Carbon Free Energy
We provide Renewable Energy Technologies and EcoGeneration products, services and solutions that are Kyoto Protocol compliant. This results in a Cooler, Cleaner, Greener™ planet for everyone, as well as decreased operating expenses and increased profits for the owners. Our Renewable Energy Technologies™ and EcoGeneration™ projects are also so environmentally safe, that we are classifying them as Carbon Free Energy™ or "Pollution Free Power™” projects. Unlike most companies, we are equipment supplier/vendor neutral. This means we help our clients select the best equipment for their specific application. This approach provides our customers with superior performance, decreased operating expenses and increased return on investment.
Cogeneration Technologies, located in Houston, Texas, provides project development services that generate clean energy and significantly reduce greenhouse gas emissions and carbon dioxide emissions. Included in this are our turnkey "ecogeneration™" products and services which includes renewable energy technologies, waste to energy, waste to watts™ and waste heat recovery solutions. Other project development technologies include; Anaerobic Digester, Anaerobic Lagoon, Biogas Recovery, BioMethane, Biomass Gasification, and Landfill Gas To Energy, project development services.
Products and services provided by Cogeneration Technologies include the following power and energy project development services:
- Project Engineering Feasibility & Economic Analysis Studies
- Engineering, Procurement and Construction
- Environmental Engineering & Permitting
- Project Funding & Financing Options; including Equity Investment, Debt Financing, Lease and Municipal Lease
- Shared/Guaranteed Savings Program with No Capital Investment from Qualified Clients
- Project Commissioning
- 3rd Party Ownership and Project Development
- Long-term Service Agreements
- Operations & Maintenance
- Green Tag (Renewable Energy Credit, Carbon Dioxide Credits, Emission Reduction Credits) Brokerage Services; Application and Permitting
We are Renewable Energy Technologies specialists and develop clean power and energy projects that will generate a "Renewable Energy Credit," Carbon Dioxide Credits and Emission Reduction Credits. Some of our products and services solutions and technologies include; Absorption Chillers, Adsorption Chillers, Automated Demand Response, Biodiesel Refineries, Biofuel Refineries, Biomass Gasification, BioMethane, Canola Biodiesel, Coconut Biodiesel, Cogeneration, Concentrating Solar Power, Demand Response Programs, Demand Side Management, Energy Conservation Measures, Energy Master Planning, Engine Driven Chillers, Geothermal Heat pumps, Ground source Heat pumps, Solar CHP, Solar Cogeneration, Rapeseed Biodiesel, Solar Electric Heat Pumps, Solar Electric Power Systems, Solar Heating and Cooling, Solar Trigeneration, Soy Biodiesel, Trigeneration, and Water source Heat pumps.
Clean Coal Technology & the President's Clean Coal Power Initiative
|During his campaign for the Presidency, George W. Bush pledged to commit $2 billion over 10 years to advance clean coal technology – a pledge he has subsequently carried out in the National Energy Policy and in budget requests to Congress.|
"Clean coal technology" describes a new generation of energy processes that sharply reduce air emissions and other pollutants compared to older coal-burning systems. In the late 1980s and early 1990s, the U.S. Department of Energy conducted a joint program with industry and State agencies to demonstrate the best of these new technologies at scales large enough for companies to make commercial decisions. More than 20 of the technologies tested in the original program achieved commercial success.
The early program, however, was focused on the environmental challenges of the time – primarily concerns over the impact of acid rain on forests and watersheds. In the 21st century, additional environmental concerns have emerged – the potential health impacts of trace emissions of mercury, the effects of microscopic particles on people with respiratory problems, and the potential global climate-altering impact of greenhouse gases.
With coal likely to remain one of the nation's lowest-cost electric power suppliers for the foreseeable future, President Bush has pledged a new commitment to even more advanced clean coal technologies. As the President said in presenting his National Energy Policy to the American public on May 17, 2001 , "More than half of the electricity generated in America today comes from coal. If we weren't blessed with this natural resource, we would face even greater [energy] shortages and higher prices today. Yet, coal presents an environmental challenge. So our plan funds research into new, clean coal technologies."
Building on the successes of the original program, the new clean coal initiative encompasses a broad spectrum of research and large-scale projects that target today's most pressing environmental challenges.
Initially, the demonstration portion of the program, the Clean Coal Power Initiative, is providing government co-financing for new coal technologies that can help utilities meet the President's Clear Skies Initiative to cut sulfur, nitrogen and mercury pollutants from power plants by nearly 70 percent by the year 2018. Also, some of the early projects are showing ways to reduce greenhouse gases from coal plants by boosting the efficiency at which they convert coal to electricity or other energy forms.
Coal gasification offers one of the most versatile and cleanest ways to convert the energy content of coal into electricity, hydrogen, and other energy forms.
The first pioneering coal gasification electric power plants are now operating commercially in the United States and in other nations, and many experts predict that coal gasification will be at the heart of the future generations of clean coal technology plants for several decades into the future. For example, at the core of the U.S. Department of Energy's FutureGen power plant of the future will be an advanced coal gasifier.
Rather than burning coal directly, gasification breaks down coal – or virtually any carbon-based feedstock – into its basic chemical constituents. In a modern gasifier, coal is typically exposed to hot steam and carefully controlled amounts of air or oxygen under high temperatures and pressures. Under these conditions, carbon molecules in coal break apart, setting into motion chemical reactions that typically produce a mixture of carbon monoxide, hydrogen and other gaseous compounds.
Gasification, in fact, may be one of the best ways to produce clean-burning hydrogen for tomorrow's automobiles and power-generating fuel cells. Hydrogen and other coal gases can also be used to fuel power-generating turbines or as the chemical "building blocks" for a wide range of commercial products.
The Energy Department's Office of Fossil Energy is working on coal gasifier advances that enhance efficiency, environmental performance, and reliability as well as expand the gasifier's flexibility to process a variety of feedstocks (including biomass and municipal/industrial waste).
The environmental benefits stem from the capability to cleanse as much as 99 percent of the pollutant-forming impurities from coal-derived gases. Sulfur in coal, for example, emerges as hydrogen sulfide and can be captured by processes used today in the chemical industry. In some methods, the sulfur can be extracted in a form that can be sold commercially. Likewise, nitrogen typically exits as ammonia and can be scrubbed from the coal gas by processes that produce fertilizers or other ammonia-based chemicals.
The Office of Fossil Energy is also exploring advanced syngas cleaning and conditioning processes that are even more effective in eliminating emissions from coal gasifiers. Multi-contaminant control processes are being developed that reduce pollutants to parts-per-billion levels and are effective in cleaning mercury and other trace metals in addition to other impurities.
Coal gasification may offer a further environmental advantage in addressing concerns over the atmospheric buildup of greenhouse gases, such as carbon dioxide.. If oxygen is used in a coal gasifier instead of air, carbon dioxide is emitted as a concentrated gas stream. In this form, it can be captured more easily and at lower costs for ultimate disposition in various sequestration approaches. (By contrast, when coal burns or is reacted in air, 80 percent of which is nitrogen, the resulting carbon dioxide is much more diluted and more costly to separate from the much larger mass of gases flowing from the combustor or gasifier.)
Efficiency gains are another benefit of coal gasification. In a typical coal combustion plant, heat from burning coal is used to boil water, making steam that drives a steam turbine-generator. Only a third of the energy value of coal is actually converted into electricity by most combustion plants, the rest is lost as waste heat.
A coal gasification power plant, however, typically gets dual duty from the gases it produces. First, the coal gases, cleaned of their impurities, are fired in a gas turbine – much like natural gas – to generate one source of electricity. The hot exhaust of the gas turbine is then used to generate steam for a more conventional steam turbine-generator. This dual source of electric power, called a "combined cycle," converts much more of coal's inherent energy value into useable electricity. The fuel efficiency of a coal gasification power plant can be boosted to 50 percent or more.
Future concepts that incorporate a fuel cell or fuel cell-gas turbine hybrid could achieve even higher efficiencies, perhaps in the 60 percent range, or nearly twice today's typical coal combustion plants. And if any of the remaining waste heat can be channeled into process steam or heat, perhaps for nearby factories or district heating plants, the overall fuel use efficiency of future gasification plants could reach 70 to 80 percent.
Higher efficiencies translate into more economical electric power and potential savings for ratepayers. A more efficient plant also uses less fuel to generate power, meaning that less carbon dioxide is produced. In fact, coal gasification power processes under development by the Energy Department could cut the formation of carbon dioxide by 40 percent or more compared to today's conventional coal-burning plant.
The capability to produce electricity, hydrogen, chemicals, or various combinations while virtually eliminating air pollutants and potentially greenhouse gas emissions makes coal gasification one of the most promising technologies for the energy plants of tomorrow.
COAL is our most abundant fossil fuel. The United States has more coal than the rest of the world has oil. There is still enough coal underground in this country to provide energy for the next 200 to 300 years.
But coal is not a perfect fuel.
Trapped inside coal are traces of impurities like sulfur and nitrogen. When coal burns, these impurities are released into the air.
While floating in the air, these substances can combine with water vapor (for example, in clouds) and form droplets that fall to earth as weak forms of sulfuric and nitric acid – scientists call it "acid rain."
There are also tiny specks of minerals – including common dirt – mixed in coal. These tiny particles don't burn and make up the ash left behind in a coal combustor. Some of the tiny particles also get caught up in the swirling combustion gases and, along with water vapor, form the smoke that comes out of a coal plant's smokestack. Some of these particles are so small that 30 of them laid side-by-side would barely equal the width of a human hair!
Also, coal like all fossil fuels is formed out of carbon. All living things – even people – are made up of carbon. (Remember – coal started out as living plants.) But when coal burns, its carbon combines with oxygen in the air and forms carbon dioxide. Carbon dioxide is a colorless, odorless gas, but in the atmosphere, it is one of several gases that can trap the earth's heat. Many scientists believe this is causing the earth's temperature to rise, and this warming could be altering the earth's climate (read more about the "greenhouse effect").
Sounds like coal is a dirty fuel to burn. Many years ago, it was. But things have changed. Especially in the last 20 years, scientists have developed ways to capture the pollutants trapped in coal before the impurities can escape into the atmosphere. Today, we have technology that can filter out 99 percent of the tiny particles and remove more than 95 percent of the acid rain pollutants in coal.
We also have new technologies that cut back on the release of carbon dioxide by burning coal more efficiently.
Many of these technologies belong to a family of energy systems called "clean coal technologies." Since the mid-1980s, the U.S. Government has invested more than $2 billion in developing and testing these processes in power plants and factories around the country. Private companies and State governments have been part of this program. In fact, they have contributed more than $4 billion to these projects.
How do you make coal cleaner?
Actually there are several ways. Take sulfur, for example. Sulfur is a yellowish substance that exists in tiny amounts in coal. In some coals found in Ohio, Pennsylvania, West Virginia and other eastern states, sulfur makes up from 3 to 10 percent of the weight of coal.
For some coals found in Wyoming, Montana and other western states (as well as some places in the East), the sulfur can be only 1/100ths (or less than 1 percent) of the weight of the coal. Still, it is important that most of this sulfur be removed before it goes up a power plant's smokestack.
|Although coal is primarily a mixture of carbon (black) and hydrogen (red) atoms, sulfur atoms (yellow) are also trapped in coal, primarily in two forms. In one form, the sulfur is a separate particle often linked with iron (green) with no connection to the carbon atoms, as in the center of the drawing. In the second form, sulfur is chemically bound to the carbon atoms, such as in the upper left.|
One way is to clean the coal before it arrives at the power plant. One of the ways this is done is by simply crushing the coal into small chunks and washing it. Some of the sulfur that exists in tiny specks in coal (called "pyritic sulfur” because it is combined with iron to form iron pyrite, otherwise known as "fool's gold) can be washed out of the coal in this manner. Typically, in one washing process, the coal chunks are fed into a large water-filled tank. The coal floats to the surface while the sulfur impurities sink. There are facilities around the country called "coal preparation plants" that clean coal this way.
Not all of coal's sulfur can be removed like this, however. Some of the sulfur in coal is actually chemically connected to coal's carbon molecules instead of existing as separate particles. This type of sulfur is called "organic sulfur," and washing won't remove it. Several process have been tested to mix the coal with chemicals that break the sulfur away from the coal molecules, but most of these processes have proven too expensive. Scientists are still working to reduce the cost of these chemical cleaning processes.
Most modern power plants — and all plants built after 1978 — are required to have special devices installed that clean the sulfur from the coal's combustion gases before the gases go up the smokestack. The technical name for these devices is "flue gas desulfurization units," but most people just call them "scrubbers" — because they "scrub" the sulfur out of the smoke released by coal-burning boilers.
How do scrubbers work?
Most scrubbers rely on a very common substance found in nature called "limestone." We literally have mountains of limestone throughout this country. When crushed and processed, limestone can be made into a white powder. Limestone can be made to absorb sulfur gases under the right conditions — much like a sponge absorbs water.
In most scrubbers, limestone (or another similar material called lime) is mixed with water and sprayed into the coal combustion gases (called "flue gases"). The limestone captures the sulfur and "pulls" it out of the gases. The limestone and sulfur combine with each other to form either a wet paste (it looks like toothpaste!), or in some newer scrubbers, a dry powder. In either case, the sulfur is trapped and prevented from escaping into the air.
The Clean Coal Technology Program tested several new types of scrubbers that proved to be more effective, lower cost, and more reliable than older scrubbers. The program also tested other types of devices that sprayed limestone inside the tubing (or "ductwork') of a power plant to absorb sulfur pollutants.
But what about nitrogen pollutants? That's another part of the Clean Coal story.
|How NOx Forms|
|Air is mostly nitrogen molecules (green in the above diagram) and oxygen molecules (purple). When heated hot enough (around 3000 degrees F), the molecules break apart and oxygen atoms link with the nitrogen atoms to form NOx, an air pollutant.|
Knocking the NOx Out of Coal
Nitrogen is the most common part of the air we breathe. In fact, about 80% of the air is nitrogen. Normally, nitrogen atoms float around joined to each other like chemical couples. But when air is heated — in a coal boiler's flame, for example — these nitrogen atoms break apart and join with oxygen. This forms "nitrogen oxides" — or, as it is sometimes called, "NOx" (rhymes with "socks"). NOx can also be formed from the atoms of nitrogen that are trapped inside coal.
In the air, NOx is a pollutant. It can cause smog, the brown haze you sometimes see around big cities. It is also one of the pollutants that forms "acid rain." And it can help form something called "groundlevel ozone," another type of pollutant that can make the air dingy.
NOx can be produced by any fuel that burns hot enough. Automobiles, for example, produce NOx when they burn gasoline. But a lot of NOx comes from coal-burning power plants, so the Clean Coal Technology Program developed new ways to reduce this pollutant.
One of the best ways to reduce NOx is to prevent it from forming in the first place. Scientists have found ways to burn coal (and other fuels) in burners where there is more fuel than air in the hottest combustion chambers. Under these conditions, most of the oxygen in air combines with the fuel, rather than with the nitrogen. The burning mixture is then sent into a second combustion chamber where a similar process is repeated until all the fuel is burned.
This concept is called "staged combustion" because coal is burned in stages. A new family of coal burners called "low-NOx burners" has been developed using this way of burning coal. These burners can reduce the amount of NOx released into the air by more than half. Today, because of research and the Clean Coal Technology Program, more than half of all the large coal-burning boilers in the United States will be using these types of burners. By the year 2000, more than 3 out of every four boilers will have been outfitted with these new clean coal technologies.
There is also a family of new technologies that work like "scubbers" by cleaning NOx from the flue gases (the smoke) of coal burners. Some of these devices use special chemicals called "catalysts" that break apart the NOx into non-polluting gases. Although these devices are more expensive than "low-NOx burners," they can remove up to 90 percent of NOx pollutants.
But in the future, there may be an even cleaner way to burn coal in a power plant. Or maybe, there may be a way that doesn't burn the coal at all.
Fluidized Bed Boilers
It was a wet, chilly day in Washington DC in 1979 when a few scientists and engineers joined with government and college officials on the campus of Georgetown University to celebrate the completion of one of the world's most advanced coal combustors.
It was a small coal burner by today's standards, but large enough to provide heat and steam for much of the university campus. But the new boiler built beside the campus tennis courts was unlike most other boilers in the world.
|A Fluidized Bed Boiler|
|In a fluidized bed boiler, upward blowing jets of air suspend burning coal, allowing it to mix with limestone that absorbs sulfur pollutants.|
It was called a "fluidized bed boiler." In a typical coal boiler, coal would be crushed into very fine particles, blown into the boiler, and ignited to form a long, lazy flame. Or in other types of boilers, the burning coal would rest on grates. But in a "fluidized bed boiler," crushed coal particles float inside the boiler, suspended on upward-blowing jets of air. The red-hot mass of floating coal — called the "bed" — would bubble and tumble around like boiling lava inside a volcano. Scientists call this being "fluidized." That's how the name "fluidized bed boiler" came about.
Why does a "fluidized bed boiler" burn coal cleaner?
There are two major reasons. One, the tumbling action allows limestone to be mixed in with the coal. Remember limestone from a couple of pages ago? Limestone is a sulfur sponge — it absorbs sulfur pollutants. As coal burns in a fluidized bed boiler, it releases sulfur. But just as rapidly, the limestone tumbling around beside the coal captures the sulfur. A chemical reaction occurs, and the sulfur gases are changed into a dry powder that can be removed from the boiler. (This dry powder — called calcium sulfate — can be processed into the wallboard we use for building walls inside our houses.)
The second reason a fluidized bed boiler burns cleaner is that it burns "cooler." Now, cooler in this sense is still pretty hot — about 1400 degrees F. But older coal boilers operate at temperatures nearly twice that (almost 3000 degrees F). Remember NOx from the page before (go back)? NOx forms when a fuel burns hot enough to break apart nitrogen molecules in the air and cause the nitrogen atoms to join with oxygen atoms. But 1400 degrees isn't hot enough for that to happen, so very little NOx forms in a fluidized bed boiler.
The result is that a fluidized bed boiler can burn very dirty coal and remove 90% or more of the sulfur and nitrogen pollutants while the coal is burning. Fluidized bed boilers can also burn just about anything else — wood, ground-up railroad ties, even soggy coffee grounds.
Today, fluidized bed boilers are operating or being built that are 10 to 20 times larger than the small unit built almost 20 years ago at Georgetown University. There are more than 300 of these boilers around this country and the world. The Clean Coal Technology Program helped test these boilers in Colorado, in Ohio and most recently, in Florida.
|The Ohio Power Company built this advanced pressurized fluidized bed boiler near the town of Brilliant, OH, as part of a joint project with the U.S. Department of Energy.
(Click on photo for larger version.)
A new type of fluidized bed boiler makes a major improvement in the basic system. It encases the entire boiler inside a large pressure vessel, much like the pressure cooker used in homes for canning fruits and vegetables — except the ones used in power plants are the size of a small house! Burning coal in a "pressurized fluidized bed boiler" produces a high-pressure stream of combustion gases that can spin a gas turbine to make electricity, then boil water for a steam turbine — two sources of electricity from the same fuel!
A "pressurized fluidized bed boiler" is a more efficient way to burn coal. In fact, future boilers using this system will be able to generate 50% more electricity from coal than a regular power plant from the same amount of coal. That's like getting 3 units of power when you used to get only 2.
Because it uses less fuel to produce the same amount of power, a more efficient "pressurized fluidized bed boiler" will reduce the amount of carbon dioxide (a greenhouse gas) released from coal-burning power plants.
"Pressurized fluidized bed boilers" are one of the newest ways to burn coal cleanly. But there is another new way that doesn't actually burn the coal at all.
Don't think of coal as a solid black rock. Think of it as a mass of atoms. Most of the atoms are carbon. A few are hydrogen. And there are some others, like sulfur and nitrogen, mixed in. Chemists can take this mass of atoms, break it apart, and make new substances — like gas!
|One of the most advanced – and cleanest – coal power plants in the world is Tampa Electric's Polk Power Station in Florida. Rather than burning coal, it turns coal into a gas that can be cleaned of almost all pollutants.|
How do you break apart the atoms of coal? You may think it would take a sledgehammer, but actually all it takes is water and heat. Heat coal hot enough inside a big metal vessel, blast it with steam (the water), and it breaks apart. Into what?
The carbon atoms join with oxygen that is in the air (or pure oxygen can be injected into the vessel). The hydrogen atoms join with each other. The result is a mixture of carbon monoxide and hydrogen — a gas.
Now, what do you do with the gas?
You can burn it and uses the hot combustion gases to spin a gas turbine to generate electricity. The exhaust gases coming out of the gas turbine are hot enough to boil water to make steam that can spin another type of turbine to generate even more electricity. But why go to all the trouble to turn the coal into gas if all you are going to do is burn it?
A major reason is that the impurities in coal — like sulfur, nitrogen and many other trace elements — can be almost entirely filtered out when coal is changed into a gas (a process called gasification). In fact, scientists have ways to remove 99.9% of the sulfur and small dirt particles from the coal gas. Gasifying coal is one of the best ways to clean pollutants out of coal.
Another reason is that the coal gases — carbon monoxide and hydrogen — don't have to be burned. They can also be used as valuable chemicals. Scientists have developed chemical reactions that turn carbon monoxide and hydrogen into everything from liquid fuels for cars and trucks to plastic toothbrushes!
Today, in Tampa, Florida, and West Terre Haute, Indiana, there are power plants generating electricity by gasifying coal, rather than burning it. At a plant in Kingsport, Tennessee, coal gas is being used to make plastic for photographic film and to make methanol (a fuel that can be burned in automobile engines).
Coal gasification could be one of the most promising ways to use coal in the future to generate electricity and other valuable products. Yet, it is only one of an entirely new family of energy processes called "Clean Coal Technologies" — technologies that can make fossil fuels future fuels.
Since the early 19th century, scientists have recognized hydrogen as a potential source of fuel. Current uses of hydrogen are in industrial processes, rocket fuel, and spacecraft propulsion. With further research and development, this fuel could also serve as an alternative source of energy for heating and lighting homes, generating electricity, and fueling motor vehicles. When produced from renewable resources and technologies, such as hydro, solar, and wind energy, hydrogen becomes a renewable fuel.
Composition of Hydrogen
Hydrogen is the simplest and most common element in the universe. It has the highest energy content per unit of weight—52,000 British Thermal Units (Btu) per pound (or 120.7 kilojoules per gram)—of any known fuel. Moreover, when cooled to a liquid state, this low-weight fuel takes up 1/700 as much space as it does in its gaseous state. This is one reason hydrogen is used as a fuel for rocket and spacecraft propulsion, which requires fuel that is low-weight, compact, and has a high energy content.
In a free state and under normal conditions, hydrogen is a colorless, odorless, and tasteless gas. The basic hydrogen (H) molecule exists as two atoms bound together by shared electrons. Each atom is composed of one proton and one orbiting electron. Since hydrogen is about 1/14 as dense as air, some scientists believe it to be the source of all other elements through the process of nuclear fusion. It usually exists in combination with other elements, such as oxygen in water, carbon in methane, and in trace elements as organic compounds. Because it is so chemically active, it rarely stands alone as an element.
When burned (or combined) with pure oxygen, the only by products are heat and water. When burned (or combined) with air, which is about 68% nitrogen, some oxides of nitrogen (Nitrogen Oxides or NOx) are formed. Even then, burning hydrogen produces less air pollutants relative to fossil fuels.
Hydrogen bound in organic matter and in water makes up 70% of the earth's surface. Breaking up these bonds in water allows us produce hydrogen and then to use it as a fuel. There are numerous processes that can be used to break these bonds. Described below are a few methods for producing hydrogen that are currently used, or are under research and development.
Most of the hydrogen now produced in the United States is on an industrial scale by the process of steam reforming, or as a byproduct of petroleum refining and chemicals production. Steam reforming uses thermal energy to separate hydrogen from the carbon components in methane and methanol, and involves the reaction of these fuels with steam on catalytic surfaces. The first step of the reaction decomposes the fuel into hydrogen and carbon monoxide. Then a "shift reaction" changes the carbon monoxide and water to carbon dioxide and hydrogen. These reactions occur at temperatures of 392° F (200 ° C) or greater.
Another way to produce hydrogen is by electrolysis. Electrolysis separates the elements of water—H and oxygen (O)—by charging water with an electrical current. Adding an electrolyte such as salt improves the conductivity of the water and increases the efficiency of the process. The charge breaks the chemical bond between the hydrogen and oxygen and splits apart the atomic components, creating charged particles called ions. The ions form at two poles: the anode, which is positively charged, and the cathode, which is negatively charged. Hydrogen gathers at the cathode and the anode attracts oxygen. A voltage of 1.24 Volts is necessary to separate hydrogen from oxygen in pure water at 77° Fahrenheit (F) and 14.7 pounds per square inch pressure [25° Celsius (C) and 1.03 kilograms (kg) per centimeter squared.] This voltage requirement increases or decreases with changes in temperature and pressure.
The smallest amount of electricity necessary to electrolyze one mole of water is 65.3 Watt-hours (at 77° F; 25 degrees C). Producing one cubit foot of hydrogen requires 0.14 kilowatt-hours (kWh) of electricity (or 4.8 kWh per cubic meter).
Renewable energy sources can produce electricity for electrolysis. For example, Humboldt State University's Schatz Energy Research Center designed and built a stand-alone solar hydrogen system. The system uses a 9.2 kilowatt (KW) photovoltaic (PV) array to provide power to compressors that aerate fish tanks. The power not used to run the compressors runs a 7.2 kilowatt bipolar alkaline electrolyzer. The electrolyzer can produce 53 standard cubic feet of hydrogen per hour (25 liters per minute). The unit has been operating without supervision since 1993. When there is not enough power from the PV array, the hydrogen provides fuel for a 1.5 kilowatt proton exchange membrane fuel cell to provide power for the compressors.
Steam electrolysis is a variation of the conventional electrolysis process. Some of the energy needed to split the water is added as heat instead of electricity, making the process more efficient than conventional electrolysis. At 2,500 degrees Celsius water decomposes into hydrogen and oxygen. This heat could be provided by a concentrating solar energy device. The problem here is to prevent the hydrogen and oxygen from recombining at the high temperatures used in the process.
Thermochemical water splitting uses chemicals such as bromine or iodine, assisted by heat. This causes the water molecule to split. It takes several steps—usually three—to accomplish this entire process.
Photoelectrochemical processes use two types of electrochemical systems to produce hydrogen. One uses soluble metal complexes as a catalyst, while the other uses semiconductor surfaces. When the soluble metal complex dissolves, the complex absorbs solar energy and produces an electrical charge that drives the water splitting reaction. This process mimics photosynthesis.
The other method uses semiconducting electrodes in a photochemical cell to convert optical energy into chemical energy. The semiconductor surface serves two functions, to absorb solar energy and to act as an electrode. Light-induced corrosion limits the useful life of the semiconductor.
Researchers at the University of Tennessee and U.S. Department of Energy's (DOE) Oak Ridge National Laboratory are researching ways to use photosynthesis to produce hydrogen from sunlight. The researchers extracted two photosynthetic complexes from spinach plants; called Photosystem I and Photosystem II. The two work together to produce carbohydrates for the plant. By attaching platinum atoms to the Photosystem I complexes, the researchers were able to produce hydrogen from visible light. Unfortunately, the process required the use of an added chemical that makes the overall process impractical, but the achievement shows potential. The researchers are working to combine the platinum-Photosystem I complexes with the Photosystem II complexes, forming a molecular system that can convert light and water directly into hydrogen, without help from an added chemical.
Biological and photobiological processes can use algae and bacteria to produce hydrogen. Under specific conditions, the pigments in certain types of algae absorb solar energy. The enzyme in the cell acts as a catalyst to split the water molecules. Some bacteria are also capable of producing hydrogen, but unlike algae they require a substrate to grow on. The organisms not only produce hydrogen, but can clean up pollution as well.
Research funded by DOE has led to the discovery of a mechanism to produce significant quantities of hydrogen from algae. Scientists have known for decades that algae produce trace amounts of hydrogen, but had not found a feasible method to increase the production of hydrogen. Scientists from the University of California (UC), Berkeley, and the U.S. DOE's National Renewable Energy Laboratory found the key. After allowing the algae culture to grow under normal conditions, the research team deprived it of both sulfur and oxygen, causing it to switch to an alternate metabolism that generates hydrogen. After several days of generating hydrogen, the algae culture was returned to normal conditions for a few days, allowing it to store up more energy. The process could be repeated many times. Producing hydrogen from algae could eventually provide a cost-effective and practical means to convert sunlight into hydrogen.
Another source of hydrogen produced through natural processes is methane and ethanol. Methane (CH4) is a component of "biogas" that is produced by anaerobic bacteria. Anaerobic bacteria occur widely throughout the environment. They break down or "digest" organic material in the absence of oxygen and produce biogas as a waste product. Sources of biogas include landfills, and livestock waste and municipal sewage treatment facilities. Methane is also the principal component of "natural gas" (a major heating and power plant fuel) produced by anaerobic bacteria eons ago. Ethanol is produced by the fermentation of biomass. Most fuel ethanol produced in the United States is made from corn.
Chemical engineers at the University of Wisconsin-Madison have developed a process to produce hydrogen from glucose, a sugar produced by many plants. The process shows particular promise because it occurs at relatively low temperatures, and can produce fuel-cell-grade hydrogen in a single step. Glucose is manufactured in vast quantities from corn starch, but can also be derived from sugar beets or low-cost waste streams like paper mill sludge, cheese whey, corn stover or wood waste.
The United States, Japan, Canada, and France have investigated thermal water splitting, a radically different approach to creating hydrogen. This process uses heat of up to 5,430°F (3,000°C) to split water molecules.
Potential Uses for Hydrogen
When properly stored, hydrogen as a fuel burns in either a gaseous or liquid state. Motor vehicles and furnaces can be converted to use hydrogen as a fuel. Hydrogen has actually been used in the transportation, industrial, and residential sectors in the United States for many years. Many people in the late 19th century burned a fuel called "town gas," which is a mixture of hydrogen and carbon monoxide. Several countries, including Brazil and Germany, still distribute this fuel. Hydrogen was used in early "hot-air" balloons, and later in airships (dirigibles) during the early 1900's. Gaseous hydrogen was used in 1820 as fuel for one of the earliest internal combustion engines. The U.S. Air Force had a secret, multi-million dollar program during the 1950's, code-named "Suntan," to develop hydrogen as a fuel for airplanes. Currently, industries use large quantities of hydrogen for refining petroleum, and for producing ammonia and methanol. The Space Shuttle uses hydrogen as fuel for its rockets. Automobile manufacturers have developed hydrogen-powered cars.
Burning hydrogen creates less air pollution than gasoline or diesel. Hydrogen also has a higher flame speed, wider flammability limits, higher detonation temperature, burns hotter, and takes less energy to ignite than gasoline. This means that hydrogen burns faster, but carries the danger of pre-ignition and flashback. While hydrogen has its advantages as a vehicle fuel it still has a long way to go before it can be used as a substitute for gasoline. This is mainly due to the investment required to develop a hydrogen production and distribution infrastructure.
However, things are getting started in this regard. Vehicle manufacturers Honda and BMW have set up hydrogen fueling stations as part of their efforts to develop fuel cell powered cars. At Honda's research and development center in Torrance, California, a PV array electrolyses hydrogen from water. The array generates enough hydrogen to power one fuel-cell vehicle. Additional power from the power grid is used to increase the hydrogen production capacity. The new station is supporting Honda's fuel cell vehicle development program for hydrogen production, storage, and fueling. Honda and a fuel cell developer are also working together on a "home" hydrogen refueling system for fuel cell vehicles. BMW opened a hydrogen fueling station at the company's engineering and emissions control test center in Oxnard, California. BMW is taking a different approach than most car companies, burning hydrogen directly in advanced internal-combustion engines, and is testing these vehicles at the Oxnard facility.
The California Fuel Cell Partnership (CaFCP) is also building a hydrogen infrastructure. The CaFCP commissioned its first "satellite" hydrogen fueling system in late October 2002, in Richmond, California; about 70 miles from the CaFCP headquarters and a primary refuel facility in West Sacramento. This extends the range over which the CaFCP's prototype fuel cell vehicles can be driven. The fueling system uses electrolysis to generate hydrogen from water and includes a storage unit capable of holding 104 pounds (47 kilograms) of hydrogen. It is capable of fueling a small fleet of vehicles and requires only one or two minutes per refueling.
In November 2002, the world's first hydrogen energy station that can provide fuel for vehicles and also produce electricity opened in Las Vegas Nevada. The station is located in the city's vehicle maintenance and operation service center. It combines an on-site hydrogen generator, compressor, liquid and gaseous hydrogen storage tanks, dispensing systems, and a stationary fuel cell. It is capable of dispensing hydrogen, hydrogen-enriched natural gas, and compressed natural gas. DOE is also working with the city to convert municipal vehicles to operate on hydrogen.
Fuel cells are a type of technology that uses hydrogen to produce useful energy. In fuel cells, electrolysis is reversed by combining hydrogen and oxygen through an electrochemical process, which produces electricity, heat, and water. The U.S. space program has used fuel cells to power spacecraft for decades. Fuel cells capable of powering automobiles and buses have been and are being developed. Several companies are developing fuel cells for stationary power generation. Most major automobile manufacturers are developing fuel cell powered automobiles.
Hydrogen could be considered a way to store energy produced from renewable resources such as solar, wind, biomass, hydro, and geothermal. For example, when the sun is shining, solar photovoltaic systems can provide the electricity needed to separate the hydrogen (as described above regarding Humboldt State University's Research Center). The hydrogen could then be stored and burned as fuel, or to operate a fuel cell to generate electricity at night or during cloudy periods.
In order to use hydrogen on a large scale, safe, practical storage systems must be developed, especially for automobiles. Although hydrogen can be stored as a liquid, it is a difficult process because the hydrogen must be cooled to -423° Fahrenheit (-253° Celsius). Refrigerating hydrogen to this temperature uses the equivalent of 25% to 30% of its energy content, and requires special materials and handling. To cool one pound (0.45 kg) of hydrogen requires 5 kWh of electrical energy.
Hydrogen may also be stored as a gas, which uses less energy than making liquid hydrogen. As a gas, it must be pressurized to store any appreciable amount. For large-scale use, pressurized Hydrogen gas could be stored in caverns, gas fields, and mines. The hydrogen gas could then be piped into individual homes in the same way as natural gas. Though this means of storage is feasible for heating, it is not practical for transportation because the pressurized metal tanks used for storing hydrogen gas for transportation are very expensive.
A potentially more efficient method of storing hydrogen is in hydrides. Hydrides are chemical compounds of hydrogen and other materials. Research is currently being conducted on magnesium hydrides. Certain metal alloys such as magnesium nickel, magnesium copper, and iron titanium compounds, absorb hydrogen and release it when heated. Hydrides, however, store little energy per unit weight. Current research aims to produce a compound that will carry a significant amount of hydrogen with a high energy density, release the hydrogen as a fuel, react quickly, and be cost-effective.
A company in Utah, Power Ball Technologies, has developed a process in which sodium metal is pelletized and encapsulated with polyethylene plastic. The pellets can then be containerized, transported, and then opened in a patented hydrogen generator to produce hydrogen gas. According to the company, each gallon of these pellets is capable of producing 1,307 gallons of hydrogen gas, which is an equivalent hydrogen storage density more than 7 times greater by volume than a compressed hydrogen tank storing hydrogen at 3,000 psi.
The Cost of Hydrogen
Currently the most cost-effective way to produce hydrogen is steam reforming. According to the U.S. Department of Energy, in 1995 the cost was $7.39 per million Btu ($7.00 per gigajoule) in large plant production. This assumes a cost for natural gas of $2.43 per million Btu ($2.30 per gigajoule). This is the equivalent of $0.93 per gallon ($0.24 per liter) of gasoline. The production of hydrogen by electrolysis using hydroelectricity at off peak rates costs between $10.55 to $21.10 per million Btu ($10.00 to $20.00 per gigajoule).
Hydrogen Research in the United States
Recognizing the potential for hydrogen fuel, the U.S. Department of Energy (DOE) and private organizations have funded research and development (R&D) programs for several years. DOE has a major effort to develop hydrogen as a major fuel within the next few decades. Information on this program is available on the World Wide Web at: www.eere.energy.gov/hydrogenandfuelcells.htm
Hydrogen Fuel Cells
Hydrogen's potential use in fuel and energy applications includes powering vehicles, running turbines or fuel cells to produce electricity, and generating heat and electricity for buildings. The current focus is on hydrogen's use in fuel cells.
A fuel cell works like a battery but does not run down or need recharging. It will produce electricity and heat as long as fuel (hydrogen) is supplied. A fuel cell consists of two electrodes—a negative electrode (or anode) and a positive electrode (or cathode)—sandwiched around an electrolyte. Hydrogen is fed to the anode, and oxygen is fed to the cathode. Activated by a catalyst, hydrogen atoms separate into protons and electrons, which take different paths to the cathode. The electrons go through an external circuit, creating a flow of electricity. The protons migrate through the electrolyte to the cathode, where they reunite with oxygen and the electrons to produce water and heat. Fuel cells can be used to power vehicles or to provide electricity and heat to buildings.
The primary fuel cell technologies under development are:
Phosphoric Acid Fuel Cells
A phosphoric acid fuel cell (PAFC) consists of an anode and a cathode made of a finely dispersed platinum catalyst on carbon paper, and a silicon carbide matrix that holds the phosphoric acid electrolyte. This is the most commercially developed type of fuel cell and is being used in hotels, hospitals, and office buildings. The phosphoric acid fuel cell can also be used in large vehicles, such as buses.
Proton-Exchange Membrane Fuel Cells
The proton-exchange membrane (PEM) fuel cell uses a fluorocarbon ion exchange with a polymeric membrane as the electrolyte. The PEM cell appears to be more adaptable to automobile use than the PAFC type of cell. These cells operate at relatively low temperatures and can vary their output to meet shifting power demands. These cells are the best candidates for light-duty vehicles, for buildings, and much smaller applications.
Solid Oxide Fuel Cells
Solid oxide fuel cells (SOFC) currently under development use a thin layer of zirconium oxide as a solid ceramic electrolyte, and include a lanthanum manganate cathode and a nickel-zirconia anode. This is a promising option for high-powered applications, such as industrial uses or central electricity generating stations.
Direct-Methanol Fuel Cells
A relatively new member of the fuel-cell family, the direct-methanol fuel cell (DMFC) is similar to the PEM cell in that it uses a polymer membrane as an electrolyte. However, a catalyst on the DMFC anode draws hydrogen from liquid methanol, eliminating the need for a fuel reformer.
Molten Carbonate Fuel Cells
The molten carbonate fuel cell uses a molten carbonate salt as the electrolyte. It has the potential to be fueled with coal-derived fuel gases or natural gas.
Alkaline Fuel Cells
The alkaline fuel cell uses an alkaline electrolyte such as potassium hydroxide. Originally used by NASA on space missions, it is now finding applications in hydrogen-powered vehicles.
Regenerative or Reversible Fuel Cells
This special class of fuel cells produces electricity from hydrogen and oxygen, but can be reversed and powered with electricity to produce hydrogen and oxygen.
The following publications provide additional information about hydrogen fuel. Contact sources to confirm availability and prices before ordering. This list was reviewed in February 2003.
Articles and Conference Papers
- "Cookin' on Hydrogen Stove Burner Conversion," D. Booth, W. Pyle, (No. 33) pp. 28-30, 2-3/1993.
- "Heatin' with Hydrogen," W. Pyle, J. Healy, R. Cortez, D. Booth, (No. 34), pp-26-29, 4-5/1993.
- "Hydrogen Basics," A. Potter, M. Newell, (No. 32) pp. 42-45, 12/1992 – 1/1993.
- "Hydrogen Fuel," L. Spicer, (No. 22) pp. 32-34, 4-5/1991.
- "Hydrogen Storage," W. Pyle, (No. 59) pp. 14-20, 6-7/1997.
- "Solar Hydrogen by Electrolysis," W. Pyle, J. Healy, R. Cortez, (No. 39) pp. 32-38, 2-3/1994.
- "The Schatz PV Hydrogen Project," R. Perez, (No. 22) pp. 26-30, 4-5/1991.
- "Water Electrolyzers," L. Spicer, (No. 26) pp. 34-35, 12/1991-1/1992.
Articles from Solar Today, American Solar Energy Society (ASES), 2400 Central Avenue, Unit G 1, Boulder, CO 80301: Phone: (303) 443 3130; Email: firstname.lastname@example.org ; World Wide Web: www.ases.org. Selected articles include:
- "Florida's Hydrogen Research," I. Melody, (7:5) pp. 14-16, 9-10/1993.
- "Hydrogen Fuel from the Sun," P. Lehman, C. Parra, (8:5) pp. 20-22, 9-10/1994.
- "Hydrogen Powered Ice Cream," C Para, S. Ornelas, and J. Zoellick, (13:4) pp. 30–33, 8-9/1999.
- "Renewable Hydrogen Energy Systems," J. Ogden, (7:5) pp. 17-18, 9-10/1993.
- "Solar Energy Hydrogen – Partners in a Clean Energy Economy," C. Linkous, (13:4) pp. 22-25, 8-9/1999.
- "Solar Hydrogen: A Sustainable Energy Option," C. Thomas, (7:5) pp. 11-13, 9-10/1993.
- "Solar Hydrogen for Transportation," J. Ogden, (9:1) pp. 25-27, 1-2/1995.
Miscellaneous Articles and Conference Papers
- "The Car of His Dreams," C. Levesque, Public Utilities Fortnightly,(139:4) pp. 23-26, February 15, 2001.
- "The Development of a Hydrogen-Fueled Internal Combustion Engine," J. Fiene, et al., Solar Forum 2001: Annual American Solar Energy Society Conference, Washington, DC, April 21-25, 2001.
- "From Fuel Cells to a Hydrogen-based Economy," A. Lovins and B. Williams, Public Utilities Fortnightly, (139:4) pp. 12-21, February 15, 2001.
- "Hydrogen Station Using Solar Becomes First Such Facility in Los Angeles Area," Ed., Solar & Renewable Energy Outlook, (27:15) p. 170, August 1, 2001.
- "Let's Be Rational About Hydrogen as a Vehicular Fuel," H. Linden, Public Utilities Fortnightly, (140:6) pp. 8-9, March 15, 2002
- "Metal Hydrides for Solar Thermal Applications," G. Lloyd, K. Kim, and A. Razani, Solar 98: Annual American Solar Energy Society Conference, Albuquerque, New Mexico, June 14-17, 1998; pp. 439-444.
- "Renewable Fuels: Harnessing Hydrogen," C. Chornet and S. Czernick, Nature, (148) August 29, 2002.
- "Routes To a Hydrogen Economy," S. Dunn, Renewable Energy World, (4:4) pp. 19-29, July/Aug 2001.
- "Sustained Photobiological Hydrogen Gas Production upon Reversible Inactivation of Oxygen Evolution in the Green Alga Chlamydomonas reinhardtii," A. Melis, et al. Plant Physiology, (122) pp. 127-136, January 2000.
- Energy: The Solar-Hydrogen Alternative, J. Bockris, John Wiley & Sons, New York, New York, 1976. 376 pp., Out of print. ISBN 0-470-08429-4.
- Fuel from Water: Energy Independence with Hydrogen, M. Peavey, Merit Inc., 1993. Available from Real Goods/Gaiam Inc., 360 Interlocken Boulevard, Suite 200, Broomfield, CO 80021-3492; Phone: (800) 762-7325; World Wide Web: www.realgoods.com . 251 pp., $25.00, Product No. 80-210.
- The Hydrogen Economy: The Creation of the Worldwide Energy Web and the Redistribution of Power on Earth, J. Rifkin, Putman, 2002. 285 pp. Available in bookstores.
- Hydrogen Fuel for Surface Transportation, J. Heffel, et al, Society of Automotive Engineers (SAE), 1996. Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001; Phone: (724) 776-4970; Fax: (724) 776-5760; World Wide Web: www.sae.org. $99.95, ISBN: 1560916842.
- Hydrogen Futures: Towards a Sustainable Energy System, S. Dunn, Worldwatch Institute, 2001. Available from Worldwatch Institute, Publications, P.O. Box 879, Oxon Hill, MD 20797; Phone: (888) 544-2303 or (301) 567-9522; Fax: (301) 567-9553; Email: email@example.com ; World Wide Web: www.worldwatch.org . 90 pp., $5.00, Worldwatch Paper 157.
- The Keys to the Car, J. MacKenzie, World Resources Institute, 1994. Available from World Resources Institute Publications, c/o Hopkins Fulfillment Service, P.O. Box 50370, Baltimore MD 21211-4370; Phone: (800) 537-5487 (publications); Fax: (410) 516-6998; World Wide Web: www.wri.org. $20.00.
- The Phoenix Project, H. Braun, Sustainable Partners, Inc. Available from Sustainable Partners, 6128 North 28th Street, Phoenix, AZ 85016; Phone: (602) 955-4555; Fax: (602) 955-5444; Email: firstname.lastname@example.org; World Wide Web: www.phoenixproject.net. 366 pp., $28.00.
- The Solar-Hydrogen Energy Economy: Beyond the Age of Fire, L. Skelton, Van Nostrand Rheinhold, 1984. 200 + pages, Out of print. ISBN 0-442-28221-4
- Solar Hydrogen: Moving Beyond Fossil Fuels, J. Ogden and R. Williams, World Resources Institute, 1989. 123 pp., Out of print. ISBN 0-915825-38-4.
Tomorrow's Energy – Hydrogen, Fuel Cells and the Prospects for a Cleaner Planet, P. Hoffman, The MIT Press, 2001. Available from MIT Press, c/o Triliteral, 100 Maple Ridge Drive, Cumberland, RI 02864; Phone: (800) 405-1619 or (401) 658-4226; Fax: (800) 406-9145 or (401) 531-2801; Email: email@example.com ; World Wide Web: mitpress.mit.edu. 320 pp., $32.95, ISBN: 0262082950.
Unless otherwise indicated, the reports cited below can be purchased from the:
National Technical Information Service (NTIS)
5285 Port Royal Road, Springfield, VA 22161
Phone: (800) 553?6847 or (703) 605-6000; Fax: (703) 605-6900
World Wide Web: www.ntis.gov
NTIS adds costs for shipping and handling. Check the price and availability before placing an order.
- Assessment of Methods for Hydrogen Production Using Concentrated Solar Energy, G. Glatzmaier, D. Blake, and S. Showalter, National Renewable Energy Laboratory, 1998. 24 pp., $ 23.00, NTIS Order No. DE98001924.
- Conversion of Municipal Solid Waste to Hydrogen, J. Richardson, et al., Lawrence Livermore National Laboratory, 1995. 27 pp., $28.50, NTIS Order No. DE95016063.
- Costs of Storing and Transporting Hydrogen, W. Amos, National Renewable Energy Laboratory, 1998. 220 pp., $47.00, NTIS Order No. DE00006574.
- FY 2002 Annual Operating Plan: Hydrogen Program, U.S. Department of Energy, 2001. Available on the World Wide Web at: www.eere.energy.gov/hydrogenandfuelcells/news.html. 231 pp.
- The Green Hydrogen Report. The 1995 Progress Report of the Secretary of Energy's Technical Advisory Panel, National Renewable Energy Laboratory, 1995. 23 pp., $28.50, NTIS Order No. DE95009213.
- Hydrogen and the Materials of a Sustainable Energy Future, M. Zalbowitz (ed.), Los Alamos National Laboratory, 1997. 180 pp., $44.00, NTIS Order No. DE97002453.
- Hydrogen as a Transportation Fuel: Costs and Benefits, G. Lawrence, Lawrence Livermore National Laboratory, 1996. 116 pp., $41.00, NTIS Order No. DE96010888.
- Hydrogen Energy for Tomorrow: Advanced Hydrogen Production Technologies, National Renewable Energy Laboratory, 1995. 4 pp., $10.00, NTIS Order No. DE95000270.
- Hydrogen Energy for Tomorrow: Advanced Hydrogen Transport and Storage Technologies, National Renewable Energy Laboratory, 1995. 4 pp., $10.00, NTIS Order No. DE95000271.
- Hydrogen Program Plan: FY 1993-FY 1997, National Renewable Energy Laboratory, 1992. 94 pp., $34.00, NTIS Order No. DE92010556.
- Hydrogen Storage for Vehicular Applications: Technology Status and Key Development Areas, S. Robinson, J. Handrock, Sandia National Laboratories, 1994. 47 pp., $28.50, NTIS Order No. DE94011626.
- Integrated Technical and Economic Assessments of Transport and Storage of Hydrogen, G. Berry and J. Smith, Lawrence Livermore National Laboratory, 1994. 12 pp., $28.50, NTIS Order No. DE94013145/WDE.
- Liquid Hydrogen As a Propulsion Fuel, 1945-1959, J. Sloop, National Aeronautics and Space Administration (NASA) History Series (SP4404). Accessible on the World Wide Web at: www.hq.nasa.gov/office/pao/History/SP-4404/contents.htm.
- On-Board Hydrogen Storage Systems Using Metal Hydrides, L. Heung, Westinghouse Savannah River Company, 1997. 18 pp., $23.00, NTIS Order No. DE97060222.
- Survey of the Economics of Hydrogen Technologies, C. Padro and V. Putsche, National Renewable Energy Laboratory (NREL), 1999. Possibly available from the NREL Document Distribution Service, 1617 Cole Blvd, Golden, CO 80401. 54 pp.
- Sustainable Hydrogen Production, D. Block, Florida Solar Energy Center, 1996. 103 pp., $41.00, NTIS Order No. DE96006063/LL.
Toward Tomorrow's Energy: Speeding the Commercial Use of Fuel Cells and Hydrogen, R. Rose and P. Hoffman, Progressive Policy Institute (PPI), 2003. Available on the World Wide Web at: http://www.ppionline.org/ppi_ci.cfm?knlgAreaID=144&subsecid=304&contentid=251177.