Matching Items (122)
Filtering by
- All Subjects: energy
- Genre: Masters Thesis
Description
Dynamic loading is the term used for one way of optimally loading a transformer. Dynamic loading means the utility takes into account the thermal time constant of the transformer along with the cooling mode transitions, loading profile and ambient temperature when determining the time-varying loading capability of a transformer. Knowing the maximum dynamic loading rating can increase utilization of the transformer while not reducing life-expectancy, delaying the replacement of the transformer. This document presents the progress on the transformer dynamic loading project sponsored by Salt River Project (SRP). A software application which performs dynamic loading for substation distribution transformers with appropriate transformer thermal models is developed in this project. Two kinds of thermal hottest-spot temperature (HST) and top-oil temperature (TOT) models that will be used in the application--the ASU HST/TOT models and the ANSI models--are presented. Brief validations of the ASU models are presented, showing that the ASU models are accurate in simulating the thermal processes of the transformers. For this production grade application, both the ANSI and the ASU models are built and tested to select the most appropriate models to be used in the dynamic loading calculations. An existing application to build and select the TOT model was used as a starting point for the enhancements developed in this work. These enhancements include: Adding the ability to develop HST models to the existing application, Adding metrics to evaluate the models accuracy and selecting which model will be used in dynamic loading calculation Adding the capability to perform dynamic loading calculations, Production of a maximum dynamic load profile that the transformer can tolerate without acceleration of the insulation aging, Provide suitable output (plots and text) for the results of the dynamic loading calculation. Other challenges discussed include: modification to the input data format, data-quality control, cooling mode estimation. Efforts to overcome these challenges are discussed in this work.
ContributorsLiu, Yi (Author) / Tylavksy, Daniel J (Thesis advisor) / Karady, George G. (Committee member) / Ayyanar, Raja (Committee member) / Arizona State University (Publisher)
Created2011
Description
This thesis pursues a method to deregulate the electric distribution system and provide support to distributed renewable generation. A locational marginal price is used to determine prices across a distribution network in real-time. The real-time pricing may provide benefits such as a reduced electricity bill, decreased peak demand, and lower emissions. This distribution locational marginal price (D-LMP) determines the cost of electricity at each node in the electrical network. The D-LMP is comprised of the cost of energy, cost of losses, and a renewable energy premium. The renewable premium is an adjustable function to compensate `green' distributed generation. A D-LMP is derived and formulated from the PJM model, as well as several alternative formulations. The logistics and infrastructure an implementation is briefly discussed. This study also takes advantage of the D-LMP real-time pricing to implement distributed storage technology. A storage schedule optimization is developed using linear programming. Day-ahead LMPs and historical load data are used to determine a predictive optimization. A test bed is created to represent a practical electric distribution system. Historical load, solar, and LMP data are used in the test bed to create a realistic environment. A power flow and tabulation of the D-LMPs was conducted for twelve test cases. The test cases included various penetrations of solar photovoltaics (PV), system networking, and the inclusion of storage technology. Tables of the D-LMPs and network voltages are presented in this work. The final costs are summed and the basic economics are examined. The use of a D-LMP can lower costs across a system when advanced technologies are used. Storage improves system costs, decreases losses, improves system load factor, and bolsters voltage. Solar energy provides many of these same attributes at lower penetrations, but high penetrations have a detrimental effect on the system. System networking also increases these positive effects. The D-LMP has a positive impact on residential customer cost, while greatly increasing the costs for the industrial sector. The D-LMP appears to have many positive impacts on the distribution system but proper cost allocation needs further development.
ContributorsKiefer, Brian Daniel (Author) / Heydt, Gerald T (Thesis advisor) / Shunk, Dan (Committee member) / Hedman, Kory (Committee member) / Arizona State University (Publisher)
Created2011
Description
The global demand and trade for fruits and vegetables is increasing at national and international levels. The fresh fruits and vegetables supply chain are highly vulnerable to contamination and can be easily spoiled due to their perishable nature. Due to increases in fresh fruit and vegetable trade shipment volume between countries, the fresh food supply chain area is the highly susceptible and frequently prone to food contamination. The inability of firms in the fresh food business to have a good supply chain visibility and tracking system is one of the prominent reasons for food safety failure. Therefore, in order to avoid food safety risk and to supply safe food to consumers, the firms need to have an efficient traceability system in their supply chain. Most of the research in the food supply chain area suggests the implementation of a highly efficient tracking system called RFID (Radio frequency identification) technology to firms in the food industry. The medium scale firms in the fresh food supply chain business are skeptical about implementing the RFID technology equipped traceability system due to its high cost of investment and low margins on fresh food sales. This research developed two methods to measure the probability of food safety risk in food supply chain. These methods use the information gain from RFID traceability systems as a tool to measure the amount of risk in the fresh food supply chain. The stochastic optimization model is applied in this study to determine the risk premium by investing in RFID technology over the electronic barcode traceability system. The results show that there is a reduction in buyer (Type II error) and seller risk (Type I error) for RFID technology employed traceability system compared to electronic barcode system. It is found from stochastic optimization results that there is a positive risk premium by investing in RFID traceability system over the current systems and suggests the implementation of RFID traceability system for complex medium scale fresh produce imports to reduce the food safety risks. This research encourages the food industries and government agencies to evaluate alternatives to update supply chain system with RFID technology.
ContributorsJanke, Deepak Kumar (Author) / Nganje, William (Thesis advisor) / Schmitz, Troy (Committee member) / Thor, Eric (Committee member) / Arizona State University (Publisher)
Created2011
Description
In this thesis the performance of a Hybrid AC System (HACS) is modeled and optimized. The HACS utilizes solar photovoltaic (PV) panels to help reduce the demand from the utility during peak hours. The system also includes an ice Thermal Energy Storage (TES) tank to accumulate cooling energy during off-peak hours. The AC runs continuously on grid power during off-peak hours to generate cooling for the house and to store thermal energy in the TES. During peak hours, the AC runs on the power supplied from the PV, and cools the house along with the energy stored in the TES. A higher initial cost is expected due to the additional components of the HACS (PV and TES), but a lower operational cost due to higher energy efficiency, energy storage and renewable energy utilization. A house cooled by the HACS will require a smaller size AC unit (about 48% less in the rated capacity), compared to a conventional AC system. To compare the cost effectiveness of the HACS with a regular AC system, time-of-use (TOU) utility rates are considered, as well as the cost of the system components and the annual maintenance. The model shows that the HACS pays back its initial cost of $28k in about 6 years with an 8% APR, and saves about $45k in total cost when compared to a regular AC system that cools the same house for the same period of 6 years.
ContributorsJubran, Sadiq (Author) / Phelan, Patrick (Thesis advisor) / Calhoun, Ronald (Committee member) / Trimble, Steve (Committee member) / Arizona State University (Publisher)
Created2011
Description
A low cost expander, combustor device that takes compressed air, adds thermal energy and then expands the gas to drive an electrical generator is to be designed by modifying an existing reciprocating spark ignition engine. The engine used is the 6.5 hp Briggs and Stratton series 122600 engine. Compressed air that is stored in a tank at a particular pressure will be introduced during the compression stage of the engine cycle to reduce pump work. In the modified design the intake and exhaust valve timings are modified to achieve this process. The time required to fill the combustion chamber with compressed air to the storage pressure immediately before spark and the state of the air with respect to crank angle is modeled numerically using a crank step energy and mass balance model. The results are used to complete the engine cycle analysis based on air standard assumptions and air to fuel ratio of 15 for gasoline. It is found that at the baseline storage conditions (280 psi, 70OF) the modified engine does not meet the imposed constraints of staying below the maximum pressure of the unmodified engine. A new storage pressure of 235 psi is recommended. This only provides a 7.7% increase in thermal efficiency for the same work output. The modification of this engine for this low efficiency gain is not recommended.
ContributorsJoy, Lijin (Author) / Trimble, Steve (Thesis advisor) / Davidson, Joseph (Committee member) / Phelan, Patrick (Committee member) / Arizona State University (Publisher)
Created2011
Description
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.
ContributorsEndurthy, Akhilesh Reddy (Author) / Reddy, T Agami (Thesis advisor) / Phelan, Patrick (Committee member) / Addison, Marlin (Committee member) / Arizona State University (Publisher)
Created2011
Description
Arizona has an abundant solar resource and technologically mature systems are available to capture it, but solar energy systems are still considered to be an innovative technology. Adoption rates for solar and wind energy systems rise and fall with the political tides, and are relatively low in most rural areas in Arizona. This thesis tests the hypothesis that a consumer profile developed to characterize the adopters of renewable energy technology (RET) systems in rural Arizona is the same as the profile of other area residents who performed renovations, upgrades or additions to their homes. Residents of Santa Cruz and Cochise Counties who had obtained building permits to either install a solar or wind energy system or to perform a substantial renovation or upgrade to their home were surveyed to gather demographic, psychographic and behavioristic data. The data from 133 survey responses (76 from RET adopters and 57 from non-adopters) provided insights about their decisions regarding whether or not to adopt a RET system. The results, which are statistically significant at the 99% level of confidence, indicate that RET adopters had smaller households, were older and had higher education levels and greater income levels than the non-adopters. The research also provides answers to three related questions: First, are the energy conservation habits of RET adopters the same as those of non-adopters? Second, what were the sources of information consulted and the most important factors that motivated the decision to purchase a solar or wind energy system? And finally, are any of the factors which influenced the decision to live in a rural area in southeastern Arizona related to the decision to purchase a renewable energy system? The answers are provided, along with a series of recommendations that are designed to inform marketers and other promoters of RETs about how to utilize these results to help achieve their goals.
ContributorsPorter, Wayne Eliot (Author) / Reddy, T. Agami (Thesis advisor) / Pasqualetti, Martin (Committee member) / Larson, Kelli (Committee member) / Kennedy, Linda (Committee member) / Arizona State University (Publisher)
Created2011
Description
ABSTRACT The purpose of this study was to determine the energy cost of four modes of resistance training (push-ups, pull-ups, curl-ups, lunges). Twelve well trained men aged 23.6 (SD=2.84) years were recruited to participate in the study. Each of the 12 men completed three trials of each of the four exercises on one visit to the laboratory lasting slightly over one hour (M=72 min, SD=5.9 min). The oxygen consumption of the men was monitored constantly throughout the trial and data was recorded every five seconds. Mean VO2 values were calculated for each exercise. The values for push-ups (M=11.57 ml/kg/min, SD=1.99), curl-ups (M=10.99 ml/kg/min, SD=1.48), pull-ups (M=10.87 ml/kg/min, SD=2.51), and lunges (M=14.18 ml/kg/min, SD=1.78) were converted to METs (Metabolic Equivalents). The MET values (3.31, 3.14, 3.11, and 4.05 respectively) all fall within the range of moderate intensity activity. The findings of this study show that a single set of any of the above exercises will qualify as a moderate intensity activity and can be used to meet recommendations on daily physical activity.
ContributorsVezina, Jesse (Author) / Ainsworth, Barbara (Thesis advisor) / Campbell, Kathryn (Committee member) / Woodruff, Larry (Committee member) / Arizona State University (Publisher)
Created2011
Description
Redundant Binary (RBR) number representations have been extensively used in the past for high-throughput Digital Signal Processing (DSP) systems. Data-path components based on this number system have smaller critical path delay but larger area compared to conventional two's complement systems. This work explores the use of RBR number representation for implementing high-throughput DSP systems that are also energy-efficient. Data-path components such as adders and multipliers are evaluated with respect to critical path delay, energy and Energy-Delay Product (EDP). A new design for a RBR adder with very good EDP performance has been proposed. The corresponding RBR parallel adder has a much lower critical path delay and EDP compared to two's complement carry select and carry look-ahead adder implementations. Next, several RBR multiplier architectures are investigated and their performance compared to two's complement systems. These include two new multiplier architectures: a purely RBR multiplier where both the operands are in RBR form, and a hybrid multiplier where the multiplicand is in RBR form and the other operand is represented in conventional two's complement form. Both the RBR and hybrid designs are demonstrated to have better EDP performance compared to conventional two's complement multipliers. The hybrid multiplier is also shown to have a superior EDP performance compared to the RBR multiplier, with much lower implementation area. Analysis on the effect of bit-precision is also performed, and it is shown that the performance gain of RBR systems improves for higher bit precision. Next, in order to demonstrate the efficacy of the RBR representation at the system-level, the performance of RBR and hybrid implementations of some common DSP kernels such as Discrete Cosine Transform, edge detection using Sobel operator, complex multiplication, Lifting-based Discrete Wavelet Transform (9, 7) filter, and FIR filter, is compared with two's complement systems. It is shown that for relatively large computation modules, the RBR to two's complement conversion overhead gets amortized. In case of systems with high complexity, for iso-throughput, both the hybrid and RBR implementations are demonstrated to be superior with lower average energy consumption. For low complexity systems, the conversion overhead is significant, and overpowers the EDP performance gain obtained from the RBR computation operation.
ContributorsMahadevan, Rupa (Author) / Chakrabarti, Chaitali (Thesis advisor) / Kiaei, Sayfe (Committee member) / Cao, Yu (Committee member) / Arizona State University (Publisher)
Created2011
Description
Photovoltaic (PV) systems are one of the next generation's renewable energy sources for our world energy demand. PV modules are highly reliable. However, in polluted environments, over time, they will collect grime and dust. There are also limited field data studies about soiling losses on PV modules. The study showed how important it is to investigate the effect of tilt angle on soiling. The study includes two sets of mini-modules. Each set has 9 PV modules tilted at 0, 5, 10, 15, 20, 23, 30, 33 and 40°. The first set called "Cleaned" was cleaned every other day. The second set called "Soiled" was never cleaned after the first day. The short circuit current, a measure of irradiance, and module temperature was monitored and recorded every two minutes over three months (January-March 2011). The data were analyzed to investigate the effect of tilt angle on daily and monthly soiling, and hence transmitted solar insolation and energy production by PV modules. The study shows that during the period of January through March 2011 there was an average loss due to soiling of approximately 2.02% for 0° tilt angle. Modules at tilt anlges 23° and 33° also have some insolation losses but do not come close to the module at 0° tilt angle. Tilt anlge 23° has approximately 1.05% monthly insolation loss, and 33° tilt angle has an insolation loss of approximately 0.96%. The soiling effect is present at any tilt angle, but the magnitude is evident: the flatter the solar module is placed the more energy it will lose.
ContributorsCano Valero, José (Author) / Tamizhmani, Govindasamy (Thesis advisor) / Madakannan, Arunachalanadar (Committee member) / Macia, Narciso (Committee member) / Arizona State University (Publisher)
Created2011