Today, with almost every major country joining the development race, the demand for fuel is on the rise and the need to look for alternative sources of fuel looms large. One area of research taken up by auto companies has been finding practical and efficient solutions to sources of fuel for vehicles.
A couple of years ago, hybrid technology emerged, and has been put into production ever since. Hybrid technology, as the name suggests, involves the use of one other source of power to move the vehicle, besides the internal combustion engine. The most commonly used source of power in present hybrids is electricity. However, the electric hybrids have not been without their share of woes. Impracticability for daily use and high costs have kept these systems from being adopted worldwide on a day-to-day basis.
It is at such a time that the development of hydraulic hybrid systems brings in a ray of hope in reversing the plummeting crisis of alternative fuel sources. Promising efficiency, peak performance and low costs, the hydraulic hybrid system seems to be where the future of motoring lies.
In a hydraulic hybrid, power comes from pressurized fluid in addition to the internal combustion engine propulsion that helps in better fuel economy than the conventional system. The hydraulic hybrids help in economising on fuel consumption by recovering and reusing the kinetic energy of the vehicle during braking and deceleration, and converting it into reusable potential energy. Hydraulic hybrids can do this much more efficiently and effectively than electrical hybrids, which use batteries for the purpose.
The hydraulic hybrid system basically consists of a fluid, a pump, a reservoir, and an accumulator. In some advanced systems, a hydraulic transformer is included in order to convert output flow at any pressure. The system uses the kinetic energy generated during braking to pump the fluid from the reservoir to the accumulator. The fluid is pressurized at this time and when the vehicle accelerates again, the pressurized fluid provides the energy to the pump to deliver the power to move the vehicle. This process converts kinetic energy to potential energy that can be reused; the process is called regenerative braking.
Two types of hydraulic hybrids exist, depending on where the output from the pump goes to. In a parallel system, the pump provides the power to the engine during acceleration. In a series system, the pump is directly connected to the wheel shaft.
The basic principle of regenerative braking system operates best in the present-day stop-and-go traffic systems, prevailing in most cities of the world. Hydraulic hybrid systems can be installed in most of the vehicles in use today, such as utility vehicles, family sedans, buses, trucks, and even bicycles.
Hydraulic hybrids have been proven to be more cost-effective than electric hybrid systems. This is mainly due to the absence of expensive materials used in it, unlike those required for batteries.
Fuel efficiency has been proven to increase dramatically in vehicles powered with series hydraulic hybrid systems. As the engine is shut off when not needed, its use is cut almost by half in the present-day urban driving scenario with dense traffic conditions.
Hydraulics systems can recover about 75% of the kinetic energy during braking and deceleration, as compared to the 25% recovery from electric hybrids, which clearly indicates the high efficiency of hydraulic hybrid systems. This system results in reduced brake maintenance by reducing the brake friction that often results in wear and tear. Coupled with the fuel efficiency it brings, hydraulic hybrid powered vehicles can result in saving up a lot of money on the maintenance of a vehicle, in addition to superior performance. Technical challenges lie in areas such as noise, size, and complexity in design.
Despite the initial hiccups, continuous innovation and research in the field has resulted in breakthroughs to make the system more efficient. Smaller, lighter, and more efficient designs for pumps and accumulators have helped in applying the system to both small consumer vehicles, as well as large, heavy-duty, commercial vehicles.
Contributed by Tom McShane, engineering blogger and writer for UK-based Apex Hydraulics.