title: Effect of flow distribution on the photovoltaic performance of a building integrated photovoltaic/thermal (BIPV/T) collector

authors: Ghani, Faisal Abid

subjects: building integrated

abstract: The phenomenon of non-uniform flow distribution and its influence on thermal performance within a traditional solar thermal collector is well known. Its effect on the photovoltaic conversion of a hybrid photovoltaic/thermal (PV/T) collector however has received little attention. In this study an investigation has been carried out to determine what effect flow distribution will have on the photovoltaic yield of a BIPV/T collector of various size. A three step numerical analysis was conducted to model flow distribution, temperature variation, and photovoltaic yield for a PV/T collector of various design (manifold sizes), geometric shape (aspect ratio), and operating characteristics (mass flow rate and flow direction in manifolds) in order to vary flow uniformity within the collector. The results revealed that flow distribution within the collector will have a significant influence on the photovoltaic performance of a hybrid PV/T collector. For the scenario where flow distribution was most uniform, photovoltaic performance was improved by over 9% in comparison to a traditional photovoltaic (PV) collector operating under the same conditions. For poor flow however, performance was only improved by approximately 2%. Parameters found to influence flow distribution include the manifold to riser pipe ratio where a ratio of 4:1 was found to be ideal and that increasing to a 6:1 ratio offered negligible improvement. Additionally it was found that array geometry (characterised by its aspect ratio in this study) plays an important role on both flow distribution and photovoltaic yield. This study has identified that the optimal mass flow rate is dependent on the shape or aspect ratio of the array.

text: Effect of flow distribution on the photovoltaic performance of a building integrated photovoltaic/thermal (BIPV/T) collector The phenomenon of non-uniform flow distribution and its influence on thermal performance within a traditional solar thermal collector is well known. Its effect on the photovoltaic conversion of a hybrid photovoltaic/thermal (PV/T) collector however has received little attention. In this study an investigation has been carried out to determine what effect flow distribution will have on the photovoltaic yield of a BIPV/T collector of various size. A three step numerical analysis was conducted to model flow distribution, temperature variation, and photovoltaic yield for a PV/T collector of various design (manifold sizes), geometric shape (aspect ratio), and operating characteristics (mass flow rate and flow direction in manifolds) in order to vary flow uniformity within the collector. The results revealed that flow distribution within the collector will have a significant influence on the photovoltaic performance of a hybrid PV/T collector. For the scenario where flow distribution was most uniform, photovoltaic performance was improved by over 9% in comparison to a traditional photovoltaic (PV) collector operating under the same conditions. For poor flow however, performance was only improved by approximately 2%. Parameters found to influence flow distribution include the manifold to riser pipe ratio where a ratio of 4:1 was found to be ideal and that increasing to a 6:1 ratio offered negligible improvement. Additionally it was found that array geometry (characterised by its aspect ratio in this study) plays an important role on both flow distribution and photovoltaic yield. This study has identified that the optimal mass flow rate is dependent on the shape or aspect ratio of the array.

year: 2012

title: Landscape-level variation in stable isotopes of carbon and nitrogen across aquatic ecosystems in New Zealand

authors: Finnerty, Rebecca Catrin

abstract: The stable isotope ratios of carbon (δ¹³C) and nitrogen (δ¹⁵N) are frequently used in food web studies as natural biological indicators for tracking ecological processes, interactions, and energy flows from the basal plant and detrital energy sources to the primary and secondary consumers. The spatial heterogeneity in the ecological, biogeochemical, hydrological, and geomorphological processes of aquatic ecosystems can influence the δ¹³C and δ¹⁵N isotopic baseline of food webs, which directly affect the isotopic composition of primary and secondary consumers. A better understanding of the significant drivers of δ¹³C and δ¹⁵N of aquatic organisms at the landscape scale would facilitate and improve the accuracy of the use of these isotopic ratios as natural tracers.
The main objective of this study was to identify the leading mechanisms influencing the spatial variability of δ¹³C and δ¹⁵N across New Zealand aquatic ecosystems at the landscape scale. The aims of this study were; (1) to review and collate the findings from published stable isotopic studies that investigated the effect of environmental factors on δ¹³C and δ¹⁵N of aquatic organisms, (2) to identify the sources and scales of δ¹³C and δ¹⁵N variability for top-predatory fish across New Zealand lake environments and, (3) to identify the sources and scales of δ¹⁵N variability for top-predatory fish and invertebrates (predatory and non-predatory) across New Zealand stream and river environments. Lake and stream δ¹³C and δ¹⁵N data of aquatic organisms were collated from a range of published and unpublished scientific literature across New Zealand. Data from a total of 88 lakes sourced from 11 publications and 475 stream sites from 15 publications were assessed to investigate the direct and indirect effects of environmental factors on the spatial variability of stable isotopic ratios across lakes and streams. To do so, a combination of correlation analyses, principal component analysis (PCA), and piecewise structural equation modelling (pSEM) were carried out.
The variability of top-predatory fish δ¹³C values across New Zealand lakes was best explained by the morphology of the lake. Fish sampled from lakes with large surface areas and volumes had higher δ¹³C signatures from lakes of smaller morphological size. I hypothesised that larger lakes allow for more influence of δ¹³C-enriched atmospheric CO₂ due to greater equilibration through gas exchange processes and turbulence regimes, contributing to the observed increase in enrichment of fish δ¹³C with lake surface area. The top-predatory fish δ¹⁵N most strongly reflected the watershed land use and showed no apparent relationship with lake size. The variability of non-predatory and predatory invertebrates, and top-predatory fish δ¹⁵N across New Zealand streams was best explained by the local land use in the upstream catchment and the nutrient concentrations, i.e., the total nitrogen and total phosphorus concentrations.
Our findings suggest that δ¹³C and δ¹⁵N respond to different environmental drivers. Carbon isotopic ratios tend to reflect the natural ecosystem properties, whereas nitrogen isotopic ratios respond more readily to the watershed land use. The findings in this study were consistent with previous stable isotopic research conducted in North American and European aquatic ecosystems, which have examined the effects of environmental factors on C and N isotopic ratios among aquatic organisms. An enhanced understanding of the natural ecosystem processes and anthropogenic influences, contributing to the spatial distribution of δ¹³C and δ¹⁵N of aquatic organisms, can improve the study design and interpretation of stable isotopes as a tracer in food web and ecosystem ecology, by taking into account the natural and human-induced spatial and trophic subsidies.

text: Landscape-level variation in stable isotopes of carbon and nitrogen across aquatic ecosystems in New Zealand The stable isotope ratios of carbon (δ¹³C) and nitrogen (δ¹⁵N) are frequently used in food web studies as natural biological indicators for tracking ecological processes, interactions, and energy flows from the basal plant and detrital energy sources to the primary and secondary consumers. The spatial heterogeneity in the ecological, biogeochemical, hydrological, and geomorphological processes of aquatic ecosystems can influence the δ¹³C and δ¹⁵N isotopic baseline of food webs, which directly affect the isotopic composition of primary and secondary consumers. A better understanding of the significant drivers of δ¹³C and δ¹⁵N of aquatic organisms at the landscape scale would facilitate and improve the accuracy of the use of these isotopic ratios as natural tracers.
The main objective of this study was to identify the leading mechanisms influencing the spatial variability of δ¹³C and δ¹⁵N across New Zealand aquatic ecosystems at the landscape scale. The aims of this study were; (1) to review and collate the findings from published stable isotopic studies that investigated the effect of environmental factors on δ¹³C and δ¹⁵N of aquatic organisms, (2) to identify the sources and scales of δ¹³C and δ¹⁵N variability for top-predatory fish across New Zealand lake environments and, (3) to identify the sources and scales of δ¹⁵N variability for top-predatory fish and invertebrates (predatory and non-predatory) across New Zealand stream and river environments. Lake and stream δ¹³C and δ¹⁵N data of aquatic organisms were collated from a range of published and unpublished scientific literature across New Zealand. Data from a total of 88 lakes sourced from 11 publications and 475 stream sites from 15 publications were assessed to investigate the direct and indirect effects of environmental factors on the spatial variability of stable isotopic ratios across lakes and streams. To do so, a combination of correlation analyses, principal component analysis (PCA), and piecewise structural equation modelling (pSEM) were carried out.
The variability of top-predatory fish δ¹³C values across New Zealand lakes was best explained by the morphology of the lake. Fish sampled from lakes with large surface areas and volumes had higher δ¹³C signatures from lakes of smaller morphological size. I hypothesised that larger lakes allow for more influence of δ¹³C-enriched atmospheric CO₂ due to greater equilibration through gas exchange processes and turbulence regimes, contributing to the observed increase in enrichment of fish δ¹³C with lake surface area. The top-predatory fish δ¹⁵N most strongly reflected the watershed land use and showed no apparent relationship with lake size. The variability of non-predatory and predatory invertebrates, and top-predatory fish δ¹⁵N across New Zealand streams was best explained by the local land use in the upstream catchment and the nutrient concentrations, i.e., the total nitrogen and total phosphorus concentrations.
Our findings suggest that δ¹³C and δ¹⁵N respond to different environmental drivers. Carbon isotopic ratios tend to reflect the natural ecosystem properties, whereas nitrogen isotopic ratios respond more readily to the watershed land use. The findings in this study were consistent with previous stable isotopic research conducted in North American and European aquatic ecosystems, which have examined the effects of environmental factors on C and N isotopic ratios among aquatic organisms. An enhanced understanding of the natural ecosystem processes and anthropogenic influences, contributing to the spatial distribution of δ¹³C and δ¹⁵N of aquatic organisms, can improve the study design and interpretation of stable isotopes as a tracer in food web and ecosystem ecology, by taking into account the natural and human-induced spatial and trophic subsidies.

year: 2022

title: Cultural Justice and Ethics

authors: Nikora, Linda Waimarie

subjects: Maori

abstract: Contains the complete proceedings of the Cultural Justice and Ethics symposium held within the Annual Conference of the New Zealand Psychological Society, Wellington, 23rd-24th August, 1993. The responsibility for ensuring that the discipline of psychology is culturally just, is not only that of Maori or some other non-dominant group - the responsibility belongs to all involved in psychology. This collection of papers is about questioning and challenging the psychology that has been adopted from other settings. It is about nurturing and valuing the development of local and indigenous psychologies. It is about developing psychological tools and methods of application that are culturally compatible. It is an invitation to become excited about and instrumental in building a profession and practice in Aotearoa, for Aotearoa.

text: Cultural Justice and Ethics Contains the complete proceedings of the Cultural Justice and Ethics symposium held within the Annual Conference of the New Zealand Psychological Society, Wellington, 23rd-24th August, 1993. The responsibility for ensuring that the discipline of psychology is culturally just, is not only that of Maori or some other non-dominant group - the responsibility belongs to all involved in psychology. This collection of papers is about questioning and challenging the psychology that has been adopted from other settings. It is about nurturing and valuing the development of local and indigenous psychologies. It is about developing psychological tools and methods of application that are culturally compatible. It is an invitation to become excited about and instrumental in building a profession and practice in Aotearoa, for Aotearoa.

year: 1993