title: Experimental Investigation of the Performance of a Building Integrated Thermal Solar Collector for Domestic Water Heating

authors: Rohorua, William Tou'anga

subjects: BIT

abstract: The recent increased interest in renewable energy has created a need for research in the area of solar technology, particularly solar water heating collectors and systems. In this study a new design of a building integrated thermal (BIT) collector was developed and experimentally tested. The subsequent result of this was the viability of its use in a water heating system for domestic application in a country like New Zealand, can be investigated.

Experimental results showed that the unglazed and glazed collector can achieve thermal efficiencies of 39% and 75%, respectively. A comparison of the glazed BIT with an integrated collector of a similar design showed that the maximum thermal efficiency of 75% was relatively high; however, the downside to this is that high losses also occurred. 

A theoretical viewpoint of the collector showed that the improvement in efficiency was attributed to the high fin efficiency which resulted from using a high thermal conductivity material relative to the integrated collector previously studied. Moreover, the high heat loss from the collector was shown to be a result of the lack of side insulation and the presence of air gaps between the collector and the rear insulation, contributing to the overall heat loss from the collector and system.

A control strategy was also developed for the control of the system and simulated tests showed that the controller was indeed effective in controlling the system. However, it was highlighted that an improvement is needed for the method of simulating the load required by the household. Additionally, transient simulation of the developed system showed that accurate predictions of the systems performance can be made. Moreover, using a hypothetical scenario where the heat loss from the BIT collector-system is reduced, it was shown that a significant improvement in its performance for water heating can be made.

This work has shown that the use of integrated collectors for domestic household heating in New Zealand is indeed viable. The potential for the control of these systems to achieve high efficiencies is also recommended, by using advance control strategies.

text: Experimental Investigation of the Performance of a Building Integrated Thermal Solar Collector for Domestic Water Heating The recent increased interest in renewable energy has created a need for research in the area of solar technology, particularly solar water heating collectors and systems. In this study a new design of a building integrated thermal (BIT) collector was developed and experimentally tested. The subsequent result of this was the viability of its use in a water heating system for domestic application in a country like New Zealand, can be investigated.

Experimental results showed that the unglazed and glazed collector can achieve thermal efficiencies of 39% and 75%, respectively. A comparison of the glazed BIT with an integrated collector of a similar design showed that the maximum thermal efficiency of 75% was relatively high; however, the downside to this is that high losses also occurred. 

A theoretical viewpoint of the collector showed that the improvement in efficiency was attributed to the high fin efficiency which resulted from using a high thermal conductivity material relative to the integrated collector previously studied. Moreover, the high heat loss from the collector was shown to be a result of the lack of side insulation and the presence of air gaps between the collector and the rear insulation, contributing to the overall heat loss from the collector and system.

A control strategy was also developed for the control of the system and simulated tests showed that the controller was indeed effective in controlling the system. However, it was highlighted that an improvement is needed for the method of simulating the load required by the household. Additionally, transient simulation of the developed system showed that accurate predictions of the systems performance can be made. Moreover, using a hypothetical scenario where the heat loss from the BIT collector-system is reduced, it was shown that a significant improvement in its performance for water heating can be made.

This work has shown that the use of integrated collectors for domestic household heating in New Zealand is indeed viable. The potential for the control of these systems to achieve high efficiencies is also recommended, by using advance control strategies.

year: 2013

title: The implications of time on the ground on running economy: Less is not always better

authors: Lussiana, Thibault

subjects: Science & Technology

abstract: A lower duty factor (DF) reflects a greater relative contribution of leg swing to ground contact time during the running step. Increasing time on the ground has been reported in the scientific literature to both increase and decrease the energy cost (EC) of running, with DF reported to be highly variable in runners. As increasing running speed aligns running kinematics more closely with spring-mass model behaviors and re-use of elastic energy, we compared the centre of mass (COM) displacement and EC between runners with a low (DFlow) and high (DFhigh) duty factor at typical endurance running speeds. Forty well-trained runners were divided in two groups based on their mean DF measured across a range of speeds. EC was measured from 4-min treadmill runs at 10, 12, and 14 km·h−1 using indirect calorimetry. Temporal characteristics and COM displacement data of the running step were recorded from 30-s treadmill runs at 10, 12, 14, 16, and 18 km·h−1. Across speeds, DFlow exhibited more symmetrical patterns between braking and propulsion phases in terms of time and vertical COM displacement than DFhigh. DFhigh limited global vertical COM displacements in favor of horizontal progression during ground contact. Despite these running kinematics differences, no significant difference in EC was observed between groups. Therefore, both DF strategies seem energetically efficient at endurance running speeds.

text: The implications of time on the ground on running economy: Less is not always better A lower duty factor (DF) reflects a greater relative contribution of leg swing to ground contact time during the running step. Increasing time on the ground has been reported in the scientific literature to both increase and decrease the energy cost (EC) of running, with DF reported to be highly variable in runners. As increasing running speed aligns running kinematics more closely with spring-mass model behaviors and re-use of elastic energy, we compared the centre of mass (COM) displacement and EC between runners with a low (DFlow) and high (DFhigh) duty factor at typical endurance running speeds. Forty well-trained runners were divided in two groups based on their mean DF measured across a range of speeds. EC was measured from 4-min treadmill runs at 10, 12, and 14 km·h−1 using indirect calorimetry. Temporal characteristics and COM displacement data of the running step were recorded from 30-s treadmill runs at 10, 12, 14, 16, and 18 km·h−1. Across speeds, DFlow exhibited more symmetrical patterns between braking and propulsion phases in terms of time and vertical COM displacement than DFhigh. DFhigh limited global vertical COM displacements in favor of horizontal progression during ground contact. Despite these running kinematics differences, no significant difference in EC was observed between groups. Therefore, both DF strategies seem energetically efficient at endurance running speeds.

year: 2019

title: ‘He reka te wai o te hua pango: The darker the berry the sweeter the juice.' The experiences of Māori women in educational leadership in mainstream secondary schools.

authors: Taukamo, Trudy

subjects: New Zealand leadership

abstract: Although there has been a growing interest in Māori women in educational leadership, the research base in New Zealand is still limited. This study provides insights into the challenges and experiences of four Māori women who occupy a formal leadership position in a mainstream secondary school. It used a qualitative kaupapa Māori research framework. Data were collected using semi-structured one-on-one interview with open-ended questions. The four women were selected from Māori women who currently hold a formal leadership position at a senior management level in a mainstream secondary school and who identify as Māori. The reason for the purposive sample was the critical under-representation of Māori women in formal educational leadership roles. This study revealed three important aspects. Firstly, a person’s upbringing and background has a significant impact on the principles and values which underpin leadership. Secondly, it was evident that a support system whether personal or professional was crucial in a leadership position. Finally, the influences of opportunities and appointments to leadership were important in educational leadership. Clearly, the findings point to a need for a stronger mentoring programme and effective networking of Māori women. Tertiary studies and leadership programs can aid the career pathways for aspiring leaders. However, what is clear is the need for more research specific to the New Zealand context and Māori women.

text: ‘He reka te wai o te hua pango: The darker the berry the sweeter the juice.' The experiences of Māori women in educational leadership in mainstream secondary schools. Although there has been a growing interest in Māori women in educational leadership, the research base in New Zealand is still limited. This study provides insights into the challenges and experiences of four Māori women who occupy a formal leadership position in a mainstream secondary school. It used a qualitative kaupapa Māori research framework. Data were collected using semi-structured one-on-one interview with open-ended questions. The four women were selected from Māori women who currently hold a formal leadership position at a senior management level in a mainstream secondary school and who identify as Māori. The reason for the purposive sample was the critical under-representation of Māori women in formal educational leadership roles. This study revealed three important aspects. Firstly, a person’s upbringing and background has a significant impact on the principles and values which underpin leadership. Secondly, it was evident that a support system whether personal or professional was crucial in a leadership position. Finally, the influences of opportunities and appointments to leadership were important in educational leadership. Clearly, the findings point to a need for a stronger mentoring programme and effective networking of Māori women. Tertiary studies and leadership programs can aid the career pathways for aspiring leaders. However, what is clear is the need for more research specific to the New Zealand context and Māori women.

year: 2011