Since our wind turbine was designed with a wind tunnel test in mind, a wind deflector was made. The blades are designed (curved) so that the fan will have more force pushing on one side than the other, which spins the fan. A deflector would decrease the opposing force and so increase the speed at which the fan will spin.
This may not be suitable for your application as the natural wind direction cannot be guaranteed and so the deflector may be ineffective.
A 1mm thick aluminium sheet was cut with a guillotine to a height of 260mm. Tin snips were used to cut out the folds and triangle sections and a sheet bender used to bend these parts to 90 degrees. The sheet was curved by hand to match the outside radius of the fan base.
Holes of 4mm were punched into the folds for the screws (same as for the blades) to go through. The base was hand drilled for the screws, which were tightened using an allen key.