title: The effect of colour on the thermal performance of building integrated solar collectors

authors: Anderson, Timothy Nicholas

subjects: solar collectors

abstract: The use of solar collectors with coloured absorbers for water heating is an area of particular interest when considering their integration with buildings. By matching the absorber colour with that of the roof or façade of the building, it is possible to achieve an architecturally and visually pleasing result. Despite the potential for the use of coloured absorbers, very little work has been undertaken in the field.
In this study, the thermal performance of a series of coloured (ranging from white to black), building integrated solar collectors for water heating was examined both theoretically and experimentally. Subsequently, the annual solar fraction for typical water heating systems with coloured absorbers was calculated. The results showed that coloured solar collector absorbers can make noticeable contributions to heating loads. Furthermore, although their thermal efficiency is lower than highly developed selective coating absorbers, they offer the advantage of improved aesthetic integration with buildings.

text: The effect of colour on the thermal performance of building integrated solar collectors The use of solar collectors with coloured absorbers for water heating is an area of particular interest when considering their integration with buildings. By matching the absorber colour with that of the roof or façade of the building, it is possible to achieve an architecturally and visually pleasing result. Despite the potential for the use of coloured absorbers, very little work has been undertaken in the field.
In this study, the thermal performance of a series of coloured (ranging from white to black), building integrated solar collectors for water heating was examined both theoretically and experimentally. Subsequently, the annual solar fraction for typical water heating systems with coloured absorbers was calculated. The results showed that coloured solar collector absorbers can make noticeable contributions to heating loads. Furthermore, although their thermal efficiency is lower than highly developed selective coating absorbers, they offer the advantage of improved aesthetic integration with buildings.

year: 2010

title: Efficiency enhancement to a linear AC voltage regulator: Multi-winding versus multi-transformer design

authors: Wijesooriya, Priyanwada Nimesha

abstract: Electricity distribution companies are required to supply electric power, which conforms to accepted standards, that place limits on voltage fluctuations beyond nominal values. However, it is common for these fluctuations to exceed the specified standards. One solution to this problem is to install stand-alone RMS voltage regulators at the consumer site. Commonly available AC regulators typically have limitations such as slow response time, flattened sine wave output, low efficiency, and limited operating range. The linear AC voltage regulator is a relatively new type of solid-state, single-phase AC regulator for consumer-end, which addresses most of the above issues. It is based on a series transistor-array coupled with a line-frequency transformer that works seamlessly from boost-to-buck mode in the range of 0.8−1.1 per-unit values of line voltage, without a need of any transformer configuration changes. However, previous prototypes exhibited reduced efficiency when the line voltage exceeded the nominal value. This paper presents two alternative designs that achieve efficiencies of 90−95%, usually required in commercial implementation. Analytical and experimental results of a multi-winding versus multi-transformer based prototypes of 300VA output capacity are presented.

text: Efficiency enhancement to a linear AC voltage regulator: Multi-winding versus multi-transformer design Electricity distribution companies are required to supply electric power, which conforms to accepted standards, that place limits on voltage fluctuations beyond nominal values. However, it is common for these fluctuations to exceed the specified standards. One solution to this problem is to install stand-alone RMS voltage regulators at the consumer site. Commonly available AC regulators typically have limitations such as slow response time, flattened sine wave output, low efficiency, and limited operating range. The linear AC voltage regulator is a relatively new type of solid-state, single-phase AC regulator for consumer-end, which addresses most of the above issues. It is based on a series transistor-array coupled with a line-frequency transformer that works seamlessly from boost-to-buck mode in the range of 0.8−1.1 per-unit values of line voltage, without a need of any transformer configuration changes. However, previous prototypes exhibited reduced efficiency when the line voltage exceeded the nominal value. This paper presents two alternative designs that achieve efficiencies of 90−95%, usually required in commercial implementation. Analytical and experimental results of a multi-winding versus multi-transformer based prototypes of 300VA output capacity are presented.

year: 2020-06-18

title: Telomere length in early childhood is associated with sex and ethnicity

authors: Ly, Kien

subjects: Science & Technology

abstract: Telomeres are repetitive DNA sequences at the end of chromosomes that function to protect chromosomes from degradation. Throughout the life course, telomere length decreases with age and is influenced by environmental factors and health conditions. This study aimed to determine the relative telomere lengths in a diverse cohort of about 4000 four-year-old children in New Zealand. Linear regression was used to investigate the relationship between telomere length, child gender, ethnicity, paternal age and deprivation. We observed substantial variation in telomere length according to sex and self-identified ethnicity. Telomere length was longer in females compared to males (coefficient of 0.042, 95% confidence interval (CI) 0.024–0.060). European children had shorter telomere than both the indigenous Māori (coefficient of 0.03, CI 0.007–0.055) and Pacific children (coefficient of 0.15, CI 0.12–0.18). The data suggest that telomere lengths are highly variable and variability between individuals arise from early age, influenced partly by sex and ethnicity. Longer telomeres in indigenous Māori and Pacific children may reflect the heritability of telomere length in genetically less complex populations. This study increases our understanding of telomere dynamics in young children since the majority of telomere studies are conducted in adults.

text: Telomere length in early childhood is associated with sex and ethnicity Telomeres are repetitive DNA sequences at the end of chromosomes that function to protect chromosomes from degradation. Throughout the life course, telomere length decreases with age and is influenced by environmental factors and health conditions. This study aimed to determine the relative telomere lengths in a diverse cohort of about 4000 four-year-old children in New Zealand. Linear regression was used to investigate the relationship between telomere length, child gender, ethnicity, paternal age and deprivation. We observed substantial variation in telomere length according to sex and self-identified ethnicity. Telomere length was longer in females compared to males (coefficient of 0.042, 95% confidence interval (CI) 0.024–0.060). European children had shorter telomere than both the indigenous Māori (coefficient of 0.03, CI 0.007–0.055) and Pacific children (coefficient of 0.15, CI 0.12–0.18). The data suggest that telomere lengths are highly variable and variability between individuals arise from early age, influenced partly by sex and ethnicity. Longer telomeres in indigenous Māori and Pacific children may reflect the heritability of telomere length in genetically less complex populations. This study increases our understanding of telomere dynamics in young children since the majority of telomere studies are conducted in adults.

year: 2019