HYDROGEN FUEL CELLS
by Tom Dickerman/AHA
We are about to witness a most amazing event. Internal combustion engines (ICE’s), so abundant in the past century are about to be replaced by fuel cell systems over the next few decades. They will replace ICE’s for both vehicle power and for stationary power generation. Fuel cells will also replace batteries for small portable power supply. Hydrogen in an internal combustion engine(ICE) produces useable power at about 17 percent efficiency. A fuel cell system has about 50 percent efficiency. This makes the fuel cell about three times as efficient as an ICE! This explains the urgency to make fuel cells commercially available.
The United States has spent more than $500 million in the development of highly efficient and environmentally benign fuel cells, according to Ed Gillis, the former director of fuel cell programs at the Electric Power Research Institute. While research continues, major commercialization efforts are underway at this time. Nearly every major car company in the world has invested massively in fuel cells for vehicles. Their total investment commitments now exceed two billion dollars, according to Peter Hoffman, publisher of the Hydrogen and Fuel Cell Newsletter.
HOW FUEL CELLS WORK
In a typical fuel cell, hydrogen gas is supplied through a porous anode and oxygen or air is supplied through a porous cathode. An electrolyzer separates the two gases, which is a material that will not allow either of the gases to pass. On a molecular level, the hydrogen and oxygen have an affinity for each other, and would like to come together to create water (2 H2 + 02 = 2 H20).
In this situation, the hydrogen atoms instantly give up their electrons, which then travel through an external circuit. The remaining parts of the hydrogen atoms are protons, which can now pass through the electrolyte, and connect with oxygen atoms. The receipt of free electrons from the external circuit allows the completion of the electrochemical reactions, as water is formed. The electrons traveling the electric circuit is electric current. Typically, a fuel cell produces about one volt when the circuit is open, which drops to a half volt when the circuit is closed and producing electrical power. For higher, more useful voltages, the fuel cells are usually stacked. One hundred cells in a stack yield about 50 volts of direct current. (DC)
TYPES OF FUEL CELLS
Fuel cells are usually named for their electrolytes. To date five different electrolyte materials have shown potential for commercial development. The five fuel cell types have different characteristics, which make each one suitable for some applications but not others. A short description of the five types follows.
ALKALINE FUEL CELLS (AFC’S)
In 1839, W. R. Grove of Great Britain built the first fuel cell. He added a catalyst, potassium hydroxide, to water and put in the ends of two wires. By impressing direct electrical current, he split the water into hydrogen at one wire and oxygen at the other. This is called electrolysis of water. Then capturing both the hydrogen and oxygen, he found he could reverse the process, adding the hydrogen and oxygen at the two poles to re-create water and electric current. In this mode, he had a fuel cell.
This first fuel cell was called the alkaline fuel cell (AFC). In the 1960’s a more complex but highly reliable AFC stack was created for our manned spacecraft. AFC’s and phosphoric acid fuel cells (PAFC’S) provided essential drinking water, electricity and a little heat in the cold of outer space for the manned spacecraft Gemini, Apollo and the Space Shuttle Orbiter. Men and women could not have gone into space without them.
An AFC and a PAFC from these flights are on exhibit at the National Air and Space Museum in Washington, DC.
PHOSPHORIC ACID FUEL CELLS (PAFC’s)
The next fuel cell to be developed was the phosphoric acid fuel cell. PAFC’s do not require pure oxygen, but can use air at the cathode. PAFC’s are now in use for electric power generation, notably at Kaiser Hospitals, air quality offices in California, and at various sites in Japan.
PAFC’s are now being developed by the DOE (and others) for trucks, buses and railroad engines. Some PAFC’s are designed to take in methanol and reform it under heat and pressure, stripping off hydrogen for the anode fuel supply.
PROTON EXCHANGE MEMBRANE (PEM) FUEL CELLS,
ALSO KNOWN AS POLYMER ELECTROLYTE FUEL CELLS (PEFC’S)
PEM’s have only a thin plastic membrane for their electrolyte. PEM’S can be very small, with high power densities. Taking away the waste heat in a uniform continuous way, so the membrane doesn’t burn up, is a significant engineering challenge, especially for high energy/power density designs.
The most reliable PEM fuel cells to date have been built by Ballard Power Systems of Vancouver, Canada. Ballard has now sold its vehicle fuel cell division to Daimler-Benz. It is also possible that Toyota or another Japanese company may be the first to mass-produce a fuel cell car. Fuel cell cars with on-board hydrogen fuel will have virtually NO emissions, except a little steam, and will be very quiet. This will be the start of an environmental revolution, as we begin to replace all the dirty, inefficient internal combustion engines with clean, highly efficient fuel cell engines, worldwide.
SOLID OXIDE FUEL CELLS (SOFC’s)
Solid oxide fuel cells, which can only operate at high temperatures, are not suited for transportation, but for stationary power. They hold the promise of high fuel efficiency, high power density and low cost.
SOFC’s can be of tubular or planar construction. For tubular designs, Westinghouse has completed many hours of successful operation. Ceramatics is a leader in planar SOFC’S, which are expected to have low cost, high performance and high reliability.
MOLTEN CARBONATE FUEL CELLS (MCFC’s)
Energy Research Corporation (ERC) and M-C Power Corporation are making important gains toward commercialization of molten carbonate fuel cells. Stacks have been tested and small demonstration plants have been completed. ERC also completed a large two-megawatt MCFC plant for the City of Santa Clara, California. Because of operating problems, the plant is not in use. It is believed the plant may have been scaled up to far from smaller prototypes, and that intermediate sized plants should have been built first, to help resolve engineering problems of scale.
MARKET ENTRY FOR FUEL CELLS.
Peter Bos, President of Polydyne, Inc, has analyzed costs of manufacturing various fuel cells, and the prices buyers are willing to pay for their fuel cell applications. According to Mr. Bos, the first fuel cells to enter the market will be for high value operations.
This seems to be borne out by the history of fuel cells to date. The first to develop fuel cells were NASA and the military, which were willing to pay virtually any price for the fuel cells that met their needs. Fuel cells are now being marketed to remote sites where power demand is small, but reliability is crucial, such as remote weather and pollution monitoring stations. Kaiser hospitals have decided to use fuel cell plants for primary power for hospital life support systems, which must be highly reliable. Low noise levels and low pollution near hospitals were also key factors for Kaiser.
Fuel cells will also be used early on for devices such as cellular phones, laptop computers and handheld camcorders. For such uses reliability, quietness, size and weight are more important considerations that the price. Fuel cells, with their almost unlimited shelf life, will soon be replacing conventional batteries, which often go dead before they are used.
Throughout the third world, small villagers are pooling their scarce money to buy two appliances: a TV set and a small diesel or gasoline engine to run it. The fuel for the generator must often be carried twenty of fifty miles from the nearest fuel station. Here is a market for solar photovoltaics. But what about at night, or when the weather is overcast? Often villagers also carry heavy lead acid batteries to their location.
This is a very likely near-term market for fuel cells. With a small electolyzer and a solar panel, hydrogen can be made and stored in a small tank. At night, a fuel cell can then be operated to generate power on demand. No more twenty-mile walks to the nearest store; no more scarce money spent for fuel.
Third world countries in general are good candidates for hydrogen and fuel cell systems, because they lack the competing power grids and natural gas pipelines of the West. They also lack the entrenched corporate interests that often block development of sustainable energy systems here in America.
In the near future, solar-produced clean hydrogen fuel will also be used for cooking and heating in these countries, gradually bringing to a halt the gathering of firewood, which is now decimating many areas of the Planet. Trees can be planted without fear that they will be cut for firewood. Whole continents can regrow their trees. Such a prospect is very important for the mitigation of global warming.
It is no exaggeration to say that hydrogen and fuel cell systems have the potential as critical tools both to counter global warming and to reverse other environmental damage, worldwide.
The fuel cell revolution is coming. Fuel cells will be the engines/generators of choice for all uses in the twenty-first century. To paraphrase Lee Iacocca, we can lead or we can follow, or we can just get out of the way.
FUEL CELL QUIZ
1. FIVE TYPES OF FUEL CELLS ARE NEARING COMMERCIALIZATION. NAME THREE.
a) ALKALINE
b) ACID
c) SOLID OXIDE
d) MOLTEN CARBONATE
e) PROTON EXCHANGE MEMBRANE
2. NAME THREE COMPANIES THAT ARE RESEARCHING/DEVELOPING FUEL CELLS.
a) BALLARD
b) DAIMLER-BENZ
c) WESTINGHOUSE
d) M-C CORPORATION
e) TOYOTA
f) CERAMATEC
g) ENERGY RESEARCH CORPORATION
3. WHAT IS THE EFFICIENCY OF AN INTERNAL COMBUSTION ENGINE?
a) 17 PERCENT
4. WHAT IS THE TYPICAL EFFICIENCY OF A FUEL CELL SYSTEM?
a) 50 PERCENT
5. NAME TWO APPLICATIONS FOR FUEL CELLS. WHICH ARE LIKELY TO BE EARLY ADOPTERS?
a) CAMCORDERS
b) LAPTOP COMPUTERS
c) BATTERIES
d) CELL PHONES
e) REMOTE SITE APPLICATIONS
6. IS HYDROGEN A FUEL?
a) YES
7. IS HYDROGEN COMMON IN NATURE?
a) YES-MOST ABUNDANT ATOM IN THE UNIVERSE
8. WHAT ARE ADVANTAGES OF A FUEL CELL OVER AN INTERNAL COMBUSTION ENGINE?
a) THREE TIMES THE EFICIENCY
b) NO DEPLETION OF FOSSIL FUELS
c) NO AIR POLLUTION
d) NO CONTRIBUTION TO GLOBAL WARMING
9. HOW CAN FUEL CELLS HELP TO MITIGATE GLOBAL WARMING?
a) BY REPLACING FOSSIL FUELS, ELIMINATING THEIR CO2 EMISSIONS
b) BY REPLACING THE USE OF FIREWOOD, STOPPING THE CUTTING OF TREES, WHICH SEQUESTER CARBON