title: Supercapacitor assisted LED (SCALED) converter technique for solar powered DC-microgrids

authors: Udathenne Gedara, Dilini Udeshika Kumari Jayananda

abstract: Designing electronic products and systems with high energy efficiency is a major challenge for electronic power circuit designers. Almost all residential and industrial buildings are presently AC powered. However, they contain electronic equipment that is internally dependent on a bulk DC power rail with multiple DC-DC converters or DC-AC converters to supply motors controlled by variable speed drives. The overall efficiency of an electronic device with multiple voltage converters is determined by the product of the efficiencies of the individual conversion stages. Thus, overall efficiency drops drastically with the number of converter stages. However, with renewable energy sources such as photovoltaic solar cells generating DC electricity, we can eliminate the first AC-DC converter and reduce the number of converter stages, to achieve a signi ficant rise in end-to-end efficiency. This is the motivation for the DC-microgrid concept. DC-microgrids are local energy networks consisting of renewable energy sources and storage systems.
Although power generation using solar energy is economical, designers have to cope with frequent fluctuations in irradiance and temperature and the non-availability of solar energy at night. Accordingly, there is a need for energy storage for reliable operation. The most common energy storage device used in solar power-based systems is the rechargeable battery pack, typically based on lead-acid and lithium-ion chemistries. However, all rechargeable batteries have limited charge-discharge life cycles as well as calendar lives, and are environmentally unfriendly. With the continuous developments of supercapacitor materials and manufacturing techniques over the last decade, it is now possible to adopt supercapacitors as short-term energy storage devices in solar powered DC-microgrids to replace electrochemical battery packs. When supercapacitors are used in solar power-based DC-microgrid environments, there is the possibility of directly operating \white goods" (such as washing machines, refrigerators, dishwashers and air conditioners) and lighting. However, if a supercapacitor bank is used as the sole energy storage, existing maximum power point tracking schemes are no longer appropriate. This is because the storage bank acts as a near-ideal capacitor, so its impedance depends on its state of charge, unlike a rechargeable battery pack with internal resistance.
The supercapacitor assisted LED lighting (SCALED) converter is a new circuit topology that can be applied to solar powered DC-microgrids. This topology has been developed specially for low voltage LED lighting systems where a supercapacitor bank is used as an efficient energy storage device instead of a battery bank. The SCALED converter is another extension of the supercapacitor assisted loss management concept developed by the Power Electronics research team at the University of Waikato. This thesis presents details of this SCALED conversion system, developed for the Ports of Auckland DC-microgrid lighting systems, including theory and experimental efficiency measurements.

text: Supercapacitor assisted LED (SCALED) converter technique for solar powered DC-microgrids Designing electronic products and systems with high energy efficiency is a major challenge for electronic power circuit designers. Almost all residential and industrial buildings are presently AC powered. However, they contain electronic equipment that is internally dependent on a bulk DC power rail with multiple DC-DC converters or DC-AC converters to supply motors controlled by variable speed drives. The overall efficiency of an electronic device with multiple voltage converters is determined by the product of the efficiencies of the individual conversion stages. Thus, overall efficiency drops drastically with the number of converter stages. However, with renewable energy sources such as photovoltaic solar cells generating DC electricity, we can eliminate the first AC-DC converter and reduce the number of converter stages, to achieve a signi ficant rise in end-to-end efficiency. This is the motivation for the DC-microgrid concept. DC-microgrids are local energy networks consisting of renewable energy sources and storage systems.
Although power generation using solar energy is economical, designers have to cope with frequent fluctuations in irradiance and temperature and the non-availability of solar energy at night. Accordingly, there is a need for energy storage for reliable operation. The most common energy storage device used in solar power-based systems is the rechargeable battery pack, typically based on lead-acid and lithium-ion chemistries. However, all rechargeable batteries have limited charge-discharge life cycles as well as calendar lives, and are environmentally unfriendly. With the continuous developments of supercapacitor materials and manufacturing techniques over the last decade, it is now possible to adopt supercapacitors as short-term energy storage devices in solar powered DC-microgrids to replace electrochemical battery packs. When supercapacitors are used in solar power-based DC-microgrid environments, there is the possibility of directly operating \white goods" (such as washing machines, refrigerators, dishwashers and air conditioners) and lighting. However, if a supercapacitor bank is used as the sole energy storage, existing maximum power point tracking schemes are no longer appropriate. This is because the storage bank acts as a near-ideal capacitor, so its impedance depends on its state of charge, unlike a rechargeable battery pack with internal resistance.
The supercapacitor assisted LED lighting (SCALED) converter is a new circuit topology that can be applied to solar powered DC-microgrids. This topology has been developed specially for low voltage LED lighting systems where a supercapacitor bank is used as an efficient energy storage device instead of a battery bank. The SCALED converter is another extension of the supercapacitor assisted loss management concept developed by the Power Electronics research team at the University of Waikato. This thesis presents details of this SCALED conversion system, developed for the Ports of Auckland DC-microgrid lighting systems, including theory and experimental efficiency measurements.

year: 2020

title: A necessary fiction: The ritualisation of stakeholder practices in New Zealand cinema

authors: Davies, Megan Jane

abstract: This thesis argues that stability of the concept ‘national cinema’ is located in the discursive positioning of individual films in such a way that they are connected to a national ‘common ground’, one which is ritually accessed via engagement with media such as cinema. This positioning, however, is not quantifiable and may not be identified as arising from any particular production practice, dimension of popularity, theme, style, characteristic of production personnel, and so on. By synthesising the work of several theorists and applying this synthesis to a selection of films, a framework of ideas (around the ritualised ‘flagging’ of the national via the expression of stakeholder interests) is applied to cinema in New Zealand. In particular, an ideoscape is ultimately mapped as a result of applying this framework of ideas. The normative assumptions of national cinema are examined in this way and found to be lacking despite the weight that the term ‘national cinema’ continues to have.

text: A necessary fiction: The ritualisation of stakeholder practices in New Zealand cinema This thesis argues that stability of the concept ‘national cinema’ is located in the discursive positioning of individual films in such a way that they are connected to a national ‘common ground’, one which is ritually accessed via engagement with media such as cinema. This positioning, however, is not quantifiable and may not be identified as arising from any particular production practice, dimension of popularity, theme, style, characteristic of production personnel, and so on. By synthesising the work of several theorists and applying this synthesis to a selection of films, a framework of ideas (around the ritualised ‘flagging’ of the national via the expression of stakeholder interests) is applied to cinema in New Zealand. In particular, an ideoscape is ultimately mapped as a result of applying this framework of ideas. The normative assumptions of national cinema are examined in this way and found to be lacking despite the weight that the term ‘national cinema’ continues to have.

year: 2011

title: Activating whanau (extended family) processes within a community and school literacy partnership

authors: Glynn, Ted

subjects: Maori Education

abstract: "The paper describes the positive outcomes of a home and school literacy partnership in one mainstream primary school where the principal and the large majority of students, teachers, and whānau belong to one Māori hapū (sub-tribe), Ngāti Whakaue. Participating students were identified by teachers as experiencing difficulties with reading and writing. They were assigned randomly to one of two conditions: (1) participating in their school’s regular reading programme (school group) or (2) participating also in the home tutored reading and writing programme (home and school group).

Students in the home and school group improved their reading and writing outcomes over and above the outcomes achieved by students participating only in the regular school programme. There were two key reasons for the success of this partnership. The first was parents and whānau members successful implementation of both a Māori language reading tutoring programme, Tatari, Tautoko Tauawhi, and the two components of the writing programme, Tuhi Atu Tui Mai and Whakaputa Whakaaro. The second was the professional educational and cultural expertise of the home and school liaison worker, Hiro. Because of her language and cultural expertise and her mana (acknowledged authority and standing), Hiro was able to engage Māori parents and whānau actively in the home and school project. The co-constructed narrative between Hiro and Mere (the second author) provided a salient context for understanding the power of culturally preferred pedagogy in establishing effective home and school partnerships."

text: Activating whanau (extended family) processes within a community and school literacy partnership "The paper describes the positive outcomes of a home and school literacy partnership in one mainstream primary school where the principal and the large majority of students, teachers, and whānau belong to one Māori hapū (sub-tribe), Ngāti Whakaue. Participating students were identified by teachers as experiencing difficulties with reading and writing. They were assigned randomly to one of two conditions: (1) participating in their school’s regular reading programme (school group) or (2) participating also in the home tutored reading and writing programme (home and school group).

Students in the home and school group improved their reading and writing outcomes over and above the outcomes achieved by students participating only in the regular school programme. There were two key reasons for the success of this partnership. The first was parents and whānau members successful implementation of both a Māori language reading tutoring programme, Tatari, Tautoko Tauawhi, and the two components of the writing programme, Tuhi Atu Tui Mai and Whakaputa Whakaaro. The second was the professional educational and cultural expertise of the home and school liaison worker, Hiro. Because of her language and cultural expertise and her mana (acknowledged authority and standing), Hiro was able to engage Māori parents and whānau actively in the home and school project. The co-constructed narrative between Hiro and Mere (the second author) provided a salient context for understanding the power of culturally preferred pedagogy in establishing effective home and school partnerships."

year: 2004