Feasibility study of fuel cell residential energy stations

Thesis (S.M.M.O.T.)--Massachusetts Institute of Technology, Sloan School of Management, Management of Technology Program, 2003.Includes bibliographical references.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Electricity provisioning has historically satisfied demand by centralized generation and pervasive distribution through an extensive transmission and distribution network. Once demand increases beyond a fixed threshold, however, the capacity of the generation, transmission and distribution can become crippled and the mal-effects of periodic brownouts and skyrocketing prices may ripple through the nationwide grid system. The traditional response to this constraint is to build new facilities. However, an alternative approach getting increased attention is to satisfy local demands by incrementally investing in distributed generation. Distributed generation facilities can be strategically sited to deliver combined heat and power (CHP) near the source of consumption at unprecedented efficiencies. Presently the distributed generation market remains largely focused on industrial and commercial peak-shaving and emergency back-up applications. The residential market is a frontier yet to be tackled. Residential electricity tariffs, in contrast, are the highest among all sectors and household users are responsible for a large proportion of the peak demand and usage growth. For residential self-generation needs, fuel cell technology is foreseen to be an ideal solution stemming from its low noise, negligible pollution and high efficiency operation. This thesis will assess the market viability of fuel cell technologies for residential distributed generation application. More specifically, the study will consider single household (5 kW) proton exchange membrane fuel cells versus hybrid solid oxide fuel cell with integrated gas turbine (10 kW) technologies for the household end-use and determine the competitiveness and sustainability of each choice.by David Tsay.S.M.M.O.T

A People's History Of Recent Urban Transportation Innovation

Who are the people leading the charge in urban transportation? As our report explains, the short answer is that it takes leaders from three different sectors of urban society to make change happen quickly.First, there needs to be a robust civic vanguard, the more diverse their range of skills and participation, the better. Second, mayors, commissioners and other city leaders need to create the mandate and champion the change. The third sector is the agency staff. When these three sectors align, relatively quick transformation is possible. Several cities, including New York and Pittsburgh, recently experienced this alignment of a healthy civic community, a visionary and bold mayor and transportation head, and internal agency champions. Our report also highlighted the potential of other cities, such as Charlotte, where the civic sector continues to build on and widen their base

Biological Activity of Trimethylselenonium-selenium and Influence of Vitamin E on its In Vivo Formation in Rats Using a Torula Yeast Diet

During recent times, many efforts have been extended to investigate the metabolism of selenium compounds-in microorganisms, animals and plants. Several investigators (1-3) have proposed some hypothetical metabolic pathways for selenium. However, the role of selenium in the life function of animals remains unknown. Liver necrosis, as induced by the feeding of a Torula yeast diet which is unsupplemented with vitamin E and selenium, is known to be a fatal symptom in rats (4-6). The addition of either vitamin E or selenium to the diet is associated with the prevention of this condition. Schwarz (7) has suggested that vitamin E and selenium play their effect on the same syndrome by acting on alternate pathways of one stage in energy metabolism, thus enabling either substance to promote the over-all reaction. Tappel (8) has proposed that either substance acts to stabilize unsaturated lipids in the intact animal, i.e. as antioxidant in preventing lipid peroxidation and accompanying cellular damage. The report that the necrogenic syndrome may occur when rats are fed a diet low in polyunsaturated fat (9) does not appear to support the explanation offered by Tappel

Comparison of The Transformation Temperatures of Heat-Activated Nickel-Titanium Orthodontic Archwires By Two Different Techniques

Objectives The purpose of this study was to investigate the suitability of the Bend and Free Recovery (BFR) method as a standard test method to determine the transformation temperatures of heat-activated Ni-Ti orthodontic archwires. This was done by determining the transformation temperatures of two brands of heat-activated Ni-Ti orthodontic archwires using the both the BFR method and the standard method of Differential Scanning Calorimetry (DSC). The values obtained from the two methods were compared with each other and to the manufacturer-listed values. Methods Forty heat-activated Ni-Ti archwires from both Rocky Mountain Orthodontics (RMO) and Opal Orthodontics (Opal) were tested using BFR and DSC. Round (0.016 inches) and rectangular (0.019 × 0.025 inches) archwires from each manufacturer were tested. The austenite start temperatures (As) and austenite finish temperatures (Af) were recorded. Results For four of the eight test groups, the BFR method resulted in lower standard deviations than the DSC method, and, overall, the average standard deviation for BFR testing was slightly lower than for DSC testing. Statistically significant differences were seen between the transformation temperatures obtained from the BFR and DSC test methods. However, the Af temperatures obtained from the two methods were remarkably similar with the mean differences ranging from 0.0 to 2.1 °C: Af Opal round (BFR 26.7 °C, DSC 27.6 °C) and rectangular (BFR 27.6 °C, DSC 28.6 °C); Af RMO round (BFR 25.5 °C, DSC 25.5 °C) and rectangular (BFR 28.0 °C, DSC 25.9 °C). Significant differences were observed between the manufacturer-listed transformation temperatures and those obtained with BFR and DSC testing for both manufacturers. Significance The results of this study suggest that the Bend and Free Recovery method is suitable as a standard method to evaluate the transformation temperatures of heat-activated Ni-Ti orthodontic archwires

Can HR and H&S work together to bring about sustainable rehabilitation?

Human Resources (HR) practitioners and Occupational Safety and Health (H&S) practitioners work in a variety of ways, in a team together (as in UK Local Authorities often under an HR Manager), in separate silos such as large manufacturing organisations, or HR and/or H&S are outsourced. Any spatial separation is compounded by the fact that HR and H&S have different professional bodies and different systems of accreditation each with their own standards. This paper looks at the outputs from a 2016 survey of the perceptions that H&S professionals have of their HR colleagues in areas such as risk management, H&S training received and leadership on wellbeing ill health initiatives. The feedback identified concerns with regards competence and trust, concerning when in many areas HR managers often ‘control’ H&S advice. The paper goes on to identify occasions where there has been both positive collaboration and conversely a lack of collaboration between professionals. The paper goes on to suggest ways of closer working and initiatives both in the workplace and academia with programmes having credits in both disciplines

Tree ensemble kernels for Bayesian optimization with known constraints over mixed-feature spaces

Tree ensembles can be well-suited for black-box optimization tasks such as algorithm tuning and neural architecture search, as they achieve good predictive performance with little or no manual tuning, naturally handle discrete feature spaces, and are relatively insensitive to outliers in the training data. Two well-known challenges in using tree ensembles for black-box optimization are (i) effectively quantifying model uncertainty for exploration and (ii) optimizing over the piece-wise constant acquisition function. To address both points simultaneously, we propose using the kernel interpretation of tree ensembles as a Gaussian Process prior to obtain model variance estimates, and we develop a compatible optimization formulation for the acquisition function. The latter further allows us to seamlessly integrate known constraints to improve sampling efficiency by considering domain-knowledge in engineering settings and modeling search space symmetries, e.g., hierarchical relationships in neural architecture search. Our framework performs as well as state-of-the-art methods for unconstrained black-box optimization over continuous/discrete features and outperforms competing methods for problems combining mixed-variable feature spaces and known input constraints.Comment: 27 pages, 9 figures, 4 table

Temporal Variation of Aerosol Properties at a Rural Continental Site and Study of Aerosol Evolution through Growth Law Analysis

Aerosol size distributions were measured by a Scanning Mobility Particle Sizer (SMPS) onboard the CIRPAS Twin Otter aircraft during 16 flights at the Southern Great Plains (SGP) site in northern central Oklahoma as part of the Aerosol Intensive Operation period in May, 2003. During the same period a second SMPS was deployed at a surface station and provided continuous measurements. Combined with trace gas measurements at the SGP site and back-trajectory analysis, the aerosol size distributions provided insights into the sources of aerosols observed at the SGP site. High particle concentrations, observed mostly during daytime, were well correlated with the sulfur dioxide (SO2) mixing ratios, suggesting nucleation involving sulfuric acid is likely the main source of newly formed particles at the SGP. Aerosols within plumes originating from wildfires in Central America were measured at the surface site. Vertically compact aerosol layers, which can be traced back to forest fires in East Asia, were intercepted at altitudes over 3000 meters. Analyses of size dependent particle growth rates for four periods during which high cloud coverage was observed indicate growth dominated by volume controlled reactions. Sulfate accounts for 50% to 72% of the increase in aerosol volume concentration; the rest of the volume concentration increase was likely due to secondary organic species. The growth law analyses and meteorological conditions indicate that the sulfate was produced mainly through aqueous oxidation of SO2 in clouds droplets and hydrated aerosol particles