Gerard Hillenbrand, P.E.
ASME’s Fifth International Fuel Cell Conference was held June 18 to 20th, 2007 at the Marriott Hotel in downtown Brooklyn across the street from Polytechnic University. This conference was attended by hundreds of scientists, engineers, technologists and industry representatives from all over the world, as well as personnel from the U. S. Federal Government and various state agencies. ASME’s Met section also sent several delegates and these delegates were enthusiastically involved in all the conference’s major activities. The major sponsors of this conference included the New York State Energy Research and Development Authority (NYSERDA), the Connecticut Clean Energy Fund, the New York State Power Authority, Keyspan, Polytechnic University, The University of Connecticut and the National Fuel Cell Research Center at the University of California in Irvine, CA.
The conference’s agenda consisted of 38 individual sessions, which may be categorized into four major categories:
- Low temperature fuel cells, which emphasize the technology of portable transport systems including hydrogen production, biological materials, nano-technology, fuel storage, liquid electrolysis, and manufacturing advances.
- High temperature fuel cells which cover such topics as electrode design, high performance electrolytes, high-temperature fuel and seals as well as stacking modeling.
- Fuel cell economics covering low and high temperature systems, electric power production and non-stationary and hybrid systems.
- Fuel cell environmental and regulatory issues including significant case studies, various business strategies for manufacturers and suppliers and guidelines for fuel cell entrepreneurs.
ASME also published a book of abstracts of the many technical papers presented at this conference along with a list of the poster displays exhibited in the foyers of the conference center.
Fuel cells have an enormous potential as efficient, reliable, environmentally friendly, and potentially inexpensive source of electricity. In their modern form, they were developed for practical usage in the NASA space program. Such fuels cells provided the electrical power for the Gemini, Apollo and space shuttle vehicles. Subsequent scientific and engineering advances by fuel cell developers have provided the opportunity to apply these devices to earth-bound, civilian applications.
The simple fuel cell is an electrochemical device that converts ordinary fuel and air into an electrical current. This cell is capable of continuously producing electricity as long as the fuel and air are supplied without interruption. Internally the fuel cell consists of a negative electrode (anode) and a positive electrode (cathode) separated by an ion-conducting electrolyte containing catalysts to enhance efficiency. Air and fuel are introduced at the anode resulting in the production of hydrogen ions, which then pass through the electrolyte to the cathode where they combine with oxygen ions to produce water. The electrons, which cannot pass through the electrolyte, are collected at the anode and conducted via an external circuit to the cathode. The electron flow in the external circuit is patted to provide direct current electricity. This simple cell provides relatively small amounts of electrical power, so several of these simple cells are assembled into a stack to achieve higher voltage levels. This assembled stack has no moving parts, is noiseless, and only produces heat and water as by-products.
Actually, modern fuel cell systems are much more complicated that the simple cell described above. First of all, the input fuel, most commonly natural gas, is reprocessed in a reformer unit into a concentrated hydrogen mixture, which is then fed to the fuel cell anode. The resulting direct current is directed to an inverter unit, which converts the DC into useful alternating current and then to the power grid. Also required are a number of auxiliary systems providing temperature control, heat recovery, water treatment, air processing, ventilation, nitrogen purge, AC power distribution and instrumentation and controls to regulate all these factors. The modern fuel cells themselves are categorized according to the type of electrolyte employed:
- Low Temperature Cells (100-450o F):
- Alkaline Cells (AFC)
- Polymer or Proton Exchange Membrane Cells (PEMFC)
- Phosphoric Acid Cells
- High Temperature Cells (1100-1800o F):
- Molten Carbonate Cells (MCFC)
- Solid Oxide Cells (SOFC)
Low temperature fuel cells require more exotic catalysts in their electrolytes, sometimes employing precious metals, and also require much purer hydrogen fuel. However, the low temperature cells can generate electricity at higher efficiency than the high temperature cells. Generally summarizing, fuel cells have about twice the electrical generating efficiency of fossil fuel plants, but can cost between two to fives times as much to install and operate, depending upon the type of electrolyte.
Driven by these parameters, this conference’s technical sessions and technical papers almost universally concentrated on reporting developments and experiments designed to improve the electrical generating efficiency, and to reduce the cost, of fuel cells. Enhanced by government, industrial and university research funding, these developments showed a steady progress toward increased efficiency and lower costs. Examples of such developments include experiments to determine the optimum operating temperature and pressure inside the fuel cell; experiments to determine the optimum density of the liquid electrolytes as well as testing for the most hydrophilic electrode materials; tests to determine the most effective membrane configurations and materials including nano-porosity elements; the results of adding microbacterial materials to electrolysis as well as the addition of industrial chemicals such as methane (CH4), methanol (CH3OH), ethanol (C2H7No) cellulose (C6H10O5) glucose (C6H12O6) and various enzymes; the effects of using electrodes composed of expensive and rare materials such as gold, platinum, rubidium, vanadium, as well as nickel copper, aluminum-nickel, gold-nickel alloys; the results of employing such exotic catalysts as sodium-borohydride (NaBH4), hydrogen peroxide (H2O2), cobalt-boride (Co3B), sodium hydroxide (NaOH), lithium silicate (Li4SiO4), nickel-aluminum oxide (NiAl2O3), cerium dioxide (CeO2), and various cerium-zirconium mixtures; even the effects of varying water droplet sizes generated at the cathode; and finally, the ability of fuel cells to perform in hazardous conditions such as extreme cold (less than 0 degrees F.) and hyper-humidity (greater than 90%).
Despite these economic and technical limitations, the installation of fuel cell power generating units continues to expand. Spurred on by substantial funding from government agencies, industry innovators, universities and research institutions, 8500 megawatts of fuel cell generated electrical energy have been installed worldwide, with 746 megawatts generated at 2000 sites in the United States. In NY State, NYSERDA has invested $136 million to develop generation of 122 megawatts at present with 315 megawatts to be in operation by 2009. 100 projects have been completed or are under construction among which are 8 operating fuel cell units at four wastewater treatment plants as well as functioning units at several area hotels and resorts. Similarly the NY State Power Authority has installed 13 major fuel cell generating units since 1997 and these units provide 23% of electrical power consumed statewide. These units, installed at state university dormitories, hospitals, police precincts, and aquariums, have attained operating lives as high as 60,000 hours – equivalent to 6 2/3 years of continuous operation before shutdown for overhaul. In the commercial sphere, the Keyspan organization first began developing fuel cell power in 1968 and has invested more than $1.9 billion since then throughout its market area consisting of the Northeastern US. Keyspan has frequently cooperated with government agencies to provide plug-in power and distribution to trucking centers, telecom central facilities, hospitals, military arsenals, and schools. Other commercial organizations are equally aggressive in promoting fuel cell developments and installations.
Of all these installations, about 75% use hydrogen as the primary fuel with the remaining 25% employing various forms of biofuels and other complex chemicals. These units generate about 60% of the electrical power for in-house use, with the remaining 40% being fed back into the local grid. One big advantage of these fuel cell units is the substantial savings they provide in current distribution costs due to the relatively short transmission lines involved. Still today, fuel cells are not competitive with fossil fuel plants when generating electricity. One industry initiative worth noting is the creation of the clean energy fund in Connecticut where low cost loans are available to engineers and scientists. So far this fund has invested in 412 kilowatts worth of demonstration projects.
Among the topics that attracted great interest at this conference was the use of fuel cell power to propel vehicles. This usage is even more demanding of fuel cell design than stationary applications. The fuel cell itself must be constructed of ultra-light weight materials and must provide high speed and acceleration, ease of driving control, low costs, and durability of components. All fuel cell vehicles use hydrogen for power because no greenhouse gases are created or emitted, only a stream of water and water vapor. The hydrogen may be supplied in one of four forms:
- As a compressed gas at 5,000 psi minimum pressure
- As a liquid chilled to minus 423 degrees F.
- As a solid in metal hydride particles
- Generated in an onboard reforming unit from methanol or gasoline or natural gas
Because of these complexities, equal power generating units of hydrogen and gasoline result in hydrogen costing two to three times as expensive as gasoline, depending upon which form of hydrogen is employed.
All major vehicle manufacturers are heavily engaged in hydrogen powered and fuel cell propelled cars and trucks because of impending government regulations covering fuel economy and emissions standards. Their research and development has so far produced a number of workable vehicles having the following formats:
- About 70% of operating vehicles employ compressed hydrogen energizing an onboard fuel cell to generate electricity driving an electric motor.
- About 10% of these vehicles use the hydrogen gas as burned fuel directly in a special internal combustion engine.
- About 10% of the vehicles use liquid hydrogen as burned fuel directly in an IC engine.
- About 10% of the vehicles derive hydrogen from metal hydride particles and then burn the hydrogen directly in an IC engine.
In the 2008 model year most manufacturers will offer fleets of about 100 cars, vans and small buses powered by hydrogen for lease to interested commercial organizations such as utilities and government agencies. However, the lack of hydrogen distribution systems, their inherently high cost, and even a latent fear of the safety of hydrogen itself limit practical widespread usage of these vehicles. In the various formats these vehicles will be able to travel 150 to 350 miles on a tank full of fuel. Given the rate of current development, expert’s estimate that it will take until 2020 before affordable hydrogen cars, trucks and buses will be widely available to the general public.
Meanwhile, mechanical engineers and other technical innovators are also investigating other sources of renewable and environmentally advantageous clean energy such as nuclear and solar technologies. The Met Section will report on these developments immediately after ASME organizes and conducts informative conferences like the excellent one just held in Brooklyn.