NIDHIN C.

HYBRID SYSTEM

A hybrid vehicle is a vehicle that uses two or moredistinct power sources to move the vehicle.

It helps in attaining better fuel, or better performance,or even better emission economy than a conventionalvehicle.

Electric power, Hydrogen, Hydraulic, Compressed air,Liquid nitrogen, Compressed or liquefied natural gas,Solar.

HYDROSTATIC REGENERATIVE

BRAKING SYSTEM (HRB)

The principle is “Recover Energy – Reduce Emissions”.

The energy lost in braking is stored in a hydraulic

accumulator and then used for powering the vehicle.

Hydraulic hybrids are ideal for vehicles with frequent,

short start-stop cycles, such as public transit buses,

refuse trucks, forklifts, pneumatic tire rollers, and

much more.

CHARACTERISTICS OF A HYDRAULIC HYBRID

High power density.

The HRB stores a vehicle’s kinetic energy, which would otherwise

be lost during mechanical braking operation. This energy is then

available for powering the vehicle and reducing primary energy

use. To ensure that Hydrostatic Regenerative Braking System

reaches its full potential, the following conditions need to be met:

High vehicle mass and strong active deceleration for

accumulating a large amount of energy in a short time.

Frequent starting and braking.

Low rolling resistance to store the maximum braking energy

PARALLEL AND SERIES HRBFor heavy vehicles with short, succeeding start-stop cyclesthere are two different Hydrostatic Regenerative BrakingSystems for capturing the braking energy.

• The parallel HRB was developed especially for vehicleswith no hydrostatic drive. The HRB components areinstalled in the vehicle as an ancillary system.

• The series HRB is used in vehicles with a hydrostaticdrive. The hydraulic components used in the system aresupplemented with two pressure accumulators and theappropriate control and valve technology

PARALLEL HRB

The parallel HRB is a hydraulic hybrid forvehicles with no hydrostatic transmission.Use of an HRB system results in significantfuel savings of up to 25% and improvedacceleration – depending on the focus of theapplication.

Storing braking energyThe hydraulic axial piston unit 1 iscoupled to the mechanical drive trainthrough a gearbox 2 When braking, theaxial piston unit converts kinetic intohydraulic energy and pumps hydraulicfluid into the pressure accumulator 3,increasing the pressure in theaccumulator.

Reusing the stored energy to assist the vehicle drive

The pressurized hydraulic fluid in theaccumulator drives the axial piston unit,which now acts like a motor. Hydraulicenergy is converted into kinetic energy. Theaxial piston unit remains coupled to themechanical drive train until the pressureaccumulator is discharged. The valvecontrol block 4 controls the filling anddischarge cycle and protects theaccumulator from excessive pressure. Theelectronic controller 5 � operates the HRB.In “normal” drive mode the HydrostaticRegenerative Braking System is decoupled.

COMPONENTS

Axial Piston Unit& Gearbox

Hydraulic PressureAccumulator

Pressure Relief Valve

Valve Control Block HIC Electronic Controller RC

REAL WORLD EXPERIMENTSimulated cost savings using the example of a refuse collectiontruck On a refuse truck (16 tons) the use of the parallel HRB canresult in saving of up to 2.25 liters of fuel per hour. The annualoperating costs can thereby be reduced significantly.

SERIES HRBThe series HRB makes full use of the

Components in an existing hydrostatictransmission – so the system can easily beintegrated into these vehicles. The seriesHRB provides significant fuel savings, forexample on forklifts, swap body movers,,pneumatic tire rollers and other heavy-dutyvehicles.

Storing the braking energy

During braking the drive motor 1 behaveslike a pump. It converts kinetic energy intohydraulic form and fills the pressureaccumulator 2 with hydraulic fluid,resulting in rising pressure in theaccumulator.

Return of the accumulated energy for assisting the vehicle transmission

At startup, the drive pump 3 is used as with atraditional hydrostatic transmission. Itcontinues to run in energy saving mode aslong as the pressurized hydraulic fluid isbeing fed to it from the accumulator. Thevalve control block 4 protects theaccumulator from excessive pressure andcontrols filling and discharge. The electroniccontroller 5 operates the HRB.

ADDITIONAL COMPONENTS NEEDED FOR A SERIES HRB

Two Hydraulic Pressure Accumulators

Pressure Relief Valve Valve Control Block

Electronic Controller

REAL WORLD SIMULATION TESTSimulated fuel savings on a forklift showed that the seriesHRB system can save up to 1.1 liters of fuel per hour on aforklift (load 3.5 to 5 tons). This significantly reducesoperating costs.

ADVANTAGES OF THE HRBEnvironment:

• Fewer harmful emissions, less pollution.

• Help in meeting future emissions and environmentalrequirements.

• Reduced brake wear, lower braking noise, and less brakedust.

Function:

• High functional reliability and low risk of failure.

• Simple maintenance and long service life.

• Ideal solution for new systems or retrofits.

COSTS:

• Significant reduction in operating costs.

• Durable components reduce maintenance needs.

• More economical than other hybrid concepts.

ENERGY:

• Reduced fuel consumption to preserve energy.

• Fuel-neutral system – can be combined with diesel, gasoline, or other types of motors.

• Increased vehicle range.

ELECTRIC HYBRID SYSTEM• An electric hybrid vehicle combines a conventional

internal combustion engine propulsion system with anelectric propulsion system.

• The presence of the electric power train is intended toachieve either better fuel economy than a conventionalvehicle, or better performance, or better emissions.

• Modern electric hybrid vehicle make use ofregenerative braking, which converts the vehicle'skinetic energy into electric energy, rather than wastingit as heat energy.

HYBRID VEHICLE POWER TRAIN CONFIGURATIONS

PARALLEL HYBRID

• In a parallel hybrid the electric motor and the internalcombustion engine are installed so that they can bothindividually or together power the vehicle. Mostcommonly the internal combustion engine, the electricmotor and gear box are coupled by automaticallycontrolled clutches. For electric driving the clutchbetween the internal combustion engine is open whilethe clutch to the gear box is engaged. While incombustion mode the engine and motor run at the samespeed.

MILD PARALLEL HYBRID:

This types use a generally compact electricmotor to give extra output during theacceleration, and to generate electricityusing regenerative braking on thedeceleration phase.On-road examplesinclude Honda Civic Hybrid, Honda Insight,Mercedes Benz S400 BlueHYBRID, BMW 7-Series hybrids, and Smart fortwo with microhybrid drive.

POWER SPLIT HYBRID:

• In a power split hybrid electric drive train there arealways two electric motors and one internalcombustion engine. One motor mostly acts as agenerator while the other one is used as a motor orgenerator. The two motors are connected through aplanetary gear set. On the open road, the primarypower source is the internal combustion engine butwhen maximum power is required, the electricmotors are used to maximize the available power fora short time, giving the effect of having a largerengine than that actually installed. The ToyotaPrius, the Ford Escape and the Lexus Gs450 andLS600 are power split hybrids

SERIES HYBRID:

A series hybrid uses an electric motor(s), which is poweredby a single-speed internal combustion engine. Whileoperating at its most efficient single speed, the combustionengine drives an electric generator instead of directlydriving the wheels. This engine can do any combination ofthe following: charge a battery, charge a capacitor, directlypower the electric motor. When large amounts of powerand torque are required, the electric motor can drawelectricity from a combination of batteries, capacitors, andthe generator. A series hybrid does not require batteries inits design as a capacitor can act as a storage device.

PLUG-IN HYBRID ELECTRICAL VEHICLE (PHEV)

Another subtype added to the hybrid market is the Plug-in Hybrid Electric Vehicle (PHEV). The PHEV is usually ageneral fuel-electric (parallel or serial) hybrid withincreased energy storage capacity (usually Li-ionbatteries). It may be connected to mains electricitysupply at the end of the journey to avoid charging usingthe on-board internal combustion engine. Roademissions can be reduced by avoiding – or at leastminimizing – the use of ICE during daily driving. As withpure electric vehicles, the total emissions saving, forexample in CO2 terms, is dependent upon the energysource of the electricity generating company.

FUEL CELL, ELECTRIC HYBRID:

• The fuel cell hybrid is generally an electricvehicle equipped with a fuel cell. The fuel cell aswell as the electric battery are both powersources, making the vehicle a hybrid. Fuel cellsuse hydrogen as a fuel and power the electricbattery when it is depleted. The ChevroletEquinox FCEV, Ford Edge Hyseries Drive andHonda FCX are examples of a fuel cell/electrichybrid.

CONCLUSION While driving in the city or vehicles with short,succeeding start-stop cycles, the energy needed forovercoming the rolling and aerodynamic resistance isabout half the resistance during the highway part. TheHybrid transmission strongly reduces the fuelconsumption and the related CO2-emission of avehicle, especially during these operating conditions.