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Electric Propulsion Systems

January 20th, 2009
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by Ferry ST

Hybrids are planning to use electric propulsion systems which prove to be very efficient and also environmentally friendly. There may be various approaches and methods in order to accomplish movement using electric power but the main idea is still the same. These systems are already working and will further help develop alternate fuel.

What is Electric Propulsion?

Electric propulsion is the acceleration of gases in order to produce propulsive thrust through electric and magnetic body forces, electric body forces or electric heating. The electric propulsion system is usually incorporated in rocket science wherein it manages energy enough to produce a powerful thrust. An electric propulsion system is an alternative to nuclear propulsion system. The total thrust is less powerful compared to a nuclear rocket but still enough to produce effects.

According to a number of studies, any engine used as a primary source of such powerful propulsion must produce exhaust velocities of around 10 to 20 km/s. There are also storable chemical systems used in rockets with an exhaust velocity of around 5 km/s but overall is less efficient.

Propulsion systems that do not require energy through chemical reactions are still needed. There are electric propulsion thrusters able to produce exhaust velocities of around 10 to 20 km/s which increases payload and reduces propellant mass. The consequences however, are less powerful thrusters consuming larger quantities of power.

The 3 Categories of Electric Propulsion

Electro thermal propulsion is when the propellant is electrically heated then isentropically expanded through a C/D or convergent/divergent nozzle. The system works as electrical energy heats propellants that produce gases as a result. The gases are sent through the C/D nozzle creating thrust. Catalyzed hydrazine or another neutral gas is used in thrusters like arc jets and resistojets.

Arc jets can also be used to heat the propellants via an electrical arc discharge. The arc in the arc jet is a beam of electrons produced from the cathode tip then gathers at the anode. Since an arc jet has a cathode and an anode, a constrictor is also present which is a narrow pathway between the two charges.

Electrostatic thrusters are also called ion thrusters. These use an ionized propellant accelerated through electric fields applied directly like gridded ion thrusters and Hall thrusters. The technique of propulsion is also known as ion propulsion technique since ions are mainly used in the process. Electrostatic energy is used to produce propulsion.

The electrons from an atom are stripped off then converted to ions. The ions are accelerated by electrical forces to high temperature without needing thermal energy producing thrust. The atoms after losing electrons become positively charged.

Electromagnetic thrusters produce thrust using electric and magnetic forces that interact with charged plasmas like ions and electrons. An example of these is the magnetoplasmadynamic thruster or MPD. The system heats the propellant to a plasma state before being accelerated. A large current is passed by electromagnetic forces through gas in order to ionize the propellant. Plasma is the ionized propellant which is then accelerated by Lorentz force, an electromagnetic force producing thrust.

Effect on Fuel

Decoupling engine speed and power output from the propeller will provide the opportunity to improve propeller efficiency. Since electric forces and electromagnetic forces kick in for support, gasoline and diesel propulsion systems in vehicles will decrease the chances of wasting a huge part of power and energy.

The chances of engine overload are eliminated resulting to better fuel economy and better gas mileage. In addition, there is higher efficiency over longer distances and various speeds and loads.

A study conducted to check how much electric propulsion systems can help diesel and gasoline engines showed that at least 10% fuel savings is achieved by simply allowing the engine to move along with the load reducing inefficiencies due to low load with high speed. Larger propellers can also save as much as 7% of fuel compared to traditional models.

With the total load split between multiple generators, as much as 20% of fuel can be saved plus another 13% by matching the power produced by the engine to the power required by the propeller. A variable-speed generator will help accomplish this. Overall, 30% to 50% can be saved compared to a very efficient diesel-electric or gasoline-electric system.

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Electric Hybrid Vehicles

January 19th, 2009
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by Ferry ST

Hybrid electric vehicles are means of transportation that incorporates the use of an electric system in the main engine. Since gasoline engines have caused a variety of environmental pollutants, people are now starting to rely on electric power which has zero emission and are more fuel efficient. Here is an overview about hybrid electric vehicles.

What is a Hybrid Electric Vehicle?

A hybrid electric vehicle or HEV is a vehicle that is a combination of a rechargeable energy storage system or RESS and a traditional propulsion system. It saves more fuel and also covers more distance compared to battery electric vehicles since charging is done through a variety of methods instead of a lone external source. The propulsion power systems of various hybrid electric engines may be composed of the same parts or subsystems.

Usual hybrid electric models have an ICE or internal combustion engine as well as electric batteries that support the main electric motors. The mechanisms of the HEV have improved significantly with the discovery of regenerative braking wherein kinetic energy can be stored. Fuel is conserved more and emission is minimized as much as possible. Drivers get to cover longer ranges as well without worrying about speed and performance.

The combustion engine too can generate electric power through a spinning electrical generator. The energy either provides power directly to the motor or recharges the battery. The internal combustion engine automatically shuts down when idling but immediately restarts as necessary. The engine is also considerably smaller which is more efficient.

Do HEVs Still Use Gas and Diesel?

Gasoline engines will most likely remain in the hybrid vehicle scene for years to come since it generates power like no other discovered or affordable material can. Petroleum gasoline is considered as the main fuel source but can be mixed with different concentrations of ethanol from other energy sources. HEVs use up around 15% bioethanol like other internal combustion engines but manufacturers are currently finding ways to improve ratios for increased fuel efficiency and decreased emission.

There are diesel electric engines wherein a diesel engine is mainly used to provide power. Diesel can prove to be more efficient than gasoline although speed and noise may not be its best features. Diesel can be better-performing and can provide power for long periods of time without wearing much.

Gas mileage is also better due to its high torque while using biodiesel. The need for petroleum is minimized depending on the type used. Although diesel are usually known to drive bigger transportations like trucks, SUVs and vans, hybrid diesel-electric vehicles have also appeared in smaller versions like sedans and other passenger cars.

Hybrid Electric Vehicle Types

Hybrid diesel-electric motorcycles have been created having a top speed of around 800 mph with a very affordable retail price of $500. Several known automobile manufacturers have also joined the bandwagon like Honda, Ford, General Motors, Mazda, Nissan and Toyota. These big names are currently innovating to continuously provide well-performing vehicles with all the advantages.

HEVs have been very specific in being made available for future taxicab models. Since these vehicles are usually on the go all day long, fuel and emission can be improved through automatic engine shutdown, regenerative braking and idling. There are plug-in models in which taxicabs can conveniently recharge batteries at designated stands throughout the city. Plug-in hybrid electric models are also available in the form of sedans and mini-cars.

Hybrid-electric buses and trucks are also circulating due to the many advantages offered. The diesel engine is smaller which means that it is more efficient. There is also a 1.9-liter diesel engine instead of the 7.0, emitting less harmful gases. Emission reduction has been reported to be around 30% while fuel efficiency is around 40%. Some hybrid-electric buses have gas turbine generators. More efforts are exerted to convert other means of transportation like trains.

Several other types of HEVs are available today and are being used in various projects. The military uses diesel-electric hybrid trucks which has a fuel cell auxiliary power and diesel electric unit. The United States Army began using hybrid electric drives for all vehicle systems and subsystems. Other notable trucks have also found their purpose in commercial sectors, scientific projects and mining endeavors.

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A Brief Guide to Hybrid Vehicles

January 18th, 2009
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by Ferry ST

Hybrid vehicles were the stuff of dreams centuries ago. Nobody ever thought that creating a vehicle independent from fuel was possible. Fortunately with the continuing development of hybrid technology, more efficient and practical vehicles have been created. In the recent years the campaign for global warming has brought the attention of the public. Hybrid cars are now becoming steadily popular available in different types from compact sedans to SUVs.

Environmental issues are not the only reason that has made the public favor hybrid cars. Rising gas prices is also one of the major reasons why people prefer hybrid cars than conventional ones. Its also practical in suburban environments where you don’t really need horsepower but gas mileage.

Hybrid vehicles

There are different types of hybrid vehicles. They can vary from the simplest wheelbarrows to ships. No matter what form they are, these vehicles help in reducing greenhouse and noise emissions. Although these vehicles are expensive due to their unique structures, developments will continue to provide more alternatives to the public. These cars may not compare to conventional ones with a 200 horsepower but why would you need that if you only need 20 in the streets?

The simplest hybrid would be the single wheeled vehicles. These are wheelbarrows famously depicted with sails. This can be seen in Chinese sailing carriages.

The next is two wheeled vehicles. These are usually cycle type vehicles. The best example would be the Moped and electric bicycles. They are powered by an electric motor or an internal combustion engine in combination with the rider’s muscles. This concept was also used in the 1800’s by motorcycles. The electric bicycle can either be a parallel or a series hybrid.

Hybrid vehicles are not just limited to private cars. There are also hybrid power trains used by heavy vehicles. There are diesel or turbo electric buses, railway locomotives, heavy duty vehicles, hydraulic machinery and ships.

In ships a diesel engine drives the electric generator or hydraulic pump which in turn powers one or more hydraulic or electric motors. Sails and engines were early forms of hybrids which may be used again due to rising fuel costs.

More developments are continually being made in hybrid structures and systems for efficiency. Today buying a hybrid car is expensive but it will be beneficial in the long run. It does not just save fuel costs but also removes pollution that can harm the health of the people and take whatever it is left of the environment.

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