Evolution of Hybrid Cars

1. Introduction:

The European government is trying to explore market and infrastructure issues related to an innovative, narrow-lane commuter car under development by a major auto manufacturer. In sufficient numbers, this vehicle offers an opportunity to increase the capacity of the existing transportation infrastructure, reduce the state’s dependence on petroleum and lower emissions of air pollutants.

The commuter car is an innovative vehicle concept that is comparable to a motorcycle in size but offers advantages similar to an automobile in comfort, utility and safety. Depending upon the customer requirements a commuter car can be designed either a three-wheel or four-wheel. Passenger emenities similar to those available in standard automobiles, including climate control systems high quality stereo systems, and passenger restraint devices, would be available as options in this commuter car. This car offers several advantages that are inherent in the design.

This report presents the product specifications which are going to be designed through different software’s, material selection and the market research analysis.

2. Evolution of Hybrid Cars:

A hybrid automobile is a means of transportation employing two power sources; it uses a Re-chargeable energy storage system found on board and a fuelled power source as the vehicle’s ambition. The hybrid car pollutes much less and uses not as much fuel.

Back in 1899, Ferdinand Porsche have developed and led the way to the initial working hybrid-electric vehicle. On the other hand, there was no key vehicle manufacturer who invested in the hybrid idea and mass produced hybrid cars until the late twentieth century. The hybrid technology was mainly utilized in developing diesel-electric submarines in the course of that interim period. Yet, the submarines major objective was to conserve oxygen as opposed to spend less fuel. Throughout the later years, submarines have evolved and have begun using the nuclear power as an alternative for diesel.

During the 1990’s, the Toyota Prius plus the Honda Insight were the very first profitable hybrid cars available in the market. It was two of the pioneers inside the hybrid auto idea which virtually adjusted the way the world considers cars. An idealistic inventor, Victor Wouk, manufactured a hybrid electric and gas car that siphoned fuel at half the quantity as practically all the other cars becoming built then. He built the hybrid car thirty years before the Toyota Prius got the attention of the U.S. as an energy- uneasy nation. And now the striking capabilities of the creation of Wouk, the hybrid cars, are now able to be an incredibly great support relating to less gas ingestion and less air pollution. Wouk and Rosen put up a start up business particularly to develop their hybrid car thought and made it easy to be on the market and be utilized as a regular automobile that belched less harmful vapors than up-to-date vehicles.

The Prius Ever since the Toyota Prius, fuel efficient car was released on the market; it has been able to remain as the premier option of hybrid cars available. It is a fact that old hybrid cars looks more like an alien automobile and cost much more than the conventional car. Yet, because of the most up-to-date technologies installed in newer versions of hybrid cars, it looks extra like a conventional car and is far less expensive than its predecessors. It is a fact that hybrid cars these days look a whole lot like conventional cars. The Civic Hybrid can get 50 miles in mere 1 gallon of gasoline.

During the year 2004, Ford has developed and introduced the initial hybrid SUV that is the Ford Escape Hybrid. A year later, Toyota also introduced their line of hybrid SUV called the Highlander Hybrid. Because of the increasing requirement for hybrid cars, other auto manufacturers are now following the footsteps of the other companies who already brought out a version of their hybrid car on the market. As an example, Nissan is now going to develop and introduce a hybrid version of the Nissan Altima. Presently, over 300,000 hybrid cars are running on American roads wherein 95 percent of them are Japanese made. The hybrid vehicles are really quite distinct technologies that can both reduce financial outlay and our environment.

3. WORKING PRINCIPLE OF HYBRID CARS:

A hybrid is anything that uses two or more sources directly or indirectly to provide propulsion. Two power sources set up in a hybrid car in different ways. It has a fuel tank, which supplies gasoline to the engine and set of batteries that supplies power to an electric motor. The engine and the electric motor together can turn the transmission at identical time, and the transmission then turns the road wheels as shown in the figure1.

The different ways in which the power sources establish in car are describe as follows:

1. Series Hybrid Cars.
2. Parallel Hybrid Cars.
3. Series-Parallel Cars.

3.1 Series Hybrid Cars:

The simplest of hybrid configuration is the Series Hybrid Car. In a series hybrid, the electric motor is the only resource of providing power to get wheels turning. The motor receives electric power from either the battery pack or from a generator run by a gasoline engine. The Battery pack is recharged by both the engine/generator and regenerative braking. The engine in a series drive train is typically smaller because it only meets the average driving power demands. The battery pack in these Hybrid cars generally more powerful than the one in parallel hybrid providing remaining peak driving power needs. Series hybrids are more expensive than parallel hybrids as the larger battery and motor with the generator add to the cost.

While the engine in a conventional vehicle is forced to operate inefficiently to satisfy varying power demands of stop-and-go driving, series hybrids perform at their best in such conditions, as the gasoline engine in a series hybrid is not coupled to the wheels. This means the engine is no longer subject to the widely varying power demands experienced in stop-and-go driving and can instead operate in a narrow power range at near optimum efficiency , which eliminates the need for a complicated multi-speed transmission and clutch. Because series drive trains perform best in stop-and-go driving are primarily being considered for buses and other urban work vehicles. The figure below shows the process of series hybrid car

3.2 Parallel Hybrid Car:

In parallel hybrid electric vehicle, the wheels are driven by the power generated from both the engine and the electric motor. The addition of computer controls and a transmission allow these components to work together. Parallel hybrids use a smaller battery pack and mainly depend on regenerative braking to keep it recharged. However, when power demands are low, parallel hybrids also utilize the drive motor as a generator for supplemental recharging, same as that of an alternator in conventional cars.

In this setup the wheels are directly connected to the engine, which eliminates the inefficiency of converting mechanical power to electricity and back, which makes these hybrids quite efficient on the highway. The same direct connection between the engine and the wheels that increases highway efficiency compared to a series hybrid does reduce, but not eliminate, the city driving efficiency benefits. The figure below shows the process of parallel hybrid cars

3.3 Series-Parallel Hybrid Car:

This drive train merges the advantages and complications of the parallel and series drive trains. As a result of combining the two designs, the engine can both drive the wheels directly (as in the parallel drive train) and be effectively disconnected from the wheels so that only the electric motor powers the wheels (as in the series drive train). Therefore, the engine operates at near optimum efficiency more often because of this dual drive train. At lower speeds it operates more as a series vehicle, while at high speeds, where the series drive train is less efficient, the engine takes over and energy loss is minimized. This system is expensive than that of a pure parallel hybrid since it needs a generator, a larger battery pack, and more computing power to control the dual system. However, the series/parallel drive train has the potential to perform better than either of the systems alone. The figure below shows the series-parallel hybrid process.

4. Project Planning:

As can be seen in figure 4, the project plan includes the timescale of the project as a whole, from the beginning to the end. It outlines the various stages of the project highlighting the objectives and deliverables of each part of the project. It also defines the deadlines of each stage so as to assure that the project runs as per the schedule desired. However, it has to be taken into account that all the real world situations cannot be accounted for and hence, a safety period of appropriate measure has to be incorporated into each stage or at the end of the project. This assures that the deadlines will be met even in the event of unforeseeable circumstances.

The project plan in itself is not a sufficient tool to manage a project of this magnitude. Hence, various other management tools were used during the course of this project to facilitate in the timely completion and effective management of the time and resources available to the team as a whole as well as, as individuals. These management tools include Gantt chart, Quality Function Deployment (QFD), Critical Path Analysis (CPA), Program Evaluation and Review (PERT), SWOT Analysis etc.

4.1 GANTT CHART:

Gantt chart is a bar chart known after Henry Gantt who designed his chart in the beginning of 20th century. It shows a very clear and easily explicable manner of the project structure in terms of time and individual tasks and subtasks. The project time schedule was visualized and optimized using Gantt chart.

In this case, the CHV project was divided into eleven main tasks: 1. market research, 2. technical research, 3. target setting, 4. concept development, 5. concept finalization, 6. further concept development, 7. management analysis and 8. Report. These tasks, in certain cases, are subdivided into subtasks, usually assigned to a particular group member responsible for that part. Name(s) of the member(s) working on an individual task are written near the blue bar, which represents the time duration of the task. The project Gantt Chart is shown in APPENDIX-1:

4.2 Critical Path Analysis:

Critical Path Analysis (CPA) is a management tool that analyzes all the tasks required for completing the project, paying specific attention to the time required for the completion of each activity. It is used to formulate, schedule and manage the various milestones or activities in the project. It was developed in the 1950’s to control large defiance projects and have been used routinely from then (mindtools.com).The critical path analysis for the CHV project was useful in:-

1. Identifying all major activities requiring time.
2. Time required for each activity was estimated and the overall project plan.
3. Logical sequencing of these activities.

For drawing the CPA first step was listing out the major activity. The next step is to sequence the activities into a logical order based on when it must or is most likely to occur i.e. certain activities will logically proceed after an activity while certain activities will be taking place parallel to each other. After sequencing, the time period required to complete each activity was determined. Time is represented in most networks as days. The time period for each activity was calculated taking into account the suggestions made by group members and considering other factors such as how many people will be working on each task, how many working days etc. As can be seen in Table 1, the findings are recorded in table format for easy look. The table also records the sequence of the activities as series, meaning occurs after another activity, and parallel, meaning occurring along with another activity. The dependence of an activity is also mentioned in the table.

Table1:

From the table 1 below, a chart is drawn in Figure 5 which represents the activities in circles and the time taken to complete an activity is stated on the arrow joining two activities.

From the above CPA this project requires 62 minimum numbers of days for the completion of the project.

4.3 SWOT ANALYSIS

SWOT analysis is a planning method that analysis the strengths, weakness, opportunities and threats for a project. SWOT is a model that helps in assessment of a firm of what it can and cannot do along with the potential opportunities and threats. In SWOT analysis the information is separated into internal and external issues and each issue is addressed. SWOT analysis is useful in helping the group in meeting its objectives and also the obstacles to overcome to meet the desired result. The SWOT analysis carried out by the group is shown below, in APPENDIX-2..

The analysis was done, the strength and weakness of the group were put down along with its opportunities available for CHV was discussed and the barriers which could prove serious for the CHV project were taken into consideration . The ways to minimize the threats were also discussed with the help of group..

4.4 3P’s:

Similar as other analysis techniques such as QFD or DFMEA, 3Ps is a management aiding method designed to help designers make better plans. The major function of 3Ps is to find disadvantages faced during a specific time for the period of the project, then to workout them. So 3P is the combination of Progress against Plan, Problems with the Progress and Plan to solve Problems.

All team members knew the weakness of this project by making 3Ps and the main problems in it have to be solved. It is very useful method because it shows the current conditions of the project; especially the direction designers should pay more concentration. The disadvantage of the project is known at the beginning and makes people think about it.

5. Market research:

The first step of the project, as per the Gantt chart and the project planning was market research. This includes researching on the current vehicles that are available in the market and are due to be available within the next 3-6 months. Also to be considered is the market evaluation i.e. what types of vehicles are the customers most inclined to buy and what is the most desirable from CVs.

As the project specification includes that the vehicle is to be a family hatchback powered by an electric battery and IC engine, the “Chevrolet Volt” or the “Honda Insight” cars were taken as bench marking. The market research results are shown in Table 5.

5.1 Comparison of vehicles using different sources as energy:

l. Petrol car: A journey of 68 miles each day consumes 2.5 gallons of fuel and takes 2 hours.

Amount of energy in fuel = 5.14 x 108 joules

Thermal power = 71.3 kW

Mechanical power = 20 kW average

Efficiency = 28%

2. Battery electric car as secondary transport.

Power station efficiency 40%

Electric car efficiency 80%

OVERALL 32%

CONCLUSION: Pollution is moved from car to power station. There is only an environmental return if the car’s performance is sacrificed or the power station is non-thermal and range/performance is limited.

3. Fuel-cell electric car as primary transport.

Hydrocarbon to hydrogen conversion 75%

Fuel-cell hydrogen to electricity 58%

Electricity to mechanical power 87%

OVERALL 38% (potential for 41% in 10 years)

CONCLUSION: Pollution reduced by 88%; fuel consumption is 60% of petrol vehicle and

Performance /range are as petrol vehicle.

4. Hybrid car as primary transport.

Hydrocarbon to electricity

Via lean burn petrol engine 45%

Electricity to mechanical power 90%

OVERALL 40.5%

CONCLUSION: Pollution reduced by 70% and fuel consumption is 70% of petrol vehicle with performance/range as the petrol vehicle.

So from the above comparison Hybrid car is the best transport CV which reduces the pollution and fuel consumption with good performance.

6. Technical Research:

The next step is the technical research. It includes researching the technologies currently available in the market for the major components of the CHV. The major components of the CHV were divided into several components as below

• Batteries.
• Motors and Controllers.
• Aerodynamic.
• Regenerative braking.
• IC Engine.
• Transmission and
• Safety and homologation.

6.1 BATTERIES:

The battery package is an essential element of an electric vehicle. Its electrical properties determines the vehicle driving range, while its physical properties must be consider during suspension design, vehicle architecture, etc. According to Larminie and Lowry (2003), batteries are the component with highest cost, weight and volume.

Generally, a battery consists of two or more electric cells, which are joined together and generate DC electricity. There are several parameters describing the properties of a battery such as internal resistance, charge capacity, energy stored [Wh] or specific energy [Wh.kg-1]. Service temperature is a very important factor influencing the battery performance.

Several different types of batteries were identified during research (Larminie and Lowry 2003):

Lead-acid batteries:

This is widely used with main constituents – lead, sulphuric acid, plastic container which are available at low cost. However, lead acid batteries have a very low specific energy. Therefore, a battery with sufficient capacity using this technology would be very heavy. As a result, lead acid batteries are used in low-cost and low-range electric vehicles.

Nickel-cadmium batteries:

These batteries have a specific energy nearly twice that of lead-acid batteries. They possess a low self-discharge capability and are able to work in wide range of temperature (-40°C to 80°C). The presence cadmium is considered as a major drawback. Nickel-cadmium (NiCd) batteries were used in electric cars.

Nickel-metal hydride batteries:

As of the abbreviation NiMH, these are used in hybrid vehicles. The main principle is as like that of nickel-cadmium batteries, but the negative electrode uses hydrogen absorbed in metal hydride instead of cadmium. In addition NiMH batteries have higher specific energy. But, their self-discharge rate is relatively high which is ten times to that of NiCd. Since the reaction running in the battery is exothermic, a NiMH battery package must be cooled.

Sodium-based batteries:

In spite of high specific energy, sodium-based batteries have serious disadvantages that exclude it from commercial use of hybrid vehicle. Its operating temperature lies in the range of 300-350°C. Once the battery is cooled down, it must be slowly reheated before operation and this process can take up to 24 hours. Besides, keeping the battery at its required temperature requires approximately 100 W of power.

Lithium batteries:

Lithium-ion batteries (Li-ion) are the latest stage in battery development providing the best performance for electric vehicles. They have a high specific energy and consequently a very low overall weight. This type of battery is used by the most recent electric vehicle available in the market (e.g. Nissan Leaf, Peugeot iOn, Tesla Roadster). The crucial disadvantage of Li-ion batteries is their high cost.

Table 6: Battery comparison table

Assumed input data

ICE vehicle consumption: 4 l/100 km of diesel fuel (Volkswagen 2010)

Diesel fuel specific energy: 40 kWh/kg

Diesel fuel density: 0.832 kg/l

ICE vehicle fuel → wheels efficiency: 10%

EV vehicle fuel → wheels efficiency: 70%

According to the input data, the required capacity of the battery pack is from 46 kWh to 61 kWh. According to specific energy of individual battery type the battery weight can be estimated (Table 7).

For the desired range, lead acid batteries are far too heavy to be applied in a family hatchback. However, they can be considered as a cheap alternative for a low-range electric vehicle.

Table 7:Battery Comparison according to range

According to the table above, lithium-ion batteries are the most suitable option. If the latest technology is used (Nissan Leaf’s laminated Li-Ion batteries), specific energy can reach 140 kW/h (Weissler 2010), and thus the battery weight can be further reduced. In addition to this, the latest development shows a good potential in increasing Li-ion battery performance by means of nanotechnology. Furthermore, according to various prediction e.g. by The Boston Consulting Group (2010), the battery cost are about to decrease with the increase of production volume and it can be more than 50 % in the year 2020.

6.2 MOTORS AND CONTROLLERS:

Motors is considered to be one of the main part of the electric vehicle .In a pure electric vehicle the motor provides the required torque directly to the wheels. However, the motor rotates at constant speed, so to vary the speed of the vehicle a potentiometer needs to be attached. The speed control of the vehicle is made possible by DC or AC (inverters) controllers. The accelerator pedal is attached to a potentiometer (variable resistor) which is further attached to the DC or AC controllers. The force on the accelerator pedal is directly proportional to the current delivered to the controller. Depending on the current supplied, the controller delivers power to the motor. The working of DC controller varies with an AC controller. For selecting a motor the main features that are important for an electric vehicle are good efficiency, high torque, low maintenance, moderate cost and easy to control. Figure 4 shows the basic layout of the motor and controller in an electric vehicle.

The three motors considered for the concept were:-

1. AC Synchronous Motor.
2. DC Brushless Motor
3. AC Induction Motor

AC 3 synchronous motor is the latest type of motor used in electric vehicle. The main characteristic of AC 3 synchronous motor is that the motor runs at synchronous speed i.e. the field winding locks with the rotating magnetic fields and rotates along with it. The AC 3 synchronous motors has many advantages .Usually the AC induction motor works at lagging power factor but the AC 3 synchronous motor works at leading power factor which means improved efficiency and reduction in voltage drop .Accurate speed control is possible which makes synchronous motors an ideal choice .Synchronous motors have speed/torque characteristics which are ideally suited for direct drive of loads. A smooth the torque curve results in better performance of the vehicle. It has good heat dissipation and overloading capacity .The absence of magnets also reduce the cost of maintenance. Regeneration of energy is easily possible in an AC 3 synchronous motor by reversing the current. AC 3 synchronous motors has certain disadvantages such as it is not a self starting motor i.e. a separate motor (pony motor) is required to drive it till it reaches synchronization. Since it is relatively a new technology the price of the motor is comparatively higher.

DC Brushless Motor or BLDC is the most common motor used in hybrid vehicles. A BLDC motor is similar to AC 3 synchronous motor. It has got good torque characteristics and also absence of slip. The heat dissipation and overloading characteristics is commendable for a BLDC motor. But BLDC motor is considered to be less efficient than the other three motors because of many factors. It has m