Hybrid technologies explained
There are different types of hybrid drivetrains currently being used. Because they're relatively new, hybrid technologies will continue to be varied and experimental for a while. Expect hybrid technologies to rapidly improve over the next few years as manufacturers pour millions into this emerging market. The plug in hybrid and series hybrid are the newest hybrid technologies you can expect to see in the latest cars.Parallel hybrid - Hybrid technologies are varied but currently this set up is the most popular. An electric motor and an internal combustion engine are installed so that they can both individually or together power the vehicle. Typical passenger car installations such as those from Toyota and Lexus use electric power for reversing, and low speed low throttle opening work because it uses less energy and does not require any energy while the car is idle, making hybrid vehicles ideal for urban and suburban environments. As the vehicle speed increases or the acceleration demanded is higher, the internal combustion engine starts and both power units work together in parallel (hence the name). Internal combustion engines deliver more power for a given motor weight, making them better suited for higher speeds. The installed electric motors and battery capacity may offer a range of 3-5km in pure electric mode, at speeds of up to 40km/h. Beyond this, the internal combustion engine is needed to either provide increased power or to recharge the batteries. On the open road, the primary power source is the internal combustion engine (partly to maximise the life of the batteries), but when maximum power is required, for example to overtake, the electric motor is used to maximise the available power for a short time, giving the effect of having a larger engine than that actually installed. The fuel consumption benefits of a hybrid electric vehicle against an internal combustion vehicle of similar performance come through the recovery of braking energy, stored in the battery by the motor/generator for use at the next start which in a conventional vehicle would have been dissipated as heat from the brakes. Additionally, the ability to shut off the engine while the electic motor is running brings further savings. The larger the motor, and the battery, the more braking energy it can recover before conventional brakes are necessary to achieve the required retardation. However, a weight/space compromise determines the limits of energy recovery possible in a given installation.
Mild hybrid - uses a generally smaller electric motor only to assist the gasoline engine when it needs extra boost, again during brisk acceleration or when going up a hill. The main improvement in fuel consumption over a conventional vehicle with the same performance is possible by the installation of a smaller internal combustion engine, with smaller internal losses and lower weight. There are also savings through energy recovery through the motor/generator on the overrun and while decelerating. This electrical energy may be used to drive the a/c, power steering, and other auxiliaries electrically as and when needed as opposed to continuously with traditional belt-driven pumps, reducing mechanical losses and so improve the fuel consumption. Manufacturers claim savings of approximately 15% fuel consumption against a conventional vehicle of similar performance.
Plug in Hybrid - An addition to the hybrid market is the Plug in Hybrid Electric Vehicle (PHEV). The plug in hybrid usually consists of a gasoline-electric 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. This concept is attractive to those seeking to minimise on-road emissions by avoiding - or at least minimising - the use of ICE during daily driving. Think of a plug in hybrid as a purely electric car, but with the security of backup power from an internal combustion engine to avoid the range limitations of solely electric cars. 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. The plug in hybrid should also be financially attractive so long as the electrical energy being used is cheaper than the petrol/diesel that they would have otherwise used.
Series hybrid - The lastest hybrid technologies use electric motors 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. But the series hybrid design can also be used as a purely electric car but with the security of backup power from an internal combustion engine, the difference being it doesn’t drive the wheels but an electric generator.