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At least 271 records · Page 15

Temperature-adaptive radiative coating for all-season household thermal regulation

The sky is a natural heat sink that has been extensively used for passive radiative cooling of households. A lot of focus has been on maximizing the radiative cooling power of roof coating in the hot daytime using static, cooling-optimized material properties. However, the resultant overcooling in cold night or winter times exacerbates the heating cost, especially in climates where heating dominates energy consumption. In this work, we approached thermal regulation from an all-season perspective by developing a mechanically flexible coating that adapts its thermal emittance to different ambient temperatures. The fabricated temperature-adaptive radiative coating (TARC) optimally absorbs the solar energy and automatically switches thermal emittance from 0.20 for ambient temperatures lower than 15°C to 0.90 for temperatures above 30°C, driven by a photonically amplified metal-insulator transition. Simulations show that this system outperforms existing roof coatings for energy saving in most climates, especially those with substantial seasonal variations.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

A Rule-Based Expert System Applied to Moisture Durability of Building Envelopes

The moisture durability of an envelope component such as a wall or roof is difficult to predict. Moisture durability depends on all the construction materials used, as well as the climate, orientation, air tightness, and indoor conditions. Modern building codes require more insulation and tighter construction but provide little guidance about how to ensure these energy-efficient assemblies remain moisture durable. Furthermore, as new products and materials are introduced, builders are increasingly uncertain about the long-term durability of their building envelope designs. Oak Ridge National Laboratory and the US Department of Energy's Building America Program are applying a rule-based expert system methodology in a web tool to help designers determine whether a given wall design is likely to be moisture durable and provide expert guidance on moisture risk management specific to a wall design and climate. The expert system is populated with knowledge from both expert judgment and probabilistic hygrothermal simulation results.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

Monitoring the Urban Heat Island Effect and the Efficacy of Future Countermeasures

To relate fine-scale spatial air-temperature variations in local urban heat islands and urban cool islands—increases and decreases in outside air temperature—within a large urban-climate archipelago to variations in land-use and land-cover properties in the Los Angeles Basin, the research team sought to (a) use fine-resolution meso-urban climate models to identify areas of urban heat and cool islands, select sites for fixed weather monitoring, and choose routes for mobile observations; (b) relate observed intraurban temperature variations to land use and land cover and surface physical properties; and (c) calibrate/validate the climate models. The research team assessed urban temperature variations via simulations and observations, including mobile transects, mesonet, dense networks of personal weather stations, and sparse but more accurate research-grade monitors. To identify the causative factors of the urban heat and cool islands at the neighborhood scale, the research team collected detailed urban morphometric and land use and land cover datasets, such as 1-meter (3.3 foot) resolution roof albedo (solar reflectance) and tree canopy cover. The research team used the observationvalidated model to finalize the transect routes and site the stationary monitors. This study provides the first observational evidence from analysis of high-spatial-density weather stations that increases in roof albedo at neighborhood scale are associated with reductions in near-surface air temperature. This finding was corroborated with the analysis from mobile transect measurements and correlation of observed air temperature with neighborhood-scale albedo and vegetation. This correlation revealed a cooling effect from areawide increase in albedo or canopy cover or both. The calibrated meteorological model accurately identified the localized urban heat and cool islands observed in this study. Interested stakeholders/researchers can use the same models and calibration/validation methodology to characterize within-city microclimate variations elsewhere in California, and can apply them to analyze the benefits from using urban heat island countermeasures. This project report is an extended and more detailed version of a related report prepared for California’s Fourth Climate Change Assessment.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

Moisture performance of sealed attics in the mixed-humid climate

Oak Ridge National Laboratory studied 8 homes in the mixed-humid climate, 4 with vented attics and 4 with sealed attics. ORNL wanted to understand the moisture performance of the sealed attic and how it affected the interior environment. We found that the attic and interior of sealed attic homes were more humid than the attic and interior observed in vented attic homes. This is due to the lack of ventilation in the sealed attic. Historically attics have been vented to dehumidify the attic and interior of the home. A sealed attic design greatly reduces the venting potential and thus this drying pathway and can cause elevated interior moisture over a vented attic home. Despite the elevated attic and interior moisture in the sealed attic homes, so far no mold or material degradation has been found. The roof sheathing moisture content has stayed below 20%, indicating low potential for material degradation. Also the relative humidity at the roof sheathing has stayed within the ASHRAE 160 design criteria except for a short time during the 2011/2012 winter. This was due to a combination of the sealed attic design (minimal venting to the outside) and the duct work not being operated in the attic which usually provides a dehumidification pathway. It was also found that when the humidity was controlled using the HVAC system, it resulted in 7% more cooling energy consumption. In the mixed-humid climate this reduces the cost effectiveness of the sealed attic design as a solution for bringing ducts into a semi-conditioned space. Because of this we are recommending the other alternatives be used to bringing ducts into the conditioned space in both new construction and retrofit work in the mixed-humid climate.

54 ENVIRONMENTAL SCIENCES↗

Structural Code Considerations for Solar Rooftop Installations

Residential rooftop solar panel installations are limited in part by the high cost of structural related code requirements for field installation. Permitting solar installations is difficult because there is a belief among residential permitting authorities that typical residential rooftops may be structurally inadequate to support the additional load associated with a photovoltaic (PV) solar installation. Typical engineering methods utilized to calculate stresses on a roof structure involve simplifying assumptions that render a complex non-linear structure to a basic determinate beam. This method of analysis neglects the composite action of the entire roof structure, yielding a conservative analysis based on a rafter or top chord of a truss. Consequently, the analysis can result in an overly conservative structural analysis. A literature review was conducted to gain a better understanding of the conservative nature of the regulations and codes governing residential construction and the associated structural system calculations.

Dwyer, Stephen F.↗

Pecan Street Grid Demonstration Program. Final technology performance report

This document represents the final Regional Demonstration Project Technical Performance Report (TPR) for Pecan Street Inc.’s (Pecan Street) Smart Grid Demonstration Program, DE-OE-0000219. Pecan Street is a 501(c)(3) smart grid/clean energy research and development organization headquartered at The University of Texas at Austin (UT). Pecan Street worked in collaboration with Austin Energy, UT, Environmental Defense Fund (EDF), the City of Austin, the Austin Chamber of Commerce and selected consultants, contractors, and vendors to take a more detailed look at the energy load of residential and small commercial properties while the power industry is undergoing modernization. The Pecan Street Smart Grid Demonstration Program signed-up over 1,000 participants who are sharing their home or businesses’s electricity consumption data with the project via green button protocols, smart meters, and/or a home energy monitoring system (HEMS). Pecan Street completed the installation of HEMS in 750 homes and 25 commercial properties. The program provided incentives to increase the installed base of roof-top solar photovoltaic (PV) systems, plug-in electric vehicles with Level 2 charging, and smart appliances. Over 200 participants within a one square mile area took advantage of Austin Energy and Pecan Street’s joint PV incentive program and installed roof-top PV as part of this project. Of these homes, 69 purchased or leased an electric vehicle through Pecan Street’s PV rebate program and received a Level 2 charger from Pecan Street. Pecan Street studied the impacts of these technologies along with a variety of consumer behavior interventions, including pricing models, real-time feedback on energy use, incentive programs, and messaging, as well as the corresponding impacts on Austin Energy’s distribution assets.The primary demonstration site was the Mueller community in Austin, Texas. The Mueller development, located less than three miles from the Texas State Capitol, is a 711-acre LEED Neighborhood Development mixed-use, urban infill redevelopment on the site of Austin’s former airport, currently under development through a public-private project between the City of Austin, and Catellus Austin LLC. Currently, Mueller is less than 50% complete and more than 3,500 people live or work at Mueller. At full build-out, the project will include more than 3 million square feet of commercial and institutional space, more than 13,000 residents from approximately 5,700 single-family and multi-family dwelling units. Figure 1 shows a Google Map image of the Mueller community, zoomed in on the residential streets participating in the project.

24 POWER TRANSMISSION AND DISTRIBUTION↗

Neutron Generator Production Facility (NGPF), Building 870: Structural Fire Protection Analysis and Basis of Design Report

This report was prepared to provide an explanation of the prescriptive-based code approach for the Neutron Generator Production Facility’s (NGPF) structural fire protection and construction classification determinations based upon the original code-of-record (1991-UBC) and current International Building Code (2012-IBC) requirements. The code approach presented in this report included a determination of the required construction type in accordance with the 2012-IBC. Through the evaluation of the record design drawings and subsequent site surveys, a determination was made of the existing types of materials used to construct the columns, beams, floor assemblies, roof assembly, and exterior and interior walls and partitions. A summary is provided for the fire resistance requirements of the different elements of the building. In addition, a determination was made in regards to the fire resistance hourly ratings of the columns, beams, floor assemblies, roof assembly, exterior walls, interiors walls and partitions, door openings, joints and penetrations. Through design evaluation, site survey, code verification, and review of record documents, the actual construction classification (Type II-B) was confirmed to be compliant with the 2012-IBC.

42 ENGINEERING↗

Combined Aero and Underhood Thermal Analysis for Heavy Duty Trucks

Aerodynamic analysis of the medium-duty delivery truck was performed to achieve vehicle design optimization. Three dimensional CFD simulations were carried out for several improved designs, with a detailed external component analysis of wheel covers, side skirts, roof fairings, and rounded trailer corners. The overall averaged aerodynamics drag reduction through the design modifications were shown up to 22.3% through aerodynamic considerations alone, which is equivalent to 11.16% fuel savings. The main identified fuel efficiencies were based on second generation devices, including wheel covers, side skirts, roof fairings, and rounded trailer corners. The important findings of this work were; (i) the optimum curvature radius of the rounded trailer edges found to be 125 mm, with an arc length of 196.3 mm, (ii) aerodynamic drag reduction increases with dropping clearance of side skirts between wheels and ground, and (iii) aerodynamic drag reduction increases with an extension of front bumper towards the ground.

36 MATERIALS SCIENCE↗

Release Report for Building Debris for TA-21 Sewage Treatment Facility

ENV-ES finds that the materials associated with TA-21 Buildings 227 (superstructure only), and 229 (see Figure 1) meet the criteria for unrestricted release to the public for recycle or as sanitary/commercial waste. The interior and exterior of the metal shed, building 387, passed the release criteria collectively; however, results from the roof of the structure were above reference background measurements. Waste management should be consulted for waste disposition options for the roofing metal. These findings are consistent with the requirements of DOE Order 458.1 “Radiation Protection of the Public and the Environment” and LANL Policy 412 “Environmental Radiation Protection.” Sampling and data analysis, as described in this report, were sufficient to meet measurement objectives under the Multi-Agency Radiation Survey and Assessment of Materials and Equipment (MARSAME) manual (2009).

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

Facilitating Deployment of Community Solar PV systems on Rooftops and Vacant Land in Northeast IL - Final Report

The Cook County Community Solar project set out to unlock the potential of community solar in the Chicago region with lessons that could be applied nationally. One of the first steps was to prove out the potential market. This was done through an opportunity assessment which showed there is over 9,000 megawatts worth of site capacity available for community solar projects in Cook County – nearly enough to offset all of Cook County’s residential electricity use. The assessment also showed that almost 75% of Cook County households are not able to invest directly in solar photovoltaic systems due to a variety of issues from physical barriers such as shading, or condition of the roof, to financial barriers such as lack of roof ownership, or the up-front costs of installation. Because of these barriers, community solar is an essential part of making the benefits of renewable energy available to all of the residents of Cook County. In addition to the opportunity assessment the project team also worked with the over 200 individuals who participated in the stakeholder advisory group to develop a number of other products including: 1) an Economic & Policy Barriers Resolutions and Work Plan document which laid out best practices to address the policy barriers that existed at the time (May of 2016) 2) Value Proposition Report I and Report II which summarize the value of community solar to potential developers and subscribers, 3) The Community Solar Business Case Tool, which provides a flexible financial model that projects the costs and befits to the system developer and subscriber for a project, 4) Bill Crediting Analysis and the 5) Final Report. The Final Report contains 15 case studies which prove that community solar projects are economically feasible in Cook County with a variety of sites, solar designs, ownership and subscriber models.

14 SOLAR ENERGY↗

Cost-Reduction Roadmap for Residential Solar Photovoltaics (PV), 2017-2030

The installed cost of solar photovoltaics (PV) has fallen rapidly in recent years and is expected to continue declining in the future. In this report, we focus on the potential for continued PV cost reductions in the residential market. From 2010 to 2017, the levelized cost of energy (LCOE) for residential PV declined from 52 cents per kilowatt-hour (cents/kWh) to 16 cents/kWh (Fu et al. 2017). The U.S. Department of Energy's (DOE's) Solar Energy Technologies Office (SETO) recently set new LCOE targets for 2030, including a target of 5 cents/kWh for residential PV. We present a roadmap for achieving the SETO 2030 residential PV target. Because the 2030 target likely will not be achieved under business-as-usual trends (NREL 2017), we examine two key market segments that demonstrate significant opportunities for cost savings and market growth: installing PV at the time of roof replacement and installing PV as part of the new home construction process. Within both market segments, we identify four key cost-reduction opportunities: market maturation, business model integration, product innovation, and economies of scale. To assess the potential impact of these cost reductions, we compare modeled residential PV system prices in 2030 to the National Renewable Energy Laboratory's (NREL's) quarter one 2017 (Q1 2017) residential PV system price benchmark (Fu et al. 2017). We use a bottom-up accounting framework to model all component and project-development costs incurred when installing a PV system. The result is a granular accounting for 11 direct and indirect costs associated with installing a residential PV system in 2030. All four modeled pathways demonstrate significant installed-system price savings over the Q1 2017 benchmark, with the visionary pathways yielding the greatest price benefits. The largest modeled cost savings are in the supply chain, sales and marketing, overhead, and installation labor cost categories. When we translate these installed-system costs into LCOE, we find that the less-aggressive pathways achieve significant cost reductions, but may not achieve the 2030 LCOE target. On the other hand, both visionary pathways could get very close to (for roof replacement) or achieve (for new construction) the 2030 target. Our analysis has two key implications. First, because installed-system soft cost reductions account for about 65 percent of the LCOE reductions in 2030 for both visionary pathways, residential PV stakeholders may need to emphasize these soft cost reductions to achieve the 2030 target. Second, capturing these savings will likely require considerable innovation in the technologies and business practices employed by the PV industry.

14 SOLAR ENERGY↗

Analyzing the Energy Performance, Wind Loading, and Costs of Photovoltaic Slat Modules on Commercial Rooftops

NREL studied a new type of photovoltaic (PV) module configuration wherein multiple narrow, tilted slats are mounted in a single frame. Each slat of the PV slat module contains a single row of cells and is made using ordinary crystalline silicon PV module materials and processes, including a glass front sheet and weatherproof polymer encapsulation. Compared to a conventional ballasted system, a system using slat modules offer higher energy production and lower weight at lower LCOE. The key benefits of slat modules are reduced wind loading, improved capacity factor and reduced installation cost. First, the individual slats allow air to flow through, which reduce wind loading. Using PV performance modeling software, we compared the performance of an optimized installation of slats modules to a typical installation of conventional modules in a ballasted rack mounting system. Based on the results of the performance modeling two different row tilt and spacing were tested in a wind tunnel. Scaled models of the PV Slat modules were wind tunnel tested to quantify the wind loading of a slat module system on a commercial rooftop, comparing the results to conventional ballasted rack mounted PV modules. Some commercial roofs do not have sufficient reserve dead load capacity to accommodate a ballasted system. A reduced ballast system design could make PV system installation on these roofs feasible for the first time without accepting the disadvantages of penetrating mounts. Finally, technoeconomic analysis was conducted to enable an economic comparison between a conventional commercial rooftop system and a reduced-ballast slat module installation.

14 SOLAR ENERGY↗

Thermosyphon Cooler Hybrid System for Water Savings in an Energy-Efficient HPC Data Center: Results from 24 Months and the Impact on Water Usage Effectiveness

In August 2016, the National Renewable Energy Laboratory (NREL) installed a thermosyphon hybrid cooling system to reduce water usage in its already extremely energy-efficient High-Performance Computing (HPC) Data Center. In its first year of use, the system saved 4,400 m3 (1.16 million gal) of water, and 7,950 m3 (2.10 million gal) during a 2-year period, cutting the use of water in the data center by about one-half. NREL's 930-m2 (10,000-ft2) HPC Data Center is often called the most energy-efficient data center in the world: it has achieved a trailing 12-month average power usage effectiveness of 1.034, and it features a chiller-less design, component-level warm-water liquid cooling, and waste heat capture and reuse. NREL considered the amount of water used by the cooling towers to be counter to the laboratory's sustainability mission, so a team of researchers from NREL, Sandia National Laboratories (Sandia), and Johnson Controls integrated the BlueStream thermosyphon cooler (TSC) - an advanced dry cooler that uses refrigerant in a passive cycle to dissipate heat - on the roof of NREL's Energy Systems Integration Facility, the building that houses the HPC Data Center. In combination with the existing cooling towers, the TSC forms an extremely water- and cost-efficient cooling system. In its first year of operation, on-site water usage effectiveness (WUE) was 0.70 L/kWh. In comparison, the WUE would be 1.27 L/kWh if NREL had continued using only heat-recovery and cooling towers. This on-site water savings was accomplished without negatively impacting the energy-efficient operation of the HPC Data Center. The TSC system technology has the potential for application in data centers around the world, and it is currently being implemented by Sandia. center by about one-half. NREL's 930-m2 (10,000-ft2) HPC Data Center is often called the most energy-efficient data center in the world: it has achieved a trailing 12-month average power usage effectiveness of 1.034, and it features a chiller-less design, component-level warm-water liquid cooling, and waste heat capture and reuse. NREL considered the amount of water used by the cooling towers to be counter to the laboratory's sustainability mission, so a team of researchers from NREL, Sandia National Laboratories (Sandia), and Johnson Controls integrated the BlueStream thermosyphon cooler (TSC) - an advanced dry cooler that uses refrigerant in a passive cycle to dissipate heat - on the roof of NREL's Energy Systems Integration Facility, the building that houses the HPC Data Center. In combination with the existing cooling towers, the TSC forms an extremely water- and cost-efficient cooling system. In its first year of operation, on-site water usage effectiveness (WUE) was 0.70 L/kWh. In comparison, the WUE would be 1.27 L/kWh if NREL had continued using only heat-recovery and cooling towers. This on-site water savings was accomplished without negatively impacting the energy-efficient operation of the HPC Data Center. The TSC system technology has the potential for application in data centers around the world, and it is currently being implemented by Sandia.

97 MATHEMATICS AND COMPUTING↗

LANL HDZoom Camera Troubleshooting [Slides]

Photo progression grid flight over white roof– HDZoom, photo progression grid flight over white roof – EO/IR and photo progression circular flight – HDZoom.

42 ENGINEERING↗

San Diego Tribal Energy Collaborative [Slides]

The project involves the installation and activation of 42 roof-top or ground mount solar photovoltaic systems. The system will use a combination of roof-top photovoltaic panels and ground-mounted panels that will be installed on 40 tribal homes and 2 tribal buildings throughout the three participating reservations. The scope of work includes site preparation, equipment installation, system testing, and inspection by a third-party inspector, system activation, troubleshooting, and final activation. It also includes any electrical system upgrades, which are anticipated to accommodate the new PV system. The system will displace at least 50% of the combined total of electricity needed by the participating structures. Implementing these systems will also provide hands-on solar installation training to at least 20 Tribal community volunteers and job trainees.

14 SOLAR ENERGY↗

White Earth Community Facilities Solar PV Project (Final Report)

Funded project was for the design, installation, and performance monitoring of 2 - 11.4 kW AC and 1-38.0 kW AC ground-mount solar installations for three tribal community facilities, for a total 60.8 kW AC, including a daycare facility and two community centers. Of in excess of 120 tribal buildings these facilities had showed the best promise for implementing solar, based upon site characteristics, roof loads, roof orientation and building size. The White Earth Nation seeks to move forward proactively to address the following project goals and objectives: 1) Reduction of energy costs, 2) Increasing energy security for Indian Tribes and tribal members, 3) Adding 60.8 KW in renewable energy generation (solar PV), 4) Offsets, reduces coal-fired electric energy demand by 76,397 kWh, 817,448 Source Energy Btu annually, and S) Meets the overall solar PV target set in the FOA.

14 SOLAR ENERGY↗

Low-Cost Preform and Molding Processes

The entry cost for prototyping a composite component for manufacture using automated, high rate processes is prohibitively expensive in many cases, especially for small business, where tooling costs may be several $100k. Discussions with industry also indicate that many small companies, tier 1 and 2 suppliers, have an interest to mold composite parts but do not want to deal with the capital cost, material handling issues, and labor associated with dry fiber preforming operations. While the molders may locate near the end user for logistics reasons, it may be more cost effective for the performer to remain regional and invest in capital equipment to support preform automation, thus keeping costs to a minimum. This project was designed to explore and demonstrate several options to meet these industry needs. Dry fiber preforming approaches were evaluated which allow for low pressure resin infusion, single sided tooling options such a vacuum assisted resin transfer molding (VARTM) or low pressure resin transfer molding (RTM-light). Unlike sheet molding compound, SMC compression molding where typical molding pressures of 1000 psi are required to push material into the desired location; positioning of a dry fiber preform into the desired location on the tool allows for low molding pressures of 10-50 psi. Lower molding pressures allow for use of low cost, additive fabrication of polymeric tooling. Polymeric tooling is suitable for rapid part prototyping and limited production. Dry fiber preforming approaches evaluated included use of commercial chopped strand mat, robotic chopper gun deposition, and continuous fiber preform augmentation using tailored fiber placement (TFP). Use of chopped strand mat does not require a robotic deposition method, however a cutting table is generally required and there is typically 20-30% scrap generation. While various fiber areal weights are available, the preform is not readily optimized for minimal fiber use or weight savings. In contrast, a robotic chopper gun approach allows for localized deposition where fiber is required to meet structural requirements. The robotic method is highly automated and minimizes fiber scrap, however the capital cost of the equipment and engineering labor for programming can result in higher preform cost compared to chopped strand mat in certain cases depending on preform complexity. Dry fiber preforming using the robotic chopper gun method allows for creation of three dimensional forms. This approach may be ideal for molding in-house, or if the preforms stack together densely to allow for efficient shipping. Applications evaluated for this program considered trade-off between fabrication of a fully 3D preform versus production of a flat preform which is designed to readily drape into the final desired shape. Such a preform design greatly simplifies robotic programming and requires no specialized tooling. The flat preforms are easily stacked and shipped to the final molding location. Flat preforms are much easier to augment with TFP continuous fiber to provide local reinforcement. The demonstration and evaluation of these preforming and tooling methods were completed on three component applications. The first application was a battery box cover for an electric vehicle which was highly three dimensional. The second demonstrator article was comprised of complex contours and was used to demonstrate the use of TFP and RTM-light molding process. The third demonstration article was the roof of an operator’s cab for large construction equipment. The roof is relatively flat however it is comprised of complex changes in thickness which clearly demonstrate the advantage of robotic chopper gun approach as compared to using numerous preform layers of chopped strand mat. The cost trades for the various preforming methods are summarized to help guide the reader as to preforming method considerations. Finally, these demonstrations all used glass fiber roving. A fourth, exploratory task was added to evaluate the ability to make preforms using Zoltek’s carbon fiber split tow roving. We were able to adapt the chopper gun to make flat preforms for laminate testing, but further development effort would be required to make suitable preforms.

36 MATERIALS SCIENCE↗

Analysis of Photovoltaic Energy: CRADA Number CRD-21-17862 (Cooperative Research and Development Final Report)

For this project, NREL will work with the Participant to model phase change material performance, model photovoltaic thermodynamics performance, and predict photovoltaic module durability based on environmental conditions to help develop optimized photovoltaic roofing designs. This project will develop thermodynamic models of integrated photovoltaic roofing with phase change materials. These models will be used to optimize the materials and design selections based on reducing photovoltaic operating temperatures while balancing cost effective integration of phase change materials.

14 SOLAR ENERGY↗