Energy Saving and Conversion(MSJ0200)

2011. Autumn semester

3. and 4. lectures

Transportation

Transportation

• Energy consumption of transportation

• Emissions from transportations, directives, regulations.

• Different type of internal combustion engines, hybrid and hydrogen cars

Introduction

• The private automobile is the primary mode of transportation for developed countries.

• More than 80 per cent of households have a personal vehicle (example Canada).

• In total, there are 19.2 million passenger cars, vans, sport utility vehicles, and pick up trucks registered in Canada and these are typically driven more than 332 billion cilometres per year (16600 km/per car).

• This level of private automobile ownership and use has had profound impacts on the economy and people’s lifestyles. But the scale of automobile use in around the world has also come at a cost.

• Energy is needed to power an automobile, and most of this energy comes from the burning of fossil fuels in the vehicle’s engine. This burning or “combustion” process produces emissions that pollute the air and contribute to climate change. In fact, transportation is a major source of these emissions.

Emissions by Sector (Canada -2006)

Emissions by Sector (Estonia - 2008)

Emissions by Sector (Estonia - 2008)

• To make substantial reductions in emissions, we need to reduce their overall transportation energy use.

• One way this can be accomplished is by minimizing the amount of fuel that an engine needs to burn while being operated – or, in other words, increasing vehicle fuel efficiency.

• Transportation alternatives such as public transit, biking or walking is also an effective way to reduce one’s transportation energy use.

• Alternative fuels.

• New construction of car hybrid and electric car.

Automobile Fuel and Emissions• The energy to power an automobile comes from its

fuel. The purpose of an automobile’s engine is to convert the chemical energy of the fuel into kinetic energy – or motion – that powers the vehicle. In other words, the engine is simply a mechanical device that uses the chemical energy of the fuel to move the vehicle down the road.

• This is done by burning or combusting the fuel inside the engine, which gives rise to the term internal combustion engine (ICE).

• If the combustion process followed a perfectly ideal chemical reaction, then complete combustion of hydrocarbons in the fuel (HxCy) with oxygen present in the air (O2) would produce only carbon dioxide (CO2) and water (H2O), as shown in the following chemical reaction equation:

Combustion is neither a complete nor a perfect process; therefore, the products in the engine exhaust also contain some unburned fuel.

Emissions of unburned fuel are also classified as Volatile Organic Compounds (VOCs) – “volatile” because they easily and quickly evaporate into the air.1 In addition, there is also a degree of incomplete or partial combustion of hydrocarbons, which results in emissions of carbon monoxide (CO).

The combustion process occurs under conditions of high heat and pressure, which causes nitrogen in the air to bond with oxygen and form Oxides of Nitrogen (NOx).

The sulphur in fuel also bonds with oxygen to form Oxides of Sulphur (SOx - under some conditions, the sulphur can also bond with hydrogen to produce a small amount of hydrogen sulphide, H2S).

In addition to these chemical compounds, automobile engines also emit varying amounts of Particulate Matter (PM), which can include microscopic liquid droplets and particles of soot produced during combustion. Thus, the “real” chemical equation of combustion in the engine looks more like this:

The characteristics of the major pollutants associated with

automobile use:• CARBON DIOXIDE (CO2)• VOLATILE ORGANIC COMPOUNDS (VOCs)• OXIDES OF NITROGEN (NOx)• CARBON MONOXIDE (CO)• PARTICULATE MATTER (PM)• OXIDES OF SULPHUR (SOx)• OTHER ENGINE EMISSIONS

CARBON DIOXIDE (CO2)

CO2 is a greenhouse gas (GHG) that persists in the atmosphere for about 150 years. Due to the large amount of CO2 emitted worldwide from the burning of fossil fuels, such as gasoline and diesel, it is the main target of global efforts to reduce atmospheric concentration levels of GHGs and lessen the negative impacts of climate change.

Carbon dioxide is also the most significant vehicle emission by weight. For each litr of gasoline burned, approximately 2.3 kg of CO2 is produced (the exact amount depends on how much carbon and oxygen end up in other combustion products for diesel 2,7 kg)).

Less than ideal combustion produces less CO2 but more air pollutants, whereas the use of “cleaner” fuels better controlled combustion and exhaust after-treatment technology reduces air pollution emissions and leads to a minor increase in emission of CO2 (since more of the carbon in the fuel ends up bonded with oxygen). For each litr of diesel burned, approximately 2.7 kg of CO2 is produced. The average car produces about two to three times its weight in CO2 every year.

VOLATILE ORGANIC COMPOUNDS (VOCs)

VOCs are defined as “volatile” because they easily and quickly evaporate into the air. There are many thousands of different types of VOCs emitted into the atmosphere from a range of natural and manmade sources, including those that are harmful and those that are not.

VOCs also react with nitric oxide (NO) and nitrogen dioxide (NO2) (which are also engine combustion products, see following page) in the presence of sunlight and heat to form ground-level ozone (O3). O3 is considered a by-product of automobile emissions (and many other non-automobile sources of emissions) and is both toxic and a major component of smog.

VOCs emitted from automobile engines are also referred to as hydrocarbons (HC) because they are primarily uncombusted hydrocarbon fuels. Gasoline and diesel are complex mixtures of different types of hydrocarbon molecules, some of which are harmful and can end up in tailpipe emissions, including benzene (H6C6) and formaldehyde (HCHO). VOCs such as these can be toxic (even in small doses), impair brain function or cause cancer.

Another hydrocarbon emitted from automobile engines is methane (CH4), which is not very reactive and hence does not contribute to smog formation as other types of VOCs do. However, it is a very potent GHG, with more than 20 times the global warming potential of CO2 and persists in the atmosphere for approximately 12 years.

OXIDES OF NITROGEN (NOx)

Under the high pressure and temperature conditions of a typical engine, nitrogen and oxygen in the air (that is drawn into the engine) combine to form NOx. Fuel is not directly the cause of NOx formation, but rather it is the heat produced by the combustion of the fuel that leads nitrogen and oxygen to bond.

Thus, NOx emissions are likely to be a problem regardless of the type of fuel burned, although the amount of NOx formed may vary among fuel types. The chemical arrangements of NOx include nitric oxide (NO), nitrogen dioxide (NO2) and nitrous oxide (N2O). NO and NO2 are air pollutants while N2O is a potent greenhouse gas.

NO and NO2 react with VOCs in the presence of sunlight and heat to form ground-level ozone (O3) and play a part in the formation of fine particulate matter, or PM (discussed on following page). They can also combine with water vapour to form nitric acid, which contributes to acid rain.

NO2 irritates the lungs, impairs lung function (even with short term exposure) and lowers resistance to respiratory infection. In children and adults with respiratory disease, NO2 can cause symptoms including coughing, wheezing and shortness of breath. In itself, N2O does not contribute to poor air quality, but it is a potent GHG. With roughly 300 times the global warming potential of CO2, N2O persists in the atmosphere for about 100 years.

CARBON MONOXIDE (CO)

CO is a colourless, odourless gas that is poisonous, and forms in the engine as a result of incomplete combustion. This phenomenon is worsened when the fuel-to-air mixture is too rich (perhaps due to a poorly tuned engine or faulty engine control systems). In the human body, CO reduces the ability of the blood to carry oxygen from the lungs.

Everyone’s health is threatened by this potentially lethal emission, but people with heart disease are most vulnerable to its effects. Other high risk groups include pregnant women (and their fetuses), infants, children, the elderly and people with anemia and respiratory or lung disease. As it decays, CO also contributes to the formation of ozone (O3).

PARTICULATE MATTER (PM)

PM is emitted directly from automobile tailpipes as microscopic carbon residues (a product of fuel combustion) and as liquid droplets. Particles are measured by their diameter and range in size from 0.005 to 100 microns (one micron equals one thousandth of a millimetre or 1/50 of the width of an average human hair).

Some PM is visible, such as the black smoke often seen in diesel truck exhaust. These particles can be large enough to become trapped in the body’s filters that are the nose and throat, limiting the potential health threat. Smaller particulates, measuring less than 10 microns (PM10), are invisible and can be breathed into the lungs.

Particulates that measure less than 2.5 microns (PM2.5) are able to penetrate deep into the lungs. The smaller the particle, the deeper it may enter the lungs and theoretically, the greater the damage it can cause. The toxicity and carcinogenic effect of PM can vary according to its source and composition. Other toxic chemicals can adhere to fine PM, compounding the threat as they are carried deep into the lungs where they can pass into the bloodstream.

PM is also a component of smog and is suspected to have a secondary impact on global warming trends as it reflects, absorbs and scatters solar radiation.

OXIDES OF SULPHUR (SOx)

Under the high pressure and temperature conditions of a typical automobile engine, sulphur in the fuel and oxygen from the air combine to form SOx. The chemical arrangement of primary concern is sulphur dioxide (SO2). SO2 contributes to the formation of fine PM and therefore is a smog pollutant. Exposure to SO2 leads to eye irritations, shortness of breath, and impaired lung function.

Combining with water molecules to form sulphuric acid, SO2 is one of the more persistent pollutants and is a major source of acid rain, acid snow, and acid fog that impact ecosystems and urban environments. SOx can also interfere with the proper functioning of a vehicle’s emissions after-treatment system (i.e., catalytic converter) and, as a result, reduce its ability to decrease other harmful emissions such as HC, CO and NOx.

OTHER ENGINE EMISSIONS

In addition to the above list, there are various other possible emissions to consider. Over the years, various chemical compounds have been added to gasoline by oil refiners to enhance combustion properties and comply with emissions standards.

Examples include tetraethyl lead, which when added to gasoline increases its octane number (i.e., leaded gasoline), and methyl tertiary butyl ether (MTBE) and methylcyclopentadienyl manganese tricarbonyl (MMT), which reduces incomplete combustion by adding oxygen to the fuel formulation. Additives such as these can end up in the combustion products in one form or another and emitted to the atmosphere. These substances can be toxic to human health or otherwise harmful to the environment.

Particle Number Emissions. Under the draft implementing legislation, a particle number emission limit of 5 × 1011 km-1 (PMP method, NEDC test) becomes effective at the Euro 5/6 stage for all categories of diesel vehicles (M, N1, N2). The particle number limit must be met in addition to the PM mass emission limits listed in the above tables.

Emission Durability. Effective October 2005 for new type approvals and October 2006 for all type approvals, manufacturers should demonstrate that engines comply with the emission limit values for useful life periods which depend on the vehicle category, as shown in the following table.

Comparing with US Conclusion:

Testing

Emission Testing

Emissions are tested over the NEDC (ECE 15 + EUDC) chassis dynamometer procedure. Effective year 2000 (Euro 3), that test procedure was modified to eliminate the 40 s engine warm-up period before the beginning of emission sampling. This modified cold start test is referred to as the New European Driving Cycle (NEDC) or as the MVEG-B test. All emissions are expressed in g/km.

The draft Euro 5/6 implementing legislation adopts a new PM mass emission measurement method (similar to the US 2007 procedure) developed by the UN/ECE Particulate Measurement Programme (PMP) and adjusts the PM mass emission limit to account for differences in results using the old and the new method. The legislation also introduces a particle number emission limit at the Euro 5/6 stage (PMP method), in addition to the mass-based limits. At the time of adoption of the Euro 5/6 regulation, its mass-based PM emission limits could only be met by closed particulate filters. Number-based PM limits would prevent the possibility that in the future open filters are developed that meet the PM mass limit but enable a high number of ultra fine particles to pass.

How do increase fuel consuption

Shape drag

The forward motion of the vehicle pushes the air in front of it. However, the air cannot instantaneously move out of the way and its pressure is thus increased, resulting in high air pressure. In addition, the air behind the vehicle cannot instantaneously fill the space left by the forward motion of the vehicle. This creates a zone of low air pressure.

The motion of the vehicle, therefore, creates two zones of pressure that oppose the motion by pushing (high pressure in front) and pulling it backwards (low pressure at the back) as shown in Figure 2.5. The resulting force on the vehicle is the shape drag. The name “shape drag” comes from the fact that this drag is completely determined by the shape of the vehicle body.

Aerodynamic drag

is a function of vehicle speed V, vehicle frontal area, Af , shape of the vehicle body, and air density, ρ:

where CD is the aerodynamic drag coefficient that characterizes the shape of the vehicle body and Vw is component of the wind speed on the vehicle moving direction, which has a positive sign when this component is in the same direction of the moving vehicle and a negative sign when it is opposite to the vehicle speed. The aerodynamic drag coefficients for typical vehicle body shapes are shown in Figure 2.6.

Ar engine (IC) (as well named Power Plant) Characteristics

The ideal performance characteristic of a power plant is a constant power output over the full speed range. Consequently, the torque varies with speed hyperbolically as shown in Figure 2.12.

Characteristics of a gasoline engine in wide open throttle are shown in Figure 2.13

Characteristics far from the ideal performance characteristic required by traction.

The IC engine has a relatively flat torque–speed profile (as compared with an ideal power plant), as shown in Figure 2.13. Consequently, a multigear transmission is usually employed to modify it, as shown in Figure 2.14

The electric motor is another candidate as a vehicle power plant, and becoming more and more important with the rapid development of electric, hybrid electric, and fuel cell vehicles. Electric motors with good speed adjustment control usually have a speed–torque characteristic that is much closer to the ideal, as shown in Figure 2.15.

Fuel Economy Characteristics of IC Engines

The fuel economy characteristic of an IC engine is evaluated by the amount of fuel per kWh energy output, which is referred to as the specific fuel consumption (g/kWh). The typical fuel economy characteristic of a gasoline engine is shown in Figure 2.30.

The fuel consumption is quite different from one operating point to another. The optimum operating points are close to the points of full load (wide open throttle). The speed of the engine also has a significant influence on the fuel economy. With a given power output, the fuel consumption is usually lower at low speed than at high speed.

Basic Techniques to Improve Vehicle Fuel Economy

The effort to improve the fuel economy of vehicles has always been an ongoing process in the automobile industry. Fundamentally, the techniques used mainly include the following aspects:

1. Reducing vehicle resistance:

Using light materials and advanced manufacturing technologies can reduce the weight of vehicles, in turn reducing the rolling resistance and inertial resistance in acceleration, and therefore reducing the demanded power on the engine. The use of advanced technologies in tire production is another important method in reducing the rolling resistance of vehicles.

For instance, steel wire plied radial tires have a much lower rolling resistance coefficient than conventional bias ply tires. Reducing aerodynamic resistance is also quite important at high speeds. This can be achieved by using a flow-shaped body style, a smooth body surface, and other techniques. Furthermore, improving transmission efficiency can reduce energy losses in the transmission. Proper transmission construction, good lubrication, proper adjustment and tightening of moving parts in the transmission, and so on will achieve this purpose.

2. Improving engine operation efficiency:

Improving engine operation efficiency has great potential to contribute to the improvement of vehicle fuel economy. There are many effective advanced techniques, such as accurate air/fuel ratio control with computer-controlled fuel injection, high thermal isolated materials for reducing thermal loss, varying ignition-timing techniques, active controlled valve and port, and so on.Example, impact of out-of-time of exhaust valve for burning rate

3. Properly matched transmission:

Parameters of the transmission, especially gear number and gear ratios, have much influence on operating fuel economy as described previously. In the design of the transmission, the parameters should be constructed so that the engine will operate close to its fuel optimum region.

4. Advanced drive trains:

Advanced drive trains developed in recent years, such as new power plants, various hybrid drive trains, etc., can greatly improve the fuel economy of vehicles. Fuel cells have higher efficiency and lower emissions than conventional IC engines. Hybridization of a conventional combustion engine with an advanced electric motor drive may greatly enhance the overall efficiency of vehicles.

Example

How an Internal Combustion Engine Works

The torque performance of the 4S SI engine is determined by the pressure within the cylinder, as shown in Figure 3.3. In the induction stroke (g–h–a), the pressure in the cylinder is usually lower than the atmospheric pressure because of the resistance of the airflow into the cylinder. In the compression stroke (a–b–c), the pressure increases with the upward movement of the piston. When the piston approaches the TDC, the spark plug produces a spark to ignite the air/fuel mixture trapped in the cylinder, and the pressure increases quickly. In the expansion stroke (c–d–e), the high-pressure gases in the cylinder push the piston downward, producing torque on the crankshaft. In the exhaust stroke (e–f–g), the gases in the cylinder are propelled out of the cylinder with a higher pressure than in the induction stroke.

The torque performance is usually evaluated by the gross work done in one cycle, usually called gross indicated work, Wc,in. The gross indicated work can be calculated by

where p is the pressure in the cylinder and V is the volume.

The work done in area B is negative, because the pressure in the induction stroke is lower than that in the exhaust stroke. In order to achieve much work in one cycle, area A should be made as large as possible by increasing the pressure in the expansion stroke, and area B should be made as small as possible by increasing the pressure in the induction stroke and decreasing it in the exhaust stroke.

The torque of an engine depends on engine size [engine displacement, which is defined as the volume that the piston sweeps from TDC to bottom dead center (BDC)]. A more useful relative performance measure is the mean effective pressure (mep), which is defined as the work per cycle per displacement:

Mechanical Efficiency

Not all the power produced in the cylinder (indicated power) is available on the crankshaft. Part of it is used to drive engine accessories and overcome the frictions inside the engine. All of these power requirements are grouped together and called friction power Pf ; thus

where Pb is brake power (useful power on the crankshaft). It is quite difficult to determine the friction accurately. In practice, one common approach for automotive engines is to drive or motor the engine on a dynamometer (operate the engine without firing it) and measure the power supplied by the dynamometer.The ratio of brake power (useful power on the crankshaft) to indicated power is called mechanical efficiency, ηm:

Specific Fuel Consumption and Efficiency

In engine tests, fuel consumption is measured as a flow rate—mass flow per unit time, ˙ mf . A more useful parameter is the specific fuel consumption (sfc)— the fuel flow rate per useful power output. It measures how efficiently an engine is using the fuel supplied to produce work:

where ˙ mf is fuel flow rate and P is engine power. If the engine power P is measured as the net power from the crankshaft, the specific fuel consumption is called brake specific fuel consumption (bsfc). The sfc or bsfc is usually measured in SI units by the gram numbers of fuel consumed per kW power output per hour (g/kWh). Low values of sfc (bsfc) are obviously desirable. For SI engines, typical best values of bsfc are about 250–270 g/kWh.

Specific Emissions

• The level of emission of oxides of nitrogen [nitric oxide (NO) and nitrogen dioxide (NO2) usually grouped together as NOx], carbon monoxide (CO), unburned HCs, and particulates are important engine operating characteristics.

• The concentrations of gaseous emissions in engine exhaust are usually measured in parts per million or percent by volume (mole fraction).

Specific emissions are the flow rate of pollutant per power output:

Fuel/Air Equivalent Ratio

Proper fuel/air (or air/fuel) ratio in the fuel/air mixture is a crucial factor that affects the performance, efficiency, and emission characteristics of an engine, as shown in Figure 3.8.

Basic Techniques for Improving Engine Performance,

Efficiency, and EmissionsForced Induction

The amount of torque produced in an IC engine depends on the amount of air induced into its cylinders. An easy way of increasing the amount of air induced is to increase the pressure in the intake manifold. This can be done by three means: variable intake manifold, supercharging, or turbocharging.

The intake manifold is like a wind instrument: it has resonant frequencies. A variable intake manifold tunes itself according to engine speed in order to exploit those resonant frequencies. If the tuning is proper, the amount of air induced into the cylinders can be optimized because the pressure in the intake manifold is increased. This technique improves the “breathing” of the engine but does not result in a very large increase of torque output.

A supercharger is an air compressor turned by the engine crankshaft. The air thus compressed is fed to the intake manifold. The advantage of a supercharger is that it can significantly increase the pressure in the intake manifold, even at low speed. The most significant disadvantage is that the supercharging power is taken from the engine crankshaft. This reduces the engine output and harms fuel consumption.

A turbocharger consists of a turbine driven by exhaust gases and of a compressor turned by the turbine. A turbocharger has the great advantage of taking its energy from the exhaust gases, which are normally wasted. Therefore, the efficiency of the engine does not suffer from the addition of the turbocharger. Turbocharging can tremendously increase the power output of the engine, especially if coupled to a charge cooling system Supercharging and turbocharging both suffer from two disadvantages: knock and emissions.

Compressing the intake air also increases its temperature. An increased temperature means a greater risk of auto-ignition and knocks for the mixture, and increased nitric oxide emissions. The solution to this problem consists in cooling down the intake air after compression by means of an intercooler or heat exchanger. The compressed air is passed through a radiator, while the ambient air or water is passed on the exterior of the radiator, removing the heat from the charge. The temperature of induced air can be reduced sufficiently to avoid auto-ignition and knock. Nitric oxide emissions are also reduced. It should be noted that an engine designed for forced induction has a lower compression ratio than an engine that is designed for normal induction.

Exhaust Gas Recirculation

In internal combustion engines, exhaust gas recirculation (EGR) is a nitrogen oxide (NOx) emissions reduction technique used in most petrol/gasoline and diesel engines.

EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. In a gasoline engine, this inert exhaust increases the amount of matter in the cylinder, which means the energy of combustion raises the temperature of the matter less, and the combustion generates the same pressure against the piston at a lower temperature. In a diesel engine, the exhaust gas replaces some of the excess oxygen in the pre-combustion mixture. Because NOx formation progresses much faster at high temperatures, EGR reduces the amount of NOx the combustion generates. NOx forms primarily when a mixture of nitrogen and oxygen is subjected to high temperature.

Catalyst converter

Eugene Houdry patent:

Hybrid Electric Vehicles

Today, there are hybrid electric vehicles composed of an internal combustion engine, a large battery pack, and one (or more) electric motors to deliver power to the driveshaft. As described above, this can help reduce fuel consumption by shutting off the engine when it is running inefficiently (e.g., driving at low speeds or idling), and by making use of regenerative braking.

However, if a larger or more advanced battery system is added that can store more energy and produce more power when needed, then the electric motor can play a much larger role in moving the vehicle, by providing significant power to the driveshaft and wheels. Since extra power is available to the wheels from the electric motor, there is less demand on the internal combustion engine to produce power across all operating conditions.

Therefore, the engine can operate at its peak efficiency more often, while the electric motor helps manage the load under conditions where the engine is less efficient, saving fuel. The extra power provided by the electric motor also allows the automobile manufacturer to downsize the combustion engine to reduce fuel consumption, while maintaining an acceptable level of acceleration performance. Some companies are adding extra battery capacity to enable their hybrids to run on all-electric drive at higher speeds and for extended periods of time.

With this extra energy storage capacity on-board, there is an opportunity to “top up” the charge with an external supply of electricity (say, from a household outlet) when the automobile is parked. Such vehicles are called plug-in hybrids. While the term “hybrid” generally refers to the combination of an internal combustion engine with an electric motor in a vehicle, there are a variety of ways that these two sources of power can be integrated.

As the electric architecture becomes more robust, the motor can displace the engine as the primary power source. Figure 3-1 conceptually describes a spectrum of electrification for automobiles, from minor to major roles for electrical power. Different configurations for hybrid systems are possible along a wide spectrum.

Parallel Architecture (opposite, top)In a parallel hybrid system, power to the wheels can be delivered by the engine and the electric motor simultaneously. The motor and engine drive shafts are coupled together, either before or after the vehicle’s transmission. The electric motor receives its power from the battery and, conversely, the motor running in reverse can also charge the battery via regenerative braking. Examples of this architecture can be found in Honda’s Integrated Motor Assist IMA® System used in the Civic Hybrid, and the Belt-Alternator-Starter (BAS) system used in GM’s Saturn Vue and Aura Green Line models.

Series Architecture (opposite, middle)

The series hybrid architecture is unique in that the engine does not directly power the wheels; instead, the wheels are powered entirely by the electric motor. The engine drives a generator, which produces electricity that can be stored in the battery for use by the electric motor later on, or delivered immediately to the motor to drive the wheels.

As in parallel architecture, the electric motor can also function as a generator, slowing the wheels and converting some of this energy into electricity to charge the battery. A computer continuously manages the direction of energy flow. An example of this type of vehicle is the Chevrolet Volt, which is under development by GM.

Series-Parallel Architecture (opposite, bottom)

The most complicated design is a combination of the series and the parallel systems. In this architecture, the engine can deliver direct power to the wheels and it can power a generator that supplies electricity to the battery. The battery supplies electricity to the motor that, in turn, delivers direct power to the wheels. As with the parallel and series architectures, the electric motor can deliver regenerative braking energy to the battery for later use.

This architecture allows greater flexibility and control over the engine, while minimizing the total mass and size of the accompanying electrical motors. Here the engine and two motors are all connected to a planetary gear system. Unlike a conventional transmission, which has discrete gears (4, 5 or 6, typically), a planetary gear system configured with two electrical motors can operate at any gear ratio that is deemed best by independently varying the speeds of the motors.

This allows the engine to run at the most efficient speed and results in excellent fuel efficiency performance. Examples of this type of system are Toyota’s Hybrid Synergy Drive® (used in the Prius, Camry hybrid and others), Ford’s Escape/Mariner Hybrid system, and the GM Two-Mode hybrid system (used in the Chevrolet Tahoe and GM Sierra).

Hydrogen vehicle

Sequel, a fuel cell-powered vehicle from General Motors

A hydrogen vehicle is a vehicle, such as an automobile, aircraft, or any other kind of vehicle that uses hydrogen as its primary source of power for locomotion. These vehicles generally use the hydrogen in one of two methods: electrochemical conversion in a fuel-cell or combustion : •In combustion, the hydrogen is burned in engines in fundamentally the same method as traditional gasoline cars. •In fuel-cell conversion, the hydrogen is reacted with oxygen to produce water and electricity, the latter of which is used to power electric motors.

The molecular hydrogen needed as an on-board fuel for hydrogen vehicles can be obtained through various thermochemical methods utilizing natural gas, coal (by a process known as coal gasification), liquefied petroleum gas, biomass (biomass gasification), by a process called thermolysis, or as a microbial waste product called biohydrogen or Biological hydrogen production. Hydrogen can also be produced from water by electrolysis. If the electricity used for the electrolysis is produced using renewable energy or nuclear power, the production of the hydrogen would (in principle) result in no net carbon dioxide emissions.

Hydrogen is an energy carrier, not an energy source, so the energy the car uses would ultimately need to be provided by a conventional power plant. A suggested benefit of large-scale deployment of hydrogen vehicles is that it could lead to decreased emissions of greenhouse gases and ozone precursors. The pollution generated at the point of use in the vehicle would be greatly reduced compared to conventional automobile engines.

Further, the conversion of fossil fuels would be moved from the vehicle, as in today's automobiles, to centralized power plants in which the byproducts of combustion or gasification can be better controlled than at the tailpipe. However, there are both technical and economic challenges to implementing wide-scale use of hydrogen vehicles. The timeframe in which such challenges may be overcome is likely to be at least several decades, as is the case with other advanced vehicles, such as gasoline electric hybrids, that are proposed to replace conventional gasoline and diesel vehicles.

Biofuels

• A biodiesel fuel vehicle is a vehicle that uses renewable fuel sources, such as vegetable oil and animal fats, to power and run a diesel engine.

• Biodiesel fuel, which is a type of biofuel, can be created from animal fats, restaurant grease from cooking food, oil from vegetables such as soybeans and corn, and even algae.

A biodiesel fuel car can use 100% biodiesel sources to power a car engine, or it can combine natural oils and fats with regular petroleum diesel to create a biodiesel blend. But you can’t just use straight animal fats or vegetable oils as fuel. They have to undergo a chemical reaction, known as transesterification, in which the fat or oil is purified and reacted with alcohol to form esters and glycerol. The end product can be used alone or mixed with regular petroleum

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