Fuel Cells

Fuel Cells in Cars

A fuel cell car uses fuel cells to produce the energy required for motion. Fuel cell is an electrochemical cell in which the energy of reaction between fuel and an oxidant is converted into electrical energy. The common fuel used in a fuel cell is hydrogen. The fuel cell cars differ from the electric cars in the source of electricity. The fuel cell cars generate the electricity required without drawing from external sources unlike an electric car.

Type of fuel used

Fuel cells are electrochemical conversion devices where chemical energy is converted into electrical energy. The fuel and the oxidant flows into the cells and the reaction products flow out of the cell. The reactant needs to be replenished continuously. Hydrogen is commonly used as fuel in fuel cells cars. Other fuels which can be used include hydrocarbons and alcohols. Oxygen from air, chlorine and chlorine dioxide can act as oxidants. Using hydrogen as a fuel in fuel cell cars almost doubles the efficiency compared to other internal combustion engines. The fuel cells do not undergo any change by itself.

The performance of fuel cell cars

The efficiency of a fuel cell is dependant on the amount of power drawn from it. As the power drawn in a fuel cell increases, the efficiency decreases. The efficiency of a fuel cell is proportional to the voltage. Factors like the air on which the fuel cells may be operating needs to be considered while calculating the efficiency of fuel cells. Fuel efficiency in the fuel cell cars decreases with load. The pressurization of the air also reduces the efficiency significantly. The tank to wheel efficiency of the fuel cell car comes around 45% at low loads. If the fuel cell cars use hydrogen stored as high pressure gas, the power-plant-to-wheel efficiency is seen around 22%. The energy generated by the fuel cells is stored in batteries in the fuel cell car. The performance of the fuel cell driven cars can be compared with the standard oil fuelled cars by considering the efficiencies up to the point where mechanical power is generated. After the mechanical power generation, the components involved and method of operation is similar to conventional cars. The electrical energy generated from the chemical energy of the reactant needs to be converted into mechanical energy. A highly efficient electric motor and inverter used for this increases the overall performance of the fuel cell driven car. The performance as well as the efficiency of the fuel cells driven car is compromised if pure hydrogen is not used as a fuel source.

Pros and cons of the fuel

Even though the hydrogen fuel cells do not have any toxic waste, there are some disadvantages introduced by a fuel cell car. Hydrogen being a low density element, storing them is very difficult. These cars are less suited for long distance travel as the hydrogen fuel supply may run out. If the fuel cells are fuelled by gases like methanol and ethanol instead of hydrogen, large amount of carbon dioxide which is a greenhouse gas is released into the atmosphere. The use of hydrogen gas as a reactant demands an on the board hydrogen extractor which makes the fuel cell car highly expensive.  Another issue is regarding the charging stations. Until the fuel call car market becomes stable, infrastructure development for charging and maintenance wont happen which in turn will affect the growth of the market. This interdependency between the market and the infrastructure development may act as a delay in bringing up the production and usage of fuel cell cars.          

Fuel Cell Use in different countries

The emerging technology of fuel cell cars has the potential to significantly reduce energy use and harmful emissions and dependence on foreign oil. These cars are well supported by most of the countries as they are cheaper to operate and are pollution free. Billions of dollars are spent by the global automobile leaders to bring efficient and high performing fuel cell cars into the market place. Some of the automobile giants invested in fuel cell cars are Ford, GM, Daimler Chrysler, Honda and Toyota.

Environmental benefits and drawbacks of Fuel Cells

The only emission from a fuel cell car operating on hydrogen is water vapor. The fuel generators on the board of these cars emit only fewer amounts of pollutants. These are near zero emission vehicles and so they do not require elaborate emission controlling technologies. Fuel cells are very clean environmentally friendly source of energy due to their super efficient use of fuel for electricity and heat. Fuel cells do not produce the same amount of unhealthy gases generated by the burning gasoline in cars. As there is no combustion in a fuel cell, fewer gases are released into the atmosphere. Sulfur oxides and nitrogen oxides are not released into the atmosphere and the emissions do not contain any particular matter. Since the level of emission is very low from a fuel cell, the cars employing fuel cells as the energy source do not offer any threats to the environment. If the hydrogen used in fuel cells is generated from renewable sources like wind, solar and water sources, then fuel cell cars are the best available energy efficient and most environmental friendly cars in the market.

Currently the hydrogen required for these fuel cells is generated mainly from fossil fuel which is one disadvantage. Concerns are there regarding the possibility of hydrogen leaks. In a large scale fuel cell economy where hydrogen is used in fuel cells, manufacturing, storing and transporting, hydrogen can result in leaks and thereby accumulating hydrogen in the upper atmosphere leading to the ozone layer depletion. The infrastructure for generation and usage of hydrogen should be well designed to avoid such possibilities.

Reliability of Fuel Cells in Cars

The fuel cells used in these cars to generate power have longer life. They do not introduce any major maintenance issues in the long run. The constant supply of the reactant hydrogen is necessary for the operation of a fuel cell car. As these cars require hydrogen charging stations for filling hydrogen fuel, long distance travel to places lacking the hydrogen fuel charging infrastructure is practically impossible.

Cost of the fuel

The cost of hydrogen fuel is around 2$ per gallon of gasoline equivalent at the station. As hydrogen generation requires expensive system setups, the initial cost of fuel cells are higher than the running cost.

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