Browsing by Subject "HVAC"
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Item Demand side load control in residential buildings with HVAC controller for demand response(2015-05) Yoon, Ji Hoon; Baldick, Ross; Novoselac, Atila; Arapostathis, Aristotle; Liedl, Petra G; Kwasinski, AlexisDemand Response (DR) is a key factor to increase the efficiency of the power grid and has the potential to facilitate supply-demand balance. Demand side load control can contribute to reduce electricity consumption through DR programs. Especially, Heating, Ventilating and Air Conditioning (HVAC) load is one of the major contributors to peak loads. In the United States, HVAC systems are the largest consumers of electrical energy and a major contributor to peak demand. In this research, the Dynamic Demand Response Controller (DDRC) is proposed to reduce peak load as well as saves electricity cost while maintaining reasonable thermal comfort by controlling HVAC system. To reduce both peak load and energy cost, DDRC controls the set-point temperature in a thermostat depending on real-time price of electricity. Residential buildings are modeled with various internal loads using building energy modeling tools. The weather data in different climate zones are used to demonstrate that DDRC decreases peak loads and brings economic benefit in various locations. In addition, two different types of electricity wholesale markets are used to generate DR signals. To assess the performance of DDRC, the control algorithms are improved to consider the characteristics of building envelopes and HVAC equipment. Also, DDRC is designed to be deployed in various areas with different electricity wholesale markets. The indoor thermal comfort on temperature and humidity are considered based on ASHRAE standard 55. Finally, DDRC is developed to a hardware using embedded system. The hardware of DDRC is based on Advanced RISC Microcontroller (ARM) processor and senses both indoor and outdoor environment with Internet connection capability for DR. In addition, user friendly Graphic User Interface (GUI) is generated to control DDRC.Item Evaluating an energy efficiency project for an existing commercial building(2011-12) Krasner, William Paul; Nichols, Steven Parks, 1950-; Duvic, Robert Conrad, 1947-In this thesis I provide general guidelines for a commercial building owner’s decision making process for heating, ventilation, and air-conditioning (HVAC) system energy efficiency projects, discuss an example HVAC project at an existing building, and recommend the most energy-efficient, cost-effective project option. First, a building’s HVAC system’s inefficiencies are identified. The systems and the components can be investigated to understand the nature of the operations. In the building owner’s interests, possible alternatives can be developed to address the systems with improvements. Consulting engineers, contractors, and other building professionals can assist in this process. There are necessary engineering and construction considerations for defining realistic project alternatives. With the alternatives, there are costs, benefits, and trade-offs. The costs, which mainly include the investment and the operational costs, and the benefits, which mainly include the available financial incentives, defined in dollars, are identified for the alternatives. The alternatives can be evaluated with Building Life Cycle Cost (BLCC) software. In this evaluation the net present-value (NPV) method is used to rank the alternatives. Then, the highest-ranking, lowest life-cycle cost, alternative is recommended for the owner. In the example, an existing commercial building’s HVAC systems are considered. The construction plans, the facilities records, and the existing field conditions were investigated and analyzed. A few operational inefficiencies were identified. To address two of these existing inefficiencies, there were alternatives considered to replace the standard-efficiency air handling unit motors with premium-efficiency motors and to renovate the ventilation system with an energy recovery wheel. The investment costs, the available rebates, the net annual energy savings, and the energy and other operational costs were estimated, over a 30-year study period, for each of these alternatives, and compared to the costs of the existing system. The BLCC evaluations were performed across a range of discount rates in the present-value calculations. Based on the lowest present-value life-cycle cost reports, the premium-efficiency motor replacement project only is recommended.Item Facilities Techs Test-Drive Building Automation Simulators(2015-09) Illanes, LauraThe advent of direct digital controls (DDC) has propelled the technology, capability, and complexity of building operations forward over the last 15 years. The combination of DDC and intelligent operating systems combine to create a Building Automation System (BAS). A BAS centralizes the control of a building’s heating, ventilation and air conditioning (HVAC), lighting, and other systems. “Intelligent” buildings improve occupant comfort, provide efficient operation of the building systems, and reduce energy consumption and operating costs. However, they are much more complicated and technical than earlier control systems and require a new generation of employees who are computer literate and technically savvy to maintain and operate them.Item Fault detection and diagnostics modeling for air-handling units on the main campus of The University of Texas at Austin(2019-02-06) McHugh, Megan Kellie; Nagy, Gyorgy ZoltanHeating, ventilation, and air conditioning accounts for about 44% of energy usage in commercial buildings. In HVAC systems, air handling units are used to condition air based on comfort for occupants or controlled environmental requirements. Faults in AHUs can occur due to failures in equipment, actuators, or sensors and feedback controllers. Leakage typically occurs due to faults in ducts, faults with valves that are stuck, broken, or in the incorrect operating position, faults in measurements of state variables, or faults with the controllers maintaining the setpoint from sensor feedback. The variety faults that can occur in AHUs can lead to increased energy consumption, especially when it remains undetected. AHU faults can also lead to uncomfortable conditions for building occupants or impact research and other special facilities as the campus building types include classroom/academic, hospital/clinic, housing, office/administrative, parking/garage, public assembly/multipurpose, and research laboratories. The building automation systems on the main campus of The University of Texas at Austin manage over 100 buildings each with multiple AHUs in different working conditions. In this paper, a methodology is proposed for the fault detection of AHU steam and chilled water valve leakage and for general fault detection and diagnoses of other common AHU faults on the UT campus. The approach is based on supervised machine learning classification models and compared to the ASHRAE fundamentals expert rule-set models. BAS data trended at 15-minute intervals for periods up to 400 days were used. Faults detected through these methods have been validated by UT Facilities Services upon inspection of the faulty AHUs. A dashboard web application was developed for the interactive use and visualization of the fault detection models by UTFS for continuous maintenance prioritization. A classification analysis allows for the prediction of leakage and provides UTFS a priority ranking of AHUs to address for maintenance in the future. The rule-set models provide a method for continuous tracking of AHU features for faults. Identifying and addressing valve leakage and other faults is expected to reduce energy usage and contribute to reduction in average annual energy use intensity in order to improve demand side energy efficiency while maintaining indoor environmental quality. This will contribute to reach the 2020 energy savings targets set in the 2012 UT Austin Campus Master Plan, which outlines a variety of initiatives for sustainable growth through 2030.Item From the Class Room to the Mechanical Room: How Architectural Engineering Students Benefit from a Partnership Between the University’s Faculty and Facilities Engineers(2017-05) Illanes, LauraWhen it comes to teaching architectural engineering students how to design and understand the large and highly technical building systems in institutions, professors often look for opportunities for their students to see the systems where they come “alive” in order to better comprehend how they work. A facility must function well to serve its purpose to its occupants. Like a breathing organism, the electrical, mechanical and heating, ventilation and air conditioning (HVAC) systems pulsing throughout the facility must remain operational. If the systems go down, the facility cannot support its purpose. One of the best ways to help teach this is the definitive “show and tell” where the class room is replaced with the mechanical room. This is the story of how a professor at The University of Texas at Austin helped make abstract concepts concrete in a partnership with the facilities professionals responsible for the university’s building operations. Twice a semester, she takes her students to a tour of two buildings: one that is newer and one that is older in order to compare and contrast the facilities in operation. How does our story begin? How do the tours impact the students?Item MARTINI : smart meter driven estimation of HVAC schedules and energy savings based on WiFi sensing and clustering(2021-09-27) Nweye, Kingsley Etonwana; Nagy, Gyorgy ZoltanHVAC systems account for a significant portion of building energy use. Nighttime setback scheduling is an energy conservation measure where cooling and heating setpoints are increased and decreased respectively during unoccupied periods with the goal of obtaining energy savings. However, knowledge of a building’s real occupancy is required to maximize the success of this measure. In addition, there is the need for a scalable way to estimate energy savings potential from energy conservation measures that is not limited by building specific parameters and experimental or simulation modeling investments. Here, we propose MARTINI, a sMARt meTer drIveN estImation of occupant-derived HVAC schedules and energy savings that leverages the ubiquity of energy smart meters and WiFi infrastructure in commercial buildings. We estimate the schedules by clustering WiFi-derived occupancy data and, energy savings by shifting ramp-up and setback times observed in typical/measured load profiles obtained by clustering smart meter energy data. Our case-study results with five buildings over seven months show an average of 8.1%–10.8% (summer) and 0.2%–5.9% (fall) chilled water energy savings when HVAC system operation is aligned with occupancy. We validate our method with results from building energy performance simulation (BEPS) and find that estimated average savings of MARTINI are within 0.9%–2.4% of the BEPS predictions. In the absence of occupancy information, we can still estimate potential savings from increasing ramp-up time and decreasing setback start time. In 51 academic buildings, we find savings potentials between 1%–5%Item Optimal residential energy consumption, prediction, and analysis(2014-05) Rhodes, Joshua Daniel; Webber, Michael E., 1971-; Blackhurst, Michael F; Edgar, Thomas F; King, Carey; Novoselac, AtilaIn the United States, buildings are responsible for 40.36 Quads (40.36 x 10¹⁵ BTU) of total primary energy consumption per year, 22.15 of which are used in residential buildings (reference year 2010). Also, the United States residential sector is responsible for about 20% of United States carbon emissions or about 4% of the world's total. While there are over 130 million residential units in the United States, only 0.1% of R&D is spent in the residential sector. This means the residential sector represents an underinvested opportunity for energy savings. Tackling that problem, this dissertation presents work that is focused on assessing, analyzing, and optimizing how residential buildings use and generate energy. This work presents an analysis of a unique dataset of 4971 energy audits performed on homes in Austin, Texas in 2009 - 2010. The analysis quantifies the prevalence of typical air-conditioner design and installation issues such as low efficiency, oversizing, duct leakage, and low measured capacity, then estimates the impacts that resolving these issues would have on peak power demand and cooling energy consumption. It is estimated that air-conditioner use in single-family residences currently accounts for 17 - 18% of peak demand in Austin, and that improving equipment efficiency alone could save up to 205 MW, or 8%, of peak demand. It was also found that 31% of systems in this study were oversized, leading to up to 41 MW of excess peak demand. Replacing oversized systems with correctly sized higher efficiency units has the potential for further savings of up to 81 MW. Also, the mean system could achieve 18% and 20% in cooling energy savings by sealing duct leaks and servicing air-conditioning units to achieve 100% of nominal capacity, respectively. A different dataset of measured whole-home electricity consumption from 103 homes in Austin, TX was analyzed to 1) determine the shape of seasonally-resolved residential demand profiles, 2) determine the optimal number of normalized representative residential electricity use profiles within each season, and 3) draw correlations to the different profiles based on survey data from the occupants of the 103 homes. Within each season, homes with similar hourly electricity use patterns were clustered into groups using the k-means clustering algorithm. The number of groups within each season was determined by comparing 30 different optimal clustering criteria. Then probit regression was performed to determine if homeowner survey responses could serve as explanatory variables for the clustering results. This analysis found that Austin homes typically fall into one of two seasonal groups. Because these groups differ in temporal energy use and the wholesale electricity price is temporal, homes in one group use more expensive electricity than others. The probit regression results indicated that variables such as whether or not someone worked from home, the number of hours of television watched per week, and level of education have significant correlation with average profile shape, but that significant indicators of profile shape can vary across seasons. Also, these results point to markers of households that might be more impacted by time-of-use (TOU) or real time price (RTP) electricity rates and can act as predictors as to how changing local demographics can change local electricity demand patterns. This work also considers the effect of the placement (azimuth and tilt) of fixed solar PV systems on their total energy production, peak power production, and economic value given local solar radiation, weather, and electricity market prices and rate structures. This model was then used to calculate the output of solar PV systems across a range of azimuths and tilts to find the energetically and economically optimal placement. The result of this method, which concludes that the optimal placement can vary with a multitude of conditions, challenges the default due-south placement that is conventional for typical installations. For Austin, TX the optimal azimuth to maximize energy production is about 187 - 188°, or 7 - 8° west of south, while the optimal azimuth to maximize economic output based on the value of the solar energy produced is about 200 - 230° or 20 - 50° west of south. The differences between due south (which is the conventional orientation) and the optimal placement were on the order of 1 - 7%. For the rest of the US and for most locations the energetically optimal solar PV azimuth is within 10° of south. Considering the temporal value of the solar energy produced from spatially-resolved market conditions derived from local time-of-use rates, the optimal placement shifts to a west-of-south azimuth in attempt to align solar energy production with higher afternoon prices and higher grid stress times. There are some locations particularly on the west coast that have west-of-south energy optimal placements, possibly due to typical morning clouds or fog. These results have the potential to be significant for solar PV installations: utilities might alter rate structures to encourage solar generation that is more coincident with peak demand, utilities might also use west-of-south solar placements as a hedge against future wholesale electricity price volatility, building codes might encourage buildings to match roof azimuths with local optimal solar PV generation placements, and calculations of the true value of solar in optimal and non-optimal placements can be more accurate. This analysis also uses a dataset of whole home electricity consumption to consider the role of small distributed fuel cells in managing energy and thermal flows in the home. The analysis determines that the average home in Austin, TX could utilize a 5.5 kW fuel cell either for total generation or backup, and the average home could operate as its own micro-grid while not sacrificing core functionality. Matching the thermal output of a possibly smaller fuel cell, used in combined heat and power mode (CHP), to an absorption refrigeration system in place of traditional space cooling further reduces the needed capacity. Lastly, it is estimated that the system efficiency could possibly double by transporting natural gas to the end user to be converted into electricity and heat as compared with traditional methods of using natural gas for power generation followed by electricity delivery. Results from two regression analyses of total energy use and energy use reductions following energy efficiency retrofits are also presented. The first model shows that home size and age were positively correlated with total yearly energy use, but there is significant correlation of reduced yearly energy use with increased energy and water knowledge. This result might lend some support for increased energy and water education campaigns. The second model (retrofit analysis) also provided results that utilities can use to assess the value of residential retrofit rebates as compared to the cost of acquiring energy on the wholesale market. The second model indicates that the current level of rebates is cost effective for the utility (on a $ per kWh offset basis) for all three considered retrofits (air-sealing, attic insulation, and air-conditioner replacement) and the rebates could be increased while still being below the cost of acquiring electricity on the wholesale market. Considering an average of $0.113/kWh for residential electric service, both the air-sealing and increased attic insulation seem to make economic sense for the homeowner given current rebate structures.Item Ozone removal air cleaning devices : test method and performance assessment(2022-11-30) Tang, Mengjia; Novoselac, Atila; Siegel, Jeffrey A.; Corsi, Richard L.; Misztal, Pawel K.; Kinney, Kerry A.Applying ozone removal devices in ventilation systems is an effective way to reduce building occupant exposure to ozone. However, the test method on ozone removal devices has not been fully validated. Little is known about the performance of commercially-available ozone removal devices under realistic usage conditions. Additionally, the device performance in building ventilation systems can be affected by a wide range of environmental and operating conditions. This dissertation aims to 1) assess the test method of ozone removal devices and introduce modifications, 2) evaluate and compare a list of devices and identify important device characteristics, 3) quantify the impact of usage conditions on device performance, and 4) develop a mechanistic model for device performance prediction. A prolonged test protocol “Ozone Stress Test” and several metrics for evaluating device performance were proposed, and results of this new test protocol were compared to the existing ASHRAE Standard 145.2 method. Results show that activated carbon-based devices had a high degradation rate at the beginning of exposure to ozone or exposure to significantly increased ozone, so a short test (i.e., 1-h initial efficiency test and 4-h capacity test in Standard 145.2) overestimated device performance. A total of 14 ozone removal devices that utilize various technologies were tested by the ozone stress test. Results show a wide range of single-pass removal efficiency from 3% to 93% at 70 ppb, and all devices degraded at a slow rate at 500 ppb. The loading and source of carbon had a significant impact on the efficiency of activated carbon filters. The impact of temperature, relative humidity, ozone concentration, approach air speed, and intermittent exposure on the ozone removal performance of activated carbon filters and one metal oxide catalyst filter were systematically evaluated. Within the realistic range, temperature, relative humidity, and ozone concentration had very small effect on device performance, but an increase in air speed decreased efficiency significantly. Activated carbon filters regenerated after a break, while metal oxide did not. The dynamic and quasi-steady-state device performance was successfully explained by a plug flow reactor model.Item Single-zone HVAC systems in k-12 schools : a literature review(2015-12) Muirhead, Loren Alyson; Novoselac, Atila; Xu, YingElementary and secondary schools are an important segment of the U.S. commercial building stock, both in terms of energy consumption and indoor environmental quality. In 2008, K-12 schools spent over 8 billion dollars on utilities, and approximately 30% of schools reported unsatisfactory indoor environmental conditions related to indoor air quality. There is an opportunity to address both of these issues by focusing on HVAC design and operation. Optimizing this particular building system can result in significant cost savings, as well as improved environmental quality for students and teachers. This report explores the existing literature on four single-zone HVAC systems – unit ventilators, fan coils, heat pumps, and package DX rooftop units – and discusses their potential for increased energy efficiency, cost savings, and improved indoor environmental quality.Item Thermal performance in mid/large buildings : in hot, humid climates(2009-10) Galloway, Ross; Brown, MeredithThis paper presents on overview of several vernacular and passive strategies as an alternative to the standard HVAC system. It examines the performance demands of large buildings in Austin, Texas and addresses several potential methods for cooling and dehumidifying buildings, including: preventing solar heat gain, ventilation strategies, ground cooling, convection cooling, desiccant cooling, evaporative cooling, and use of multiple zones.