My first impression is that 4.5m diameter is too big for a suburban environment, especially with Cape Town winds. I would say about 2m diameter is a good size.
There are two approaches to installing turbine.
The fully legal: For this you have detailed drawings done of the planned installation, and get a structural engineer to sign it off. Then you approach your council, and see what they say. Bear in mind its much easier for a lazy civil servant to say 'No', than to engage and finally approve. They might ask you to do an EIA (Environmental Impact Assessment), which is a very tedious process. Thats what happended to a friend of mine in Milnerton. The good side of that, is that anyone in the same area can refer to that EIA (which was passed), and I have heard that council (which covers Milnerton) does not now object to domestic wind turbines, up to 9m in height.
The other approach is more Zen, 'just do it'. This has a few advantages: It less hassle, delay, paperwork and expense. Also, the more people who go this route, the more of a precedent is set, and the more likely future applications for approval will be approved. Of course there is the risk that some obnoxious soul lodges a complaint, and that the council instructs you to take it down.
If so, that would be a wonderful story for all the papers, and you will become famous: "Local householder tries to help planet; council objects". With the ReFIT for microscale generation planned to come in soon, any council which objects to local generation is on a collision course with City and National policy.
Also remember that its much easier for a lazy civil servant to do nothing, than to notice a turbine and lodge an objection.
There are a few things to bear in mind whichever route you go:
- Avoid hanging over the boundary line. If your pole is in the centre of your property, its likely to be less noticable, and won't "loom" over your neighbours.
-Think about where the shadow will fall in all seasons. Even the most reasonable neighbour will object if there is a flickering shadow on their bedroom curtains every morning at dawn!
-Two bladed designs tend to spin faster, and so can be noisier. Although a three blader can be very quiet, in general the more blades a turbine has, the slower it is designed to spin, and the quieter it will be.
I hope that's helpful for you!