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Crossing Diesels with Plug-In Hybrids: Good or Bad Idea?

Volvo V70_PHEV_dieselDiesels and hybrid-electric cars have often been posed as competitors racing to capture the green-automotive market. Diesels are more popular in Europe, while hybrids are more popular in the United States. Both have their advantages and disadvantages: diesels can get impressive fuel economy without complicated drivetrains (providing a cost advantage over hybrids today), while plug-in hybrids bundled with a renewable energy-powered grid can be even cleaner.

But now, it looks like these competitors are coming together. Volvo Car Corp. announced Friday that it plans to bring a diesel plug-in hybrid to the market by 2012. The news comes after Peugeot earlier this month unveiled a diesel PHEV minicar that it plans to bring to the market next year, and BMW also showed off a sporty diesel PHEV concept car at the Frankfurt auto show. While companies have been tinkering with the concept for some time, it looks like diesel PHEVs are finally starting to gain some traction.

It’s an exciting idea. First of all, diesel fuel packs 10-20 percent more energy per gallon than gasoline, according to Fusel, a site that advocates running diesel engines on vegetable oil. That higher energy content, combined with some engine advantages, means modern diesel cars can get about 40 percent more miles per gallon than their gasoline counterparts, according to the site.

With that kind of diesel fuel economy, it means the new crop of clean diesels, such as the Volkswagen Jetta TDI, achieves similar fuel economy to hybrids like the Toyota Prius without a complex drivetrain, according to AutoblogGreen. On top of that, advocates say diesels are more fun to drive, because they deliver more torque. Perhaps the most important factor to consumers: diesels often cost less than hybrids. According to an Edmunds comparison earlier this year, the 2009 Jetta TDI cost $22,890, compared with $28,933 for the Prius. And plug-in hybrids are expected to cost even more.

But diesels also emit more particulates than gasoline, and while new technologies have enabled companies to meet strict U.S. standards for particulates, those technologies cost money. Diesels also have an image problem. In the United States, many people still think of diesel as the “loud, smoke-belching beast” they remember from the 1970s, as this article puts it, even though they have changed dramatically.

A marriage of diesel and plug-in hybrid technology could produce a wonder child that brings out the best of both technologies, boosting fuel economies to their highest levels yet while avoiding the range issues of pure electric vehicles. An electric motor could help diesels easily meet even the strictest potential particulate standards being considered today, while a diesel engine could boost the fuel economy of a PHEV.

But some think that the match could also produce a monster. Adding the technologies together could result in an even more complex drivetrain that ends up being far more expensive than its worth. And it could still have trouble winning diesel converts in the United States. We’ll be waiting with our fingers crossed to see what automakers produce. What do you think?

6 Responses to “Crossing Diesels with Plug-In Hybrids: Good or Bad Idea?”

  1. There are two things. Diesel vs gas pros aren’t as clear cut as you make them out to be. The emissions are a real problem, plus the added energy to use diesel instead of gasoline makes it a questionable move for most environmentalists. Add in the higher cost of diesel (for now), plus the much higher initial cost to purchase a diesel and you end up with a lot of cons.

    Mating a diesel to an electric motor makes sense in that you’re increasing your fuel efficiency, but by how much, really? Yes, you might go from 50 mpg to 60 mpg in a Prius, but is that really worth the several thousand more?

    When you talk about plug-ins however, the added cost is smaller proportionately to the overall cost. (What’s a couple thousand more to a car that’s going to cost over 40 grand, right?)

    • Wrong – lots of places.

      At the refinery, the cost of producing diesel is less than gasoline.

      The only reasons for higher cost, state-by-state, is taxes.

      Look at today’s clean diesel and emissions are NOT a significant problem. And the happiest diesel drivers in my extended family are those who have convenient access to biodiesel.

      The critters not only run cleaner and cheaper, they have more power.

      • True, the financial cost is less to produce, but the amount needed to create is more. The financial aspect is not one to be ignored, though. I don’t see any politicians running to cut the tax structure right now.

        The emissions for diesels is a problem, because the cost to putting in the clean filters is high, not to mention the replacement costs.

        Biodiesel makes a lot of things better, but even there the case is not clear cut. I happen to fall on your side of things there, although the availability is a big issue for most.

        They do have more power.

  2. waltinseattle

    Mr Wallace has touch most of my points. I would only now address the ownership of batteries as perhaps a separate proposition from ownership of the vehicle they are used in. A system of leasing them, charged, from a station much as we pick up propane , acetylene and other gases in special canisters which belong to the station, not the customer. This insures expert maineneance care and allows best alocation of monies ( like saving the car buyer from the tremendous burden that is yet, and for the forseeable future, high enough to turn many off on the idea of going electric. A lease system will spread the burden.

    I for the life of me cant understand why so many hybrids sem determined to hold on outmoded power trains!!!

  3. Bob Wallace

    Use the diesel to drive a generator. Make it a genset. Like the Volt.

    That way the diesel can run at a fixed RPM, can be optimized for a fixed RPM. That should be even less polluting. (And remember, we have had low sulfur diesel in the US for only a short time. That’s where some of the opposition to diesels comes from.)

    Power the wheels with electricity. Electric motors have enormous torque. (Look at what the Tesla can do on a quarter mile track.)

    Use in hub motors. That makes for easier regenerative braking. It eliminates the weight of the drive train and it increases efficiency by about 10%.

    Design the battery space large enough to hold a 25kWh pack (or whatever the standard EV pack turns out to be). Design the car to allow battery swaps. When the price of batteries comes down the car could be reborn as a “100 mile range” plug in, with extended range from the genset if needed.

  4. Darb Dabney

    Seems to me that most locomotive engines are diesel-electric hybrids in some sense (although not of the plug-in variety).
    Getting that sort of power train into a small, lightweight package seems attractive, if it doesn’t end up costing more than either hybird or diesel vehicles.