Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Concentrated Solar”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Performance of a Prototype Heliostat Having a Twisting Mechanism to Maintain Focus Throughout the Day

A prototype heliostat has been designed and built with a rectangular reflector whose shape is altered automatically through the day, to maximize concentration at the receiver. The shape changes needed to form solar disc images, which give the highest possible concentration, can be realized by twisting the reflector from its corners, provided that a target-oriented, dual-axis mount is used. Then a cam mechanism connected to the second (cross) axis drive, turning with the angle of incident sunlight, may be used to twist the reflector as needed. Our prototype reflector comprises a single glass mirror, 2.4 m x 3.3 m, attached to a steel frame. Four diagonal back struts extend from the central mechanism out to the rectangular frame corners. The glass mirror of the prototype is attached to the steel frame by 58 screw actuators. Before twisting the frame, the glass shape is adjusted to the biconic shape needed to form a 1 m diameter disc image on a 113 m distant target when sunlight is incident at 60°. To form disc images over the full range of angles of incidence from 0° (normal incidence) to 70°, the struts push the corners up and down by up to 17 mm. A reflectometry metrology system has been used to set the 58 adjustment screws for the initial shape to an accuracy of ≤ 0.6 mrad, and to measure the accuracy of the different twisted shapes. The prototype will be tested at NSTTF early next year.

14 SOLAR ENERGY↗
DOE OSTI2024

Design, performance, and field operation of twisting heliostats for 3,000-sun concentration and high temperature

The idea is to combine the solar energy reflected from a field of many heliostats to obtain a single focus of high concentration and high power. We exploit a new type of “twisting” heliostat” in which as the mount is moved to track the sun through the day, the reflector shape is twisted to maintain a focused image of the sun’s disc on the target, through the day over a wide range of angles of incidence. By combining the light reflected by many twisting heliostats into a single focus, we are not only able to accomplish but also maintain very high concentration and temperature through the day, with higher efficiency than has previously been possible with conventional heliostats having a fixed shape. A circular field of twisting heliostats is used to power a single intense focus atop a central tower. The light from all the heliostats is relayed to an upward facing receiver at the focus via a central Cassegrain secondary reflector located above the receiver. In a specific design targeting 1 MW of power, a 100 m diameter field arrays 431 twisting heliostats, each with a 7 m2 reflector. The secondary reflector ,7.2 m in diameter, is located 24 m above the heliostat field, bringing sunlight with annual average power of 1 MW to a circular focus 0.8 m in diameter, at a concentration averaging 3,000 suns.

14 SOLAR ENERGY↗
DOE OSTI2020

Pumped Thermal Energy Storage: Thermodynamics and Economics

This presentation gives an overview of Pumped Thermal Energy Storage (PTES), and in particular concentrates on the performance and cost of a Joule-Brayton cycle with liquid storage. Results for systems with supercritical CO2 are also presented. PTES may be hybridized with solar heat, and some examples are provided as well as an overview of potential issues.

41 EE - Solar Energy Technologies Office (EE-4S)↗
DOE OSTI2020

Plasmon-Enhanced Greenhouse Selectivity for High-Temperature Solar Thermal Energy Conversion

The greenhouse effect arises when thermal radiation is forced to undergo absorption and re-emission many times before escaping, while sunlight transmits largely unimpeded. Although this effect is responsible for global warming, it is generally weak in solid-state materials because radiation can be easily overpowered by other modes of heat transfer. Here, we report on the use of infrared plasmonic nanoparticles to enhance the greenhouse effect in transparent mesoporous materials. Local surface plasmon resonances in transparent conducting oxide nanoparticles (TCO NPs) selectively shorten the mean free path of thermal photons while maintaining high solar transmittance. The addition of a small amount of TCO NPs (<0.1% by volume) nearly halves the heat losses at 700 °C. This leads to an experimentally demonstrated effective thermal emittance of ~0.17 at 700 °C, which is the lowest reported value to date, among all selective surfaces and transparent insulating materials measured at 650 °C or above. Furthermore, our results show that plasmon-enhanced greenhouse selectivity (PEGS) is a promising mechanism for spectral control of radiative heat transfer, and more specifically, for conversion of minimally concentrated sunlight into high-temperature heat.

14 SOLAR ENERGY↗
DOE OSTI2023

Performance Analyses of Supercritical Carbon Dioxide-Based Parabolic Trough Collectors with Double-Glazed Receivers

Supercritical carbon dioxide is becoming a hot research topic as a potential heat transfer fluid in parabolic trough concentrators since it enables operating the solar system at high temperatures for a higher quality of energy. However, the corresponding inflated thermal losses necessitate alternative receiver designs. This work examines four double-glazed receivers, with each annular space being evacuated or non-evacuated, in terms of the absorber tube's diameter (53-80 mm) and the diameter ratios of the two glass shells (1.2-2.0). An analytical model is developed and validated for this purpose, and the four designs are further examined using ground-level solar and meteorological measurements. The results demonstrate higher performance in the case of fully evacuating the receiver and using the smallest possible diameters of the three concentric cylinders, where the energy and exergy efficiencies reach 65.3 and 40.3%, respectively. Yet, evacuating only the inner annular space is sufficient to achieve virtually the same performance level. This energy efficiency decreases to 62% in case of increasing the tube diameter to 80 mm. As the operating temperature increases from 423 to 850 K, the specific thermal losses increase by 3.98-4.34 folds, depending on the receiver design. Double glazing the receivers is favorable only at high operating temperatures of sCO2, where the reduction in thermal losses overcomes the drop in optical efficiency. For an inlet sCO2 temperature of 850 K, thermal losses are reduced by 33.64 and 53.92%, compared to evacuated and non-evacuated single-glazed receivers, respectively. Throughout the year, the fully evacuated and fully non-evacuated double-glazed receivers have energy efficiencies of 54.96 and 52.39%, exergy efficiencies of 33.64 and 32.06%, and thermal losses of 348.8 and 402.5 W/m, respectively.

analytical model↗
DOE OSTI2023

Topographic Correction of Optical Remote Sensing Images in Mountainous Areas: A systematic review

Rugged terrain distorts optical remote sensing observations and subsequently impacts land cover classification and biophysical and biochemical parameter retrieval over mountainous areas. Therefore, topographic correction (TC) is a prerequisite for many remote sensing applications. Although various TC methods have been explored over the past four decades to mitigate topographic effects, a systematic and global review of these studies is still lacking. Using a multicomponent bibliometric approach, we extracted bibliometric metadata from 426 publications identified by searching titles, keywords, and abstracts for research on “topographic correction” and “topographic effects” in Scopus and Web of Science (WoS) from 1980 to 2022. Here this systematic review revealed a rapid growth in the number of TC studies since the 1980s, primarily driven by the availability of decametric-resolution remote sensing observations and digital elevation models (DEMs). Most of the research has focused on relatively low-elevation regions, with increasing attention beyond American and European regions, particularly in China. The seasonal distribution of satellite acquisition for TC showed considerable imbalance, mainly concentrated in months with favorable solar illumination conditions (e.g., May to October). Important themes emerged from the keyword analysis, including satellite sensors, DEMs, TC methods, evaluation criteria, and applications.

58 GEOSCIENCES↗
DOE OSTI2024

The Escape Velocity Profile of the Milky Way from Gaia DR3

Abstract The escape velocity profile of the Milky Way offers a crucial and independent measurement of its underlying mass distribution and dark matter (DM) properties. Using a sample of stars from the third data release of Gaia with 6D kinematics and strict quality cuts, we obtain an escape velocity profile of the Milky Way from 4 to 11 kpc in Galactocentric radius. To infer the escape velocity in radial bins, we model the tail of the stellar speed distribution with both traditional power-law models and a new functional form that we introduce. While power-law models tend to rely on extrapolation to high speeds, we find our new functional form gives the most faithful representation of the observed distribution. Using this for the escape velocity profile, we constrain the properties of the Milky Way’s DM halo modeled as a Navarro–Frenck–White profile. Combined with constraints from the circular velocity at the solar position, we obtain a concentration and mass of c 200 c DM = 13.9 − 4.3 + 6.2 and M 200 c DM = 0.55 − 0.14 + 0.15 × 10 12 M ⊙ . This corresponds to a total Milky Way mass of M 200 c = 0.64 − 0.14 + 0.15 × 10 12 M ⊙ , which is on the low end of the historic range of the galaxy’s mass, but in line with other recent estimates.

Astronomy & Astrophysics↗
DOE OSTI2020

Acciona Power Plant Hydrogen Mitigation Project

In 2014, Acciona Solar Power and the National Renewable Energy Laboratory initiated discussions to identify a method to solve a long-standing efficiency loss problem at parabolic trough power plants. Parabolic trough power plants begin to show lost thermal efficiency after six years of operation, due to the presence of trace concentrations of hydrogen in the heat transfer fluid that circulates in the power plant. Trace levels of hydrogen infiltrate the collector field receivers, increasing their heat loss, and decreasing the power plants’ thermal efficiency. At the time, Acciona’s Nevada Solar One power plant in Boulder City, Nevada was starting to show this efficiency loss. After several discussions, APS and NREL agreed to a collaborative effort (CRADA) to develop and implement a method to reduce hydrogen levels in the circulating HTF at the NSO power plant. The project was planned as a three-year effort, and work started in June 2015. The CRADA’s goal was to solve the long-standing lost efficiency problem caused by the buildup of hydrogen in the HTF, which significantly impacts the efficiency, electricity generation, and revenue from parabolic trough power plants.

08 HYDROGEN↗
DOE OSTI2020

Method To Determine MgO and MgOHCl in Chloride Molten Salts

A commercial blend of mainly carnallite (KCl∙MgCl 2 ∙6H 2 O) is considered as a next-generation heat transfer fluid in solar thermal plants. Corrosive properties of MgCl2 hydrates must be addressed at the operating temperatures of 500-720 degrees C. For successful chemical monitoring of the carnallite heat transfer fluid, an experimental method was developed to separate and titrate for MgO and MgOHCl from solid carnallite. This new method was assessed for error and accuracy. The method's relative error for MgOHCl was -7.0% for a mass fraction of 9.0 wt % MgOHCl in the carnallite salt. The method's relative error for MgO was less than +1.0% for a mass fraction of 12.0 wt % MgO in the carnallite salt. Titration results were used to track changes in the MgOHCl concentration in carnallite salt through the carnallite's dehydration and purification.

14 SOLAR ENERGY↗
DOE OSTI2020

Solar geoengineering may not prevent strong warming from direct effects of CO2 on stratocumulus cloud cover

Discussions of countering global warming with solar geoengineering assume that warming owing to rising greenhouse gas concentrations can be compensated by artificially reducing the amount of sunlight Earth absorbs. However, here we show that solar geoengineering may not be fail-safe to prevent global warming because CO2 has direct effects on cloud cover: it reduces cloud cover by modulating the longwave radiative cooling within the atmosphere, which is not mitigated by solar geoengineering. We use high-resolution simulations of clouds to show that under a sustained solar geoengineering scenario, the direct CO2 effects may lead to loss of subtropical stratocumulus clouds at concentrations above 1700~ppm. Because stratocumulus clouds cover large swaths of subtropical oceans and cool Earth by reflecting incident sunlight, their loss would trigger strong (about 5 K) global warming. Thus, the results highlight that, at least in an extreme scenario, solar geoengineering may be incapable to counter greenhouse-gas driven global warming.

Schneider, Tapio↗
DOE OSTI2025

Understanding and controlling the fundamental photochemistry of protonic solar energy conversion (Final Scientific/Technical Report)

The selectivity and activity of most fuel-forming reactions are tunable by the concentration of electrons, holes, protons, and/or hydroxides. That is one reason why traditional solar energy conversion processes are used to drive these reactions, where light directly increases the concentration of electrons and holes. We, instead, took a different approach, using light to increase the concentration of protons and/or hydroxides. For this, we leveraged photophysical and solid-state physics theories, techniques, and design strategies previously developed for the study of traditional solar energy conversion processes. We designed and fabricated several materials platforms based on molecular photoacid and photobase dyes coupled with ion-exchange polymer membranes and assessed their fundamental photoelectrochemistry. We demonstrated control over built-in electric potentials, photovoltages, proton-transfer kinetics, and efficiency limits to our approach. Understanding the basic science of these dye-sensitized protonic membranes and their photochemical mechanisms is of use to the DOE-relevant processes of solar photochemical fuel formation, solar photodialytic desalination, and solar cells. Moreover, functional materials that we developed from this project may be of use to several broad-reaching fields and may provide the foundation for a completely new, inexpensive, and robust solar energy conversion technology.

14 SOLAR ENERGY↗
DOE OSTI2023

Materials Design Directions for Solar Thermochemical Water Splitting

The sustainable, economical production of molecular hydrogen is a crucial component of a net zero-greenhouse-gas-emissions future. Solar thermochemical water splitting (STWS) offers a renewable route to hydrogen with the potential to help decarbonize several industries, including transportation, manufacturing, mining, metals processing, and electricity generation, as well as provide sustainable hydrogen as a chemical feedstock. STWS uses high temperatures generated from concentrated sunlight or other sustainable means for high-temperature heat to produce hydrogen and oxygen from steam. For example, in its simplest form of a two-step thermochemical cycle, a redox-active metal oxide is heated to ≈1700-2000 K, driving off molecular oxygen while producing oxygen vacancies in the material. The reduced metal oxide then cools (ideally with the extracted heat recuperated for re-use) and, in a separate step, comes into contact with steam, which reacts with oxygen vacancies to produce molecular hydrogen while recovering the original state of the metal oxide. Despite its promising use of the entire solar spectrum to split water thermochemically, the current estimated cost of hydrogen produced via STWS is ≈4-6× the U.S. Department of Energy (DOE) Hydrogen Shot target value of $1/kg. One contributing approach to bridging this cost gap is the design of new materials with improved thermodynamic properties to enable higher efficiencies. The state-of-the-art (SOA) redox-active metal oxide for STWS is ceria (CeO 2 ), due to its close to optimal, although too high, oxygen vacancy formation enthalpy and large configurational and electronic entropy of reduction. However, ceria requires high operating temperatures and its efficiency is insufficient. Therefore, efforts to increase the efficiency of STWS cycles have focused on further optimizing oxygen vacancy formation enthalpies and augmenting the reduction entropy via substitution or doping and materials discovery schemes. Examples of the latter include the perovskites BaCe 0.25 Mn 0.75 O 3 and (Ca,Ce)(Ti,Mn)O 3 . These efforts and others have revealed intuitive chemical principles for the efficient and systematic design of more effective materials, such as the strong correlation between the enthalpies of crystal bond dissociation and solid-state cation reduction with the enthalpy of oxygen vacancy formation, as well as configurational entropy augmentation via the coexistence of two or more redox-active cation sublattices. The purpose of this chapter is to prepare the reader with an up-to-date account of STWS redox-active materials, both the SOA and promising newcomers, as well as to provide chemically intuitive strategies for improving their cycle efficiencies through materials design – in conjunction with ongoing efforts in reactor engineering and gas separations – to reach the cost points for commercial viability. First, we will introduce the thermodynamics of STWS using a two-step, metal-oxide, thermochemical cycle with economics in mind. We also will compare the pros and cons of processes that do or do not involve phase changes. Second, we will describe the qualities that make ceria the SOA STWS redox-active material, as well as its limitations. Third, we will survey some of the most promising candidates to date in the search for materials to supplant ceria, emphasizing the post-ternary, metal-oxide-perovskite alloys. Lastly, we will enumerate and discuss the following materials design directions for STWS redox-active materials: crystal reduction potentials as a proxy for oxygen vacancy formation enthalpies, engineering the electronic and configurational entropy of reduction via f-shells and simultaneous redox, and vetting materials stability via temperature-dependent phase diagrams and melting-point prediction.

08 HYDROGEN↗
DOE OSTI2026

PV Lifetime Project - 2025 NLR Annual Report

DOE's PV Lifetime project was initiated in 2016 with the goal of accurately characterizing the early-life evolution of photovoltaic (PV) field performance. Different PV cell and module technologies result in different initial degradation rates due to effects like light-induced degradation (LID) and light and elevated temperature-induced degradation (LeTID). To accurately characterize the initial field degradation of maximum power (Pmp) requires the use of high-accuracy indoor IV curve measurements at standard test conditions. Therefore, PV modules involved in this study are removed from the field once or twice per year and brought indoors for measurement under constant temperature and irradiance conditions. Overall annual degradation rates are as follows: our first modules to be deployed (Jinko, Trina, QCells) have annual median degradation rate between -0.4%/yr and -0.5%/yr mainly concentrated in the first year. Mission Solar, LG and Panasonic modules are all displaying modest degradation, better than -0.3% / year. Indeed, Mission Solar fielded modules degraded less than their control modules which remain indoors and un-exposed. This is also true for the LONGi monofacial modules, which had some field degradation, but not as much as the degradation of the indoor control modules. The LONGi bifacial modules on the other hand have degraded more in the field than their monofacial counterparts, although still a modest amount (-0.4 %/yr). Of the four newest module types in the study, only one has had better than average degradation. REC360NP2 (N-type TOPCon) had a slight performance increase over the first year and a half of field deployment. For the other three new module types (plus one older module type), degradation was more rapid. In our study of 16 module types, four have demonstrated degradation faster than -1%/yr: two N-type Heterojunction, one PERC bifacial and one PERC shingled module. The two heterojunction modules in our study are degrading the most rapidly. Sunpreme n-HIT bifacial modules are showing a loss rate around -1.5%/yr, for over -10% total to date. This is largely attributed to loss in front-side Isc. This is distinct from the REC 405AA-Pure modules which have degraded -6.8% in only a year and a half, for an annualized decline of -3.9 %/yr. For this module type, the decline is roughly half in Voc, with the remaining split between FF and Isc. Of the remaining two module types, Prism Solar PERC bifacial has declined -5% total since 2019, although this loss appears to have stabilized in the most recent measurement. The Solaria PowerX-400R Shingled module type has also lost around -3.2% in the first 1.5 years of field deployment. It remains to be seen if these losses will continue with time.

14 SOLAR ENERGY↗
DOE OSTI2026

Power now, pay later: the evolution of U.S. residential solar financing

Most U.S. residential rooftop solar customers finance their solar purchases through loans or by buying power from third-party owned systems. Prior research demonstrates how third-party ownership (TPO) models such as leases emerged in the early 2010s and accelerated solar adoption by low- and moderate-income households while driving market concentration in the installation industry. Since 2015, loans have emerged as a prevalent financing alternative, but the potential effects of loans on the customer base and industry remain understudied. Here, we fill that research gap by developing a methodology to identify loan-financed and third-party owned systems in a household-level solar adopter data set. The data suggest that loans accounted for increasing solar market shares from 2017 until reaching as high as 70% in 2022, but that the market has since shifted back to TPO. The data show that TPO adopters in our sample earned about 16%–18% less and loan recipients earned 3%–7% less, at the median, than customers who self-financed systems. These results reaffirm prior research showing that TPO has accelerated low- and moderate-income adoption and that loans have likewise expanded the customer base to a lesser extent. The results suggest that loan-financed systems entail around a 16%–26% price premium that is only partly explained by loan fees. Finally, the data suggest that the emergence of loans has likely reduced market concentration in the rooftop solar industry.

financing↗
DOE OSTI2021

Renewable Thermal Energy Systems Designed for Industrial Process Solutions in Multiple Industries

The need for renewable heat in industry is vital for the next decade and beyond. Industrial decarbonization is a key area that must be accelerated, to foster the removal of fossil fuels from the provision of heat, especially at low temperatures. This paper looks at the development and results of case studies for understanding the economics and potential for renewable thermal energy systems (RTES), particularly in hybrid configurations to provide industrial process heat (IPH). For the case studies, these include non-concentrating e.g., heat pumps, and concentrating collectors e.g., parabolic trough collectors and direct steam generation (DSG)-linear Fresnel collectors (LFCs). The results show that a levelized cost of heat (LCOH) of $6-$8 per million British Thermal Units (MMBTU) is possible, depending on the direct normal irradiance (DNI) and the system sizing e.g., to increase the solar fractions. In Arizona for example, with a DNI of 7.36 kWh/m2/day, the base case for the DSG-LFC system with 6hrs of thermal energy storage could potentially meet a 1 MWth load 80% of the year.

concentrated solar thermal↗
DOE OSTI2023

GeoCarb Calibration Campaign Field Campaign Report

The GeoCarb Calibration Campaign, referred to as the Total Carbon Column Observing Network (TCCON) calibration campaign within this report for clarity, involved a series of single- and multiple-day Bruker EM27/SUN Fourier transform infrared (FTIR) spectrometer deployments at the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) user facility’s Southern Great Plains (SGP) observatory in Oklahoma. The EM27/SUN instruments directly measure infrared solar radiation in a wavelength range from 4000 to 11000 cm -1 at a spectral resolution of 0.5 cm -1 and varied temporal resolution of approximately 15 seconds. The solar radiation observed by these spectrometers contains information about the concentrations of atmospheric constituents present between the instruments and the top of the atmosphere, as every gas and particle in the atmosphere absorbs solar radiation at different wavelengths depending on their physical and chemical makeup. Through retrieval algorithm processing, the solar radiation data collected by EM27/SUN instruments can be used to infer total column dry-air mole fractions, or total column concentrations, of different trace gases present in the atmosphere. These total column concentrations, denoted as Xgas , represent the concentration, in ppb or ppm, of a trace gas in the column of atmosphere between an instrument and the top of the atmosphere. EM27/SUN instruments are primarily used to infer total column concentrations of carbon dioxide (CO 2 ), carbon monoxide (CO), methane (CH 4 ), and water vapor.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Enhanced Photostability of “Hollow” Mixed Halide Wide-Bandgap Perovskite Films

We investigated the role of hollow perovskite architectures in enhancing the photostability of mixed halide wide-bandgap perovskites. We focused on mitigating photoluminescence (PL) peak shifts caused by phase segregation when exposed to light. By analyzing the optical and structural properties of mixed bromide/iodide hollow perovskite thin films, we observed that the incorporation of hollow structures reduced the ionic conductivity in the films, leading to improved photostability compared to non-hollow perovskite samples. The mixed halide hollow perovskite thin films exhibited increased the bandgap. High-power laser irradiation was used to induce phase segregation, and changes in the PL emission spectra were measured as a function of irradiation time. The mixed halide hollow perovskite thin films exhibited reduced PL peak shifts compared to the control samples. The inclusion of enI 2 (en = ethylenediamine) resulted in a reduction in the overall ionic conductivity of the films and a lower trap density. Hollow perovskite films incorporated in solar cells indicated that while the initial efficiency of the solar cells decreased with increasing enI 2 concentration, the open-circuit voltage value increased, potentially due to the slight enhancement of the band gap. Furthermore, the findings highlight the potential of hollow perovskite architectures in enhancing the photostability of mixed halide perovskites

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

Meteorological Conditions and Atmospheric Components Concentration in Urban Sites in Knoxville, USA. 2024

This dataset, which contains five csv files, reports several meteorological conditions such as temperature, wind speed, solar radiation, and net radiation measured in Cumberland Estates Park (CEP) and Socially Equal Energy Efficient Development (SEEED) sites in Knoxville, Tennessee, USA. Also, hourly concentration of particulate matter (PM) with different aerodynamic diameter and inorganic gases such as ozone and nitrogen dioxide measured in the two are included in this dataset. The concentrations of PM and inorganic gases were monitored using the MODULAIR, a low-cost sensor equipped with a solar power module. The measurement of the concentration of biogenic and anthropogenic volatile organic compounds (VOCs) of the two sites was determined using a High-Resolution Proton Transfer Reaction Time of Flight Mass Spectrometer (PTR-ToF-MS). The VOCs were collected using miniature canister (400 mL) equipped with female RAVEqc valve to 1/4” male compression fitting and an integrated passive air sampling kit. This work is a part of a larger study which investigates the impact of soil moisture and plant evapotranspiration on ambient temperature and relative humidity in several city parks in Knoxville, Tennessee.

54 ENVIRONMENTAL SCIENCES↗