A fuel cell is a device that generates electricity by a chemical reaction. It converts hydrogen and oxygen into water, and in the process also creates electricity. Fuel cells provide many advantages, they are environment friendly as they don’t produce pollutants or greenhouse gasses, significantly improving our environment, high energy efficiency ( can be close to 80% where they generate both heat and electricity), scalable providing power from milliwatts to megawatts, and complementary i.e. readily be combined with other energy technologies, such as batteries, wind turbines, solar panels, and super-capacitors.
In just the last two years, Toyota, Hyundai and Honda have released vehicles that run on fuel cells, and carmakers such as GM, BMW and VW are working on prototypes. The Japanese have invested more than AUD $16 billion (USD $12 billion) on hydrogen research and development and are looking to deploy at least 6,000 fuel-cell cars and 100 buses in Tokyo for the 2020 Olympics. In 2016, South Korea announced plans to switch 26,000 buses from compressed natural gas to hydrogen. And in July 2018, the country’s Ministry of Trade, Industry and Energy pledged to establish special-purpose companies to speed up the rollout of hydrogen fueling stations.
In July 2018, ARENA announced AUD $1.5 million (USD $1.1 million) for a green hydrogen innovation hub at Jandakot, Western Australia. There, the gas company ATCO will trial the production, storage and use of renewable hydrogen in a commercial-scale microgrid. Green hydrogen will be produced from on-site solar using electrolysis, fueling a range of appliances after being blended into a natural gas pipeline, ARENA said.
However, compared to electric vehicles, “hydrogen hasn’t really taken off,” said Timotej Gavrilovic, a contributing analyst at Wood Mackenzie Power & Renewables. “The number of hydrogen-based vehicles has been pretty small.”And with battery-powered electric vehicles still only slated to have a penetration of around 10 percent by 2030, the chances of a major boom in fuel-cell cars by the same time is small.
Fuel cells can also extend the operating range and mission of military systems by reducing the dependence on carbon-based fuel sources. They also save energy and reduce the operating costs associated with dependence on foreign oil. “As the U.S. moves to reduce its dependence on foreign oil and become more energy efficient, this technology may well define the future of power and energy for the war fighter,” writes ONR.
There are many types of fuel cells, and each can operate in a clean manner using different fuels including hydrogen, natural gas, methanol, ethanol, biogas. All fuel cells, consist of an anode, a cathode, and an electrolyte that allows positively charged hydrogen ions (or protons) to move between the two sides of the fuel cell. The reactions that produce electricity take place at the electrodes.
Every fuel cell also has an electrolyte, which carries electrically charged particles from one electrode to the other, and a catalyst, which speeds the reactions at the electrodes.
Fuel cells are classified primarily by the kind of electrolyte they employ. This classification determines the kind of electro-chemical reactions that take place in the cell, the kind of catalysts required, the temperature range in which the cell operates, the fuel required, and other factors. These characteristics, in turn, affect the applications for which these cells are most suitable.
The six fuel cell types are : PEMFC, Proton Exchange Membrane Fuel Cell, DMFC, Direct Methanol Fuel Cell, PAFC, Phosphoric Acid Fuel Cell, AFC, Alkaline Fuel Cell, MCFC, Molten Carbonate Fuel Cell and SOFC, Solid Oxide Fuel Cell.
Individual fuel cells produce relatively small electrical potentials, about 0.7 volts, so cells are “stacked”, or placed in series, to create sufficient voltage to meet an application’s requirements. The energy efficiency of a fuel cell is generally between 40–60%, or up to 85% efficient in cogeneration if waste heat is captured for use.
Fuel cell challenges
The high capital cost for fuel cells is by far the largest factor contributing to the limited market penetration of fuel cell technology. In order for fuel cells to compete realistically with contemporary power generation technology, they must become more competitive from the standpoint of both capital and installed cost (the cost per kilowatt required to purchase and install a power system).
The primary fuel used in a fuel cell is hydrogen, which can be obtained from natural gas, gasoline, coal-gas, methanol, propane, landfill gas, biomass, anerobic digester, gas and other fuels containing hydrocarbons. Fuel cells must be developed to use widely available fossil fuels, handle variations in fuel composition, and operate without detrimental impact to the environment or the fuel cell.
Increasing the fuel flexibility of fuel cells implies that power generation can be assured even when a primary fuel source is unavailable. This will increase the initial market opportunities for fuel cells and enhance market penetration.
Although fuel cells have been shown to be able to provide electricity at high efficiencies and with exceptional environmental sensitivity, the long-term performance and reliability of certain fuel cell systems has not been significantly demonstrated to the market. Fuel cells could be great sources of premium power if demonstrated to have superior reliability, power quality, and if they could be shown to provide power for long continuous periods of time.
Researchers are engaged in creating many breakthroughs in technology development to make fuel cells competitive with other advanced power generation technologies. Some of the breakthroughs technologies are: New fuel cell types, Contaminant tolerance (CO, sulfur), New fuel cell materials (electrolyte, catalyst, anode and cathode) and New balance of plant (BOP) concepts (reformers, gas clean-up, water handling, etc.).
Researchers discover new materials to make fuel cells more durable, less expensive
Platinum is the most common catalyst in the type of fuel cells used in vehicles. However, platinum is expensive — as anyone who’s shopped for jewelry knows. The metal costs around $30,000 per kilogram. Instead, the UD team made a catalyst of tungsten carbide, which goes for around $150 per kilogram. They produced tungsten carbide nanoparticles in a novel way, much smaller and more scalable than previous methods.
“The material is typically made at very high temperatures, about 1,500 Celsius, and at these temperatures, it grows big and has little surface area for chemistry to take place on,” Vlachos said. “Our approach is one of the first to make nanoscale material of high surface area that can be commercially relevant for catalysis.”
The researchers made tungsten carbide nanoparticles using a series of steps including hydrothermal treatment, separation, reduction, carburization and more. “We can isolate the individual tungsten carbide nanoparticles during the process and make a very uniform distribution of particle size,” Zheng said.
Next, the researchers incorporated the tungsten carbide nanoparticles into the membrane of a fuel cell. Automotive fuel cells, known as proton exchange membrane fuel cells (PEMFCs), contain a polymeric membrane. This membrane separates the cathode from the anode, which splits hydrogen (H2) into ions (protons) and delivers them to the cathode, which puts out current.
The plastic-like membrane wears down over time, especially if it undergoes too many wet/dry cycles, which can happen easily as water and heat are produced during the electrochemical reactions in fuel cells. When tungsten carbide is incorporated into the fuel cell membrane, it humidifies the membrane at a level that optimizes performance. “The tungsten carbide catalyst improves the water management of fuel cells and reduces the burden of the humidification system,” Wang said. The team also found that tungsten carbide captures damaging free radicals before they can degrade the fuel cell membrane. As a result, membranes with tungsten carbide nanoparticles last longer than traditional ones.
“The low-cost catalyst we have developed can be incorporated within the membrane to improve performance and power density,” Prasad said. “As a result, the physical size of the fuel cell stack can be reduced for the same power, making it lighter and cheaper. Furthermore, our catalyst is able to deliver higher performance without sacrificing durability, which is a big improvement over similar efforts by other groups.”
A team of Brown University scientists has developed a new catalyst that could make hydrogen fuel cell-powered vehicles more economical. Based on nanoparticles made of an alloy of platinum and cobalt, the new catalyst is not only cheaper than pure platinum, but is also more efficient and longer lasting. According to team leader Junrui Li, alloying platinum with metals like cobalt is cheaper and makes the catalyst more efficient, but the base metal quickly oxidizes inside the harsh conditions of the fuel cell and leeches away.
To prevent this, the Brown team created nanoparticles consisting of an outer layer of pure platinum and an interior built up of alternating layers of platinum and cobalt atoms. “The layered arrangement of atoms in the core helps to smooth and tighten platinum lattice in the outer shell,” says says Shouheng Sun, professor of chemistry. “That increases the reactivity of the platinum and at the same time protects the cobalt atoms from being eaten away during a reaction. That’s why these particles perform so much better than alloy particles with random arrangements of metal atoms.” Tests of the new catalytic nanoparticles show that they already out-perform platinum and remained active after 30,000 voltage cycles – a point at which platinum drops off radically.
New Technology Facilitates Hydrogen Storage
MAN Cryo, shipowner Fjord1 and designer Multi Maritime in Norway have developed a marine fuel-gas system for liquefied hydrogen. The system is designed for vessels, such as ferries, employed on relatively short routes and has been granted preliminary approval in principle by DNV GL. It is the first marine-system design globally to secure such an approval. The system has a scalable design and is suited for both above- and below-deck applications.
Liquefied hydrogen has a temperature of -253° Celsius and is one of the coldest cryogenic gases there is, which places system components and materials under extreme stresses. Another design challenge was hydrogen’s explosive nature. Once liquefied, hydrogen is reduced to 1/800th of its volume, compared to that of its gas phase, facilitating a more-efficient distribution. As a fuel, hydrogen does not release any CO2, and liquefied hydrogen can be used to charge batteries for electrical propulsion via fuel cell technology.
Some 55 million tons per annum (Mtpa) of hydrogen is currently made every year for industrial feedstock, mostly for oil refining and making chemicals. In contrast, only 0.002 percent of hydrogen production, about 1,000 tons annually, is produced for use as an energy source. Most, if not all, of this currently powers hydrogen fuel-cell electric vehicles.
A newly-released research paper by DNV GL Hydrogen as an energy carrier predicts significant long-term rises in these numbers, with low-carbon hydrogen becoming an effective decarbonization agent to mitigate climate change. For example, the company’s experts estimate that demand in 2050 for hydrogen solely for energy could range from 39–161 Mtpa.
Converting Natural Gas to Hydrogen for Clean, Efficient Transportation
Scientists at the Commonwealth Scientific and Industrial Research Organisation (CSIRO), in Canberra, unveiled a membrane technology that separates ultra-high purity hydrogen from ammonia, while blocking all other gases. The development is seen as a major step in overcoming a drawback for renewable hydrogen: the fact that it is difficult and costly to store and move around. “This technology will pave the way for bulk hydrogen to be transported in the form of ammonia, using existing infrastructure, and then reconverted back to hydrogen at the point of use,” said CSIRO in a press release. Scientists are now testing the fuel-cell-powered Toyota Mirai that uses ultra-high purity hydrogen, produced using CSIRO membrane technology.
Ammonia (NH3) has a high capacity for storing hydrogen atoms—17.6% by weight, and at a volumetric density 45% greater than liquid H2. It has often been proposed as a carrier method, given that it’s stable and can be stored in pressure tanks in much the same way as propane or other fuels. Yet the large amount of energy needed to create and/or separate ammonia molecules and unfavorable economics has discounted any further practical use—until now.
The key to the CSIRO project rests in a different approach based on a proprietary membrane separator technology designed by Dr. Michael Dolan. Its vanadium-alloy membrane is tipped to transform the hydrogen separation process, as well as enable the use of ammonia as a means of carrying the ultralight hydrogen. The ammonia is stored in the tank at ambient temperature. Therefore, most of the ammonia is a liquid. However, some vaporizes, which creates a pressure in the tank of 5 to 10 atmospheres, depending on the temperature. Vapor from the tank is then heated to 400°C and passes through a catalyst bed that then decomposes ammonia into nitrogen and hydrogen gas.
That mixture is subsequently passed over the membrane. The thin metal membrane allows hydrogen to pass while blocking all other gases including nitrogen, and using decomposed ammonia feedstock, it enables H2 conversion in a single step. It permits a small plant—with no moving parts—to work in continuous operation.
Dr. Dolan says “Our design philosophy has been to use inexpensive materials and mass-production techniques (like metal tube extrusion and electroplating) as much as possible. The membrane substrate itself is a dense tube of a permeable, inexpensive [vanadium] alloy which is drawn down to a wall thickness of ~0.2 mm, and diameter of 10 mm. A catalytic layer is then deposited on the inner and outer surfaces.”
The membrane breakthrough comes amid growing interest in exporting hydrogen from Australia to Asian markets, and predominantly Japan, which leads the way worldwide in the deployment of fuel-cell vehicles. At present, hydrogen is produced using fossil fuels. But advocates hope to use surplus energy from Australia’s growing solar and wind industries to provide the power for hydrogen production. Last month, the Australian Renewable Energy Agency (ARENA) published a vision of renewably sourced hydrogen being exported to Japan.
Earlier, a team of scientists from CoorsTek Membrane Sciences, the University of Oslo (Norway) and the Instituto de Tecnología Química (Spain) successfully completed laboratory testing of a ceramic membrane that generates compressed hydrogen from natural gas and electricity in a one-step process with near zero energy loss. The ceramic membrane makes production of hydrogen from abundant, low-cost natural gas so efficient that it will make hydrogen the cleanest and least expensive option for future automotive fueling — surpassing both electricity and petroleum.
CoorsTek ceramic membrane technology enables compact hydrogen generators to enable anyone with access to natural gas to easily and inexpensively fuel a hydrogen vehicle at home. This makes it possible for hydrogen-fueled vehicles to run cleaner and cheaper than battery or petroleum fueled automobiles.
The present membrane is made from oxides of abundant materials (including barium, zirconia, and yttrium), forming a solid ceramic electrolyte that can transport hydrogen in the form of protons at temperatures from 400 to 900 °C. By applying an electric potential over the ceramic cell, hydrogen is not only separated from other gases but also electrochemically compressed.
“By combining an endothermic chemical reaction with an electrically operated gas separation membrane, we can create energy conversions with near zero energy loss”, explains Dr. Jose Serra, Professor with Instituto de Tecnología Química (ITQ) in Valencia, Spain, a leading research lab for hydrocarbon chemistry and a co-author of the report in Nature Energy.
Energy Department awarded professor over $600,000 for hybrid fuel cell development
The Department of Energy awarded Dustin McLarty, a mechanical and materials engineering assistant professor, $678,000 to research hybrid fuel cells as part of its Advanced Research Projects Agency – Energy, or ARPA-E, project.
McLarty defined his power system design as a “breaching technology.” He said it could work with natural gas today — while it is still abundant — or synthetic fuels in the future. He said just about any fuel would work once the temperatures at which the system operates are considered.
“High-temperature fuel cells have operated on biogases, landfill gases, gases from wastewater treatment facilities, regular old natural gases,” McLarty said, “just about anything that can be a fuel can be used by this.”
McLarty is working to improve hybrid power systems by using solid oxide fuel cells, or SOFCs. His design uses a very thin ceramic tile with pressurized fuel on one side and air on the other. The gases mix, triggering a reaction that releases energy in the form of heat and electricity.
Scientists can control where electrons go in the fuel cell, enabling them to convert more energy into electricity and less into heat. This is an important aspect because heat released from the reaction cannot power technology. McLarty’s new system design added what is called an oxygen membrane, separating the gas turbine from the fuel cell. “This allows for the turbine to power up and down independently of the fuel cell powering up and down,” McLarty said. McLarty said the design has a lot of potential for development.
“ARPA-E is very focused on the commercialization pathway,” McLarty said, “and with success, it would be something the university could license out or spin out as a startup company through the university incubator.”
DOE and TARDEC to collaborate on hydrogen and fuel cells for military use
The US Department of Energy (DOE) and the US Army signed a memorandum of understanding to collaborate in the development of hydrogen and fuel cell technologies for military and civilian use. Army TARDEC is the United States Armed Forces’ research and development facility for advanced technology in ground systems. Research is underway at Army TARDEC to develop fuel-cell-powered vehicles for tactical uses, among other activities.
The Energy Department’s Fuel Cell Technologies Office (FCTO), within the Office of Energy Efficiency and Renewable Energy, focuses on advancing an innovative portfolio of hydrogen and fuel cell technologies through early-stage applied research and development (R&D) of technologies. This R&D includes hydrogen production from diverse domestic resources including renewable, fossil, and nuclear resources, infrastructure development including hydrogen delivery and storage, and fuel cells for transportation, stationary, and mobile applications.