This paper reports the design and characterization of a small-scale wind energy portable turbine (SWEPT) targeted to operate below 5m/s wind speed. Aerodynamic performance characteristics of SWEPT were extensively examined using the wind tunnel experimentation and it was found that the maximum coefficient of performance of 14% occurred at the tip speed ratio of 2.9. SWEPT was found to have very low cut-in wind speed of 2.7m/s and it produced 0.83W of electrical power at the rated wind speed of 5m/s. Further, we designed a diffuser structure for SWEPT using Computational Fluid Dynamics (CFD) simulations. It was observed that the SWEPT having diffuser of almost same length as the diameter of SWEPT can produce 1.4 to 1.6 times higher electrical power. An alternative method for the mechanical power calculation is also discussed which does not require torque measurement device and thus is highly useful for common laboratory measurements.