Matching Items (25)

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Investigation of CO2 tracer gas-based calibration of multi-zone airflow models

Description

The modeling and simulation of airflow dynamics in buildings has many applications including indoor air quality and ventilation analysis, contaminant dispersion prediction, and the calculation of personal occupant exposure. Multi-zone airflow model software programs provide such capabilities in a manner

The modeling and simulation of airflow dynamics in buildings has many applications including indoor air quality and ventilation analysis, contaminant dispersion prediction, and the calculation of personal occupant exposure. Multi-zone airflow model software programs provide such capabilities in a manner that is practical for whole building analysis. This research addresses the need for calibration methodologies to improve the prediction accuracy of multi-zone software programs. Of particular interest is accurate modeling of airflow dynamics in response to extraordinary events, i.e. chemical and biological attacks. This research developed and explored a candidate calibration methodology which utilizes tracer gas (e.g., CO2) data. A key concept behind this research was that calibration of airflow models is a highly over-parameterized problem and that some form of model reduction is imperative. Model reduction was achieved by proposing the concept of macro-zones, i.e. groups of rooms that can be combined into one zone for the purposes of predicting or studying dynamic airflow behavior under different types of stimuli. The proposed calibration methodology consists of five steps: (i) develop a "somewhat" realistic or partially calibrated multi-zone model of a building so that the subsequent steps yield meaningful results, (ii) perform an airflow-based sensitivity analysis to determine influential system drivers, (iii) perform a tracer gas-based sensitivity analysis to identify macro-zones for model reduction, (iv) release CO2 in the building and measure tracer gas concentrations in at least one room within each macro-zone (some replication in other rooms is highly desirable) and use these measurements to further calibrate aggregate flow parameters of macro-zone flow elements so as to improve the model fit, and (v) evaluate model adequacy of the updated model based on some metric. The proposed methodology was first evaluated with a synthetic building and subsequently refined using actual measured airflows and CO2 concentrations for a real building. The airflow dynamics of the buildings analyzed were found to be dominated by the HVAC system. In such buildings, rectifying differences between measured and predicted tracer gas behavior should focus on factors impacting room air change rates first and flow parameter assumptions between zones second.

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2011

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Coupling of thermal mass with night ventilation in buildings

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Passive cooling designs & technologies offer great promise to lower energy use in buildings. Though the working principles of these designs and technologies are well understood, simplified tools to quantitatively evaluate their performance are lacking. Cooling by night ventilation, which

Passive cooling designs & technologies offer great promise to lower energy use in buildings. Though the working principles of these designs and technologies are well understood, simplified tools to quantitatively evaluate their performance are lacking. Cooling by night ventilation, which is the topic of this research, is one of the well known passive cooling technologies. The building's thermal mass can be cooled at night by ventilating the inside of the space with the relatively lower outdoor air temperatures, thereby maintaining lower indoor temperatures during the warmer daytime period. Numerous studies, both experimental and theoretical, have been performed and have shown the effectiveness of the method to significantly reduce air conditioning loads or improve comfort levels in those climates where the night time ambient air temperature drops below that of the indoor air. The impact of widespread adoption of night ventilation cooling can be substantial, given the large fraction of energy consumed by air conditioning of buildings (about 12-13% of the total electricity use in U.S. buildings). Night ventilation is relatively easy to implement with minimal design changes to existing buildings. Contemporary mathematical models to evaluate the performance of night ventilation are embedded in detailed whole building simulation tools which require a certain amount of expertise and is a time consuming approach. This research proposes a methodology incorporating two models, Heat Transfer model and Thermal Network model, to evaluate the effectiveness of night ventilation. This methodology is easier to use and the run time to evaluate the results is faster. Both these models are approximations of thermal coupling between thermal mass and night ventilation in buildings. These models are modifications of existing approaches meant to model dynamic thermal response in buildings subject to natural ventilation. Effectiveness of night ventilation was quantified by a parameter called the Discomfort Reduction Factor (DRF) which is the index of reduction of occupant discomfort levels during the day time from night ventilation. Daily and Monthly DRFs are calculated for two climate zones and three building heat capacities. It is verified that night ventilation is effective in seasons and regions when day temperatures are between 30 oC and 36 oC and night temperatures are below 20 oC. The accuracy of these models may be lower than using a detailed simulation program but the loss in accuracy in using these tools more than compensates for the insights provided and better transparency in the analysis approach and results obtained.

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2011

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Implementation of building information modeling for wafer fab construction

Description

Semiconductor manufacturing facilities are very complex and capital intensive in nature. During the lifecycle of these facilities various disciplines come together, generate and use a tremendous amount of building and process information to support various decisions that enable them to

Semiconductor manufacturing facilities are very complex and capital intensive in nature. During the lifecycle of these facilities various disciplines come together, generate and use a tremendous amount of building and process information to support various decisions that enable them to successfully design, build and sustain these advanced facilities. However, a majority of the information generated and processes taking place are neither integrated nor interoperable and result in a high degree of redundancy. The objective of this thesis is to build an interoperable Building Information Model (BIM) for the Base-Build and Tool Installation in a semiconductor manufacturing facility. It examines existing processes and data exchange standards available to facilitate the implementation of BIM and provides a framework for the development of processes and standards that can help in building an intelligent information model for a semiconductor manufacturing facility. To understand the nature of the flow of information between the various stakeholders the flow of information between the facility designer, process tool manufacturer and tool layout designer is examined. An information model for the base build and process tool is built and the industry standards SEMI E6 and SEMI E51 are used as a basis to model the information. It is found that applications used to create information models support interoperable industry standard formats such as the Industry Foundation Classes (IFC) and ISO 15926 in a limited manner. A gap analysis has revealed that interoperability standards applicable to the semiconductor manufacturing industry such as the IFC and ISO15926 need to be expanded to support information transfers unique to the industry. Information modeling for a semiconductor manufacturing facility is unique in that it is a process model (Process Tool Information Model) within a building model (Building Information Model), each of them supported more robustly by different interoperability standards. Applications support interoperability data standards specific to the domain or industry they serve but information transfers need to occur between the various domains. To facilitate flow of information between the different domains it is recommended that a mapping of the industry standards be undertaken and translators between them be developed for business use.

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2011

The net zero-energy home: precedent and catalyst for local performance-based architecture

Description

The building sector is responsible for consuming the largest proportional share of global material and energy resources. Some observers assert that buildings are the problem and the solution to climate change. It appears that in the United States a coherent

The building sector is responsible for consuming the largest proportional share of global material and energy resources. Some observers assert that buildings are the problem and the solution to climate change. It appears that in the United States a coherent national energy policy to encourage rapid building performance improvements is not imminent. In this environment, where many climate and ecological scientists believe we are running out of time to reverse the effects of anthropogenic climate change, a local grass-roots effort to create demonstration net zero-energy buildings (ZEB) appears necessary. This paper documents the process of designing a ZEB in a community with no existing documented ZEB precedent. The project will establish a framework for collecting design, performance, and financial data for use by architects, building scientists, and the community at large. This type of information may prove critical in order to foster a near-term local demand for net zero-energy buildings.

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2014

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Enhancing the cooling capacity of roof ponds using polyethylene band filter

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With the desire of high standards of comfort, huge amount of energy is being consumed to maintain the indoor environment. In US building consumes 40% of the total primary energy while residential buildings consume about 21%. A large proportion of

With the desire of high standards of comfort, huge amount of energy is being consumed to maintain the indoor environment. In US building consumes 40% of the total primary energy while residential buildings consume about 21%. A large proportion of this consumption is due to cooling of buildings. Deteriorating environmental conditions due to excessive energy use suggest that we should look at passive designs and renewable energy opportunities to supply the required comfort. Phoenix gets about 300 days of clear sky every year. It also witnesses large temperature variations from night and day. The humidity ratio almost always stays below the 50% mark. With more than six months having outside temperatures more than 75 oF, night sky radiative cooling promise to be an attractive means to cool the buildings during summer. This technique can be useful for small commercial facilities or residential buildings. The roof ponds can be made more effective by covering them with Band Filters. These band filters block the solar heat gain and allow the water to cool down to lower temperatures. It also reduces the convection heat gain. This helps rood ponds maintain lower temperatures and provide more cooling then an exposed pond. 50 μm Polyethylene band filter is used in this study. Using this band filter, roof ponds can be made up to 10% more effective. About 45% of the energy required to cool a typical residential building in summer can be saved.

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2013

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Investigation of heat dissipation enhancement due to backfill modification in ground coupled heat pump systems

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Due to the lack of understanding of soil thermal behavior, rules-of-thumb and generalized procedures are typically used to guide building professionals in the design of ground coupled heat pump systems. This is especially true when sizing the ground heat exchanger

Due to the lack of understanding of soil thermal behavior, rules-of-thumb and generalized procedures are typically used to guide building professionals in the design of ground coupled heat pump systems. This is especially true when sizing the ground heat exchanger (GHE) loop. Unfortunately, these generalized procedures often encourage building engineers to adopt a conservative design approach resulting in the gross over-sizing of the GHE, thus drastically increasing their installation cost. This conservative design approach is particularly prevalent for buildings located in hot and arid climates, where the soils are often granular and where the water table tends to exist deep below the soil surface. These adverse soil conditions reduce the heat dissipation efficiency of the GHE and have hindered the adoption of ground coupled heat pump systems in such climates. During cooling mode operation, heat is extracted from the building and rejected into the ground via the GHE. Prolonged heat dissipation into the ground can result in a coupled flow of both heat and moisture, causing the moisture to migrate away from the GHE piping. This coupled flow phenomenon causes the soil near the GHE to dry out and results in the degradation of the GHE heat dissipation capacity. Although relatively simple techniques of backfilling the GHE have been used in practice to mitigate such coupled effects, methods of improving the thermal behavior of the backfill region around the GHE, especially in horizontal systems, have not been extensively studied. This thesis presents an experimental study of heat dissipation from a horizontal GHE, buried in two backfill materials: (1) dry sand, and (2) wax-sand composite mixture. The HYDRUS software was then used to numerically model the temperature profiles associated with the aforementioned backfill conditions, and the influence of the contact resistance at the GHE-backfill interface was studied. The modeling strategy developed in HYDRUS was proven to be adequate in predicting the thermal performance of GHE buried in dry sand. However, when predicting the GHE heat dissipation in the wax-sand backfill, significant discrepancies between model prediction and experimental results still exist even after calibrating the model by including a term for the contact resistance. Overall, the thermal properties of the backfill were determined to be a key determinant of the GHE heat dissipation capacity. In particular, the wax-sand backfill was estimated to dissipate 50-60% more heat than dry sand backfill.

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2012

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The effect of high SRI roofing finishes across climate zones in the U.S

Description

The intent of this research is to determine if cool roofs lead to increased energy use in the U.S. and if so, in what climates. Directed by the LEED environmental building rating system, cool roofs are increasingly specified in an

The intent of this research is to determine if cool roofs lead to increased energy use in the U.S. and if so, in what climates. Directed by the LEED environmental building rating system, cool roofs are increasingly specified in an attempt to mitigate urban heat island effect. A typical single story retail building was simulated using eQUEST energy software across seven different climatic zones in the U.S.. Two roof types are varied, one with a low solar reflectance index of 30 (typical bituminous roof), and a roof with SRI of 90 (high performing membrane roof). The model also varied the perimeter / core fraction, internal loads, and schedule of operations. The data suggests a certain point at which a high SRI roofing finish results in energy penalties over the course of the year in climate zones which are heating driven. Climate zones 5 and above appear to be the flipping point, beyond which the application of a high SRI roof creates sufficient heating penalties to outweigh the cooling energy benefits.

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2011

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Analysis methods for post occupancy evaluation of energy-use in high performance buildings using short-term monitoring

Description

The green building movement has been an effective catalyst in reducing energy demands of buildings and a large number of `green' certified buildings have been in operation for several years. Whether these buildings are actually performing as intended, and if

The green building movement has been an effective catalyst in reducing energy demands of buildings and a large number of `green' certified buildings have been in operation for several years. Whether these buildings are actually performing as intended, and if not, identifying specific causes for this discrepancy falls into the general realm of post-occupancy evaluation (POE). POE involves evaluating building performance in terms of energy-use, indoor environmental quality, acoustics and water-use; the first aspect i.e. energy-use is addressed in this thesis. Normally, a full year or more of energy-use and weather data is required to determine the actual post-occupancy energy-use of buildings. In many cases, either measured building performance data is not available or the time and cost implications may not make it feasible to invest in monitoring the building for a whole year. Knowledge about the minimum amount of measured data needed to accurately capture the behavior of the building over the entire year can be immensely beneficial. This research identifies simple modeling techniques to determine best time of the year to begin in-situ monitoring of building energy-use, and the least amount of data required for generating acceptable long-term predictions. Four analysis procedures are studied. The short-term monitoring for long-term prediction (SMLP) approach and dry-bulb temperature analysis (DBTA) approach allow determining the best time and duration of the year for in-situ monitoring to be performed based only on the ambient temperature data of the location. Multivariate change-point (MCP) modeling uses simulated/monitored data to determine best monitoring period of the year. This is also used to validate the SMLP and DBTA approaches. The hybrid inverse modeling method-1 predicts energy-use by combining a short dataset of monitored internal loads with a year of utility-bills, and hybrid inverse method-2 predicts long term building performance using utility-bills only. The results obtained show that often less than three to four months of monitored data is adequate for estimating the annual building energy use, provided that the monitoring is initiated at the right time, and the seasonal as well as daily variations are adequately captured by the short dataset. The predictive accuracy of the short data-sets is found to be strongly influenced by the closeness of the dataset's mean temperature to the annual average temperature. The analysis methods studied would be very useful for energy professionals involved in POE.

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2011

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Analysis of the impact of urban heat island on energy consumption of buildings in Phoenix

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The Urban Heat Island (UHI) has been known to have been around from as long as people have been urbanizing. The growth and conglomeration of cities in the past century has caused an increase in the intensity and impact of

The Urban Heat Island (UHI) has been known to have been around from as long as people have been urbanizing. The growth and conglomeration of cities in the past century has caused an increase in the intensity and impact of Urban Heat Island, causing significant changes to the micro-climate and causing imbalances in the temperature patterns of cities. The urban heat island (UHI) is a well established phenomenon and it has been attributed to the reduced heating loads and increased cooling loads, impacting the total energy consumption of affected buildings in all climatic regions. This thesis endeavors to understand the impact of the urban heat island on the typical buildings in the Phoenix Metropolitan region through an annual energy simulation process spanning through the years 1950 to 2005. Phoenix, as a representative city for the hot-arid cooling-dominated region, would be an interesting example to see how the reduction in heating energy consumption offsets the increased demand for cooling energy in the building. The commercial reference building models from the Department of Energy have been used to simulate commercial building stock, while for the residential stock a representative residential model prescribing to IECC 2006 standards will be used. The multiyear simulation process will bring forth the energy consumptions of various building typologies, thus highlighting differing impacts on the various building typologies. A vigorous analysis is performed to see the impact on the cooling loads annually, specifically during summer and summer nights, when the impact of the 'atmospheric canopy layer' - urban heat island (UHI) causes an increase in the summer night time minimum and night time average temperatures. This study also shows the disparity in results of annual simulations run utilizing a typical meteorological year (TMY) weather file, to that of the current recorded weather data. The under prediction due to the use of TMY would translate to higher or lower predicted energy savings in the future years, for changes made to the efficiencies of the cooling or heating systems and thermal performance of the built-forms. The change in energy usage patterns caused by higher cooling energy and lesser heating energy consumptions could influence future policies and energy conservation standards. This study could also be utilized to understand the impacts of the equipment sizing protocols currently adopted, equipment use and longevity and fuel swapping as heating cooling ratios change.

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2011

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Comparative analysis of benchmarking and audit tools

Description

Among the various end-use sectors, the commercial sector is expected to have the second-largest increase in total primary energy consump¬tion from 2009 to 2035 (5.8 quadrillion Btu) with a growth rate of 1.1% per year, it is the fastest growing

Among the various end-use sectors, the commercial sector is expected to have the second-largest increase in total primary energy consump¬tion from 2009 to 2035 (5.8 quadrillion Btu) with a growth rate of 1.1% per year, it is the fastest growing end-use sectors. In order to make major gains in reducing U.S. building energy use commercial sector buildings must be improved. Energy benchmarking of buildings gives the facility manager or the building owner a quick evaluation of energy use and the potential for energy savings. It is the process of comparing the energy performance of a building to standards and codes, to a set target performance or to a range of energy performance values of similar buildings in order to help assess opportunities for improvement. Commissioning of buildings is the process of ensuring that systems are designed, installed, functionally tested and capable of being operated and maintained according to the owner's operational needs. It is the first stage in the building upgrade process after it has been assessed using benchmarking tools. The staged approach accounts for the interactions among all the energy flows in a building and produces a systematic method for planning upgrades that increase energy savings. This research compares and analyzes selected benchmarking and retrocommissioning tools to validate their accuracy such that they could be used in the initial audit process of a building. The benchmarking study analyzes the Energy Use Intensities (EUIs) and Ratings assigned by Portfolio Manager and Oak Ridge National Laboratory (ORNL) Spreadsheets. The 90.1 Prototype models and Commercial Reference Building model for Large Office building type were used for this comparative analysis. A case-study building from the DOE - funded Energize Phoenix program was also benchmarked for its EUI and rating. The retrocommissioning study was conducted by modeling these prototype models and the case-study building in the Facility Energy Decision System (FEDS) tool to simulate their energy consumption and analyze the retrofits suggested by the tool. The results of the benchmarking study proved that a benchmarking tool could be used as a first step in the audit process, encouraging the building owner to conduct an energy audit and realize the energy savings potential. The retrocommissioning study established the validity of FEDS as an accurate tool to simulate a building for its energy performance using basic inputs and to accurately predict the energy savings achieved by the retrofits recommended on the basis of maximum LCC savings.

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2011