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Abstract. The aim of the present study is to investigate the effect of flow parameters on the free convection and mass transfer of an unsteady magnetohydrodynamic flow of an electrically conducting, viscous and incompressible fluid past an infinite vertical porous plate in the presence of variable suction. The thermal radiation and chemical reaction effects are assumed to exist within the channel. Non dimensional partial differential equations of governing equations of flow are solved numerically using Crank Nicolson finite difference method. The skin friction, heat and mass transfer rates as well as the effects of various parameters on velocity, temperature and concentration profiles are analyzed. The signifiant results from this study are that an increase in the values of radiation parameter and chemical reaction parameter causes a reduction in the velocity, temperature and concentration.

The study investigates the interaction of free convective flow with thermal radiation and variable pressure on natural convective heat and mass transfer fluid flow in porous medium. Solutions for time dependent energy, concentration and momentum equations were obtained by the perturbation series method after transforming into ordinary differential equations. The effect of various flow parameters such as: suction/injection ( δ) radiation (R ) magnetic field (M ) heat source (S ) chemical reaction ( Rc) on the skin friction, rate of heat transfer, velocity, temperature, and concentration profile influencing the physical situation were discussed with the aid of line graphs. Keywords: Thermal Radiation, Variable pressure, Perturbation, Natural Convection

Most of the wind energy conversion systems are failing in many developing countries such as Nigeria due to poor and un-appropriate site selection. Ten years (2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010) daily average wind speed data measured at 10m height for Minna (9.6°N, 6.6°E and 251m) were obtained from Nigerian Meteorological Agency (NIMET) and the characteristics of the three small scale wind energy conversion systems with power rating of 1, 1.5 and 3.0 kW obtained from the manufacturers websites were used in this study for the performance evaluation of three selected wind energy conversion system (WECS). The performance of the selected WECS were compared using the capacity factors obtained for the turbines from the algorithms developed, that combine the daily average wind speed and standard deviation for the location with the selected turbines characteristics provided by the manufacturers. The annual energy output for the WECS were found to be 1.37MWh, 1.23MWh and 2.53MWh with corresponding capacity factor of 18.8%, 11.2% and 8.4% respectively from e3001 (1kW), Ge-Power System 1.5SL (1.5kW) and Gv-3kW (3.0 kW). The e30001 (1kW) was observed to performed better with capacity factor of 18.8% as against 11.2% and 8.4% for Ge-Power system 1.5SL (1.5kW) and Gv-3kW (3.0 kW) respectively for Minna location.

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