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Disclaimer This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees,
Disclaimer This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The view and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. An Overview of Hydrogen Production and Storage Systems with Renewable Hydrogen Case Studies May 2011 Prepared by: Timothy Lipman, PhD 1635 Arrowhead Drive Oakland, California (510) Prepared for: Clean Energy States Alliance 50 State Street, Suite 1 Montpelier, VT Conducted under US DOE Grant DE-FC3608GO18111 A000, Office of Energy Efficiency and Renewable Energy Fuel Cell Technologies Program This page intentionally blank Summary Hydrogen is already widely produced and used, but it is now being considered for use as an energy carrier for stationary power and transportation markets. Approximately million metric tonnes of hydrogen are produced in the US each year, enough to power million cars or 5-8 million homes. 1 Major current uses of the commercially produced hydrogen include oil refining (hydro-treating crude oil as part of the refining process to improve the hydrogen to carbon ratio of the fuel), food production (e.g., hydrogenation), treating metals, and producing ammonia for fertilizer and other industrial uses. In addition to the conventional hydrogen production methods of steam methane reforming (SMR) and grid-powered electrolysis, a new suite of renewable production options is emerging. These include using renewable power directly for electrolysis, various biogas production options using gasification or pyrolysis processes or biomass fermentation with microorganisms, and newly developed photo-electrochemical and thermo-chemical processes including using microbial electrolysis cells as well as tailored molecules that can facilitate the splitting of water molecules into hydrogen and oxygen with lower energy requirements than conventional electrolysis. Codes and standards for hydrogen storage and transport have evolved greatly over the past years and now cover most hydrogen applications being considered. Hydrogen is now being transported by trucks and pipelines, and is stored in vessels that are certified by ASME for stationary use or by the US Department of Transportation (DOT) for transportation/delivery uses. Examples of producing hydrogen using renewable resources include hydrogen production in a high-temperature, molten carbonate fuel cell tri-generation system that uses landfill gas, solar photovoltaic electrolysis for hydrogen to be used as a vehicle fuel at Honda s US headquarters in Torrance, California, and a California winery that is generating hydrogen on a demonstration basis using a new type of microbial electrolysis cell that is generating a mix of hydrogen and methane from winery wastewater. 2 Challenges to expanded use of hydrogen for stationary power production include better education and training of local codes-and-standards officials on the processes for hydrogen system permitting, continued efforts to bring down the costs of electrolyzers to enable renewable hydrogen production, improved efficiency and performance of steam methane reformers (particularly in smaller sizes), current relatively high costs for hydrogen storage and piping systems, and improvements in other scientific processes and technologies for producing hydrogen with low to zero emissions of greenhouse gases and costs that can ultimately be competitive in the energy marketplace. 1 Source is EIA, See reference list for full citation. 2 For additional information on these applications see the following sources: Fuel cell tri-generation: Honda solar PV station: California winery with microbial electrolysis cell: Table of Contents Introduction... 1 The Current Hydrogen Market... 5 Hydrogen Production Methods... 7 Hydrogen Production Costs Hydrogen Storage and Delivery Renewable Hydrogen Case Studies Honda s Solar Photovoltaic Hydrogen Electrolysis Station Fuel Cell Energy and Air Products and Chemicals, Inc. Hydrogen and Electricity Tri-generation System Napa Wine Company Hydrogen Production by Microbial Electrolysis Conclusion References... 24 Introduction Hydrogen is already widely produced and used, but it is now being considered for use as an energy carrier for stationary power and transportation markets. Although hydrogen is the most abundant element in the universe, where it appears naturally on the earth s crust it is bound with other elements such as carbon and oxygen instead of being in its molecular H 2 form. Molecular hydrogen is produced for various uses, and this can be done in various ways, as discussed below. Approximately million metric tonnes of hydrogen are produced in the US each year (EIA, 2008). For reference, this is enough to power million cars (using 700 to 1,000 gallon energy equivalents per car per year) or about 5-8 million homes. Globally, the production figure is around 40.5 million tonnes (equal to about 44.4 million short tons or about 475 billion cubic feet), and is expected to grow 3.5% annually through 2013 (Freedonia Group, Inc., 2010). Major current uses of the commercially produced hydrogen are for oil refining, where hydrogen is used for hydro-treating of crude oil as part of the refining process to improve the hydrogen to carbon ratio of the fuel, food production (e.g., hydrogenation), treating metals, and producing ammonia for fertilizer and other industrial uses. Because much of the hydrogen produced in the US is done in conjunction with oil production, much of this hydrogen is produced in three states: California, Louisiana, and Texas. This hydrogen is produced from steam reforming of natural gas, the most prevalent method of hydrogen production. There are other significant production facilities up the Mississippi River valley and in the Northeast. Figure 1 shows where various types of production facilities are located in the US, including both merchant and captive (i.e., for internal use) producers. A key point here is that vast amounts of hydrogen are currently produced and used in the US and around the world. It is a widely used industrial gas, with a well developed set of codes and standards governing its production, storage, and use. 3 However, for fuel cell applications a high level of hydrogen purity is typically more important than for many industrial applications and thus can often entail higher costs of delivery. 4 A growing use of hydrogen is to support emerging applications based on fuel cell technology along with other ways to use hydrogen for electricity production or energy storage. More than 50 types and sizes of commercial fuel cells are being sold, and the value of fuel cell shipments reached $498 million in Approximately 9,000 stationary fuel cell systems and 6,000 other commercial fuel cell units were shipped that year. The 15,000 total represented 40% growth over the previous year. In addition, 9,000 small educational fuel cells were shipped. (US DOE, 2010) 3 For the latest details on hydrogen codes and standards, see: and as well as the standards themselves (e.g., NFPA 55 and CGA H and CGA G ). 4 For example ISO and Society of Automotive Engineers (SAE) standard J2719 currently specify purity standards for fuel cell applications with 99.97% overall hydrogen purity and additional allowable levels of key impurities (e.g. 0.2 ppm carbon monoxide and additional upper limits on sulfur compounds, formaldehyde, etc.). Figure 1: Industrial Hydrogen Facilities in the US Source: NREL, 2006 As shown in Figure 2 below, there is significant potential to produce hydrogen using renewable resources. Very little of this potential is used at present (the facilities shown above in Figure 1 are mostly associated with natural gas or refinery products). The renewable production potential in the US ranges from as high as 650,000 kilograms per square kilometer per year (kg/km 2 /yr) in some areas to less than 50,000 kg/km 2 /yr. Large parts of the country have production potential greater than 100,000 kg/km 2 /yr (NREL, 2006). For reference, at the US average population density of about 30 people per square kilometer, 100,000 kg/km 2 /yr would be enough for about 3,300 kilograms per person per year, or enough to drive about 200,000 miles in a 60-mpg equivalent hydrogen-powered car. 5 5 Using the close approximation that one kilogram of hydrogen has the same energy content as a gallon of gasoline. Figure 2: Estimated US Hydrogen Potential From Renewable Sources Source: NREL, 2006 As for overall hydrogen production potential, a 2009 analysis by the National Renewable Energy Laboratory (NREL) titled Hydrogen Potential from Coal, Natural Gas, Nuclear, and Hydro Resources examined the combined hydrogen production potential from those energy sources, building on a previous study that examined the potential from renewable wind, solar, and biomass. The study found that total US production from coal, natural gas, hydro-electric, and nuclear power could be about 72.5 million metric tonnes per year, or enough to power about 35 million homes, if 30% of the current annual production capacity from those resources were devoted to hydrogen production (Milbrandt and Mann, 2009). This would be enough hydrogen to displace 80% of the 396 million tonnes of gasoline used in the US in 2007 (Milbrandt and Mann, 2009). The previous 2007 study titled Potential for Hydrogen Production from Key Renewable Resources in the United States, that focused on wind, solar, and biomass, found that the total production potential in the US from these renewable resources would be about 1 billion tonnes per year, or more than 10 times the potential from the other (coal, natural gas, hydro-electric, and nuclear) resources (Milbrandt and Mann, 2007). Thus, the hydrogen resource potential in the US is large, but the challenge is to tap economically into that resource to deliver clean, end-use energy for buildings and vehicles. The region of the country with the highest renewable hydrogen production potential (the Midwest/Great Plains) is not close to the largest population centers on the East and West Coasts. This implies considerable need for hydrogen transport and delivery infrastructure. A key point related to hydrogen for energy production is that it is a substance that is not found like crude oil or natural gas, but rather made like electricity from one of many different means. As with electricity, the environmental impacts of hydrogen use vary significantly by production method and its accompanying value or fuel chain. This paper reviews several of these hydrogen production methods and then considers a few recent case studies of hydrogen production using renewables. A range of potential hydrogen production methods and pathways is presented below in Figure 3. There are various emerging additional pathways also possible, but these are mostly at the laboratory scale at present and not the focus of this review. 6 Figure 3: Example Hydrogen Production Pathways (Source: EIA, 2008) For a literature review of the environmental impacts of hydrogen produced from various means, and more details about some of these fuel pathways, see National Academy of Engineering and Sciences (2004), Lipman (2005), and US DOE (2010). A recent US DOE review of hydrogen production methods explores several of these as well as some of the more longer term hydrogen production methods such as photo-electrochemical and high temperature thermochemical. 7 Also, for further details on the environmental impacts of hydrogen production for vehicle applications for various production methods and stages (feedstock production/delivery, fuel production, fuel delivery, and fuel end-use), the Argonne National Laboratory Greenhouse Gases, Regulated Emission, and Energy Use in Transportation (GREET) model is available to registered users through the model s website. It is an Excel spreadsheet model with a graphicaluser interface that runs in the PC/Windows environment. 8 6 For more on emerging hydrogen production technologies and systems, a good source of information is the 7 See: 8 See: The Current Hydrogen Market The current merchant and captive use hydrogen market is, as noted above, dominated by uses for oil refining, food production, metals treatment, and fertilizer manufacture. Power production uses relatively little of the hydrogen, perhaps on the order of million kilograms per year in the US, or about 0.1% of the total. This figure is based on an estimate by FuelCell Energy (FCE) that their fuel cell systems produced over 400 million kwh of electricity through 2009, using about 30 million kilograms of hydrogen over the past several years (Fuel Cell Energy, 2011). The FCE systems represent a significant part of the fuel cell market -- approximately 1/3 to 1/2 of the total installed base in the country (Adamson, 2008). For purposes of understanding the hydrogen market, it is useful to distinguish between captive hydrogen production (where the hydrogen is produced and used onsite, such as at oil refineries) and merchant hydrogen where the hydrogen is produced for delivery to other locations as an industrial gas. Further, a distinction can be drawn between on-purpose hydrogen, where hydrogen production is the main goal, and by-product hydrogen, where hydrogen is produced as a by-product from another process (e.g., chlor-alkali production). As shown in Table 1, on-purpose captive hydrogen production at oil refineries accounts for about 25% of total US production (2.7 million tonnes per year). Production for ammonia represents about 21% of total US production (2.3 million tonnes per year), and a small amount of captive production is used for methanol production and other uses. On-purpose merchant hydrogen production was about 1.6 million tonnes in 2006, or about 15% of the US total. Finally, by-product hydrogen production amounted to about 3.8 million tonnes in 2006, or nearly 36% of total US production. Most of this by-product hydrogen was from catalytic reforming at oil refineries and from chlor-alkali production (EIA, 2008). Table 1: Overview of US Hydrogen Production Capacity (Source: EIA, 2008) As shown in Figure 4, the demand for hydrogen in oil refineries is growing in order to satisfy the increasing demand for vehicle fuels and tightening environmental regulations. Since 1982, refinery hydrogen plant capacity has increased by 59%, or by about 1.2% per year. Overall, hydrogen production capacity in the US has been growing by about 7-10% per year (EIA, 2008). Figure 4: United States Refinery Onsite Hydrogen Production Capacity (million cubic feet and million kilograms of hydrogen per day) Source: EIA, 2008 Hydrogen Pipelines As of 2006, there were approximately 1,213 miles of hydrogen pipeline in the US, as reported by the US Energy Information Administration (EIA, 2008). Most of these pipelines are in Texas (847 miles), Louisiana (290 miles), Alabama (31 miles), Indiana (15 miles), and California (13 miles). Virtually all (an estimated 99%) of the transportation of hydrogen in the US is by pipeline as a compressed gas (typically at pressures below 1,000 psi), mainly for oil refinery use and ammonia production. Hydrogen transmission by pipeline dates back to the 1930 s in the U.S., and has had a good safety record (EIA, 2008). As an example, a hydrogen pipeline in California connects Carson and nearby Wilmington, associated with oil refineries in the area, as shown in Figure 5. The existing pipeline was installed by Air Products and Chemicals, Inc. to connect various refineries and to balance their capacities and needs for hydrogen for hydro-treating crude oil as part of the gasoline production process. Figure 5: Los Angeles Area Hydrogen Pipeline Source: Air Products and Chemicals, Inc. (undated) Several new or extended pipelines are being contemplated by various groups, including a proposal by Air Product and Chemicals Inc. to build a 180-mile long segment to connect its pipeline networks in Texas and Louisiana. This would create the world s largest network with the ability to supply over one billion cubic feet of hydrogen per day by the middle of 2012 (Air Products and Chemicals, Inc., 2010). Among the other hydrogen pipelines being contemplated is one between Chevron s refinery in Richmond, California and a group of refineries in nearby Martinez. This pipeline would be approximately 20 miles long and would provide opportunities for additional uses of the hydrogen along the pipeline alignment path. However, the project has not yet been fully approved and permitted as of April Hydrogen Production Methods Hydrogen in molecular form can be produced from many different sources, and in many different ways. In the context of energy systems, hydrogen is best thought of as an energy carrier, more akin to electricity than the fossil fuels that we extract from the earth s crust. Hydrogen can be produced from any hydrocarbon fuel because by definition these fuels contain hydrogen. Hydrogen can also be produced from various biological materials and from water. The water-splitting process is called electrolysis, and it is the oldest known electrochemical process. Hydrogen is most typically produced today through the steam reformation of natural gas, but also is produced through electrolysis and as a by-product of some industrial processes such as chlor-alkali production. Steam Methane Reforming Steam methane reforming (SMR) is the process by which natural gas or other methane stream, such as biogas or landfill gas, is reacted with steam in the presence of a catalyst to produce hydrogen and carbon dioxide. When starting with natural gas, SMR is approximately 72% efficient in producing hydrogen on a lower heating value basis (U.S. DOE, 2010). The efficiency can be somewhat lower with sources of methane that include sulfur or other impurities that require a pre-treatment cleanup step to remove the impurities upstream of the SMR process. SMR produces a hydrogen rich gas that is typically on the order of 70-75% hydrogen on a dry mass basis, along with smaller amounts of methane (2-6%), carbon monoxide (7-10%), and carbon dioxide (6-14%) (Hirschenhofer et al., 2000). Costs of hydrogen from SMR vary with feedstock cost, scale of production, and other variables and range from about $2-5 per kilogram at present (delivered and stored at high pressure) (NAS/NAE, 2004). Delivered costs as low as about $1.60 per kilogram are believed to be possible in the future based on large centralized production and pipeline delivery, and delivered costs for small-scale decentralized production are projected to be on the order of $ per kilogram (EIA, 2008; NAS/NAE, 2004). Gasification of Coal and Other Hydrocarbons In the partial oxidation (POX) process, also known more generally as gasification, hydrogen can be produced from a range of hydrocarbon fuels, including coal, heavy residual oils, and other low-value refinery products. The hydrocarbon fuel is reacted with oxygen in a less than stoichiometric ratio, yielding a mixture of carbon monoxide and hydrogen at 1200 to 1350 C. Hydrogen can be produced from coal gasification at delivered costs of about $ per kilogram at present at large scale, with delivered costs as low as about $1.50 per
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