RINA was appointed by international developer Neoen to undertake an Independent Energy Yield Assessment (EYA) for its 100 MW Hornsdale 1 and 100 MW Hornsdale 2 Wind Farms currently under construction, and the new neighbouring 100 MW Hornsdale 3 Wind Farm to be constructed in Southern Australia.
Both of the projects under construction have a capacity of greater than 100 MW, with wind turbines located across an area of approximately 15 km x 8 km in medium complexity terrain. Turbines are located at elevations spanning a 230m vertical range, with some steep slopes resulting in areas of potential flow separation and additional complexity.
Due to the close proximity of the turbines, wake impacts were likely to be significant. Therefore, a key focus of the analysis, over and above the accurate prediction of energy yield was the quantification of the impact of one project on the other. RINA's extensive experience in the wake modelling of large onshore and offshore projects was therefore required.
Site specific wind turbine power curve guarantees, performance warranties and contract structure details were provided for the project, and we used this information to strengthen the loss assumptions for both projects. Details regarding site specific turbine technologies resulted in a detailed analysis of the expected temperature de-rating losses and power curve performance issues on a time series basis, further reducing uncertainties.
The measurement of meteorological data on location was substantial, with the use of four masts across the proposed area in addition to a roaming SoDAR. Mast data covered a period of five years, providing valuable insight into inter-annual conditions and variation. Masts were located centrally to key turbine cluster areas, allowing RINA to undertake multiple cross predictions between masts to assist in the validation of the performance of the flow model.
Wind flow across the site was noted to be strongly influenced by meteorological effects that are generally not accurately captured by typical flow modes. These included sea-breeze and land-breeze effects, fall winds and more general thermally induced winds, with the impacts of these more extreme in some areas of the site than others. Due to the complex nature of the wind flow and the site specific meteorological conditions, the analysis was undertaken using an advanced Computational Fluid Dynamics (CFD) flow model resulting in higher confidence in the results and an improved P90 / P50 ratio.
A detailed technical report was delivered to the client within the challenging timelines in the lead up to project financial close. The final reporting provided to the client was utilised within the financing of the projects, with RINA providing reliance for the owner in addition to eight separate international lenders.
Detailed data analysis was required in order to accurately define the localised wind regime at each of the measurement locations. The availability of SoDAR enabled RINA to validate wind shear measurements at the mast locations and provided further support in flow model validations. Wind shear exhibited a strong diurnal variation which strongly correlated with wind speed trends. The use of seasonal, diurnal and sector-wise shear matrices ensured the uncertainty in the derivation of hub height wind speeds was kept to a minimum.