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Thursday, 27 October 2011

Electric Cars - Concepts, Practicality and Future – Part One

The electric vehicle (EV) is at a decisive point. Despite major manufacturers within and outside the car industry working on various systems and governments professing their support, there are considerable obstacles ahead. Many challenges, particularly in terms of infrastructure, remain. Yet, there was a time when electrons as the driving force had the upper hand.

Early Success

The EV is closely linked to the development of the battery. After all, who would want to drive around in a car that is tethered to a socket at home by a fifty-mile-long power cable? Monty Python quite rightly assumed that no one expected the Spanish inquisition but neither would pedestrians, dogs and other exposed creatures to be mowed down by a supersized flex.

Alessandro Volta built the first battery in 1800 after he had realised that a current could flow between two different metals. The potential of his discovery was soon recognised and if you thought the EV was a recent invention driven by environmental concerns you are in for a shock. In those days the central idea was that of getting rid of the horses but still have a carriage moving forward. Reducing pollution or saving fossil fuels was simply not on the agenda.

Inventors looked at many different means of propulsion. A number of people worked with electricity but American Thomas Davenport and Robert Anderson from Scotland are credited with constructing the earliest proper models between 1834 and 1842. As you can see, recycling works in many different ways in renewable energy. Ideas are no exception and modern designs using concepts that are over 150 years old are proof of that.

There is no better example than a certain German sports car manufacturer. Ferdinand Porsche developed the electric wheel hub motor and displayed his car, constructed at the Viennese carriage builder Lohner, at the World Exhibition in Paris in 1900. It caused a stir and was on sale for about $135,000 in today’s money. That system was purely electrical but only a short while later he assembled the first true hybrid! A petrol (gasoline) engine acted as a generator and a battery provided temporary storage. Now the principle has come back in the current Panamera Hybrid, which is a bargain at $95,000 compared to its ancestor.

Decline and Resurgence of the Electric Car

At the time of the Lohner-Porsche EVs outsold all other types in America and Camille Jenatzy, a Belgian racing driver, had broken the coveted 100 km-per-hour-barrier (62.15 mls/h) in his electric La Jamais Contente in 1899. In fact, electric cars were so dominant that the first land speed record by means of different propulsion was not achieved until 1902.

EdisonElectricCar1913 (with reference)
Unfortunately, the same problems beset the industry then, as today. People wanted to travel more than the 50 miles or so that were possible on one charge. Wider availability of petrol (gasoline), increasing speed and better roads made longer distances with combustion engines possible. At the same time prices dropped continuously, helped by rationalisation of manufacturing processes. The electric car could not keep up with its fossil fuel brethren. The technology stagnated while the hydrocarbon competition accelerated away.

Now the situation is different. EVs offer the chance of pollution-free travel and their capabilities have improved enormously. In a world that is far more environmentally aware, that counts for a lot. So what are the choices?

Electric Propulsion Concepts

There are three main concepts in use today:

  • Hybrid
  • Full electric
  • Fuel cell

The Hybrid

Most commonly this is a combination of combustion engine, electric engine and battery. There are also fuel cell hybrids (see below).

Hybrid engines come in various arrangements. They can be set up so there is only a small electric motor that provides power when accelerating away from standstill, whereas the combustion engine is used for most other situations and as a generator for recharging the battery. They can provide motive power individually or together (parallel hybrid). An example would be the Honda Insight.

Taking this a step further is the combination, where the proportion of work taken over by the engine or the electric motor can vary (power-split or series-parallel hybrid). Both can be used as the sole driver but any level of sharing is possible in between (e.g., 60/40). Here the electric motor can take on different roles depending on requirements. It can provide the principle power source, add a boost for accelerating on the open road or recharge the battery. The Toyota Prius is equipped with this arrangement.

Alternatively, the electric motor can be the main power source constantly. The combustion engine is principly used to recharge the battery (series hybrid). This is a system that has been in use for decades on ships and in diesel-electric locomotives. In cars it is fairly new and they are often referred to as Range Extended Electric Vehicles. Several companies, such as Volvo, Chevrolet and Ricardo, are working on models (late 2011) that should come to the market soon. The main advantage over rivals often cited is the ability to generate their own energy. Consequently, they are not only potentially very efficient and frugal but can cover a fair distance as well.

Hybrid engine setup
All these variants have in common that they are controlled by sophisticated engine management systems. These allow an optimised combined effect of the individual components for increased range, battery life and efficiency. Also, almost all make use of stop-start functions that shut down the combustion engine at standstill in order to reduce fuel consumption and emissions. If the driver wishes to move off, for example at a traffic light, the system restarts the engine as soon as necessary (parallel and series-parallel/power-split hybrids).

The battery can receive an extra boost by recovering brake energy. Like any other object, a car in motion possesses kinetic energy. When we decelerate by braking that is converted in large parts into heat. In other words discs, pads, etc. become hot. However, in a modern electric car, no matter whether it is a hybrid, a full EV or a fuel cell vehicle, this energy can by recovered and put back into the battery, topping up the charge.

Lastly, plug-in hybrids are versions as described above but their batteries can be charged from the mains or another external power source.

Full Electric

As the name suggests, there is no combustion engine involved. All power is provided by a battery together with one or more electric engines. Like for the plug-in hybrid charging makes an external source necessary. In the past the disadvantages of fully electric vehicles were their limited range, high weight because of the batteries and often hideous design. The latter might sound trivial when trying to save the planet but when it comes to selling such cars to the masses it is an important factor.

Both engineers and stylists have progressed considerably over the past ten years or so. Good examples are the models offered by American manufacturer Tesla. Their roadster changed many perceptions of electric cars. The latest introduction, the Model S, is a modern saloon with an impressive performance. The maximum range, depending on the power pack installed is 300 miles (480 km) and acceleration is more than respectable at 5.6 seconds from 0 to 60 miles per hour (96 km/h).

The main limiting element is the batteries. Technology here has made rather small steps over the years. If batteries need to be replaced the costs can run into five-figure-sums. However, how much progress has been made, can be deduced from the fact that a number of manufacturers give warranties of eight and more years or up to 100,000 miles (160,000 km)

Fuel Cell

A fuel cell generates an electric current that can provide the power for a motor. To do that it needs a fuel, which is most often Hydrogen.

 

Fuell Cell Diagram

At the anode a catalyst helps to seperate electrons from a Hydrogen atoms. They can travel along a separate path to the user. Meanwhile the positively charged Hydrogen ions make their way through a medium towards the cathode. Oxygen enters the cell and combines with the Hydrogen ions plus the electrons that have completed the circuit. The result is water.

If this could be perfected it would be a fantastic solution but there are problems. For a start the fuel needs to be stored inside the car safely. Hydrogen and oxygen literally make explosive partners. Also, hydrogen is not existent freely on Earth but mostly bound in water. The main sources are still fossil fuels. Another method is hydrolysis (the splitting of water) but that requires high amounts of , still mostly non-renewable, energy. Therefore, their clean, green credentials are questionable. However, it should be pointed out that work on other supplies and methods is being driven forward, for example bio fuels (bio gas) as the basis in place of hydrogen or as the source of it, or using renewable energy for hydrolysis.

At present, instead of providing a direct power supply that goes straight to the motor fuel cell cars are usually hybrids. The generated energy is used to charge the battery (see also the first comment in Part Two)

What Next?

In Part Two I will explore the current development status of the individual systems, the question whether EVs are actually environmentally friendly and introduce some cars you can buy in 2011/2012.

Until then I sign off by wishing you success and good health. See you next week.

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Electric cars are much more energy efficient compared to traditional gasoline cars. Electric cars offer a real opportunity to reduce the carbon output of the transport sector, as they emit zero exhaust pipe emissions.

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