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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,009 records · Page 56
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Oxidation of SiC cladding under Loss of Coolant Accident (LOCA) conditions in LWRs

An experimental assessment of Silicon Carbide (SiC) cladding oxidation rate in steam under conditions representative of Loss of Coolant Accidents (LOCA) in light water reactors (LWRs) was conducted. SiC oxidation tests were performed with monolithic alpha phase tubular samples in a vertical quartz tube at a steam temperature of 1140 deg. C and steam velocity range of 1 to 10 m/sec, at atmospheric pressure. Linear weight loss of SiC samples due to boundary layer controlled reaction of silica scale (SiO{sub 2} volatilization) was experimentally observed. The weight loss rate increased with increasing steam flow rate. Over the range of test conditions, SiC oxidation rates were shown to be about 3 orders of magnitude lower than the oxidation rates of zircaloy 4. A SiC volatilization correlation for developing laminar flow in a vertical channel is formulated. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2021

Process Heat for Chemical Industry

Process heating with nuclear energy can reduce greenhouse gas emissions by reducing combustion of fossil fuels in fired heaters as steam boilers. Light water reactors can replace the majority of steam duties used by industry; however, high temperature processes such as steam methane reforming require advanced high temperature reactors. Here, guidance on matching the scale of nuclear reactors with specific industries is provided. Principles of heat transport, temperature boosting, and substitution for hot combustion gases are also discussed in this section.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2011

Conceptual Design of a 100 MWe Modular Molten Salt Power Tower Plant

A conceptual design of a 100 MWe modular molten salt solar power tower plant has been developed which can provide capacity factors in the range of 35 to 75%. Compared to single tower plants, the modular design provides a higher degree of flexibility in achieving the desired customer's capacity factor and is obtained simply by adjusting the number of standard modules. Each module consists of a standard size heliostat field and receiver system, hence reengineering and associated unacceptable performance uncertainties due to scaling are eliminated. The modular approach with multiple towers also improves plant availability. Heliostat field components, receivers and towers are shop assembled allowing for high quality and minimal field assembly. A centralized thermal-storage system stores hot salt from the receivers, allowing nearly continuous power production, independent of solar energy collection, and improved parity with the grid. A molten salt steam generator converts the stored thermal energy into steam, which powers a steam turbine generator to produce electricity. This paper describes the conceptual design of the plant, the advantages of modularity, expected performance, pathways to cost reductions, and environmental impact.

14 SOLAR ENERGY↗
DOE OSTI2023

A New Class of Proton Conductors with Dramatically Enhanced Stability and High Conductivity for Reversible Solid Oxide Cells

Reversible solid oxide cells based on proton conductors (P-ReSOCs) have potential to be the most efficient and low-cost option for large-scale energy storage and power generation, holding promise as an enabler for the implementation of intermittent renewable energy technologies and the widespread utilization of hydrogen. Here, the rational design of a new class of hexavalent Mo/W-doped proton-conducting electrolytes with excellent durability while maintaining high conductivity is reported. Specifically, BaMo(W) 0.03 Ce 0.71 Yb 0.26 O 3-δ exhibits dramatically enhanced chemical stability against high concentrations of steam and carbon dioxide than the state-of-the-art electrolyte materials while retaining similar ionic conductivity. In addition, P-ReSOCs based on BaW 0.03 Ce 0.71 Yb 0.26 O 3-δ demonstrate high peak power densities of 1.54, 1.03, 0.72, and 0.48 W cm –2 at 650, 600, 550, and 500 °C, respectively, in the fuel cell mode. During steam electrolysis, a high current density of 2.28 A cm –2 is achieved at a cell voltage of 1.3 V at 600 °C, and the electrolysis cell can operate stably with no noticeable degradation when exposed to high humidity of 30% H 2 O at –0.5 A cm –2 and 600 °C for over 300 h. Altogether, this work demonstrates the promise of donor doping for obtaining proton conductors with both high conductivity and chemical stability for P-ReSOCs.

25 ENERGY STORAGE↗
DOE OSTI2020

Build Orientation Dependent Microstructure in Polymer Laser Sintering: Relationship to Part Performance and Evolution with Aging

Laser sintering (LS) is widely used to produce functional polymeric parts; however, the resulting parts are often limited by their porous structure, and performance of the part may be strongly anisotropic. Relating the structural features of parts to build process conditions or powder feedstock has been explored previously. In contrast, little is known regarding how the unique internal structures of LS parts evolve and relate to their performance later in their life cycle, for example, after use in a real-world operating environment. In this study, a tightly controlled LS build process and measurement campaign by standard X-ray computed tomography (XCT), supported by high-resolution synchrotron XCT, was used to benchmark the internal microstructure (e.g. porosity) as a function of four different build orientations in printed polyamide-12 (PA-12) parts. The initial performance of the parts after printing was characterized by tensile testing and dynamic mechanical analysis (DMA). Arrays of PA-12 parts in different build orientations were exposed to steam (under pressure) and air across multiple temperature and time points for the purposes of accelerated aging through oxidative and hydrolytic breakdown. Exposing parts to steam dramatically altered the internal microstructure and functional properties such as the glass transition temperature, tensile properties, and damping behavior. Notably, post-aging XCT revealed large microstructural changes after only 40 h of steam treatment relative to the as-printed specimens. Furthermore, pore reorganization and changes in crystallinity occurred regardless of whether the steam temperature was aggressive enough to induce a significant loss in mechanical properties. The build orientation dependence on the aging rate was minimal with the relative trend in performance persisting across most metrics among the different orientations even after aging.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Pyroclast cooling and saturation in water

In the submarine setting pyroclast cooling and saturation, by controlling the buoyancy of individual clasts and surrounding fluid, exert fundamental controls on the dispersal and fate of volcanic material. Here, we use laboratory experiments to understand and quantify how hot and air-filled pyroclasts cool and saturate in liquid water. By measuring internal temperature and clast submerged weight in over thirty experiments, we find that pumice cools and saturates in two stages. We observe that the first stage is marked by much higher rates of cooling and saturation than the second stage and that the transition between stages is sharp. We propose conceptual and quantitative models for each stage of pyroclast cooling and saturation. Specifically we argue that the first stage is defined by the presence of internal steam. That is, hot pyroclasts ingest liquid water and generate steam. Once a clast's internal pore space is filled with steam, heat loss to the surroundings causes condensation of internal vapor and clast saturation. Stage 1 ends when all internal steam has condensed. We test this idea with a Stefan Model with advection and conclude that heat loss, rather than permeability, controls the saturation of pyroclasts above the boiling temperature. We find that permeability matters for air-filled clasts with initial temperatures below the boiling point. Stage 2 begins after all internal vapor has condensed and we propose that stage 2 cooling and saturation are controlled by heat conduction and thermal contraction of trapped gas, respectively. From our understanding of the processes that govern the stage 1 to 2 transition, we derive an empirical average pyroclast cooling rate of q = 7.5 ± 0.5 W cm -2 . Finally, we develop quantitative models for cooling-controlled porous clast saturation and for buoyant clast rise to the ocean surface. We find that meter size clasts stay buoyant for more than 10 min - long enough to reach the surface from a depth of 1000 m. Lastly, the models developed here test our understanding of clast-scale processes and demonstrate that - in hot and porous clasts - the details of internal texture do not matter because clast saturation, and thus buoyancy and fate in the water column, are governed by heat transfer.

58 GEOSCIENCES↗
DOE OSTI2016

Nonintrusive Uncertainty Quantification of Computational Fluid Dynamics Simulations of a Bench-Scale Fluidized-Bed Gasifier

Uncertainty quantification (UQ) analysis is increasingly becoming one of the major requirements of simulation-based engineering to assess the confidence in the results and make better-informed decisions based on the insight derived from the simulations. In an earlier study, Bayesian UQ analysis was applied to existing bench-scale fluidized-bed gasifier experiment results. In the current study, a series of simulations were carried over with the open-source computational fluid dynamics software MFiX to reproduce the experimental conditions, where three operating factors, i.e., coal flow rate, coal particle diameter, and steam-to-oxygen ratio, were systematically varied to understand their effect on the syngas composition. Bayesian UQ analysis was this time performed on the numerical results for comparison purposes. This is part of ongoing research efforts to explore the applicability of advanced UQ methods and processes such as Bayesian methods for large-scale complex multiphase flow simulations. As part of Bayesian UQ analysis, a global sensitivity analysis was performed based on the simulation results, which shows that the predicted syngas composition is strongly affected not only by the steam-to-oxygen ratio (which was observed in experiments as well) but also by variation in the coal flow rate and particle diameter (which was not observed in experiments). The carbon monoxide mole fraction is underpredicted at lower steam-to-oxygen ratios and overpredicted at higher steam-to-oxygen ratios. The opposite trend is observed for the carbon dioxide mole fraction. These discrepancies are attributed to either excessive segregation of the phases that leads to the fuel-rich or -lean regions or alternatively the selection of reaction models, where different reaction models and kinetics can lead to different syngas compositions throughout the gasifier.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2019

Treatment of Highly Saline Brines by Supercritical Precipitation Followed by Supercritical Membrane Separation

A two-stage supercritical (SC) desalination system is proposed to treat highly saline brines to high-purity steam that could be used in power generation. Highly saline brines with up to similar to 20% salt content are pressurized and heated to SC conditions of 500 degrees C and 3500 psi to rapidly precipitate the dissolved salts and generate SC steam containing similar to 100 ppm salts. Two highly saline brines, collected from an oil field and a deep saline formation, and two concentrated NaCl solutions were treated in the SC desalination system. A SC membrane separation system with carbon filters is developed and used to purify the SC steam to a high purity level. Promising carbon filters or membranes prepared and tested for purifying SC steam included a porous graphite disk, a flexible graphite sheet, and a carbon nanotube-based membrane. Finally, the best performing membranes exhibited a very high water flux of similar to 200-800 kg/m 2 .h, with a salt rejection of >90%.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Electrochemically Engineered, Highly Energy-Efficient Conversion of Ethane to Ethylene and Hydrogen below 550 °C in a Protonic Ceramic Electrochemical Cell

Ethylene is one of the largest building blocks in the petrochemical industry, mainly produced by steam cracking of ethane derived from naphtha or shale gas at high temperatures (>800 °C). Despite its technical maturity and economic competitiveness, the thermal steam cracking of ethane is highly energy-intensive. In this work, an electrochemically engineered direct conversion process of ethane to produce hydrogen and ethylene using a planar protonic ceramic membrane reactor with a bi-functional three-dimensional catalytic electrode is reported, with a single-pass ethane conversion of 40% and ethylene yield of 26.7% at 550 °C. Compared with the industrial ethane steam cracking, this method saves process energy input by 45.1% and improves process energy efficiency by 50.6%, based on comprehensive process simulation using Aspen Plus software. Further, steam electrolysis treatment under the solid oxide electrolysis cell mode can regenerate the system’s catalytic performance and significantly alleviate catalytic degradation by 74%, demonstrating high techno-economic viability.

bi-functional electrode↗
DOE OSTI2012

Rigorous Kinetic Modeling and Optimization Study of a Modified Claus Unit for an Integrated Gasification Combined Cycle (IGCC) Power Plant with CO{sub 2} Capture

The modified Claus process is one of the most common technologies for sulfur recovery from acid gas streams. Important design criteria for the Claus unit, when part of an Integrated Gasification Combined Cycle (IGCC) power plant, are the ability to destroy ammonia completely and the ability to recover sulfur thoroughly from a relatively low purity acid gas stream without sacrificing flame stability. Because of these criteria, modifications to the conventional process are often required, resulting in a modified Claus process. For the studies discussed here, these modifications include the use of a 95% pure oxygen stream as the oxidant, a split flow configuration, and the preheating of the feeds with the intermediate pressure steam generated in the waste heat boiler (WHB). In the future, for IGCC plants with CO{sub 2} capture, the Claus unit must satisfy emission standards without sacrificing the plant efficiency in the face of typical disturbances of an IGCC plant, such as rapid change in the feed flow rates due to load-following and wide changes in the feed composition because of changes in the coal feed to the gasifier. The Claus unit should be adequately designed and efficiently operated to satisfy these objectives. Even though the Claus process has been commercialized for decades, most papers concerned with the modeling of the Claus process treat the key reactions as equilibrium reactions. Such models are validated by manipulating the temperature approach to equilibrium for a set of steady-state operating data, but they are of limited use for dynamic studies. One of the objectives of this study is to develop a model that can be used for dynamic studies. In a Claus process, especially in the furnace and the WHB, many reactions may take place. In this work, a set of linearly independent reactions has been identified, and kinetic models of the furnace flame and anoxic zones, WHB, and catalytic reactors have been developed. To facilitate the modeling of the Claus furnace, a four-stage method was devised so as to determine which set of linearly independent reactions would best describe the product distributions from available plant data. Various approaches are taken to derive the kinetic rate expressions, which are either missing in the open literature or found to be inconsistent. A set of plant data is used for optimal estimation of the kinetic parameters. The final model agrees well with the published plant data. Using the developed kinetics models of the Claus reaction furnace, WHB, and catalytic stages, two optimization studies are carried out. The first study shows that there exists an optimal steam pressure generated in the WHB that balances hydrogen yield, oxygen demand, and power generation. In the second study, it is shown that an optimal H{sub 2}S/SO{sub 2} ratio exists that balances single-pass conversion, hydrogen yield, oxygen demand, and power generation. In addition, an operability study has been carried out to examine the operating envelope in which both the H{sub 2}S/SO{sub 2} ratio and the adiabatic flame temperature can be controlled in the face of disturbances typical for the operation of an IGCC power plant with CO{sub 2} capture. Impact of CO{sub 2} capture on the Claus process has also been discussed.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2013

Progress toward Biomass and Coal-Derived Syngas Warm Cleanup: Proof-of-Concept Process Demonstration of Multicontaminant Removal for Biomass Application

Systems comprising of multiple sorbent and catalytic beds have been developed for the warm syngas cleanup of coal- and biomass-derived syngas. Tailored specifically for biomass application the process described here consists of six primary unit operations: 1) Na2CO3 bed for HCl removal, 2) two regenerable ZnO beds for bulk H2S removal, 3) ZnO bed for H2S polishing, 4) NiCu/SBA-16 sorbent for trace metal (e.g. AsH3) removal, 5) steam reforming catalyst bed for tars and light hydrocarbons reformation and NH3 decomposition, and a 6) Cu-based LT-WGS catalyst bed. Simulated biomass-derived syngas containing a multitude of inorganic contaminants (H2S, AsH3, HCl, and NH3) and hydrocarbon additives (methane, ethylene, benzene, and naphthalene) was used to demonstrate process effectiveness. The efficiency of the process was demonstrated for a period of 175 hours, during which no signs of deactivation were observed. Post-run analysis revealed small levels of sulfur slipped through the sorbent bed train to the two downstream catalytic beds. Future improvements could be made to the trace metal polishing sorbent to ensure complete inorganic contaminant removal (to low ppb level) prior to the catalytic steps. However, dual, regenerating ZnO beds were effective for continuous removal for the vast majority of the sulfur present in the feed gas. The process was effective for complete AsH3 and HCl removal. The steam reforming catalyst completely reformed all the hydrocarbons present in the feed (methane, ethylene, benzene, and naphthalene) to additional syngas. However, post-run evaluation, under kinetically-controlled conditions, indicates deactivation of the steam reforming catalyst. Spent material characterization suggests this is attributed, in part, to coke formation, likely due to the presence of benzene and/or naphthalene in the feed. Future adaptation of this technology may require dual, regenerable steam reformers. The process and materials described in this report hold promise for a warm cleanup of a variety of contaminant species within warm syngas.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2019

Redox oxidative cracking of n -hexane with Fe-substituted barium hexaaluminates as redox catalysts

Light olefins such as ethylene and propylene are critical building blocks in the chemical industry and are currently produced mainly from steam cracking of naphtha. However, the highly endothermic nature of steam generation and the cracking reactions make this process highly energy- and CO 2 -intensive. Coke formation in the steam cracker tubes represents another obstacle. To address these challenges, we proposed a chemical looping approach to convert naphtha into olefins via a redox oxidative cracking (ROC) process. In the present work, Fe-substituted barium hexaaluminates (BaFe x Al 12– x O 19 ) were investigated as oxygen carriers, or redox catalysts, to convert n -hexane to olefins via ROC. The cyclic redox scheme facilitated by the Fe-substituted hexaaluminates allows autothermal operation and higher olefin yields relative to the endothermic steam-cracking process. While base BaFe x Al 12– x O 19 ( x = 1, 2, 3, 4, 6) oxides showed high CO x yields (8.4–55.2%) in ROC of n -hexane, 20 wt% Na 2 WO 4 promotion of BaFe 6 Al 6 O 19 (20-NaW/BaFe6) significantly inhibited CO x formation (0.6–1.2% CO x yield) while oxidizing all the H 2 produced during cracking within a temperature range of 600–700 °C and GHSV of 9000 h –1 . Benefiting from the donation of selective lattice oxygen, we report 20-NaW/BaFe6 more than doubled the olefin yield when compared to that from thermal cracking (26.0% vs. 12.8%). Moreover, decreasing the GHSV from 9000 h –1 to 2250 h –1 resulted in 8.5% increase in n -hexane conversion on an absolute basis, while maintaining nearly the same olefin selectivity. Long-term stability of the 20-NaW/BaFe6 oxygen carrier was also demonstrated within 30 cycles at 700 °C and 2250 h –1 , achieving an olefin yield in the range of 31.3–32.4% and low CO x yield of 0.6–0.7%. XPS analysis of cycled BaFe6 revealed a shift towards near-surface Ba enrichment upon redox cycling. In comparison, both as-prepared and cycled 20-NaW/BaFe6 showed suppression of near surface Ba content, indicating that Na 2 WO 4 inhibited the migration of Ba into the near-surface region during n -hexane ROC and effectively suppressed non-selective oxidation reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Proton surface exchange kinetics of perovskite triple conducting thin films for protonic ceramic electrolysis cells: BaPr 0.9 Y 0.1 O 3–δ (BPY) vs. Ba 1–x Co 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3–δ (BCFZY)

Protonic ceramic electrolysis cells (PCECs) are an attractive green H 2 production technology, given their intermediate-temperature operating range and ability to produce dry H 2 . However, PCECs will benefit from development of more efficient and durable “triple conducting” anodes where steam is split, H incorporated, and oxygen evolved. In this work, we evaluated the kinetics of the steam-splitting/H incorporation reaction on BaPr 0.9 Y 0.1 O 3–δ (BPY) in comparison to the benchmark Ba 1–x Co 0.4 Fe 0.4 Z r0.1 Y 0.1 O 3–δ (BCFZY) composition, replacing most of the transition metal elements (Co, Fe, Zr) with the lanthanide Pr. We prepared geometrically well-defined perovskite BPY and BCFZY thin films by pulsed laser deposition and performed simultaneous optical transmission relaxation and electrical conductivity relaxation measurements at 400–500 °C in 0.21 atm O 2 during switching of the steam partial pressure to isolate and compare their proton surface exchange coefficients (k). The k values of BPY were comparable to those of BCFZY and more stable over time. According to angle-resolved XPS and STEM-EDS mapping of FIB cross-sections, the surface of BPY exhibited Ba enrichment, Pr deficiency, and Si contamination. In contrast, BCFZY exhibited Ba deficiency throughout, no obvious surface segregation, and less Si contamination. The Ba segregation on the BPY film appears to have promoted steam splitting/H incorporation kinetics even though the more basic surface reacted with the acidic environmental SiO x H y . Faster kinetics observed on stoichiometric BCFZY vs. Ba-deficient BCFZY confirmed the benefit of a high A-site Ba concentration. This result contrasts with most work on perovskites applied in solid oxide electrolysis cell anodes, in which A-site segregation is considered deleterious for surface reaction kinetics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Competitiveness Assessment of Decarbonizing Electricity and Process Heat Supply to a Campus with a Small Nuclear Reactor

This paper analyzes the competitiveness of siting a small nuclear reactor to support decarbonization of sites requiring tens of MW of electricity and/or process heat to support centralized heating and cooling system. This paper focuses on campuses as representative of sites with collections of buildings and research facilities with decarbonization needs represented by buildings heating, and electricity consumption by electrical loads which may include cooling via chilled water (e.g., for air conditioning and to cool down computer clusters). A nuclear reactor can be considered to decarbonize a site’s high-temperature steam generation used mostly for building heating needs, climate control, and hot water, by supplying process heat capabilities, while electricity decarbonization would be achieved mostly by the grid. However, a secondary application can be considered to maximize reactor utilization and avoid ramping down the reactor if the steam demand varies significantly throughout the year. Chilled water generation through steam-driven systems was identified as an attractive secondary option for the site analyzed, due to potential for plant design simplification, while electricity generation could be considered as well to reduce electricity purchases for a wider range of site applications. For a campus with peak 60MW thermal power demand, a small nuclear reactor with similar thermal power rating would almost eliminate CO2 emissions from steam generation and reduce electricity imports for chilled water production. A preliminary techno-economic feasibility study shows that a small nuclear reactor design that is optimized to support process heat can represent an economically feasible option when compared with other decarbonization alternatives.

Stauff, Nicolas E.↗
DOE OSTI2013

Novel Molten Salts Thermal Energy Storage for Concentrating Solar Power Generation

The explicit UA program objective is to develop low melting point (LMP) molten salt thermal energy storage media with high thermal energy storage density for sensible heat storage systems. The novel Low Melting Point (LMP) molten salts are targeted to have the following characteristics: 1. Lower melting point (MP) compared to current salts (<222ºC) 2. Higher energy density compared to current salts (>300 MJ/m3) 3. Lower power generation cost compared to current salt In terms of lower power costs, the program target the DOE's Solar Energy Technologies Program year 2020 goal to create systems that have the potential to reduce the cost of Thermal Energy Storage (TES) to less than $15/kWh-th and achieve round trip efficiencies greater than 93%. The project has completed the experimental investigations to determine the thermo-physical, long term thermal stability properties of the LMP molten salts and also corrosion studies of stainless steel in the candidate LMP molten salts. Heat transfer and fluid dynamics modeling have been conducted to identify heat transfer geometry and relative costs for TES systems that would utilize the primary LMP molten salt candidates. The project also proposes heat transfer geometry with relevant modifications to suit the usage of our molten salts as thermal energy storage and heat transfer fluids. The essential properties of the down-selected novel LMP molten salts to be considered for thermal storage in solar energy applications were experimentally determined, including melting point, heat capacity, thermal stability, density, viscosity, thermal conductivity, vapor pressure, and corrosion resistance of SS 316. The thermodynamic modeling was conducted to determine potential high temperature stable molten salt mixtures that have thermal stability up to 1000 °C. The thermo-physical properties of select potential high temperature stable (HMP) molten salt mixtures were also experimentally determined. All the salt mixtures align with the go/no-go goals stipulated by the DOE for this project. Energy densities of all salt mixtures were higher than that of the current solar salt. The salt mixtures costs have been estimated and TES system costs for a 2 tank, direct approach have been estimated for each of these materials. All estimated costs are significantly below the baseline system that used solar salt. These lower melt point salts offer significantly higher energy density per volume than solar salt – and therefore attractively smaller inventory and equipment costs. Moreover, a new TES system geometry has been recommended A variety of approaches were evaluated to use the low melting point molten salt. Two novel changes are recommended that 1) use the salt as a HTF through the solar trough field, and 2) use the salt to not only create steam but also to preheat the condensed feedwater for Rankine cycle. The two changes enable the powerblock to operate at 500°C, rather than the current 400°C obtainable using oil as the HTF. Secondly, the use of salt to preheat the feedwater eliminates the need to extract steam from the low pressure turbine for that purpose. Together, these changes result in a dramatic 63% reduction required for 6 hour salt inventory, a 72% reduction in storage volume, and a 24% reduction in steam flow rate in the power block. Round trip efficiency for the Case 5 - 2 tank “direct” system is estimated at >97%, with only small losses from time under storage and heat exchange, and meeting RFP goals. This attractive efficiency is available because the major heat loss experienced in a 2 tank “indirect” system - losses by transferring the thermal energy from oil HTF to the salt storage material and back to oil to run the steam generator at night - is not present for the 2 tank direct system. The higher heat capacity values for both LMP and HMP systems enable larger storage capacities for concentrating solar power.

25 ENERGY STORAGE↗
DOE OSTI2014

Bench-Scale Silicone Process for Low-Cost CO 2 Capture (Final Scientific/Technical Report)

A bench-scale system was designed and built to test an aminosilicone-based solvent. A model was built of the bench-scale system and this model was scaled up to model the performance of a carbon capture unit, using aminosilicones, for CO 2 capture and sequestration (CCS) for a pulverized coal (PC) boiler at 550 MW. System and economic analysis for the carbon capture unit demonstrates that the aminosilicone solvent has significant advantages relative to a monoethanol amine (MEA)-based system. The CCS energy penalty for MEA is 35.9% and the energy penalty for aminosilicone solvent is 30.4% using a steam temperature of 395 °C (743 °F). If the steam temperature is lowered to 204 °C (400 °F), the energy penalty for the aminosilicone solvent is reduced to 29%. The increase in cost of electricity (COE) over the non-capture case for MEA is ~109% and increase in COE for aminosilicone solvent is ~98 to 103% depending on the solvent cost at a steam temperature of 395 °C (743 °F). If the steam temperature is lowered to 204 °C (400 °F), the increase in COE for the aminosilicone solvent is reduced to ~95-100%.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2014

Geothermal Power Production: Alternative Scenarios and Critical Issues

This is the last in a series of reports that completes the life cycle analyses (LCAs) of geothermal power production technologies conducted by Argonne National Laboratory. It addresses the remaining critical issues pertaining to the LCAs of geothermal electricity production: the relative contributions from plant operations and maintenance (O&M), from decommissioning (dcm), from well field exploration, and from plant operational greenhouse gas (GHG) emissions to the total life cycle performance of geothermal power plants. Contributions from O&M and dcm to the performance of other power generating technologies are also discussed. Also included in this study are LCA results for a new series of scenarios for geothermal power production. Our analysis uses fossil fuel energy consumption and GHG emissions per unit of lifetime electricity output (referred to as the fossil energy and GHG ratios, respectively) as the life cycle metrics for quantifying life cycle stage contributions to their corresponding totals, which were subsequently used for comparing the environmental performance of geothermal and other electric power production plants. Based on literature results, we concluded that the contribution from dcm to both ratios is negligible for power plants in general. Further, we found that the contribution from O&M to both ratios is generally significant for facilities with no fuel cycle (fuel production and use) burdens. In the case of geothermal power production, O&M contributes about 20% to the total for enhanced geothermal power plants, 10% for geothermal binary plants, and about 25% of the energy ratio for geothermal flash and dry steam plants. However, due to operational GHG emissions that are unique among geothermal power plants, O&M contributes only about 1% of total GHG ratios for flash and dry steam plants. These GHG emissions arise when the geofluids of these plants become exposed to the atmosphere, thus releasing dissolved GHGs. The amount of GHG emissions from these plants had a wide range. However, we found that 85% of California’s running capacity in flash and dry steam plants released 160 grams or less per kilowatt-hour of electricity produced. We developed an exploration model to account for core hole, slim hole, and confirmation well drilling that includes a probability of success for confirmation well drilling. The model shows that well field exploration represents about 20% of the total life cycle burden for large geothermal plants with numerous wells and 32% of the burden for small plants with few wells. We also analyzed a set of geothermal scenario pairs. The objective was to identify geothermal scenarios with a lower levelized cost of electricity and lower life cycle burdens. A comparison of reference with improved cases within each pair revealed that the improved cases demonstrated a lower levelized cost of electricity and lower fossil energy consumption and GHG metrics. The scenario pairs covered a range of plant capacities, well numbers and depths, resource temperatures, and plant lifetimes. Finally, we found that compared to fossil-fuel generation of electricity, both flash and dry steam geothermal electricity generation result in fewer GHG emissions: on average, only one-fifth of the GHG emissions per kilowatt-hour from a natural gas combined-cycle plant, and one-tenth of those from a coal-fired plant. Moreover, these fractions were much smaller when the fossil plants were compared with plants that use geothermal binary technology.

Sullivan, J. L.↗
DOE OSTI2013

Next Generation Pressurized Oxy-Coal Combustion: High Efficiency and No Flue Gas Recirculation

The Gas Technology Institute (GTI) has developed a pressurized oxy-coal fired molten bed boiler (MBB) concept, in which coal and oxygen are fired directly into a bed of molten coal slag through burners located on the bottom of the boiler and fired upward. Circulation of heat by the molten slag eliminates the need for a flue gas recirculation loop and provides excellent heat transfer to steam tubes in the boiler walls. Advantages of the MBB technology over other boilers include higher efficiency (from eliminating flue gas recirculation), a smaller and less expensive boiler, modular design leading to direct scalability, decreased fines carryover and handling costs, smaller exhaust duct size, and smaller emissions control equipment sizes. The objective of this project was to conduct techno-economic analyses and an engineering design of the MBB project and to support this work with thermodynamic analyses and oxy-coal burner testing. Techno-economic analyses of GTI’s pressurized oxy-coal fired MBB technology found that the overall plant with compressed CO2 has an efficiency of 31.6%. This is a significant increase over calculated 29.2% efficiency of first generation oxy-coal plants. Cost of electricity (COE) for the pressurized MBB supercritical steam power plant with CO2 capture and compression was calculated to be 134% of the COE for an air-coal supercritical steam power plant with no CO2 capture. This compares positively with a calculated COE for first generation oxy-coal supercritical steam power plants with CO2 capture and compression of 164%. The COE for the MBB power plant is found to meet the U.S. Department of Energy (DOE) target of 135%, before any plant optimization. The MBB power plant was also determined to be simpler than other oxy-coal power plants with a 17% lower capital cost. No other known combustion technology can produce higher efficiencies or lower COE when CO2 capture and compression are included. A thermodynamic enthalpy and exergy analysis found a number of modifications and adjustments that could provide higher efficiency and better use of available work. Conclusions from this analysis will help guide the analyses and CFD modeling in future process development. The MBB technology has the potential to be a disruptive technology that will enable coal combustion power plants to be built and operated in a cost effective way, cleanly with no carbon dioxide emissions. A large amount of work is needed to quantify and confirm the great promise of the MBB technology. A Phase 2 proposal was submitted to DOE and other sponsors to address the most critical MBB process technical gaps. The Phase 2 proposal was not accepted for current DOE support.

Rue, David↗