Under pressure to cut fuel use? Try a hydraulic hybrid

Written by adam


Those of you who weren’t impressed by the air-powered car might be more excited by the latest pressure-powered vehicle: the hydraulic hybrid truck.

Hydraulic hybrids pair a standard internal combustion engine with a series of tanks holding compressed fluid. The tanks capture energy during braking and deliver it back to the wheels during acceleration. A pressurized tank can’t hold a large amount of energy, but it does offer some compensating advantages:

> One is that it can accept and deliver huge amounts of energy quickly, which batteries cannot. And its storage ability does not degrade over time, which is a fact of life with batteries available today.

It’s the ability to deliver large amounts of energy quickly that make the system so desirable for trucks, which need considerable starting power. Another advantage: components are relatively cheap and incredibly easy to service. In fact, systems can be built with no electronics at all.

UPS just concluded a road test, conducted jointly with the EPA that demonstrated fuel efficiency gain of 50%. The company will add seven of the trucks to its fleet over the next few years:

> Fuel economy is increased in three ways: vehicle braking energy is recovered that normally is wasted; the engine is operated more efficiently, and the engine can be shut off when stopped or decelerating.

> The EPA estimates that when manufactured in high volume, the added costs of the hybrid components can be recouped in less than three years through lower fuel and brake maintenance costs.

The initial purchase represents a tiny fraction of UPS’ 93,600-vehicle fleet, but the quick payback period and lack of any need for exotic fueling infrastructure suggest the technology could be rolled out quickly if it proves a success.

The technology works well in any situation in which trucks have to start and stop frequently. One of the most promising applications? Garbage trucks.

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  1. Brandon

    Garbage trucks using hydraulic hybrid systems, as well as burning LFG (land fill gas, basically natural gas) would be a great piece of the energy puzzle.

  2. Donny

    There are many ways to store energy, and I’m glad folks are looking at alternatives that are cheap and applicable to particular niches.
    The reason a hybrid system works is because it stores energy and returns it to the car when needed, not because of something specific about batteries or electricity.
    Flywheels have also been investigated for this type of energy storage, and also supercapacitors.
    Keep thinking outside the box, folks, and way to go UPS!

  3. Alex

    I love this new spin on hybrids for the simplicity and durability of the hydraulic system. Like Donny said, keep thinking outside the box. Striving to be more efficient in lots of little ways seems to work better than trying to find a one-size fits all solution.

  4. Cherie

    Thrilled to see all additional attempts by trucking companiesmaking an effortto utilize technology to increase efficiency and reduce waste. I work in a very large gated community(20K residents) and UPS has set up storage lockers. They fill it full of packages and then use a golf cart to deliver around the community instead of using the full size trucks to deliver from door to door. Kudos to UPS.

  5. shritz

    So, at the risk of having my comment deleted, I don’t get it! If UPS could improve fuel efficiency by 50% and there is a three year payback, why are they only adding seven units over the next several YEARS?!?! Seems to me that they could retro-fit all 93,000 of their trucks at their next routine maintenance and laugh all the way to the bank, not to mention getting a huge “WAY TO GO!” from Terrapass.

  6. Adam Stein

    Because it’s a new technology. They’ve been testing it under controlled conditions, and the next phase of the test is to put several of the trucks into full-time use to see how they perform. Fuel efficiency isn’t the only consideration. The technology has to work reliably, etc.
    But if all goes well, I imagine it will get rolled out more widely relatively quickly.

  7. JD Howell

    Adam, can you comment on the company that has developed this system for UPS, or at least more information on the technology ? This, combined with many of the CO2 scrubbing technologies being developed (and patented) for removal of CO2 from the air and from air paths (i.e, tailpipe) would greatly benefit air quality. And at the same time, it seems the companies implementing these technologies would benefit from several tax incentives provided by the stimulus package. After all, it is GHG we’re seeking to minimize and eventually, remove.
    I’d also like to see UPS and the trucking industry in general take an approach with solar. All of these vehicles have a large roof space and the addition of thin film products could at minimum offset the charging requirements for auxiliary equipment, air conditioning, and potentially even an electric hybrid operating system coupled to the flywheel of the vehicle. I can see this as a fairly simple solution as well, that wouldn’t require a large retrofit… call it an electric boost motor, if you like !
    Also, will you guys please do an article on Global Dimming ? Haven’t seen enough information circulating on this topic and it seems there’s more to be said and not enough informed global citizens aware of this aspect of pollution. Thanks !
    As for me and mine, we’ll see you out there, on our bikes of course – JD Howell, Eugene, OR

  8. Adam Stein

    Alls I know is what’s in the article:
    “When fully charged, the system holds 2,000 horsepower-seconds of energy, according to Benjamin M. Hoxie, engineering manager for hydraulic hybrids at Eaton, an automotive supplier that built the prototype, using technology developed by the E.P.A.”
    Apparently the E.P.A. actually has some patents on this stuff, which is interesting. I didn’t know they were in the technology development business.

  9. vm

    I think recent decision by UPS to stop railroad shipping in favor of huge gas guzzling tractor trailers was a shame.