Energy Efficiency And Renewable Energy Research Articles

An Innovative Carbonate Fuel Cell Matrix

Introduction The electrolyte matrix is a microporous ceramic structure sandwiched between the electrodes to isolate the fuel from the oxidant, store electrolyte and facilitate ionic transport. The electrolyte distribution and fill levels in carbonate fuel cell are controlled by the balance in capillary forces of the porous cell components. The matrix needs to remain completely filled; therefore, pores are required to be fine and significantly smaller than the electrodes to exert sufficient capillary force to prevent electrolyte from moving to the electrodes at all times during endurance operation. A balanced pore structure between matrix and electrodes is necessary to avoid electrodes flooding and gas cross-over and to maintain stable cell resistance (1). FCE has advanced direct fuel cell (DFC) electrolyte matrix over the years and demonstrated that the matrix meets the requirements for greater than 5 year life based on accelerated tests and field stack operations. However, development of advanced designs and materials that can further increase the performance and extend cell life will enable accelerated MCFC deployment. This paper will report the progress on the development of an unique and innovative matrix design that offers numerous benefits to the carbonate fuel cell performance and durability. In addition, this paper will also review parameters that affect matrix material stability and approaches to extend cell life. Experimental Experiments were performed with button and single cells (3 cm2 and 250 cm2, respectively). Each cell consisted of a porous Ni-alloyed anode, a porous in-situ lithiated NiO cathode and a porous matrix (LiAlO2) filled with the carbonate electrolyte. Tests were performed at different temperatures under standard fuel (72.8%H2-18.2%CO2-9%H2O) and oxidant (18%CO2-12%CO2-67%N2-3%H2O) conditions. Other specially designed out of cell tests (OCT) were also performed at different temperatures and gas atmospheres to investigate parameters and processes affecting matrix material stability. Different techniques such as XRD, SEM, Mercury porosimetry, AC-impedance and steady-state polarization were carried out to evaluate and characterize matrix stability under fuel cell operating conditions. Results and Discussion The carbonate fuel cell matrix stability holds an important key to maintain higher electrolyte capacity and longer service life. The matrix particles (LiAlO2) stability is mainly controlled by the material purity, particles uniformity, temperature and electrolyte composition. Literature studies and accelerated tests showed localized matrix particles coarsening during long-term use. Such coarsening may lower capillary force, leading to an increase in cell ohmic resistance and gas crossover. FCE has made a substantial improvement in the matrix structure and the mechanical strength to enhance electrolyte storage capacity and extend cell life. Figure 1 shows a comparison of the snap strength of the advanced and the conventional matrix designs. Results showed that the advanced matrix offers >40% improvement in mechanical strength and more than 20% reduction of large pores at (0.2µm). These improvements are projected to enable low electrolyte loss from the fuel cell matrix and extend cell life. This paper reports the requirements, approaches and progress in achieving a higher performance and longer life carbonate fuel cell matrix. Acknowledgement The advanced matrix research is funded by the Office of Energy Efficiency and Renewable Energy (EERE), U.S. Department of Energy, under Award Number DE-EE0006606 1. C. Yuh, A. Franco, L. Chen, A. Hilmi, R. Venkataraman and M. Farooque., “Liquid-Electrolyte Fuel Cells Electrolyte Management Progress,” 192, Fuel Cell Seminar and Energy Exposition, November 10-13, 2014, Los Angeles, CA. Figure 1

Semantic catalog of things, services, and data to support a wind data management facility

Transparency and data integrity are crucial to any scientific study wanting to garner impact and credibility in the scientific community. The purpose of this paper is to discuss how this can be achieved using what we define as the Semantic Catalog. The catalog exploits community vocabularies as well as linked open data best practices to seamlessly describe and link things, data, and off-the-shelf (OTS) services to support scientific offshore wind energy research for the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy (EERE) Wind and Water Power Program. This is largely made possible by leveraging collaborative advances in the Internet of Things (IoT), Semantic Web, Linked Services, Linked Open Data (LOD), and Resource Description Framework (RDF) vocabulary communities, which provides the foundation for our design. By adapting these linked community best practices, we designed a wind characterization Data Management Facility (DMF) capable of continuous data collection, processing, and preservation of in situ and remote sensing instrument measurements. The design incorporates the aforementioned Semantic Catalog which provides a transparent and ubiquitous interface for its user community to the things, data, and services for which the DMF is composed.

Invited: Engineering Net Water Balance in Polymer Electrolyte Fuel Cells

The motivation of this work is to understand and control the water balance of a polymer electrolyte fuel cell to reduce anode water buildup and degradation. A custom 4.8 cm2 fuel cell with precision liquid coolant control was used to acquire the water balance data. The precision liquid coolant ensures stable, high accuracy thermal boundary conditions for the analysis. The net water drag coefficient was measured by placing high accuracy dew point temperature sensors at the inlets and outlets of the fuel cell to measure water balance. Gradients in pressure, inlet relative humidity, and temperature were used to isolate hydraulic, diffusion, and temperature driven flow through the membrane and porous media.This presentation will focus on the effects of anode land width, channel shape, and diffusion media tortuosity on net water drag. Using neutron radiography data that has been previously presented (1, 2) coupled with net water drag data, conclusions will be presented relating performance and water transport and storage. Data from this work will build upon an online database of benchmark data for the modeling community made available through this Department of Energy EERE supported program. Acknowledgements This work is funded by the United States Department of Energy Efficiency and Renewable Energy (EREE) Program through General Motors under Award Number DE-EE0000470.1. J. M. LaManna, S. Chakraborty, J. J. Gagliardo and M. M. Mench, International Journal of Hydrogen Energy, 39, 3387 (2014).2. J. LaManna and M. Mench, Meeting s, MA2014-01, 646 (2014).

Cost Reduction Strategies for Lithium Ion Electrode Processing and Pouch Cell Formation Steps

For lithium ion batteries (LIBs) to take their place in widespread commercialization of hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and full electric vehicles (EVs), system cost must still be reduced by 2-3× to about $200 kWh. [1] Two important ways to achieve significant system cost reduction are to: 1) lower the electrode processing cost (elimination of costly organic solvents, increasing the cathode thickness, and reduction of primary solvent drying time); and 2) reduce the formation time associated with the anode solid electrolyte interface (SEI) layer.Purchasing and handling the N-methylpyrrolidone (NMP) solvent used in much of the electrode formulation and coating steps add unnecessary manufacturing cost to the LIB pack. In addition, more processing energy (heated air flow) is required to remove NMP during drying of the electrode coatings than other solvents (such as water and lower alcohols) with much lower boiling points and higher vapor pressures. NMP recovery involves significant capital expense since multiple condensers or distillation towers are needed, and its use adds to the cost of the coating line equipment in making it explosion proof. Cathode thicknesses, which currently limit the cell specific capacity (mAh/g on a total-unit-cell weight basis) and energy density and indirectly add to cell cost, should also be significantly increased, so much fewer inactive components (current collectors and separators) are required per cell.Electrode wetting and formation cycling also add significant process energy cost per kWh of usable energy, which is often neglected in LIB pack cost calculations. Furthermore, the wetting and formation steps are a huge process time bottleneck and add substantial capital cost to a LIB production plant. In a large-scale LIB manufacturing plant, the footprint associated with the wetting and formation steps can be as large as 20-25% of the entire layout.There have been two useful LIB cost studies presented recently by Argonne National Laboratory (ANL) [2] and TIAX, LLC, [3] but these studies consider the entire 18650 cell production process without much granularity on individual processing and fabrication steps. These cost models are also heavy on contributions from material, labor, and capital equipment without detailed consideration of process energy requirements. This paper will give a more in depth review of the process energy consumption associated with electrode processing and formation cycling, two particularly costly elements of lithium-ion cell production, and how manufacturing cost savings could be realized.The cell fabrication steps mentioned above contribute significantly to the current overall pack cost of $400-600/kWh and will be the focus of the calculations in this presentation. Formulation, coating, and drying aspects will be considered with respect to electrode processing cost, and wetting time and low-rate cycling will be addressed with respect to total cell formation time. This cost assessment approach will show the critical link between electrode processing aides, process energy consumption, and LIB pack cost. Initial calculations show that about 20% of the total battery pack cost can be saved by switching to aqueous electrode processing and doubling the electrode thicknesses. Acknowledgment This research at Oak Ridge National Laboratory (ORNL), managed by UT Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725, was sponsored by the Office of Energy Efficiency and Renewable Energy (EERE) Vehicle Technologies Office (VTO) Applied Battery Research (ABR) subprogram (Program Managers: Peter Faguy and David Howell).

Current State of Understanding of the Solid-Electrolyte Interphase (SEI) in Lithium-Ion Cells and Its Relationship to Formation Cycling

The process of formation cycling refers to the electrochemical side reactions involved with creating a “passive” film on the anode active material, for instance graphite, known as the solid electrolyte interface (SEI) layer. This interfacial layer is formed during the first several charge-discharge cycles primarily by the reaction of electrolyte components with graphite at reducing potentials near the equilibrium potential of lithium metal (-3.045 V vs. SHE), and it plays a protective role by preventing the graphite from undergoing subsequent reaction with the electrolyte solvent and salt. [1] An ideal SEI layer should be thin, electrochemically inert, electronically conductive, and conductive to lithium ions. The commonly accepted hypothesis of the structure and composition of the SEI layer is an inner (interface with the graphite surface) inorganic layer of compounds such as LiF, Li2CO3, LiOH, LiO2, etc. and an outer (interface with the electrolyte solvent) organic layer primarily consisting of alkyl carbonates such as lithium ethylene dicarbonate (LiEDC). However, obtaining direct experimental evidence of SEI-layer composition and structure is extremely challenging. Information about thicknesses, constituent mass fractions, crystallinity, reactivity, and how these characteristics change from early cell life through thousands of charge-discharge cycles has remained elusive. Formation cycling is performed immediately after a lithium ion cell has been constructed and filled with electrolyte, and it has a profound economic impact on lithium ion battery manufacturing. The formation process requires that battery producers install many cycling stations to complete the process, which results in a heavy capital equipment investment and a much larger plant size. The irreversible capacity loss associated with anode SEI formation involves the consumption of lithium from the fresh cathode, resulting in a diminished battery lifetime. The formation process occurs in two successive stages, with the first stage involving formation of a highly resistive SEI layer at higher anode potentials (>0.25 V vs. Li/Li+). The second stage involves simultaneous intercalation of lithium into the graphite at potentials <0.25 V vs. Li/Li+ where the SEI layer is converted to a highly conductive film. [2] Fong et al. showed that the second stage involving the initial intercalation of lithium into graphite does not occur without the proper passivating electrolyte solvent and a sufficient coverage of SEI film. [3] There are three primary methods of formation cycling, which consist of a two-step current-charge formation, [4] pulse formation, [5] or the ageing process at elevated temperature. [6] In industry, combinations of these three approaches are often used. Electrode wettability plays a critical role in SEI layer formation. [7] After electrodes are coated and dried, they are usually calendered at high pressure to compact the composite structure, thus improving the energy density of the electrode layer. However, the electrode porosity is correspondingly reduced to only 30-35%, which has a significant impact on the pore-size distribution and the related wetting of the electrolyte.8 Wettability of the electrolyte to the electrode pores can be enhanced in two ways: 1) by supplying an additive to the electrolyte to lower its composite surface tension; and 2) by increasing the composite surface energy of the electrode. There is evidence that both of these approaches are effective, but the latter will be the focus of this presentation, especially as it relates to the SEI layer formation chemistry, growth in early cell life, and degradation in aged cells. Acknowledgment This research at Oak Ridge National Laboratory (ORNL), managed by UT Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725, was sponsored by the Office of Energy Efficiency and Renewable Energy (EERE) Vehicle Technologies Office (VTO) Applied Battery Research (ABR) subprogram (Program Managers: Peter Faguy and David Howell).

Comparison of Water Transport Mechanisms Between Commercial and Experimental Virgin and Aged Diffusion Media Using High Resolution Neutron Radiography

The motivation of this work is to characterize water transport for a new high tortuosity anode diffusion media (DM) and to provide the modeling community with valuable benchmark validation data. The high resolution neutron images in this work were taken at the Neutron Imaging Facility at the National Institute of Standards and Technology (NIST) Center for Neutron Research. Tests were conducted with well-defined boundary conditions and publically available materials. Gradients in pressure, inlet relative humidity, and temperature were used to isolate hydraulic, diffusion, and temperature driven flow through the membrane and porous media.A custom designed 4.8 cm2fuel cell with liquid coolant for precise thermal boundary conditions was used to acquire the neutron images. Test conditions were selected to produce extreme gradients within the cell to push model prediction capabilities. The high resolution neutron images allow for the determination of through-plane water profiles and water transfer rates as a function of current density as shown in Figure 1. Additionally, real-time water balance and net water drag measurements were made with dew point sensors.This talk will discuss the differences in performance and water content of the experimental DM and baseline commercial DM presented previously, and attempt to draw conclusions relating the structural properties of the porous media and resulting performance and water transport and distribution. Additionally, partially degraded materials (e.g. electrodes used for hundreds of hours) will be compared to virgin materials to understand the impact of age and lifetime on water transport and performance. Data from this work will build upon an online database of benchmark data for the modeling community made available through this Department of Energy EREE supported program. Acknowledgements This work is funded by the United States Department of Energy Efficiency and Renewable Energy (EREE) Program through General Motors under Award Number DE-EE0000470. The authors would like to thank Dr. Dan Hussy and Dr. David Jacobson of NIST for their guidance.Figure 1: Liquid water profiles for all 1.5 A/cm2 test conditions for baseline DM (upper) and high tortuosity DM (lower). The high tortuosity DM significantly reduces anode water content for identical operating conditions to baseline.

ChemInform Abstract: Research Highlights from the U.S. Department of Energy′s Working Group on Photoelectrochemical Hydrogen Production

AbstractReview: 43 refs.

Hybrid and Electric Systems R&amp;D at DOE: Fiscal Year 2011-2012 Status

This paper presents an overview of the recent highlights and accomplishments, for fiscal years (FYs) 2011- 2012, by the hybrid and electric systems (HES) R&amp;D Team at the Vehicle Technologies Program (VTP) Office of the United States Department of Energy (DOE) Energy Efficiency and Renewable Energy (EERE) Office. There is significant U.S. commitment to HES R&amp;D and additional responsibilities were assigned under the American Recovery and Reinvestment Act (ARRA) of 2009, an economic stimulus package from the 111th United States Congress. DOE has supported the development of HES technologies, including advanced automotive energy storage technologies, power electronics and electric machines, and simulation and testing tools, over the long term. This support has involved leveraging resources and expertise from automobile manufacturers, battery, motor, and electronics developers, small businesses, national laboratories, and universities to address the technical barriers which prevent the market introduction of vehicles which would use those advanced technologies. The HES R&amp;D Team has had many significant accomplishments and continues to advance the state of the art for many technologies. This paper provides a discussion of the most recent highlights and a description of R&amp;D coordination efforts with other government agencies in associated areas.

Status of the U. S. Department Of Energy, Energy Efficiency and Renewable Energy's Fuel Cell Research and Development Efforts

The U.S. Department of Energy (DOE) Fuel Cell Technologies Program, in the Office of Energy Efficiency and Renewable Energy (EERE), seeks to enable the widespread commercialization of fuel cells, through applied research and development (R&D) to overcome technical barriers, as well as through efforts to reduce institutional and market barriers. In support of this goal, DOE funds a broad range of fuel cell R&D activities with emphasis on materials, fuel cell stack components, balance of plant (BOP) subsystems, and integrated fuel cell systems targeting lower cost and enhanced durability. Fuel cell system cost estimates for transportation applications have illustrated that catalysts and system BOP are major cost drivers at high-volume production. Membranes are a cost driver at lower production volumes. The DOE has supported research to develop improved fuel cell catalysts and membranes and characterize and optimize transport phenomena to improve membrane electrode assembly (MEA) and stack performance.

Research Highlights from the U.S. Department of Energy’s Working Group on Photoelectrochemical Hydrogen Production

ABSTRACTThe US Department of Energy (DOE) hydrogen production research and development portfolio focuses on low-cost, highly efficient and environmentally friendly production technologies based on diverse, domestic resources. Within the DOE, work on hydrogen production technologies integrates basic and applied research, as well as technology development and demonstration. The integration of basic and applied research is of particular importance in “transformational” production technologies, such as photoelectrochemical (PEC) hydrogen production, where scientific advances are needed for achieving the long-term DOE performance and cost targets. In the case of renewable hydrogen production via PEC solar water splitting, high solar-to-hydrogen conversion efficiency has been demonstrated to date on the laboratory scale, but only with high-cost, low-durability material systems. In order to identify and develop the appropriate high-efficiency, low-cost, durable and scalable PEC material systems, research and development efforts in the DOE EERE (Energy Efficiency and Renewable Energy) Office have keyed in on specific focus areas, including: 1) the engineering of solar energy absorption properties in PEC semiconductor materials, such as the bandgap lowering in stable metal oxides as well as bandgap raising in nanostructured sulfide catalysts; 2) the engineering of PEC solid-liquid interfaces for optimal reaction rates and stability, such as surface nitrogenation in III-V semiconductor systems; 3) the standardization of PEC measurement and reporting methodologies, using national and international peer-review process, for facilitating research progress; and 4) the design and analysis of integrated PEC device and system configurations for scalable hydrogen production. As described in this presentation, all of these research and development areas rely heavily on collaborative efforts among academia, industry and national laboratory partners, utilizing state of the art resources in materials theory, synthesis, characterization and analysis. The collaboration extends nationally among research programs supported by the DOE EERE as well as Office of Science; and internationally via networking through the International Energy Agency’s Hydrogen Implementation Agreement Annex-26. Key and encouraging accomplishments resulting from the collaborative work are highlighted in this presentation.

The impact of DOE building technology energy efficiency programs on U.S. employment, income, and investment

The U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy (EERE) analyzes the macroeconomic impacts of its programs that are designed to increase the energy efficiency of the U.S. residential and commercial building stock. The analysis is conducted using the Impact of Sector Energy Technologies (ImSET) model, a special-purpose 188-sector input–output model of the U.S. economy designed specifically to evaluate the impacts of energy efficiency investments and saving. For the analysis described in the paper, ImSET was amended to provide estimates of sector-by-sector capital requirements and investment. In the scenario of the Fiscal Year (FY) 2005 Building Technologies (BT) program, the technologies and building practices being developed and promoted by the BT program have the potential to save about 2.9 × 10 15 Btu in buildings by the year 2030, about 27% of the expected growth in building energy consumption by the year 2030. The analysis reported in the paper finds that, by the year 2030, these savings have the potential to increase employment by up to 446,000 jobs, increase wage income by $7.8 billion, reduce needs for capital stock in the energy sector and closely related supporting industries by about $207 billion (and the corresponding annual level of investment by $13 billion), and create net capital savings that are available to grow the nation's future economy.

Analysis of long-range clean energy investment scenarios for Eritrea, East Africa

We discuss energy efficiency and renewable energy (EE/RE) investments in Eritrea from the strategic long-term economic perspective of meeting Eritrea's sustainable development goals and reducing greenhouse gas emissions. EE/RE are potentially important contributors to national productive capital accumulation, enhancement of the environment, expansion of energy services, increases in household standard of living, and improvements in health. In this study, we develop a spreadsheet model for calculating some of the national benefits and costs of different levels of investment in EE/RE. We then present the results of the model in terms of investment demand and investment scenario curves. These curves express the contribution that efficiency and renewable energy projects can make in terms of reduced energy sector operating expenses, and reduced carbon emissions. We provide demand and supply curves that show the rate of return, the cost of carbon emissions reductions vs. supply, and the evolution of the marginal carbon emissions per dollar of GDP for different investment levels and different fuel-type subsectors.

Biomass cofiring: the technology, the experience, the combustion consequences

Cofiring, the practice of supplementing a base fuel with a dissimilar fuel, is an extension of fuel blending practices common to the solid fuels community. Recently, there has been considerable emphasis on cofiring biomass opportunity fuels with coal in pulverized coal (PC) and cyclone boilers owned and operated by electricity generating utilities in order to address such issues as potential portfolio standards, voluntary actions to reduce fossil CO 2 emissions, customer service, and the generation of green power within the context of deregulation. Biomass fuels considered for cofiring include wood waste, short rotation woody crops, short rotation herbaceous crops (e.g., switchgrass), alfalfa stems, various types of manure, landfill gas and wastewater treatment gas. Of these, the solid biofuels such as sawdust, urban wood waste and switchgrass have received the most attention. The Electric Power Research Institute (EPRI), along with the Tennessee Valley Authority (TVA), GPU Genco, Northern Indiana Public Service Company (NIPSCO), Central and South West Utilities (C&SW), Southern Company, Madison Gas & Electric (MG&E), New York State Electric and Gas (NYSEG) and others developed a concerted effort to commercialize direct combustion cofiring of biomass with coal. The USDOE joined the program with a cooperative agreement between the Federal Energy Technology Center (FETC) — now the National Energy Technology Laboratory (NETL) and EPRI; this agreement was extensively supported by the energy efficiency and renewable energy (EERE) element of USDOE. European cofiring programs also have been extensive and include gasification-based cofiring in Lahti, Finland and straw cofiring in Denmark. Three general techniques comprise the cofiring technology family: blending the biomass and coal in the fuel handling system and feeding that blend to the boiler; preparing the biomass fuel separately from coal, and injecting it into the boiler without impacting the conventional coal delivery system; and gasifying the biomass with subsequent combustion of the producer gas in either a boiler or a combined cycle combustion turbine (CCCT) generating plant. Commercialization has proceeded on the direct combustion approaches to cofiring, beginning with engineering and economic studies, parametric testing and the construction of demonstration projects. The direct combustion cofiring techniques are now ready for commercial deployment. This paper reviews the key projects, and details some of the influences of cofiring on the combustion process.

Cofiring multiple opportunity fuels with coal at Bailly Generating Station

Northern Indiana Public Service Company (NIPSCO) has developed a long-term demonstration firing biomass and petroleum coke with coal at its Bailly Generating Station boiler #7, a 160 MW e (net) cyclone boiler. This demonstration, funded by the US Department of Energy (USDOE) Office of Energy Efficiency and Renewable Energy (EERE) and the USDOE National Energy Technology Laboratory (NETL), has been developed as part of the Electric Power Research Institute (EPRI) biomass cofiring demonstration program. The NIPSCO demonstration program — the triburn program — has involved designing and constructing a fuel preparation and blending facility. It then involved extensive testing of firing clean urban wood waste — biomass — with coal, firing petroleum coke with coal, and firing various blends of urban wood waste and petroleum coke with coal. Results of the extensive testing program have shown that the triburn blends of biomass and petroleum coke with coal have accomplished the following: (1) increased boiler efficiency, (2) reduced fuel costs; and (3) reduced emissions of oxides of nitrogen (NO x ), mercury, and fossil carbon dioxide (CO 2). At the same time, the triburn program has not increased other emissions. This paper summarizes the results of testing at Bailly Generating Station, discusses the impacts of petroleum coke and wood waste, discusses the synergies between these two opportunity fuels, and considers the implications of the demonstration.

Prolonged gestation: Energy efficiency and renewable energy businesses

AbstractLife cycle theories suggest that businesses evolve through a number of stages: from an embryonic stage of introduction to growth, maturity, and decline. The force that propels their development is consumer acceptance. Industries pass through life cycles as well. However, not all industries pass through each stage of the life cycle, and the duration of stages varies across industries. Some industries skip the slow introductory phase; others avoid the decline stage and are continually revitalised through technological innovation. Still others continue to show substantial promise, but fail to take‐off. It is this industry condition, persistent promise without corresponding growth, that we characterise as extended gestation. We believe that energy efficiency and renewable energy (EERE) businesses in Minnesota face the challenge of extended gestation. In this paper, we review the literature on the traditional stages of industry development, explore some of the factors that may lead an industry to remain in a state of extended gestation, and report the results of a study undertaken to better understand the factors that affect the growth of EERE businesses.