title: Renewable integration options for remote New Zealand community

authors: Kumar Jayasankar, Naveen

abstract: About 35% of New Zealand’s population lives in rural and remote areas like Whitianga and its nearby settlements. These areas are facing growing electricity demand due to rising population, business activity, and the shift to cleaner transport such as EV and FCEV. This trend is expected to put additional pressure on existing electricity infrastructure and networks, many of which were not built to handle such loads. A potential solution is to utilize local renewable energy sources, such as solar, wind, and green hydrogen, to reduce reliance on the national grid and delay costly infrastructure upgrades.
The first part of the thesis investigates the dynamic behaviour of a PEM electrolyser as a likely component in future integrated renewable energy systems. A Python-based simulation compares the hydrogen production output of dynamic and static models of a PEM under variable solar PV inputs. For the PEM capacity selected, there was a modest difference in cumulative hydrogen output from the dynamic model compared to the static model using one-minute input data over a whole day. Potentially, the dynamic model provides a more accurate way to size electrolyser and associated units like compressor and hydrogen storage vessels with the fluctuating electrical input conditions.
The second part evaluates the use of rooftop solar PV, wind, and hybrid solar-wind systems integrated with green hydrogen into a single residential house to achieve various levels of self-sufficiency over a full year. The study models energy balance, hydrogen storage, and levelized cost of energy (LCOE) for a range of system sizes, showing that 100% self-sufficiency is achievable in all three options, but only at extremely high LCOE levels between 0.52 and 0.78 NZD/kWh. Among the options, the hybrid system of solar and wind performs best, achieving complete self-sufficiency (100%) at the lowest cost of 0.52 NZD/kWh while balancing energy generation and storage needs with demand.
The third part presents a case study of the Whitianga township and region, exploring the integration of solar PV, Vehicle-to-grid (V2G), and green hydrogen to meet future energy demand. A techno-economic assessment examines residential, commercial, and transport energy needs from 2024 to 2050 and evaluates how a 32 MWp solar PV energy system can supply local demand while reducing reliance on the national grid and the need for local transformer upgrades. Two approaches were investigated: a centralised solar farm approach plus local hydrogen production & EV charging demand, and a decentralised residential rooftop solar approach supported by V2G electricity storage. The results indicate that the centralised approach has the lowest LCOE of 0.107 NZD/kWh, while the local grid upgrade remains unavoidable, even with higher solar penetration to the local grid. But in terms of payback period, the decentralised approach has a significant advantage, even with the higher investment cost, especially when V2G is incorporated into the energy management system. The initial investment amount can be recovered in 12.01 years with 20kWh of V2G battery storage.

text: Renewable integration options for remote New Zealand community About 35% of New Zealand’s population lives in rural and remote areas like Whitianga and its nearby settlements. These areas are facing growing electricity demand due to rising population, business activity, and the shift to cleaner transport such as EV and FCEV. This trend is expected to put additional pressure on existing electricity infrastructure and networks, many of which were not built to handle such loads. A potential solution is to utilize local renewable energy sources, such as solar, wind, and green hydrogen, to reduce reliance on the national grid and delay costly infrastructure upgrades.
The first part of the thesis investigates the dynamic behaviour of a PEM electrolyser as a likely component in future integrated renewable energy systems. A Python-based simulation compares the hydrogen production output of dynamic and static models of a PEM under variable solar PV inputs. For the PEM capacity selected, there was a modest difference in cumulative hydrogen output from the dynamic model compared to the static model using one-minute input data over a whole day. Potentially, the dynamic model provides a more accurate way to size electrolyser and associated units like compressor and hydrogen storage vessels with the fluctuating electrical input conditions.
The second part evaluates the use of rooftop solar PV, wind, and hybrid solar-wind systems integrated with green hydrogen into a single residential house to achieve various levels of self-sufficiency over a full year. The study models energy balance, hydrogen storage, and levelized cost of energy (LCOE) for a range of system sizes, showing that 100% self-sufficiency is achievable in all three options, but only at extremely high LCOE levels between 0.52 and 0.78 NZD/kWh. Among the options, the hybrid system of solar and wind performs best, achieving complete self-sufficiency (100%) at the lowest cost of 0.52 NZD/kWh while balancing energy generation and storage needs with demand.
The third part presents a case study of the Whitianga township and region, exploring the integration of solar PV, Vehicle-to-grid (V2G), and green hydrogen to meet future energy demand. A techno-economic assessment examines residential, commercial, and transport energy needs from 2024 to 2050 and evaluates how a 32 MWp solar PV energy system can supply local demand while reducing reliance on the national grid and the need for local transformer upgrades. Two approaches were investigated: a centralised solar farm approach plus local hydrogen production & EV charging demand, and a decentralised residential rooftop solar approach supported by V2G electricity storage. The results indicate that the centralised approach has the lowest LCOE of 0.107 NZD/kWh, while the local grid upgrade remains unavoidable, even with higher solar penetration to the local grid. But in terms of payback period, the decentralised approach has a significant advantage, even with the higher investment cost, especially when V2G is incorporated into the energy management system. The initial investment amount can be recovered in 12.01 years with 20kWh of V2G battery storage.

year: 2025-07-11

title: The effects of terrigenous sediment on the behaviour of Macomona liliana (Bivalvia) in permeable sediments: Implications for porewater exchange

authors: McCartain, Lisa

subjects: Bivalve

abstract: Catastrophic sedimentation events create one off disturbances that can cause mass mortality events in receiving estuaries. In contrast, the deposition of small amounts of terrigenous sediment (TS) is on-going and likely to have long-term consequences for benthic communities who, play important roles in ecosystem functioning. The aim of this thesis was to look at the effects of small amounts of TS on the behaviour of an infaunal deposit-feeding bivalve (Macomona liliana), which may have implications for sediment porewater fluxes and ecosystem functioning. To determine the effect of TS on behaviour, mesocosm experiments in a recirculating flume tank were run. Time lapse imagery was used to capture surface activity, and high resolution pressure sensors were buried within the sediment and captured changes in hydraulic activity. The effect of three TS treatments were tested, low, high and mixed. The low and high treatments were surface additions of TS (0.09 g cm -2 and 0.20 g cm -2, respectively) and represented the initial deposition and build-up of TS. The mixed treatment, mixed 0.20 g cm -2 through the top 2 cm of sediment, to mimic the incorporation of TS into marine sediments over time. Behaviours were observed pre- and post-treatment addition, and were compared to determine the effect of TS on M. liliana behaviour. The surface (top 2 cm) sediment properties were measured to determine the degree of surface modification by the TS treatments.
TS significantly modified the properties of the sediment surface and the hydraulic conductivity. These caused subtle, but significant, changes in some of the behaviours observed in M. liliana, and on a whole, behaviour which bioturbated the sediment surface decreased. Two feeding modes were observed at the surface, deposit-feeding and suspension-feeding/ventilation. There was a switch in feeding modes, from deposit-feeding to suspension-feeding/ventilation, in the low and mixed treatments. The duration of suspension-feeding/ventilation was, on average, three times longer than deposit-feeding, across all treatments, therefore a switch in modes altered the temporal patterns of sediment pressurisation. The amplitude of sediment pressurisation during feeding was significantly increased in the mixed treatment (up to 5× higher) as a result of decreased hydraulic conductivity. Additionally, the pressure signal measured during deposit-feeding was twice that of suspension-feeding/ventilation in the mixed treatment. 
Collectively the short-term changes in M. liliana behaviour are likely to increase sediment stability and the persistence of TS in the environment, potentially causing long-term degradation to habitat and M. liliana condition. As a result of reduced hydraulic conductivity, larger porewater fluxes are likely to be generated in the mixed treatment, and this would be two fold larger during deposit-feeding than in suspension-feeding/ventilation. This paired with the different temporal scales of the two feeding modes, and the observed switches in feeding modes, would have important consequences for geochemical conditions. Rather than short periods of high pressurisation, there would be longer periods of smaller pressurisations, which would increase the duration of sediment oxygenation, but reduce the porewater flux. This is likely to promote more stable geochemical conditions, which when compared to oscillating conditions, has been shown to reduce nutrient recycling and estuarine productivity.

text: The effects of terrigenous sediment on the behaviour of Macomona liliana (Bivalvia) in permeable sediments: Implications for porewater exchange Catastrophic sedimentation events create one off disturbances that can cause mass mortality events in receiving estuaries. In contrast, the deposition of small amounts of terrigenous sediment (TS) is on-going and likely to have long-term consequences for benthic communities who, play important roles in ecosystem functioning. The aim of this thesis was to look at the effects of small amounts of TS on the behaviour of an infaunal deposit-feeding bivalve (Macomona liliana), which may have implications for sediment porewater fluxes and ecosystem functioning. To determine the effect of TS on behaviour, mesocosm experiments in a recirculating flume tank were run. Time lapse imagery was used to capture surface activity, and high resolution pressure sensors were buried within the sediment and captured changes in hydraulic activity. The effect of three TS treatments were tested, low, high and mixed. The low and high treatments were surface additions of TS (0.09 g cm -2 and 0.20 g cm -2, respectively) and represented the initial deposition and build-up of TS. The mixed treatment, mixed 0.20 g cm -2 through the top 2 cm of sediment, to mimic the incorporation of TS into marine sediments over time. Behaviours were observed pre- and post-treatment addition, and were compared to determine the effect of TS on M. liliana behaviour. The surface (top 2 cm) sediment properties were measured to determine the degree of surface modification by the TS treatments.
TS significantly modified the properties of the sediment surface and the hydraulic conductivity. These caused subtle, but significant, changes in some of the behaviours observed in M. liliana, and on a whole, behaviour which bioturbated the sediment surface decreased. Two feeding modes were observed at the surface, deposit-feeding and suspension-feeding/ventilation. There was a switch in feeding modes, from deposit-feeding to suspension-feeding/ventilation, in the low and mixed treatments. The duration of suspension-feeding/ventilation was, on average, three times longer than deposit-feeding, across all treatments, therefore a switch in modes altered the temporal patterns of sediment pressurisation. The amplitude of sediment pressurisation during feeding was significantly increased in the mixed treatment (up to 5× higher) as a result of decreased hydraulic conductivity. Additionally, the pressure signal measured during deposit-feeding was twice that of suspension-feeding/ventilation in the mixed treatment. 
Collectively the short-term changes in M. liliana behaviour are likely to increase sediment stability and the persistence of TS in the environment, potentially causing long-term degradation to habitat and M. liliana condition. As a result of reduced hydraulic conductivity, larger porewater fluxes are likely to be generated in the mixed treatment, and this would be two fold larger during deposit-feeding than in suspension-feeding/ventilation. This paired with the different temporal scales of the two feeding modes, and the observed switches in feeding modes, would have important consequences for geochemical conditions. Rather than short periods of high pressurisation, there would be longer periods of smaller pressurisations, which would increase the duration of sediment oxygenation, but reduce the porewater flux. This is likely to promote more stable geochemical conditions, which when compared to oscillating conditions, has been shown to reduce nutrient recycling and estuarine productivity.

year: 2013

title: Section 2: Native disruption: Maori and the precariat: Introduction

authors: Masters-Awatere, Bridgette

abstract: Within this section, the authors encourage the reader to look back into history and then consider the future. We are invited to re-examine deeds from this country’s past. To immerse ourselves in a narrative that may be different to the one we have been taught in school, or heard among our friends and family. Through their stories we can see multiple narratives. Readers are invited to understand, embrace and own the past. By recognising and accepting the past — our collective histories — we can determine our collective present and future.

text: Section 2: Native disruption: Maori and the precariat: Introduction Within this section, the authors encourage the reader to look back into history and then consider the future. We are invited to re-examine deeds from this country’s past. To immerse ourselves in a narrative that may be different to the one we have been taught in school, or heard among our friends and family. Through their stories we can see multiple narratives. Readers are invited to understand, embrace and own the past. By recognising and accepting the past — our collective histories — we can determine our collective present and future.

year: 2017