Electric Cars

What would the cars run on if one day the fuels that we’ve been lavishing on for so long just disappeared? Earth had once been a planet replete with stockpiles of consumable fossil fuels like coal and petroleum. But as mankind progressed and advanced its appetite for energy shot up to humungous proportions and in much less than three centuries since the Industrial revolution, there is an outcry to conserve these natural resources and look for alternatives.

Fig. 1: A Representational Image of an Electric Car

The fragile ecology of the earth is gravely in danger due to the side effects of such rampant use of these depleting resources. Of all the industries that would directly or indirectly hit the consumers if these fuels disappeared from earth, the most obvious would be the automobile industry. To offer a viable solution to these dilemmas, many innovations in the field of automobile industry have taken place from time to time. One of them is ‘electric cars’, a solution for a cleaner and healthier tomorrow.

History

An electric car is an automobile run by electric motors which derive their energy from batteries. It is a subset of ‘Electric Vehicles’ and generally refers to vehicles running on the road only (others might be trains and boats). These were popular in late 19^th century and early 20^th century before people lost interest in them owing to rapid advances in the internal combustion engine technology. The origins of electric car date back to the second quarter of the 19^th century when Robert Anderson invented the first crude electric carriage. Thomas Davenport is credited with building the first electric vehicle in the form of a small locomotive. By the turn of the century, cars with three variants, steam, electric and gasoline were available out of which electric cars had the highest market share. It was a time when cars were used only for short distance travel. But then, due to increased interest in IC engine based automobiles, electric cars almost disappeared by 1935.

The 1960s and 70s witnessed a short revival of interest in electric car technology due to the need for alternative-fuel vehicles to reduce exhaust emissions of IC engines. Companies like Battronic Truck Company, General Electric, Sebring-Vanguard and Elcar Corp., American Motor Company etc. cashed on this need to roll out electric cars and vehicles. Last decade of the millennium saw renewed interest in electric cars when many nations took several legislative and regulatory actions like emission level regulations, Clean Air Act Amendment (US) etc. which worked in favor of electric car technology. Some vehicles from this era are the Chevrolet S-10, Geo Metro, Ford Ranger pickup, General Motors EV1 etc. It is working something like the fashion industry, old fashion being brought back in new clothes and fad.

Structure of Electric Cars

Electric vehicles are one of the simplest forms of self propelled mechanical transport. In the basic design, the drive train of the car is made up of a battery array connected to an electric motor via a switch. The amount of electricity that is allowed to pass through to the electric motor and gear systems is controlled such that the electric motor drives the wheels in the most efficient manner. Thus, the key elements that differentiate an electric car from other cars and also form the heart and core of this type are:

1. Electric Motor: The car may run on AC or DC motors. If it uses a DC motor, the car may run on any voltage between 96V and 192V of the rating around 20kW. Motors work on the principle of electromagnetic induction where change in magnetic flux causes the central shaft to rotate. DC motors can be overdriven at a value much greater than the normal operating point thus offering short burst of increased horsepower. Overdriving for longer spells lead to overheating of the motor to a point where it may be destroyed. In case of AC motors, 3 phase motors are generally used which run at 220-240 Volts AC along with 300 Volt battery packs. AC motors have the ease of availability in various sizes, shapes and power ratings in contrast to DC motors and also have a ‘regenerative braking’ feature by virtue of which, the motor can act as a generator to charge the batteries while braking.

2. Motor Controller: This is the part of the system which would control the amount of current being supplied to the motor depending on amount of pressure on the accelerator pedal. The accelerator is connected to potentiometers which act as variable resistors to provide the signal on how much power to deliver. When the pressure on accelerator is zero, no power is delivered and full power is delivered when pedal has been fully pressed. In case of DC motors the controller would chop the values of DC supply voltage to obtain a current with average value that is proportional to the amount of pressure applied to the accelerator. This chopping or pulsing takes place at a rate of more than 15000 cycles per second to avoid the humming sound in the human hearing range. In case of three phase AC motors, the controllers need to create 3 pseudo sine waves by taking DV voltage from batteries and then pulsating them on and off while inverting the polarities 60 times a second. This requires 6 sets of transistors, three for the pulsing and the other 3 for inversion of the three signals. This is a little more complex than a simple DC motor controller.

3. Batteries: Batteries are the parts that hold the energy reserve for the entire car operation. These store energy in the form of chemical energy and convert them back to electrical energy when required. Despite of all the advances in technology, battery still remains the weakest link in the chain. Lead acid batteries find predominant use in today’s cars. These are heavy, bulky, take a lot of time to charge and yet have limited capacity and life. Better replacements in the form of LiMH batteries do exist, which not only double the range of cars but also have significantly longer lives, are present but at present are too expensive to invest in. Fuel Cells offer the most attractive solution to all these problems along with being environment friendly, but still need a lot of R&D before they enter the mainstream market.

Fig. 2: Block Diagram Illustrating Battery Use For Operation of an Electric Car

Electric v/s Gasoline Cars

Electric Cars v/s Gasoline Cars

In the making of an electric car, a few parts get replaced from a conventional gasoline driven car. Firstly, the internal combustion engine, which is replaced by an electric motor. It gets its power from a controller which is further connected to an array of rechargeable batteries. On a higher level of abstraction, a gasoline car might look like a plumbing project with fuel lines, exhaust pipes, hoses etc. while an electric car may look more like a wiring project. The difference in sound levels might be oblivious to a person standing outside, but the one sitting inside would notice that the electric car is almost silent, even while running. The electric parts are supplemented by little changes of the car like the fuel gauge being replaced by a voltmeter, the engine vacuum used in power brakes being replaced by a vacuum pump, the manual transmission being replaced by a switch etc. Though these designs may vary from vendor to vendor and car to car, the first three parts discussed are essential to any electric car. Apart from these, there are a few subtle differences which can be drawn as in the figure below.

A Diagram Highlighting Prominent Differences Between Electric and Gasoline Cars

Fig. 3: A Diagram Highlighting Prominent Differences Between Electric and Gasoline Cars

Comparing the two solely on initial pricing would always give gasoline cars an upper hand. On closely seeing the performance of electric cars, it is observed that they offer an advantage of up to 30% on each kilometer driven. And each battery pack which usually lasts around 2 to 3 years is capable of running 25,000 kilometers.

Benefits

Benefits

These also have many potential benefits. First and foremost is the reduction in the emission levels of the car. Pollution has been a bane, adversely affecting ecology as well as making it uncomfortable for everyone who has to live with it. Through almost zero tailpipe emissions, green house gas release into the atmosphere is reduced. Along with it, the dependence of any country going for electric cars reduces its dependency on foreign nations for its fuel supply which directly affects the state of economy. Moreover, electric motors have relatively high conversion efficiencies of up to 75%as compared to IC engines which convert only 20% of gasoline energy at maximum.

Despite of the promise of greener pastures by the electric car, it is yet to enter the automobile mainstream. It faces several hurdles and limitations in being adopted by all and sundry. First factor that backs people off such an alternative is the initial cost of car. The main component of this cost is the battery pack. With mass production, it is expected that the rates will decline. But investments on expectations are highly risky and not many people want to take such a leap of faith. Other factors are the lack of public infrastructure to overcome the ‘range anxiety’, where a driver fears that the battery might just run out before reaching home and there is no charging point around. Most of the electric vehicles are not capable of high speeds.

As of 2011, there are only a few highway-capable models available in the market. Electric cars are aimed at reducing the use of fossil fuels. But this makes us think that where does the energy to produce electricity come from? Many power plants still rely on fossil fuels to operate their boilers. Thus complete migration would only be possible only when there is a huge investment to replace the existing infrastructure and its dependence on fossil fuels. Most people would be plugging in their cars to recharge at night when it is not in use. This could also cause potential load problems on the electric grid. Also, the batteries would charge using the conventional 220V sockets and hence would take all the more time to recharge. A possible solution to this would be to have a smart energy plan where the charging would be done on ‘Level 2’ 240 Volts charger rather than the conventional 120 V chargers, reducing charging time and for this, a large load would be given to the grid. Fuel cells offer much promise on many fronts like weight reduction, increased battery performance and life, capacity etc. and are an area of active research. Hydrogen as a fuel would reduce the harmful emissions to zero and is quite abundant.

Current Scenario

Current Scenario

Several countries like US, UK and China have pledged federal grants for electric cars and batteries to hasten up the process. Local governments offer tax credits, subsidies and incentives to reduce the purchase price of electric cars. Many European Union member states provide tax reductions and exemptions for people going in for purchasing electric cars. Many companies like America Electric, Commuter Cars, ElBil Norge, Fly Bo, Global Electric Motorcars (GEM), Modec, REVA etc. have been rolling out various electric car models. The influence has been such that even IC engine car manufacturers have started to manufacture electric car variants. Some of the common names are Toyota, Hyundai, Mahindra, Honda, Chevrolet, Nissan etc.

Despite of all the marketing strategies and all the push being given by the governments to popularize electric cars among the people, not everybody understands the importance of switching over to alternative energy solutions right now. And the scenario is expected to remain so until the manufacturing cost is brought down and the performance is brought up to the level where they can directly compete with the gasoline cars and outdo them. This all rounds up again to the weakest link in the electric car manufacture chain, the batteries. But we’ll need to understand the need, if not for us, then for the generations to come. Electric car is one such investment!