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At least 199 records · Page 11

All sources NASA NTRS DOE OSTI

DOE OSTI2015

A simplified model for estimating population-scale energy impacts of building envelope air-tightening and mechanical ventilation retrofits

Changing the air exchange rate of a home (the sum of the infiltration and mechanical ventilation airflow rates) affects the annual thermal conditioning energy. Large-scale changes to air exchange rates of the housing stock can significantly alter the residential sector's energy consumption. However, the complexity of existing residential energy models is a barrier to the accurate quantification of the impact of policy changes on a state or national level. The Incremental Ventilation Energy (IVE) model developed in this study combines the output of simple air exchange models with a limited set of housing characteristics to estimate the associated change in energy demand of homes. The IVE model was designed specifically to enable modellers to use existing databases of housing characteristics to determine the impact of ventilation policy change on a population scale. The IVE model estimates of energy change when applied to US homes with limited parameterisation are shown to be comparable to the estimates of a well-validated, complex residential energy model.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2013

Test Plan to Evaluate the Relationship Among IAQ, Comfort, Moisture, and Ventilation in Humid Climates

This experimental plan describes research being conducted by Pacific Northwest National Laboratory (PNNL), in coordinatation with Florida Solar Energy Center (FSEC), Florida HERO, and Lawrence Berkeley National Laboratory (LBNL) to evaluate the impact of ventilation rate on interior moisture levels, temperature distributions, and indoor air contaminant concentrations. Specifically, the research team will measure concentrations of indoor air contaminants, ventilation system flow rates, energy consumption, and temperature and relative humidity in ten homes in Gainesville, FL to characterize indoor pollutant levels and energy consumption associated with the observed ventilation rates. PNNL and FSEC have collaboratively prepared this experimental test plan, which describes background and context for the proposed study; the experimental design; specific monitoring points, including monitoring equipment, and sampling frequency; key research questions and the associated data analysis approach; experimental logistics, including schedule, milestones, and team member contact information; and clearly identifies the roles and responsibilities of each team in support of project objectives.

High Performance Homes↗

DOE OSTI2016

Measured performance of filtration and ventilation systems for fine and ultrafine particles and ozone in an unoccupied modern California house

This study evaluated nine ventilation and filtration systems in an unoccupied 2006 house located 250m downwind of the I-80 freeway in Sacramento, California. Systems were evaluated for reducing indoor concentrations of outdoor particles in summer and fall/winter, ozone in summer, and particles from stir-fry cooking. Air exchange rate was measured continuously. Energy use was estimated for year-round operation in California. Exhaust ventilation without enhanced filtration produced indoor PM 2.5 that was 70% lower than outdoors. Supply ventilation with MERV13 filtration provided slightly less protection whereas supply MERV16 filtration reduced PM 2.5 5 by 97-98% relative to outdoors. Supply filtration systems used little energy but provided no benefits for indoor-generated particles. Systems with MERV13-16 filters in the recirculating heating and cooling unit (FAU) operating continuously or 20 min/h reduced PM 2.5 by 93-98%. Across all systems, removal percentages were higher for ultrafine particles and lower for black carbon, relative to PM 2.5 . Indoor ozone was 3-4% of outdoors for all systems except an electronic air cleaner that produced ozone. Filtration via the FAU or portable filtration units lowered PM 2.5 by 25-75% when operated over the hour following cooking. The energy for year-round operation of FAU filtration with an efficient blower motor was estimated at 600 kWh/year.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2018

Field and Laboratory Testing of Approaches to Smart Whole-House Mechanical Ventilation Control

Whole-house mechanical ventilation is a critical component to a comprehensive strategy for good indoor air quality (IAQ). However, due to lack of integration with standard heating and cooling systems, and perceptions from a portion of the homebuilding industry about risks related to increased energy use, increased cost, and decreased comfort, voluntary and code-required adoption varies amongst regions. Smart ventilation controls (SVC) balance energy consumption, comfort, and IAQ by optimizing mechanical ventilation operation to reduce the heating and/or cooling loads, improve management of indoor moisture, and maintain IAQ equivalence according to ASHRAE 62.2.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2018

Field and Laboratory Testing of Approaches to Smart Whole-House Mechanical Ventilation Control

Whole-house mechanical ventilation is a critical component to a comprehensive strategy for good indoor air quality (IAQ). However, due to lack of integration with standard heating and cooling systems, and perceptions from a portion of the homebuilding industry about risks related to increased energy use, increased cost, and decreased comfort, voluntary and code-required adoption varies among regions. Smart ventilation controls (SVC) balance energy consumption, comfort, and IAQ by optimizing mechanical ventilation operation to reduce the heating and/or cooling loads, improve management of indoor moisture, and maintain IAQ equivalence according to ASHRAE 62.2.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2021

Research and Development of a Ventilation-Integrated Comfort System

From an indoor air quality perspective, the best residential ventilation strategies include filtering outdoor air and distributing that air to all occupied parts of a home. From an energy standpoint, it's desirable that energy be transferred from the exhaust air to the incoming outdoor air to limit heating and cooling impacts. Heat or energy recovery ventilation systems (HRVs or ERVs) can provide these functions, but researchers have seen many poor installations related to design, installation, and operation and maintenance. More robust ventilation systems may involve an ERV with a dedicated duct distribution system and controls. Such a duct system can be costly to install, and many builders reduce these costs by connecting an ERV to a central heating and cooling duct system. While this can sometimes be done effectively, researchers have seen consistent challenges with low, inconsistent, or imbalanced flow rates; high electricity consumption; and - of greatest concern - outdoor air short-circuiting or not being delivered to occupied spaces at all. Most ERVs are designed to operate with their own duct system; they are not designed as an add-on to much larger HVAC systems. With support from the US DOE Building Technologies Office, Steven Winter Associates, Inc. (SWA) partnered with Mitsubishi Electric Trane US, CORE Energy Recovery Solutions, and Therma-Stor LLC to design and test VICS prototypes. A conceptual diagram is shown in Figure 1, and the latest prototype (shown in Figure 2) was manufactured by Therma-Stor and tested in SWA's facility in Norwalk, CT. The ERV heat exchanger was provided by CORE, and the VICS was installed in conjunction with a 1-ton, inverter heat pump provided by Mitsubishi.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

DOE OSTI2024

Ventilation and Indoor Air Quality in Recently Constructed U.S. Homes: Measured Data From Select Southeastern States

Little data is available that quantifies IAQ or associates contaminant levels with air exchange in U.S. homes. To address this gap, the U.S. Department of Energy (DOE) Building America Program conducted a study to characterize IAQ in U.S. homes constructed since 2013, along with presence, functionality, and occupant use of control measures. Specific objectives of this study effort included: Measuring time-integrated concentrations and temporal profiles of established contaminants of concern; monitoring the use of ventilation equipment; and tracking activities that impact air pollutant emissions and removal processes in typical homes in various climate zones; Characterizing the prevalence, type, and installed performance of mechanical ventilation equipment in new homes; exploring regional variations in system designs and performance; Investigating associations between contaminant levels and the presence of control measures including whole-house mechanical ventilation (WHMV). The study engaged research teams to collect data at a regional level. This report introduces the study protocol and presents and discusses high-level results obtained from Florida Solar Energy Center (FSEC) data collection efforts in the southeastern U.S. states of Florida, Georgia, and South Carolina.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2021

Impact of Intake and Exhaust Ducts on the Recovery Efficiency of Heat Recovery Ventilation Systems

The heat recovery efficiency of ventilation systems utilizing heat recovery ventilators (HRVs) depends not only on the heat recovery efficiency of the HRV units themselves but also on the intake and exhaust ducts that connect the HRV units to the outside environment. However, these ducts are often neglected in heat loss calculations, as their impact on the overall heat recovery efficiency of HRV systems is often not understood and, to the knowledge of the authors, a mathematical model for the overall heat recovery efficiency of HRV systems that accounts for these ducts has not been published. In this research, a mathematical model for the overall heat recovery efficiency of HRV systems that accounts for the intake and exhaust ducts was derived and validated using real-life data. The model-predicted decrease in heat recovery efficiency due to the ducts was in reasonable agreement (relative error within 20%) with the real-life measurements. The results suggest that utilizing this model allows for more correct ventilation heat loss calculations compared to using the heat recovery efficiency of the HRV unit alone, but more field studies are needed to verify the accuracy of this model in a wide range of applications.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

NASA NTRS2000

Ventilation-perfusion matching in long-term microgravity

We studied the ventilation-perfusion matching pattern in normal gravity (1 G) and short- and long-duration microgravity (microG) using the cardiogenic oscillations in the sulfur hexaflouride (SF(6)) and CO(2) concentration signals during the phase III portion of vital capacity single-breath washout experiments. The signal power of the cardiogenic concentration variations was assessed by spectral analysis, and the phase angle between the oscillations of the two simultaneously expired gases was obtained through cross-correlation. For CO(2), a significant reduction of cardiogenic power was observed in microG, with respect to 1 G, but the reduction was smaller and more variable in the case of SF(6). A shift from an in-phase condition in 1 G to an out-of-phase condition was found for both short- and long-duration microG. We conclude that, although the distribution of ventilation and perfusion becomes more homogeneous in microG, significant inhomogeneities persist and that areas of high perfusion become associated with areas of relatively lower ventilation. In addition, these modifications seem to remain constant during long-term exposure to microG.

Mir Project↗

NASA NTRS2000

Regional ventilation-perfusion distribution is more uniform in the prone position

The arterial blood PO(2) is increased in the prone position in animals and humans because of an improvement in ventilation (VA) and perfusion (Q) matching. However, the mechanism of improved VA/Q is unknown. This experiment measured regional VA/Q heterogeneity and the correlation between VA and Q in supine and prone positions in pigs. Eight ketamine-diazepam-anesthetized, mechanically ventilated pigs were studied in supine and prone positions in random order. Regional VA and Q were measured using fluorescent-labeled aerosols and radioactive-labeled microspheres, respectively. The lungs were dried at total lung capacity and cubed into 603-967 small ( approximately 1.7-cm(3)) pieces. In the prone position the homogeneity of the ventilation distribution increased (P = 0.030) and the correlation between VA and Q increased (correlation coefficient = 0.72 +/- 0.08 and 0.82 +/- 0.06 in supine and prone positions, respectively, P = 0.03). The homogeneity of the VA/Q distribution increased in the prone position (P = 0.028). We conclude that the improvement in VA/Q matching in the prone position is secondary to increased homogeneity of the VA distribution and increased correlation of regional VA and Q.

NASA Program Biomedical Research and Countermeasur↗

NASA NTRS1992

Ventilation-perfusion matching during exercise

In normal subjects, exercise widens the alveolar-arterial PO2 difference (P[A-a]O2) despite a more uniform topographic distribution of ventilation-perfusion (VA/Q) ratios. While part of the increase in P(A-a)O2 (especially during heavy exercise) is due to diffusion limitation, a considerable amount is caused by an increase in VA/Q mismatch as detected by the multiple inert gas elimination technique. Why this occurs is unknown, but circumstantial evidence suggests it may be related to interstitial pulmonary edema rather than to factors dependent on ventilation, airway gas mixing, airway muscle tone, or pulmonary vascular tone. In patients with lung disease, the gas exchange consequences of exercise are variable. Thus, arterial PO2 may increase, remain the same, or fall. In general, patients with advanced chronic obstructive pulmonary disease (COPD) or interstitial fibrosis who exercise show a fall in PO2. This is usually not due to worsening VA/Q relationships but mostly to the well-known fall in mixed venous PO2, which itself results from a relatively smaller increase in cardiac output than VO2. However, in interstitial fibrosis (but not COPD), there is good evidence that a part of the fall in PO2 on exercise is caused by alveolar-capillary diffusion limitation of O2 transport; in COPD (but not interstitial fibrosis), a frequent additional contributing factor to the hypoxemia of exercise is an inadequate ventilatory response, such that minute ventilation does not rise as much as does CO2 production or O2 uptake, causing arterial PCO2 to increase and PO2 to fall.

Non-NASA Center↗

DOE OSTI2014

A Prospective Study of Ventilation Rates and Illness Absence in California Office Buildings

Background – This study investigated the associations of ventilation rates (VRs), estimated from indoor CO2 concentrations, in offices with the amount of respiratory infections, illness absences, and building-related health symptoms in occupants. Methods – Office buildings were recruited from three California climate zones. In one or more study spaces within each building, real-time logging sensors measured carbon dioxide, temperature, and relative humidity for one year. Ventilation rates were estimated using daily peak CO2 levels, and also using an alternative metric. Data on occupants and health outcomes were collected through web-based surveys every three months. Multivariate models were used to assess relationships between metrics of ventilation rate or CO2 and occupant outcomes. For all outcomes, negative associations were hypothesized with VR metrics, and positive associations with CO2 metrics. Results – Difficulty recruiting buildings and low survey response limited sample size and study power. In 16 studied spaces within 9 office buildings, VRs were uniformly high over the year, from twice to over nine times the California office VR standard (7 L/s or 15 cfm per person). VR and CO2 metrics had no statistically significant relationships with occupant outcomes, except for a small significantly positive association of the alternative VR metric with respiratory illness-related absence, contrary to hypotheses. Conclusions– The very high time-averaged VRs in the California office buildings studied presumably resulted from “economizer cycles” bringing in large volumes of outdoor air; however, in almost all buildings even the estimated minimum VRs supplied (without the economizer) substantially exceeded the minimum required VR. These high VRs may explain the absence of hypothesized relationships with occupant outcomes. Among uniformly high VRs, little variation in contaminant concentration and occupant effects would be expected. These findings may provide initial evidence for an upper bound of the range of VRs within which increased VRs provide benefits in reducing illness absence.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2020

Smart Ventilation Controls Boost Energy Efficiency and Indoor Air Quality

The average American household spends more than $2,200 a year on energy, and heating, ventilating, and air conditioning (HVAC) costs comprise nearly half of the bill. This is one reason why home builders focus on tightening building envelopes to save energy. Yet, limiting the potential for air exchange can negatively impact indoor air quality (IAQ). When outdoor conditions are most extreme during occupied periods, there may be comfort implications from continuing high levels of ventilation during associated weather events. This is true even with heat recovery. To mitigate risks, the Florida Solar Energy Center developed and tested approaches for “smart” ventilation system controls that enable more reliable design, installation, and operation to achieve desired IAQ while also minimizing energy and comfort impacts.

Building America↗

DOE OSTI2020

Smart Ventilation Controls Boost Energy Efficiency and Indoor Air Quality

30 DIRECT ENERGY CONVERSION↗

DOE OSTI2015

Feasibility studies for the design of disposal vaults for multi-purpose containers (MPCs): construction, operation, ventilation and management of heat - 15175

The Nuclear Decommissioning Authority (NDA) subsidiary, Radioactive Waste Management Ltd (RWM) is responsible for the safe implementation of a Geological Disposal Facility (GDF) for radioactive waste in the UK. As part of their generic programme to underpin the planned designs for a GDF, work is ongoing to explore a range of possible geological disposal concepts. This work developed GDF concept designs for Multi-Purpose Containers (MPC) disposal in the generic host rock types considered: higher strength (crystalline), lower strength sedimentary (sedimentary / clay formations) and evaporite rocks. This paper is specific to concepts for the disposal of MPC for Pressurised Water Reactor (PWR) spent nuclear fuel (SF). The key outcomes of the feasibility studies to improve the understanding of the MPC disposal concept and the specific challenges to construct, operate, ventilate, manage heat and backfill associated with this concept are summarised in this paper. The management of the high loading of radiogenic heat (from 12 PWR SF assemblies in MPCs compared to 4 in 'standard' disposal containers) during an extended open phase (delayed backfilling of the disposal area) of up to 300 years was investigated. The concept designs developed demonstrate it is feasible to construct, operate and ventilate disposal vaults to accommodate open 'storage' periods required for transitional thermal decay of high heat generating waste in higher strength and lower strength sedimentary host rock types considered by RWM. This work focused on developing two contrasting disposal concepts which are applicable to both higher strength and lower strength rock environments; both of which illustrate how vault temperature, stability and groundwater inflows can be controlled to delay backfilling and allow MPC package thermal output to decrease. MPC disposal in evaporite rock does not require a cooling period due to its high thermal conductivity and favourable performance at higher temperatures; therefore the concept developed for this rock includes immediate backfilling of disposal tunnels. A clear understanding of the interactions and limitations associated with heat management during the open period was developed by investigation of a 'Heating Ventilation and Air-Conditioning System' (HVAC). It was concluded that removal of heat from the disposal tunnels / vaults is feasible, but introduces significant operational complexity. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2015

Sealed Crawl Spaces with Integrated Whole-House Ventilation in a Cold Climate

One method of code-compliance for crawlspaces is to seal and insulate the crawlspace, rather than venting to the outdoors. However, codes require mechanical ventilation; either via conditioned supply air from the HVAC system, or a continuous exhaust ventilation strategy. As the CARB's building partner, Ithaca Neighborhood Housing Services, intended to use the unvented crawlspace in a recent

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2025

Operator learning for energy-efficient building ventilation control with computational fluid dynamics simulation of a real-world classroom

Energy-efficient ventilation control plays an important role in reducing building energy consumption while ensuring occupant health and comfort. While Computational Fluid Dynamics (CFD) simulations provide detailed and physically accurate representations of indoor airflow, their high computational cost limits their use in real-time building control. In this work, we present a neural operator learning framework that combines the physical accuracy of CFD with the computational efficiency of machine learning to enable building ventilation control with the high-fidelity fluid dynamics models. Our method jointly optimizes the airflow supply rates and vent angles to reduce energy use and adhere to air quality constraints. We train an ensemble of neural operator transformer models to learn the mapping from building control actions to airflow fields using high-resolution CFD data. This learned neural operator is then embedded in an optimization-based control framework for building ventilation control. Experimental results show that our approach achieves significant energy savings compared to maximum airflow rate control, rule-based control, as well as data-driven control methods using spatially averaged CO 2 prediction and deep learning–based reduced-order models, while consistently maintaining safe indoor air quality. These results highlight the practicality and scalability of our method in maintaining energy efficiency and indoor air quality in real-world buildings.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2020

Risk assessment and ventilation modeling for hydrogen releases in vehicle repair garages

The availability of repair garage infrastructure for hydrogen fuel cell vehicles is becoming increasingly important for future industry growth. Ventilation requirements for hydrogen fuel cell vehicles can affect both retrofitted and purpose-built repair garages and the costs associated with these requirements can be significant. A hazard and operability (HAZOP) study was performed to identify risk-significant scenarios related to light-duty hydrogen vehicles in a repair garage. Detailed simulations and modeling were performed using appropriate computational tools to estimate the location, behavior, and severity of hydrogen release based on key HAZOP scenarios. Here, this work compares current fire code requirements to an alternate ventilation strategy to further reduce potential hazardous conditions. Modeling shows that position, direction, and velocity of ventilation have a significant impact on the amount of instantaneous flammable mass in the domain.

08 HYDROGEN↗