Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 115
Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report 4 Hydrogen and Biofuels The FreedomCAR and Fuel Partnership was originally focused on power systems driven by hydrogen fuel cells but now is examining three power system approaches: fuel cells using hydrogen, advanced combustion engines using biofuels, and plug-in hybrid electric vehicles (PHEVs) and battery electric vehicles (BEVs) using electricity. This chapter reviews programs focused on providing the fuels needed by the first two of these approaches while minimizing petroleum imports and greenhouse gas emissions. The issue of interfacing between the nation’s electricity transmission and distribution system to provide the electricity needed for PHEVs and BEVs is addressed in Chapter 2, “Crosscutting Issues.” Hydrogen is an energy carrier produced from a variety of energy sources as discussed in this chapter and is the fuel that makes vehicular fuel cells feasible. Biofuels, energy carriers for solar energy and thus renewable fuels, are produced from a variety of biological sources, such as plant materials or algae. Programs on each of these approaches are reviewed in this chapter. HYDROGEN PRODUCTION, DELIVERY, AND DISPENSING As discussed in Chapter 1, the FreedomCAR and Fuel Partnership in the Department of Energy’s (DOE’s) Office of Energy Efficiency and Renewable Energy (EERE) includes the hydrogen production, delivery, and dispensing program, which is in turn part of the Hydrogen, Fuel Cells, and Infrastructure Technologies program (HFCIT; now called the Fuel Cell Technologies [FCT] program). This program addresses a variety of means of producing hydrogen in distributed and centralized plants using technologies that can be made available in the short, medium, and long term. The manager of the FCT program is the
OCR for page 116
Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report overall DOE hydrogen program manager. There are three fuel technical teams: fuel pathway integration, hydrogen production, and hydrogen delivery, with participation from the DOE and five energy companies that joined the Partnership 5 years ago. The technical teams report to the Fuel Operations Group, consisting of energy directors and DOE program managers, who in turn report to the Executive Steering Group. A number of important programs related to FCT are carried out in other parts of the DOE. Work on growing, harvesting, transporting, and storing biomass as well as work on using solar heat to produce hydrogen are also carried out in the EERE but are not part of the Partnership.1 The Office of Fossil Energy (FE) supports the development of technologies to produce hydrogen from coal and related carbon-sequestration technologies. The Office of Nuclear Energy (NE) supports research on the potential use of nuclear heat to produce hydrogen, and the Office of Science (SC) supports fundamental work on new materials for hydrogen storage, catalysts, and fundamental biological or molecular processes for hydrogen production, as well as work potentially affecting other areas of the FreedomCAR and Fuel Partnership. As discussed elsewhere in this report, the DOE recently added two utility partners to the Partnership to address issues associated with emergence of PHEVs and BEVs. With time this should bring additional attention to the issues associated with providing the required electricity while increasing energy security and reducing greenhouse gas (GHG) emissions. In reviewing the hydrogen production, delivery, and dispensing area, the committee considered whether it is appropriate for the federal government to be involved, and without exception the committee concluded that government involvement is appropriate and needed. As will be shown in this chapter, the DOE through the FCT program continues to make substantial progress, ensuring that hydrogen can be made available to meet the needs of fuel-cell-powered vehicles as they emerge. Continued work is needed to minimize cost and GHG emissions and reduce dependence on natural gas. Although the current abundance and low cost of natural gas make it attractive as a transition source of hydrogen, reducing dependence on natural gas should remain a long-term objective for hydrogen production. HYDROGEN FUEL PATHWAYS The hydrogen fuel/vehicle pathway integration effort is charged with looking across the full hydrogen supply chain from well (source) to tank. Specifically, the goals of this integration effort are to (1) analyze issues associated with complete hydrogen production, distribution, and dispensing pathways; (2) provide input to 1 This EERE program is coordinated with programs in the Department of Agriculture. See on the Web <http://www.usda.gov/wps/portal/!ut/p/_s.7_0_A/7_0_1OB?navid=ENERGY&navtype=MS>.
OCR for page 117
Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report the Partnership on goals for individual components; (3) provide input to the Partnership on needs and gaps in the hydrogen analysis program including the important industrial perspective; and (4) foster full transparency in all analyses, including an independent assessment of information and analyses from other technical teams. This effort involves source-to-vehicle-tank analysis, including costs, energy use, safety, availability of critical resources, and carbon dioxide (CO2) emissions. The accomplishment of these goals is overseen by the fuel pathways integration technical team (FPITT), with representation from the DOE, the energy companies, and the National Renewable Energy Laboratory (NREL). FPITT’s expertise supports the analysis efforts of the Partnership, coordinates fuel activities with the vehicle systems analysis technical team, recommends additional pathway analyses, provides input from industry on practical considerations, and acts as honest broker for the information generated by other technical teams. The DOE continues to make important progress toward understanding and preparing for the transition to hydrogen fuel. In the continuing source-to-wheels analysis, seven pathways, including both distributed and centralized hydrogen production, have been assessed, and the key drivers for pathway costs, energy use, and emissions have been identified. In addition, estimates have been developed for the water, electricity, natural gas, and platinum requirements for various pathways, and a biomass supply-and-demand assessment for major U.S. cities and regions was developed. A hydrogen quality study by the Argonne National Laboratory (ANL) was reviewed, and efforts are underway to incorporate hydrogen quality, cost, and benefit into the pathway analysis protocol. This will be very important, given that different pathways produce hydrogen with different levels of impurities that significantly impact performance and perhaps durability. The Society of Automotive Engineers (SAE) and the International Organization for Standardization (ISO) have developed standards for hydrogen purity that should be finalized in 2010. These standards can be further modified if research indicates that different standards are justified. The technology is available to produce and distribute hydrogen commercially for large users, but it is not yet completely optimized and cost-effective for supplying local vehicle fueling stations. Research efforts are focused on the further development of options that reduce cost, dependence on imported petroleum and natural gas, and greenhouse gas emissions. The primary constraint to the broad availability of hydrogen is the construction of a distribution system similar to the natural gas pipeline network. The Partnership has already developed several options for distributed hydrogen generation that could be used while such a national distribution system is being built. As indicated above, the long-term effort of the Partnership has thus far been focused on hydrogen. However, the Partnership now is examining three power system approaches, only one of which involves hydrogen: fuel cells powered by hydrogen, advanced combustion engines powered by biofuels, and PHEVs and BEVs powered by electricity. Clearly, additional effort is needed to develop mean-
OCR for page 118
Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report ingful comparisons of the fuel implications of these three approaches. As the fuel pathways integration technical team has indicated, biomass resource information is inconsistent and often outdated. And further definition is needed of the effects of significant penetration of PHEVs and BEVs in the market on electricity generation and distribution, including the impacts on the use of imported oil or gas and emissions of greenhouse gases as well as criteria pollutants. Recommendation 4-1. The DOE should broaden the role of the fuel pathways integration technical team (FPITT) to include an investigation of the pathways to provide energy for all three approaches currently included in the Partnership. This broader role could include not only the current technical subgroups for hydrogen, but also subgroups on biofuels utilization in advanced internal combustion engines and electricity generation requirements for PHEVs and BEVs, with appropriate industrial representation on each. The role of the parent FPITT would be to integrate the efforts of these subgroups and to provide an overall perspective of the issues associated with providing the required energy in a variety of scenarios that meet future personal transportation needs. HYDROGEN PRODUCTION The hydrogen production program embodies hydrogen generation from a wide range of energy sources as a means of enhancing U.S. energy security and reducing GHG emissions. The hydrogen production technical team facilitates the development of commercially viable technologies through nonproprietary dialogue among the commercial and federal sectors to guide program efforts. Energy sources under study include natural gas, coal, biological systems, nuclear heat, wind, solar heat, and grid-based electricity; grid-based electricity employs several types of energy sources to varying extents, depending on geographical area. Direct comparisons of the costs and other consequences of using these approaches are not included here because the technologies are at different stages of development and the adequacy of domestic reserves of the resources varies, as pointed out in the National Research Council’s Phase 2 report (NRC, 2008). In addition, hydrogen purity varies depending on the production approach used. Since hydrogen quality can affect fuel cell performance and durability, the cost of removing impurities to provide equivalent hydrogen may vary and influence the comparisons to some extent. The hydrogen production program includes both long-term and short-term approaches. In the short term, when a hydrogen pipeline system is not in place, distributed generation in relatively small plants will be required to supplement hydrogen available from existing, large-scale commercial plants. As the fleet of fuel-cell-powered cars grows and hydrogen demand increases, centralized hydrogen-generation plants with pipeline distribution will become increasingly attractive and are expected to partially replace distributed generation.
OCR for page 119
Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report The rest of this section reviews the DOE’s ongoing programs on hydrogen production involving thermal, electrolytic, and photolytic processes (DOE, 2010). Thermal Processes Approaches to hydrogen generation using thermal processes include coal and biomass gasification, reforming of bio-derived fuels, and high-temperature thermochemical splitting of water. The DOE’s program to improve natural gas reforming, completed in 2009, has established the feasibility of distributed generation at fueling stations using reforming and has directionally improved gas cleanup technologies for centralized plants. Commercial options now exist to generate hydrogen either in distributed or centralized plants using natural gas. Hydrogen Production from Coal and Biomass This subsection addresses the application of two domestic feedstocks, coal and biomass, to the manufacture of hydrogen. The production of hydrogen from coal or from biomass feedstocks appears in the Hydrogen Production Roadmap (DOE, 2009a,b) as both a midterm technology (coal gasification with carbon sequestration) and a long-term technology (biomass gasification with carbon sequestration). The most critical challenges to the use of either feedstock are (1) the capital cost of the gasification processes and (2) the cost and availability of carbon sequestration. Both feedstocks, coal and biomass, share a generally similar gasification process2 that has been in commercial use for nearly a century—the solid feedstock is gasified by reacting it with just enough oxygen to increase its temperature so that steam can react with the remaining carbonaceous material to produce “syngas,” a mixture of carbon monoxide (CO) and H2. The syngas is then cleaned to remove contaminants—such as particles, sulfur, ammonia, and mercury—and further processed to improve the ratio of H2 to CO by using the water−gas shift reaction (NAS/NAE/NRC, 2009). A wide slate of products can be produced, but those of chief interest here are hydrogen and CO2. In addition, electric energy could be sold as a by-product, possibly offsetting some of the cost of hydrogen production. Advantages and Limitations of Hydrogen Production from Coal and Biomass. Both feedstocks, coal and biomass, offer abundant, domestic resources for the manufacture of hydrogen. In the case of coal, most estimates suggest a resource sufficient to meet the needs of the United States for the next century at current 2 The distinct chemical and physical properties of each feedstock require special adaptation and so present challenges when coal and biomass are co-fired in a single gasification process.
OCR for page 120
Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report rates of consumption. However, use of the coal resource for hydrogen production will be paced by the availability of carbon sequestration—currently the secure disposal of the CO2 in underground reservoirs and possibly in the future disposal as a solid through advanced technologies. In contrast, biomass, though renewable, is limited by the sustainability of the land, water, and chemical resources required for its production. Further, the attractiveness of the biomass feedstock would be increased markedly if the CO2 that it emits could also be permanently sequestered from the biosphere. Thus CO2 disposal becomes an essential goal in the use of both coal and biomass for hydrogen. Yet for all its importance, a full-scale demonstration of permanent geologic storage has not been made within the U.S. legal, regulatory, and social framework, even though it has been demonstrated in a few locations around the world. Funding for carbon-sequestration research has grown steadily from about $69 million in FY 2006 to about $150 million in FY 2009. The American Recovery and Reinvestment Act of 2009 also allotted about $3 billion for projects to demonstrate this technology.3 The first U.S. demonstration, FutureGen, was discontinued in June 2008 but was started again with a new set of industrial partners a year later. The Department of Energy signed an agreement with its new industrial partners in the FutureGen Alliance to fund a reevaluation of the project for a 2010 go/no-go decision. Through regional partnerships in the United States, the DOE is planning to conduct 20 different tests by 2020. Worldwide, the target is 68 projects by 2020. This announced schedule implies that confirmation of the acceptability of the geological sequestering of CO2 could not be complete before 2020. In addition to geologic and terrestrial sequestration research and development (R&D) activities, the DOE also supports research on novel and advanced concepts that pursue chemical and biological methods of consuming CO2. Examples of chemical methods include capturing CO2 by reaction with magnesium sulfate to form carbonate, or formation of CO2 clathrate; examples of biological methods include microbial conversion of CO2 to methane or other hydrocarbons. In summary, the commercial deployment of coal-to-hydrogen production prior to the availability of publicly acceptable CO2 disposal will have adverse effects on CO2 emissions. The committee believes that at best the demonstration of CO2 sequestration is unlikely to see completion before 2020, and the record of similar projects suggests that it might well be later. Furthermore, the availability of biological feedstocks from sustainable sources is essential for biomass gasification to become a major producer of hydrogen. Recommendation 4-2. The DOE’s Fuel Cell Technologies program and the Office of Fossil Energy should continue to emphasize the importance of dem- 3 L. Miller, DOE, “Status and Outlook for Carbon Capture and Storage,” Presentation to the committee, October 26, 2009, Washington, D.C.
OCR for page 121
Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report onstrated CO2 disposal in enabling essential pathways for hydrogen production, especially for coal. Recommendation 4-3. The Fuel Cell Technologies program should adjust its Technology Roadmap to account for the possibility that CO2 sequestration will not enable a midterm readiness for commercial hydrogen production from coal. It should also consider the consequences to the program of apparent large increases in U.S. natural gas reserves. Recommendation 4-4. The EERE should continue to work closely with the Office of Fossil Energy to vigorously pursue advanced chemical and biological concepts for carbon disposal as a hedge against the inability of geological storage to deliver a publicly acceptable and cost-effective solution in a timely manner. The committee also notes that some of the technologies now being investigated might offer benefits in the small-scale capture and sequestration of carbon from distributed sources.4 Recommendation 4-5. The DOE should continue to evaluate the availability of biological feedstocks for hydrogen in light of the many other claims on this resource—liquid fuels, chemical feedstocks, electricity, food, and others. Reforming of Bio-Derived Fuels Before the demand for hydrogen is large enough to support large centralized production facilities, smaller distributed hydrogen generation at fueling station sites is expected to be the preferred option. The steam reforming of natural gas and water electrolysis are both technically attractive options for this. Neither process, however, provides a clear and practical renewable pathway. It is not practical to capture the CO2 from the distributed reforming of natural gas, and the electricity generated for use in electrolysis is dependent on the grid makeup, which on average releases large amounts of CO2. The distributed reforming of bio-derived liquids such as ethanol, sugars, or bio-oils can provide a renewable option for distributed hydrogen generation in the early stages of a hydrogen fuel buildup. A recent study concluded that, from a technical standpoint, up to 2 million barrels per day of gasoline-equivalent fuel could be produced from biomass available in 2020 but that the actual level of production could be achieved some time beyond that, in about 2035 (NAS/NAE/NRC, 2009). A wide range of bio-derived liquids can be reformed into hydrogen, but ethanol, being the largest produced biofuel, has received the most development attention. The process for steam reforming ethanol into hydrogen is similar to 4 A description of these advanced concepts appears on the Web at <http://fossil.energy.gov/programs/sequestration/novelconcepts/index.html>.
OCR for page 122
Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report that for steam reforming natural gas except for higher temperatures. In this sense steam reforming of ethanol requires little further development, but it still has some unique challenges that can be addressed. The primary challenges involve catalyst activity and coking and the overall cost of the hydrogen produced. Since the processes for the steam reforming of natural gas and ethanol are similar, it is expected that any process-related technology advances in one can be applied to the other. However, the feedstock cost issues are very different. The overall process of first producing ethanol from a cellulosic source, then transporting the ethanol to a station, and then reforming this into hydrogen results in a hydrogen cost that is higher than that for reforming natural gas. Its applicability then will be related to the relative costs of ethanol compared with that of natural gas and also to the value associated with the renewable aspect of hydrogen production. A tax on CO2 emissions would favor hydrogen from any biomass feedstock, including cellulosic ethanol reforming. It is possible, or even likely, that future state or federal regulations will encourage or mandate that a percentage of hydrogen be made in a renewable fashion. California already has such a program.5 Whereas distributed natural gas reforming has demonstrated the ability to meet the hydrogen cost targets of $2.00 to $3.00 per gallon gasoline equivalent (gge) (based on the DOE standard set of assumptions), distributed ethanol reforming has not. The current cost estimates are higher than $4.00/gge, and the targets for 2014 and 2019 are $3.80/gge and $3.00/gge, respectively. To meet these targets, further improvements are needed in catalyst performance, process design cost aspects, and feedstock cost reductions. All of these issues are being investigated, with indications of progress. The DOE is investigating using other bioliquids such as sorbitol, glucose, glycerol, methanol, propylene glycol, and less refined sugars such as cellulose and hemicelluloses that may have potential for cost improvements over ethanol. One promising technology path is aqueous-phase reforming that can process water-soluble carbohydrates such as glucose, sorbitol, glycerol, or methanol. The process conditions for aqueous-phase reforming are less severe than for the vapor-phase reforming that is used for natural gas or ethanol reforming. As a result, catalyst coking is not a significant problem as it can be for vapor-phase reforming. This technology is at a very early development stage and holds some promise for reducing costs. Laboratory batch experiments have indicated very high reactor conversion of cellulosic biomass (95 percent) at high hydrogen selectivity (74 percent). In summary, there is likely to be a need for a renewable distributed-hydrogen-generation method. Reforming a bioliquid is a viable approach. There are several different feedstock and technology pathways to do this—for example, cellulosic ethanol with vapor-phase reforming and glucose with aqueous-phase reforming, 5 See, for example, <http://www.energy.ca.gov/low_carbon_fuel_standard/>.
OCR for page 123
Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report among many others. It will be very difficult to meet the hydrogen cost targets without a significant reduction in current costs for bioliquid. Recommendation 4-6. The Partnership should prioritize the many biomass-to-biofuel-to-hydrogen process pathways in order to bring further focus to development in this very broad area.6 High-Temperature Thermochemical Splitting of Water The DOE is funding six projects that address the high-temperature technique of thermochemical water splitting for the centralized production of hydrogen. To split water directly by brute force requires temperatures of about 2000°C. By using various chemical cycles, the reaction temperatures can be reduced to the 500°C to 1100°C range. These temperatures can be achieved by many means, including next-generation high-temperature nuclear reactors or solar concentrators. Most solar design concepts for this centralized production method use power towers to get the high powers and high temperatures required. Some of the concepts also use electricity to power a still-elevated but much lower-temperature electrolysis step. Most of the work done so far in the area of thermochemical water splitting has been funded by the Office of Nuclear Energy and has been on the sulfur-iodine cycle. It is not clear to the committee that all attractive chemical cycles have been identified. Several projects are nearing completion, and this provides an opportunity to review and down-select projects to identify promising approaches. The committee understands that the Office of Nuclear Energy will not be funding chemical cycles for hydrogen production in the future. In the view of the committee, the EERE’s effort to identify solar, thermochemical approaches for future funding would be enhanced by carrying out a systems analysis of candidate systems after conducting a workshop to ensure that all promising, potential cycles have been identified. It would also be useful to see if any attractive options are evolving in the DOE Office of Basic Energy Sciences (BES) program, including the new Energy Frontier Research Centers. Recommendation 4-7. The Partnership should consider conducting a workshop to ensure that all potentially attractive high-temperature thermochemical cycles have been identified, and it should carry out a systems analysis of candidate systems to identify the most promising approaches, which can then be funded as money becomes available. Recommendation 4-8. The EERE funding for high-temperature thermochemical cycle projects has varied widely and was very low in FY 2009. The committee 6 N. Gupta, “Hydrogen Production Technical Team,” Presentation to the committee, Slide 11, Biomass Processes, August 5, 2009, Southfield, Michigan.
OCR for page 124
Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report believes that these centralized production techniques are important, and thus adequate and stable funding for them should be considered. Electrolytic Processes This subsection covers programs aimed at splitting water using electricity in an electrolysis process. The coupling of wind power with electrolysis is included as one embodiment of this technology. In the long term, water electrolysis represents a significant option for hydrogen generation in the development of a refueling infrastructure. Its attractiveness stems from the fact that (1) it is relatively simple compared to alternative methods; (2) it can positively impact carbon emissions if powered by renewables; (3) it can generate relatively pure hydrogen, potentially at elevated pressure, thereby making downstream cleanup processing simpler and reducing compression requirements; and (4) its efficiency is largely independent of unit size. Furthermore, water electrolysis can be placed at the “point of use,” allowing it to satisfy regional hydrogen supply needs, while at the same time it has the potential for large-scale centralized operations. In the near term the process is attractive, as it can facilitate a proof-of-concept fueling option because water electrolysis technology and systems are available today. However, water electrolysis is still a small segment of the total hydrogen-generation capacity, because capital costs are high and have not been seriously reduced to date, and operating costs are high; together these costs lead to high-cost hydrogen. Except for selected military and industrial-based uses, electrolysis systems have been built without volume and cost-reduction benefits due to the lack of high-volume manufacturing. Even with these limitations, conventional water electrolysis exhibits high efficiencies (percentages in the 70s versus lower heating value [LHV]) and long lifetimes using multiple chemistries and processes, and electrolysis systems are available commercially in low- and high-volume production of gas. The primary R&D activities are focused on component or engineering (balance of plant) enhancements. Such advancements have the potential to impact the energy requirements that are over and above what is needed to split the water from the perspective of a fundamental electrochemistry requirement. Examples of R&D activities include new membranes for both acid and alkaline chemistries, hardware and configuration changes, and advanced catalysis. Specifically, membrane development could possibly impact the resistance of the stack, thereby reducing the ohmic losses if the membrane has enhanced conductivities over those of currently used materials. In all cases, such energy-consumption-reduction and capital-cost-reduction efforts will have to succeed without seriously impacting the efficiency and lifetimes currently exhibited in commercial and military electrolyzers. Lastly, such developments must make progress against the goals for hydrogen cost. Presented in Table 4-1 are the DOE cost targets for distributed hydrogen generation from water electrolysis.
OCR for page 125
Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report TABLE 4-1 DOE Cost Status and Targets for Distributed Hydrogen Generation from Water Electrolysis, 2006, 2012, 2017 Characteristics/Units 2006 Status 2012 Target 2017 Target Hydrogen cost, $/kg H2 4.80 3.70 <3.00 Electrolyzer capital cost, $/kg H2 1.20 0.70 00.30 Electrolyzer efficiency, % Based on LHV 62 69 74 Based on HHV 73 82 87 NOTE: LHV, lower heating value; HHV, higher heating value. SOURCE: See DOE’s Multi-Year Research Development and Demonstration Plan: Planned Activities for 2005-2015 (updated April 2009). Available on the Web at <http://www1.eere.energy.gov/hydrogenandfuelcells/mypp/pdfs/production.pdf>. Higher-risk, longer-term new technologies have been recently reported (Farmer, 2009) and include both high-temperature electrolysis and the photo-electrolysis of water. High-temperature electrolysis has advantages in the reduction of energy requirements to split water owing to the lower voltage requirements to dissociate water, but it requires high-temperature materials that are challenging. The high-temperature option, using solid oxide technology, also has the potential to make use of waste thermal energy, thereby making nuclear power plants attractive locations for centralized generation. Another aspect of the long-term potential of the electrolysis process is that there are variations of the engineering configurations, making it even more attractive by possibly reducing system complexity. For example, in selected cases, hydrogen may be generated at substantial pressures, thereby reducing the need for follow-on mechanical compressors (DOE, 2005). Furthermore, from a final cleanup perspective, as electrolysis generates relatively pure hydrogen, the final cleanup stage from a pressurized system may use alternative, existing know-how to remove residual oxygen and moisture efficiently (e.g., high-pressure electrolysis followed by passive membrane separation). In such cases, the electrolyzer may be able simply to generate pressure and purity without significantly impacting electrical consumption and capital. If such is accomplished, refueling hydrogen may be available in remote and non-methane-accessible regions that meet hydrogen purity specifications. The DOE recognizes that water electrolysis may play an important role in the hydrogen infrastructure, and the DOE is supporting numerous electrolysis efforts related to capital, electrocatalytic processes, and configuration and engineering. In addition, a number of systems analyses now include water electrolysis. Furthermore, photoelectrolysis has the potential to improve the efficiency of water splitting, but fundamental research is needed to establish the feasibility of this approach relative to conventional electrolysis (DOE, 2008).
OCR for page 126
Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report Recommendation 4-9. Water electrolysis should remain an integral part of the future hydrogen infrastructure development. The DOE should continue to fund novel water electrolysis materials and methods, including alternative membranes, alternative catalysts, high-temperature and -pressure operation, advanced engineering concepts, and systems analysis. Additional efforts should be placed on advanced integration concepts in which the electrolyzer is co-engineered with subsequent upstream and downstream unit operations to improve the overall efficiency of a stand-alone system. Recommendation 4-10. Commercial demonstrations should be encouraged for new designs based on established electrolytic processes. For newer concepts such as high-temperature solid oxide systems, efforts should remain focused on laboratory evaluations of the potential for lifetime and durability, as well as on laboratory performance assessments. Wind- and Solar-Driven Electrolysis The DOE continues to study at NREL opportunities to couple wind and solar energy with electrolysis, and it has several projects to improve the efficiency of electrolyzers. The program has recently demonstrated about 70 to 71 percent efficiency at the stack level. Higher-pressure electrolyzers could be a thrust for the future and could reduce the compression energy for storage and vehicle refueling. The hydrogen storage can be used to offset at least in part the intermittent and variable nature of the wind and solar resource. This approach can be employed with three different energy pathways: wind to grid; wind to electrolysis unit to hydrogen; and hydrogen to fuel cell to grid. These outputs can be varied if there is not enough demand for hydrogen for vehicle fueling. Some of the challenges with a wind- and solar-driven electrolysis approach include efficient power electronics for dc-to-dc and ac-to-dc conversion, and controllers and communications protocols to match the source to the electrolyzer. Additional valuable data and experience can be gained by continuing the operation and upgrades of the facility at NREL. Recommendation 4-11. Work on close coupling of wind and solar energy with electrolysis should be continued with stable funding. Further improvements in electrolyzers, including higher stack pressure, and in power electronics will benefit this application. Photolytic Processes This subsection covers the discussion of programs oriented toward using solar energy to split water. Included are biological and photoelectrochemical hydrogen production.
OCR for page 127
Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report The production of hydrogen using microorganisms, utilizing energy by absorbing incident light and nutrients, can be a carbon-neutral process. The FreedomCAR and Fuel Partnership identifies four main biological production pathways: photolytic (direct water splitting), photosynthetic bacterial (solar-aided organic decomposition), dark fermentative (organic decomposition), and microbial-aided electrolysis (electric power-aided organic decomposition) (DOE, 2009b). The commercial viability of these processes is highly uncertain, and the Partnership classified this approach as “long term.” The activity has been supported by the BES. There are many barriers to technical success that, if overcome, would result in a process competitive with other pathways for hydrogen production. Thus, a possible application identified for this approach is to generate hydrogen from dilute feedstock in waste streams from other processes that would not be captured otherwise. The technical barriers include, among others, lack of information on microorganisms with suitable characteristics for biological hydrogen production; efficiency in light utilization; efficiency in feedstock utilization; cost; and product purity. In spite of the difficulties, the Partnership reported some noticeable progress—for example, the successful cloning of the Tla2 gene to enable 15 percent absorbed solar-to-chemical-energy conversion efficiency in microalgae. Internationally, this approach is pursued actively. Photoelectrochemical water splitting, utilizing electrolysis, converts solar energy directly into chemical energy in the form of hydrogen.7 A semiconductor material is used to collect light energy and produce hydrogen and oxygen using electrolysis. This also is supported by the BES and is classified as “long term.” Barriers to technical success are found in the semiconductor materials used to capture light energy, the photochemical device, the integration of the device into an operating system, and the development of the storage needed to compensate for the diurnal light cycle.8 Given these barriers, this could be the highest-risk approach currently in the program. Barring spectacular breakthroughs, the potential impact of biological and photoelectrochemical hydrogen production will be limited and far in the future. Support of this approach has been by BES, which is appropriate because of its exploratory nature and because discoveries could just as likely have applications other than for the Partnership. The committee finds no clearly defined targets or vision of the photolytic approach that will contribute to the overall hydrogen production goals, and as a result it is unclear whether the Partnership should retain this approach in its portfolio of activities. 7 Although interesting work is being done with the use of microorganisms and photoelectrochemical techniques to generate hydrogen, and R&D is expected to continue, it is too early to consider them as viable options in the context of Partnership goals. 8 Alternatively, hydrogen could be stored for use when there is no sunlight. This would also be a barrier, given the issues with hydrogen storage discussed in this report.
OCR for page 128
Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report Recommendation 4-12. The Partnership should examine the goals for the photolytic approach to producing hydrogen using microorganisms and formulate a vision with defined targets. Otherwise, this approach should be deemphasized as an active research area for hydrogen production. HYDROGEN DELIVERY, DISPENSING, AND TRANSITION SUPPLY A significant factor in fuel cost and (source-to-wheels) efficiency for fuel-cell-powered vehicles is the means for delivering, storing, and dispensing hydrogen, especially compared to the petroleum delivery system, which is low-cost and efficient. In a fully developed hydrogen economy, the postproduction part of the supply system for high-pressure hydrogen will probably cost as much as production and consume as much energy (NRC/NAE, 2004). The distribution costs are of even greater concern in the transition period when there is a lack of demand, particularly when hydrogen from centralized production is available. In such cases distribution could easily cost more than production. Dispensing systems for gaseous hydrogen must be designed to prevent excessive temperature increases in the vehicle tank during pressuring and filling, particularly for 700 bar (approximately 70 MPa or 10,000 psi) operation. As a result, communication between the vehicle and the refueling dispenser is required so that pressure and temperature can be monitored and controlled. As pointed out in the National Research Council’s Phase 2 report (NRC, 2008), there are five main ways to deliver hydrogen from centralized production to refueling stations: pipeline, liquid, gas containers, one-way liquid carriers, and two-way liquid carriers. Given the importance of the area, all of these have been studied in the program. The DOE program on the delivery, storage, and dispensing of hydrogen is comprehensive and includes aggressive cost targets (see Table 4-2). The goal is to reduce the delivery and dispensing cost to less than $1 per kilogram of hydrogen by 2017. This compares to current costs of $3-$5/kg at low volume and $2-$3/kg at high volume. Given that all of the physical steps involved in delivery and dispensing have been practiced for decades by the gas industry, the committee continues to question whether it will be possible to reduce costs to the target levels, but clearly significant cost reductions are very important to the outlook for hydrogen-powered vehicles. Funding of this important program has been variable. Funding of $1.1 million in FY 2006 and $6.3 million in FY 2007 was followed by $9.5 million in FY 2008 and $3.3 million in FY 2009. In spite of this inconsistent funding, progress has continued to be made. Cost has been reduced from $3-$5/kg to roughly $2-$3/kg through advances in pipelines, tube-trailers, and liquefaction.9 9 M. Gardiner and J. Kegerreis, “Hydrogen Delivery Technical Team,” Presentation to the committee, August 5, 2009, Southfield, Michigan.
OCR for page 129
Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report TABLE 4-2 Cost Targets for Hydrogen Delivery and Dispensing ($ per kilogram of hydrogen) Activity 2010 2012 2015 2017 Delivery from central plant to refueling gate <0.90 <0.60 Dispensing at refueling sitea <0.80 <0.40 a Includes compression/storage; centralized H2 available at 300 psi. SOURCE: NRC (2008), p. 98. Progress has been made in all areas of the program. Delivery models have been developed that predict delivery and dispensing costs for different methods as a function of market penetration. Hydrogen compression has been direction-ally advanced by investigating a centrifugal compressor design and also electrochemical compression. Promising aging studies on a fiber-reinforced polymer pipe material were completed. In addition, studies of carbon-fiber composites and glass fibers indicate that the capacity of tube trailers can be increased by a factor of two to three, leading to a potential cost reduction for these trailers, according to DOE estimates, of up to 50 percent. The plan for FY 2010 includes $4.5 million for this area. Past funding in the area of hydrogen delivery and dispensing has not been based on program needs but apparently on budget constraints. Reducing the cost of delivery and dispensing from the current $2 to $3 per kilogram of hydrogen to the 2017 target of less than $1 per kilogram of hydrogen will require substantial and consistent funding based on program needs. Otherwise, any chance of meeting the 2017 target will be forgone. Recommendation 4-13. Hydrogen delivery, storage, and dispensing should be based on the program needed to achieve the cost goal for 2017. If it is not feasible to achieve that cost goal, emphasis should be placed on those areas that would most directly impact the 2015 decision regarding commercialization.10 In the view of the committee, pipeline, liquefaction, and compression programs are likely to have the greatest impact in the 2015 time frame.11 The cost target should be revised to be consistent with the program that is carried out. 10 The program framework is based on a 2015 target date for getting all of the technical information needed by the automotive manufacturers to make decisions on commercialization of fuel-cell-powered vehicles. Presumably, these decisions will involve in part the assurance of the availability of hydrogen at a sufficient number of locations to provide the fuel needed. 11 Compression will take on even greater importance as the delivery pressure is raised from 350 to 700 bar (about 5,000 to 10,000 psi, or 35 to 70 MPa).
OCR for page 130
Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report BIOFUELS FOR INTERNAL COMBUSTION ENGINES Liquid hydrocarbon fuels made from biomass and used in an internal combustion engine (ICE) are another pathway that can have an effect on oil imports and CO2 emissions. This pathway differs from the other two primary pathways being developed by the Partnership in that the light-duty vehicle (LDV) and drive system do not require new technology for this pathway to grow. The hydrogen fuel cell pathway and the battery electrification pathway (hybrid electric vehicle [HEV], PHEV, and BEV) both require new drivetrain technology for them to begin and to grow. Biomass-derived ethanol and biodiesel are already available in the marketplace for use with today’s ICE cars. The technology development needs are almost all related to producing the biofuel rather than to the use of the biofuel in an ICE. About 8 billion gallons per year (BGY) of biofuels were produced in the United States in 2008, with most of this being ethanol made from corn. This amount is about 5 percent of the total gasoline use measured by volume, or a little less than 4 percent measured by energy content. Less than 10 percent of this 8 BGY is biodiesel made primarily from soy and waste oils. The total is planned to increase to 36 BGY by 2022, as outlined in the Renewable Fuel Standard that is part of the Energy Independence and Security (EISA) Act of 2007 (Public Law 110-140). Most of the increase beyond the present is scheduled to be from non-grain-based sources. Corn-based ethanol could grow to 12 BGY by 2012 but is not anticipated to grow beyond this. To accommodate these plans, a number of challenging barriers must be resolved with the biomass production, logistics, conversion into biofuel, distribution of the biofuel, and end use of the biofuel: Biomass production—The rapid growth of biofuels has come from the use of corn and soy for producing ethanol and biodiesel. To meet the future EISA targets, movement to second-generation sources (crop and forest residues) and even third-generation sources (energy crops such as perennial grasses, fast-growing trees, and algae) will be necessary. Feedstock logistics—Harvesting, storing, preprocessing, and delivering the biomass to a conversion facility can cost as much as 20 percent of the total cellulosic ethanol cost. Innovative business models and new technologies are needed to reduce these costs. Conversion to biofuel—Currently, cellulosic ethanol production and other biofuel technologies needed to reach the EISA targets are too expensive to compete in the marketplace. Cellulosic ethanol conversion technology is in the large-pilot-plant or small-demonstration-plant phase of development. Biofuel distribution—Much of the land area needed for increasing bio-fuel production will be in the Midwest, and by inference much of the biofuel production also, although much of the demand for biofuels will
OCR for page 131
Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report be on the coasts. A much larger system of trucks, trains, barges, blending and storage terminals, and perhaps pipelines and station storage will be needed. Biofuel end use—As ethanol use increases to meet EISA targets, the average gasoline blend will need to contain more than the current 10 percent maximum of ethanol (E10). Although some of today’s LDVs can use E85, the ability to move the entire LDV fleet to E20 and above is needed prior to achieving the 2022 targets. Biofuels and the FreedomCAR and Fuel Partnership Within the DOE, the Biomass Program12 has the responsibility for managing the development and progress for the bulk of the needs for biofuels, including the needs for biomass production, feedstock logistics, and biomass conversion to a biofuel. Historically the DOE focused on biofuel distribution and end use through the FreedomCAR and Fuel Partnership (DOE, 2010). This split of focus puts responsibility for making biofuels with the Biomass Program and the responsibility for delivering the biofuel and the LDV drivetrain responsibility with the FreedomCAR and Fuel Partnership. As this committee is reviewing just the Partnership and not the entire biofuel program, its comments apply to those areas for which FreedomCAR has responsibility. The split of focus described above appears logical and takes advantage of the capabilities within the Partnership developed over the last several years for systems analysis and the ongoing ICE development work. Just as the systems analysis of the hydrogen infrastructure has better defined the challenges, barriers, and possible solutions to implementing a hydrogen infrastructure, so too can a thorough analysis of the biofuel infrastructure identify barriers, possible solutions, and costs for distributing biofuels. A key assumption with regard to the use of biofuels is that all near- and mid-term biofuels must be fungible with existing liquid fuels and existing distribution infrastructure (DOE, 2010). Blending biofuels with gasoline and diesel as is done with ethanol and biodiesel has distinct advantages that hold down distribution costs by using a portion of the existing distribution system and takes advantage of the existing car technology and large gasoline and diesel markets for sales. Doing this creates impacts on the existing petroleum fuel distribution system and on vehicle drivetrain performance. E85 can be viewed as an example of how the biofuel affects the existing petro- 12 Algal biofuels are now receiving increased attention and are included in the DOE Aquatic Species Program of the Biomass Program (http://www1.eere.energy.gov/biomass/pdfs/algalbiofuels.pdf). With further research this could become a viable long-term option for producing biodiesel, gasoline, or other fuels. One other possible long-term option is the use of photosynthetic bacteria to produce hydrocarbons from CO2.
OCR for page 132
Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report leum system and the engine technology. Because of the high octane of ethanol (129 Research Octane Number [RON] and 102 Motor Octane Number [MON] and 116 [R+M]/2), a flexible fuel engine is designed to perform with both a regular 87 (R+M)/2 octane gasoline and the much-higher approximately 105 (R+M)/2 octane E85 so that it could use either fuel. If, however, the engine were optimized only for the high-octane E85, it could be made more efficient. From a petroleum refinery perspective, E85 is a fuel with excess octane giveaway, because the fuel has much higher octane than the gasoline specification. High-octane components of gasoline are much more expensive than are lower-octane components. If the 15 percent of petroleum gasoline components to the blend were optimized to take advantage of the excess octane, a lower-cost E85 could result. This example illustrates some of the complexities of integrating three large industries into an overall efficient system. The choice of the biofuel impacts both the design of the ICE and the makeup of the petroleum fraction blended with the biofuel. In the short term, ethanol is the biofuel of choice, as it is the only bio-fuel in the market now in a significant amount. Much of the research on biomass conversion, however, is focused on the next generation of biofuels, such as mixed alcohols, biobutanol, green gasoline, and diesel. A close collaboration between the three industries in the Biomass Program and the Partnership in analyzing the overall system should help ensure the best overall system design. As the emphasis for biofuel growth beyond that anticipated for ethanol is likely to come from a new biofuel or one that is blended with gasoline or diesel fuel, it creates an opportunity to improve the ICE overall efficiency through a fuel and engine optimization program. Furthermore, there is a need for a thorough systems analysis of the biofuel distribution and end-use system that accounts for engine technologies and petroleum-blending fuel properties could help to identify priority areas for further development. Such development could result in modified priorities for different biomass sources, conversion processes, biofuels, distribution systems, and engines. Recommendation 4-14. A thorough systems analysis of the complete biofuel distribution and end-use system should be done. This should include (1) an analysis of the fuel- and engine-efficiency gains possible through ICE technology development with likely particular biofuels or mixtures of biofuels and conventional petroleum fuels, and (2) a thorough analysis of the biofuel distribution system needed to deliver these possible fuels or mixtures to the end-use application. REFERENCES DOE (U.S. Department of Energy). 2005. Small Business Innovation Research and Small Business Technology Transfer Programs, Phase II Grant Abstracts, FY 2005, DOE Grant DE-FG02-04ER83905. Washington, D.C. DOE. 2008. Annual Progress Report, DOE Hydrogen Program. Section II-B, Electrolysis. Washing-ton, D.C.: Office of Energy Efficiency and Renewable Energy.
OCR for page 133
Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report DOE. 2009a. Hydrogen Production, Overview of Technology Options (January). FreedomCAR and Fuel Partnership. Available on the Web at <http://www1.eere.energy.gov/hydrogenandfuelcells/pdfs/h2_tech_roadmap.pdf>. DOE. 2009b. Hydrogen Production Roadmap, Technology Pathways to the Future (January). FreedomCAR and Fuel Partnership. Available on the Web at <http://www1.eere.energy.gov/hydrogenandfuelcells/pdfs/h2_production_roadmap.pdf>. DOE. 2010. Biomass Multi-year Program Plan (April). Office of Biomass Energy, Office of Energy Efficiency and Renewable Energy. Available on the Web at <http://www1.eere.energy.gov/biomass/pdfs/mypp.pdf>. Farmer, R. 2009. “Hydrogen Production.” DOE Annual Merit Review and Peer Evaluation Meeting, May 19. Arlington, Virginia. Available on the Web at <http://www.hydrogen.energy.gov/pdfs/review09/pd_0_farmer.pdf>. NAS/NAE/NRC (National Academy of Sciences/National Academy of Engineering/National Research Council). 2009. Liquid Transportation Fuels from Coal and Biomass: Technological Status, Costs, and Environmental Impacts. Washington, D.C.: The National Academies Press. NRC (National Research Council). 2008. Review of the Research Program of the FreedomCAR and Fuel Partnership, Second Report. Washington, D.C.: The National Academies Press. NRC/NAE (National Research Council/National Academy of Engineering). 2004. The Hydrogen Economy: Opportunities, Costs, Barriers, and R&D Needs. Washington, D.C.: The National Academies Press.
OCR for page 134
Review of the Research Program of the FreedomCAR and Fuel Partnership: Third Report This page intentionally left blank.