The NVBL Viral Fate and Transport Team includes researchers from eleven DOE national laboratories and is utilizing unique experimental facilities combined with physics-based and data-driven modeling and simulation to study the transmission, transport, and fate of SARSCoV-2. The team was focused on understanding and ultimately predicting SARS-CoV-2 viability in varied environments with the goal of rapidly informing strategies that guide the nation’s resumption of normal activities. The primary goals of this project include prioritizing administrative and engineering controls that reduce the risk of SARS-CoV-2 transmission within an enclosed environment; identifying the chemical and physical properties that influence binding of SARS-CoV-2 to common surfaces; and understanding the contribution of environmental reservoirs and conditions on transmission and resurgence of SARS-CoV-2.
High-temperature particle receivers are being pursued to enable next-generation concentrating solar thermal power (CSP) systems that can achieve higher temperatures (> 700 °C) to enable more efficient power cycles, lower overall system costs, and emerging CSP-based process-heat applications. The objective of this work was to develop characterization methods to quantify the particle and heat losses from the open aperture of the particle receiver. Novel camera- based imaging methods were developed and applied to both laboratory-scale and larger 1 MWt on-sun tests at the National Solar Thermal Test Facility in Albuquerque, New Mexico. Validation of the imaging methods was performed using gravimetric and calorimetric methods. In addition, conventional particle-sampling methods using volumetric particle-air samplers were applied to the on-sun tests to compare particle emission rates with regulatory standards for worker safety and pollution. Novel particle sampling methods using 3-D printed tipping buckets and tethered balloons were also developed and applied to the on-sun particle-receiver tests. Finally, models were developed to simulate the impact of particle size and wind on particle emissions and concentrations as a function of location. Results showed that particle emissions and concentrations were well below regulatory standards for worker safety and pollution. In addition, estimated particle temperatures and advective heat losses from the camera-based imaging methods correlated well with measured values during the on-sun tests.
An integrated modeling approach has been developed to better understand the relative impacts of different expiratory and environmental factors on airborne pathogen transport and transmission, motivated by the recent COVID-19 pandemic. Computational fluid dynamics (CFD) modeling was used to simulate spatial-temporal aerosol concentrations and quantified risks of exposure as a function of separation distance, exposure duration, environmental conditions (e.g., airflow/ventilation), and face coverings. The CFD results were combined with infectivity models to determine probability of infection, which is a function of the spatial-temporal aerosol concentrations, viral load, infectivity rate, viral viability, lung-deposition probability, and inhalation rate. Uncertainty distributions were determined for these parameters from the literature. Probabilistic analyses were performed to determine cumulative distributions of infection probabilities and to determine the most important parameters impacting transmission. This modeling approach has relevance to both pathogen and pollutant dispersion from expelled aerosol plumes.
This paper describes a terrestrial thermocline storage system comprised of inexpensive rock, gravel, and/or sand-like materials to store high-temperature heat for days to months. The present system seeks to overcome past challenges of thermocline storage (cost and performance) by utilizing a confined radialbased thermocline storage system that can better control the flow and temperature distribution in a bed of porous materials with one or more layers or zones of different particle sizes, materials, and injection/extraction wells. Air is used as the heat-transfer fluid, and the storage bed can be heated or "trickle charged"by flowing hot air through multiple wells during periods of low electricity demand using electrical heating or heat from a solar thermal plant. This terrestrial-based storage system can provide low-cost, large-capacity energy storage for both high- (∼400- 800°C) and low- (∼100-400°C) temperature applications. Bench-scale experiments were conducted, and computational fluid dynamics (CFD) simulations were performed to verify models and improve understanding of relevant features and processes that impact the performance of the radial thermocline storage system. Sensitivity studies were performed using the CFD model to investigate the impact o f the air flow rate, porosity, particle thermal conductivity, and air-to-particle heattransfer coefficient on temperature profiles. A preliminary technoeconomic analysis was also performed to estimate the levelized cost of storage for different storage durations and discharging scenarios.
This paper describes a terrestrial thermocline storage system comprised of inexpensive rock, gravel, and/or sand-like materials to store high-temperature heat for days to months. The present system seeks to overcome past challenges of thermocline storage (cost and performance) by utilizing a confined radialbased thermocline storage system that can better control the flow and temperature distribution in a bed of porous materials with one or more layers or zones of different particle sizes, materials, and injection/extraction wells. Air is used as the heat-transfer fluid, and the storage bed can be heated or "trickle charged"by flowing hot air through multiple wells during periods of low electricity demand using electrical heating or heat from a solar thermal plant. This terrestrial-based storage system can provide low-cost, large-capacity energy storage for both high- (∼400- 800°C) and low- (∼100-400°C) temperature applications. Bench-scale experiments were conducted, and computational fluid dynamics (CFD) simulations were performed to verify models and improve understanding of relevant features and processes that impact the performance of the radial thermocline storage system. Sensitivity studies were performed using the CFD model to investigate the impact o f the air flow rate, porosity, particle thermal conductivity, and air-to-particle heattransfer coefficient on temperature profiles. A preliminary technoeconomic analysis was also performed to estimate the levelized cost of storage for different storage durations and discharging scenarios.
Computational fluid dynamics (CFD) modelling was performed to simulate spatial and temporal airborne pathogen concentrations during an observed COVID-19 outbreak in a restaurant in Guangzhou, China. The reported seating configuration, overlap durations, room ventilation, layout, and dimensions were modelled in the CFD simulations to determine relative exposures and probabilities of infection. Results showed that the trends in the simulated probabilities of infection were consistent with the observed rates of infection at each of the tables surrounding the index patient. Alternative configurations that investigated different boundary conditions and ventilation conditions were also simulated. Increasing the fresh-air percentage to 10%, 50%, and 100% of the supply air reduced the accumulated pathogen mass in the room by an average of ∼30%, ∼70%, and ∼80%, respectively, over 73 min. The probability of infection was reduced by ∼10%, 40%, and 50%, respectively. Highlights: Computational fluid dynamics (CFD) models used to simulate pathogen concentrations Infection model developed using spatial and temporal CFD results Simulating spatial variability was important to match observed infection rates Recirculation increased exposures and probability of infection Increased fresh-air ventilation decreased exposures and probability of infection.
This paper describes the development of a facility for evaluating the performance of small-scale particle-to-sCO2 heat exchangers, which includes an isobaric sCO2 flow loop and an electrically heated particle flow loop. The particle flow loop is capable of delivering up to 60 kW of heat at a temperature of 600°C and flow rate of 0.4 kg/s. The loop was developed to facilitate long duration off-sun testing of small prototype heat exchangers to produce model validation data at steady-state operating conditions. Lessons learned on instrumentation, control, and system integration from prior testing of larger heat exchangers with solar thermal input were used to guide the design of the test facility. In addition, the development and testing of a novel 20-kWt moving packed-bed particle-to-sCO2 heat exchanger using the integrated flow loops is reported. The prototype heat exchanger implements many novel features for increasing thermal performance and reducing pressure drop which include integral porting of the sCO2 flow, unique bond/braze manufacturing, narrow plate spacing, and pure counter-flow arrangement. The experimental data collected for the prototype heat exchanger was compared to model predictions to verify the sizing, thermal performance, and pressure drop which will be extended to multi-megawatt heat exchanger designs in the future.
High-temperature falling particle receivers are being investigated for next-generation concentrating solar power applications. Small sand-like particles are released into an open-cavity receiver and are irradiated by concentrated sunlight from a field of heliostats. The particles are heated to temperatures over 700 °C and can be stored to produce heat for electricity generation or industrial applications when needed. As the particles fall through the receiver, particles and particulate fragments in the form of aerosolized dust can be emitted from the aperture, which can lower thermal efficiency, increase costs of particle replacement, and pose a particulate matter (PM) inhalation risk. This paper describes sampling methods that were deployed during on-sun tests to record nearfield (several meters) and far-field (tens to hundreds of meters) concentrations of aerosol particles within emitted plumes. The objective was to quantify the particulate emission rates and loss from the falling particle receiver in relation to OSHA and EPA National Ambient Air Quality Standards (NAAQS). Near-field instrumentation placed on the platform in proximity to the receiver aperture included several real-time aerosol size distribution and concentration measurement techniques, including a TSI Aerodynamic Particle Sizers (APS), TSI DustTraks, Handix Portable Optical Particle Spectrometers (POPS), Alphasense Optical Particle Counters (OPC), TSI Condensation Particle Counters (CPC), Cascade Particle Impactors, 3D-printed prototype tipping buckets, and meteorological instrumentation. Far-field particle sampling techniques utilized multiple tethered balloons located upwind and downwind of the particle receiver to measure the advected plume concentrations using a suite of airborne aerosol and meteorological instruments including POPS, CPCs, OPCs and cascade impactors. The combined aerosol size distribution for all these instruments spanned particle sizes from 0.02 μm - 500 μm. Results showed a strong influence of wind direction on particle emissions and concentration, with preliminary results showing representative concentrations below both the OSHA and NAAQS standards.
The National Solar Thermal Test Facility (NSTTF) at Sandia National Laboratories New Mexico (SNL/NM) developed this Project Execution Plan (PEP) to document its process for executing, monitoring, controlling and closing-out Phase 3 of the Gen 3 Particle Pilot Plant G3P3. This plan serves as a resource for stakeholders who wish to be knowledgeable of project objectives and how they will be accomplished. The plan is intended to be used by the development partners, principal investigator, and the federal project director. Project objectives are derived from the mission needs statement, and an integrated project team assists in development of the PEP. This plan is a living document and will be updated throughout the project to describe current and future processes and procedures. The scope of the PEP covers: Cost, schedule, and scope Project reporting Staffing plan Quality assurance plan Environment, safety, security, and health This document is a tailored approach for the Facilities Management and Operations Center (FMOC) to meet the project management principles of DOE Order 413.3B, Program and Project Management for the Acquisition of Capital Assets , and DOE G 413.3-15, DOE Guide for Project Execution Plans. This document will elaborate on content as knowledge of the project is gained or refined.
Two active airflow control methods are investigated to mitigate advective and particle losses from the open aperture of a falling particle receiver. Advective losses can be reduced via active airflow methods. However, in the case of once-through suction, energy lost as enthalpy of hot air due to active airflow needs to be minimized so that thermal efficiency can be maximized. In the case of forced air injection, a properly configured aerowindow can reduce advective losses substantially for calm conditions. Although some improvement is offered in windy conditions, an aerowindow in the presence of winds does not show an ability to mitigate advective losses to values achievable by an aerowindow in the absence of wind. The two active airflow methods considered in this paper both show potential for efficiency improvement, but the improvement many not be justified given the added complexity and cost of implementing an active airflow system. While active airflow methods are tractable for a 1 MWth cavity receiver with a 1 m square aperture, the scalability of these active airflow methods is questionable when considering commercial scale receivers with 10–20 m square apertures or larger.
Particle emissions from a high-temperature falling particle receiver with an open aperture were modeled using computational and analytical methods and compared to U.S. particle-emissions standards to assess potential pollution and health hazards. The modeling was performed subsequent to previous on-sun testing and air sampling that did not collect significant particle concentrations at discrete locations near the tower, but the impacts of wind on collection efficiency, especial for small particles less than 10 microns, were uncertain. The emissions of both large (~350 microns) and small (<10 microns) particles were modeled for a large-scale (100 MWe) particle receiver system using expected emission rates based on previous testing and meteorological conditions for Albuquerque, New Mexico. Results showed that the expected emission rates yielded particle concentrations that were significantly less than either the pollution or inhalation metrics of 12 Pg/m3 (averaged annually) and 15 mg/m3, respectively. Particle emission rates would have to increase by a factor of ~400 (~0.1 kg/s) to begin approaching the most stringent standards.
A strategy to optimize the thermal efficiency of falling particle receivers (FPRs) in concentrating solar power applications is described in this paper. FPRs are a critical component of a falling particle system, and receiver designs with high thermal efficiencies (~90%) for particle outlet temperatures > 700°C have been targeted for next generation systems. Advective losses are one of the most significant loss mechanisms for FPRs. Hence, this optimization aims to find receiver geometries that passively minimize these losses. The optimization strategy consists of a series of simulations varying different geometric parameters on a conceptual receiver design for the Generation 3 Particle Pilot Plant (G3P3) project using simplified CFD models to model the flow. A linear polynomial surrogate model was fit to the resulting data set, and a global optimization routine was then executed on the surrogate to reveal an optimized receiver geometry that minimized advective losses. This optimized receiver geometry was then evaluated with more rigorous CFD models, revealing a thermal efficiency of 86.9% for an average particle temperature increase of 193.6°C and advective losses less than 3.5% of the total incident thermal power in quiescent conditions.
Millions of dollars and significant resources are being spent by developers of utility-scale solar photovoltaic (PV) and concentrating solar power (CSP) plants to address federal and local requirements regarding glare and avian hazards. Solar glare can occur from the glass surfaces of PV modules and from mirrors in CSP systems, which can produce safety and health risks for pilots, motorists, and residents located near these systems. In addition, concentrated solar flux at CSP plants has the potential to singe birds as they fly through regions of high solar flux. This work will develop tools to characterize and mitigate these potential hazards, which will address regulatory policies and reduce costs and efforts associated with the proposed deployment of gigawatts of solar energy systems throughout the nation. The development of standardized and publicly available tools to address these regulatory policies and ensure public and environmental safety is an appropriate role for the government.
This work is developing particle flow control and measurement methods for next-generation concentrating solar power systems employing particle-based technologies. Particle receivers are being pursued to provide substantial performance improvements through higher temperatures (>700 °C) for more efficient and cost-effective CSP systems with direct storage for electricity generation, process heating, thermochemistry, and solar fuels production. This specific work will develop technologies that enable more efficient particle receivers and scalable methods to accommodate variable irradiances during commercial on-sun operation. The development of next-generation particle-receiver systems and methods with potentially high consequences for improved performance and cost savings for CSP applications is an appropriate role for the government.
Particle receivers are being pursued to provide substantial performance improvements through higher temperatures (>700 °C) for more efficient and cost-effective concentrating solar power (CSP) systems with direct storage. However, the interface between the solar-collection and power-block subsystems - a high-temperature particle/supercritical CO2 (sCO2) heat exchanger - has not been developed. The objective of this project is to design, construct, and test a first-of-a-kind particle-to-sCO2 heat exchanger. This work will enable emerging sCO2 power cycles that have the potential to meet SunShot targets of 50% thermal-to-electric efficiency, dry cooling with 40 °C ambient temperature, and $0.06/kWh for CSP systems. The development of next-generation particle-based systems and methods with potentially high consequences for improved performance and cost savings for CSP applications is an appropriate role for the government.
This report describes the design, development, and testing of a prototype 100 kWt particle-to-supercritical CO2 (sCO2) heat exchanger. An analytic hierarchy process was implemented to compare and evaluate alternative heat-exchanger designs (fluidized bed, shell-and-plate moving packed bed, and shell-and-tube moving packed bed) that could meet the high pressure (≥ 20 MPa) and high temperature (≥ 700 °C) operational requirements associated with sCO2 power cycles. Cost, heat-transfer coefficient, structural reliability, manufacturability, parasitics and heat losses, scalability, compatibility, erosion and corrosion, transient operation, and inspection ease were considered in the evaluation. A 100 kWt shell-and-plate design was selected for construction and integration with Sandia’s falling particle receiver system that heats the particles using concentrated sunlight. Sandia worked with industry to design and construct the moving packed-bed shell-and-plate heat exchanger. Tests were performed to evaluate its performance using both electrical heating and concentrated sunlight to heat the particles. Overall heat transfer coefficients at off-design conditions (reduced operating temperatures and only three stainless steel banks in the counter-crossflow heat exchanger) were measured to be approximately ~25 - 70 W/m2-K, significantly lower than simulated values of >100 W/m2-K. Tests using the falling particle receiver to heat the particles with concentrated sunlight yielded overall heat transfer coefficients of ~35 – 80 W/m2-K with four banks (including a nickel-alloy bank above the three stainless steel banks). The overall heat transfer coefficient was observed to decrease with increasing particle inlet temperatures, which contrasted the results of simulations that showed an increase in heat transfer coefficient with temperature due to increased effective particle-bed thermal conductivity from radiation. The likely cause of the discrepancy was particle-flow maldistributions and funnel flow within the heat exchanger caused by internal ledges and cross-bracing, which could have been exacerbated by increased particle-wall friction at higher temperatures. Additional heat loss at higher temperatures may also contribute to a lower overall heat-transfer coefficient. Design challenges including pressure drop, particle and sCO2 flow maldistribution, and reduced heat transfer coefficient are discussed with approaches for mitigation in future designs. Lessons learned regarding instrumentation, performance characterization, and operation of particle components and sCO2 flow loops are also discussed. Finally, a 200 MWt commercial-scale shell-and-plate heat-exchanger design based on the concepts investigated in this report is proposed.
Large-scale integration of energy storage on the electric grid will be essential to enabling greater penetration of intermittent renewable energy sources, modernizing the grid for increased flexibility security, reliability, and resilience, and enabling cleaner forms of transportation. The purpose of this report is to summarize Sandia's research and capabilities in energy storage and to provide a preliminary roadmap for future efforts in this area that can address the ongoing program needs of DOE and the nation. Mission and vision statements are first presented followed by an overview of the organizational structure at Sandia that provides support and activities in energy storage. Then, a summary of Sandia's energy storage capabilities is presented by technology, including battery storage and materials, power conversion and electronics, subsurface-based energy storage, thermal/thermochemical energy storage, hydrogen storage, data analytics/systems optimization/controls, safety of energy storage systems, and testing/demonstrations/model validation. A summary of identified gaps and needs is also presented for each technology and capability.