Pines Calyx Earth Tube Performance

In temperate climates earth tubes achieve increased comfort in summer and the pre-heating of inlet air in winter, reducing the requirement for cooling and heating. This strategy was adopted to pre-temper air entering a small conference centre building in Kent, UK. The earth tube is about 16m long comprising a concrete pipe with an internal diameter of 0.6m. The pipe is located approximately 1.5m below ground level. A very low energy fan at the outlet end draws air through the tube and pushes it through a heat exchanger before it is distributed via ducts in the building. This paper reports on the results of monitoring the earth tube temperatures and air velocities under different weather conditions. Temperature sensors were positioned externally and at both ends of the earth tube. An anemometer was fixed in place 4m from the inlet end. This ‘fixed’ anemometer in the earth tube was calibrated and the velocity profile of the air flow in the tube was established. The air in the tube was found to have an almost uniform velocity profile, which is likely to be caused by the considerable turbulence created by changes in the direction of the tube, and the dimensions of the pipe relative to the flow rate. This indicates that the system was well-designed to maximise the heat exchange potential of the duct. The energy contribution of the earth in pre-heating and pre-cooling the air has been calculated at approximately 500W for each degree Kelvin raised or lowered, compared to only 18W power consumed by the fans. This demonstrates that earth tubes can make a very significant contribution to providing heating and cooling, with very low carbon emissions. Earth tubes are a durable and low-cost method of providing resilience in the face of climate change

Mothering Experiences of Women in Jail

Women make relatively small proportions of incarcerated population worldwide, but the rate at which they have been incarcerated over the past four decades in the U.S. has outpaced that of their male counterparts. Although carceral trends show declining patterns in prison population numbers, the jailed population continues on an upward trend (Bureau of Justice Statistics, 2022), studies have focused more on prison than jail. The disproportional incarceration of women is evident in jails where the majority of women incarcerated are mothers of young children (Sawyer & Bertram, 2022). The current paper explores mothering experiences of women in two Midwestern jails, including those detained before trial and not yet convicted of crime, as well as convicted individuals incarcerated for one year or less. The study utilizes a qualitative research design and data were analyzed from in-depth interviews with incarcerated mothers. The findings discuss the women’s mothering experiences prior to their incarceration, as well as their parenting experiences while in jail. Most of the mothers in the study were not part of their children’s lives before their incarceration meaning that there were intersectional issues in the system that make the mothering experiences hard for the women. The study presents policy implications relating to parental experiences of mothers’ involved in the criminal justice system

Development and advancement of thin CdTe-based solar cells for photovoltaic performance improvements

2020 Fall.Includes bibliographical references.Photovoltaic technologies, with an essentially infinite energy source, large total capacity, and demonstrated cost competitiveness, are well-positioned to meet growing global demand for clean energy. Cadmium-telluride (CdTe) thin-film photovoltaics is advantageous primarily for its direct optical band gap (approximately 1.48 eV) which is well-matched to the standard AM 1.5G solar spectrum, and its high absorption coefficient. These advantages, in tandem with innovations in fabrication and photovoltaic design in the past decade, have significantly increased CdTe photovoltaic device performance and reduced cost. Major advances in CdTe device performance have been achieved through improved current collection and fill factor, however, the open-circuit voltage (VOC) of CdTe devices remains limited compared to the band gap-determined maximum achievable VOC. The voltage deficit could be minimized through various approaches, and this work addresses it through progressive structural changes to a thin CdTe device. Absorbers of less than 2 µm were pursued for ultimate electron-reflector devices which incorporate a wide band-gap material behind the absorber to induce a back-surface field via a back-side conduction-band offset for improved VOC. An optimized and stable base structure is necessary to quantify characteristics and improvements in progressive devices with additional material layers. Thin, 0.4-1.2 µm CdTe absorber devices were optimized and demonstrated respectable and repeatable performance parameters, and a maximum efficiency of 15.0% was achieved with only 1.2 µm CdTe. Capacitance measurements also showed that thinner devices had fully-depleted absorbers into forward bias. To improve device performance through increased current collection, a 1.4-eV band gap CdSeTe layer was introduced as an additional absorber material preceding CdTe. Prior understanding of the effects of the additional CdSeTe material was incomplete, and this work deepens and expands this understanding. Performance improvement was achieved for thin, 1.5-µm absorber devices with no intentional interdiffusion of the CdSeTe and CdTe. The importance of the CdSeTe thickness was demonstrated, where performance was consistently reduced for CdSeTe thickness greater than CdTe thickness, independent of CdSe composition in the close-space sublimation (CSS) CdSeTe source material. Longer time-resolved photoluminescence (TRPL) tail lifetimes in CdSeTe/CdTe devices compared to CdTe devices suggested better bulk properties, and current loss analysis showed that CdSeTe is the dominant absorber in 0.5-µm CdSeTe/1.0-µm devices. 1.5-µm CdSeTe/CdTe devices demonstrated increased current collection and 30-mV voltage deficit reduction due to the 100-meV narrower band gap of CdSeTe compared to CdTe and passivating effects of selenium, for an ultimate efficiency improvement to 15.6%. Lattice-constant matching to CdTe and wide, ~1.8-eV band-gap requirements directed the selection of CdMgTe as the electron-reflector layer. CdMgTe was incorporated into the CdSeTe/CdTe device structure first through CSS, but sputter deposition was found to be more favorable to address the material complexities of CdMgTe (temperature-induced magnesium diffusion and CdCl2 passivation loss, doping, and MgO formation), and produced higher performing CdMgTe electron-reflector devices. Low substrate temperature achievable in sputtered CdMgTe deposition proved the greatest advantage over CSS-CdMgTe: CdCl2 passivation and magnesium can be appropriately maintained with a corresponding maintenance of device performance, whereas temperature-induced CdCl2 passivation loss or magnesium loss will occur for CSS-deposited CdMgTe with incumbent performance reduction. Through low-temperature depositions, doping optimization, and small structural adjustments, 16.0% efficiency was achieved with CdMgTe sputtered on 0.5-µm CdSeTe/1.0-µm CdTe absorbers, the highest-known CdMgTe electron-reflector device performance. The CdMgTe and non-CdMgTe-containing device VOC's suggested that electron reflection was enacted with partial success for the sputter CdMgTe-incorporated structure, but the significant improvements expected based on simulation have not been realized due to MgO formation and a negative valence-band offset which somewhat impedes hole transport to the back contact. Suggestions to overcome or circumvent these limitations are presented and discussed in the context of progressed understanding of CdMgTe electron-reflector devices

Assessing corporate financial distress in South Africa

This study develops a bankruptcy prediction model for South African companies listed on the Johannesburg Stock Exchange. The model is of considerable efficiency and the findings reported extend bankruptcy literature to developing countries. 64 financial ratios for 28 companies, grouped into failed and non-failed companies, were tested using multiple discriminant analysis after conducting normality tests. Three variables were found to be significant which are: Times Interest Earned, Cash to Debt and Working Capital to Turnover. The model correctly classified about 75% of failed and non-failed in the original and cross validation procedures. This study went on to conduct an external validation of the model superiority by introducing a sample of failed companies, which showed that the model predictive accuracy is more than chance. Despite the popularity of the topic among researchers this study highlighted the importance and relevance of the topic to corporate managers, policy makers and to investors especially in a developing market perspective, thereby contributing significantly towards understanding the factors that lead to corporate bankruptcy