The investigations were conducted in July 2006 at Ga-Ramrupu village in Limpopo province. The author collected information regarding this village in the following manner:

1. The author grew up in Ga-Rampuru village and therefore knows the problems and challenges that the villagers face on a day-to-day basis living without electricity. This was an advantage in terms of moving around the village doing the resource assessment analysis.

2. One of the store owners in the village, Mr Morifi was interviewed regarding the issues he faces in supplying power to his store, especially to the refrigerator he has in store. The store owner mentioned that he has to refill the petroleum gas (LPG) in his store every two weeks. He also added that this is very expensive as there are also transport costs involved.

3. Face to face interviews were conducted with some of the villagers where many concerns and challenges were raised. Most of the villagers said that it has been several years since they have been promised to be electrified and nothing has been done to date.

4. The author paid a visit to the Provincial ESKOM office in Pretoria to enquire about any plans to extend the grid to Ga-Rampuru village. The ESKOM Electrification Manager, Jack Bandile was interviewed in this regard.

1.5 Plan of development

The report begins with a brief background of the thesis and introduction of the rural area for which the wind generator will be designed for. Then, the remaining project researches are outlined as follows:

· Chapter 2 reviews the design of a small wind generator and after that a wind generator suitable for Ga-Rampuru village is designed using recyclable materials that where found in this village.

· Chapter 3 details the procedure undertaken to design a permanent magnet synchronous generator for Ga-Rampuru village wind turbine.

· Chapter 4, the generator geometry discussed in chapter 3 is modelled in FEMN using recyclable and commercial magnets to analyse and estimate both machine designs.

· Chapter 5 discusses the results found in chapter 4.

· Chapter 6 details all the steps that were taken in an attempt to assemble a prototype of the wind generator.

· Chapter 7 & 8 concludes the discussion based on the analyses and finally presents recommendations.

Chapter 2. Design of the wind turbine prototype

2.1 Background on wind energy

Wind powered systems have been widely used since the tenth century for water pumping, grinding grain and other low power applications ^[9] . Since then, this has lead to an investigation and attempt to build large wind energy systems to generate electricity.

Wind energy has proven to be cost effective and reliable in the past years. The main development of this technology has been with large wind turbines in the industrialized world, but there is scope to deliver decentralized energy service in the rural areas of developing countries ^[6] .

Furthermore, wind energy is an attractive option to generate electricity since it does not consume fossil fuels nor emit greenhouse gases. The land on which the wind generators are build may also be used for agricultural purposes such as ploughing the land or domestic animal gazing.

During its transition from the earlier day’s wind ‘mills’ to the modern electric generators, the wind energy conversion systems (WECS) have transformed to various sizes, shapes and designs, to suit the applications for which they are intended for ^[5] . In this chapter, the main components of a simple small wind generator will be investigated and a wind generator suitable for Ga-Rampuru village will be designed using recyclable materials found in the area.

The available wind resource is governed by the climatology of the region concerned and has a large variability from one location to the other and also from season to season at any fixed location ^[9] . Hence, it is important that the wind generator is designed for a specific area; this will ensure that the wind energy in that specific area is exploited to generate maximum power from the wind.

2.2 Wind turbine basic principles

The wind generators are specially designed and build to extract power from turning blades with the maximum efficiency and minimum complexity ^[6] . The magnet rotor disk rotates as a result of the force of the wind on the turbine’s blades.

A typical small wind generator consisting of blades, tower, PM generator and the cabling is illustrated in figure 2.1. The main components, which are common to most wind generators, will be discussed below.

Fig 2.1 Basic features of a typical small wind generator ^[6]

2.2.1 The blades

Modern wind turbine rotors usually have two or three wooden blades. A larger number of blades would create more turning force (torque), but would not be capable of driving the PM generator fast enough to generate the required voltage, because the rotor would turn more slowly ^[6] . The rotor blades are designed in such a way that they extract the maximum power from the wind.

Power supplied by the blades to the generator is ^[7] :

(Eq 2.1)

whereis the air density (Kg/m³ ), C is the dimensionless power coefficient and A the area swept by the blades in m³ .

In equation 2.1 above, the power drawn from the wind is proportional to the cube of the wind speed. This means that if the wind speed doubles, there is 8 times as much power available from it ^[7] .

A further important parameter is the tip speed ratio. The tip speed ratio is defined as the ratio of the tip of the blade to that of the undisturbed wind velocity entering the blades ^[11] . The ratio is given by ^[7] :

(Eq 2.2)