ELECTRIC FUEL

4.0 ELECTRIC FUEL

Electricity is unique among the alternative fuels in that mechanical power is derived directly from it, whereas the other alternative fuels release stored chemical energy through combustion to provide mechanical power. Motive power is produced from electricity by an electric motor. Electricity used to power vehicles is commonly provided by batteries, but recently fuel cells are also being explored.

4.1 Battery:

Batteries are energy storage devices. A large number of various types of batteries are being tested for use in electric vehicles. Some of the technologies include lead-acid, nickel cadmium, nickel iron, nickel zinc, nickel metal hydride, sodium nickel chloride, zinc bromine, sodium sulphur, lithium, zinc air and aluminum air. On the other hand fuel cells convert chemical energy to electricity, which then power the motor.

4.2 Fuel Cell:

Day by day fuel cells are becoming the most promising so far as electricity generation is concerned. A fuel cell is an electrochemical energy conversion device. It is two to three times more efficient than an internal combustion engine in converting fuel to power. A fuel cell produces electricity, water and heat using fuel and oxygen in the air. Water is the only emission when hydrogen is the fuel.

4.3 Production:

Electricity is produced from power plants throughout the country, transmitted to substations through high voltage transmission systems, stepped down to lower voltages, and carried to homes and businesses through local distribution systems. This electricity is charged and stored in the onboard rechargeable batteries, which power the motor of the vehicles.

Like battery powered vehicles fuel cell vehicles use on-board electric motor. But while drivers must periodically recharge battery powered vehicles with electricity generated elsewhere, fuel-cell vehicles make their own power from on-board supply of hydrogen, or a hydrogen-rich fuel such as natural gas, methanol, ethanol or gasoline. This enables drivers to fill up at a service station, rather than recharge the car, making it a more practical solution for today's automobiles.

There are six basic types of fuel cells, solid oxide, phosphoric acid, alkaline, molten carbonate, direct methanol and Proton-Exchange Membrane (PEM). The PEM fuel cell has several advantages for transportation use:

- High power density
- Relatively quick start up
- Compact size
- Low operating temperature
- Low noise levels.

4.4 PEM fuel cell components:

 

A basic fuel cell has three parts: An anode, a cathode and an electrolyte separating the anode from the cathode. In a PEM fuel cell, the electrolyte is a proton-exchange membrane. The fuel (Hydrogen) starts out at the anode and combines with oxygen at the cathode to form water. Since water is in a lower energy state than hydrogen and oxygen by themselves, there is a chemical potential that induces the hydrogen and oxygen to combine into water.

The hydrogen at the anode separates into individual protons and electrons, the constituent particles that comprise hydrogen atoms. A catalyst at the anode helps the separation occur. The membrane allows protons to pass through it, but not electrons.

The proton travel from the anode to the cathod through the membrane. Electrons travel from the anode to the cathode not through the membrane, but through an external device (electrical load). Moving electrons are by definition electricity. The electrons then travel to the cathode, where they recombine with the protons and oxygen to form water.
A full size electric vehicle needs about 50 to 60 KW of power to accelerate and about 12.5 KW of power for cruising. A single PEM fuel cell has about 350 W of power, or 4 W per square inch of the cell area. To supply the necessary power, auto manufacturers may combine 150 and 200 individual fuel cells into a "stack".

Fuel cells require hydrogen to operate, but the storage of hydrogen and availability of hydrogen as a vehicle fuel pose challenges. Because of this, many fuel cell vehicles currently being developed to extract their hydrogen from another fuel, such as methanol or gasoline through the use of an on-board fuel processor or reformer.

4.5 Emissions:

Electric vehicles do not undergo any combustion process. Mechanical power is directly derived from electricity. There are no tailpipe emissions. Water is the only emission when hydrogen is used as the fuel in fuel cells. But the process of commercial hydrogen production to feed the fuel cell is associated with some CO2 emissions.

4.6 Advantages of electric fuel:

The advantages of electric fuel/fuel cells are:

- No tailpipe emissions.
- Vehicles using electric fuel demand less maintenance.
- Electric fuel vehicle have less moving parts to service and replace.
- Acceleration, speed and handling for well-designed vehicles are equivalent to, or better than, those of comparable internal combustion powered vehicles.
- Fuel cells vehicles are highly efficient.
- Fuel cells have high power density.

4.7 Disadvantages of electric fuel:

Some of the disadvantages of electric fuels are:

- Batteries may take time in charging.
- Weather extremes and use of accessories such as air conditioning can affect the range of electric vehicles.
- Noble metal required for some fuel cells thereby increasing the cost.
- Impurities in the hydrogen can hamper cell performance.
- Commercial production of hydrogen to cater to the fuel cells results in substantial copious CO2 emissions.
- Costly technology.
- Limited life of the battery is also a limitation of electric vehicles.

More than 4000 electric vehicles are operating throughout the United States with the largest numbers in California.

4.8 Operation & Performance:

The main features of operation and performance of electric vehicles are:

- Efficient operation when properly designed.
- Less moving parts demand less maintenance.
- Less noisy while in operation.
- Range spans from 50 to 130 miles depending on the vehicle weight, design and type of battery.
- Decrease in available specific energy in transient driving cycles and decrease in vehicle range with increased speed is reported.
- Sometimes cold weather may drop the specific energy, which the battery can store and hence vehicle range.

4.9 Safety Issues:

When designed properly the electric vehicles are quite safe. The battery or fuel cell stack on-board the vehicles contain enough charge to be fatal, so proper design and grounding should be done.

4.10 Storage & Distribution:

Electric vehicles require charging facilities, which automatically exists with the infrastructure of electricity utility distribution system. Fuels like methanol, ethanol etc. needed for extraction of hydrogen for fuel cells can be obtained from service stations. Installation of equipment at charging locations are expensive and sometimes charging may take much time depending on the remaining state of charge of the batteries and available voltage.

4.11 Indian Initiative on Electric Vehicles:

In India Bharat Heavy Electricals Ltd., Eddy Current Controls India Ltd., Cheetlec Vehicles India Ltd. and recently Bajaj are established to produce electric vehicles. The technologies developed so far have reached a level to meet the basic operational requirements of urban road transport and industrial sector in a limited way. They are on their way to commercialise various models developed.

In the last Auto Expo during January 2002, several auto companies of India have displayed their model electric vehicles. Reva Electric Car Company, Bangalore displayed the first electric car of the country called "Reva". Bajaj and Mahindra & Mahindra have also developed electric vehicles in the country.

Government of India has shown interest in supporting the developments of electric vehicles. Ministry of Non-conventional Energy Sources, Govt. of India have provided the following incentives to promote Evs in the country:

- Rs. 1000,000 per road vehicle
- Rs. 2000,000 in case of an additional battery
- Rs. 50,000 per industrial vehicle to a public, private sector users, Govt. Departments along with 100% depreciation in the first year and IREDA loans at 10% interest for 5 years.

Ministry of Non-conventional Energy Sources (MNES) has constituted a Committee in 2000 headed by Dr. Mashelkar. This Committee on " High Energy density Batteries for Electric Vehicles" also recommended for development of appropriate low weight and reasonable cost batteries for commercialization. Other operational programmes and field trial projects for Evs are also being taken up through a consortium approach of R&D organizations, manufacturers of batteries, ARAI, VRDE and other government agencies.

Several agencies including MNES have supported projects on different types of fuel cell technologies with the involvement of national laboratories, universities and industries with an aim to develop suitable materials, catalysts and components to strengthen manufacturing base for production of fuel cells in India. Small PAFC stacks have been developed and tested by BHEL. The SPIC Science Foundation of Chennai has developed an improved version of 5 kw fuel cell module. A research project is under implementation at the Central Glass and Ceramic Research Institute, Kolkata for the development of 1 kw SOFC power pack. Indian Institute of Science, Bangalore will construct a 100-watt liquid-feed solid polymer electrolyte direct method fuel cell (DMFC). IIT, Chennai is also developing in collaboration with SPIC a 250-watt DMFC stack. Comparision of different fuel cell technologies is given in Table-4.