Calling for a Revolution

Old ways of generating electricity need to be improved.

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Breakthroughs are needed to make the generation of electricity more environmentally friendly. By Jerry Sorell

Nickel magazine, October 2002 -- The high-efficiency power plants envisioned for the near future are expected to release significantly less carbon dioxide, nitrogen oxides and sulphur dioxide into the atmosphere. However, this feat will require heat- and corrosion-resistant materials that do not exist today.

The advanced energy systems being pursued will have substantially higher thermal efficiencies compared to today's commercial plants. This translates into higher gas temperatures and a greater need for materials possessing the requisite strength, heat and corrosion resistance for long-term, reliable service at higher temperatures.

Such innovations are not restricted to the development of materials with better mechanical properties and corrosion resistance, however. Rather, they extend to innovations in design concepts, materials synthesis, fabrication methods, monitoring-control inspection techniques, and life assessment/prediction. There are a lot of things to consider to make power generation more environmentally friendly.

Major programs aimed at furthering these initiatives are ongoing in Europe, the U.S. and Japan, and were discussed at the Third International Workshop on Life Cycle Issues in Advanced Energy Systems, held in Woburn, U.K., in June 2002.

The total cost, shared by government and industry in the U.S., Europe and Japan, for ongoing materials-related research and testing in support of advanced energy systems totals several hundred million dollars annually.

The European Union (EU) has two multifaceted R&D efforts in progress -- the COST and THERMIE programs. The former is targeted at a 650 [degrees] C/300 bar (50% efficiency) USC steam cycle plant; the latter, at a 700 [degrees] C/375 bar (55% efficiency) plant. Key areas of concern are advanced materials for steam generators and turbines. Although the base-case fuel is coal, consideration will be given to biomass co-firing in order to minimize greenhouse gas emissions. Strength and corrosion considerations in advanced USC plants will require replacement of iron-based with nickel-based alloys for highest temperature components.

Another Europe-based program addressing materials needs is being conducted by the UK Advanced Power Generation Task Force, which is focusing on cleaner coal systems, gasification, fuel cells, and CO[subscript]2 capture technologies.

Materials R&D programs in the U.S., the cost of which are mostly shared by the U.S. Department of Energy (DOE) and the private sector, are slanted toward radically advanced energy technologies. The ambitious goals are enunciated in DOE's VISION 21 strategy for developing the technology basis for high-efficiency, ultra-clean, fuel-flexible, cost-effective energy systems by 2015.

Technologies include gasification, fluid bed combustion, externally fired cycles, hot gas cleanup, fuel cells and carbon sequestration. Materials systems under development embrace structural materials (for example, high-temperature alloys, ceramics and coatings for heat exchangers and gas turbines), as well as functional materials (such as ceramic membranes for gas separation and fuel cell components).

Materials R&D in Japan continues its heavy emphasis in support of high-efficiency USC power generation, exemplified by collaborative METI and NIMS projects for developing stronger ferritic steels. Other government-industry collaborations have succeeded in developing high-strength austenitic stainless steels for high-temperature power generation equipment. Under NEDO auspices, new austenitic steels, targeted specifically for high-efficiency waste-to-energy plants, are being evaluated. As in Europe and the U.S., Japan is performing materials R&D for fuel cells and other advanced energy systems, as well as testing materials for clean coal technology IGCC and PFBC applications.

Corrosion-related issues discussed at the workshop included materials performance in modern power plants and data from laboratory and pilot-plant tests. The prevalent corrosion modes experienced in high-temperature combustion-gasification environments, often in combination, are oxidation, sulfidation, chloridation, carburization and molten salt attack. Also encountered in some advanced energy system environments are nitridation and metal dusting attack. "Breakaway" corrosion was identified as a particularly troublesome manifestation of high-temperature oxidation-sulfidation, characterized by a sudden steep increase in attack after extended exposures. Models are being developed to predict the onset of breakaway.

The workshop was co-sponsored by the Electric Power Research Institute (EPRI), Oak Ridge National Laboratory (ORNL), Cranfield University's Power Generation Technology Centre, and the European Commission's JRC Institute for Energy. Invited participants were from 12 countries and included prominent materials-corrosion scientists and engineers, among them NiDI consultant Jerry Sorell.

Publication of the Workshop proceedings is targeted for early 2003 in a special edition of the international journal "Materials at High Temperatures."

Jerry Sorell is a consultant to the Nickel Development Institute based in North Caldwell, New Jersey, U.S.A.

The proceedings of the above-mentioned workshop will be published in early 2003 in "Materials at High Temperatures" published by: Science Review P.O. Box 314 St. Albans Hertfordshire, U.K. AL1 4ZG E-mail: scilet@scilet.com Web site: www.scilet.com/materials/scimat.htm

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