By Chris Burroughs
A Sandia research team is avoiding the use of greenhouse gas-producing fossil fuels to create hydrogen by turning to the sun.
The team, led by Doug Ruby (6218), is working with Teledyne Energy Systems, Inc., of Hunt Valley, Md., to improve the electrolysis process that separates hydrogen atoms from water to produce pure hydrogen gas. In a nonpolluting approach, photovoltaics — a method that uses solid-state solar cells to convert sunshine to electricity — would be the power source.
Teledyne is a company that has manufactured commercial electrolyzers for more than 30 years.
The goal of the research is for the hydrogen produced from electrolysis to be the fuel in hydrogen-powered cars of the future without generating greenhouse gases in its production or use.
"There are a lot of problems to be solved before a hydrogen-fueled car can become a reality," Doug says. "One is development of a cost-effective, sustainable, and nonpolluting way to make hydrogen."
Electrolysis involves passing water between two electrodes, one positive and one negative. A DC voltage is applied across a cell separator (membrane). Hydrogen collects at the cathode and oxygen at the anode, which are kept separated by the membrane. The hydrogen is captured and then stored in a tank. The oxygen could be vented or sold for various uses.
Today the most common way to make hydrogen is by using natural gas (methane). When it is heated and reacted with water (reformed), natural gas breaks down into hydrogen, which is stored, and carbon dioxide, a greenhouse gas that is released into the air.
"Electrolysis of water would be a far more preferable way to produce hydrogen than by reforming of methane," Doug says. "It avoids the use of the increasingly costly and limited supplies of natural gas. If the electricity for electrolysis is produced from renewable, hydropower, or nuclear sources, there are no greenhouse gases generated during production of hydrogen. This is a sustainable, nonpolluting cycle. Electrolysis produces hydrogen from water, and the hydrogen recombines with oxygen in air to create water and power in a fuel cell, which then powers our electric cars in the future."
The joint Sandia/Teledyne research will have three aspects: cell separator development, discovery of improved electrocatalysts and application methods, and design of optimized photovoltaics interface electronics. The improved electrolysis process will then be optimized using an economic/energy optimization model.
"The cell separator is a critical component in the electrolysis cell stack," says Donald Pile (2521), who is leading the cell separator development effort. "The objective here is to conduct research to design, develop, and fabricate an alternative cell separator material for electrolysis cells."
The separator is positioned between the two electrodes and prevents the remixing of hydrogen and oxygen products released after the DC voltage is applied to water. The problem with separators is that as the current increases, the efficiency of the separators decreases. A membrane made of a more ionically conductive material will minimize this issue.
Doug Wall and Bill Steen (both 1832) will be working on development of improved electrocatalysts. Teledyne has been using a proprietary catalyst for the cathode in its electrolysis process for many years.
"Although this catalyst is very effective in reducing cell voltage and improving efficiency, we believe the application of combinatorial electrochemical screening techniques will lead to identifying even better materials," Doug Wall says. "Furthermore, the same techniques can be used to evaluate anode materials, operating conditions, and duty cycles, generating an inclusive data set for identifying the optimum system conditions."
Over the next three years, he will work with Teledyne to build an electrochemistry toolset composed of automated, sequential evaluation techniques and truly parallel array-based screening methods. These will enable high-throughput evaluation of hundreds or thousands of material variations. These capabilities will be ideally suited for identifying catalysts but can also be used to pursue electrochemical-based sensor technologies.
In the meantime, Doug Ruby will take on the tasks of optimizing the photovoltaic interface electronics to maximize the overall system energy efficiency. And he will use extensive computer modeling to vary other parameters of the electrolysis process to reach the lowest overall hydrogen production cost.
It will be Teledyne's role to construct prototype electrolysis systems incorporating Sandia's research findings.
Electrolysis prototypes will then be evaluated at Sandia's photovoltaic test facilities.
Although the research is in its early stages, some people say it holds great promise for producing hydrogen for future hydrogen-fueled cars, which could reduce pollution and reduce our reliance on imported oil for making transportation fuel.
Hydrogen fueling stations
The vision, Doug Ruby says, is that there would be hydrogen fueling stations throughout the country, just as there are gas stations today. A hydrogen fueling station would consist of large electrolysis units, some powered by photovoltaics. Each unit could be sized to provide enough fuel for 100 cars.
"As the cost of natural gas keeps increasing, and if efficiency of electrolysis continues to improve, in the not-too-distant future, electrolysis-produced hydrogen could become available at the same cost as hydrogen produced from natural gas, which is the lowest cost source today," he says.
"If we are successful, and similar problems in developing cost-effective hydrogen storage and fuel cells are solved, we anticipate that hydrogen can be produced at a cost equivalent to $1 per gallon of gasoline on a cost-per-mile-driven basis. We believe it's a realistic goal, and we are eager to get started." — Chris Burroughs
By Mike Janes
General Motors Corp. and Sandia have launched a partnership to design and test an advanced method for storing hydrogen based on metal hydrides.
Metal hydrides — formed when metal alloys are combined with hydrogen — can absorb and store hydrogen within their structures. When subjected to heat, the hydrides release their hydrogen. In a fuel cell system, the hydrogen can then be combined with oxygen to produce electricity.
GM, the world's largest vehicle manufacturer, and Sandia have embarked on a four-year, $10 million program to develop and test tanks that store hydrogen in a complex hydride, sodium aluminum hydride — or sodium alanate for short. The goal is to develop a pre-prototype solid-state hydrogen storage tank that would store more hydrogen onboard a fuel cell vehicle than current conventional hydrogen storage methods. Researchers also hope to create a tank design that could be adaptable to any type of solid-state hydrogen storage.
"Hydrides have shown significant early promise to one day increase the range of fuel cell vehicles," says Jim Spearot, director of GM's Advanced Hydrogen Storage Program. "We know a lot of research still needs to be done, both on the types of hydrides we use, as well as the tanks we store them in. We think our work on projects like this with Sandia will get us another step closer to our goal."
GM and Sandia say the program is part of a concerted effort to find a way to store enough hydrogen onboard a fuel cell vehicle to equal the driving range obtained from a tank of gas, which will be key to customer acceptance of fuel cell vehicles.
The current leading methods of storage are liquid and compressed gas. However, to date, neither of these technologies has been able to provide the needed range and running time for fuel cell vehicles.
"We are designing a hydrogen storage system with challenging thermal management requirements and limits on volume and weight," says Chris Moen, manager of Sandia's Engineering and Science Technologies Dept. 8775. "Our staff researchers are excited to apply their unique, science-based design and analysis capabilities to engineer a viable solution."
"This is the kind of public-private research partnership that will help us realize the president's vision, communicated in his 2003 State of the Union Address, that ‘the first car driven by a child born today can be powered by hydrogen, and pollution-free,'" said Spencer Abraham, DOE secretary at the time of the announcement. "Over the long term, because of the president's visionary leadership, clean, efficient hydrogen fuel technologies like this will help make our nation far less reliant on foreign sources of energy."
In 2003, President Bush announced the Hydrogen Fuel Initiative with $1.2 billion over five years (FY 2004-FY 2008) to accelerate hydrogen research. Sandia's research activities in hydrogen storage support the president's long-term vision for commercially viable hydrogen-powered vehicles to reverse America's growing dependence on foreign oil.
The GM/Sandia project, privately funded and separate from the president's initiative, will be conducted in two phases. In Phase One, the program will study engineering designs for a sodium alanate storage tank. Researchers will analyze these designs using thermal and mechanical modeling, develop control systems for hydrogen transfer and storage, and develop designs for external heat management. GM and Sandia scientists will also be testing various shapes — from cylindrical to semi-conformable — to see which are the most promising.
In Phase Two, researchers will subject promising tank designs to rigorous safety testing and ultimately fabricate pre-prototype sodium alanate hydrogen storage tanks based on knowledge gained from the program's first phase.
Here's a possible scenario for filling up with a solid-state storage solution such as sodium alanate: The alanate would come preloaded in the tank, where it would remain, giving up its hydrogen and becoming a mixture of sodium hydride and aluminum. The customer would fill up using gaseous hydrogen. During filling, the mixture of aluminum and sodium hydride would absorb the hydrogen and turn it back into alanate, which would be ready to yield hydrogen when needed by the fuel cell. Once the tank is filled, the hydrogen would be stored at low pressure.
While it has shown good potential, hydride-based hydrogen storage also has some hurdles to clear. One current drawback is that most complex metal hydrides, such as sodium alanate, still operate at too high a temperature, which causes an inefficiency that forces some of the hydrogen to be used up in order to release the remaining hydrogen. Another challenge is reducing the time it takes to reabsorb hydrogen. It currently takes at least 30 minutes to recharge.
In separate, independent projects outside of this collaboration, both GM and Sandia are working to identify alloys that will store greater amounts of hydrogen that can be released at lower temperatures. Reducing filling and recharging times is another key area of research.
The research conducted through the GM/Sandia partnership is independent from that of Sandia's participation in the Metal Hydride Center of Excellence (see "Center of Excellence complements CRADA effort" below). The Center of Excellence, to be funded this year through a DOE "Grand Challenge," aims to develop a new class of materials capable of storing hydrogen safely and economically. -- Mike Janes
By Michael Padilla
Two members of a team that helped determine the cause of the space shuttle Columbia accident (Lab News, Sept. 5, 2003) are now helping NASA with its return-to-flight mission.
David Crawford (9116) and Ken Gwinn (9126) have been analyzing tests conducted on sensors that will be placed on the orbiter's wing-leading edges.
The project is to develop impact models for NASA's Impact Penetration Sensing system (IPSS) Wing Model. The model is being developed at Boeing to predict the accelerometer data to be collected during ascent and micrometeoroid/orbiting debris (MMOD) impacts on shuttle wing and spar leading-edge materials.
The project comes nearly two years after the shuttle fleet was grounded due to the space shuttle Columbia accident in February 2003. NASA has been working toward the final processing of hardware for the STS-114 Return to Flight mission. The space shuttle Discovery is scheduled to launch in early May.
The sensors developed by NASA are significant to the return-to-flight effort. The addition of the sensors to the leading edge meets one of the prime objectives identified by the Columbia Accident Investigation Board.
"If significant damage to the leading edge has occurred, the sensors will send a signal back to the command center and the request for an inspection can be made," says Ken.
David and Ken are evaluating test data and are comparing it with structural models of the shuttle and assessing what the signal levels mean.
Sandia's tasks include defining the forcing functions for foam, pieces of ice (from takeoff), ablator particles, and micrometeorites.
The tests evaluate different sizes of possible debris in the range of 20 cubic inches (the Columbia debris foam impactor was in the range of 2,000 cubic inches). All debris is studied by determining the velocity and angle of the impact.
"Lots of stuff can hit the shuttle," Ken says. "Liquid hydrogen and liquid oxygen develop frost prior to launch."
Ken says background noise from aero and acoustic loads also affects the sensors. "It is our job to discriminate significant impacts from the normal loadings of the shuttle," he says.
Full-scale tests of foam, ice, ablator, metal particle, and MMOD impacts are being performed at Southwest Research Institute (SwRI) in San Antonio, Texas. Tests on fiberglass and RCC (reinforced carbon composite) wing panels are being conducted at the White Sands Test Facility (WSTF).
The forcing functions will be individually and directly validated where possible against SWRI and WSTF test data. Integrated validation of the forcing function and IPSS Wing Model will be performed in collaboration with the effort of Boeing.
"We worked with the SWRI, WSTF, and NASA engineers to design tests to validate the impact models," Ken says. "This includes various velocity ranges, various impactors, and many locations on the panels to capture as many impact scenarios as possible. We also coordinated with the test engineers to place instruments where they'll be most effective for both analysis correlation and sensor demonstration."
Ken is analyzing the impact on the front of the wing, then providing impulse definitions to another team that determines how that impact affects the shuttle's structure and the response at the sensor box.
David analyzes the in-orbit data. He helps coordinate an experimental program at WSTF having to do with measuring and understanding the signals expected to be seen on the IPSS sensors from the impact of micrometeoroids or orbiting debris on the RCC leading-edge materials.
David primarily runs the shock physics code, CTH. He has been in daily contact with the experimenters at White Sands. His role is to develop a theoretical model of these signals to apply to the system model that Boeing is putting together.
He also provides a theoretical model for ice impacts and writes software that will distill all of the understanding of the various impactors —ice, foam, ablator, orbital debris— and provides it to the Boeing system model.
David says the general finding is that the signals expected to occur from damaging orbital impacts are large enough to be detectable with the sensor system.
"The IPSS project generally is very important as it is considered a crucial aspect of the space shuttle return to flight. Everything I've seen suggests that the IPSS should function as required."
Further analysis will extend forcing functions beyond the level that is accessible to tests being conducted at WSTF and SwRI. Every effort will be made to give Boeing the ability to construct new forcing functions as may be required for future missions — Michael Padilla