technologies can produce an ideal power supply. In other words, are hybrid engines the car technology of the future?
We have begun to research more efficient power sources, bearing in mind that many current cars are based on technology that is over a hundred years old. Plus, it is very dirty. Newer alternatives include fuels made from agricultural crops. But this agrofuel, which is also known as ‘biofuel’, is also problematic. What I mean is, there are always mechanical and economic pros and cons in new technologies. Anyway, we’ll look at biofuels later – I mean another day.
So, er … in later lectures, we’ll also go on to consider other options being researched by engineers, including even compressed air. Today, however, we will deal with the features of electric cars and hybrid cars.
Unit 7, Lesson 7.2, Exercise C ≤2.2
Part 2 As we have seen in earlier sessions, fossil fuel engines are currently quite inefficient. As we know, only about 20% of the energy in your fuel actually gets converted, or is used in moving the vehicle. But that is not the only concern.
Now, another term for fossil fuels is mineral fuels. And as well as being inefficient, burning them releases carbon dioxide into the atmosphere, as we saw previously. Now, CO2 is a greenhouse gas. ‘Greenhouse’ in this case can be thought of as trapping the sun’s heat around the earth, causing the average temperature to rise. In other words, as we continue to burn oil, natural gas and coal – and wood – the global temperature increases. And then, finally, we might see catastrophic results.
Unit 7, Lesson 7.2, Exercise E ≤2.3
Part 3 Now, an important concept in new car technology is regenerative braking. What do I mean by regenerative braking? I’ll explain.
Electric cars have huge advantages: no fuel tank,
oil pump or filter; no valves, cams, fan belts or clutch, like in an internal combustion engine. All this means is that an electric car is fairly simple under the hood; all it needs is a battery.
However, looking at it another way, there are serious drawbacks. First of all, batteries are currently not as good a method of energy storage as petrol fuel itself – they are quite heavy for the
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amount of energy they store. The idea of regenerative braking goes some way to solving this.
Let’s look at an example. Say you’re driving for a long time on a road with a lot of bends. When the brakes are applied, there’s a lot of kinetic energy going to waste as the vehicle slows down. The friction in the brakes generates energy in the form of heat that just dissipates into the air. In efficiency terms, this is a huge waste. To help you understand this idea clearly, you can look for a moment at the Monckton Industrial Research leaflet I have given you. As you can see, in a hybrid or electric car, that energy is converted into electricity by the motor (running as a generator) and stored in a battery. In this way, every time we decelerate, energy is stored for use later in the electric motor. The point is that by using the operation of the car to produce the power source, efficiency increases significantly.
Unit 7, Lesson 7.2, Exercise F ≤2.4
Part 4 Now … er … let’s see … oh dear, I see we’re running short of time … so let’s move on to the second new technology.
You’ve probably seen hybrid cars on the roads. So how are they different? Of course, the internal combustion engine is the conventional technology. In this type of technology, a fairly large engine capacity is required. The bigger engine allows a large and constant amount of power to be generated. This works against forces that cause drag. Examples of these forces are weight and friction. You can get from zero to high power very quickly. It also allows quick acceleration. But in fact, only a small amount of the engine power – perhaps about a tenth of the maximum capacity – is needed to drive at a steady pace. The additional power is there only for acceleration. And a big engine creates problems: it is heavy and inefficient at part load, and as a result requires the use of extra fuel.
A second possibility is to make a much lighter engine. What’s important with a lighter engine is that a much more efficient car can be produced. When we use small engines, we use smaller cylinders, holding less fuel and using lighter pistons, and we can control how we load it, and so save more fuel.
However, we would need to introduce some other way of giving us that extra boost power for acceleration. So lastly, we come to the hybrid
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