Browsing by Author "Horonga, Nyasha"

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Analysis of the dynamic power requirements for controllable energy storage on photovoltaic microgrid
(2016) Horonga, Nyasha
Standalone microgrid studies are being done because an expansion of the existing utility grids to supply power to remote communities is not feasible. Standalone microgrids can be considered as one of the solutions for remote communities because power can be generated close to these communities and it minimizes cost related to power transmission. Renewable energy sources with large uctuations are frequently the source of power for these standalone microgrids. The uctuating nature of these renewable sources can often lead to frequent blackouts. This research is aimed at minimizing power uctuations using controllable energy storage systems. This MSc focuses on the analysis of the ramp rate and delay time requirements for controllable energy storage system used in standalone PV microgrids. Measured insolation data and recorded load demand data for typical domestic appliances are used in this study to analyze ramp rates present. The ramp rates are then used to determine the range of energy storage ramp rate and delay time required to maintain the microgrid voltage within the standardized range of 1pu 5%. From the recorded data it has been observed that PV power can be sampled from at least 1-second intervals without losing important information. The 1 second averaged ramp rates obtained from the insolation data measurements have been found to have the highest value of 0.12pu/sec. However, this ramp rate increases to 0.3pu/sec when the allowable microgrid voltage band is narrow (1pu 5%). These insolation ramp rates are very low compared to the ramp rates of typical loads that can be connected to a microgrid. This means that, if the energy storage system is speci ed to meet the load ramp rate requirements, it will be able to respond to the uctuating PV power. The results obtained from the simulations con rm that energy storage system ramp rate plays an important role in the stability of a standalone microgrid. The minimum allowable energy storage ramp rate was found to be 8.15pu/sec for load transients with a ramp time of 20ms. This value is 28 times the energy storage ramp rate required to cancel out insolation uctuations. This further con rms that energy storage system ramp rates must be speci ed using the load demand data. The maximum allowable delay time was also found to be 0.53s to maintain the microgrid voltage within the standardized range of 1pu 5%. This delay time is applicable when canceling out only the insolation uctuations. To cancel out load transient power uctuations, there should be no delay time.
Consumer perceptions of long-distance ride-sharing services in South Africa
(University of the Witwatersrand, Johannesburg, 2024) Horonga, Nyasha
The research focuses on the analysis of consumer perception towards a long-distance peer-to-peer ridesharing service. Due to the rising cost of living, travelling has become a challenge. While other people are already hitchhiking to reduce spending on travelling, some are a bit hesitant due to the risk associated with it. The research proposes that to address challenges associated with hitchhiking, a platform which only allows those who have been vetted for security purposes can access and share their travelling plans. Such a platform which ideally works if both the driver and the passenger have an intention to travel the same distance is linked to shared travelling costs. Qualitative analysis is used to identify the factors that affect consumer perception towards adoption of long-distance ridesharing services and quantitative analysis is used to analyse and rank the factors. This research examines the seven factors which include: perceived usefulness, perceived risk, perceived ease of use, compatibility, trust, social influence, and facilitating conditions. These factors are analysed to identify the socio-economic attributes that drive them. Results obtained highlight that there is a relationship between perceived usefulness and travelling frequency, age, level of education, ridesharing history and earnings. The younger generation agrees that such a platform is useful while the older and more educated population do not agree. It is believed that this is because they still have enough funds to travel alone. Results also suggest that social influence has a relationship with earnings and age. The older population do not agree that they can be influenced by society when choosing to adopt long-distance ridesharing while the younger generation is more likely to be influenced. Results also show that those with higher levels of education and high-income earners do consider risk as an important factor when adopting ridesharing services while the younger generation is comfortable with the level of risk they are used to in the current ehailing services. Participants in the survey were also asked to rank these factors according to their importance. The ranking was compared to a similar exercise which was done in India. It was found that these rankings are different meaning that studies done in other countries may not necessarily apply in another countr