NIDHIN C.
HYBRID SYSTEM
A hybrid vehicle is a vehicle that uses two or more distin distinct ct pow power sour sources ces to mov move the vehicle. ehicle. It helps in attaining better fuel, or bett be tter er performance, or even better emission economy than a conventional vehicle. 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 HRB For heavy vehicles with short, succeeding start-stop cycles there are two different Hydrostatic Regenerative Braking Systems for capturing the braking energy. The parallel HRB was developed especially for vehicles with no hydrostatic drive. The HRB components are installed in the vehicle as an ancillary system. The series HRB is used in vehicles with a hydrostatic drive. The hydraulic components used in the system are supplemented with two pressure accumulators and the appropriate control and valve technology •
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PARALLEL HRB The
parallel HRB is a hydraulic hybrid for vehicles with no hydrostatic transmission. Use of an HRB system results in significant fuel savings of up to 25% and improved acceleration – depending on the focus of the application.
Storing braking energy The hydraulic axial piston unit 1 is coupled to the mechanical drive train through a gearbox 2 When braking, the axial piston unit converts kinetic into hydraulic energy and pumps hydraulic fluid into the pressure accumulator 3, increasing the pressure in the accumulator.
Reusing the stored energy to assist the vehicle drive The pressurized hydraulic fluid in the accumulator drives the axial piston unit, which now acts like a motor. Hydraulic energy is converted into kinetic energy. The axial piston unit remains coupled to the mechanical drive train until the pressure accumulator is discharged. The valve control block 4 controls the filling and discharge cycle and protects the accumulator from excessive pressure. The electronic controller 5 operates the HRB. In “normal” drive mode the Hydrostatic Regenerative Braking System is decoupled.
COMPONENTS
Axial Piston Unit & Gearbox
Valve Control Block HIC
Hydraulic Pressure Accumulator
Pressure Relief Valve
Electronic Controller RC
REAL WORLD EXPERIMENT Simulated cost savings using the example of a refuse collection truck On a refuse truck (16 tons) the use of the parallel HRB can result in saving of up to 2.25 liters of fuel per hour. The annual operating costs can thereby be reduced significantly.
SERIES HRB The series HRB makes full use of the Components in an existing hydrostatic transmission – so the system can easily be integrated into these vehicles. The series HRB provides significant fuel savings, for example on forklifts, swap body movers,, pneumatic tire rollers and other heavy-duty vehicles.
Storing the braking energy
During braking the drive motor 1 behaves like a pump. It converts kinetic energy into hydraulic form and fills the pressure accumulator 2 with hydraulic fluid, resulting in rising pressure in the accumulator.
Return of the accumulated energy for assisting the vehicle transmission At startup, the drive pump 3 is used as with a traditional hydrostatic transmission. It continues to run in energy saving mode as long as the pressurized hydraulic fluid is being fed to it from the accumulator. The valve control block 4 protects the accumulator from excessive pressure and controls filling and discharge. The electronic controller 5 operates the HRB.
ADDITIONAL COMPONENTS NEEDED FOR A SERIES HRB
Two Hydraulic Pressure Accumulators
Pressure Relief Valve
Electronic Controller
Valve Control Block
REAL WORLD SIMULATION TEST Simulated fuel savings on a forklift showed that the series HRB system can save up to 1.1 liters of fuel per hour on a forklift (load 3.5 to 5 tons). This significantly reduces operating costs.
ADVANTAGES OF THE HRB Environment: •
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Fewer harmful emissions, less pollution. Help in meeting future emissions and environmental requirements. Reduced brake wear, lower braking noise, and less brake dust.
Function: • • •
High functional reliability and low risk of failure. Simple maintenance and long service life. Ideal solution for new systems or retrofits.
COSTS: •
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Significant reduction in operating costs. Durable components reduce maintenance needs. More economical than other hybrid concepts.
ENERGY: •
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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 •
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An electric hybrid vehicle combines a conventional internal combustion engine propulsion system with an electric propulsion system. The presence of the electric power train is intended to achieve either better fuel economy than a conventional vehicle, or better performance, or better emissions. Modern electric hybrid vehicle make use of regenerative braking, which converts the vehicle's kinetic energy into electric energy, rather than wasting it as heat energy.
HYBRID VEHICLE POWER TRAIN CONFIGURATIONS PARALLEL HYBRID •
In a parallel hybrid the electric motor and the internal combustion engine are installed so that they can both individually or together power the vehicle. Most commonly the internal combustion engine, the electric motor and gear box are coupled by automatically controlled clutches. For electric driving the clutch between the internal combustion engine is open while the clutch to the gear box is engaged. While in combustion mode the engine and motor run at the same speed.
MILD PARALLEL HYBRID:
This types use a generally compact electric motor to give extra output during the acceleration, and to generate electricity using regenerative braking on the deceleration phase.On-road examples include Honda Civic Hybrid, Honda Insight, Mercedes Benz S400 BlueHYBRID, BMW 7Series hybrids, and Smart fortwo with micro hybrid drive.
POWER SPLIT HYBRID: •
In a power split hybrid electric drive train there are always two electric motors and one internal combustion engine. One motor mostly acts as a generator while the other one is used as a motor or generator. The two motors are connected through a planetary gear set. On the open road, the primary power source is the internal combustion engine but when maximum power is required, the electric motors are used to maximize the available power for a short time, giving the effect of having a larger engine than that actually installed. The Toyota Prius, the Ford Escape and the Lexus Gs450 and LS600 are power split hybrids
SERIES HYBRID:
A series hybrid uses an electric motor(s), which is powered by a single-speed internal combustion engine. While operating at its most efficient single speed, the combustion engine drives an electric generator instead of directly driving the wheels. This engine can do any combination of the following: charge a battery, charge a capacitor, directly power the electric motor. When large amounts of power and torque are required, the electric motor can draw electricity from a combination of batteries, capacitors, and the generator. A series hybrid does not require batteries in its 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 Plugin Hybrid Electric Vehicle (PHEV). The PHEV is usually a general fuel-electric (parallel or serial) hybrid with increased energy storage capacity (usually Li-ion batteries). It may be connected to mains electricity supply at the end of the journey to avoid charging using the on-board internal combustion engine. Road emissions can be reduced by avoiding – or at least minimizing – the use of ICE during daily driving. As with pure electric vehicles, the total emissions saving, for example in CO2 terms, is dependent upon the energy source of the electricity generating company.
FUEL CELL, ELECTRIC HYBRID: •
The fuel cell hybrid is generally an electric vehicle equipped with a fuel cell. The fuel cell as well as the electric battery are both power sources, making the vehicle a hybrid. Fuel cells use hydrogen as a fuel and power the electric battery when it is depleted. The Chevrolet Equinox FCEV, Ford Edge Hyseries Drive and Honda FCX are examples of a fuel cell/electric hybrid.
CONCLUSION While driving in the city or vehicles with short, succeeding start-stop cycles, the energy needed for overcoming the rolling and aerodynamic resistance is about half the resistance during the highway part. The Hybrid transmission strongly reduces the fuel consumption and the related CO2-emission of a vehicle, especially during these operating conditions.
