A fuel cell utilizes basic electrolytic properties of oxygen and hydrogen molecules to produce electricity. The transfer of electrons between the molecules can be used to supply direct current power. The supplied electrical power will be continuous as long as both oxygen and hydrogen flows are maintained and constant.
The proton exchange membrane fuel cell (PEMFC) uses platinum-based electrodes and the electrolyte is a humidified polymer membrane that is an electric insulator, but permeates hydrogen ions (H+).
The operating temperature is 50-100°C, temperatures above 100°C is not feasible as the membrane needs to stay humid.
The PEMFC uses hydrogen and oxygen, and produces water in addition to electricity and heat. If other fuel sources than hydrogen are to be used they need to be converted to hydrogen prior to injection to the PEMFC. For hydrocarbons, this means steam-reforming and water-gas-shift.
Proton Exchange Membrane Fuel Cell
The PEM fuel cell is a mature technology that has been successfully used both in marine and other high energy applications.
The technology is available for a number of applications. The relative maturity of the technology also leads to a relatively low cost. The operation requires pure hydrogen, and the operating temperature is low. The main safety aspects are thus related to the use and storage of hydrogen on a vessel.
Energy conversion with a PEM fuel cell, from hydrogen to electricity, would essentially result in water as the only emission and low quality heat, with the low temperature providing however high tolerance for cycling operation.
The efficiency is moderate, around 50-60%, and, with the low operating temperature, heat recovery is considered not to be feasible.
The modules currently have a size of up to 120kW, and the physical size is small, which is positive for applications in transport, remarkably for marine use.
Fuel Cell System Benefits
A fuel cell operating on pure hydrogen emits zero emissions at the source.
Some stationary fuel cells use natural gas or hydrocarbons as a hydrogen feedstock, but even these systems produce far fewer emissions than conventional power plants.
Combining a gas engine with stationary fuel cell, results in a 67 percent reduction in emissions, relative to a standalone gas engine.
Fuel cells also reduce noise emissions. Since fuel cells do not rely on combustion and have few moving parts, they are very quiet – about 60 decibels, the volume of a typical conversation. And since noise pollution is all but eliminated, fuel cells can be sited indoors or outdoors without being obtrusive.
Emissions from fuel cells are so low that some areas of the United States have exempted fuel cells from air permitting requirements.
Because fuel cells create energy electrochemically, and do not burn fuel, they are fundamentally more efficient than combustion systems.
Fuel cell systems today achieve 40-50 percent fuel-to-electricity efficiency using hydrocarbon fuels such as natural gas. When a fuel cell is sited near the point of energy use, as in some stationary applications, the waste heat can be captured for cogeneration, which is also referred to as combined heat and power.
In large-scale building systems this cogeneration can reduce facility energy costs by 20-40 percent. Using this waste heat can bring the system efficiency up over 85 percent, and in some real world cases higher than 90 percent. This compares favorably to the relatively low efficiency of the electric grid, which is about 30 percent.
Fuel cell passenger vehicles are expected to be up to three times more efficient than internal combustion engines which, on average, have efficiencies between 16-20 percent.
Highly reliable power is essential to many businesses, as well as residential communities. It is estimated that U.S. businesses lose $29 billion annually from computer failures due to power outages.
Data centers, banks, hospitals, grocery stores and telecommunications companies all rely on constant power to maintain operations. These buildings require power that is available 99.9999% of the time, and in many areas the electrical grid does not meet this requirement.
Fuel cells can generate power independent of the grid, providing crucial backup power to a grid-connected building that can eliminate the fear of losing power. Fuel cells can also be configured to be a building’s primary source of power.
Many banks, data centers, and other electricity intense buildings require high-quality power. Fuel cells provide a constant power output that does not have the same voltage surges and sags as the electric grid.
Smooth power output is also important for fuel cell-powered materials handling vehicles such as forklifts, as batteries lose voltage as they deplete, making it more difficult to do the same amount of work over the course of a shift.
Fuel cells also have a conditioner that ensures high quality power output.
Most fuel cells run on hydrogen and all will continue to generate power as long as fuel is supplied.
The source of the hydrogen does not matter in most fuel cells. A fuel cell system can include a fuel reformer that generates hydrogen from a diverse range of sources including fossil fuels such as natural gas, propane and coal, alcohol fuels such as methanol and ethanol, and from hydrogen compounds containing no carbon such as ammonia or borohydride.
In addition, biomass, methane, landfill gas or anaerobic digester gas from wastewater treatment plants may be used as fuel sources, and are considered renewable in several states and countries.
Hydrogen produced via water electrolysis provides the cleanest fuel pathway, and can be achieved through conventional grid power, nuclear power, solar or wind.
Hydrogen can be produced from domestic resources, eliminating the need to import foreign oil. Passenger vehicles alone consume six million barrels of oil every day, equivalent to 85 percent of oil imports. If just 20 percent of cars in the U.S. were fuel cell vehicles, oil imports could be cut by 1.5 million barrels per day.
Because fuel cells do not have to be connected to the electrical grid, they are a form of distributed generation that allows the country to move away from reliance on high voltage central power generation, which is vulnerable to attacks and natural disasters.
Fuel cells aid critical communications networks, providing crucial connections and continuous power during weather events such as hurricanes and snow storms that can cripple the grid.
Fuel cells have proven themselves during these violent weather events over the past few years, providing reliable backup power to schools, hospitals, and grocery stores, all of which deliver crucial goods and services to communities.
Fuel cells are also rugged, and can be sited in harsh terrain, extreme climates, and rural areas without infrastructure.
Whether in rough terrain or extreme climates, fuel cells can be sited wherever power is needed.
Uninterrupted power supply (UPS) units currently backup cell towers in remote locations, and portable fuel cells have proved themselves alongside the U.S. military in theater, providing soldiers critical power with low heat and noise signatures in extreme environments.
Fuel cells are modular, and can be scaled up depending on the power needs of a facility.
Larger fuel cells can be linked together to achieve multi-megawatt outputs, while smaller ones can satisfy specific power needs at residential, telecommunications, or small commercial facilities.
Because they use no combustion or moving parts, fuel cells are much quieter than many incumbent technologies. This allows them to be sited in places such as parks or residential areas.
The Sheraton hotel in San Diego, has four fuel cells installed next to their tennis courts! As the chart below illustrates, most conversation takes place around a noise level of 60 dBa, which is approximately the noise level measured at 1 meter for all fuel cell units between 1-250 kW regardless of application.
When integrated into a system, air pumps and/or fans are typically needed, which are usually the only source of noise on a fuel cell power unit or vehicle.
Fuel cells are complementary, not competitors, with other electricity generation technologies, particularly renewable ones.
Some power systems utilize a fuel cell either integrated or co-located with on-site solar PV, wind turbines, and/or batteries. In these systems, the fuel cell often provides a stable, baseload power supply to support the intermittent renewable systems. Some warehouses today use hybrid forklifts, which have an onboard fuel cell that is used to recharge the battery.
Telecom backup stations have employed hybrid renewable energy systems for several years, installing fuel cells alongside solar, wind, and batteries to harden a site’s power and ensure continuous operation.
Fuel cells are being developed for portable electronic devices such as laptops and cell phones. Fuel cells provide a much longer operating life than a battery, and since fuel cells have a higher energy density, they are lighter than an equivalent battery system.
Fuel cells do not require recharging; as long as fuel is present, the system will continuously generate electricity. For portable fuel cells liquid, solid, or gaseous fuel in a reusable canister could be replaced in a moment.
U.S. military forces are assessing the value of portable fuel cells in the field and have deployed demonstration units with ground forces in Afghanistan to test their readiness. Soldiers need a lot of power, but they already carry so much weight, and batteries are heavy.
Fuel cells are lighter and can operate 10 times longer than conventional batteries, and have the added benefits of lower heat and noise signatures.
Source: hfcarchive.org
FAQ’s
When were Fuel Cells Invented?
The first fuel cell was built in 1839 by Sir William Grove, a Welsh judge and gentleman scientist, who conducted dozens of experiments using his “gas battery.”
More than a century later, equipment manufacturer Allis Chalmers plowed a Wisconsin alfalfa field using fuel cell-powered tractor (1959).
Serious interest in the fuel cell as a practical energy generator did not begin until the 1960′s, when the U.S. space program chose fuel cells over riskier nuclear power and more expensive solar energy, using fuel cells to furnish power for the Gemini and Apollo spacecraft and electricity and water for the space shuttle.
Also in the 1960s, the first passenger vehicle, a prototype van, was built by GM (1966); major auto manufacturers began more concerted fuel cell development efforts in the 1990s.
What fuels can be used in a fuel cell?
Fuel cells operate using hydrogen, the most abundant element in the universe. Hydrogen combines readily with other elements and forms compounds. On Earth, hydrogen is chiefly combined with oxygen in the form of water.
One method of hydrogen production is via electrolysis – passing electricity through water between two electrodes. This process that can be made extremely clean and emissions-free by using electricity generated by renewable resources, such as solar or wind power.
Hydrogen is also present in organic matter, such as biomass and hydrocarbons. Thus any hydrogen-rich material can serve as a possible fuel source for fuel cells:
Hydrocarbon fuels – methanol, ethanol, natural gas, petroleum distillates, liquid propane and gasified coal – yield hydrogen in a process called reforming.
Although the use of reformed hydrogen does lead to some carbon dioxide emissions, highly-efficient fuel cell systems produce significantly lower emissions than conventional power plants. In fact, emissions are so low that some areas of the United States have exempted fuel cells from air permitting requirements.
Hydrogen can be extracted from renewable biogases, such as landfill gas produced during natural bacterial decomposition of organic material, or anaerobic digester gas generated at wastewater treatment plants, breweries and agricultural processing facilities. Hydrogen made from renewable energy resources provides an extremely clean and abundant energy source.
Hydrogen can be derived from compounds containing no carbon, such as ammonia (NH3) or borohydrides (BH4-).
In the lab, researchers are examining novel hydrogen generation methods using enzymes, algae and cyanobacteria.
Doesn't it take engergy to create Hydrogen?
Extracting any fuel takes energy – even getting gasoline from well to pump has a cost penalty equivalent of 20 percent of the energy content of gasoline. It does take more energy to generate hydrogen than gasoline, but looking at the whole picture is important. “Well-to-wheels” or “well-to-tank” analyses examine not only the energy cost, but also the environmental impacts from the entire pathway of producing, storing, distributing and utilizing different vehicle fuels.
An Argonne National Laboratory well-to-wheels analysis, for example, reports that most, but not all, fuel cell vehicle/fuel combinations achieve significant energy and greenhouse gas emission benefits over gasoline and alternatively-fueled vehicles.
A 2010 U.S. Department of Energy well-to-wheels analysis comparing internal combustion, battery and fuel cell vehicles found that fuel cell-electric vehicles are one of the lowest users of petroleum energy and emit significantly less levels greenhouse gases than most other vehicle technologies.
Why should governement support Fuel Cell development?
Fuel cells can provide major environmental, energy and economic benefits that advance critical national goals. Development and optimization of energy technologies has always been a partnership between government and the private sector.
Hydrogen and fuel cell technologies have historically received less government support compared to other energy technologies. Tax credits for natural gas drilling, military support for gas turbine technology, support for solar power research, nuclear power research and coal cleanup technologies total in the hundred billions of dollars over the past few decades.
What are other countries doing to support Hydrogen and Fuel Cell Technology?
The U.S. faces fierce competition from other countries for leadership in fuel cell technology.
Japan, Korea, Germany, and the United Kingdom are aggressively promoting fuel cell development with tax credits, low-interest loans, grants, and demonstration programs to support early purchases and drive down costs.
Additionally, these governments have been vocal in their support for fuel cell technologies, giving additional support to emerging fuel cell companies. The U.S. should pay close attention as other countries move aggressively towards a hydrogen and fuel cell future.
Why do we need a Hydrogen Economy?
The United States – indeed, the world – has a fundamental strategic interest in pursuing the hydrogen economy.
Our nation’s reliance on fossil fuels presents fundamental challenges to our economic security, our energy security, our homeland security, and our environment. Hydrogen can be produced renewably and locally, giving communities a fuel flexible and secure energy source. Our current over-reliance on fossil fuels is untenable. Hydrogen and fuel cells must be an important part of our energy portfolio moving into the future.
Source: hfcarchive.org