title: Investigation of thermal aspects of building integrated photovoltaic/thermal solar collectors

authors: Anderson, Timothy Nicholas

subjects: photovoltaic thermal

abstract: In this study a novel building integrated photovoltaic/thermal (BIPVT) solar collector was developed, tested, modelled and optimised both experimentally and theoretically. Experimental testing found that glazing the prototype collector improved the maximum thermal efficiency by approximately 25% and decreased heat loss, by a factor of two, relative to an unglazed collector. Additionally, the spectral absorptance of a photovoltaic (PV) cell and several coloured absorber samples were characterised.

The experimental data was subsequently used in the development and validation of an optimisation model for BIPVT style collectors. Numerical optimisation showed that the collector thermal efficiency could be improved by maximising the geometric fin efficiency, reducing the thermal resistance between the PV cells and the absorber, and by increasing the transmittance-absorptance product of the PV cells and/or the absorber. The results showed that low cost materials, such as mild steel, could be used without significantly affecting the BIPVTs thermal efficiency. It was also shown that there was potential to develop coloured BIPVT collectors with acceptable thermal efficiencies. Finally, the model showed that potentially the air space in an attic could be used rather than  traditional  insulating materials.

Subsequent computational and experimental fluid dynamics studies found that the heat transfer coefficients in a scale-model attic would result in R-values similar to mineral wool type insulation and therefore may provide sufficient insulation of a BIPVT in a cold roof building. In these studies the validity of an existing correlation for natural convection in an attic-shaped enclosure was extended to Grashof numbers in the range 10^7 to 10^9 from its previous range, 2.9 x 10^6 to 9 x 10^6. 

The use of a single vertically mounted baffle was also found to reduce the natural convection heat transfer coefficients in attic-shaped enclosures. This led to the development of a new generalised correlation that can be used to determine the Nusselt number in an attic-shaped enclosure with regard to the proportions of the baffle.

This work has shown that it is possible to achieve satisfactory thermal performance from BIPVT style collectors fabricated from low cost materials such as colour coated mild steel. Further it has demonstrated that there is potential to reduce the cost of such systems by integrating them into a building rather than onto a building.

text: Investigation of thermal aspects of building integrated photovoltaic/thermal solar collectors In this study a novel building integrated photovoltaic/thermal (BIPVT) solar collector was developed, tested, modelled and optimised both experimentally and theoretically. Experimental testing found that glazing the prototype collector improved the maximum thermal efficiency by approximately 25% and decreased heat loss, by a factor of two, relative to an unglazed collector. Additionally, the spectral absorptance of a photovoltaic (PV) cell and several coloured absorber samples were characterised.

The experimental data was subsequently used in the development and validation of an optimisation model for BIPVT style collectors. Numerical optimisation showed that the collector thermal efficiency could be improved by maximising the geometric fin efficiency, reducing the thermal resistance between the PV cells and the absorber, and by increasing the transmittance-absorptance product of the PV cells and/or the absorber. The results showed that low cost materials, such as mild steel, could be used without significantly affecting the BIPVTs thermal efficiency. It was also shown that there was potential to develop coloured BIPVT collectors with acceptable thermal efficiencies. Finally, the model showed that potentially the air space in an attic could be used rather than  traditional  insulating materials.

Subsequent computational and experimental fluid dynamics studies found that the heat transfer coefficients in a scale-model attic would result in R-values similar to mineral wool type insulation and therefore may provide sufficient insulation of a BIPVT in a cold roof building. In these studies the validity of an existing correlation for natural convection in an attic-shaped enclosure was extended to Grashof numbers in the range 10^7 to 10^9 from its previous range, 2.9 x 10^6 to 9 x 10^6. 

The use of a single vertically mounted baffle was also found to reduce the natural convection heat transfer coefficients in attic-shaped enclosures. This led to the development of a new generalised correlation that can be used to determine the Nusselt number in an attic-shaped enclosure with regard to the proportions of the baffle.

This work has shown that it is possible to achieve satisfactory thermal performance from BIPVT style collectors fabricated from low cost materials such as colour coated mild steel. Further it has demonstrated that there is potential to reduce the cost of such systems by integrating them into a building rather than onto a building.

year: 2009

title: Laptops for teachers: practices and possibilities

authors: Cowie, Bronwen

subjects: teachers’ laptops

abstract: The Laptops for Teachers scheme in New Zealand provides teachers whose schools opt into the scheme access to a laptop for their exclusive use. This paper reports on the findings of the three‐year evaluation of the impact of the laptops on secondary teachers’ work. The findings indicate that school leadership has been pivotal to the provision of the technological infrastructure and organisational support needed for teacher use of the laptops. Departmental leadership has been crucial in supporting teacher use of laptops for teaching and learning. Teachers described gains in expertise, indicating that they used the laptop for a range of purposes to support their teaching. These included lesson planning and preparation, and reporting. Where teachers had easy access to a laptop‐plus‐data projector they found that students responded to material that included images and up‐to‐date real‐world examples. Colleagues were identified as the main source of professional development for the use of the laptop for teaching purposes. The findings of the study suggest schools are advised to consider how to support teachers to work collaboratively to share expertise as a way of supporting and extending teacher use of laptops.

text: Laptops for teachers: practices and possibilities The Laptops for Teachers scheme in New Zealand provides teachers whose schools opt into the scheme access to a laptop for their exclusive use. This paper reports on the findings of the three‐year evaluation of the impact of the laptops on secondary teachers’ work. The findings indicate that school leadership has been pivotal to the provision of the technological infrastructure and organisational support needed for teacher use of the laptops. Departmental leadership has been crucial in supporting teacher use of laptops for teaching and learning. Teachers described gains in expertise, indicating that they used the laptop for a range of purposes to support their teaching. These included lesson planning and preparation, and reporting. Where teachers had easy access to a laptop‐plus‐data projector they found that students responded to material that included images and up‐to‐date real‐world examples. Colleagues were identified as the main source of professional development for the use of the laptop for teaching purposes. The findings of the study suggest schools are advised to consider how to support teachers to work collaboratively to share expertise as a way of supporting and extending teacher use of laptops.

year: 2011

title: Investigating Māori approaches to trauma informed care

authors: Pihama, Leonie

subjects: Māori health and wellbeing

abstract: This article gives an overview of a three-year Health Research Council funded research project “He Oranga Ngākau: Māori approaches to trauma-informed care”. The study is informed by Kaupapa Māori which provides both the theoretical and methodological foundation for understanding the world, exploring and conceptualising issues. The need for contextualised and culturally safe health and social services is well recognised within Aotearoa and particularly within Mental Health and Addiction Services. While trauma is an experience that can impact on all people, Māori experience trauma in distinct ways that are linked to the experience of colonisation, racism and discrimination, negative stereotyping and subsequent unequal rates of violence, poverty and ill health. Given that Māori are impacted by trauma in specific ways, it is important to explore and identify practice principles that contribute to the development of a framework that supports Māori Providers, counsellors, clinicians and healers in working with Māori. (Authors' abstract).

text: Investigating Māori approaches to trauma informed care This article gives an overview of a three-year Health Research Council funded research project “He Oranga Ngākau: Māori approaches to trauma-informed care”. The study is informed by Kaupapa Māori which provides both the theoretical and methodological foundation for understanding the world, exploring and conceptualising issues. The need for contextualised and culturally safe health and social services is well recognised within Aotearoa and particularly within Mental Health and Addiction Services. While trauma is an experience that can impact on all people, Māori experience trauma in distinct ways that are linked to the experience of colonisation, racism and discrimination, negative stereotyping and subsequent unequal rates of violence, poverty and ill health. Given that Māori are impacted by trauma in specific ways, it is important to explore and identify practice principles that contribute to the development of a framework that supports Māori Providers, counsellors, clinicians and healers in working with Māori. (Authors' abstract).

year: 2017