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NextEnergy Launches Hydraulic Hybrid Working Group

NextEnergy, Michigan’s non-profit alternative energy technology incubator, has formally launched a Hydraulic Hybrid Working Group.

A hydraulic hybrid system uses an accumulator (which stores energy as highly compressed gas) and one or more hydraulic pump/motors rather than the battery pack, electric generator/motor and power electronics used in electric hybrids.

A number of commercial hydraulic applications are under development.

  • The EPA and its partner, Eaton Corporation–Fluid Power, will build the world’s first full diesel-hydraulic series hybrid delivery truck for UPS. The hybrid system is based on numerous EPA pioneering hybrid patents. (Earlier post.)

  • Peterbilt and Eaton Corporation are jointly developing refuse trucks using Eaton’s parallel hydraulic hybrid system for Hydraulic Launch Assist (HLA). (Earlier post.)

  • Beijing will soon begin a large scale of test of hydraulic hybrid technology deployed on 50 buses, using technology developed by Chargeboard Electric Vehicle Co. (Earlier post.)

The mission of the Working Group is to create greater awareness of hydraulic hybrid technology, to advance its commercialization for use in automotive and commercial vehicle applications, and to develop technology-neutral standards and policies for hydraulic hybrid vehicles.

EPA testing has shown hydraulic hybrid drivetrains can produce over 80 miles per gallon for a midsize family sedan that also incorporates improved tires and aerodynamics.

NextEnergy’s partners in founding the Working Group include Dana Corporation, Eaton Corporation, Hybra-Drive Systems, Hydraulic Innovations LLC in a partnership with Altair Engineering, Southwest Research Institute, and the University of Michigan. The Working Group is also collaborating with the US EPA in its efforts.



Sound like a very promising technology, and no rocket science behind. The hydralic parts surely can be made last longer and cheaper then a huge Li-ion batteries.


ya but can't be put on small cars! i hope the price is right too.

A Syme

Ask anyone who works on equiptment that is powered by hydraulics, these systems love to leak, and they are usually higher maintainance than an equivlent electric powered system.


Hi just dropped in to answer a few questions. 1st ths std disclaimers. This is personal opinion offered by a company rep to the HHWG and do not necessarily represent the opinions of my employer or the HHWG.

Yes it can be put on small cars. I know of several implimentaions; however I will not directly speak on those because they are not projects that I'm personally involved in.

Higher maintainance. Not true for the equipment that has been designed for this purpose. The industry knows that if the reliabilty is less than that of current car technology that it will see limited acceptance (read sales). Limited acceptance causes cost issues that will cause further loss in sales, etc .....

Finally price. It will be higher than a convential car. But when developed as well as
a Prisus (as an example)I'm GUESSING (however a pretty safe bet)that the cost could be less than half of an electric hybrid.


Hydraulic system reliability has come a long way in the past 20 years. When is the last time you had a leak in your power steering system? Constuction and agricultural equipment have taken the lead in high pressure hydraulics, and for them, down time is money. Power density is another plus when comparing hydraulic with electric machinery. Cost is yet to be proven for high volume, high pressure machinery, but the outlook is favorable.


This seems like promising technology. It seems like some weight reduction might be possible by converting some structural components into hydraulic energy storage containers, e.g. frame. I thought of this for a potential user group that I've not seen much efficiency enhancement information on. Railroad engines and cars would seem to be well suited to take advantage of hydraulically stored energy. I see them start and stop all over my town, not to mention the commuter transit trains.


How do the hydrostatic transmissions (direct and with accumulator) compare in efficiency to normal mechanical gearboxes.
Generally. I believe a normal transmission loses 10% to 15% between crankshaft and wheels. Is the hydraulic system better or worse.
Also have you considered 2 stroke diesel technology. These engines are clean and have have minimal pumping losses as they don't pull air or fuel through the crankcase.
I believe a design like this German aero engine www.zoche.de could be incredibly powerful and fuel efficient.


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