Sandia researchers seek new nonpolluting ways to produce hydrogen fuel from water and sunlight
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."