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Gas-Optional & Green

The bright green community of the future may be eminently walk-able and replete with useful public transit, but in the meantime, strong demand remains for personal mobility (i.e., cars). Although two broad technology categories are facing off for the title of Car of Tomorrow -- electric batteries and hydrogen fuel cells -- a somewhat more humble development is sneaking in as the near-term technology of choice: gas-optional hybrids.

We've posted about gas-optional hybrids before, generally under their previous label "plug-in hybrids." Unlike current hybrids, gas-optional hybrids would add the ability to plug them in when parked, drawing power from the grid. Gas-optional hybrids have much larger batteries than current hybrids, and can go quite a ways on electric power, only switching over to the gas engine if the batteries are drained or when going onto the highway. They have a far better range than electric cars, get better mileage than traditional hybrids, and are far cleaner than old-style gasoline-only cars. What's more, gas-optional hybrids can also serve as "mobile generators," putting power back in to the grid if the batteries are full when plugged in. Best of all, gas-optional hybrids are possible now, and some people are even retrofitting Priuses to gas-optional function.

The obvious question that arises is whether a gas-optional hybrid, recharging from the grid when parked at home, is really better than a standard hybrid when it comes to greenhouse gas emissions. After all, electricity generation using coal or natural gas puts out CO2. How does the power drawn from the grid compare to a comparable amount of gasoline used by a regular hybrid?

Joseph Romm, author of They Hype About Hydrogen and former director of the Office of Energy Efficiency and Renewable Energy at the US Department of Energy, has become quite the gas-optional hybrid evangelist. In an email to Felix Kramer, founder of the California Cars Initiative (and reposted to the CalCars mailing list), Romm answers this question, making a very good case for a rapid shift to gas-optional designs.

Let's compare 12,000 miles (the typical yearly vehicle miles traveled), running all electric, which consumes 3,000 kwh, with running all gasoline (i.e. using a regular Prius), which would be 240 gallons.

The lifecycle greenhouse gas emissions from burning a gallon of gasoline is roughly 25 pounds (20 on-site, another 5 in the petroleum production chain -- the number may be slightly higher for reformulated gasoline, and will be considerably higher from oil from the tar sands). So we have 6,000 pounds of CO2 from a Prius.

NOTE: The average new NON-hybridized car would emit 11,000 to 12,000 pounds of CO2. This is the proper baseline for those who are concerned about whether e-hybrids would increase emissions compared to a business as usual case.

The grid average emissions factor for electricity in this country is, roughly, 1.3 pounds per kwh. That yields 3,900 pounds of CO2! So running your E-hybrid on the U.S. grid is 35% better than running a Prius on gasoline and 65% better than an average car.

If the entire grid were coal, you could double that (7,800 pounds), so even in that worst-case scenario, you'd still have far LOWER CO2 emissions from a plug-in Prius than from the average new car on the road running on gasoline.

In California, with its cleaner grid, you'd have under 2,000 pounds emissions from a plug-in Prius. And, of course, people can choose to purchase 100% renewable power.

And as the grid gets cleaner, with more wind, solar, wave and tidal power coming online, the relative advantage of gas-optional hybrids grows.

Current hybrids run $2,000-$5,000 more than comparable conventional autos; the larger batteries of gas-optional hybrids would add more to the cost. But according to the Center for Energy and Climate Solutions, in a June 2004 report to the bipartisan National Commission on Energy Policy, the ability of gas-optional hybrids to feed power back to the grid can actually make them lower in overall cost.

The vehicle will almost certainly have a higher first cost, but this is likely to be more than compensated by the economic benefit of a lower fuel bill [as well as] a large potential revenue stream the vehicle owner may be able to extract from the utility by having what is essentially a portable electric generator.

The largest potential revenue stream that a PHEV owner might be able to extract is for so-called spinning reserves, which, as one analysis explains, “are contracts for generating capacity that is up and running, and is synchronized with the power line.” When called upon, a spinning reserve “must ramp up to its full output within 10 minutes.” Spinning reserves are valuable to a utility or power system because they contribute “to grid stability helping to arrest the decay of system frequency when there is a sudden loss of another resource on the system.” Value can also be extracted by generators that can provide faster response when grid voltage needs to be increased or decreased, so-called “regulation services.” Since cars are designed to start rapidly, they could quickly add their power to the electric grid when needed. Utilities would pay for this service if there was a guarantee that the car could deliver juice when needed, which suggests that this is more practical for vehicle fleets or for a corporate sponsor.

The potential value of such services is significant: $700 to $3000 per year. This value is so large that it might allow the monthly cost of purchasing or leasing a PHEV to be lower than a conventional car[.]

Unsurprisingly, automakers are not yet ready to provide gas-optional hybrids from the factory. Business Week reported recently that, although Toyota and Daimler-Chrylser (among others) may be interested in pursuing gas-optional hybrids down the road, they were hesitant to bring them out now. The added costs, uncertain demand and general industry timidity all contribute to that decision.

In the meantime, Prius owners can convert to gas-optional status with a bit of work (as can owners of the Lexus and Ford hybrids -- sadly the Honda models can't be converted). Interestingly, the compact SUV hybrids -- the Lexus and Ford hybrids, as well as the upcoming Toyota Highlander hybrid -- are better suited to gas-optional conversion than even the Prius. As the CalCars site puts it:

Compact SUV are good candidates: they're popular, they have more space for batteries, and several have already had all-electric versions.Unlike controversial larger SUVs, they're built on safer car frames, and their weight and bumper height are similar to sedans. Finally, the batteries' added mass will lower their center of gravity, reducing tendencies to roll over. That's why SUVs + CalCars=Green SUVs

It's possible that, a decade or two from now, hydrogen fuel cells and/or battery-electric cars will have the combination of power, range, convenience and cost to make them ideal replacements for internal combustion engine cars. Maybe. Then again, we may just find that plug-in hybrids (substituting biofuels for gasoline) have already given us an ideal alternative.


Listed below are links to weblogs that reference Gas-Optional & Green:

» Are Gas-Optional Hybrids the Way... from sustainablog
While our fearless leaders in Washington have put our money behind hydrogen fuel cell technology that is likely decades away from commercial viability as a replacement for the internal combustion engine, WorldChanging points us to another option for ... [Read More]

» New Energy Currents: 06-17-2005 from Winds of Change.NET
This week, debate in the Senate began in earnest on the federal energy bill - and the debate in the US, around the world, and on the internet shows no signs of aba... [Read More]

» New Energy Currents: 06-17-2005 from Winds of Change.NET
This week, debate in the Senate began in earnest on the federal energy bill - and the debate in the US, around the world, and on the internet shows no signs of aba... [Read More]

Comments (14)

Great summary of the situation. I would clarify a few things:

* The conversions are not trivial; they are definitely not do-it-yourself projects, involving hard-to-get components and high voltages. For more on what's involved, see the PRIUS+ Fact Sheet at calcars.org

* CalCars' goal is entirely to promote the technology in order to further motivate auto makers to build these cars. In that context, we're delighted that EDrive Systems will build a business on conversions of Priuses. For more on the relationship between the two efforts, see Message 36 in our CalCars-News archive.

* CalCars is likely to focus next on the Ford Escape compact SUV, rather than on Toyota or Lexus SUVs. For more on reasons and current status, see the Yahoo Discussion Group linked from the CalCars website.

* Revenues from "spining reserves" (sometimes called V2G or vehicle to grid) can't happen until we have a modernized grid, hundreds of thousands of GO-HEVs with advanced telematics that enable them to identify themselves to the grid. It's a goal well worth working toward.

Felix Kramer, Founder, California Cars Initiative

Anyone interested in more information (down to some extremely technical information and results of actual trials) on these issues should visit the AC Propulsion White Papers page.

Disclaimer:  I have no affiliation whatsoever with AC Propulsion or EPRI.

Erik Ehlert:

I think that there are two things that make gas-optional better than hybrid. The first reason is that getting electricity from the grid allows you to concentrate the pollution source. That is, I think it would be easier to control pollution at one power plant than through the catalytic converters of thousands of cars.

The second, briefly touched on in this blog, is that gasoline has only one real source today (underground-derived oil) but electricity could be generated from A MULTITUDE of sources, including clean and renewable ones. My car sits in the corporate lot all day under the hot sun. Why not take the flexible solar cells they are producing today and make one that's designed to be unfolded, put on the car's top, and plugged into the car? Then the production of CO2 to drive the car goes to 0.


Cost is only an issue in our current one-car per person model. As has been posted on this site before, one of the best short-term alternatives for reducing car impact (as redesigning cities away from auto dependency will take time) is car-sharing. Either corporately (Flexcar, etc.) or personally (you and a friend), this takes a great deal of the sting out of higher costs for these vehicles, even putting them within reach of those who cannot afford conventional gasoline cars.


Combining a green power purchase with a gasoline optional car would seem to be a close to ideal solution, ignoring cost for the moment.

Ben Schiendelman:

Car-sharing, bus, train, moving into a place with better transit - all of these are much more viable options. The question is, how do we convince people to do it?

WA has come up with one way - raise gas taxes to pay for rail infrastructure upgrades while gas prices are high. It will drive some people out of their cars and help support demand for public transit (which I believe, eventually, will be the only option).


I'd like to see a whole package for this type of hybrid conversion....a combination of solar pv for the home, ec energy's conversion, and solar car ports at offices or public garages. In this way, the synergy created by this undertaking would provide a sustainable model and sound infrastructure.

Does anyone know if this is happening in California....Felix?

Ben, in principle, I agree -- vastly improved public transit and sustainability-focused urban planning would be preferable to further proliferation of cars, even GO-HEVs. But there's a chicken-egg dilemma -- in order to make moving from one's auto to public transit & walking, the public transit (etc.) infrastructure needs to be in place. If you're depending upon higher gas taxes to fund the improvements to infrastructure, you'll have a "viability gap" between the point when gas taxes go up and the point at which infrastructure improvements are complete (or complete enough to be useable). Rail, new bus lines, changes to road availability and sidewalks -- these don't pop up overnight; they can take years to implement. Meanwhile, people who are priced out of car use don't have a public transit alternative.

We know where we want to be. The real challenge is figuring out how to get there without making the people who can afford it least suffer the most.


“Where does Toyota stand on this? Talking to a representative, I learned that Toyota intends to introduce plug in hybrids when market demand and battery costs justify it.”


The problem with making life too unformforable for single driver cars and urban sprawl is if you do so alot of people worth a ton of tax dollars simply up and leave you to implode.

The very same people you hate soo much are the ones funding everything you care about through massive taxes.

Re Neal's question about a complete package, of course, that's the goal. We've had conversations with developers of new solar homes about bundling the price of a GO-HEV into the mortgage. If Bay Area Rapid Transit at some future time allowed charging in their parking lots, this would be of special interest to people who don't park their cars in garages. I hope once we have GO-HEVs on the roads, many things will start to change.

Ralph Lovesy, Campaign for Battery Electric Vehicles (UK):

I would be interested to hear of any studies that have compared the greenhouse gas emissions caused by comparable EVs, plug-in hybrids and standard hybrids for comparable drive cycles. I would be especially interested in studies from outside the US, but happy to read US studies in the absence of anything else.

The studies I have seen suggest in a State with a relatively "clean" low-coal electricity generation mix (such as California), EVs cause the fewest emissions, followed closely by plug-ins and that this may even be true for the US average mix.

Many thanks!

Tom Walsh:

G-O hybrids appear to be a great idea whose time has come - a step above current hybrids and more practical than all-electric, given current battery technology. I do have a concern, however, because I live in Minnesota. One thing that gasoline engines produce much more abundantly than electric motors is heat. One of the basic requirements for a vehicle in Minnesota in winter is efficient and quickly available heat for the car's interior. Can gas-optional vehicles provide that without sacrificing their "greenness"?

Paul Scott:

My family has the "whole package" mentioned in Neal's post. We have a 3kW PV system and a Toyota Rav4 EV. The solar covers all our driving energy needs and most of the house as well. Using solar PV to replace gas means the payback is very fast, i.e., affordable. Solar ports, combined with charging stations, are in use throughout the LA and SF areas. More could easily be built. It's a great combination.

Charging could also prove to be a profit center for both private and public entities as GO-HEVs and EVs become common. Cities could easily sell power through parking meters with a swipe of a card. Restaurants and shopping centers could do the same thing while their customers ate or shopped.

Those of us with experience driving an EV with a 100 mile range understand that this is not as much of an inconvenience as one would think. EVs built today could easily have a 150-250 mile range and could be charged from any plug anywhere. This could cover well over 90% of our daily needs.

A GO-HEV would be a great second car for those times when longer distances were traveled.

The only problem is battery cost, but that could be dealt with in the short term by taking some of the federal subsidy currently given to the oil industry and applying it to the cost of EVs to bring them down to affordable levels with ICE cars. It wouldn;t need to be very much per car. After the numbers increased, the economies of scale would come into play and bring the battery cost down to where the subsidy is no longer needed.


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