Discovery of Fuel Cells

DHS Summer Training - 2011

University of Baltimore

Mrs. Ipsita Ghosh

Ms. Alicia Sartorio

Trends in the use of fuel

Wood Coal O il NaturalGas

Hydrogen

Percentage of hydrogen content in fuel

It is interesting to note that as fuel use has developed through time the percentage of hydrogen content in the fuel has increased. It seems a natural progression that the fuel of the future will be hydrogen.

The two principal reactions in the burning of a hydrocarbon fuel are the formation of water and the formation of water becomes more significant, resulting in proportionality lower emissions of carbon dioxide.

A wide range of people, from energy companies through to automobile manufacturers are working to develop fuel cells and the accompanying infrastructure. A trend in the production of power is clearly visible:

The 19th century was the century of the steam engine,

The 20th century was the century of the internal combustion engine,

The 21st century will be the century of the fuel cell.

19th century: steam engine

20th century: internal combustion engine

21st century: fuel cells

What is a fuel cell? A fuel cell is a device that generates electricity by a chemical reaction. Every fuel cell has two electrodes, one positive and one negative, called, respectively the anode and the cathode. The reactions that produce electricity takes place at the electrodes. Every fuel cell has an electrolyte, which carries electrically charge particles from one electrode to the other, and a catalyst, which speeds the reactions at the electrodes.

A block diagram of a fuel cell

A fuel cell is an electrochemical cell that converts chemical energy from a fuel into electric energy.

Electricity is generated from the reaction between a fuel supply and oxidizing agent. The reactants flow into the cell, and the reaction products flow out of it, while the electrolyte remains within it.

Fuels can operate continuously as long as the necessary reactant and oxidant flows are maintained.

The most important design features in a fuel cell are: The electrolyte substance. The electrolyte substance usually

defines the type of a fuel cell. The fuel that is used. The most common fuel is hydrogen. The anode catalyst, which break down the fuel into electrons and

ions. The anode catalyst is usually made up of very fine platinum powder.

The cathode catalyst, which turns the ions into the waste chemicals like water or carbon dioxide. The cathode catalyst is often made up of nickel.

The Science of Fuel Cells

Phosphoric Acid

(PAFC)

Alkaline(AFC)

Polymer Electrolyte Membrane

(PEMFC)

Direct Methanol

(DMFC)

Solid Oxide

(SOFC)

Molten Carbonate(MCFC)

Types of Fuel Cells

Polymer Electrolyte Membrane(PEMFC)

Direct Methanol(DMFC)

Solid Oxide(SOFC)

Different types of fuel cells Alkali fuel cells operate on compressed

hydrogen and oxygen. They generally use a solution of potassium hydroxide (chemically KOH) in water as their electrolyte. Efficiency is about 70%, and operating temperature is 150 to 200 degrees C, (about 300 to 400 degrees F). Alkali cells were used in Apollo spacecraft to provide both electricity and drinking water.

Drawing of an Alkali Cell

Molten Carbonate fuel cells (MCFC) use high temperature compounds of salt ( like sodium or magnesium) carbonates (chemically, CO3) as the electrolyte. Efficiency ranges from 60 to 80 percent, and operating temperature is about 650 degrees C (1,200 degrees F). The high temperature limits damage from carbon monoxide “poisoning” of the cell and waste heat can be recycled to make additional electricity. Their nickel electrode-catalysts are inexpensive compared to the platinum used in other cells. But the high temperature also limits the materials and used of MCFC’s- they would probably be too hot for home use.

Drawing of a molten carbonate cell

Phosphoric Acid fuel cells (PAFC) use phosphoric acid as the electrolyte. Efficiency ranges from 40 to 80 percent, and operating temperature is between 150 to 200 degrees C (about 300 to 400 degrees F) Existing phosphoric acid cells have outputs up to 200kW, and 11MW units have been tested. PAFCs tolerate a carbon monoxide concentration of about 1.5 percent, which broadens the choice of fuels they can use. If gasoline is used, the sulfur must be removed. Platinum electrode-catalyst are needed, and internal parts must be able to withstand the corrosive acid.

Drawing of how both phosphoric acid and PEM fuel cells operate.

Proton Exchange Membrane fuel cells work with polymer electrolyte in the form of a thin, permeable sheet. Efficiency is about 40 to 50 percent, and operating temperature is about 80 degrees C ( about 175 degrees F). Cells outputs generally range from 50 to 250 kW. The solid, flexible electrolyte will not leak or crack, and these cells operate at a low enough temperature to make them suitable for homes and cars.

PEM Fuel Cell Electrochemical Reactions

Anode:

H2 2H+ + 2e- (oxidation)

Cathode:

1/2 O2 + 2e- + 2H+ H2O (l) (reduction)

Overall Reaction:

H2 + 1/2 02 H2O (l)

ΔH = - 285.8 kJ/mole

Thermodynamics of PEM Fuel Cells

Change in enthalpy (ΔH) = - 285,800 J/mole

Gibb’s free energy (ΔG) = ΔH - TΔS

ΔG at 25° C: = - 285,800 J - (298K)(-163.2J/K)

= - 237,200 J

Ideal cell voltage (Δ E) = - ΔG/(nF)

ΔE at 25º C = - [-237,200 J/((2)(96,487 J/V))]

= 1.23 V

ΔG at operating temperature (80º C):= - 285,800 J - (353K)(163.2 J/K)

= - 228,200 J

ΔE at 80º C = - [-228,200 J/((2)(96,487 J/V))]

= 1.18 V

Solid Oxide fuel cells (SOFC) use a hard, ceramic compound of metal ( like calcium or zirconium) oxides (chemically, O2) as electrolyte. Efficiency is about 60 percent, and operating temperatures are about 1000 degrees C (about 1800 degrees F). Cells output is up to 100kW. At such high temperatures a reformer is not required to extract hydrogen from the fuel, and waste heat can be recycled to make additional electricity. However, the high temperature limits applications of SOFC units and they tend to be rather large. While solid electrolytes cannot leak, they can crack.

Drawing of a solid oxide cell

The sixth type of fuel cell is the direct methanol fuel cell (DMFC). It is also a low temperature fuel cell, but can use methanol as a fuel directly without the need reforming. The primary limitation to the direct methanol fuel cell is that the rate of reaction on the anode is very slow, this results in a very low operating voltage output. However for certain application, such as portable power, the direct methanol fuel cell may be ideal.

Advantages and Disadvantages of Fuel Cell Advantages• Fuel cells eliminate pollution caused by burning

fossil fuels; the only by-product is water.• If the hydrogen used comes from the electrolysis of

water, then using fuel cells eliminates greenhouse gases.

• Fuel cells do not need conventional fuels such as oil or gas and can therefore eliminate economic dependence on politically unstable countries.

• Since hydrogen can be produced anywhere where there is water and electricity, production of potential fuel can be distributed.

• Installation of smaller stationary fuel cells leads to a more stabilized and decentralized power grid.

• Fuel cells have a higher efficiency than diesel or gas engines.

• Most fuel cells operate silently, compared to internal combustion engines.

• Low temperature fuel cells (PEM, DMFC) have low heat transmission which makes them ideal for military applications.

Disadvantages• Fuel cells eliminate pollution caused by burning

fossil fuels; the only by-product is water.• If the hydrogen used comes from the electrolysis of

water then using fuel cells eliminates greenhouse gases.

• The refueling and the starting time of fuel cells vehicle are longer and the driving range is shorter than in a “normal” car.

• Fuel cells are in general slightly bigger than comparable batteries or engines. However, the size of the units is decreasing.

• Fuel cells are currently expensive to produce, since most units are hand-made.

• Some fuel cells use expensive materials. • The technology is not yet fully developed and few

products are available.

History of Fuel Cell The principle of the fuel cell was discovered by

German Scientist Christian Friedrich Schonbein in 1838 and published in one of the scientific magazines of the time.

The first fuel cell was demonstrated by Welsh scientist and barrister Sir William Robert Grove in the February 1839 edition of the Philosophical Magazine and Journal Science and later sketched, in 1842, in the same journal. The fuel cell he made used similar materials to today’s phosphoric-acid fuel cell. However, Grove’s fuel cell was not practical, due to problems of corrosion and instability of the materials. As a result there was little research and development into fuel cells for many years to follow.

The History

Electrolyser Grove’s Gas Battery(first fuel cell, 1839)(after Larminie and Dicks, 2000)

In 1955, W. Thomas Grubb, a chemist working for the General Electric Company (GE), further modified the original fuel cell design by using a sulphonated polystyrine ion-exchange membrane as the electrolyte.

Three years later another GE chemist, Leonard Niedrach, device a way of depositing platinum onto the membrane, which served as catalyst for the necessary hydrogen oxidation and oxygen reduction reactions. This became known as the “Grubb-Niedrach fuel cell”. GE went on to develop this technology with NASA and McDonnell Aircraft, leading to its use during Project Gemini. This was the first commercial use of a fuel cell.

Bacon’s laboratory in 1955

Photo courtesy of University of Cambridge

In 1959, a British engineer Francis Thomas Bacon successfully developed a 5kW stationary fuel cell.

Later on that same year, Bacon and his colleagues demonstrated a practical a five-kilowatt unit capable of powering a welding machine.

In 1959, a team led by Harry Ihrig built a 15kW fuel cell tractor for Allis-Chalmers which was demonstrated across the US at state fairs. This system used potassium hydroxide as the electrolyte and the compressed hydrogen and oxygen as the reactants.

In the 1960s, Pratt and Whitney licensed Bacon’s U.S. patents for use in the U.S. space program to supply electricity and drinking water (hydrogen and oxygen being readily available from the spacecrafts tanks).

In 1991, the first hydrogen fuel cell automobile was developed by Roger Billings .

NASA Space Shuttle fuel cell

United Technologies Corporation’s UTC Power subsidiary was the first company to manufacture and commercialize a large, stationary fuel cell system for use as a co-generation power plant in hospitals, universities and large office buildings. UTC Power continues to be the sole supplier of fuel cells to NASA for use in space vehicles, having supplied the Apollo missions, and currently the Space Shuttle program, and is developing fuel cells for automobiles, buses, and cell phone towers; the company has demonstrated the first fuel cell capable of starting under freezing conditions with its proton exchange membrane.

Distributed power stations

Photo courtesy of Ballard Power Systems

250 kW distributed cogeneration power plant

Applications for Fuel Cells

Shown in the picture is a prototype fuel cell distributed power plant, recently developed by Ballard Power. This particular unit was commissioned for the BC Hydro grid. It provides 250 kilowatts of electricity and about the same amount of heat, fuelled from natural gas. This is enough power to provide heat and electricity to a community of about 50 homes for example, or to a hospital or to a remote location school. Ballard plans to introduced it’s first commercial fuel cell distributed power plant as a backup power supply in 2003.

Applications for Fuel Cells

Transportation vehicles

Photo courtesy of DaimlerChrysler

NECAR 5

The California Low Emission Vehicle Program, a program of the California Air Resources Board (CARB) has been a large incentive for automakers to develop fuel cell automobiles.

The NECAR 5, shown here is a prototype automobile is Daimler Chrysler. This automobile is fuelled with liquid methanol and has a top speed of over 90 miles/hour (150km/hr). In forthcoming years there are plans for buses, trucks, and trains all powered with fuel cell engines. Thirty buses will be commercially introduced in ten European cities beginning in 2002.

Home power

Photo courtesy of Plug Power

7 kW home cogeneration power plant

Applications for Fuel Cells

Fuel cell power plants are also being developed by several manufacturers to provide electricity and heat to a single family home. Fuelled by either natural gas or propane these fuel cell power plants will be able to power a home independent of a grid.

Plug power, based in Latham New York has developed a new fuel cell power plant that supplies 7 kilowatts of electricity and heat, using either natural gas or propane as the fuel. That is enough power to supply the electrical demand of a modern energy efficient home. Plug Power plans to commercially introduce this home power plant, distributed through General Electric, in 2002.

Portable power

50 W portable fuel cell with metal hydride storage

Applications for Fuel Cells

Several manufacturers are currently developing portable fuel cell power supplies. These power supplies can provide anything from a few watts up to several kilowatts of electricity. Portable fuel cell power supplies will by an alternative to conventional batteries for many applications. Applications includes laptops, mobile phones, remote road signs and lighting.

This particular fuel cell is a prototype 40 watt PEM fuel cell by Heliocentris, powering a remote blinking lamp. The fuel cell is contained in the upper part of the unit. The lower part of the unit contains metal hydride storage cylinder, containing the hydrogen.

Applications for Fuel CellTelecommunicationsWith the use of computers, the

Internet, and communication networks steadily increasing, there comes a need for more reliable power than is available on the current electrical grid, and fuel cells have proven to be up to 99.999% (five nines reliable). Fuel cells can replace batteries to provide power for 1kW to 5kW telecom sites without noise or emissions, and are durable, providing power in sites that are either hard to access or are subject to inclement weather.

Landfills/ Wastewater Treatment Plants/ Breweries/ Wineries Fuel cells currently operate

at landfills and wastewater treatment plant across the country, proving themselves as a valid technology for reducing emissions and generating power from the methane gas they produce. They are also installed at several breweries and a winery- Sierra Nevada, Kirin, Asahi and Sapporo and Napa Wine Company.

Applications of Fuel CellTransportation Cars- All the major

automotive manufacturers have a fuel cell vehicle either in development or in testing right now, and several have begun leasing and testing in larger quantities.

Transportation

Buses- Over the last four years, more than 50 fuel cell buses have been demonstrated in North and South America, Europe, Asia and Australia. Fuel cells are highly efficient, so even if the hydrogen is produced from fossil fuels, fuel cell buses can reduce transit agencies’ CO2 emissions. And emissions are truly zero if the hydrogen is produced from renewable electricity, which improves local air quality. Fuel cell buses reduce noise pollution as well.

Transportation

Scooters- In spite of their small size, many scooters are pollution powerhouses. Gas-powered scooters, especially those with two-stroke engines, produce tailpipe emissions at a rate disproportionate to their small size. These two stroke scooters produce almost as much particulate matter and significantly more hydrocarbons and carbon monoxide as a heavy diesel truck. Fuel cell scooters running on hydrogen will eliminate emissions.

Transportation

Trains- Fuel cell s are being developed for mining locomotives since they produced no emissions. An international consortium is developing the world’s largest fuel cell vehicle, a 109 metric-ton, 1MW locomotive for military and commercial railway applications.

Transportation

Planes- Fuel cells are an attractive option for aviation since they produce zero or low emissions and make barely any noise. The military is especially interested in this application because of low noise, low thermal signature and ability to attain high altitude. Companies like Boeing are heavily involved in developing a fuel cell plane.

Transportation

Boats- For each liter of fuel consumed, the average outboard motor produces 140 times the hydrocarbons produced by the average modern car. Fuel cell engines have higher energy efficiencies than combustion engines, and therefore offer better range and significantly reduced emissions. Iceland has committed to converting its vast fishing fleet to use fuel cells to provide auxiliary power by 2015 and, eventually, to provide primary in its boats.

Portable Power

Fuel cells can provide power where no electric grid is available, plus they are quiet, so using one instead of a loud, polluting generator at a campsite would not only save emissions, but it won’t disturb nature, or your camping neighbors. Portable fuel cells are also being used in emergency backup power situations and military applications. They are much lighter than batteries and last a lot longer, especially important to soldiers carrying heavy equipment in the in the field.

Micro Power

Consumer Electronics- Fuel cells will change the telecommuting world, powering cellular phones, laptops and palm pilots hours longer than batteries. Companies have already demonstrated fuel cells that can power cell phones for 30 days without recharging and laptops for 20 hours. Other applications for micro fuel cells include pagers, video recorders, portable power tools and low power remote devices such as hearing aids smoke detectors, burglar alarms, hotel locks and meter readers. This miniature fuel cells generally run on methanol, an inexpensive wood alcohol also used in windshield wiper fluid.

Renewable Energy Sources

As long as the sun shines, the wind blows or the rivers flow there can be clean, safe and sustainable electrical power, where and

when required, with a solar hydrogen energy system

M icro hydro

Storage

H 2

Oxygen

Oxygen

WaterWater

FuelCellE lectro lyzer

Solar Cell

W ind

Heliocentris: Science education through fuel cells 54

A

Our Fragile Planet.

We have the responsibility to mind the planet, so that the extraordinary natural beauty of the Earth

is preserved for generations to come.

Photo courtesy of NASA