Transportation Deployment Casebook/2018/Hybrid Electric Vehicles (USA)

Qualitative AnalysisEdit


Hybrid Electric Vehicles utilises a combination of a conventional internal combustion engine propulsion system, seen in standard automobiles, with an electric propulsion system. The electric propulsion system powers the vehicles at the lower speeds and the internal combustion engine powers the vehicle at higher speeds. Thus hybrid electric vehicles not only conserves fuel but it also produces less carbon dioxide emissions. Under the category of hybrid electric vehicles, there exists the plug-in hybrid vehicle, which involves charging the vehicles battery using an external electric grid connection. The internal combustion engine provides a longer driving range while the electric propulsion system increases the vehicles fuel efficiency as energy is regenerated during braking and by storing energy from the internal combustion engine during coasting.

Components of a Hybrid Electric VehicleEdit

The energy system of a hybrid electric vehicle consists of a battery, an ultracapacitor and internal combustion engine unit. The sources of energy and infrastructure required to power a hybrid electric vehicle includes gasoline stations and electric grid charging facilities for the plug in hybrid vehicles. Key characteristics of a hybrid electric vehicle include very low emission when compared to a standard gasoline powered vehicle. Further, hybrid electric vehicles usually have higher fuel economies and longer driving ranges depending on the power level of the motor and battery as well as the driving cycle. Some of the key issues that are associated with hybrid electric vehicles stem from the battery and battery management and the high performance propulsion.

The Electric Propulsion MotorEdit

The electric propulsion motor is one of the key components and plays a vital role in a hybrid electric vehicle. There are three types of electric motors that are suitable to be used in automobiles. These are the propulsion motor brushless motor, induction motors and switched reluctance motors. Standard requirements for a motor and drive technology includes having a high torque density and high power density, having a wide speed range and high efficiency over this speed range. Further the electric propulsion motor should be very reliable and be available at a reasonable cost in order to attract customers.

Powered ConvertersEdit

Powered converters include all the typical power electronic circuits used in hybrid electric vehicles. These include the rectifiers, inverters and the direct current converters. The design of the power electronics circuits in a hybrid electric vehicle can be broken down into categories as follows:

  • The Electrical Design: The electrical design includes the main switching circuit design, the controller circuitry design, the selection to switch devices and switching frequency optimisation.
  • The Control Algorithm Design: The control algorithm design includes the design used to achieve the desired voltage, current and frequency at the output. Further, this algorithm design is used to realise the bidirectional power flow.
  • The Magnetic Design: The magnetic design includes the design of the inductors, capacitors and other magnetic components needed for functions such as filtering and switching.
  • The Mechanical and Thermal Design: The mechanical and thermal design includes the model of the loss of power devices and magnetic components in the system. It also includes the design of the cooling system, the heat sink and the integration of the power electronics unit.

Hybrid Control TechnologyEdit

Hybrid Control Technology is mainly understood through simulations performed and through past experiences. Hybrid control technology splits into two categories. The first is energy management control and the second is drivability control. Energy management control is basically the goal to optimise the energy efficiency and reduce the emission. The drivability control aimed to optimise driving performance, comfort and safety performance. Thus, control is one of the most essential components in the technology in hybrid electric vehicles.

Battery and Ultra-capacitorEdit

Battery and Ultra-capacitor is another essential component in hybrid electric vehicles. The battery and the ultra-capacitor store the energy that comes from the kinetic energy during braking or from the engine during coasting. Batteries use electrochemistry principles to store energy whereas ultra-capacitors use static electricity principles to store electric power. These components also provide the power to the propulsion system especially during times when there is a sudden power demand from the vehicle. Since the specific power of a battery or ultra-capacitor has very little specific power relative to gasoline, it is usually used together with a fuel cell to improve the starting performance of the vehicle.

Reasons for an Increase in Sales of Hybrid VehiclesEdit

Advantages of Hybrid CarsEdit

  • Environmentally Friendly: Hybrid electric vehicles runs cleaner as it switches to the electric propulsion system for power when the vehicle is moving at lower speeds. This also results in a better gas mileage, which makes the hybrid electric vehicles environmentally friendly.
  • Financial Benefits: Many governments around the world provide incentives to the manufacturers of hybrid electric vehicles to spend on research and development in order to make the vehicles cheaper and thus more affordable to the consumers. Further, some governments have lower annual tax bills and exemptions from congestion charges that all translate to less money spent on fuel and thus an added financial benefit on the users of hybrid electric vehicles.
  • Less Dependence on Fossil Fuels: A hybrid electric vehicle will require less fuel for a journey as the power system may change back and forth between the electric propulsion system and the internal combustion engine. This lower dependence on fossil fuel may also mean a lower demand for fuel and a further third party benefit that arises is that the cost of fuel also reduces.
  • Regenerative Braking System: The batter will be recharged every time the brakes are applied and from the internal combustion engine during coasting. The fact that the battery is recharged during braking eliminates the need for stopping to recharge the battery periodically.
  • Built from Light Materials: Hybrid electric vehicles are built using lighter materials compared to the conventional vehicles available in the market. This means that less energy is required to power the car, which saves fuel in terms of costs.
  • Higher Resale Value: Since there is a constant rise in global gasoline prices, more consumers prefer to purchase hybrid electric vehicles. This growing demand for hybrid electric vehicles has resulted in a higher resale value for these vehicles.

Reasons for Slow Initial Growth in Sales of Hybrid VehiclesEdit

Disadvantages of Hybrid CarsEdit

  • Less Power: Hybrid electric vehicles have twin-powered engines, the internal combustion engine and the electric propulsion system. Due to this reason, hybrid electric vehicles have much smaller gasoline engines in them than that found in a conventional gasoline powered car. Further the electric motor in the hybrid electric vehicle produces low power. Thus, the combined power of both the internal combustion engine and the electric propulsion system is usually lower than that of a car with a solely gas powered engine. Therefore, hybrid electric vehicles are more suitable for city limit driving rather than for speed and acceleration.
  • Can be Expensive: Hybrid electric vehicles are usually much more expensive than a regular petrol car unless the government subsidises the vehicle manufacturers which translates into lower prices for the consumer as well. However, the initial major cost is a one-off cost and can be recovered in the long run through the reduced fuel consumptions and tax exemptions.
  • Poorer Handling: A hybrid electric vehicle has a internal combustion engine, a lighter electric engine and a pack of large, powerful batteries. This adds up weight and uses up most storage space in the car. This additional weight results in fuel inefficiency. Thus, manufacturers have resorted to downsizing the motor and battery in order to reduce the weight. This in turn has reduced the support in the suspension and body, which results in the vehicle having poor handling.
  • Higher Maintenance Costs: The presence of dual engines and the constant improvements to the engine through research ad development makes it more difficult for mechanics to repair the car. Also, it is harder to find a mechanic with such an expertise.
  • Presence of High Voltage in Batteries: In the event if an accident, the high voltage present in the batteries can prove lethal to the passengers inside the vehicle. There is a high chance of the passengers being electrocuted and makes it harder for rescuers to get the passengers out of the car in the event of an accident.

Why do Governments Support Hybrid Electric Vehicles/ Third Party Benefits Through Hybrid Electric VehiclesEdit

The U.S government has been supporting the purchasing of hybrid electric vehicles in the forms of federal income tax deductions before 2006 and federal income tax credits since 2006. The government is interested in promoting hybrid electric vehicles due to several reasons and benefits.

  • Environmental Benefits: Some of the key factors the government takes into consideration when supporting hybrid electric vehicles is due to the reductions in environmental externalities of motor gasoline consumption and national energy interests. Automobile emissions contribute a significant amount of carbon dioxide to the atmosphere, which causes negative implications of climate change. Hybrid electric vehicles have been considered to be vital method of reducing carbon dioxide emissions, pollution and to achieve energy security. A further benefit of the hybrid electric vehicles is the fact that they use nickel metal hydride batteries, which is a more environmentally friendly option than the lead-acid batteries that it used in conventional gasoline fuelled cars.
  • Economy Benefits: Further, the government supports hybrid electric vehicles over the conventional gasoline run car due to the constantly rising fuel prices. The steep rise in fuel prices results in a loss in disposable in income in households, resulting in individuals spending less money on goods and services. This has a negative impact on the nation’s gross domestic product. The greater fuel efficiency in hybrid electric vehicles would result in the consumers relying less on fuel and thus getting affected less by the fluctuating fuel prices. This would mean that there is more money with the people to circulate through the economy.
  • Reducing Trade Deficits: The government would also promote the sale of hybrid electric vehicles due to the trade deficits caused by the oil prices. The rise in oil prices in 2008 was responsible for 75 percent of the trade deficit that the United States of America had. Thus, anything that reduces oil imports would have a positive net effect on the trade imbalance. The penetration of the hybrid electric vehicle into the market would result in a gradual reduction of oil imports.

Case Study - Toyota PriusEdit

The Toyota Prius is the world’s first commercially produced hybrid electric vehicle. It went on sale in 1997 in Japan and in 2000 in the United States. In the year 2005, a total of 100,000 units were sold in the United States, alone which resembles the quick growth of the hybrid electric vehicles. The Prius underwent several modifications and upgrades. For instance, the consumer saw the 2004 model Prius redesigned as a midsize hatchback. There were several modifications done to the electric propulsion battery component and the internal combustion engine of the Toyota Prius in the editions that followed. Currently, the Prius is on its fourth generation model. Further, the market saw hybrid versions of other Toyota vehicles such as the Camry and Corolla, which outline the success the hybrid electric vehicle had with the consumer.  

Timeline of Motor Travel and PoliciesEdit

  • 1880: Electricity was applied in transportation to the streetcar. Testing of battery trolleys took place as early as in the 1880’s in places like Philadelphia.
  • 1888: Camille Faure later wanted to adapt this knowledge for electric dynamos and then later filed for a patent for a battery-powered vehicle. The filing for patent was approved in 1888. It was realised that each additional battery added reduced the effectiveness of all the other batteries. This was due to the stored energy being used to move around other batteries instead of the car and passengers in it. Thus, diminishing returns set in. At that time people imagined of travelling 100 miles a day. This was something an electric powered vehicle could not do. Other problems that led to the electric car being unsuccessful were the lack of charging stations and the underdeveloped grid. The plug to connect the car battery to the wall was not developed till 1901. Before this invention, the car batteries had to be removed as a whole and be replaced again once charged. Furthermore to make matters worse the range with an electric battery was roughly around four hours, so charging was done frequently.
  • 1901-1905: In 1901 Ferdinand Porsche built a hybrid car. The hybrid cars developed at the time were able to switch between using electric or gasoline power. This specific vehicle used an internal combustion engine to spin a generator that provided power to the electric motors located in the wheel hubs. Surprisingly, the vehicle could travel 40 miles on the power supplied from the battery alone. Following Ferdinand Porsche, in 1905, the Fischer Motor Vehicle Company developed an early gas-electric hybrid vehicle, which used an electric starter. Whenever there was an overload on the gasoline engine, the battery power was utilized. A patent for a petrol-electric hybrid vehicle was filed in the U.S.
  • 1904: In 1904 Henry Ford overcame the challenges that were an obstruction with gasoline-powered cars. He fixed issues with the noise, odour and colour of the car and began assembly line production of lightweight, cheap gas powered vehicles.
  • 1913: With self starters on the gasoline-fuelled vehicles, the demand for electric vehicles drop exponentially as consumers now prefer gasoline cars as it’s easier to start. The sales of electric cars dropped to 6000 vehicles whereas the Ford Model T sold 182,809 units.
  • 1966: The U.S congress introduced the first Acts to encourage the use of electric vehicles as a means of reducing air pollution and protecting the environment.
  • 1970’s: The Arab oil embargo of 1973 resulted in a steep rise in the price of fuel. This created an interest towards electric vehicles.
  • 1975: The U.S Energy and Research Development Administration began a government program to improve electric and hybrid technology.
  • 1976: The U.S Congress introduced the Electric and Hybrid Vehicle Research, Development and Demonstration Act. The aims of the law were to work with industry to improve batteries, motors and other hybrid-electric components.
  • 1977-1979: General Motors spent over 20 million dollars in electric car research and development.
  • 1997-2000: In 1997 the Toyota Prius went on sale in Japan, in 2000 the Prius went on sale in the United States following the Honda Insight in 1999.   

Birth PhaseEdit

Both the time period the hybrid electric car was invented and the inventor of the hybrid electric vehicle is unclear. Instead it was a series of innovation and transfer of knowledge from batteries to the electric motor that led to the first electric vehicle and then the first hybrid electric vehicle in the world. In the United States, William Morrison introduced the first electric car around 1890. His passenger vehicle was able to reach a maximum speed of 14 miles per hour, which was slightly faster than the first electric car but it served a inspiration for the first electric vehicle.

Over the following years, there were several electric vehicles entering the market from different automakers. By 19000, the first wave of electric cars reached its peak as it accounted for one third of the vehicles on the road. This success continued to show in the next decade through the strong sales values.

Early Market DevelopmentEdit

Although electric cars were available in the 1900’s, the horse remained the primary mode of transportation. However, as Americans were becoming richer and as the economy was improving, people started using the newly invented motor vehicle available with steam, gasoline and electric engines.

Steam technology in transportation modes was proved to be reliable through its success in transport modes such as trains. However, it was not until the 1870’s that this steam technology was adapted in cars. This was since steam was not practical for personal vehicles as it required long startup times and would need to be frequently refilled with water, which limited their range.

The gasoline-powered car accompanied the entrance of the electric car into the market. This was due to the improvements to the internal combustion engine in the 1800’s. Initially the consumer preferred the electric car to the gasoline car due to several reasons. There were faults with the gasoline car such as it requiring a lot of manual effort to drive when changing gears. Further, gasoline cars were noisy and their exhaust was unpleasant. On the other hand, electric cars were quiet, easy to drive and did not emit unpleasant pollutants like its rival cars. As more people gained access to electricity in the 1910’s, charging of electric cars became easier. This led to electric cars becoming more popular amongst consumers.

Many innovators such as Ferdinand Porsche worked on ways to improve the electric cars. He managed to develop an electric car in 1898 and was able to create the world’s first hybrid electric vehicle at around the same time. Further innovators such as Henry Ford and Thomas Edison worked together to develop low cost electric cars in 1914.

It was Henry Ford’s mass-produced Model T that affected the sales of the electric cars. The introduction of the Model T in 1908, made the gasoline powered cars widely available through the low prices achieved by producing the cars at low cost by using assembly lines. The Model T was being sold for less than half the price of an electric car at that time.

Other factors such as the development of the transportation road networks and the wants of the people to travel further distances coupled with the readily available cheap gas had a negative impact on the sales of electric cars.

Growth PhaseEdit

Due to the great success of the gasoline-powered vehicles, the development of the electric cars was stagnant with little sales. The success of the gasoline-powered vehicle stemmed from improvement of the internal combustion engine and the cheap and freely availability of gasoline.

However, overtime the price of gasoline was rising steeply. The soaring oil prices and gasoline shortages in the early 1970’s led to the United States incentive to depend less on foreign oil and finding domestic sources of fuel. Following the interest, the Congress passed the Electric and Hybrid Vehicle Research, Development and Demonstration Act of 1976. This Act passed was to ensure the Energy Department showed interest and support towards research and development in electric and hybrid vehicles.

Even though the automobile manufacturers had the facilities and resources for research and development they were unable to produce a sufficient electric or hybrid electric vehicle to compete with the gasoline-powered vehicle. Electric vehicles produced had a top speed of 45 miles per hour and the vehicles had a range of only 40 miles before having to be recharged again.

Environmental Concerns Raise Demands for Electric and Hybrid VehiclesEdit

The focus towards environment protection and preservation increased form the 1990’s onwards. As a result the interest in electric and hybrid vehicles started to revive during this time period. The government passed the 1990 Clean Air Act Amendment and the 1992 Energy Policy Act to help initiate the renewed interest in electric and hybrid cars. As a result of this, automobile manufacturers began upgrading their popular models into hybrid vehicles. This enabled the hybrid electric vehicles to now achieve speeds much closer to gasoline-powered vehicles and also have an improved driving range of 60 miles from solely the battery.

Unfortunately, although the government had concerns about the damage caused to the environment through the harmful gases released by gasoline-powered vehicles, the economy seemed to be booming. Thus more people had more money and the demand for vehicles started to rise. Since, the economy was booming, individuals did not worry about fuel-efficient cars and therefore did not consume fuel-efficient cars.

A New Beginning for Electric CarsEdit

The true revival of the hybrid electric vehicle surfaced in the 21st century. One of the major milestones was the introduction of the Toyota Prius. It was released in Japan in 1997 and in the United States in 2000. It was the world’s first mass-produced hybrid electric vehicle. Toyota was able to successfully capture a significant market share through its hybrid electric vehicles by spreading awareness about carbon pollution. Further rising global gasoline prices also encouraged people to turn towards hybrid electric vehicles, which were fuel-efficient.

Another major event that highlighted the presence of electric cars was the announcement of Tesla Motors in 2006. At the time, Tesla Motors claimed to start producing a luxury electric sports car that could go north of a 200 miles on a single charge. This announcement coupled with subsequent successes motivated other big automobile manufacturers to accelerate their work on hybrid electric vehicles. In 2010 the Chevrolet Volt and the Nissan Leaf were released in the U.S market. The Chevrolet Volt was the first plug-in hybrid that ran completely on the battery till it depleted and then would switch to its gasoline engine in order to increase the range.

Over the next few years, majority of the major automobile manufacturers began rolling out hybrid electric vehicles in the U.S market. However, the consumers were faced with the issue of where they were going to charge their plug-in hybrid vehicles. To combat this the Energy Department introduced the Recovery Act in which they invested 115 million dollars to help build a nation-wide charging infrastructure. This program installed more than 18000 public chargers across the country. Automakers also installed their own charges in vital locations across the U.S, which increased the total number of charging outlets to 20000.

With the aid of the Energy Departments Technology Office, the technology of the batteries used was developed. The improvements in the battery have enabled the manufacturers to produce them at lower costs and thus the price of the vehicles has reduced making it more affordable for consumers.

Today consumers have a vast variety of choices of hybrid electric cars available in the market. There are 23 plug-in hybrid models and a further 36 hybrid electric models. These vehicles range from the Toyota Prius and Honda Insight to the luxury BMW i8.

Projection of Hybrid Electric CarsEdit

The constant development of hybrid electric cars would guarantee a sustainable future if the demand for hybrid electric cars remain. According to the data analysed there is a drop kin demand for hybrid electric cars. Since the current global oil prices are rising, consumers most probably are not switching to gasoline-fuelled vehicles.

Quantitative AnalysisEdit

The S-CurveEdit

The S-Curve identifies the birth phase, the growth phase and the maturity phase for the sales of hybrid electric vehicles. Graph 1 illustrates the number of vehicle sales over the years of the birthing, growth and maturity stages of the lifecycle. Since the actual sales of hybrid electric vehicles is portrayed by a somewhat noisier observation as seen by the curve in Graph 1, we fit a smoother curve of the predicted hybrid electric vehicles in order to understand the data and results in more depth.

The data was obtained from The U.S Department of Transportation, Bureau of Transportation Statistics. Therefore the data integrity is not lost and the reliability of the data obtained is very high.


The data was used to estimate a three-parameter logistic function:

S (t)=K/[1+exp (-b (t-t0))]


  • S (t) is the status measure (number of hybrid electric vehicle sales)
  • t is the time in years
  • t0 is the inflection time
  • K is the saturation status level
  • b is a coefficient
Graph 1


Year Vehicle Sales Predicted Vehicle Sales
1999 17 3310
2000 9350 5612
2001 20282 9487
2002 36035 15950
2003 47600 26578
2004 84199 43653
2005 209711 70082
2006 252636 108720
2007 352274 160735
2008 312386 223504
2009 290271 289974
2010 274210 351299
2011 268807 401091
2012 434344 437489
2013 495534 462104
2014 443823 477887
2015 384404 487664
Variable Value
K 502268.228
b 0.532749435
tnought 2008.414706
R Squared 0.702055575

Accuracy and ReliabilityEdit

K was estimated to be 502268.228 according to the data gathered. The K value of 502268.228 represents the hybrid electric vehicle market maturing in 2008 with a vehicle sale value of 312386. From 2008 onwards the sales of hybrid electric vehicles still continues to increase but at decreasing rate. The fact that the vehicle sales for hybrid electric vehicles were at its highest at 2013 and then declined from that point onwards suggest that the market may be facing difficulties due to fluctuations in fuel prices. However, there may be another argument to this aforementioned point. The sales in hybrid electric vehicles may have reduced by a small proportion due to the introduction of plug-in hybrid vehicle models. The increase and decrease in demand of the hybrid electric vehicle is mainly influenced by the prices of fuel and the status of the economy. If the economy is thriving, more people will have disposable income, which would mean that they would have more money to spend on hybrid electric vehicles and vice versa. Further an increase in fuel price would encourage consumers to switch to a more fuel-efficient alternative, thus, increasing the sale of hybrid electric vehicles and vice versa. Further, since the fall in hybrid electric vehicles is very small between the years 2013 and 2015, the results cannot provide sufficient information on whether the market is maturing. Instead, it could simply imply that there have been some changes in external factors that are affecting the demand temporarily.

Regression AnalysisEdit

The regression analysis resulted in an R Squared value of 0.70206. An R Squared value close to 1 is desirable. The data observed resulted in an estimated b value of 0.53275. In general, through the result portrayed in the “HEV Sales Predicted” curve on Graph 1, the birth phase of the market is presented in the span of years 1999 to 2004 as the graph has a horizontal shape. Between the years 2004 and 2012, the “HEV Sales Predicted” curve shows the growth phase of the market for sales of hybrid electric vehicles. This is observed through the initial increase in sales with a increasing gradient of the curve and the slower increase of sales in vehicles presented through the rise in the curve along the y axis with a decreasing gradient. According to the curve, “HEV Sales,” the market hits its peak at 2013 where it is assumed to have reached the mature phase. Unlike the actual data observed showing a market peak at 2013 and therefore market maturity, the predicted model assumes that the sales of the hybrid electric vehicles will rise after 2013 in the years to follow.

Analysis of the curve shows that the model underestimates the amount of sales of hybrid electric vehicles from 1999 till 2009. It then overestimates the sales between the years 2009 and 2012 followed by another underestimation in the year 2013, where the actual market hits a peak.