Toyota, maker of the pioneering Prius hybrid, has decided that they aren’t going to build an all electric vehicle. They’re going to throw their considerable research and development might behind producing a hydrogen fuel cell vehicle. The US government is also a firm believer in the future of the fuel cell and has a goal of making the technology practical for family car use by 2020. Fuel cell powered vehicles are already on the road in limited numbers and fuel cells are becoming common in industrial applications like forklifts. In fact, Walmart started using fuel cell powered forklifts in its distribution centers in 2006. But, what is a hydrogen fuel cell, how does it work, and what are the limitations?
First, a Bit of History
Fuel cells have been around for a very long time. They were invented by Sir William Grove in 1839. Scientists already knew that water could be split into hydrogen and oxygen by passing electricity through it. Groves reasoned that you could reverse the process to create electricity and water from hydrogen and oxygen. Groves was able to create a primitive fuel cell called a gas voltaic battery. 50 years later, Ludwig Mond and Charles Langer coined the term fuel cell.
The first fuel cell powered vehicle was a modified Allis-Chalmers tractor fitted with a 15 kilowatt fuel cell in around 1959. Fuel cells were used in the Gemini and Apollo space programs to provide power to the spacecraft. In 1966, General Motors developed the Chevrolet Electrovan that used a Polymer Electrolyte Membrane Fuel Cell (PEMFC) and had a range of 120 miles and top speed of 70 mph. The fuel cell stack took up the entire rear of the van and only one was ever built. During the 1980’s, the US space program’s use of fuel cells continued on the Space Shuttle.
There are several different types of fuel cells but the Polymer Electrolyte Membrane Fuel Cell (FEMFC) is currently the most practical type for automotive use. It converts hydrogen and oxygen into water and in the process generates electricity without creating pollution. Unlike a battery, a fuel cell never goes dead. As long as hydrogen and oxygen flow into it, it will continue to produce electricity. One of the advantages of the FEMFC is its relatively low operating temperature – 60 to 80 degrees C (140 – 176 degrees F). Some fuel cells operate at very high temperatures – up to 1000 degrees C.
How is a Fuel Cell Made?
An FEMFC uses a relatively simple reaction to generate electricity and has four basic components:
Anode – negative post of the fuel cell. As electrons are stripped from hydrogen atoms by the reaction that occurs inside the fuel cell, they are conducted by the anode to the motor. The anode has channels etched into its surface so that hydrogen can disperse evenly over the surface of the catalyst.
Cathode – the positive post of the fuel cell. Like the anode, the cathode has channels etched into its surface so oxygen can spread evenly over the entire surface of a catalyst. Electrons flowing through the anode and the electric drive motor return to the fuel cell through the cathode where they are recombined with hydrogen ions and oxygen to form water.
Electrolyte – proton exchange membrane that looks sort of like kitchen wrap. It only allows positively charged ions to pass through but blocks electrons. The electrolyte must be kept wet in order to work properly.
Catalyst – usually made of a thin layer of platinum particles applied to one side of carbon paper or cloth. The catalyst is what causes the reaction of hydrogen and oxygen that generates electricity and water.
How does it Work?
Pressurized hydrogen gas enters the anode (negative) side of the fuel cell where it’s forced through the catalyst. When a hydrogen molecule comes into contact with platinum, it’s split into two positively charged ions and two negatively charged electrons. The electrons are conducted through the anode and go off through the external circuit to power the motor. They then return to the cathode (positive) side of the fuel cell. Meanwhile, on the cathode side of the fuel cell, oxygen molecules are being forced through a catalyst where they are split into two oxygen atoms, each with a strong negative charge. The negatively charged oxygen atoms attract two hydrogen ions through the polymer electrolytic membrane and two electrons to form a molecule of water.
A single fuel cell only produces about .7 volt of electricity and can be small enough to fit in the palm of your hand. In order to power something like a car, many separate fuel cells must be combined or stacked to produce a usable amount of voltage. That’s when things get really complicated and expensive.
How Efficient is a Fuel Cell?
Fuel cells that use pure hydrogen are about 80% efficient, meaning that about 80% of the energy potential of the hydrogen is converted into electricity. Some energy is wasted when the electricity is run though an inverter and used to power a motor. Some fuel cell systems use a reformer to convert hydrocarbon or alcohol fuels into hydrogen. Systems like this are less efficient and generate heat and other gases besides hydrogen. A vehicle powered by a fuel cell is about 64% efficient as compared to 20% for a traditional car with an internal combustion engine. Pure battery powered cars are about 72% efficient if the electricity used to charge them is hydroelectrically generated. If the electricity used to charge their batteries is generated by fossil fuels, their efficiency falls to about 26% or less.
What’s the Hold Up?
There’s no doubt that the fuel cell has incredible potential as a source of power for automobiles. However, the technology is still very expensive although as with everything, the price will come down as more companies start to jump on the fuel cell powered band wagon.
Another challenge is making fuel cells that can operate efficiently at temperatures over 100 degrees C. but that work well when the outside temperature is below zero, for example in most of Canada during the winter.
Fuel cell durability is also an issue at the moment. The Polymer Electrolyte Membrane has to remain stable when the fuel cell cycles on and off frequently, which happens during stop and go driving. Cycling is hard on fuel cells, especially when they get hotter.
As well, the infrastructure needed for hydrogen fuel cells is in its infancy. A hydrogen generation and distribution system has to be designed and built. That might mean hydrogen pipelines, transporting hydrogen by truck or train, and more hydrogen generating plants. There is a well developed network of hydrogen filling stations in Europe but they are just beginning to come online in North America. California is leading the way with about 50 stations in place or currently under construction. It’s estimated that up to $500 billion will be needed to build the infrastructure needed to make fuel cells a viable energy source. In contrast, the infrastructure for electric vehicles already exists and they can be plugged in and charged just about anywhere.
Hydrogen is the most abundant element in the universe and hydrogen fuel cells are non polluting. However, it’s important to recognize that even though a battery or fuel cell powered vehicle doesn’t produce emissions, it’s not necessarily 100% “green.” That’s because the electricity used to charge the batteries or to free hydrogen from water using electrolysis could be generated at a fossil fuel fired power generating station.
Will you be Driving a Hydrogen Powered Vehicle?
Most of the major automobile manufacturers are working on their own hydrogen fuel cell powered vehicles. Once the costs have come down and a filling infrastructure has been built, hydrogen truly could become the fuel of the future. In the meantime, you can do your part to make the world a greener place by driving an electric vehicle like the Nissan Leaf, the best selling electric vehicle in the world. The 2015 Leaf has arrived at Kelowna Nissan. Come down and find out for yourself how exhilarating (and economical) zero emission driving can be.