In response to a request from the Deputy Assistant Secretary for Coal and Power Systems, the National Research Council (NRC) formed the Committee on Research and Development (R&D) Opportunities for Advanced Fossil-Fueled Energy Complexes to review the goals of the Department of Energy's (DOE) Vision 21 Program (DOE's vision for the future of coal-based power generation) and to recommend systems and approaches for moving from concept to reality. Vision 21 is an ambitious, forward-looking program for improving technologies and reducing the environmental impacts of using fossil fuels (petroleum, natural gas, and coal) to produce electricity, process heat, transportation fuels, and chemicals. The general directions and goals of the Vision 21 Program are intended to ensure that fossil fuels can be used well into the twenty-first century.
The committee's review was based primarily on the Vision 21 Program Plan: Clean Energy Plants for the 21st Century published by DOE in April 1999 (DOE, 1999). The committee also invited speakers from government, industry, and academia to comment on the technical challenges and other issues facing the Vision 21 Program. The committee's principal findings and recommendations on the program as a whole, as well as on individual program components, are summarized below. Additional findings and recommendations appear in the body of this report.
GOALS OF THE VISION 21 PROGRAM
Vision 21 is described by DOE as a program for generating power efficiently and controlling pollution from a new class of fossil-fueled facilities capable of
TABLE ES-1 Goals of the Vision 21 Program
Overall thermal efficiency above 85 percent; also meets above efficiency goals for electricity.
Efficiency-Fuels Only Plant
When producing fuels, such as H2 or liquid transportation fuels alone from coal, 75 percent fuels utilization efficiency (LHV).
Near zero emissions of sulfur and nitrogen oxides, particulate matter, trace elements, and organic compounds; 40–50 percent reduction in CO2 emissions by efficiency improvement; 100 percent reduction with sequestration.
Aggressive targets for capital and operating costs and RAM;c products of Vision 21 plants must be cost-competitive with market clearing prices when they are commercially deployed.
Major benefits (e.g., improved gasifiers and combustors, gas separation membranes) begin by 2006 or earlier; designs for most Vision 21 subsystems and modules available by 2012; Vision 21 commercial plant designs available by 2015.
a HHV = higher heating value
b LHV = lower heating value
c RAM = reliability, availability, maintenance
Source: Adapted from DOE, 1999.
coproducing electric power, process heat, and high-value fuels and chemicals. The major goals of the program are shown in Table ES-1.
STRUCTURE OF THE VISION 21 PROGRAM
The overall goal of the Vision 21 Program is to develop flexible components and subsystems for modular-designed plants capable of using multiple feedstocks or producing multiple products. The program focuses on the elements that will be common to all of the facilities under consideration:
Enabling technologies, such as fuel-flexible gasification, fuel-flexible turbines, fuel cells, advanced-combustion and high-temperature heat exchangers, will be the building blocks of the subsystems and modules.
Supporting technologies, such as controls and sensors, new materials, advanced computational modeling, and virtual demonstrations, will be critical crosscutting technologies for many of the subsystems and components.
Systems integration will focus on innovative ways of combining high-performance subsystems into very clean, efficient, low-cost plants.
The goals of the Vision 21 Program include the demonstration of modules and/or designs of complete plants by 2015. For purposes of the committee's evaluation, the Vision 21 Program was divided into three areas:
supporting technologies and systems integration
Commercialization was considered separately because the committee believes the success of the program will depend on the successful transfer of the Vision 21 technologies to the marketplace. The following evaluation is based on the Vision 21 Program Plan provided by DOE.
ACHIEVING VISION 21 PROGRAM GOALS
The goals for the Vision 21 Program are very ambitious. If these goals can be achieved, Vision 21 technologies would offer the United States, and the world, a new method of coal-based power generation that would have significant advantages over current methods. Because coal is one of the most abundant resources in the United States (and in the world), the development of coal as an environmentally acceptable resource is a major objective of the Vision 21 Program. Power generated by Vision 21 plants would be produced at the same or lower cost as power generated by natural gas in areas where gas is available and at lower cost in areas where gas is not available at reasonable rates.
The committee believes that the Vision 21 Program should be a separate program area in DOE's Office of Fossil Energy (OFE) with its own clearly defined budget for both revolutionary and evolutionary changes in advanced technologies for 2015 and beyond. Meeting the program goals should not be taken for granted. The Vision 21 Program Plan encompasses a broad range of technological options and will require a well defined process that includes systematic procedures for setting priorities and downselecting options based on progress towards meeting interim targets. Program success will require breakthroughs in cost and technical performance in a number of technologies. For example, significant improvements will be required in the relatively mature field
of coal gasification to reduce costs by a factor of about two. Innovative approaches will have to be developed for several gasification subsystems to achieve the required cost reductions. Hybrid combinations of advanced gas turbines and high-temperature fuel cells will be required to achieve the program's efficiency goals. Testing of the first experimental units is scheduled for 2000, but these technologies will not be ready for commercialization for many years, although some of the components, systems, and subsystems may become commercially available in the interim.
Strategies for an Uncertain Future
The Vision 21 Program should promote R&D that maintains cost-competitive options for using a diverse mix of fossil fuels for power generation. A key element of this R&D should be the effective removal of current environmental concerns and impediments associated with producing electricity, transportation fuels, and chemical feedstocks from fossil fuels, including natural gas, petroleum, and coal.
Based on current conditions, the outlook for future energy supplies and conversion technologies indicates a growing reliance on natural gas as the economic fuel of choice for the generation of electric power. Although relatively low-cost, abundant supplies of natural gas are projected to be available for the foreseeable future, the committee also recognizes that the future is inherently uncertain and long-term projections of price trends and fuel mixtures could easily be wrong. The role of coal could decline rapidly if future environmental policies (in response to concerns about global climate change) require sizeable reductions in emissions of carbon dioxide from U.S. power plants. Therefore maintaining a diverse, low-cost energy supply will require controlling these emissions through carbon management.
A key premise of the committee's deliberations is that carbon management will be an element of future environmental policy and that the timing and stringency of environmental regulations will have a substantial affect on the use of coal for power generation. The Vision 21 Program must be able to accommodate a range of scenarios with regard to this key issue. Advanced fossil-fuel technologies, especially coal-based technologies, must be able to meet increasingly stringent environmental requirements for ''criteria" air pollutants (sulfur dioxide, oxides of nitrogen [NOx], particulate matter, and toxic air pollutants), as well as other environmental issues (such as liquid and solid waste), and still remain cost competitive with other fossil fuels, especially natural gas.
Coordination of Research and Development
Vision 21 should be a well defined activity focused on advanced technologies for 2015 and beyond. A distinguishing feature of these technologies should
be that they provide options for using coal and other fossil fuels in a carbon-constrained world. They should also incorporate substantial improvements in environmental design that eliminate nearly all emissions of air pollutants, liquid pollutants, and solid wastes.
To succeed in the marketplace, Vision 21 technologies must also be cost competitive with other long-term options for producing electricity, process heat, transportation fuels, and chemicals. Dedicated efforts will be required to commercialize and deploy Vision 21 technologies in both international and domestic markets. In the near term (prior to 2015), the greatest opportunities for commercializing new coal-fired power-generation technologies will most likely result from OFE's other R&D programs in advanced combustion systems and other near-term (2000–2015) technologies.
Meeting the technical challenges of the Vision 21 Program will require a continual stream of new ideas, innovations, and improvements in fundamental understanding that can only come from a sustained program in basic science and engineering. Other DOE programs, such as the Office of Science and OFE's Advanced Research and Technology Development Program, should be directed toward meeting the needs of the Vision 21 Program and encouraged to incorporate new developments into Vision 21 concepts.
Recommendation. Over time, Vision 21 should become the primary focus of Office of Fossil Energy's program in coal and power systems.
Recommendation. The U.S. Department of Energy (DOE) should develop mechanisms to link the Vision 21 Program with other basic science and engineering research programs in and beyond DOE. DOE should also coordinate the domestic and international commercialization and deployment of Vision 21 technologies.
Recommendation. All research and development (both revolutionary and evolutionary) related to in-plant carbon management should be part of the Vision 21 Program, with most of the effort focused on the development of revolutionary approaches for capturing and separating carbon dioxide.
Recommendation. As part of an industrial-ecology approach, which includes the integrated management of solids and liquid waste streams, the U.S. Department of Energy should determine whether "eliminating environmental concerns" is an achievable goal. If it is, the Vision 21 Program should define specific emissions goals for eliminating environmental pollutants from Vision 21 plants. The emissions goals should include a precise definition of the concept of "near-zero" emissions. Integrated plant designs should then include the processing of periodic wastes, such as spent catalysts, saturated absorbents, contaminated solvents, and water treatment sludge.
Although highly efficient processes will be important for both carbon management and the minimization of environmental impacts, the Vision 21 Program may be placing too much emphasis on thermal efficiency as a goal (e.g., a 60-percent efficiency rate for coal-based electric power generation by 2015).
Recommendation. The U.S. Department of Energy should establish criteria for making trade-offs to facilitate the early commercialization of significantly improved technologies that would provide significant improvements (even though they fall short of the ultimate goals for Vision 21) and would be competitive in the power-generation market. Vision 21 should simultaneously pursue high thermal efficiency and market expectations for:
effective performance (including low environmental impact)
low capital and operating costs
improved reliability, availability, and maintenance
improved flexibility and operability
All of these factors should be considered in the prioritization and selection of technologies for continued development and support.
As environmental emissions at Vision 21 plants approach the "near-zero" goal, upstream emissions from the mining, beneficiation, and transportation of coal and other fossil fuels will become increasingly important. Trade-offs may be necessary between in-plant and upstream mitigation.
Recommendation. The selection criteria and program planning framework for Vision 21 designs and concepts should include a full life-cycle analysis that includes the entire fuel cycle.
The Vision 21 Program Plan does not discuss the use of facilities that will have to be built or renovated to test new components and systems. There appears to be an assumption that this demand will somehow be met outside the program.
Recommendation. The U.S. Department of Energy (DOE) should make facilities at the Power Systems Development Facility, all of the Clean Coal Technology Program projects, and the National Energy Technology Laboratory available for sequential and concurrent development and tests of Vision 21 component technologies. DOE should fund modifications and side-stream tests at Clean Coal Technology plants, particularly integrated gasification/combined-cycle plants, to test breakthroughs or evolve processes.
The committee reviewed five enabling technologies in the Vision 21 Program Plan: fuel-flexible gasification, advanced combustion systems, advanced fuels and chemicals, fuel cells, and fuel-flexible gas turbines.
The committee believes that the focus of the enabling technology programs (and of the Vision 21 Program) should be coal gasification, which is the major element of the fuel-flexible gasification program. This conclusion is based on the following considerations:
Coal, coke, and heavy-oil gasification processes produce a fuel gas that can be efficiently cleaned and converted to electricity in fuel-flexible gas turbines and fuel cells. At this time, the only plausible approach to meeting the 60-percent efficiency goal of the Vision 21 Program will require converting that gas to electricity in gas-turbine, combined-cycle, fuel-cell, or fuel-cell/gas-turbine systems.
Coal gasification produces a more concentrated carbon dioxide stream that should be less expensive to capture than the carbon dioxide from the flue gas of current coal-fired power plants.
Competitive power generation with natural gas with the same types of fuel-flexible gas turbines will require that the investment cost of the direct syngas production section of Vision 21 plants be reduced from the current target of $850/kW to less than $550/kW. The committee encourages DOE to pursue both revolutionary and evolutionary improvements, which would complement each other in achieving the ambitious goals of the program.
Recommendation. DOE should pursue both revolutionary and evolutionary approaches to the development of gasification systems to achieve the performance and cost targets. Innovative, high-risk research can complement evolutionary improvements in subsequent generations of the components and systems of particular technologies. The gasification sections of integrated Vision 21 plants contain many highly integrated components (coal handling, oxygen production, gasification, gas cleaning, heat exchange), and significant cost reductions will be necessary to meet the overall Vision 21 goal.
Advanced Combustion Systems
This enabling technology program has two major elements: pressurized fluidized-bed combustion (PFBC) and indirectly fired cycles (IFC). The PFBC has been demonstrated at an 80-MW scale in four plants and has been scaled up in one plant with a capacity of 300 MW. IFC is still in the R&D phase.
Recommendation. Advanced combustion should not be included in the Vision 21 Program. Work on advanced combustion technologies should be continued as part of the main U.S. Department of Energy program to improve power-generating technologies. If new approaches are conceived that support the 60-percent efficiency goal by 2015, an advanced combustion element should be added to the Vision 21 Program.
Advanced Fuels and Chemicals
For every ton of fuels and chemicals produced by coal-based plants using conventional Fischer-Tropsch technology, three tons of carbon dioxide are produced. If natural gas is used as the feedstock instead of coal, less than one ton of carbon dioxide is produced. In a carbon-constrained environment, this will be a major drawback for coal-based technologies.
Recommendation. Research and development (R&D) in the Vision 21 Program should be directed away from the well researched areas of Fischer-Tropsch synthesis and focused on the production of fuels, chemicals, and syngas derived from coal and other solid fuels with low hydrogen-to-carbon ratios. R&D should be focused on novel catalysts, reactors, and fuel and chemical products that could potentially narrow the economic and environmental gap between coal-based (and petroleum-based) and natural gas-based fuels and chemicals. The goal should be to reduce the amount of carbon dioxide produced per ton of fuel and chemical product.
R&D on fuel cells should be focused on reducing the production cost of high-temperature fuel-cell systems. R&D should include system studies to identify promising options for integrating the fuel cell, gasification, and gas turbine sections of Vision 21 plants. Another problem that must be addressed is contaminant cleanup for the product gases from coal-gasification systems so that they can be used in fuel-cell systems.
Recommendation. The focus of Vision 21 should be on reducing the capital costs of fuel-cell systems in large-scale, coal-gasification, central station power plants. The distributed power-generation fuel-cell program should be continued
as part of the U.S. Department of Energy's baseline program and should not be included in the Vision 21 Program.
Fuel-Flexible Gas Turbines
The committee concurs with the Vision 21 Program Plan, which calls for using vendor-developed products as the basis for Vision 21 plants. However, only limited testing on hydrogen combustion is included. Vision 21 R&D should be focused on cycles that use hydrogen (from coal gasification) rather than syngas as the fuel for gas turbines to determine the need for unique components.
Recommendation. The U.S. Department of Energy (DOE) should look further ahead into the twenty-first century in formulating its Vision 21 plans. The advanced turbine system machines proposed as the core of the Vision 21 Program will be approaching the end of their model life cycle in 2015 and are likely to be supplanted in the marketplace by machines with higher efficiencies (either through higher firing temperatures or more sophisticated thermal integration cycles). To optimize its research, development, and demonstration program, DOE must consider the effects of these products on the marketability of Vision 21 technologies. Vision 21 research should focus more on cycles that result in hydrogen, rather than syngas, as the fuel for gas turbines to determine if unique components will have to be developed.
SUPPORTING TECHNOLOGIES AND SYSTEMS INTEGRATION
Support for technologies and systems integration will be essential for commercial Vision 21 plants. The ability of a process or power plant to perform to its design capability will depend largely on the engineering integrity of its components and support systems.
Advanced Modeling and Systems Analysis
Computer-based modeling and simulation are critical to three areas of the Vision 21 Program Plan: (1) systems analysis, (2) advanced computational modeling and the development of virtual demonstration capability, and (3) systems integration. Computer-based tools will be critical for identifying and designing the most promising Vision 21 configurations and for reducing the development time and cost of building Vision 21 systems and components. However, the technical level of the models described in the Vision 21 Program Plan is unrealistic and unlikely to be achieved in the Vision 21 time frame (i.e., the next 15 years).
Recommendation. The U.S. Department of Energy should assess the current state of the art of science-based modeling capabilities at both the component and systems levels as a basis for refining its expectations for Vision 21 models. This assessment should clearly identify and distinguish among modeling capabilities at different levels of detail (e.g., mechanistic [molecular or microscale] modeling vs. more empirically-based engineering models).
Recommendation. The Vision 21 Program should include plans for a hierarchy of models, from simple, transparent models showing basic mass and energy balances and costs for process units and integrated systems to more complex, detailed models of components and systems. The hierarchy should be based on dynamic simulations, as well as steady-state modeling of components and systems. It should also include the capability of coupling performance models and cost models, as well as analyzing the effects of uncertainty.
Recommendation. The U.S. Department of Energy should develop a management plan and an institutional capability to carry out computer-based modeling, systems analysis, and systems integration activities. The plan should include mechanisms for verifying or qualifying the performance of models; assessing and characterizing their reliability; maintaining and updating all Vision 21 models and modeling capabilities; and ensuring that models and modeling capabilities are made available to interested parties.
Materials and Heat Exchangers
The commercial availability and long-term survivability of materials is a critical area for all advanced power-generation technologies, regardless of fuel source. Resolving materials-related problems for coal-based technologies will be extremely challenging. The numerous technology configurations for Vision 21 systems, as well as for other future electric power-generation options using coal as feedstock, present different materials problems. Therefore, the materials R&D program, including commercial deployment, should be closely coordinated. The success of the Vision 21 Program will depend largely on the timely development, demonstration, and commercialization of advanced, cost-competitive, reliable materials and high-temperature, corrosion-resistant coatings.
DOE's R&D on materials and heat exchangers is currently dispersed among several DOE programs. The focus of the Vision 21 Program should be on high-temperature components, rather than high-temperature materials.
Recommendation. All Vision 21 materials-related development activities should be focused and coordinated with other federally funded materials research and development (R&D) programs. Vision 21 does not have the time or resources for
a pure materials program and should, therefore, focus on a component development program. All Vision 21 materials R&D should be driven by component design and reassessed in light of the aggressive goals of the Vision 21 Program.
Recommendation. The U.S. Department of Energy should develop and test a systematic, well defined program for deploying high-temperature membranes for oxygen separation from air and hydrogen separation from syngas. Because separation will be a critical step in the gasification-based Vision 21 plant, this program should be given a high priority.
Recommendation. The U.S. Department of Energy should place a high priority on the development of high-temperature coatings and materials, which will be essential for all advanced generation technologies.
Environmental Control Technologies
Advanced emissions controls have been identified as a key technology area in the technology road maps for electric power and fuels. Vision 21 proposes eliminating the environmental concerns associated with the use of fossil fuels. However, the boundaries and responsibilities for capturing and sequestering carbon dioxide are not clearly defined.
Recommendation. The program to develop a low-NOx combustor and integrate energy systems with terrestrial sinks should be removed from the Vision 21 Program and transferred to the U.S. Department of Energy's ongoing program. Vision 21 should focus on much larger and more fundamental issues: the removal of NOx, sulfur dioxide, metals, and other toxins from effluent streams, evolutionary and revolutionary technologies for capturing carbon dioxide, and other separation technologies.
Recommendation. The types and concentrations of impurities from gasification-based processes will be significantly different from those in combustion-based effluent streams. The U.S. Department of Energy should make early investments in new approaches for capturing effluent and new disposal methods based on solid scientific and engineering concepts. The time frame for the implementation of these novel approaches should be extended beyond 2015.
Recommendation. Vision 21 plants should be designed to allow for new technologies for capturing and separating carbon dioxide to be integrated into plant designs if they become viable within the extended timeline of the program. The transport and ultimate disposal of a concentrated carbon dioxide stream should be addressed in other research programs.
Gas separation will be required for many critical modules of Vision 21 plants. In general, the most difficult challenge will be to develop suitable materials.
Recommendation. The U.S. Department of Energy (DOE) should continue testing materials with near-term implementation at existing facilities until 2004. DOE should also develop a fundamental materials science program to improve the mechanical properties and chemical reactions of materials at high temperatures. The materials development program should be coordinated with the testing to ensure that the materials meet the requirements for Vision 21 technologies.
Gas separation is a critical process step for gasification/fuel cell-based Vision 21 plants. All of the separation concepts being pursued are novel and technologically challenging.
Recommendation. When bench-scale data are available on permeation rates, selectivity, and lifetimes, Vision 21 should conduct an independent economic assessment of advanced hydrogen-separation membrane technology, including associated cost uncertainties and a comparison with conventional hydrogen-recovery technology, before initiating a major development program.
Recommendation. The Vision 21 Program should investigate the carbon dioxide hydrate-based technology concept for capturing carbon dioxide; the energy and capital cost assumptions should be reviewed periodically to confirm the low costs claimed in preliminary process design studies. The technologies chosen for carbon dioxide recovery should be resistant to low-temperature absorption and regeneration.
Hydrogen Production from Water Dissociation
This program will investigate the use of an inorganic proton-transfer membrane for the generation and separation of hydrogen from high-temperature steam.
Recommendation. The first milestone for the program on hydrogen production from the dissociation of water should be an independent review to identify engineering and economic hurdles that will have to be overcome for this concept to become commercially attractive.
COMMERCIALIZATION OF VISION 21 TECHNOLOGIES
The commercialization of Vision 21 technologies, both domestically and internationally, in the post-2015 period will be extremely difficult. The construction of prototype, or commercial-scale, demonstration plants is not currently included in the Vision 21 Program Plan. The goals of the program are restricted to providing complete commercial plant designs and cost estimates, as well as verified virtual simulations of plant performance and demonstrations of key modules. The committee does not believe the designs, cost estimates, virtual simulations, and module demonstrations will be convincing unless they are accompanied by a commercial deployment program. Vision 21 plants based on commercial designs will not be in service until at least 2020, and full deployment of Vision 21 plants should not be expected before 2030.
Conditions in the post-2015 world may be very different from conditions today: (1) continued global economic growth may lead to greatly increased consumption of electricity and fuels; (2) environmental pressures may lead to a global regime of carbon management, as well as widespread, stringent local regulations on air emissions; and (3) restricted availability of gas supplies in many regions and extensive replacements of both coal and nuclear power plants may create many new market opportunities for coal-based power generation.
Recommendation. The U.S. Department of Energy should sequence its commercialization strategy for Vision 21 technologies to encourage the commercialization of components as they become available in the post-2010 time frame. Early commercialization would capitalize on the domestic and international opportunities for improved coal-based technologies.
Recommendation. The U.S. Department of Energy should work with private industry to develop an incentive program for the first three to five installations to overcome the technical and economic risks associated with early domestic or international commercial applications of new technologies.
DOE (U.S. Department of Energy). 1999. Vision 21 Program Plan: Clean Energy Plants for the 21st Century. Morgantown, W.V.: Federal Energy Technology Center.