now used. If poor villages in India can invest in digesters why don't rich American beef, pork, and poultry producers?


Odograph wrote: "is hydrogen actually easier to store than natural gas?...i guess my question was to get jack thinking along those lines...and there are certainly a few natural gas cars, for example the honda civic gx, that show it can be done at a low price point." (sic)

Please take the time to read posts carefully before replying. I did not compare NGV to H2, nor did I endorse (or disparage) the Prius H2 ICE project. Actually, I didn't get around to any opinions at all. I merely pointed out that (1) the Prius project is not a federal project, as someone else had thought, and (2) one of the reasons why natural gas hybrids are, at present, few and far between.

It sounds like Odograph is bullish on NGVs (great!) but oversensitive to anyone who he or she percieves to have different views. That's dangerous. We have to be able to look at both the positive and the negative of any solution. Some of my clients are municipal fleets with electric, hybrid, NGV, biodiesel, and hydrogen transportation, among others. They are the test beds for many of the alternative fuels that we discuss.

I have seen too many leaks created during the filling process to be comfortable with NGV. Most of them involved driver error and the Honda Civic GX, and an NGV leak releases a lot of hydrocarbons into the air, especially if the driver doesn't notice it and operates the car. Happens way too much for my comfort.

By the way, the Honda Civic GX doesn't necessarily "show that [NGV] can be done at a low price point." I think it can, but we don't know whether or not Honda is making money on these vehicles. Civic GX production is low enough that Honda can afford to lose money on them and keep them around to help Honda's image and further their research. Don't forget that there were at least two money-losing cars on sale in the US in 2000 - the Honda Insight and the Toyota Prius.

Until operator error can be dramatically reduced, I'm a bit leery of all gaseous fuels - NGV, propane, hydrogen, anything - and believe me, I want to get rid of gasoline as much as the next guy. Practical problems often foil pie-in-the-sky solutions. Unless we face and solve those problems, it's all just talk.


Most everyone can handle an extension cord without creating a hazard.  How do you feel about plug-in hybrids, Jack?


Although Engineer-Poet's post is somewhat vague, I think he or she has somehow concluded that I am worried about the safety hazards inherent in NGV vehicles, and from that, has further concluded that I think extension cords are dangerous. So it's time to drag out the sarcasm, and then run away. Oh, dear.

Again, please read the post all the way through before replying! I did not address NGV gas leaks as a safety issue; rather, I brought up the amount of hydrocarbons released into the air during NGV leaks. I'm referring to emissions. And I'm not talking theory, but practical experience. You may be surprised to learn than an NGV vehicle with a serious and very audible leak can be driven for a while before running out of natural gas. All too often, a municipal employee will drive up to the city or county's fleet maintenance yard, and ask a technician, "what's that whooshing sound?" And yes, NGV drivers are trained on these vehicles; and yes, this has happened more than once with the same driver. Since I brought this up in the context of emissions, and not safety, I'll expect Engineer-Poet to opine as to whether or not the above situation represents a safety problem...

In answer to your query about hybrids (and I'm assuming that you really wanted an answer): As with all emerging technologies, I think that the plug-in concept is very promising. But assuming that someone with NGV refueling concerns is therefore scared of an extension cord? That's junk logic. My own experience in the field suggests that the average person - even after NGV training - can still make enough of a mistake to cause a problem. Your mileage may vary.

Please remember that this all started because (a) I corrected someone who thought that the AQMD H2 hybrid project was a federal project, and (b) I explained the design problem that has limited NGV hybrid research as compared to gas-electric hybrid research. These statements were somehow interpreted as anti-NGV, pro H2. I have not attacked or defended any one technology. All new technologies come with problems. You can pretend that they are not there, but someone will have to do the dirty work and solve these problems. Step up!

It sounds like Odograph and Engineer-Poet are pro-NGV. Great! If you have real-world NGV field experiences of your own, particularly any which contradict what I have written (rather than what you think I meant), PLEASE send them along. I am open to as much information as I can get, especially decent field research. And if you want to see a natural-gas hybrid, build one!


I'm leaning anti-NGV at this time.  If natural gas supplies were increasing it would be otherwise, but N. American production has already peaked and the government is now pushing LNG imports to make up the difference.

NGV's would just substitute one imported fuel for another.  I don't want to rearrange deck chairs on the Titanic, I want to build a new ship.


On LNG: Most LNG investors want to amortize their terminal plants over a 20yr period and beyond. Well, the US has missed the boat. Much of the world's exportable Natural Gas is under long term 30 yr contracts.

We'll have to struggle just to keep the nation's pilot lights from going out due to shortages and the resulting pressure drops. I shudder to contemplate the number of manual restart and defective electrical restart pilot lights there are in the country.

Now, let's add a new demand on the above system - NGVs.

Rob Sawyer

---- and the results of this feasibility study are ... (crickets)

Whether you power a prius with natural gas, biodiesel, hydrogen, or gasoline, is plugging it into the grid a good idea? You are betting that the utility company with it's power lines are more efficient overall than the prius. Granted there is the argument that the utility company could be using green technology in which case it does make ecological sense.

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