How A Fuel Cell Electric Vehicle Works
You probably know about battery-electric vehicles and plug-in hybrids, but have you heard about fuel cell vehicles? Fuel cell vehicles are powered entirely by electricity, thus they are categorized as electric vehicles (EVs). But other than the environmental benefits of driving on electricity, this late generation of fuel cell electric cars have marked differences compared to the EVs that we know, and interestingly, share similar range and refueling processes with conventional cars and trucks.
Hyundai first launched a hydrogen fuel cell electric vehicle in the United States in June 2014, followed by Huyndai and Toyota, with more manufacturers expected to introduce more offerings in the coming years. Fuel cell vehicles are the new kid on the block, and the debates among major automakers about whether they are superior to conventional EVs, or their applications, are ongoing. Read on to find out how fuel cell vehicles work, their advantages and disadvantages compared to regular vehicles as well as electric vehicles, and what their future looks like to keep your automotive industry knowledge up to date.
The Birth of Fuel Cell Vehicles
Reducing emissions has long been a commitment shared by most major global car manufacturers. Before the birth of fuel cell vehicles, battery-electric vehicles (BEVs) like the Tesla Model 3 and Chevrolet Bolt had been the absolute winner in the arena of green cars, with zero tailgate emission vehicles and powered entirely by electricity, part of which comes from smart regenerative braking systems.
While a few major automakers like Volkswagen still believe that battery-electric vehicles are greener and more energy efficient than the new hydrogen fuel cell vehicle, many others remain staunch advocates of fuel cell vehicles’ zero-emission technology and their potential applications outside of passenger cars.
Some advocates of fuel cell vehicles are Honda, Toyota and Hyundai. They have been offering fuel cell vehicles in the United States, while Honda and Toyota don’t even sell their battery-electric cars here. Due to the newness of these cars and their big price tag, so far only California has fueling stations, so it would be a while until we’d see more fuel cell cars on the road.
How A Fuel Cell Vehicle Works
Fuel cell vehicles also draw electricity from an onboard battery pack to power an electric motor like all pure electric or battery-electric vehicles. Just like conventional EVs, this battery pack stores both excess electricity and the energy captured as heat from braking through a process called regenerative braking.
The difference is while other electric vehicles draw power from the battery pack only, fuel cell vehicles also draw power directly from a fuel cell powered by hydrogen and oxygen. The size of the hydrogen fuel tank of a fuel cell vehicle determines the amount of energy stored onboard, while for a pure electric vehicle, the amount of energy available is determined by the battery’s size.
In a fuel cell vehicle, the battery is used for recapturing energy from braking, and this captured energy is used during short accelerations to provide some extra power. During low power needs, the fuel cell can be turned off or idle, and the vehicle will be drawing power stored in the battery.
The amount of electricity available in a fuel cell vehicle equals the power produced from the hydrogen tank plus the energy stored in the battery pack. The power of a fuel cell vehicle is defined by the manufacturer as the size of the electric motors, which draw power from the combination of the battery pack and the fuel cell.
A difference from plug-in hybrids is that the current models of fuel cell cars do not have plug-in capability to charge the battery.
Hydrogen as an Abundant Source of Alternative Fuel
Hydrogen as an alternative fuel received attention and research later than solar and wind power. As a source of fuel, it has a very high energy content by weight. Hydrogen is also the most common element on earth.
Hydrogen in its isolated state is a highly flammable gas, but in nature, it rarely exists as a single element. It most often combines with other elements to form compounds, and can be found in enormous quantities in water, hydrocarbons like oil and natural gas, and countless other organic matter.
This means that hydrogen gas to be used as a fuel source for automobiles needs to be manufactured. Hydrogen fuel can be manufactured from many resources including biomass, fossil fuels, and derived from water by the process of water electrolysis, which in turn uses grid electricity or wind or solar energy.
There are refueling stations where hydrogen gas is made by water electrolysis, that is splitting water into hydrogen and oxygen. In other words, although hydrogen is greener than traditional fuel, how hydrogen gas is produced and how it is transported to refueling stations decides how green and how energy efficient it’s actually is compared to other alternative fuels..
Key Components of a Fuel Cell Electric Car
- Fuel cell: An electrochemical cell, or an assembly of individual electrodes, that converts the chemical energy of hydrogen and an oxidizing agent, that is oxygen to produce electricity. Fuel cells are similar to batteries in the way that they produce power without combustion or emissions.
- Hydrogen fuel tank: Hydrogen gas is stored onboard in a tank until it’s needed by the fuel cell. It’s hard to maintain hydrogen as a gas at normal room temperature and pressure, so the tank is pressurized and designed to store hydrogen in the gas state.
- Traction battery pack: This is called the traction battery and to be distinguished from the auxiliary battery. The traction battery provides power to run the motors to propel the vehicle forward with torque and stores electricity generated from regenerative braking.
- Auxiliary battery: The auxiliary battery provides electricity to run various electrical accessories in the vehicle like dome light and radio, and provides power to start the car before the traction battery pack is engaged.
- Electric traction motor: This motor drives the vehicle’s wheels using electrical power stored in the traction battery pack as well as power generated by the fuel cell using hydrogen and oxygen. Some fuel cell models use motor generators, which also perform the function of energy regeneration from braking.
- Power electronics controller: As the name suggests, the controller regulates the flow of electricity from the fuel cell and the traction battery as well as managing the speed of the motor and the torque it produces.
- Cooling system: Like in all vehicles, the cooling system is a crucial part and makes sure that every vital component operates within a safe, optimal temperature range, including the fuel cell, the electric motor, the power controller and many others.
- Electric transmission: Again, like in all vehicles, the transmission in a fuel cell vehicle transfers mechanical power from the motor to drive the wheels.
Features of Fuel Cell Vehicles
Unlike plug-in electric vehicles to connect to a power outlet to charge, a fuel cell vehicle requires refueling, which is comparable to that of a conventional car or truck. The hydrogen fuel is stored in a pressurized tank designed specifically for the purpose of maintaining hydrogen in the gas state. The fuel filler is more high-tech than the regular gasoline pump nozzle at gas stations, which makes hydrogen refueling a bit more complicated than putting gas in a conventional vehicle, but only slightly so, and the process takes a comparable amount of time, less than 10 minutes to fill current models.
A full refill might offer varying driving ranges among the different fuel cell car models, but on average, this type of electric car offers longer driving ranges than full-electric cars and plug-in hybrids, that is between 200 and 300 miles, comparable to the ranges of vehicles that run on traditional gasoline or diesel.
This means that fuel cell vehicles are more ideal for larger vehicles that often travel long distances, such as commercial trucks. It’s also worth considering for drivers who lack the appropriate plug-in access at home to charge their EVs efficiently.
Like other EVs, fuel cell vehicles can draw energy stored in the traction battery instead of the fuel cells during instances of low power needs like stopping at traffic lights. During these idle-off situations, the fuel cells are put into idle or shut down. Another common feature is the regenerative braking function that recaptures valuable energy that otherwise would be lost as heat.
Advantage: Cutting Emissions
The process of converting hydrogen gas into automotive fuel produces only water and heat as a byproduct, which means fuel cell vehicles are as green as all-electric vehicles when it comes to zero tailpipe emissions.
As above, remember that the process of hydrogen production itself can create greenhouse gas emissions and other pollutants, and the manner by which hydrogen gas is manufactured and transported to refilling stations might make hydrogen fuel less clean than they appear. That said, even when the hydrogen fuel is made from one of most polluting sources of fuel like natural gas, the early generations of fuel cell vehicles on the road today can still cut emissions by over 30% compared to their gas- and diesel-powered counterparts.
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While all these benefits sound very promising, fuel cell vehicles won’t dominate the road just yet. One reason is that fuel cells compact enough to power a vehicle are very expensive to manufacture, although recently the cost has decreased by a small margin thanks to technological advancement. That said, as fuel cell vehicles gain more public awareness and popularity, the production of fuel cell vehicles should scale up and drive down manufacturing cost.
Disadvantage: Availability of Refueling Stations
Because fuel cell vehicles are quite new, you might have limited access to hydrogen refueling stations. These vehicles only began to enter the US market in recent years, and nearly all of the tiny number of refueling stations here are located in the larger urban areas of California, so interested drivers living elsewhere will have to wait. But wait for how long is a chicken-and-egg problem: should we invest in more hydrogen delivery infrastructure and refilling stations with the anticipation that more fuel cell vehicles will be produced, or should there be enough of these vehicles on the roads to justify investments in infrastructure?
Disadvantage: Shorter Lifespan
On top of being expensive, fuel cells (and electric motors) are less durable than gas- and diesel-powered engines, which makes the initial upfront cost of fuel cell vehicles even harder to swallow.
Energy Efficiency: Fuel Cell vs Battery-Electric Vehicles
Although both battery-electric cars and fuel cell vehicles use electricity for propulsion, the process of power generation is different, so different fractions of the electricity generated by the grid is actually applied to propulsion. , while fuel-cell cars store it in gaseous hydrogen, releasing it through a chemical reaction in the cells.
Battery-electric cars store that electricity directly in their battery packs. A recent study by management consultancy Horváth & Partners shows that battery-electric cars have a very high energy efficiency of 70% to 80%. About 8% of the power generated is lost in transmission from the source to the car’s battery pack, and about 18% of the remaining power is further lost on the way from the battery to the drive wheels. Still, the majority of the power generated by the grid, that is about three quarters, makes it to the wheels to run the car.
Meanwhile, a fuel cell electric car only has an efficiency of 25% to 35%. This is mostly attributable to the fact that about 45% of the generated energy must be used to produce usable gaseous hydrogen through a chemical reaction in the cells, with water electrolysis currently being the most common method. Of the remaining potential energy, another 55% is lost during the process of converting hydrogen into electrical power within the fuel cell.
The Future of Fuel Cell Vehicles
As above, while advocates of battery-electric cars often cite their superior energy efficiency to prove that they are more ideal than fuel cell vehicles as a type of zero-emission vehicle, supporters of fuel cell cars often refer to their long driving range. All fuel-cell cars currently sold in the United States by Honda, Toyota and Huyndai offer a range of 300 miles and above, something that only a handful of Tesla battery-electric models can achieve.
While some traditional EVs advocates like Volkswagen believe that battery-electric cars will soon be able to match this long driving range, not every automaker agrees, however.
Many manufacturers, including Toyota, Honda and Huyndai, expect that the cost of fuel-cell powertrains will become more affordable as production scales up. The direction that many are making is to look at a bigger picture than just cars and in the direction of commercial vehicles, such as heavy-duty transport like commercial trucks, aviation, and shipping, since hydrogen fuel is more suitable for large machines and long-distance transport.
Honda just partnered up with Isuzu on fuel-cell development. Isuzu do offer passenger cars, but now commercial trucks make up the majority of its business.