High resolution non-hydrostatic numerical simulations for wind energy assessment over Libya.

Abstract

This research is aimed at understanding the national wind energy resource of Libya to examine the viability of obtaining wind-generated electricity in the country. High-resolution regional wind observations in Libya are not sufficient for wind resource assessments throughout the country. To overcome such a barrier, the wind conditions have been estimated utilising high-resolution 3-D nested numerical simulations by the Non-hydrostatic Mesoscale Model of the Weather Research and Forecasting system (WRF-NMM). Analysis 2007 data from the Global Forecast System (GFS) were used as initial conditions whereas the boundary conditions came from a combination of GFS analysis and forecast data, in all runs. The coarse domain had a horizontal resolution of 15 km and a temporal resolution of 30 seconds while the fine domain had a horizontal resolution of 5 km and a temporal resolution of 10 seconds. 365 successive nested simulations were performed to produce hourly wind velocity data at 10 m above the ground along with at model sigma levels for both domains for the entire year. A cubic spline interpolation was used to interpolate wind velocity data between sigma levels and 10-m winds. Thus, wind velocity data at each grid point at six fixed heights (25, 50, 75, 100, 125, and 150 m above the ground) were obtained. Hourly power density data were computed at the seven mentioned heights. Wind power outputs were also estimated based on the power curves of commercial wind turbines of different sizes and designs. Results have shown that Libya has a very good potential for wind power generation. Several areas have been identified to be promising for future wind farms. The eastern and western coastlines, the northwestern high-altitude regions, and the mountainous areas in the Sahara Desert, have great potentials of using wind-generated electricity. Summer experiences the highest wind power resource over most parts of Libya. Over most areas, vertical wind shear peaks in the atmospheric layer of 75-100m. The use of the standard value of wind shear exponent would underestimate the vertical wind speed and power changes on most parts of the nation, while it would overestimate them in a few areas.