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Hydraulic Hybrid Systems and EMI Partner to Target Fleet Retrofit Market; First Retrofit Underway

HHS upfit system. Click to enlarge.

Hydraulic Hybrid Systems, LLC (HHS), a recently-formed subsidiary of Lightning Hybrids Inc. (earlier post), is partnering with Equipment Maintenance Innovators (EMI-Global) to distribute HHS hydraulic hybrid retrofit systems for light- and medium-duty commercial fleet vehicles.

HHS’s upfit solution is a high-efficiency, light-weight parallel hydraulic hybrid propulsion system inserted within the driveline of a vehicle. This system is designed and engineered to be installed in fourteen hours, including all controls and wiring harness, by a certified installer. HHS says that its system is expected to deliver at least a 40% improvement in fuel economy made possible through regenerating braking energy that is then used during acceleration.

The first conversion of the partnership is already underway, a MY 2002 CNG Chevrolet HD 2500 provided by Denver International Airport. The truck is used for runway checks and plowing. The hybrid system is currently being finalized, installed and tested at HHS’s shop in downtown Loveland, Colorado and the truck prototype will be put back into runway service in early October 2009.

HHS has also purchased a totaled 2008 Chevy Silverado HD 2500 that will serve as a demonstration vehicle. The truck has been stripped down almost to a bare chassis and will have a plexiglass floorboard to show the system as it works. Other vehicle platforms will be prototyped in the near future to meet the needs of current fleets.

Hydraulic hybrids have been around for a while, but there has been no reason until now to explore these kinds of technologies. Now is the time to move forward with hydraulics because of the push to cut emissions and dependence on foreign oil. Batteries just cannot address issues for fleets at the scale that we need.

—Richard LeFrancois, founder and president of EMI-Global

HHS system on the test stand. Click to enlarge.

Genesis of HHS. In late 2008 Loveland-based Lightning Hybrids began engineering a biodiesel hydraulic hybrid vehicle that combined a small biodiesel engine with a 150 hp hydraulic pump on a lightweight sports sedan. The first prototype was displayed at the Denver Auto Show in April 2009. At that show questions arose from a number of fleet managers about the prospect of applying the hydraulic hybrid as a retrofit to existing fleet vehicles.

We explored the opportunity and found a need for fuel and emissions savings in the light-duty fleet market. A hydraulic hybrid retrofit system is an excellent answer in situations where the light duty fleet vehicle does a lot of start and stop driving, such as city and state fleet vehicles, vocational and contractor trucks and vans, mining and oil field vehicles, and school buses.

—Dan Johnson, CEO of HHS

In late April 2009 Lightning Hybrids’ engineering team started the design and implementation of a hydraulic hybrid system that could be applied to fleet vehicles. Lightning Hybrids established Hydraulic Hybrid Systems, LLC in July 2009 to manage the manufacturing and distribution of the system.

The HHS system. A parallel hydraulic hybrid system is similar to many of the electric hybrid vehicles on the market today, but stores recaptured braking energy in hydraulic accumulators rather than a battery. The main components of a parallel hydraulic hybrid system are:

  • Hydraulic Pump/Motor, a variable displacement, axial piston type pump. This type of closed circuit pump has been used reliably in various hydraulic applications for many years. Depending on which port is pressurized, the pump/motor can operate in both counter-clockwise and clockwise directions and as a pump or motor with the same efficiency of between 85% and 90% depending on speed. Because of this characteristic, the pump/motor can either add power to the system or be used to pump hydraulic fluid to a high pressure accumulator and store that energy for use in its opposite mode of operation.
  • Hydraulic accumulator.
  • The conventional automotive drivetrain.

The hydraulic pump/motor is coupled to the driveline via a belt and clutch. The pump captures braking energy and stores it in accumulator. Upon acceleration, the pump becomes a motor that uses the stored energy in the accumulators to provide torque to power the wheels. The large fuel efficiency gains are achieved by regenerating the braking energy that is normally lost to heat, and using this energy instead of (and in addition to, if needed) the internal combustion engine for acceleration.

The HHS hydraulic hybrid system includes a heavy-duty Eaton hydraulic pump and motor, an ASTM-certified high pressure accumulator tank, a low pressure reservoir, a valve block, HHS control system, brackets and associated certified hoses.



That looks very complex...and it takes FOURTEEN hours to install per vehicle? If it is indeed at least a 40% improvement in fuel economy, the benefits better seriously outweigh the costs. If I'm a small business owner with a fleet of specialized light & medium duty vehicles, the last thing I'd need is a vehicle that is out of commission for a long period of time, getting costly repairs at some distant location, because garden-variety mechanics have no idea how to fix such a system.



How do you rate this one.

Nick Lyons

Good solution for medium-to-heavy vehicles with stop & go duty cycle:

Delivery vans.
School buses.
Garbage trucks.

Henry Gibson

I have an automatic reaction against parallel hybrids because most of them require the engine to run when the vehicle moves. But this may not always be decisive. The Kitson-Still locomotive was a parallel steam-diesel hybrid that the Chinese should copy with modern materials and technology.

Such locomotives would still be running in the US if they had been invented by Southern Pacific in the US instead of Kitson in the UK. Most Southern Pacific steam locomotives ran on oil because California had much oil and almost no coal.

Artemis removed an entire transmission and retrofitted a car with their electronic pump valve system and cut the fuel use to one half in stop-go service. This was without using a smaller, more efficient engine but with the identical engine. Unfortunately Bosch now owns the highway use rights to this system which could undermine profits of their other efforts to improve efficiency if implemented.

This system has similarities to the UPS delivery truck hybrid system that also had an automobile prototype. Any type of hybrid saves fuel and a 1930s mechanic could understand and repair hydraulics. ..HG..


There is multiple demonstration that prove that this technic is efficient and robust but still no commercial application. I think it is much better suited to pick up and truck than electric hybrid, it is more efficient at recovering braking energy than electric hybrid, lighter, cheaper doesn't require sensitive material like copper, rear-earth or lithium or Ni. A 3Tons pick up with a Turbo-Diesel-Miller Cycle engine and this system and some aerodynamic improvement could get close to 30MPG.

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