Planning of mobile complete set for a rural wind generator
Planning of mobile
complete set for a rural wind generator
The aim of this thesis is to alleviate the chronic lack of
electricity supply in the rural South African areas by designing a portable
wind generator kit.
An extensive assessment on the rural village of Ga-Rampuru,
in Limpopo Province, was conducted, to investigate the present needs, as well
as the availability of resources both human and material that would be needed
to construct and assemble the system. From the inventory of recyclable
materials found during the investigation the author was more inclined to
suggest the design of a wind turbine that could be assembled and maintained by
the local artisans.
A two pole permanent magnet synchronous generator was
designed using standard commercial magnets, which were later replaced by
recyclable loudspeaker magnets that were found in the village. This was done to
compare the output of the generator in both cases. All the designs were
modelled in FEMM, a software package, to estimate the induced voltage and flux
of the generators.
Using standard commercial magnets the simulated voltage and
flux levels were 9.4, 5.1, 3.6V and 0.0489, 0.0186, 0.0175 Wb, respectively.
Assuming a generator current rating of 1 amp this would yield 36 watts at the
estimated average wind speed of 4 meters per second.
Then when these were substituted with recycled speaker
magnets the generator yielded a voltage of 3.5V and a flux of 0.0171Wb. The
estimated output power of the recycled generator was estimated to be 10.5W.
This compared well with the power output from the commercial magnets
From these preliminary results it is quite apparent that a
viable generator can be designed from the recyclable magnetic components. The
same design procedure as outlined in this thesis can be used to design larger
recycled generators with larger outputs. The design of this wind turbine will
obviously have a wide range of positive developmental benefits on the community
The next stage was practical construction to validate of the
simulation results. This however could not be realised in time.
Chapter 1. Introduction
1.1 The subject of the report
The aim of this thesis is to design a simple wind generator
kit that can be easily assembled and installed by rural artisans. The kit will
use recyclable materials that are found in the rural areas to ensure a cost
effective and environmentally sustainable solution.
1.2 Background to research and investigation of
“Electricity brings immeasurable benefits to human life. With
electricity, comes lighting and the ability to extend the daylight hours, to
study and to improve education. With electricity come cooling and heating and
the ability to store food and cooking. At its extended level, electricity
facilitates communications, transportation and production and paves the way for
the eradication of poverty, industrialisation and ultimately the growth of our
Electricity is a basic necessity and access to it has a wide
range of positive developmental benefits for communities , yet,
in 2001 2.8 million South African households still had no access to electricity
. The majority of these households are poor and live in remote
places which are located far from the central business districts and the
country’s electricity grid. And this makes it very expensive to connect them to
the country’s electricity grid.
As a national initiative to improve the quality of life in
South Africa, National Electrification Programme (NEP) aims to provide
universal access to all South Africans by 2012 . Hence, this has
lead to the investigation of other safe, cost effective and environmentally
friendly alternative methods of electrifying rural areas in South Africa.
Renewable energy resources such as wind and solar, are the
fastest growing alternative means of providing a reasonable amount of energy at
the point of demand. The Government of South Africa is also determined that
renewable resources will be a major complement to the national mix .
1.2.1 Ga-Rampuru, a typical rural South African
Ga-Rampuru is a small village located in Limpopo Province in
South Africa. The village is in a fairly rural mountainous area, which is
situated some 58 odd kilometres from Polokwane, the provincial capital city.
The area has sparsely populated households with some trading stores and
schools. Most of the people in the village are unemployed and rely on
agriculture for their subsistence.
People in the village have to travel long distances to
collect wood or to purchase fuels like liquid petroleum gas (LPG) and kerosene
to meet their cooking, lighting, refrigeration, infotainment and other needs.
Figure 1 illustrates a picture of an LPG refrigerator in one of the trading
store in Ga-Rampuru. This picture and others that will follow in this thesis we
taken by the author during a visit at Ga-Rampuru last June vacation.
The supply of these fuels is both expensive and
unpredictable. Additionally the problems related to the use of fuels such as
kerosene are incidences concerning burned houses and respiratory problem for
children who use kerosene candles for reading is well documented world wide .
The author paid a visit to the Provincial ESKOM office to
enquire about any plans to extend the grid to Ga-Rampuru village; and the
Electrification Manager guaranteed that ESKOM has plans to ultimately electrify
the whole country by 2012. However, further discussions with people from
Ga-Rampuru dismissed the ESKOM Manager’s promises as empty. They contended that
they had heard similar promises but they still lived in darkness.
It was the conclusion of the author that an alternative
solution to the problem had to be devised. Some means of generating electric
power to meet loads such as the refrigerator in figure 1, if only it could be
an affordable design. The best design would clearly be one that uses local
material and human resources.
1.2.2 Resource assessment
The author spent the next three weeks exploring the resources
available in Ga-Rampuru that would support the design and sustainable
construction of electricity generators.
To begin with Ga-Rampuru has two schools, namely Rampuru
primary school and Seokeng secondary school, all which constitute a total
population of roughly 1400 pupils. On average 30% of school leavers will
continue to tertiary education, some will migrate to urban centres in search
for jobs and a substantial number will remain in the village.
This village is endowed with adequate human capacity with
intermediate levels of education. These would constitute a source of trainable
technicians and potential consumers of locally manufactured products. There are
also local mechanics who fix cars and some electrical appliances. These people
will be easily trained as they have hands on experience.
Some of the people who left the village for jobs in the
cities come back to settle down in the village and build big houses like the
one indicated in Fig 2. This clearly indicates that this people can afford the
electricity tariffs if they were to be supplied with power.
Moving further around the village there was evidence of old
windmills used for pumping water. Figure 3 shows one of the windmills. These
windmills operate satisfactorily providing enough water to the villagers. The
presence of these windmills in this area is evidence that there is some wind
resource in the area.
Further investigations took the author to various waste-dump
sites and a range of disused old gadgets that could potentially be re-used, as
shown in appendix A, were discovered. These included cables from an old car,
loudspeaker magnets, drums and old machines that were used for grinding grain.
The other natural resource in the area (of course) is the sun
but from the inventory of recyclable materials found during the investigation
it is more inclined to suggest the design of a wind turbine.
1.3 Objectives of the report
In light of the above background, the main objective of this
thesis is to design a small wind generator for Ga-Rampuru village using
recyclable materials found in this village. The idea is to build an easily
assembled and manufactured machine that can be build by the rural artisans.
This wind generator must of course be cost effective.
The resource assessment of Ga-Rampuru village is conducted in
order to investigate the present needs, as well as the availability of
resources both human and material that would be needed to construct and
assemble the wind turbine using recyclable materials. Furthermore, the resource
assessment analyses lead to an appropriate wind generator design specifically
for Ga-Rampuru village.
1.4 Method of investigation
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
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
· 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 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 .
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 .
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 . 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 . 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 . 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 
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 . 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 :
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 .
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 . The ratio is given by :
where R is the radius of the blades, ωr is the rotor speed in rad/s and W the wind speed (m/s).
rotors operate at low tip speed ratios of 1 or 2, where else, one, two or three
bladed rotors operate at higher tip speeds of 6 to 10. The power coefficient in
equation 2.1 depends on tip speed ratio as shown in figure 2.2. For a
particular wind rotor design there exists a tip speed ratio which will produce
the maximum value of power coefficient .
Fig. 2.2 Power
coefficient Cp versus tip speed ratio 
2.2.2 Permanent magnet generator
Using permanent-magnet generators for small wind turbines is
very commonly used world wide. Usually an AC generator with many poles operates
between 10-100 Hz. Many configurations use surface mounted three phase
permanent magnet synchronous generators with a rectifier connected to the
generator terminals. 
A simple PM generator consists of the stator, magnet rotor
disk and a shaft. The magnet rotor disk is mounted on a bearing hub so that it
can rotate on the shaft due to the rotating blades of the wind generator.
The stator has coils of copper wire wound around them, which
are accommodated in the slots. Electricity is then generated when the magnets
on the rotor disks rotate past the coils embedded in the stator. The magnetic
field that is created induces a voltage in the coils .
2.2.3 Rotor design
There are two types of rotor configurations commonly used
world wide, these are the disk and the cup as shown in figure 2.3 below .
Fig. 2.3 Disk and cup rotor designs
The radius of the rotor primarily depends on the power
expected from the turbine and the strength of the wind regime in which it
The main function of the tower is to raise the blades and the
generator to a height where the wind is stronger and smoother than the ground
level. The wind speed increases with height because of the earth surface .
The tower should be high enough to avoid any obstacles such as trees, building,
etc. Practical considerations such as expense, safety and maintenance limit the
tower to between 10m to 20m  above ground level.
2.3 Design of a wind turbine for Ga-Rampuru
In this section a wind generator that is designed
specifically for Ga-Rampuru village will be discussed. The generator will be
designed using recyclable materials such as car brake plates, cables and drums
found in the village [See appendix A]; this will clearly ensure a cost
effective design. The wind turbine will be designed in such a way that the
local people can easily assemble and manufacture it themselves.
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