Department Of Energy Goals Research Articles

Powering the Future: Progress and Hurdles in Developing Proton Exchange Membrane Fuel Cell Components to Achieve Department of Energy Goals—A Systematic Review

This comprehensive review explores recent developments in Proton Exchange Membrane Fuel Cells (PEMFCs) and evaluates their alignment with the ambitious targets established by the U.S. Department of Energy (DOE). Notable advancements have been made in developing catalysts, membrane technology advancements, gas diffusion layers (GDLs), and enhancements in bipolar plates. Notable findings include using carbon nanotubes and graphene oxide in membranes, leading to substantial performance enhancements. Innovative coatings and materials for bipolar plates have demonstrated improved corrosion resistance and reduced interfacial contact resistance, approaching DOE targets. Nevertheless, the persistent trade-off between durability and cost remains a formidable challenge. Extending fuel cell lifetimes to DOE standards often necessitates higher catalyst loadings, conflicting with cost reduction objectives. Despite substantial advancements, the ultimate DOE goals of USD 30/kW for fuel cell electric vehicles (FCEVs) and USD 600,000 for fuel cell electric buses (FCEBs) remain elusive. This review underscores the necessity for continuous research and innovation, emphasizing the importance of collaborative efforts among academia, industry, and government agencies to overcome the remaining technical barriers.

Understanding Fuel-Cell Impedance Spectra Via Numerical Modeling: A Single-Phase Water-Management Study

Cost of hydrogen-fueled proton-exchange-membrane fuel cells (PEMFCs) remains a challenge for the global commercialization of the technology and needs to be reduced to meet the U.S. Department of Energy goals [1]. Cost-reduction can be achieved by incorporating efficient water management, which helps keep the electrolyte hydrated while avoiding cell flooding by product water.Dynamic liquid-water accumulation and electrolyte hydration can be studied via transient polarization [2-6] and ohmic-resistance [2,4-7] curves, in which they induce hysteresis. Analyzing the polarization and resistance data may, however, be challenging due to the overlapping transients of various physical processes occurring in the cell during the voltage and current sweeps. Electrochemical impedance spectroscopy (EIS) allows the study of the dynamic processes of different time scales separately in the frequency domain and has been widely used for fuel-cell characterization [8-11].Fuel-cell impedance spectra often exhibit an inductive behavior at low frequencies, which has been shown to be affected by electrolyte hydration [10,12-14]. A recent experimental study [9] showed that the strength of this inductive behavior depends on the anode and cathode RH. Understanding the low-frequency inductance may help improve the water-management strategies for fuel cells. However, this inductive phenomenon has not been investigated in detail with a comprehensive numerical model.In this work, a transient 2D PEMFC model is developed in the open-source fuel-cell modeling software OpenFCST [17] with a thorough validation through dynamic polarization, resistance, and impedance-spectroscopy data at various operating conditions. Unlike other physical EIS models [13-16], the presented model does not rely on parameter fitting to reproduce the experimental impedance spectra. The model also takes the finite-rate water absorption/desorption kinetics of the electrolyte into account, which allows to investigate the effect of the interfacial transport of water on fuel-cell impedance and performance. With the presented model, water-management signatures are identified in fuel-cell impedance spectra under single-phase conditions that help elucidate electrolyte-hydration dynamics. The trends in the simulated effect of anode and cathode RH on the fuel-cell inductance are in agreement with experiments in [9], which verifies the model’s ability to correctly predict the inductive behavior. The low-frequency inductive behavior of fuel cells is shown to be related to the interfacial transport of water in the electrolyte and linked to the electrolyte-hydration and proton-conductivity dynamics in the membrane and in the catalyst layers. Additionally, an ohmic-resistance breakdown is performed with the model using the ohmic-heating-based approach proposed by Secanell et al. [18]. The high-frequency resistance obtained through EIS is shown to be comprised of the membrane resistance and the electronic resistance of other MEA components, but not the protonic resistance of the catalyst layers.Figure: Single-phase water-transport signatures in a fuel-cell-impedance spectrum.

Physical Properties Needed to Enable Extreme Fast Charging of High Energy Density Graphite/NMC Cells

The U.S. Department of Energy (DOE) has acknowledged extreme fast charging as one of the remaining challenges in enabling wide spread adoption of electric vehicles (EVs). The current DOE goal is to enable a 10-15 minute recharge time for high energy density cells with at least 200-250 Wh/kg. There are existing lithium-ion batteries that can be charged at very high rates (>5C), but these typically have prohibitively low energy density from use of thin electrodes and high cost. The charging time of EV type cells is limited by lithium plating, rapid temperature rise, and particle cracking. Through a combination of experimental data and Newman pseudo 2-D (P2D) modeling, this presentation will discuss physical properties needed to enable extreme fast charging of high energy density graphite/NMC 532 cells while avoiding lithium plating. The ANL team fabricated graphite/NMC 532 coin cells with loadings of 1.5, 2.7, 4.3 and 5 mAh/cm2 with similar electrode porosities and N/P ratio. The cells used standard “Generation 2” electrolyte consisting of 1.2 M LiPF6 in EC/EMC (3:7 by weight). After formation cycling, cells where charged at 6C with CC-CV protocol up to 4.1 V with a total charge time of 10 minutes at a temperature of 30 °C. At the lowest loading of 1.5 mAh/cm2, the cell achieved 90% SOC during 6C charging and almost all the capacity occurred during the CC portion. For this loading, cells could be 6C charged/C/2 discharged for 800 cycles and retain 70-80% of the initial capacity. However, at the higher loadings the achieved SOC during 6C charging rapidly fell off to less than 60% SOC and most of the capacity occurred during the CV portion. Further, the capacity fade is dramatically higher for thicker cells during continued 6C/C/2 cycling. For instance, cells with a loading of 4.3 and 5 mAh/cm2 capacity faded by 20% in only 5 cycles. A macro-homogeneous P2D model is used to investigate the poor 6C performance of thick-electrode cells and explore options from enabling 6C charging of high energy density cells. The model has been previously tuned to this chemistry under the DOE Computer-Aided Engineering for Electric-Drive Vehicle Batteries (CAEBAT) program. For loadings of 2.7, 4.3, and 5 mAh/cm2, the model predicts severe electrolyte depletion in the anode and saturation in the cathode are limiting high rate charging. The model and data seem to indicate solid-state diffusion and intercalation chemistry are sufficient to enable 6C charging. Based on this, the model is used to explore how the following might enable extreme fast charging of high energy density cells: Reducing electrode tortuosityImproving electrolyte propertiesIncreasing electrode porosityIncreasing charging temperatureIncreasing N/P ratio A combination of increased temperature, reduced electrode tortuosity, and improved electrolyte properties should enable 6C charging for cells with a loading of 4 mAh/cm2 and high energy density. Figure 1

Transient Testing of Nuclear Fuels and Materials in the United States

The United States has established that transient irradiation testing is needed to support advanced light water reactors fuel development. The U.S. Department of Energy (DOE) has initiated an effort to reestablish this capability. Restart of the Transient Testing Reactor (TREAT) facility located at the Idaho National Laboratory (INL) is being considered for this purpose. This effort would also include the development of specialized test vehicles to support stagnant capsule and flowing loop tests as well as the enhancement of postirradiation examination capabilities and remote device assembly capabilities at the Hot Fuel Examination Facility. It is anticipated that the capability will be available to support testing by 2018, as required to meet the DOE goals for the development of accident-tolerant LWR fuel designs.

Influence of quantum effects on the physisorption of molecular hydrogen in model carbon foams

The physisorption of molecular hydrogen in model carbon foams has been investigated from 50 K to room temperature. The study is carried out within the framework of the density functional theory for quantum liquids at finite temperatures. Calculations are performed in the grand canonical ensemble, i.e., the adsorbed fluid is assumed to be in equilibrium with an external gas of hydrogen molecules with concentrations ranging from 8×10(-4) kg m(-3) to n=71 kg m(-3). It is shown that, while strong zero-point energy effects are present even at room temperature, the adsorption isotherms exhibit only a weak dependence on the explicit incorporation of the bosonic exchange symmetry of hydrogen molecules. The increase of the average particle density prevents the deviations from the Maxwell-Boltzmann statistics to become noticeable if the system is cooled down. The volumetric storage capacity of these materials at low temperatures is about one half of the U. S. Department of Energy goal, while the gravimetric capacity is still far from the standards required by mobile applications. The relation between the microscopic structure of the hydrogen fluid and the calculated adsorption properties is also addressed.

Strategies for Enhancing the Effectiveness of Metagenomic-based Enzyme Discovery in Lignocellulolytic Microbial Communities

Producing cellulosic biofuels from plant material has recently emerged as a key US Department of Energy goal. For this technology to be commercially viable on a large scale, it is critical to make production cost efficient by streamlining both the deconstruction of lignocellulosic biomass and fuel production. Many natural ecosystems efficiently degrade lignocellulosic biomass and harbor enzymes that, when identified, could be used to increase the efficiency of commercial biomass deconstruction. However, ecosystems most likely to yield relevant enzymes, such as tropical rain forest soil in Puerto Rico, are often too complex for enzyme discovery using current metagenomic sequencing technologies. One potential strategy to overcome this problem is to selectively cultivate the microbial communities from these complex ecosystems on biomass under defined conditions, generating less complex biomass-degrading microbial populations. To test this premise, we cultivated microbes from Puerto Rican soil or green waste compost under precisely defined conditions in the presence dried ground switchgrass (Panicum virgatum L.) or lignin, respectively, as the sole carbon source. Phylogenetic profiling of the two feedstock-adapted communities using SSU rRNA gene amplicon pyrosequencing or phylogenetic microarray analysis revealed that the adapted communities were significantly simplified compared to the natural communities from which they were derived. Several members of the lignin-adapted and switchgrass-adapted consortia are related to organisms previously characterized as biomass degraders, while others were from less well-characterized phyla. The decrease in complexity of these communities make them good candidates for metagenomic sequencing and will likely enable the reconstruction of a greater number of full-length genes, leading to the discovery of novel lignocellulose-degrading enzymes adapted to feedstocks and conditions of interest.

The impact of injection on seismicity at The Geysers, California Geothermal Field

Water injection into geothermal systems has often become a required strategy to extend and sustain production of geothermal resources. To reduce a trend of declining pressures and increasing non-condensable gas concentrations in steam produced from The Geysers, operators have been injecting steam condensate, local rain and stream waters, and most recently treated wastewater piped to the field from neighboring communities. If geothermal energy is to provide a significant increase in energy in the United States (the US Department of Energy goal is 40,000 MW by 2040), injection must play a larger role in the overall strategy, i.e., enhanced geothermal systems (EGS). Presented in this paper are the results of monitoring microseismicity during an increase in injection at The Geysers field in California using data from a high-density digital microearthquake array. Although seismicity has increased due to increased injection, it has been found to be somewhat predictable, thus implying that intelligent injection control may be able to control large increases in seismicity.

Design and Optimization of a Natural Graphite/Iron Phosphate Lithium-Ion Cell

This paper uses a model for a natural graphite/lithium hexafluoro phosphate (ethylene carbonate:diethyl carbonate)/iron phosphate lithium-ion cell in order to study its performance and aid in its optimization. The model is used to generate Ragone plots for various designs, where both the average power of the cell and the peak power, defined at 80% depth-of-discharge for a 30 s pulse, are evaluated. This allows us to assess the ability of this chemistry to achieve the U.S. Department of Energy goals. The model is then used to maximize the specific energy of the cell by optimizing the design for a fixed time of discharge. The cell was optimized for the porosity and thickness of the positive electrode, while holding constant the capacity ratio of the two electrodes, the thickness and porosity of the separator, the electrolyte concentration, and the porosity of the negative electrode. The effect of the capacity ratio was qualitatively examined. The optimization was performed for discharge times ranging from 10 h to 2 min in order to map the maximum performance of this chemistry under a wide operating range. The study allows us to gauge the ability of this chemistry to be used in a particular application. The optimized designs derived in this paper are expected to be a starting point for battery manufacturers and to help decrease the time to commercialization. © 2004 The Electrochemical Society. All rights reserved.

Independent Task Force Urges New R&D Goals For Department of Energy

The Department of Energy, probably the unwieldiest of all the Cabinet departments, has been given yet another road map for its energy research and development program. Numerous past studies have examined various aspects of the department's R&D programs. A new report, the first to take a truly comprehensive look at them, is called R&D: Shaping Our Nation's Future in a Competitive World. It was produced by a task force chaired by one of the foremost experts on energy policy, Daniel Yergin, president of Cambridge Energy Research Associates in Cambridge, Mass. The task force was cochaired by Maxine Savitz, general manager of AlliedSignal Ceramic Components, and Mason Willrich, a former law professor and industrial manager who is now a private energy consultant. The 13 other panel members come from various energy-related companies and university departments. The report comes at a time of immense ferment for a department whose current mission bears little resemblance to ...