A green car is a vehicle that is more environmentally friendly than traditional models. Green cars produce lower levels of harmful emissions; some types produce no pollutants at all. The fuel source is a major consideration when deciding whether a vehicle merits the description of a green car. The vehicles also use an alternative to petroleum-based products to supply all or part of the fuel needed to power its engine.
Types of Green Cars
Over the years, automakers have invested significant amounts of both time and capital to produce green cars, resulting in a variety of vehicles using alternative fuels.
- Electric vehicles (EVs) have electric motors that use rechargeable battery packs to supply their power. Battery packs can be plugged into a regular household outlet or a charging dock to be recharged; a charging dock greatly reduces the charging time.
- Hybrid electric vehicles (HEVs) have both a traditional internal combustion engine and an electric motor. At low speeds, the electric engine supplies the power, and the batteries recharge while driving rather than through an outlet or charging dock.
- Plug-in hybrid electric vehicles (PHEVs) have an internal combustion engine as a back-up, but they are powered primarily by an electric motor that runs on internal batteries. Drivers connect to a regular outlet or charging station to recharge the batteries.
Automakers have engineered some excellent green cars, but the public still has some concerns. One of them is “range anxiety”. Although some electric vehicles can be driven for more than 100 miles before they need to be recharged, there are consumers who consider this range to be insufficient and fear being stranded if their battery pack is expended. HEVs and PHEVs reduce the need for fossil fuels, but neither type completely eliminates that dependence.
Newer technologies, however, hold more promise for eliminating range anxiety and reduce the dependence on fossil fuels. One of the newest types of green cars to be developed is the fuel cell electric vehicle (FCV, FCEV).
What Is a Fuel Cell?
Fuel cell technology uses a chemical reaction to generate electricity. The three basic components of a fuel cell are an electrolyte, an anode and a cathode.
- The electrolyte is the medium that allows electrical conductivity.
- The anode is a type of electrode that allows current to flow in, i.e., the positive terminal.
- The cathode is a type of electrode that allows positive current to flow out, i.e., the negative terminal.
The cathode draws electrons from the anode, which produces electricity in the form of direct current. The electricity is then used as a power source.
There are several types of fuel cells, and their names normally reflect the electrolyte used. Green vehicles typically us polymer exchange membrane (PEM) fuel cells as they are lightweight, compact and easily stacked.
NASA made significant use of fuel cells for space applications. The first fuel cell tests began during the Gemini missions and fuel cells were used extensively throughout the Apollo and space shuttle missions. Despite their use in space-age technology, however, fuel cells are not a 20th-century development. Humphry Davis demonstrated the basic concept early in the 19th century, and William Grove is normally credited with having invented the fuel cell in 1838.
Unlike batteries, fuel cells do not store energy for later use. They must have a constant fuel supply to power the chemical reaction. For cars, the most common power sources for fuel cells are hydrogen and oxygen.
Upsurge of Hydrogen Fuel Cell Cars
Fuel cell vehicles have actually been around for more than 50 years. The first was an Allis-Chalmers tractor that was modified around 1959 to use a fuel cell. Then in 1966, General Motors produced a prototype, the Chevrolet Electrovan, which could go 120 miles between charges. The fuel cell stack was bulky and heavy, however, and the Electrovan was deemed too costly to be commercially viable, especially since the price of gas was relatively low during that era.
Interest in fuel cell vehicles was renewed in 2008 when Honda introduced the FCX Clarity.
In the U.S., the FCX Clarity was only available to customers in Southern California and only through a lease program. Since 2009, there have been more than 20 models of FCEVs produced by various automakers as concept or demonstration vehicles and a limited number of models released to consumers.
Fuel cell vehicles are considered to be one of the most promising technologies for reducing reliance on fossil fuels as well as reducing harmful automotive emissions. Automakers are ramping up production on proven prototypes and developing new models. However, the supply of FCEVs in the U.S. is still somewhat limited although availability is expected to improve between the middle of 2015 and the end of 2016.
How do Hydrogen Fuel Cell Cars Work?
Hydrogen is the most abundant element in the universe, and it is odorless, tasteless, colorless and non-toxic. On Earth, it combines with oxygen to form water.
A hydrogen fuel cell vehicle has a storage tank for the hydrogen rather than a gas tank. The hydrogen molecules (H2) each have two hydrogen atoms. The oxygen is usually harnessed from the surrounding air.
A fuel cell consists of an anode, where hydrogen is introduced, and a cathode, where oxygen is introduced. A catalyst (most commonly platinum) is also necessary for the proper reaction to take place.
What happens at the anode:
- Hydrogen is sent to the anode in the fuel cell, which breaks the hydrogen into protons (ions) and electrons.
- The ions pass freely through the membrane, but the electrons are forced to take a different path and go around the membrane.
- While the electrons are being routed around the membrane, the electrical charge can be harnessed and routed to a high-output battery that is used to power an electric motor.
What happens at the cathode:
- Oxygen is forced into the fuel cell at the cathode.
- When the hydrogen electrons and protons arrive at the cathode, they combine with the oxygen, forming water.
Most of this water is exhausted as steam. If the hydrogen used is pure, no harmful byproducts are produced. Emissions consist of heat and water, which is why these cars are referred to as zero-emission vehicles.
Advantages and Disadvantages of Fuel Cell Technology
Just like every other type of vehicle, there are advantages and disadvantages to driving a car powered by fuel cell technology.
- The exhaust from an FCV contains no pollutants that are harmful to the air quality. The reduced carbon footprint also helps protect the ozone layer.
- Driving an FCV requires no consumption of fossil fuels, which take millions of years to form and are available in a limited amount.
- Hydrogen tanks can be refilled in as little as three to five minutes, making it faster to recharge an FCV than an EV or PHEV.
- Range anxiety is eliminated due to the ease of recharge and the extended range.
- Fuel cell vehicles are not widely available. Although automakers are planning to produce more units in the coming years, supplies are still limited, resulting in most fuel cell vehicles being shipped to just a handful of states.
- Fuel cell vehicles are expensive to make and therefore expensive to own. For example, platinum is the most commonly used catalyst in a fuel cell. Currently, the costs are too prohibitive for most Americans to purchase these vehicles outright, so automakers are offering them on a lease basis only.
- Hydrogen fueling stations are not yet plentiful. Currently, most of these stations are located in California. Many states have plans to build hydrogen fueling stations over the next few years, however.
- Hydrogen can be tricky to store as well as transport. It is ultra-light, so it is difficult to contain. It is also flammable. However, the Society of Automotive Engineers and the U.S. Department of Transportation have established extremely stringent requirements for vehicle storage tanks as well as refueling stations. Thus, FCVs are considered safe to operate and refuel although there is some potential for hazard if the hydrogen is allowed to escape.
Ever since the first automobiles were introduced, Americans have relied on their cars to commute to their jobs, take care of their errands and drive to vacation spots. Simply put, they love the freedom that their cars provide, and they are not likely to surrender that mobility willingly.
At the same time, however, there is a growing movement in the U.S. to end dependence on fossil fuels and reduce emissions that are damaging to the environment. It is within the realm of possibility that by the turn of the next century, there could be a hydrogen fuel cell vehicle in the driveway of every car owner.
What do you think about hydrogen fuel cell cars? Would you be interested in owning one?
Whatever the future might hold, it will take time before FCVs claim a significant share of the market. The infrastructure is not yet in place to support the operation of FCVs on a wide scale. Although automakers are researching ways to produce FCVs at a lower cost, such as by substituting less expensive materials for the platinum catalysts, the purchase costs are still beyond the reach of most citizens. There is also the problem of availability.
Many automakers are planning to increase their output of FCVs between 2015 and 2017, but available units are likely to be numbered in the thousands. Therefore, it remains to be seen just how much of an impact hydrogen cars will have during the next decade.