Series HHVs

Hydraulic Hybrid Vehicles, better known as HHVs, have two major system types. The first is a series HHV. These vehicle models rely solely on pressurized fluids in order to turn the wheels. When the accelerator is pressed, pressurized nitrogen pushes hydraulic fluid through the pump motor. The pump motor then uses this pressurized fluid to turn the wheels. In this system, an HHV’s internal combustion engine is connected to the hydraulic motor. This connection results in more pressure within the fluids of the hydraulic motor, which results in a more powerful hydraulic motor. In series HHVs, the internal combustion engine is not used to turn the wheels on the vehicle but rather to assist the hydraulic motor in the production of power in the vehicle.

Advantages to Series HHVs

 * Major fuel savings due to lack of engine use.


 * Carbon Dioxide and greenhouse gas emisions drastically decreased.


 * Savings on brake maintenance due to regenerative braking.      


 * Very quiet due to lack of engine use.


 * Effective in urban, suburban, and rural areas.


 * No need to charge like many electric cars and electric hybrids.

How a Series HHV Works While Accelerating
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 * 1) Gas pedal is pressed
 * 2)    Pressurized Nitrogen in the high pressure tank/accumulator pushes  hydraulic fluid across the pump motor.
 * 3) Pre ssurized fluid moving across pump motors turns the wheels.
 * 4) Fluid that moved across pump motor is not depressurized.
 * 5) Depressurized fluid moves into low pressure reservoir tank.



Series HHV Cruising
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 * 1) When high pressure fluid reaches a certain, low level, the engine  turns on. 
 * 2) Turned on engine pressurizes low pressure fluid in the reservoir tank.
 * 3) Newly pressurized fluid is pushed across the pump motor to continue  <span style="color:rgb(217,217,217);font-size:14px;">movement of the vehicle.
 * 4) <span style="color:#D9D9D9;mso-themecolor:background1; mso-themeshade:217;mso-style-textfill-fill-color:#D9D9D9;mso-style-textfill-fill-themecolor: background1;mso-style-textfill-fill-alpha:100.0%;mso-style-textfill-fill-colortransforms: lumm=85000">Excess high pressure fluid produced by engine is stored back in the  <span style="color:rgb(217,217,217);font-size:14px;">accumulator.

Series HHV Braking (Rgenerative Braking)

 * 1) Brake pedal is pressed.
 * 2) Engine shuts off.
 * 3) Vehicle slows down by using vehicle's kinetic energy to re-pressurize fluid in the reservoir.
 * 4) Re-pressurized fluid is moved across the pump motor back into the accumulator.

References/Sources
EPA Series Info

Series HHV Video

Series HHV 2D Diagram

Series HHV 3D Diagram