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Hybrid Cars
With some experts predicting that the demand for oil will outstrip supply as early as year 2015, the car industry is really going to have to pull out all the stops if we are all to be driving alternative fuel cars, or electric powered vehicles.
In recent years we have seen an explosion in the production of Hybrid Cars. Motor manufactures, it seems, are starting to take seriously the topic of alternative fuels.
Hybrid cars, which use both petrol and electricity for power, are perhaps the most talked about, but there are other forms of cars running on alternative fuels.
Regenerative Braking
One of the systems used is something called, regenerative braking. This works by harnessing kinetic energy that is normally lost during braking.
Regenerative braking, in the case of an electrically powered vehicle, works by using the electric motor that powers the car, also as a brake.
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Electric current is used to gain drive power from the output shaft of an electric motor, but if you drive the output shaft of the electric motor, the motor itself will produce electricity. The electricity obtained from an electric motor in this way is then be used to charge the batteries. However, when extracting electricity from an electric motor, by using it as generator, there is much resistance to overcome and this is how the motor provides a braking effect. The kinetic energy is used in this way to replenish battery packs fitted to the car, rather than losing it to the atmosphere as heat, as will be the case with conventional vehicle brakes. Hybrid Cars – An Old IdeaThe idea of using battery power for driving cars is not a new one, nor hybrid cars. As early as the turn of the 20th Century the idea of powering cars by both petrol and electricity was explored. The problem with powering cars by electricity has always been that of the amount space required, and the weight, of the lead and acid batteries. The more weight you add to a vehicle the more energy is required to move it, so the problem can never be solved by adding more batteries. The range is not good for cars using solely electric power provided by batteries. |
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There is a negative environmental issue with battery powered cars. Whilst you may not be putting harmful gases into the atmosphere whilst driving, because of the amount of electrical power required to re–charge your car batteries, the effect upon the environment can be worse than if you were driving a petrol engine.
Electric cars driven by solar panels is another idea that has been tried, but like the battery powered cars, the size and weight of solar panels makes their use impractical. Also, solar panels are not effective when driving at night.
Battery technology has come a long way in recent years, and this has been useful for electric cars and hybrid cars. Lithium batteries, for example, have a good weight to storage ratio.
Lithium batteries are being used in some hybrid vehicles. Sealed Nickel–Metal Hydride (Ni–MH) batteries are another popular choice, again for their electric power output versus size and weight ratio.
Hybrid cars use the normal petrol or diesel engines to drive the car and to power an on board generator that charges the batteries. This method re–charges the vehicle batteries and this energy can then be used to drive the car.
Toyota Prius – Hybrid Car
In the current batch of hybrid cars, Toyota was the first to launch the Hybrid car for the masses in 1997 with the Toyota Prius.
The Toyota Prius was shortly followed in 1999 by the Honda Insight. Both of these cars have a mechanical linkage from their petrol driven engines capable of driving the drive wheels. They also can use the electric motors to drive the car without any linkage to the petrol engine. The cars can be driven by the petrol engine and electric power at the same time.
The petrol engine of the Toyota Prius, a 1.5–litre 4–cylinder unit, can run at an engine speed that is independent to the speed of the car. In other words, engine speed and road speed do not have to be the same.
The Toyota Prius has what is known has what is known as a parallel hybrid powertrain. This hybrid car will operate between the speeds from zero to 40mph using the electric power stored in the vehicle batteries and power from the onboard generator.
Above that speed the petrol engine cuts in and provides drive for the car, supplementing the power from the petrol engine. This is all managed through a special gearbox using what is called a sun gear and planet gears.
Whilst the electrical generator is being driven by the petrol engine the batteries of the car are re–charged so there is plenty of electric power ready to drive the car when at slower speeds.
The hybrid car is fitted continuously variable transmission, which means there is no gear changing going on so the car is always running at its greatest level of efficiency.
Electrical Drive and Petrol Engine
When you pull away from the traffic lights, for example, initially the electric motors drive the car with the batteries providing all the power. This also spins the generator, which produces more electrical power.
At about 40mph, the petrol engine fires in and remarkably runs at a constant speed. The generator will then vary its speed to match the output demand made by the electric motor. If the driver needs to accelerate hard and electrical power that cannot be supplied directly from the generator comes from the batteries.
At cruising speed the system will use both petrol engine power and electrical power from the generator. The onboard generator in the Toyota Prius, mounted behind the engine, always maintains the required level of power within the batteries. Therefore, the car never has to be plugged into the mains supply of electricity.
On the instrument panel of the Toyota Prius, so as to monitor the electrical charge system, there is a system of lights on a diagram.
The dashboard display tells the driver if the car is driving on electrical power from the batteries, power from the generator, from the engine or both petrol and electricity power. The indicator to show if the electrical system is healthy is, and rather appropriately, a green light.
There is also a graphic that give you details of your petrol consumption over the last 30–minutes of driving.
Toyota Prius Has no Reverse Gear
Rather interestingly, there is no reverse gear on the Toyota Prius. This is because it never needs the engine to drive backwards, as all the power for this comes from the electric motors.
The engine of the Toyota Prius operates in a very narrow rpm band and is always kept within its most efficient operating rpm range. By burning petrol efficiently to generate electric power, and using that electric power to drive the car, the overall fuel efficiency makes the Toyota Prius one of the best in its class.
When car companies like Honda and Toyota, as well as others, first launched their hybrid cars the was much scepticism. If fact, many journalists saw them as joke and took every opportunity to poor scorn in the idea of Hybrid cars.
The Bush administration, for example, when speaking of the threat of global warming and the situation of greenhouse gas emissions, almost dismissed the idea of engineering change on the grounds it was financially unsustainable.
Considering the Toyota Prius, when it was first released in May 1997 was seen by most as joke, by 31st August 2009 2–million units had been sold worldwide. What is even more remarkable is one of the top selling cars in America is the Toyota Prius.
Hybrid cars are now predicted by experts to be well on the way to taking a core segment of the automotive market of the future.
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This page was last updated
Friday, 28-Jan-2011
Hybrid Cars, Such as the Toyota Prius
