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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Timed to save: the added value of accounting for hourly incidence of electricity savings from residential space-conditioning measures

Abstract Previous research has recognized that the value of measures that reduce electricity usage depends upon the timing of the savings generated, but the lack of hourly savings shapes has limited the demonstration of this concept. We develop empirical hourly savings shapes for residential space-conditioning measures from nearly 18,000 efficiency projects in California and show how they combine with the diurnal and seasonal variation in electricity system costs. We find that these measures (cooling replacements; windows, doors, and skylights; and other envelope measures) tend to save electricity when system costs are highest and that the hourly savings account for 1.4–1.5 times as much value as non-time-sensitive estimates of efficiency would predict. We present these impact multipliers for each measure to quantify the additional value revealed by the time-sensitive approach. We show that this additional value is similar in an evolving electricity grid with storage, rather than natural gas generation, as the marginal resource.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
NASA NTRS1999

Estimated Benefits of Variable-Geometry Wing Camber Control for Transport Aircraft

Analytical benefits of variable-camber capability on subsonic transport aircraft are explored. Using aerodynamic performance models, including drag as a function of deflection angle for control surfaces of interest, optimal performance benefits of variable camber are calculated. Results demonstrate that if all wing trailing-edge surfaces are available for optimization, drag can be significantly reduced at most points within the flight envelope. The optimization approach developed and illustrated for flight uses variable camber for optimization of aerodynamic efficiency (maximizing the lift-to-drag ratio). Most transport aircraft have significant latent capability in this area. Wing camber control that can affect performance optimization for transport aircraft includes symmetric use of ailerons and flaps. In this paper, drag characteristics for aileron and flap deflections are computed based on analytical and wind-tunnel data. All calculations based on predictions for the subject aircraft and the optimal surface deflection are obtained by simple interpolation for given conditions. An algorithm is also presented for computation of optimal surface deflection for given conditions. Benefits of variable camber for a transport configuration using a simple trailing-edge control surface system can approach more than 10 percent, especially for nonstandard flight conditions. In the cruise regime, the benefit is 1-3 percent.

Bolonkin, Alexander↗
NASA NTRS2022

Tentative Evidence for Water Vapor in the Atmosphere of the Neptune-sized Exoplanet HD106315c

We present a transmission spectrum for the Neptune-sized exoplanet HD 106315c from optical to infrared wavelengths based on transit observations from the Hubble Space Telescope/Wide Field Camera 3, K2, and Spitzer. The spectrum shows tentative evidence for a water absorption feature in the 1.1–1.7 μm wavelength range with a small amplitude of 30 ppm (corresponding to just 0.8 ± 0.04 atmospheric scale heights). Based on an atmospheric retrieval analysis, the presence of water vapor is tentatively favored with a Bayes factor of 1.7–2.6 (depending on prior assumptions). The spectrum is most consistent with either an enhanced metallicity or high-altitude condensates, or both. Cloud-free solar composition atmospheres are ruled out at >5σ confidence. We compare the spectrum to grids of cloudy and hazy forward models and find that the spectrum is fit well by models with moderate cloud lofting or haze formation efficiency over a wide range of metallicities (1–100× solar). We combine the constraints on the envelope composition with an interior structure model and estimate that the core mass fraction is ≳0.3. With a bulk composition reminiscent of that of Neptune and an orbital distance of 0.15 au, HD 106315c hints that planets may form out of broadly similar material and arrive at vastly different orbits later in their evolution.

Exoplanet atmospheres↗
DOE OSTI2025

Assessing the hygrothermal performance of bio-based materials in building wall systems

Building envelope systems are crucial in regulating thermal and moisture exchange between interior and exterior environments, accounting for approximately 28 % of building energy consumption in the United States with walls being the primary contributors. Improper selection of building envelope materials can lead to moisture-related issues, reduced resilience, and compromised durability. Hygrothermal performance assessment is a key factor in efficient building design. As such, improving the energy and hygrothermal performance of opaque wall materials, through careful assessment of material choices, is essential to enhancing building resilience, lowering energy costs, and improving occupant comfort. As the building industry seeks new strategies to reduce material energy intensity, bio-based materials emerge as a promising solution. However, their long-term hygrothermal performance in building envelope systems remains underexplored. To fill this gap, this study evaluates the hygrothermal behavior of 13 bio-based materials in residential wall systems across three U.S. climate zones. Laboratory experiments were performed to measure material properties such as density, thermal conductivity, moisture transmission, and sorption isotherms. These data were integrated into the WUFI® simulation tool to assess wall hygrothermal performance in Houston, Baltimore, and Chicago. A three-phase modeling approach was used: (1) baseline residential walls with oriented strand board (OSB) and gypsum board; (2) replacing OSB with bio-based materials; and (3) replacing drywall with bio-based materials. Results showed that the evaluated bio-based materials maintained acceptable moisture thresholds of ≤ 16 % across all climates, confirming their viability as an alternative for current sheathing materials. Furthermore, this study provides a foundation for future research and innovation in material science on the use of certain bio-based materials in high-performance, low energy use residential construction. Ultimately, providing critical data, offering a database of bio-based material properties, and supplying a simulation-based approach will help designers make informed decisions for future efficient building practices.

Bio-based materials↗
DOE OSTI2017

Impact of Protostellar Outflows on Turbulence and Star Formation Efficiency in Magnetized Dense Cores

The star-forming efficiency of dense gas is thought to be set within cores by outflow and radiative feedback. We use magnetohydrodynamic simulations to investigate the relation between protostellar outflow evolution, turbulence, and star formation efficiency. We model the collapse and evolution of isolated dense cores for ≳0.5 Myr including the effects of turbulence, radiation transfer, and both radiation and outflow feedback from forming protostars. We show that outflows drive and maintain turbulence in the core environment even with strong initial fields. The star formation efficiency decreases with increasing field strength, and the final efficiencies are 15%–40%. The Stage 0 lifetime, during which the protostellar mass is lower than that of the dense envelope, increases proportionally with the initial magnetic field strength and ranges from ∼0.1 to 0.4 Myr. The average accretion rate is well represented by a tapered turbulent core model, which is a function of the final protostellar mass and is independent of the magnetic field strength. By tagging material launched in the outflow, we demonstrate that the outflow entrains about three times the actual launched gas mass, a ratio that remains roughly constant in time regardless of the initial magnetic field strength. However, turbulent driving increases for stronger fields since momentum is more efficiently imparted to non-outflow material. The protostellar outflow momentum is highest during the first 0.1 Myr and declines thereafter by a factor of ≳10 as the accretion rate diminishes.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

Model-based, in-situ, non-destructive qualification and certification of parts made by autonomous additive manufacturing

To address the significant productivity challenges associated with the qualification and certification (Q&C) tasks of additively manufactured (AM) parts, which have traditionally relied on rigorous post‐build inspection and testing, we propose an integrated framework that combines model‐based qualification and certification (MBQ&C) with autonomous additive manufacturing (AAM). MBQ&C employs high‐fidelity predictive models, developed within the Integrated Computational Materials Engineering (ICME) paradigm, to simulate process–structure–property–performance relationships for assessing a part’s fitness for use. Since predictive models are commonly machine learning (ML)-based or reduced-order surrogates of validated physics models, they run efficiently, enabling timely inference. In parallel, the self-driving AAM utilises ML-based adaptive, closed‐loop control strategies to avoid, mitigate, or repair defects and anomalies during fabrication, thereby increasing the likelihood of producing acceptable parts. A key feature of the combined AAM-MBQ&C framework is that predictive models explicitly incorporate defects or anomalies that persist after the build, using instance-specific data captured via in-situ sensing. This customisation enables a build‐specific assessment of fitness for use, rather than relying on nominal or generic parameters. Such individualised evaluation provides a robust basis for Q&C-related acceptance decisions relating to each build. Additionally, the rapid solution capabilities of ML or reduced-order models enable the determination of a part’s suitability for service shortly after build completion. As the framework matures, it has the potential to substantially reduce reliance on conventional point‐design approaches—such as time‐consuming post‐build computed tomography scanning and costly destructive testing. Thus, the AAM-MBQ&C framework represents a transformative, scalable strategy for quality assurance of AM components, as parts produced within a stable, validated, and certified envelope can be certified with reduced testing. Key benefits include: (1) significant gains in Q&C productivity through efficient, model-centric assessment; (2) performance-based classification of defects into critical and non-critical categories; (3) the ability to predict potential deviations in the performance of parts affected by real-time, adaptive process control interventions relative to those produced under a certified process, and (4) the enabling of virtual Q&C for service environments that are difficult, hazardous, or impractical to access or reproduce experimentally. Collectively, these capabilities strengthen the business case for AM, particularly for high‐consequence and mission‐critical applications. Finally, although this work focuses on powder-based AM, the proposed techniques could be extended to AM processes employing alternative feedstock forms.

Gunasegaram, Dayalan↗
DOE OSTI2024

Positioning Accuracy in a Concurrent Robot-CNC Hybrid Manufacturing System

Abstract Additive manufacturing (AM) has gained notoriety for offering advantages over traditional manufacturing methods, such as increased design complexity and flexibility. However, it has not found widespread use beyond rapid prototyping. One hindrance to the acceptance of AM processes in industry is the time and cost of fabrication per component. While metal AM by itself can be inexpensive, extra manufacturing steps in the form of subtractive manufacturing (SM) may need to be performed to reach final part tolerances, leading to hybrid additive-subtractive manufacturing (HASM) of a part, which increases time and cost. A potential area to reduce cost is through increasing the efficiency of the HASM process by conducting additive and subtractive manufacturing simultaneously. Usually, HASM is performed in a process where AM is completed in one machine or cell and transferred to another machine or cell for SM in a sequential assembly line process. This efficiency decreases part cost, but high aspect ratio parts or parts with internal geometry that require interleaved additive deposition and machining cannot be produced. One unexplored solution to simultaneous HASM that allows for interleaved operations is to operate the deposition head and machining spindle concurrently within the same machine envelope, known as concurrent HASM (CHASM). In this type of process, both AM and SM occur simultaneously on a batch of small parts or a single large part, maintaining a high efficiency without sacrificing the full range of complex geometries that AM allows for. A potential approach to the single-machine method could be to combine a robot and mill within the same envelope. A challenge to this approach, however, is control of both systems. Most machine controllers have limited external communication or, if a robot has been integrated, only offer movement of either the robot or mill at any given time. As a result, systems must pause either the AM or SM process to switch between them rather than working simultaneously. The present work investigates the positional accuracy of such a CHASM system comprised of a robotic arm and a 3-axis mill. Open-loop tests with limited communication between machines are performed on the system to verify positional error during concurrent robot-mill movements. Under certain conditions, it is demonstrated that position error can stay within 2 mm for the duration of a single layer; however, these tests show that, generally, the open-loop positioning performance of the system is inadequate for CHASM without part-specific hand-tuning of parameters. Based on these results, a set of requirements for successful robot-CNC CHASM is proposed for future integrations.

Goodwin, Jesse↗
DOE OSTI2015

Stability and coalescence of massive twin binaries

Massive stars are usually found in binaries, and binaries with periods less than 10 days may have a preference for near equal component masses (“twins”). In this paper we investigate the evolution of massive twin binaries all the way to contact and the possibility that these systems can be progenitors of double neutron star binaries. The small orbital separations of observed double neutron star binaries suggest that the progenitor systems underwent a common envelope phase at least once during their evolution. Bethe and Brown proposed that massive binary twins will undergo a common envelope evolution while both components are ascending the red giant branch (RGB) or asymptotic giant branch (AGB) simultaneously, also known as double-core evolution. Using models generated from the stellar evolution code EZ (evolve zero-age main sequence), we determine the range of mass ratios resulting in a contact binary with both components simultaneously ascending the RGB or AGB as a function of the difference in birth times, Δτ. We find that, even for a generous Δτ = 5 Myr, the minimum mass ratio q{sub min}=0.933 for an 8 M{sub ⊙} primary and increases for larger mass primaries. We use a smoothed particle hydrodynamics code, StarSmasher, to study specifically the evolution of q = 1 common envelope systems as a function of initial component mass, age, and orbital separation. We also consider a q = 0.997 system to test the effect of relaxing the constraint of strictly identical components. We find the dynamical stability limit, the largest orbital separation where the binary becomes dynamically unstable, as a function of the component mass and age. Finally, we calculate the efficiency of ejecting matter during the inspiral phase to extrapolate the properties of the remnant binary from our numerical results, assuming the common envelope is completely ejected. We find that for the nominal core masses, there is a minimum orbital separation for a given component mass such that the helium cores survive common envelope evolution in a tightly bound binary and are viable progenitors for double neutron stars.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

Hygric Redistribution in Insulated Assemblies: Retrofitting Residential Envelopes Without Creating Moisture Issues

This research report was prepared by the Building Science Corporation Building America Research Team as part of the Energy Efficient Housing Research Partnerships project. The project title is Hygric Redistribution in Insulated Assemblies. The exterior retrofit of frame assemblies can be risky when impermeable insulating sheathings of relatively low thermal resistance are used. For example, basic hygrothermal analysis demonstrates that removing the existing cladding and installing a board foam insulation with low vapor permeance (such as ½-in. foil faced rigid insulation) directly over the sheathing membrane under a replacement cladding (such as vinyl siding) is likely to cause moisture problems in cold climates. One such problem is known as a “cold sided vapor barrier.” Tens of thousands of such retrofit and renovation projects have been completed, however, without apparent problems. There is also a perception that when water is intentionally drained in a drainage cavity between exterior insulation and the existing structure following an energy retrofit, moisture-related durability concerns exist for the sheathing and wood structure. This experimental program includes a literature review of previous research, laboratory testing programs, and an analysis of full-scale test wall performance in the U.S. Department of Energy’s climate zone 4C.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2012

Non-abelian symmetries in tensor networks: A quantum symmetry space approach

A general framework for non-abelian symmetries is presented for matrix-product and tensor-network states in the presence of well-defined orthonormal local as well as effective basis sets. The two crucial ingredients, the Clebsch-Gordan algebra for multiplet spaces as well as the Wigner-Eckart theorem for operators, are accounted for in a natural, well-organized, and computationally straightforward way. The unifying tensor-representation for quantum symmetry spaces, dubbed QSpace, is particularly suitable to deal with standard renormalization group algorithms such as the numerical renormalization group (NRG), the density matrix renormalization group (DMRG), or also more general tensor networks such as the multi-scale entanglement renormalization ansatz (MERA). In this paper, the focus is on the application of the non-abelian framework within the NRG. A detailed analysis is presented for a fully screened spin- 3/2 three-channel Anderson impurity model in the presence of conservation of total spin, particle-hole symmetry, and SU(3) channel symmetry. The same system is analyzed using several alternative symmetry scenarios based on combinations of U(1){sub charge}, SU(2){sub spin}, SU(2){sub charge}, SU(3){sub channel}, as well as the enveloping symplectic Sp(6) symmetry. These are compared in detail, including their respective dramatic gain in numerical efficiency. In the Appendix, finally, an extensive introduction to non-abelian symmetries is given for practical applications, together with simple self-contained numerical procedures to obtain Clebsch-Gordan coefficients and irreducible operators sets. The resulting QSpace tensors can deal with any set of abelian symmetries together with arbitrary non-abelian symmetries with compact, i.e. finite-dimensional, semi-simple Lie algebras. - Highlights: Black-Right-Pointing-Pointer We introduce a transparent framework for non-abelian symmetries in tensor networks. Black-Right-Pointing-Pointer The framework was successfully applied within the numerical renormalization group. Black-Right-Pointing-Pointer Combinations of SU(N{<=}3) and Sp(6) are implemented and discussed in detail. Black-Right-Pointing-Pointer Non-abelian symmetries allow to speed up calculations by orders of magnitude. Black-Right-Pointing-Pointer The framework is equally applicable to other tensor networks such as DMRG or MERA.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Strain-graded quantum dots with spectrally pure, stable and polarized emission

Structural deformation modifies the bandgap, exciton fine structure and phonon energy of semiconductors, providing an additional knob to control their optical properties. The impact can be exploited in colloidal semiconductor quantum dots (QDs), wherein structural stresses can be imposed in three dimensions while defect formation is suppressed by controlling surface growth kinetics. Yet, the control over the structural deformation of QDs free from optically active defects has not been reached. Here, we demonstrate strain-graded CdSe-ZnSe core-shell QDs with compositionally abrupt interface by the coherent pseudomorphic heteroepitaxy. Resulting QDs tolerate mutual elastic deformation of varying magnitudes at the interface with high structural fidelity, allowing for spectrally stable and pure emission of photons at accelerated rates with near unity luminescence efficiency. We capitalize on the asymmetric strain effect together with the quantum confinement effect to expand emission envelope of QDs spanning the entire visible region and exemplify their use in photonic applications.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
NASA NTRS1991

Technology needs for high speed rotorcraft (2)

An analytical study was conducted to identify rotorcraft concepts best capable of combining a cruise speed of 350 to 450 knots with helicopter-like low speed attributes, and to define the technology advancements needed to make them viable by the year 2000. A systematic approach was used to compare the relative attributes and mission gross weights for a wide range of concepts, resulting in a downselect to the most promising concept/mission pairs. For transport missions, tilt-wing and variable diameter tilt-rotor (VDTR) concepts were found to be superior. For a military scout/attack role, the VDTR was best, although a shrouded rotor concept could provide a highly agile, low observable alternative if its weight empty fraction could be reduced. A design speed of 375 to 425 knots was found to be the maximum desirable for transport missions, with higher speed producing rapidly diminishing benefits in productivity. The key technologies that require advancement to make the tilt-wing and VDTR concepts viable are in the areas of wing and proprotor aerodynamics, efficient structural design, flight controls, refinement of the geared flap pitch control system, expansion of the speed/descent envelope, and the structural and aerodynamic tradeoffs of wing thickness and forward sweep. For the shrouded rotor, weight reduction is essential, particularly with respect to the mechanism for covering the rotor in cruise.

Scott, Mark W.↗
DOE OSTI2017

A modified eco-efficiency framework and methodology for advancing the state of practice of sustainability analysis as applied to green infrastructure: Sustainability Analysis of Rainwater Harvesting

We propose a modified eco-efficiency (EE) framework and novel sustainability analysis methodology for green infrastructure (GI) practices used in water resource management. Green infrastructure practices such as rainwater harvesting (RWH), rain gardens, porous pavements, and green roofs are emerging as viable strategies for climate change adaptation. The modified framework includes 4 economic, 11 environmental, and 3 social indicators. Using 6 indicators from the framework, at least 1 from each dimension of sustainability, we demonstrate the methodology to analyze RWH designs. We use life cycle assessment and life cycle cost assessment to calculate the sustainability indicators of 20 design configurations as Decision Management Objectives (DMOs). Five DMOs emerged as relatively more sustainable along the EE analysis Tradeoff Line, and we used Data Envelopment Analysis (DEA), a widely applied statistical approach, to quantify the modified EE measures as DMO sustainability scores. We also addressed the subjectivity and sensitivity analysis requirements of sustainability analysis, and we evaluated the performance of 10 weighting schemes that included classical DEA, equal weights, National Institute of Standards and Technology’s stakeholder panel, Eco-Indicator 99, Sustainable Society Foundation’s Sustainable Society Index, and 5 derived schemes. We improved upon classical DEA by applying the weighting schemes to identify sustainability scores that ranged from 0.18 to 1.0, avoiding the nonuniqueness problem and revealing the least to most sustainable DMOs. Our methodology provides a more comprehensive view of water resource management and is generally applicable to GI and industrial, environmental, and engineered systems to explore the sustainability space of alternative design configurations.

Sustainability Rainwater harvesting↗
DOE OSTI2026

Technology pathways for energy- and water-efficient controlled environment agriculture: A review of technologies, implementation pathways, and regional use cases

Controlled Environment Agriculture (CEA) offers high-yield, climate-resilient food production, but high energy and resource demands challenge its sustainability. This paper synthesizes technologies that can improve outcomes across six categories—energy, CO 2 utilization, building envelope, hardware, water, and process—plus colocation strategies. We evaluate 80 technologies and define ten implementation pathways bundling complementary technologies to reduce energy use, optimize water consumption, and minimize emissions. Regional application is demonstrated through five U.S. case studies spanning different climates. A logic framework guides pathway selection for case studies based on climate, infrastructure, and regulatory context, informing context-sensitive technology deployment. Results show energy intensity reductions of 3–55 %, ranging from energy management programs to comprehensive lighting retrofits; water savings of 20–40 % through closed-loop recirculation; and emissions reductions of 3–100 %, with strategic energy management achieving 3–5 % and renewable electricity paired with electrified heating achieving up to 100 %. Text mining revealed that energy, hardware, and process technologies account for 91 % of literature coverage. Water, building envelope, and CO 2 utilization remain underexplored, indicating priorities for future research. This integrative approach to technology assessment supports growers, developers, and policymakers in aligning CEA system design with local conditions, improving resource efficiency and addressing gaps in cross-domain technology coverage.

Controlled environment agriculture↗
DOE OSTI2022

Enhancement of phase change material hysteresis model: A case study of modeling building envelope in EnergyPlus

Nowadays, buildings are expected to offer demand side services to the power grid to enhance the electrical load flexibility, which leads to the concepts of grid-interactive efficient buildings (GEBs). Phase change material (PCM)-based thermal energy storage has seen increasing attention in recent years for peak load shifting of grid-interactive efficient buildings (GEBs). Numerical models are critical tools for design and evaluation of PCM-integrated systems. Most industrial-grade PCMs are reported to melt/freeze over a temperature range instead of at a unique temperature. Such thermal hysteresis effect significantly affects the reliability of simulation results because not only the heat transfer process depends on melting and freezing temperatures, the PCM thermal properties change significantly during the phase change process as well. This study is aimed to develop a model for the PCMs used in the building envelope with the capability to accurately simulate hysteretic behaviors. Further, this model is based on a two-phase assumption and is implemented in a whole building energy performance simulation program (i.e., EnergyPlus). A comparison between numerical results and experimental data shows that during a complete phase transition, the two-phase model could achieve a good agreement with the experimental data. During a partial phase transition, the two-phase model could lead to significant improvements compared to other alternative PCM models, including the existing PCM model in EnergyPlus. Last, whole building simulations were performed to study this model's performance regarding heating/cooling loads and zone mean air temperature of a given building. The results show that the difference in hourly heating/cooling loads introduced by the models was less than 1% in design conditions, while significant changes were observed in both hourly heating/cooling loads and zone mean air temperature when the PCM envelope underwent partial phase transition processes.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
NASA NTRS1986

A high resolution spectrometer for EUV/FUV wavelengths

The most efficient of the various configurations considered for a high-resolution spaceborne spectrometer for point-source astronomy in the 400-1200-A wavelength region which will fit within an envelope defined by the projected Spartan space platform is a multiple Rowland circle spectrograph, with each of four toroidal gratings respectively intercepting a fraction of the primary mirror beam. Each spectrometer can accept a rather slowly diverging beam, reducing grating aberrations, without further efficiency loss due to additional reflections or magnification. The line densities, detector size, pixel size, etc., of the detector for this instrument are dependent on the drift rate of the space platform; a design optimized for an uncorrected 4-arcsec drift is presented.

Hurwitz, Mark↗
DOE OSTI2023

Low-Voltage Haze Tuning with Cellulose-Network Liquid Crystal Gels

Being key components of the building envelope, glazing products with tunable optical properties are in great demand because of their potential for boosting energy efficiency and privacy features while enabling the main function of allowing natural light indoors. However, windows and skylights with electric switching of haze and transparency are rare and often require high voltages or electric currents, as well as not fully meet the stringent technical requirements for glazing applications. Here, by introducing a predesigned gel material we describe an approach dubbed “Haze-Switch” that involves low-voltage tuning of the haze coefficient in a broad range of 2–90% while maintaining high visible-range optical transmittance. The approach is based on a nanocellulose fiber gel network infiltrated by a nematic liquid crystal, which can be switched between polydomain and monodomain spatial patterns of optical axis via a dielectric coupling between the nematic domains and the applied external electric field. By utilizing a nanocellulose network of nanofibers ~10 nm in diameter we achieve <10 V dielectric switching and <2% haze in the clear state, as needed for applications in window products. Finally, we characterize physical properties relevant to window and smart glass technologies, like the color rendering index, haze coefficient, and switching times, demonstrating that our material and envisaged products can meet the stringent requirements of the glass industry, including applications such as privacy windows, skylights, sunroofs, and daylighting.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Final Report UCLA-Thermochemical Storage with Anhydrous Ammonia

In ammonia-based thermochemical energy storage (TCES), ammonia is dissociated endothermically as it absorbs solar energy during the daytime. When energy is required, the reverse reaction releases energy to heat a working fluid such as steam, to produce electricity. Ammonia-based TCES has great advantages of simplicity, low cost reactants, and a strong industrial base in the conventional ammonia industry. The concept has been demonstrated over three decades of research at Australian National University, achieving a 24-hour demonstration of a complete system. At the start of this project, three challenges were identified that would have to be addressed to show that the system is technically and economically viable for incorporation into a CSP plant with an advanced, high temperature power block. All three of these challenges have now been addressed: 1. The ammonia synthesis reaction had not, to our knowledge, been carried out at temperatures consistent with modern power blocks (i.e., ~650°C). The technical feasibility of operating a reactor under high-temperature, near-equilibrium conditions was an unknown, and was therefore a technical risk. The project has successfully demonstrated steam heating to 650°C and energy recovery to steam at the 5 kWt level. 2. The ammonia system has a relatively low enthalpy of reaction combined with gas phase reactants. This is not a direct disadvantage since the reactants themselves are low cost. The challenge lies in storing the required volume of reactants cost effectively. Therefore, a second key goal was to show, through techno-economic analysis, that underground storage technologies can be used to store the energy-rich gas at a cost that is consistent with the SunShot cost goal. We have identified two promising technologies for gas storage: storage in salt caverns has an estimated cost of 1(USD)/kWht and storage in drilled shafts could be on the order of 7(USD)/kWht. Together these two options answer the technical challenge associated with storage of gas phase components. 3. While this project is primarily concerned with high-temperature heat recovery and methods to store the gaseous components, it is also important to consider the feasibility of the entire system. Consequently, an additional goal was to perform analysis to show the feasibility of integrating endothermic reactors within a tower receiver. A conceptual design of an ammonia dissociation receiver/reactor has been developed that fits into the same size cylindrical envelope as the molten salt receiver in SAM, and has the same design thermal capacity. The calculated thermal efficiency of this receiver is 94.6%. Thus, this investigation has established the technical feasibility of a surround field tower system using ammonia dissociation. With these challenges addressed, we proceeded to design a full-scale synthesis and heat recovery system. A model was developed and validated by comparison with our experimental data. A parametric study showed, among other things, the importance of using small tube diameters and spacing to enhance heat transfer. Multi-parameter optimization was used to find a design that minimizes the wall material volume. Finally, cost estimation shows that the ammonia system has good prospects of meeting the Sunshot 15(USD)/kWht target: estimated costs of the entire synthesis system for the 220 MWt plant with 6 hours of storage are 13(USD)/kWht using salt cavern storage and 18(USD)/kWht using shaft drilling. Costs per kWht are even lower with more hours of storage. With the established technology of ammonia synthesis as a starting point, the successes of the project have mitigated technical risks associated with high-temperature synthesis reaction, underground storage, and tower receiver design. Estimated costs are less than 15(USD)/kWht with salt cavern storage. It is now possible to map a time line to commercial deployment that is likely to be shorter and less risky than other thermochemical cycles under active investigation. UCLA has filed a patent that protects the new ideas developed during this project. Discussions are ongoing with potential investors with the aim of partnering for further work. As well as immediate improvements and extra work with the existing experimental system, a key goal is to extend it to a small solar-driven project at an early opportunity.

14 SOLAR ENERGY↗