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

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At least 1,585 records · Page 88
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Analysis of Building Model Forecasts using Autonomous HVAC Optimization System for Residential Neighborhood

Heating, ventilation, and air conditioning (HVAC) systems account for the highest share of home energy consumption in the United States. Optimized HVAC control can provide thermal improved comfort to the occupants, improve energy efficiency, reduce energy cost, and support grid services. In this paper, we discuss a multi-agent and cloud-based software framework that has been deployed in occupied residential neighborhood. This system enables automatic data collection, learning, optimization, and dispatches signals to neighborhood devices. HVAC optimization is based on model predictive control (MPC). Since the operational performance of MPC depends on model forecasting accuracy, it is crucial to evaluate the model continuously and modify or retrain it as necessary. In this research, we developed an automated workflow to evaluate the performance of temperature and power forecasts based on measured data in the real world. This will provide researchers with a deeper understanding of the model and how it can be improved.

Lebakula, Viswadeep↗
NASA NTRS1996

CI Controls for Energy and Environment

Computational intelligence (CI) is a rapidly evolving field that utilizes life imitating metaphors for guiding model building including, but not limited to neural networks, fuzzy logic, genetic algorithms, artificial life, and hybrid CI paradigms. Although the boundaries between artificial intelligence (AI) and CI are not distinct, their research communities are separate and distinct. CI researchers tend to focus on processing numerical data from sensors, while the AI community generally relies on symbolic computing to capture human knowledge. In both areas, there is a great deal of interest and activity in hybrid systems that can offset the limitations of individual methods, extend their capabilities, and create new capabilities. Examples of the benefits that can accrue from hybrid systems are contained.

Biondo, Samuel J.↗
DOE OSTI2021

Integrated Framework of Vehicle Dynamics, Instabilities, Energy Models, and Sparse Flow Smoothing Controllers

This work presents an integrated framework of: vehicle dynamics models, with a particular attention to instabilities and traffic waves; vehicle energy models, with particular attention to accurate energy values for strongly unsteady driving profiles; and sparse Lagrangian controls via automated vehicles, with a focus on controls that can be executed via existing technology such as adaptive cruise control systems. This framework serves as a key building block in developing control strategies for human-in-the-loop traffic flow smoothing on real highways. In this contribution, we outline the fundamental merits of integrating vehicle dynamics and energy modeling into a single framework, and we demonstrate the energy impact of sparse flow smoothing controllers via simulation results.

Lee, Jonathan W.↗
DOE OSTI2016

Galaxies in X-Ray Selected Clusters and Groups in Dark Energy Survey Data. I. Stellar Mass Growth of Bright Central Galaxies Since z ~ 1.2

Using the science verification data of the Dark Energy Survey for a new sample of 106 X-ray selected clusters and groups, we study the stellar mass growth of bright central galaxies (BCGs) since redshift z ~ 1.2. Compared with the expectation in a semi-analytical model applied to the Millennium Simulation, the observed BCGs become under-massive/under-luminous with decreasing redshift. Here, we incorporate the uncertainties associated with cluster mass, redshift, and BCG stellar mass measurements into an analysis of a redshift-dependent BCG-cluster mass relation, $m_*$ $∝ \huge{(}$$\frac{M_{200}}{1.5x10^{14}M_⊙}\huge{)}$$^{0.24±0.08}$ $(1 + z)$$^{-0.19±0.34}$, and compare the observed relation to the model prediction. We estimate the average growth rate since z = 1.0 for BCGs hosted by clusters of M 200,z = 10 13.8 M ⊙ ; at z = 1.0: m * , BCG appears to have grown by 0.13 ± 0.11 dex, in tension at the ~2.5σ significance level with the 0.40 dex growth rate expected from the semi-analytic model. We show that the build-up of extended intracluster light after z = 1.0 may alleviate this tension in BCG growth rates.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Time Step Considerations when Simulating Dynamic Behavior of High Performance Homes

Building energy simulations, especially those concerning pre-cooling strategies and cooling/heating peak demand management, require careful analysis and detailed understanding of building characteristics. Accurate modeling of the building thermal response and material properties for thermally massive walls or advanced materials like phase change materials (PCMs) are critically important.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
NASA NTRS2014

State-to-State Internal Energy Relaxation Following the Quantum-Kinetic Model in DSMC

A new model for chemical reactions, the Quantum-Kinetic (Q-K) model of Bird, has recently been introduced that does not depend on macroscopic rate equations or values of local flow field data. Subsequently, the Q-K model has been extended to include reactions involving charged species and electronic energy level transitions. Although this is a phenomenological model, it has been shown to accurately reproduce both equilibrium and non-equilibrium reaction rates. The usefulness of this model becomes clear as local flow conditions either exceed the conditions used to build previous models or when they depart from an equilibrium distribution. Presently, the applicability of the relaxation technique is investigated for the vibrational internal energy mode. The Forced Harmonic Oscillator (FHO) theory for vibrational energy level transitions is combined with the Q-K energy level transition model to accurately reproduce energy level transitions at a reduced computational cost compared to the older FHO models.

Liechty, Derek S.↗
DOE OSTI2018

Distributed Energy Resources Customer Adoption Model (DER-CAM) v5.9

The Distributed Energy Resources Customer Adoption Model (DER-CAM) is a powerful and comprehensive decision support tool that primarily serves the purpose of finding optimal distributed energy resource (DER) investments in the context of either buildings or multi-energy microgrids. Version 5.9 introduces significant advancements to DER-CAM, including support for wholesale market integration (ancillary services), storage aging effects, improved solar thermal collector modeling, improved part-load efficiency modeling for conventional generators, added support for hydro generation, among others.

Deforest, Nicholas↗
DOE OSTI2020

Scheduling and Control of Flexible Building Loads for Grid Services Based on a Virtual Battery Model

This paper presents a framework for modeling, scheduling, and controlling residential thermostatically controlled loads (TCLs) to provide multiple grid services, such as energy shifting, peak load reduction, and ancillary services. A modeling method is proposed to characterize the aggregate flexibility from heterogeneous TCLs using a battery-equivalent model. Based on the flexibility model, a multi-period optimal scheduling formulation is developed to best utilize the flexibility from building loads and maximize total benefits from stacked value streams. An algorithm is proposed to control individual TCLs to follow the desired power consumption in real-time. The proposed methods are illustrated and validated through simulations.

Wu, Di↗
DOE OSTI2022

Utilizing commercial heating, ventilating, and air conditioning systems to provide grid services: A review

The modern power grid faces multiple challenges due to an increase in the adoption of renewable generation, such as dynamically balancing supply and demand at different time scales. Demand side management in buildings plays a vital role in achieving this balance because buildings can provide grid services through a variety of building assets. However, the development of grid-interactive, efficient buildings is still in its infancy, and a systematic and holistic understanding of grid service delivery strategies in terms of energy efficiency, load shifting, load shedding and load modulating is still limited. This paper is a comprehensive review of the development and application of building-level control strategies for utilizing heating, ventilating, and air conditioning systems to provide grid services. These strategies have been investigated through numerical and experimental studies. Control algorithms, such as heuristic rule-based control and model-based control, have been used to enable the automatic control delivery of grid services. The advantages and disadvantages of the strategies are summarized and discussed. Finally, research trends are also identified, which include considering predicted mean vote-based and occupant-based thermal comfort, modeling of occupant behavior, integrating power grid operations with building control, and combining different demand flexibility modes in the control design.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2020

Dynamic Modelling and Performance Evaluation of a Chemisorption Heat Pump for Cold Climate

Space heating is a significant contributor to the energy consumption in residential buildings, especially in cold climates where electric-driven heat pumps lose the advantage of high efficiency and conventional gas-combustion furnaces have limited efficiency. Chemical adsorption (chemisorption) heat pumps (CSHP) have the potential for producing heating with high energy efficiency under cold operating conditions. A CSHP operates intermittently between desorption and adsorption modes, and their performance is affected by system design and transient system control. This study developed a dynamic model and used it to evaluate the daily system performance under different designs and controls, particularly the buffer tank size and the controlled minimum heating power. The simulation results revealed the effects of these parameters on the system performance and helped identify the optimal design and control for the highest coefficient of performance and heating capacity.

Yang, Zhiyao↗
DOE OSTI2020

Paving the Way for Net Zero Energy Codes through Performance Based Approaches

The prescriptive path is the most widely used approach for commercial code compliance in the United States. However, to achieve near-term net zero energy performance that many stakeholders in the buildings industry desire, it is clear that energy codes will need to transition from prescriptive to performance-based approaches. However, that transition is not without potential pitfalls. Among the concerns expressed by stakeholders are added complexity and cost, lack of confidence in energy modeling results, gamesmanship on the part of applicants, lack or qualified reviewers, challenges in promoting de-carbonization, and the inequity of trading long lived envelope efficiency for short lived measures such as building controls. This paper will discuss multiple approaches being evaluated and implemented by Pacific Northwest National Laboratory to improve the usability of the performance-based approach for both code compliance and beyond code programs to meet aggressive energy savings targets. A 'system performance' approach provides a simpler approach compared to whole building performance, while keeping tradeoffs limited to specific building systems. A simplified whole-building performance-based approach for small commercial buildings can cost effectively achieve deeper savings for buildings that typically follow the prescriptive compliance approach. Improved reporting and verification processes applied to the traditional performance path can provide greater confidence in simulation results and facilitate adoption of performance-based approaches. Prescriptive packages provide prescriptive solutions while targeting specific performance thresholds. This paper discusses the progress being made with each of these approaches and provides examples of their implementation in energy codes and beyond code programs.

Performance Based Codes, Appendix G, PRM, TSPR, Sy↗
DOE OSTI2018

Analysis of radiant cooling system integrated with cooling tower for composite climatic conditions

Increased demand for cooling leads to consumption of a significant amount of energy by heating, ventilation, and air conditioning (HVAC) systems in buildings. Building envelope acts as a thermal barrier and plays a significant role in improving building energy efficiency. Radiant cooling systems often utilize building structure in the form of thermal storage and provide thermal comfort. The radiant cooling system has the potential of saving peak power in the buildings. In present study experimental and a simulation study is performed for chiller and cooling tower integrated chilled ceiling radiant cooling system for chilled water source and a parallel dedicated outdoor air system (DOAS) is used for providing latent load and fresh air requirements of the zone. Cooling tower based radiant cooling system is compared with a chiller-based radiant cooling system for achieving annual energy saving. Experiments are conducted for the chiller and cooling tower operated radiant cooling system. Based on experimental data, whole building simulation models of both cooling tower and chiller-based systems were calibrated. For both the simulation model of chiller and cooling tower operated radiant cooling system simulation were carried out for round the year. The annual simulation results show that the cooling tower operated radiant cooling system saves 14% energy as compared to the chilled water operated radiating cooling system.

Srivastava, Prateek↗
DOE OSTI2015

LESSONS FROM NUCLEAR ENERGY: BUILDING SNOW AND AVALANCHE SIMULATION TOOLS USING A COMMON OPEN-SOURCE FRAMEWORK

The Department of Energy (DOE) is currently investing millions of dollars annually into various modeling and simulation tools for all aspects of nuclear energy. An important part of this effort includes developing applications based on the open-source Multiphysics Object Oriented Simulation Environment (MOOSE; mooseframework.org) from Idaho National Laboratory (INL). Through the DOE and outside collaborators, MOOSE includes a large set of physics modules, including phase field, level set, heat conduction, tensor mechanics, Navier-Stokes, and porous media, among others. The phase-field module, in particular, is well-suited for micro-structure evolution simulations, including solidification, as shown in the figure. It was also used, in conjunction with the heat conduction module, to build a multiscale snow model (Pika) as presented at the 2014 International Snow Science Workshop (Slaughter et al., 2014). The snow science community should learn from the nuclear industry, and harness the enormous effort underway to build simulation tools that are open, modular, and share a common framework. In particular, MOOSE-based multi-physics solvers are inherently parallel, dimension agnostic, adaptive in time and space, fully-coupled, and capable of interacting with other applications. The snow science community must build on existing tools to enable collaboration between researchers and practitioners throughout the world, and advance the state-of-the-art in line with other scientific research efforts.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2024

Washington Housing Electrification Analysis [Slides]

This technical assistance is part of the Communities Local Energy Action Program (CLEAP) for the community of Beacon Hill, Seattle, WA. This analysis focuses on opportunities to reduce energy burden, energy consumption, and energy bills for both single family homes and large multifamily buildings. It uses state-level data from the ResStock modelling tool that was filtered to be relevant to Beacon Hill. Hence, this content includes single family detached homes and large multifamily buildings in the income group of 0-80% AMI, and climate zone 4c (mixed temperatures, relatively cooler summers) within Washington State.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2012

Wynkoop Building Performance Measurement: Water

This report is a summary of the water analysis performance for the Denver, Colorado Wynkoop Building. The Wynkoop Building (Figure 1) was built in 2006 as the Environmental Protection Agency (EPA) Region 8 Headquarters intended to house over 900 occupants in the 301,292 gross square feet (248,849 rentable square feet). The building was built on a brownfield in the Lower Downtown Historic District as part of an urban redevelopment effort. The building was designed and constructed through a public-private partnership with the sustainable design elements developed jointly by General Services Administration (GSA) and EPA. That partnership is still active with all parties still engaged to optimize building operations and use the building as a Learning Laboratory. The building design achieved U.S. Green Building Council Leadership in Energy and Environmental Design for New Construction (LEED-NC) Gold Certification in 2008 (Figure 2) and a 2008 EPA Energy Star Rating of 96 with design highlights that include: (1) Water use was designed to use 40% less than a typical design baseline. The design included low flow fixtures, waterless urinals and dual flush toilets; (2) Native and adaptive vegetation were selected to minimize the need for irrigation water for landscaping; and (3) Energy use intensity was modeled at 66.1 kBtus/gross square foot, which is 39% better than ASHRAE 90.1 1999. The Wynkoop Building water use (10 gallons/square foot) was measured at lower than industry average (15 gallons/square foot) and GSA goals (13 gallons/square foot), however, it was higher than building management expected it would be. The type of occupants and number of occupants can have a significant impact on fixture water use. The occupancy per floor varied significantly over the study time period, which added uncertainty to the data analysis. Investigation of the fixture use on the 2nd, 5th, and 7th floors identified potential for water use reduction if the flush direction of the dual-flush toilet handles was reversed. The building management retrofitted the building's toilets with handles that operated on reduced flush when pushed down (0.8 gallons) and full flush when pulled up (1.1 gallons). The water pressure on the 5th floor (< 30 psi) is less than half the pressure on the 7th floor (>80 psi). The measured water savings post-retrofit was lower on the 5th floor than the 7th floor. The differences in water pressure may have had an impact on the quantity of water used per floor. The second floor water use was examined prior to and following the toilet fixture retrofit. This floor is where conference rooms for non-building occupants are available for use, thus occupancy is highly variable. The 3-day average volume per flush event was higher post-retrofit (0.79 gallons per event), in contrast to pre-retrofit (0.57 gallons per event). There were 40% more flush events post retrofit, which impacted the findings. Water use in the third floor fitness center was also measured for a limited number of days. Because of water line accessibility, only water use on the men's side of the fitness center was measured and from that the total fitness center water use was estimated. Using the limited data collected, the fitness center shower water use is approximately 2% of the whole building water use. Overall water use in the Wynkoop Building is below the industry baseline and GSA expectations. The dual flush fixture replacement appears to have resulted in additional water savings that are expected to show a savings in the total annual water use.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2022

Designing for Zero Energy and Zero Carbon on a Multi-Building Scale Using URBANopt: Preprint

Groundbreaking efforts are necessary to mitigate contributors increasing impacts of climate change. In parallel to inventing pioneering clean energy technologies it is even more fundamental to rethink designing energy systems within a singular facility and collectively to function as a district. Facilities should not be continuously passive by just consuming; there is a need to shift to perform more dynamically. Designing for zero energy and zero carbon on a multi-building scale can uncover opportunities for building energy efficiency, decarbonization, demand flexibility, and resiliency that are not accessible at an individual building scale. This approach can be challenging without innovative tools to evaluate the multitude of possibilities. As an investigated result, we highlight the use of a campus-scale energy modeling platform - URBANopt™ - for the expansion of the National Renewable Energy Laboratory's (NREL's) South Table Mountain campus in Golden, Colorado. Programmatic growth included the design of three new all-electric, zero-energy, and zero-carbon, mixed used buildings (a combination of research laboratories and office space). This investigation is critical to NREL reaching net-zero emissions for its operational footprint, which will occur in phases over the next decade. Leveraging URBANopt's capabilities, we evaluate 1) high-performance building energy efficiency and decarbonization measures, 2) 4th generation district heating and cooling (4th GDHC) systems, 3) optimized onsite generation and energy storage assets that meet zero-energy and zero-carbon targets at minimum life-cycle costs, and 4) cost-optimal distributed energy technology mixes, dispatch strategies, and associated capacities that increase resiliency to grid outages. This work demonstrates the use and capabilities of URBANopt through a real-world case study on a multi-building scale.

community energy model↗