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Fuel Cell Facts
Fuel cells generate electricity through an electrochemical reaction, known as reverse electrolysis. This reaction combines hydrogen and oxygen to form water vapor, heat and electricity. All three of the by-products of this reverse electrolysis reaction can be further utilized by the fuel cell system. Waste heat can be utilized for space heating and cooling. The water vapor can be captured and used as the feedstock for additional hydrogen and the electricity is channeled into an external circuit where it is used by any electric appliance.
- Environmental - Fuel Cells achieve high fuel efficiency while emitting extremely low emissions.
- Engineering - Fuel cells operate on a wide variety of fuels, utilize electrochemical reactions and contain no moving parts. These features make them simple to operate, quiet and extremely reliable.
One advantage of fuel cells is their fuel flexibility. With the proper reforming technology, fuel cells can extract hydrogen from a wide variety of currently available fossil fuels (e.g. Natural gas, methanol, coal, etc.). From fossil fuels, fuel cells utilize one natural element as their fuel, hydrogen, the most abundant element on Earth. In addition to fossil fuels, hydrogen can be generated renewably from water and other photobiological means.
There are four main types of fuel cells distinguished by the electrolyte used in the individual cells. The different types of fuel cells are; polymer electrolyte membrane or proton exchange membrane (PEM), molten carbonate (MCFC), phosphoric acid (PAFC) and the solid oxide fuel cell (SOFC).
Sir William Grove first demonstrated the technology behind fuel cells in 1839. The gas battery, later named the fuel cell, reversed the well-understood principal of electrolysis to generate an electrical current. Grove's invention was largely a curiosity as the age was captivated by the horseless carriage and the large reserves of petroleum that were being discovered. Fuel cells remained in obscurity until 1960 when the upstart government agency, The National Aeronautic and Space Administration (NASA), began looking for a practical power source for extended missions to space. Through research and development sponsored by NASA and private industry, the fuel cell is poised to become a replacement for the internal combustion engine and redesign the utility industry by making energy cleaner, cheaper and portable.
In the near future, fuel cells will play an increasing role in everyday life. Soon fuel cell powered cars and trucks will be cruising the streets of your town emitting nothing more than harmless water vapor. Fuel cells will find their way into cell phones and laptop computers whose battery life is measured in days instead of hours. Your house or office will have a fuel cell that replaces a conventional furnace, providing heat and electricity free from the disruptions associated with the utility's electric grid. Most of the companies planning to manufacture fuel cells are still in the research and development stage of production. Once their systems satisfy the manufacturers' stringent requirements for performance and safety, the fuel cell systems will be available to the general public.
Hydrogen is a medium for storing energy. To be useful as an energy carrier all fuels, such as gasoline and natural gas, have a characteristic of being volatile. Hydrogen's benefits differ from the fossil fuels commonplace in an advanced energy utilizing society such as in the United States.
Hydrogen is non-toxic.
Gasoline and oil are extremely toxic and poisonous humans along with wildlife when unintentionally released into the environment. If a hydrogen spill occurred, the hydrogen would evaporate almost immediately leaving only water behind. Oil and gasoline, on the other hand, require immense cleanup efforts with the result being that most of the spilled toxic gasoline or oil seeps into the surrounding ecosystem wrecking irreparable harm.
Hydrogen has suffered from image problems in the past.
Hydrogen is commonly associated with two things; the Hindenburg disaster and the hydrogen bomb. Recently, researchers trying to determine the exact cause of the fire have investigated the Hindenburg accident. In 1937 the Hindenburg was destroyed attempting to land in an electrical storm outside of Lakehurst, NJ. Witness reported observing a blue glow on the top of the ill-fated airship. The blue glow is often indicative of extremely high electrical activity. The current school of thought indicates that the electricity around the skin of the ship probably ignited the skin. Addison Bain, a retired NASA safety expert, has analyzed the remaining fragments of the zeppelin's exterior fabric skin. His findings indicated that the skin was composed of either cellulose nitrate or cellulose acetate. Aluminum flakes were combined with these materials to reflect sunlight in order to keep the airship cool. The combination of cellulose nitrate and aluminum is commonly known today as the recipe for rocket fuel, as anyone who has watched a rocket launch knows, is highly flammable. The hydrogen contained in the airship did burn, but remember that hydrogen is lighter than air and the flames would have been streaking upwards not down onto the passenger cabin. All of the people who died in the disaster, died from falling to their death or burning to death from flaming, dripping diesel fuel. All of the survivors rode the airship down to the ground and safety. The size of the Hindenburg needs to be kept in mind. A passenger car or fuel cell operating on hydrogen would never have such a large amount of hydrogen stored in a flimsy cloth bag. All of the fuel cell systems and hydrogen storage techniques are engineered with safety being a paramount concern. The composite tanks used to store liquid and gaseous hydrogen are required to undergo rigorous safety testing before they are certified for hydrogen storage. The other reason hydrogen has received negative press in the past is its relationship to the hydrogen bomb. In order for hydrogen atoms to fuse tighter, like the reaction in a hydrogen bomb, special circumstances have to occur. Hydrogen will only fuse under extremely high heat and pressures that would never be found in a fuel cell system or hydrogen storage device.
The Union of Concerned Scientists have issued a report stating that, "If the entire U.S. passenger vehicle fleet were powered by hydrogen FCVs (fuel cell vehicles), the amount of water emitted annually (assuming no losses) would be 0.005% the rate of natural evapotranspiration, water that is released by plants during photosynthesis, in the continental U.S."
By supporting the research and development of fuel cells, the United States Government is developing clean energy sources for our future while strengthening the United States' competitiveness on the world energy market. Many governmental departments, including the Defense Department, the Department of Energy, and the Department of Transportation have fuel cell programs in their respective areas. All of these programs are leading towards the commercialization of fuel cell technology through partnering with private industry. The Federal Government supports research and development through monetary contributions towards research that is considered risky by industry and by creating the initial markets for expensive new technology. For example, the Climate Change Fuel Cell program provides cost sharing regarding the purchase of a fuel cell system. Hydrogen and fuel cells only enjoy a fraction of the subsidies that the nuclear and fossil fuel industries receive each year.
Japan, Germany and Canada are all intensively developing fuel cell technology in their respective countries. Many of the manufacturers located in these countries enjoy governmental support that far surpasses what the United States Government is providing at home. These countries realize that fuel cells and hydrogen are the most likely replacement for our current energy system and with this in mind; they are trying to develop future industries today.
By supporting fuel cell development, the United States Government will achieve the goals of strengthening our national energy security, improving environmental conditions and developing an industry. The United States is dependent on politically unstable and unfriendly regions of the globe for its supply of oil. Currently, the United States imports 50% of its oil. According to the Department of Energy this number is expected to grow to 65% by 2020. Fuel cells, with their characteristic fuel flexibility, allow the United States to dramatically reduce its dependence on foreign energy sources and reduce its unbalanced foreign trade debt. By eliminating or greatly reducing the emissions associated with fossil fuels, a noticeable improvement in the environmental conditions in many major metropolitan areas will occur. This results in a reduction of pollution-related medical conditions and a dramatic increase in the quality of life for residents of these areas. These two benefits combine to form incalculable monetary benefits. The United States has the opportunity to develop a new industry. Fuel cells and related industries can expand and improve the United States economy by creating new jobs in fuel cell manufacturing, sales, service and hydrogen production and storage. As costs fall, fuel cell technology becomes appealing to utilities in developing countries improving our exports and reducing our foreign trade deficit.
In a residential fuel cell system there are three main components. The source of hydrogen, the actual fuel cell stacks and the power condition unit. The hydrogen can either be reformed from fossil fuels (i.e. natural gas, propane, etc) or the unit can be coupled to a renewable energy source and generate hydrogen through electrolysis of water. The fuel cell stack is the part, which converts the hydrogen and oxygen into electricity, water vapor and heat. The last piece is the power conditioner. This inverts the DC current from the fuel cell into AC current that many household appliances operate on.
Many factors enter into what your actual savings will be. These factors include; individual electricity consumption, geographic location, the particular utility, if utilizing a reformer the price of natural gas or propane, the avoided costs of installing lines to your residence when located in an off-grid area, etc.
The ability to sell electricity back into the grid depends on the geographic location of the unit. Many states have net metering laws, which allow qualified customers to sell surplus electricity back to the grid. Individual states vary on the amount of electricity each individual is allowed to sell, consult your local laws and ordinances.
When a solar or wind system is coupled with an electrolyzer, the fuel cell system provides a completely renewable source of electricity. By generating hydrogen with a renewable system, the hydrogen becomes a storage medium for the energy contained in the captured sunlight or wind. Hydrogen and the fuel cell are able to replace the toxic, heavy, limited-life batteries currently used as energy storage. Generating hydrogen is non-toxic method to remove the temporal nature of renewable energy systems.
Vehicles powered by fuel cells combine the attractive advantages of battery-powered cars and the convenience of an internal combustion engine. Fuel cells operate quietly and are zero to low emissions, comparable to a battery-powered vehicle. Fuel cell powered vehicles offer the range, power, responsiveness and rapid fueling that the internal combustion engine provides. Unlike battery-powered cars, fuel cells do not require lengthy recharge times and will not transfer the pollution from the tailpipe over the grid to a central generating facility. The batteries used in automobiles are extremely heavy which limits the vehicles range and capacity. The batteries are also composed of toxic materials and have a limited lifetime leading to disposal problems. Fuel cell vehicles operating on pure hydrogen produce only water vapor and heat as emissions while fuel cells reforming fossil fuels into hydrogen would be classified as ultra-low emission vehicles.
Hydrogen, when burned in a combustion engine is a huge improvement in terms of emissions when compared to fossil fuels. Burning hydrogen does release low amounts of nitrous oxide, a component of smog, into the atmosphere. This occurs whenever high temperature combustion occurs in the presence of oxygen. Other pollutants are also released as trace amounts of lubricants are burned in the process. The main reason to employ fuel cells instead of combusting hydrogen has to do with efficiency. Anytime a fuel is ignited and burned the overall efficiency is limited by the laws of physics, especially Carnot's Law, to around 10%. This is due to efficiency losses associated with heat and the additional steps necessary before the fuel is transformed into usable energy. A fuel cell directly converts the hydrogen fuel into electricity and is therefore inherently more efficient. A fuel cell skips the steps, associated with combustion generation, of first converting the fuel into heat, then mechanical energy and finally into energy. In an automobile engine 100 scf of hydrogen would power the car for about 6 to 12 miles. That same amount of hydrogen in a fuel cell powered car could travel 12 to 24 miles.
It would take about 10 Nm3 of hydrogen gas to equal the energy present in 1 gallon of gasoline or 8.3 pounds of coal.
Below is an example calculation for determining the cost of operating a 1kW fuel cell on hydrogen. In this example a compressed hydrogen cylinder with a capacity of 200 cubic feet of hydrogen at normal temperature and pressure (NTP) is used. The purity of hydrogen consumed is 99.99999%.
1. Compressed hydrogen cylinder - 200 cu.ft. of hydrogen (NTP) or 5667.37 Liters.
2. Cost of hydrogen cylinder is $100 + $14/month (rental) +$20 (delivery)
3. 1kW fuel cell system with a hydrogen consumption rate of 13 Standard Liter/min.
4. Number of hours of operation at 1kW = 5667.37/13 = 7.26 hours
Costs: Example 1:
Costs: Example 2: