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[Saurabh Jain]

coal without combustion



Researchers want to put it into fuel cells instead of boilers, for cheaper, cleaner electricity.
by Scott Samuelsen and Amy Babthingy

the 19th century is seen as the age of coal, and with good reason. It was then that engineers first put coal to work on a large scale, first as fuel for steamboats and locomotives, and later in electrical power plants. Other energy sources were available—petroleum came on the market in the middle of the 19th century, and wood and water still had important roles—but burning coal was dominant.

So it may be a shock to realize that in 1839, as the coal-fired Industrial Revolution was in full swing, English scientist William Grove invented the first fuel cell. Grove used what was considered reverse electrolysis to generate electricity from hydrogen and oxygen. The efficiencies of the early fuel cells were low, and investigators were stumped as to how to make them more practical. With the advent of the internal combustion engine, interest in fuel cells fell away. They were curiosities, mostly, or relegated to specialized applications, such as powering manned spacecraft.

Now, many years later, scientists and engineers are working fervidly to make fuel cells a practical replacement for combustion. What's changed? For one, the cheap fuel that made the industrialization in the 19th and 20th centuries possible is becoming harder to find. And we've come to realize that how we use the fuel is an important consideration: Uncontrolled combustion can spew toxic metals or climate-changing gases into the atmosphere. Fuel cells can improve on combustion on both those fronts. Fuel cells are electrochemical, so they are not bound by the Carnot limit on efficiency, and they can be designed to capture any harmful metals or gases produced.

One of the most ambitious projects is the Solid State Energy Conversion Alliance, created by the U.S. Department of Energy to clear the technical hurdles that have kept fuel cells impractical. Launched in 2000, and managed by the National Energy Technology Laboratory and the Office of Fossil Energy in Pittsburgh, SECA is a collaboration among government, the private sector, and the scientific community to pursue a vision of cost-effective, near-zero-emission solid oxide fuel cell technology for commercial applications.

Already, the systems developed are making great advances. One small prototype system has exceeded benchmarks for efficiency, and has an estimated cost within a factor of two of existing commercial power stations.

And in what is an odd twist, the solid oxide fuel cells being developed are designed to run on gasified coal. The future of coal, in fact, may well be tied to a technology that it has overshadowed for nearly 170 years.

Compared to other government research programs, SECA has an unusual structure. The program unifies a number of organizations to work toward a common goal, yet retains a healthy spirit of competition to drive progress and spur innovation. Private sector businesses are grouped into industry teams with vested interests in developing solid oxide fuel cell systems as commercial products. All of these teams work to spin off early products achieving the targeted reductions in SOFC system costs and to establish the needed material and manufacturing infrastructure.

The SECA industry teams are supported by the core technology program, comprising leading universities, national laboratories, and businesses across the country. These groups are working on dozens of competitively selected SOFC projects to provide vital research and development solutions to the industry teams in five areas: materials, manufacturing, fuel processing, power electronics, and computer simulation. Research priorities are constantly evaluated and updated as new knowledge and technology advances are achieved. This shared R&D portfolio is intended to reduce redundancy and the cost to the federal government by making results available to all industry teams through special intellectual property provisions that enhance technology transfer. As a result, the SECA industry teams—potential competitors in the marketplace—benefit mutually from the collective ingenuity of the core technology program to pursue innovations independently in fuel cell design.

The United States' Office of Management and Budget recently cited the SECA program as a leader in government-industry partnerships, noting that its structure "has generated a high level of competition between the [industry teams] and an impressive array of technical approaches. The SECA program also develops certain core technologies that can be used by all the industry teams to avoid duplication of effort."


Clean, Quiet, and Consistent

There are, of course, many fuel cells in use today, so why do we need such a large-scale program? The fuel cells on the market have many advantageous qualities, to be sure: They are exceedingly clean, relatively quiet, and can operate for long periods without maintenance and oversight. But compared to standard combustion generating equipment, commonly used fuel cells—which use molten electrolytes such as sodium bicarbonate or phosphoric acid—have a capital cost many times greater. And they have been largely limited to fuels such as natural gas or pure hydrogen. As a consequence, fuel cells have yet to break into mainstream power applications.

Research is reducing the gap between fuel cells and standard combustion generators, and one type of fuel cell promises to eliminate it altogether. Fuel cells made with a solid, porous ceramic electrolyte have the ability to use many types of fuels, and since they don't require precious metals or caustic chemicals, they have the potential to be made quite inexpensively. Solid oxide fuel cells are, in fact, a solid-state technology, with all the potential for reliability and compactness that the name implies.

What makes SECA groundbreaking is that it is working to develop a modular, low-cost, solid oxide fuel cell system specifically for use in a new kind of coal plant. To be sure, SECA fuel cells can also operate using natural gas, bio-fuels and diesel, and, of course, hydrogen. By developing fuel cells to operate efficiently and cost effectively on the fuels that dominate today's power industry, the hope is that the program can help meet pressing environmental and energy-security needs while building a bridge to a low-carbon economy. The SECA goal is to have SOFC power generation systems capable of mass production at $400 per kilowatt—a cost comparable to that of current stationary power systems—by 2010.

That ambitious vision is rapidly becoming a reality. Challenges to fuel cell technology remain, but they are being solved at an accelerated rate due to the intense focus of the alliance.

To tackle the perennial problem of the cost of fuel cells, SECA is blending established manufacturing processes developed in the semiconductor and electronics industry with state-of-the-art fuel cell technology and designs. The aim is that this will leverage the advantages of economies of production and scale in the coal plant of the future. What's more, SECA has set aggressive performance and cost targets for its private sector industry teams, driving them to new solutions to old problems. And by dividing the research and development into three phases, a comprehensive set of escalating benchmarks has been established for achieving breakthroughs in cost, reliability, and efficiency—the keys to commercial viability.


Ready for the Real Test
The results have been encouraging. The first round of system prototypes developed by several competing industry teams and manufactured with scalable mass-production techniques, has exceeded SECA's first set of escalating goals for efficiency, availability, and production cost. A typical system demonstrated an availability of 90 percent, and the small 3-10 kilowatt systems reached efficiencies in the 35-to-40 percent range—both marks surpassing SECA targets. Indeed, this level of efficiency in a small system demonstrates that much higher levels are achievable in larger systems. Most significantly, the independently audited system costs ranged from $691 to $784 per kilowatt—a big step toward achieving market-competitive costs. (These numbers represent aggregated results across six industry teams.)

These early developments are needed to ensure that established, mature, and cost-effective solid-oxide fuel cells are ready for the real test—demonstration in a coal plant. Three teams, in fact, are focused on delivering megawatt-scale systems. And another program within SECA seeks to leverage the program's success to date by ultimately extending the efficiency and environmental benefits of the technology to full-scale coal central power systems.

Nearly a quarter of the energy consumed in the United States comes from coal, and while domestic gas and oil supplies dwindle, the U.S. possesses a bonanza of coal. With 25 percent of the world's coal reserves, the United States is the Saudi Arabia of coal, and coal is a key part of the National Energy Policy put forth by the Bush administration a few years ago.

Such a large and secure energy resource will be of critical importance in the coming decades. But there is concern from many quarters about coal's viability as a fuel. It has been implicated in the increase in atmospheric carbon dioxide and in the rise in global temperatures that follow from that. In addition, harmful materials such as sulfur and mercury are found in the raw emissions from coal-fired power plants.

One increasingly popular solution to the environmental impact of coal energy is capturing carbon dioxide and other products of coal combustion before they are released. The captured carbon dioxide can then be held—sequestered—in geologic formations. SOFCs are one of the key technologies being developed with an eye toward enabling the sequestration of carbon dioxide during power production. The ultimate goal is that at least 90 percent of the CO2 produced generating electricity will one day be captured, and that this technology will let coal plants meet environmental and permit requirements throughout the United States.

Such a system would see an SOFC and its associated components scaled up to a size appropriate for a central generating station and integrated with coal gasification technology. SECA plans to have megawatt-scale, coal-based SOFC systems ready for deployment by 2012, perhaps as part of FutureGen, another public-private partnership. When it's operational, the prototype will be the cleanest fossil fuel-fired power plant in the world.

The fuel cell has come a long way since its inception nearly 170 years ago. SECA's recent successes demonstrate that it's only a matter of time before solid oxide fuel cell technology achieves its commercial potential. Indeed, it's possible that SOFCs could reach high enough standards of efficiency and economy to entirely replace conventional combustion as the primary means of generating electricity in the U.S.

The coal age would continue, only now it would be converted electrochemically into electricity. And the fuel cell would move from being William Grove's laboratory curiosity to the mainstay of the modern world.


Scott Samuelsen is the director of the National Fuel Cell Research Center at the University of California, Irvine. Amy Babthingy is president of STG2, a technical marketing firm, in Honeoye Falls, N.Y.