A fuel cell vehicle (FCV), also known as a fuel cell electric vehicle is a kind of motor vehicle that runs on a fuel cell. The fuel cell converts hydrogen fuel stored in a tank fitted to the vehicle to produce electricity. The electricity that is produced is converted to kinetic energy and is used to power a fuel cell vehicle’s motor system. Due to the rising costs of fuel and global warming issues, the need for a renewable and non-polluting source of energy is long overdue.
Motor vehicles running on gasoline are one of the leading sources of Greenhouse gases as they release carbon dioxide, hence the need to adopt fuel cell vehicles. It is on these grounds that scientists have been performing tests on the feasibility of the use of hydrogen as a fuel to power vehicles. Fuel cells produce electricity through an electrochemical reaction involving hydrogen and oxygen obtained from the air. Unlike gasoline that produces carbon dioxide when used as an automobile fuel, the only waste product obtained from the reactions in a fuel cell is water. In addition, hydrogen is easily available from air and water and this reduces the cost of using it as a fuel, it is renewable too.
A Brief History
Francois Isaac de Rivaz constructed the first hydrogen vehicle in 1807, but the car was not produced en masse due to the high cost of production and safety concerns. The first “road worthy” FCV was designed in 1966 by General Motors, the car had a range of approximately 150 miles and a maximum speed of 70mph. Most FCVs that are currently in construction are for test purposes, although a few brands have made it to the roads, these include the much-hyped Honda 2008 FCX Clarity, the Audi Q5-HFC, and the Mercedes-Benz F 800.
FCVs are in the early stages of development and before their full adoption, engineers have to overcome several challenges so that they can be competitive with regular vehicles. Vehicles produced using the current fuel cell technology are very expensive, however, scientists have predicted that with technological advancements, future fuel cell vehicles will cost the same as gasoline-powered vehicles.
Fuel Extraction Processes
Current fuel cells have low efficiency because “the energy required to isolate hydrogen from natural compounds (water, natural gas, biomass), package the light gas by compression or liquefaction, transfer the energy carrier to the user, plus the energy lost when it is converted to useful electricity with fuel cells” leaves an efficiency of around 25% (Weiss et al 2003). This efficiency value does not consider the efficiency at which Hydrogen is obtained, stored, and moved. This further reduces the efficiency to 22% if the fuel is compressed, and 17%, if it is stored in liquid form. These challenges must be overcome before fuel cell vehicles can be adopted.
Scientists have come up with a cheaper alternative for producing hydrogen. The process, known as steam reforming, extracts hydrogen from natural gas and is currently being used in numerous plants. The efficiency for supplying compressed hydrogen through this technique is almost 70%. This can be improved further by constructing plants near natural gas extraction areas to take advantage of the existing gas distribution networks. This is viewed as the most economical way for producing hydrogen fuel, and the first step in the adoption of FVCs (Weiss et al 2003).
Hydrogen fuel can also be obtained by reacting coal with water; this process can be harnessed for large-scale production of hydrogen due to the abundance of coal. Scientists are still trying to discover ways of capturing the carbon dioxide that is produced in the process to improve its efficiency and reduce the emission of carbon dioxide into the atmosphere.
The Fuel Cell
In order to have a deeper knowledge of the FCVs, it is imperative that one understands how the onboard fuel cell converts hydrogen fuel into kinetic energy. The fuel cell, also known as a hydrogen fuel cell, produces electricity through an electrochemical reaction involving hydrogen and oxygen. A major function of the cell is the conversion of chemical potential energy of hydrogen fuel into electrical energy, a form of energy that can be used for several purposes.
Hydrogen fuel is gotten through the catalytic splitting of water as shown below:
H2O O– + 2H+
The fuel enters the cell an inlet located at the anode end, then mixed with a catalyst, such as platinum, to increase the rates of reaction to provide a viable source of fuel. The catalyst splits the diatomic hydrogen compound into hydrogen electrons and protons as shown below.
H2 catalyst 2H+
Hydrogen electrons flow through the cell, basically, electron flow produces electricity.
The electricity is directed to the vehicle’s electric motor and converted to kinetic energy for propulsion. Due to the high efficiency of electric propulsion, only a small amount of energy is lost, unlike gasoline propulsion in which the energy loss is high because of frictional energy loss. Energy loss is further reduced by the car’s electronic control, which enables the driver to change the car’s responsiveness and smoothness, as compared to gears in gasoline-powered vehicles (von Helmolt & Eberie 2007).
FCVs are fitted with batteries used to store excess electrical energy and can be used when the car runs out of fuel. Hydrogen protons formed from the catalytic splitting of water go through the electrolyte membrane is reacted with oxygen to form water, i.e.
O– + 2H+ H2O
Hydrogen is continuously supplied from the onboard fuel tank placed at the back of the vehicle in most FCV models. Hydrogen is stored in compressed form. Some vehicle models include a fuel processor to transform the fuel to a hydrogen-rich gas for production of electrical energy in the fuel cell. The electricity that is produced is controlled by a power electronics package, which transfers electricity to any of the traction motors for propelling the vehicle.
At minimum, the FCV has a battery for start up, however, some models have an additional battery or storage device used as a supplementary energy source in a hybrid vehicle.
Similar to conventional engines, the fuel cell is fitted several security features owing to the dangers posed by liquid hydrogen, and from the electricity produced. For instance, it is fitted with a safety valve that prevents the reverse flow of hydrogen, averts contamination of the fuel, and ensures that the compressed gas maintains its temperature. And in case of a collision, the fuel cell automatically shuts off, stopping the flow of hydrogen and the production of electricity.
Advantages of the Fuel Cell Vehicle
As mentioned earlier, the fuel cell has a higher efficiency due to electronic control, energy loss due to friction in moving parts is minimized. An electric drive system further improves the FCV’s efficiency by retaining energy during braking, this energy is lost in gasoline-powered vehicles as they use a frictional braking system. The recaptured energy is used to charge the car battery. The benefits of an onboard fuel storage system include the moderately low molecular mass of hydrogen, which reduces the mass of the fuel. Besides, a FCV can run many miles before requiring a refill, and the simplicity refueling process (Deccico 2004).
The advantages of the fuel cell vehicle arise from hydrogen’s density as liquid hydrocarbon fuels, such as diesel and petrol, have higher energy densities than gaseous fuels such as hydrogen. Liquid hydrocarbon fuels also have higher densities than gaseous fuels.
Apart from the fuel cell, an FCV requires additional components and these include the secondary parts required for a complete fuel cell energy system. Others include the fuel tank and electronic systems. Secondary parts include the blower, heat exchangers, and other parts required to control the heat and mass flows (Deccico 2004).
Many automobile companies are currently engrossed in feasibility studies towards the use of hydrogen for powering vehicles. Companies such as Chevrolet, Hyundai, Toyota, Daimler and Mercedes-Benz are already testing their FCV prototypes before a final roll out in the next two or three years. Hyundai has already announced that it will begin selling FCVs in 2012 while Toyota and the rest of the firms plan to roll out their vehicles in 2015. The firm has stated that it will build 500 cars in 2012 and hope to increase this figure to 10,000 in 2015.
FCVs have several advantages over regular cars: they do not release carbon dioxide, have higher efficiency, hydrogen is cheaper that hydrocarbon fuels, hydrogen is renewable and is easily available. Therefore, FCVs are a solution to the global warming crisis and high costs of fuel.
Decicco, J. M. (2004). Fuel Cell Vehicles. Encyclopedia of Energy, Volume 2, 759-770.
Von Helmolt, R., and Eberie, U. (2007). Fuel Cell Vehicles: Status 2007. Journal of Power Sources, Volume 165(2), 833-843.
Weiss, M. A., Heywood, J. B., Schafer, A., Natarajan, V. K. (2003). Comparative Assessment of Fuel Cell Cars. MIT LFEE, 2003-001 RP.