Proton Exchange Membrane (PEM) Fuel Cells Portal Page

Proton exchange Membrane (PEM) fuel cells, also known as Polymer exchange membrane fuel cells typically operate on pure (99.999%) hydrogen fuel. The PEM fuel cell combines the hydrogen fuel with the oxygen from the atmosphere to produce Water, heat (up to 90°C) and electricity.

How it Works

PEM Fuel cells typically utilise platinum basedcatalysts on the Anode to split the Hydrogen into positive ions (protons) and negative electrons. The ions pass through the membrane to the cathode to combine with oxygen to produce water. The electrons must pass round an external circuit creating a current to rejoin the H2 ion on the cathode. Chemical Equation:

Anode: 2H₂ »» 4H⁺ + 4e^-
Cathode: O₂ + 4H⁺ + 4e^- »» 2H₂O

Each cell produces approximately 1.1 volts, so to reach the required voltage the cells are combined to produce stacks. Each cell is divided with bipolar plateswhich while separating them provide a hydrogen fuel distribution channel, as well as a method of extracting the current.

PEM fuel cells are considered to have the highest energy density of all the fuel cells, and due to the nature of the reaction have the quickest start up time (less than 1 sec) so they have been favoured for applications such as vehicles, portable power and backup power applications.

The intolerance of the catalysts to impurities such as carbon monoxide has led to developments of high temperature membranes which operate at 150°C +. This enables the catalysts to tolerate greater impurities in the hydrogen supply.

Image source - http://www.eere.energy.gov/hydrogenandfuelcells/fuelcells/fc_types.html

Courtesy: SGL Carbon

Fuente:http://www.fuelcellmarkets.com/fuel_cell_markets/proton_exchange_membrane_fuel_cells_pemfc/4,1,1,2502.html 

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PEM Fuel Cells 

Technology

History

Applications

The essay below outlines the technology and history of proton exchange membrane, or PEM, fuel cells. If you have artifacts, photos, documents, or other materials that would help to improve our understanding of these devices be sure to respond to the questionnaire: 

Collecting Fuel Cell History

PEM Fuel Cell Technology

Proton exchange membrane (PEM) fuel cells work with a polymer electrolyte in the form of a thin, permeable sheet. This membrane is small and light, and it works at low temperatures (about 80 degrees C, or about 175 degrees F). Other electrolytes require temperatures as high as 1,000 degrees C.

GE's Russell Hodgdon shows a polymer electrolyte in 1965

To speed the reaction a platinum catalyst is used on both sides of the membrane. Hydrogen atoms are stripped of their electrons, or "ionized," at the anode, and the positively charged protons diffuse through one side of the porous membrane and migrate toward the cathode. The electrons pass from the anode to the cathode through an exterior circuit and provide electric power along the way. At the cathode, the electrons, hydrogen protons and oxygen from the air combine to form water. For this fuel cell to work, the proton exchange membrane electrolyte must allow hydrogen protons to pass through but prohibit the passage of electrons and heavier gases.

Efficiency for a PEM cell reaches about 40 to 50 percent. An external reformer is required to convert fuels such as methanol or gasoline to hydrogen. Currently, demonstration units of 50 kilowatt (kw) capacity are operating and units producing up to 250 kw are under development.

PEM Fuel Cell History

PEM technology was invented at General Electric in the early 1960s, through the work of Thomas Grubb and Leonard Niedrach. GE announced an initial success in mid-1960 when the company developed a small fuel cell for a program with the U.S. Navy's Bureau of Ships (Electronics Division) and the U.S. Army Signal Corps. The unit was fueled by hydrogen generated by mixing water and lithium hydride. This fuel mixture was contained in disposable canisters that could be easily supplied to personnel in the field. The cell was compact and portable, but its platinum catalysts were expensive.

Thomas Grubb and Leonard Niedrach of General Electric (Schenectady) run a fan with a small diesel powered PEM fuel cell in April 1963

PEM technology served as part of NASA's Project Gemini in the early days of the U.S. piloted space program. Batteries had provided spacecraft power in earlier Project Mercury missions, but the lunar flights envisioned for Project Apollo required a longer duration power source. Gemini's main objective was to test equipment and procedures for Apollo, and missions lasting up to 14 days included operational tests of fuel cells. GE's PEM cells were selected, but the model PB2 cell encountered repeated technical difficulties, including internal cell contamination and leakage of oxygen through the membrane. Geminis 1 through 4 flew with batteries instead.

GE redesigned their PEM cell, and the new model P3, despite malfunctions and poor performance on Gemini 5, served adequately for the remaining Gemini flights. Project Apollo mission planners, however, chose to use alkali fuel cells for both the command and lunar modules, as did designers of the Space Shuttle a decade later.

Technicians inspect a PEM fuel cell in the Gemini 7 spacecraft, 1965

GE continued working on PEM cells and in the mid-1970s developed PEM water electrolysis technology for undersea life support, leading to the US Navy Oxygen Generating Plant. The British Royal Navy adopted this technology in early 1980s for their submarine fleet. Other groups also began looking at PEM cells. In the late 1980s and early 1990s, Los Alamos National Lab and Texas A&M University experimented with ways to reduce the amount of platinum required for PEM cells.

Recently PEM developers added the weatherproofing material Gore-Tex to their cells to strengthen the electrolyte.

PEM Fuel Cell Applications

A Ballard fuel cell powers a laptop computer.

PEM cells may have a mixed record in space, but several companies have been testing the cells in more down-to-earth vehicles. In 1995, Ballard Systems tested PEM cells in buses in Vancouver and Chicago and later in experimental vehicles made by DaimlerChrysler. PEM cells have also supplied power to unmanned blimps called aerostats and to sonobuoys, which are nautical buoys that generate and receive sonar signals.

Early in 2000, AeroVironment selected PEM technology to provide nighttime power for its solar-powered Helios long-duration aircraft. The goal was to make an unpiloted aircraft that could fly continuously for up to six months by using photovoltaic panels during the day to run electric motors and electrolyze water. At night, the fuel cell was to run the motors by converting the hydrogen and oxygen back into water. Several test flights were made with and without a fuel cell from 2001 to 2003.

The Helios research aircraft takes to the air.

  Automotive research has taken on new urgency as air quality regulations grow steadily stricter, particularly in California. Energy Partners and the U. S. Department of Energy's Office of Advanced Automotive Technologies provided two 20 kw fuel cell stacks to Virginia Tech and Texas Tech universities to evaluate performance in hybrid electric cars. Major automakers like Ford and Volkswagen are also testing PEM vehicles.

Since the mid-1980s, PEM development has included stationary power applications. In 1989, Ballard Systems introduced a 5 kw hydrogen and air PEM stack. Two years later, GPU and Ballard began operating a 250 kw plant at Crane Naval Air Station in Indiana.

Avista Laboratory's 7.5KW PEM residential fuel cell power plant.

One of the more publicized demonstrations has been Plug Power's PEM unit in Albany, New York, which began powering a home in June 1998. Promoted by the company as the "first permanent home installation," the 5 kw power plant helped the company to make significant partnerships with both GE and Detroit Edison. These partners had hoped to market a residential fuel cell during 2002, however those plans have been postponed.

©2004 Smithsonian Institution
(Copyright Statement) 

Source: http://americanhistory.si.edu/fuelcells/pem/pemmain.htm
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• Video: How PEM Fuel Cells Work

http://www.youtube.com/watch?v=hvWX7rLryAs

http://www.youtube.com/watch?v=g2vZ9o_0WyA&feature=related

• Video: Hydrogen Fuel Co - Ballard explains PEM fuel cells

http://www.youtube.com/watch?v=08ZH7vwzzEg&feature=related

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