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This thesis aims to model and validate, Fiji’s wind resources with high spatial and temporal resolution at applicable wind turbine hub-heights, to evaluate the potential of wind energy to support Fiji in utility-scale electrical power generation, and to assist in future wind energy planning and development. The thesis consists of three major parts split into six primary chapters: first, the microscale assessment and evaluation of local wind resources of Fiji using the available measured wind data from thirty automatic weather stations for utility-scale wind power applications and an analysis of the 10 MW Butoni wind farm in Fiji; second, the evaluation of the Weather Research and Forecasting (WRF) model for simulating surface winds and the diurnal cycle, a grid sensitivity study of the WRF model, and a high-resolution mesoscale wind resource assessment of Fiji for a recent decade (2009 - 2018); and finally, the evaluation of the mesoscale-microscale (WRF-WAsP (Wind Atlas Analysis and Application Program)) coupling methodology for wind energy in Fiji and the evaluation of the potential of wind energy for utility-scale wind power applications using the WRF-WAsP coupling methodology at identified wind resource sites. For the microscale wind-resource assessment using WAsP at thirty automatic weather stations (AWS) locations, the results revealed three potential sites of Rakiraki, Nabouwalu and Udu with utility-scale wind resource (NREL Wind Power Class 3 and above). Each of the sites can accommodate a minimum installed capacity of 10 MW wind farm using Vergnet 275 kW wind turbines to support the national electricity grid network in Fiji. For the Butoni wind farm analysis, the results revealed that the main reason for the under-performance of the wind farm is that it is commissioned on a weak wind speed regime (of NREL Wind Power Class 1). The wind farm has a low-capacity factor (~ 5.4 %) and a high wind shear coefficient (0.35), which are also contributing factors to the wind farm underperformance. This part of the research supports the idea that proper wind farm project planning via wind resource and economic viability assessments prior to the installation of a grid-connected wind farm project in the small island developing states (SIDSs) of the Pacific are required. For the evaluation of the WRF model for simulating surface winds at a grid resolution of 1.33 km × 1.33 km, the results revealed that the WRF model is able to accurately capture the surface winds and the diurnal cycle of wind speed on the windward sides of Viti Levu and Vanua Levu. Surface winds on the leeward side and the outer islands, show positive bias especially at night-time for January and both the day and night-time for July, despite adjusting some of the physics settings, showing the limitations of the model and the need for a grid sensitivity study. For the grid sensitivity study, the results revealed that the optimal grid resolution for simulating the surface winds and its diurnal cycle for Fiji is d03 = 1 km × 1 km. The WRF model is able to capture the surface winds and its diurnal cycle more accurately for the higher grid resolution of 1 km × 1 km in comparison with simulations conducted using a grid resolution of 1.33 km × 1.33 km. This indicates that the topography is better resolved in the higher grid resolution. Therefore, the grid resolution of 1 km × 1 km in the grid set up of 15 km – 5 km – 1 km (d01 – d02 – d03) is the optimal grid set-up for the long-term integration of the mesoscale wind resource assessment of Fiji. For the recent decade (2009 - 2018) mesoscale wind-resource assessment using the optimal grid resolution and grid set-up in the WRF model, the results revealed that the WRF model simulated wind-resource parameters are in good agreement with the observations. The model can be reliably used to simulate the wind flow around the Fijian Islands in order to get reliable information on the wind-resource. Higher wind speeds are observed during austral winter than during austral summer. Forty high wind-resource areas are identified with mean wind speeds and power densities greater than 6.4 m/s and 300 W/m2 (Wind Power Class 3) respectively, which were previously unknown. An estimated 1000 MW theoretical potential installed capacity is therefore available for utility-scale wind power applications on Viti Levu and Vanua Levu. For the mesoscale-microscale (WRF-WAsP) coupling, a methodology was proposed and assessed. It was found that the proposed methodology can be used as a wind-resource assessment methodology provided very-high resolution dynamically downscaled wind resource data is available in the order of 10 years for utility-scale wind power applications. The analysis also revealed that the 1 km × 1 km WRF model data from d03 is best for coupling WRF-WAsP for resource mapping and evaluation. The coupling methodology of WRF-WAsP improved the accuracy of the wind prediction by 0.2 – 6 % for the wind resource parameters for Fiji. Using the WRF-WAsP coupling methodology with the decade-long high-resolution (1 km × 1 km) wind resource data at resource sites in WAsP, it was estimated that Fiji has a potential installed capacity of 720 MW with 2114 GWh electricity generation capacity from wind energy. Even if a quarter of the potential installed capacity is installed over a decade at the identified potential wind resource sites, Fiji can achieve its target of generating 100 % electricity generation from renewable energy resources. Therefore, as the first mesoscale and mesoscale-microscale coupling exercise for the SIDS of Fiji for the recent decade (2009 – 2018), the study supports the idea that the SIDS in the Pacific can utilize their wind resource to ease dependence on diesel-based power generation and can even support 100 % electricity generation in the case of Fiji from renewable energy sources. The thesis provides a methodology for mesoscale wind-resource assessment for the SIDS in the Southwest Pacific together with the identification and verification of potential wind resource sites. Furthermore, it provides a methodology for mesoscale-microscale coupled wind-resource assessment for the SIDS in the Southwest Pacific with an evaluation of the potential wind resource and economic analysis for future wind energy planning and development in Fiji. These works can be extended to other SIDS of the Southwest Pacific region. |
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