Matching Items (226)
- All Subjects: energy
- Creators: Arizona State University
- Member of: ASU Electronic Theses and Dissertations
Evaluating different green school building designs for Albania: indoor thermal comfort, energy use analysis with solar systems
Improving the conditions of schools in many parts of the world is gradually acquiring importance. The Green School movement is an integral part of this effort since it aims at improving indoor environmental conditions. This would in turn, enhance student- learning while minimizing adverse environmental impact through energy efficiency of comfort-related HVAC and lighting systems. This research, which is a part of a larger research project, aims at evaluating different school building designs in Albania in terms of energy use and indoor thermal comfort, and identify energy efficient options of existing schools. We start by identifying three different climate zones in Albania; Coastal (Durres), Hill/Pre-mountainous (Tirana), mountainous (Korca). Next, two prototypical school building designs are identified from the existing stock. Numerous scenarios are then identified for analysis which consists of combinations of climate zone, building type, building orientation, building upgrade levels, presence of renewable energy systems (solar photovoltaic and solar water heater). The existing building layouts, initially outlined in CAD software and then imported into a detailed building energy software program (eQuest) to perform annual simulations for all scenarios. The research also predicted indoor thermal comfort conditions of the various scenarios on the premise that windows could be opened to provide natural ventilation cooling when appropriate. This study also estimated the energy generated from solar photovoltaic systems and solar water heater systems when placed on the available roof area to determine the extent to which they are able to meet the required electric loads (plug and lights) and building heating loads respectively.
The results showed that there is adequate indoor comfort without the need for mechanical cooling for the three climate zones, and that only heating is needed during the winter months.
The transition to alternative fuel vehicles (AFVs): an analysis of early adopters of natural gas vehicles and implications for refueling infrastructure location methods
Alternative fuel vehicles (AFVs) have seen increased attention as a way to reduce reliance on petroleum for transportation, but adoption rates lag behind conventional vehicles. One crucial barrier to their proliferation is the lack of a convenient refueling infrastructure, and there is not a consensus on how to locate initial stations. Some approaches recommend placing stations near where early adopters live. An alternate group of methods places stations along busy travel routes that drivers from across the metropolitan area traverse each day. To assess which theoretical approach is most appropriate, drivers of compressed natural gas (CNG) vehicles in Southern California were surveyed at stations while they refueled. Through GIS analysis, results demonstrate that respondents refueled on the way between their origins and destinations ten times more often than they refueled near their home, when no station satisfied both criteria. Freeway interchanges, which carry high daily passing traffic volumes in metropolitan areas, can be appropriate locations for initial stations based on these results. Stations cannot actually be built directly at these interchange sites, so suitable locations on nearby street networks must be chosen. A network GIS method is developed to assess street network locations' ability to capture all traffic passing through 72 interchanges in greater Los Angeles, using deviation from a driver's shortest path as the metric to assess a candidate site's suitability. There is variation in the ability of these locations to capture passing traffic both within and across interchanges, but only 7% of sites near interchanges can conveniently capture all travel directions passing through the interchange, indicating that an ad hoc station location strategy is unlikely to succeed. Surveys were then conducted at CNG stations near freeway interchanges to assess how drivers perceive and access refueling stations in these environments. Through comparative analysis of drivers' perceptions of stations, consideration of their choice sets, and the observed frequency of the use of a freeway to both access and leave these stations, results indicate that initial AFV stations near freeway interchanges can play an important role in regional AFV infrastructure.
The investigation and characterization of the group 3 [NiFe]-Hydrogenases using protein film electrochemistry
Hydrogenases, the enzymes that reversibly convert protons and electrons to hydrogen, are used in all three domains of life. [NiFe]-hydrogenases are considered best suited for biotechnological applications because of their reversible inactivation with oxygen. Phylogenetically, there are four groups of [NiFe]-hydrogenases. The best characterized group, "uptake" hydrogenases, are membrane-bound and catalyze hydrogen oxidation in vivo. In contrast, the group 3 [NiFe]-hydrogenases are heteromultimeric, bifunctional enzymes that fulfill various cellular roles. In this dissertation, protein film electrochemistry (PFE) is used to characterize the catalytic properties of two group 3 [NiFe]-hydrogenases: HoxEFUYH from Synechocystsis sp. PCC 6803 and SHI from Pyrococcus furiosus. First, HoxEFUYH is shown to be biased towards hydrogen production. Upon exposure to oxygen, HoxEFUYH inactivates to two states, both of which can be reactivated on the timescale of seconds. Second, we show that PfSHI is the first example of an oxygen tolerant [NiFe]-hydrogenase that produces two inactive states upon exposure to oxygen. Both inactive states are analogous to those characterized for HoxEFUYH, but oxygen exposed PfSHI produces a greater fraction that reactivates at high potentials, enabling hydrogen oxidation in the presence of oxygen. Third, it is shown that removing the NAD(P)-reducing subunits from PfSHI leads to a decrease in bias towards hydrogen oxidation and renders the enzyme oxygen sensitive. Both traits are likely due to impaired intramolecular electron transfer. Mechanistic hypotheseses for these functional differences are considered.
This thesis addresses the issue of making an economic case for energy storage in power systems. Bulk energy storage has often been suggested for large scale electric power systems in order to levelize load; store energy when it is inexpensive and discharge energy when it is expensive; potentially defer transmission and generation expansion; and provide for generation reserve margins. As renewable energy resource penetration increases, the uncertainty and variability of wind and solar may be alleviated by bulk energy storage technologies. The quadratic programming function in MATLAB is used to simulate an economic dispatch that includes energy storage. A program is created that utilizes quadratic programming to analyze various cases using a 2010 summer peak load from the Arizona transmission system, part of the Western Electricity Coordinating Council (WECC). The MATLAB program is used first to test the Arizona test bed with a low level of energy storage to study how the storage power limit effects several optimization out-puts such as the system wide operating costs. Very high levels of energy storage are then added to see how high level energy storage affects peak shaving, load factor, and other system applications. Finally, various constraint relaxations are made to analyze why the applications tested eventually approach a constant value. This research illustrates the use of energy storage which helps minimize the system wide generator operating cost by "shaving" energy off of the peak demand.
A visual analytics based decision support methodology for evaluating low energy building design alternatives
The ability to design high performance buildings has acquired great importance in recent years due to numerous federal, societal and environmental initiatives. However, this endeavor is much more demanding in terms of designer expertise and time. It requires a whole new level of synergy between automated performance prediction with the human capabilities to perceive, evaluate and ultimately select a suitable solution. While performance prediction can be highly automated through the use of computers, performance evaluation cannot, unless it is with respect to a single criterion. The need to address multi-criteria requirements makes it more valuable for a designer to know the "latitude" or "degrees of freedom" he has in changing certain design variables while achieving preset criteria such as energy performance, life cycle cost, environmental impacts etc. This requirement can be met by a decision support framework based on near-optimal "satisficing" as opposed to purely optimal decision making techniques. Currently, such a comprehensive design framework is lacking, which is the basis for undertaking this research. The primary objective of this research is to facilitate a complementary relationship between designers and computers for Multi-Criterion Decision Making (MCDM) during high performance building design. It is based on the application of Monte Carlo approaches to create a database of solutions using deterministic whole building energy simulations, along with data mining methods to rank variable importance and reduce the multi-dimensionality of the problem. A novel interactive visualization approach is then proposed which uses regression based models to create dynamic interplays of how varying these important variables affect the multiple criteria, while providing a visual range or band of variation of the different design parameters. The MCDM process has been incorporated into an alternative methodology for high performance building design referred to as Visual Analytics based Decision Support Methodology [VADSM]. VADSM is envisioned to be most useful during the conceptual and early design performance modeling stages by providing a set of potential solutions that can be analyzed further for final design selection. The proposed methodology can be used for new building design synthesis as well as evaluation of retrofits and operational deficiencies in existing buildings.
The sun provides Earth with a virtually limitless source of energy capable of sustaining all of humanity's needs. Photosynthetic organisms have exploited this energy for eons. However, efficiently converting solar radiation into a readily available and easily transportable form is complex. New materials with optimized physical, electrochemical, and photophysical properties are at the forefront of organic solar energy conversion research. In the work presented herein, porphyrin and organometallic dyes with widely-varied properties were studied for solar energy applications. In one project, porphyrins and porphyrin-fullerene dyads with aniline-like features were polymerized via electrochemical methods into semiconductive thin films. These were shown to have high visible light absorption and stable physical and electrochemical properties. However, experimentation using porphyrin polymer films as both the light absorber and semiconductor in a photoelectrochemical cell showed relatively low efficiency of converting absorbed solar energy into electricity. In separate work, tetra-aryl porphyrin derivatives were examined in conjunction with wide-bandgap semiconductive oxides TiO2 and SnO2. Carboxylic acid-, phosphonic acid-, and silatrane-functionalized porphyrins were obtained or synthesized for attachment to the metal oxide species. Electrochemical, photophysical, photoelectrochemical, and surface stability studies of the porphyrins were performed for comparative purposes. The order of surface linkage stability on TiO2 in alkaline conditions, from most stable to least, was determined to be siloxane > phosphonate > carboxylate. Finally, porphyrin dimers fused via their meso and beta positions were synthesized using a chemical oxidative synthesis with a copper(II) oxidant. The molecules exhibit strong absorption in the visible and near-infrared spectral regions as well as interesting electrochemical properties suggesting possible applications in light harvesting and redox catalysis.
Building Envelope includes walls, roofs and openings, which react to the outdoor environmental condition. Today, with the increasing use of glass in building envelope, the energy usage of the buildings is increasing, especially in the offices and commercial buildings. Use of right glass type and control triggers helps to optimize the energy use, by tradeoff between optical and thermal properties. The part of the research looks at the different control triggers and its range that governs the use of electrochromic glass to regulate the energy usage in building. All different control trigger that can be possibly used for regulating the clear and tint state of glass were analyzed with most appropriate range. Its range was triggered such that 80% time of the glass is trigger between the ranges. The other building parameters like window wall ratio and orientations were also investigated. The other half of the research study looks into the feasibility of using the Electrochromic windows, as it is ought to be the main factor governing the market usage of Electrochromic windows and to investigate the possible ways to make it feasible. Different LCC parameters were studied to make it market feasible product. This study shows that installing this technology with most appropriate trigger range can reduce annual building energy consumption from 6-8% but still cost of the technology is 3 times the ASHRAE glass, which results in 70-90 years of payback. This study concludes that south orientation saves up to 3-5% of energy and 4-6% of cooling tons while north orientation gives negligible saving using EC glass. LCC parameters show that there is relative change in increasing the net saving for different parameters but none except 50% of the present glass cost is the possible option where significant change is observed.
Development of transition metal macrocyclic-catalysts supported on multi-walled carbon nanotubes for alkaline membrane fuel cell
Low temperature fuel cells are very attractive energy conversion technology for automotive applications due to their qualities of being clean, quiet, efficient and good peak power densities. However, due to high cost and limited durability and reliability, commercialization of this technology has not been possible as yet. The high fuel cell cost is mostly due to the expensive noble catalyst Pt. Alkaline fuel cell (AFC) systems, have potential to make use of non-noble catalysts and thus, provides with a solution of overall lower cost. Therefore, this issue has been addressed in this thesis work. Hydrogen-oxygen fuel cells using an alkaline anion exchange membrane were prepared and evaluated. Various non-platinum catalyst materials were investigated by fabricating membrane-electrode assemblies (MEAs) using Tokuyama membrane (# A201) and compared with commercial noble metal catalysts. Co and Fe phthalocyanine catalyst materials were synthesized using multi-walled carbon nanotubes (MWCNTs) as support materials. X-ray photoelectron spectroscopic study was conducted in order to examine the surface composition. The electroreduction of oxygen has been investigated on Fe phthalocyanine/MWCNT, Co phthalocyanine/MWCNT and commercial Pt/C catalysts. The oxygen reduction reaction kinetics on these catalyst materials were evaluated using rotating disk electrodes in 0.1 M KOH solution and the current density values were consistently higher for Co phthalocyanine based electrodes compared to Fe phthalocyanine. The fuel cell performance of the MEAs with Co and Fe phthalocyanines and Tanaka Kikinzoku Kogyo Pt/C cathode catalysts were 100, 60 and 120 mW cm-2 using H22 and O2 gases. This thesis also includes work on synthesizing nitrogen doped MWCNTs using post-doping and In-Situ methods. Post-doped N-MWNCTs were prepared through heat treatment with NH4OH as nitrogen source. Characterization was done through fuel cell testing, which gave peak power density ~40mW.cm-2. For In-Situ N-MWCT, pyridine was used as nitrogen source. The sample characterization was done using Raman spectroscopy and RBS, which showed the presence ~3 at.% of nitrogen on the carbon surface.
Development of platinum-copper core-shell nanocatalyst on multi-walled carbon nanotubes for proton exchange membrane fuel cells
With a recent shift to a more environmentally conscious society, low-carbon and non-carbon producing energy production methods are being investigated and applied all over the world. Of these methods, fuel cells show great potential for clean energy production. A fuel cell is an electrochemical energy conversion device which directly converts chemical energy into electrical energy. Proton exchange membrane fuel cells (PEMFCs) are a highly researched energy source for automotive and stationary power applications. In order to produce the power required to meet Department of Energy requirements, platinum (Pt) must be used as a catalyst material in PEMFCs. Platinum, however, is very expensive and extensive research is being conducted to develop ways to reduce the amount of platinum used in PEMFCs. In the current study, three catalyst synthesis techniques were investigated and evaluated on their effectiveness to produce platinum-on copper (Pt@Cu) core-shell nanocatalyst on multi-walled carbon nanotube (MWCNT) support material. These three methods were direct deposition method, two-phase surfactant method, and single-phase surfactant method, in which direct deposition did not use a surfactant for particle size control and the surfactant methods did. The catalyst materials synthesized were evaluated by visual inspection and fuel cell performance. Samples which produced high fuel cell power output were evaluated using transmission electron microscopy (TEM) imaging. After evaluation, it was concluded that the direct deposition technique was effective in synthesizing Pt@Cu core-shell nanocatalyst on MWCNTs support when a rinsing process was used before adding platinum. The peak power density achieved by the rinsed core-shell catalyst was 618 mW.cm-2 , 13 percent greater than that of commercial platinum-carbon (Pt/C) catalyst. Transmission electron microscopy imaging revealed the core-shell catalyst contained Pt shells and platinum-copper alloy cores. Rinsing with deionized (DI) water was shown to be a crucial step in core-shell catalyst deposition as it reduced the number of platinum colloids on the carbon nanotube surface. After evaluation, it was concluded that the two-phase surfactant and single-phase surfactant synthesis methods were not effective at producing core-shell nanocatalyst with the parameters investigated.
Development of nanosphere lithography technique with enhanced lithographical accuracy on periodic Si nanostructure for thin Si solar cell application
In this thesis, a novel silica nanosphere (SNS) lithography technique has been developed to offer a fast, cost-effective, and large area applicable nano-lithography approach. The SNS can be easily deposited with a simple spin-coating process after introducing a N,N-dimethyl-formamide (DMF) solvent which can produce a highly close packed SNS monolayer over large silicon (Si) surface area, since DMF offers greatly improved wetting, capillary and convective forces in addition to slow solvent evaporation rate. Since the period and dimension of the surface pattern can be conveniently changed and controlled by introducing a desired size of SNS, and additional SNS size reduction with dry etching process, using SNS for lithography provides a highly effective nano-lithography approach for periodically arrayed nano-/micro-scale surface patterns with a desired dimension and period. Various Si nanostructures (i.e., nanopillar, nanotip, inverted pyramid, nanohole) are successfully fabricated with the SNS nano-lithography technique by using different etching technique like anisotropic alkaline solution (i.e., KOH) etching, reactive-ion etching (RIE), and metal-assisted chemical etching (MaCE).
In this research, computational optical modeling is also introduced to design the Si nanostructure, specifically nanopillars (NPs) with a desired period and dimension. The optical properties of Si NP are calculated with two different optical modeling techniques, which are the rigorous coupled wave analysis (RCWA) and finite-difference time-domain (FDTD) methods. By using these two different optical modeling techniques, the optical properties of Si NPs with different periods and dimensions have been investigated to design ideal Si NP which can be potentially used for thin c-Si solar cell applications. From the results of the computational and experimental work, it was observed that low aspect ratio Si NPs fabricated in a periodic hexagonal array can provide highly enhanced light absorption for the target spectral range (600 ~ 1100nm), which is attributed to (1) the effective confinement of resonant scattering within the Si NP and (2) increased high order diffraction of transmitted light providing an extended absorption length. From the research, therefore, it is successfully demonstrated that the nano-fabrication process with SNS lithography can offer enhanced lithographical accuracy to fabricate desired Si nanostructures which can realize enhanced light absorption for thin Si solar cell.