  
|
 |
| April 2008 |
Feature |
|
The Winds of Change are Blowing around the world from the Windy City
|
||||||||||||||||||||
A kestrel wind turbine in action. |
In the USA, Chicago is known as the windy city - this is however because the area was famous for a specific type of onion which gave flatulence - not the sort of wind one can make electricity from. The city of Port Elizabeth, near the southern tip of Africa on the other hand is called the Windy City because the air hitting this area is almost always moving at great speed after having traveled half way around the world without encountering a single bit of land. It is fitting therefore that the first producer of wind turbines in South Africa, Kestrel Wind Turbines, is located in the Windy City of Africa.
Wind power is an interesting energy. Often it is referred to as an alternative energy source. Port Elizabeth was founded as a port for sail ships which were wind powered. Prior to the arrival of the British, earlier settlers in the area had come from the Netherlands, where the harnessing of wind power to pump water and grind grain in the 11th century had increased the carrying capacity of the low lands to such a level that people could travel from there and colonize other parts of the world a few hundred years later. Later, as alternative energies, such as coal and oil, became cheaper, steam ships took technology to Port Elizabeth that allowed the region to use alternatives to wind, such as coal and oil. The result was that manufacturers such as the booming automotive industries of the area were born allowing people to harness alternative energies to wind.
Getting the wind turbine to a height where air flow is optimal
requires the use of either guyed or scissor towers. In this example, a |
Today, as oil and coal become more expensive again, we approach a time like that when Port Elizabeth was founded, where wind energy looks again to be a useful complementary energy source, together with a variety of other options such as coal, nuclear, solar and tidal energy. Interestingly, much of the technology used in the automotive industry has spin offs which can add value to the wind power industry, hence it is fitting that Kestrel Wind Turbines is based in Port Elizabeth, which is one of Africa's major automotive hubs.
Kestrel Wind Turbines produces four different turbines ranging from the 600W rated e150 to the 3kW rated e380i. The turbines are designed to harvest wind speeds of more than 2 meters per second (7.2km/h) and produce their peak power at 12m/s (42.2km/h). Each unit is designed to have a working life of 20 to 40 years, with very limited maintenance services required every two years.
If one looks at how a wind turbine works, it is important to understand how energy is extracted from wind. The amount of power that can be transferred to a turbine is directly proportional to the density of the air, the sweep of the rotor and the cube of the wind speed. The useable power is determined by the following equation:
In this equation, P is power in watts, α is an efficiency factor, ρ is the density of the air in kilograms per cubic meter, and v is the velocity of the air in meters per second. The efficiency factor is the first important consideration. Albert Betz, a German physicist determined in 1919 that a turbine can at best extract only 59% of the energy in wind passing it, with this now being called the Betz limit. In other words, when investing in wind energy it is best to hedge your bets on those who design the rotors which come closest to the Betz limit.
It is also very important to note that air density is important when working out how much power you can get from wind in your area. The density of air is governed by a number of factors, including temperature, pressure and humidity. High pressure, low temperature and low humidity gives the greatest density. Low pressure, high temperature and high humidity gives the lowest density. Hence, for example, wind power can be more efficient at sea level in a cold dry area, than high up on top of a mountain in the tropics with low atmospheric pressure, high humidity and high temperature.
The South western coastal regions of South Africa generally provide an excellent choice in terms of these factors as the region has moderate humidity, relatively low temperatures, sea level atmospheric pressure and abundant wind from the frontal systems which move up from the Southern Oceans.
Kestrel provides turnkey solutions for rural power generation, and generation for people who wish to have back up power in the event of load shedding, or who are unable to access the grid. When installing a turbine it is important that the turbine be sufficiently high above the ground to avoid the uneven air flows caused objects on the ground. Kestrel Wind Turbines have developed a number of different options ranging from 6 to 18 meter masts which can hoist the turbine into usable air flows. The types of mast range again from the simple scissor mast, which allows the turbine to be lowered and lifted quite easily to guy cable supported masts.
The actual current generated by the turbine is uncontrolled DC current, hence it has to pass to a charge controller. When charging a battery it is important to be able to control the battery at an appropriate rate - too rapidly can cause all sorts of problems - and to also ensure that the battery does not accidentally return current to the turbine, turning it into an expensive propeller. The controller can also detect simple malfunctions.
From the controller the power is then stored in a battery bank to even out the uneven supply of power from the wind turbine. The batteries feed into an inverter which converts direct current into alternating current at the voltage required (e.g. 220V for South Africa, 110V for the USA).
The company has patented the voltage limiters, and the pitch control and more efficient axial flux technology which was developed by Jim Carpy, the original inventor and driving force behind the company which is no owned by Eveready Batteries. The wind turbines were re-named last year, and the names of each unit relate to the rotor diameter eg. e150= 1.5m rotor diameter. The reseach and development team is constantly improving and inventing new ways of making the turbines themselves, with new patents on the blades themselves in progress currently.
Kestrel Wind Turbines have established distributors in South Africa, Namibia, Swaziland, Hong Kong, India, the USA, the UK and France, hence as Africans we can be proud of the extent to which this company is influencing the world. The company has just packed its first serious export consignment to the US consisting of 68 wind turbines. These comprise a mixture of 600, 800 & 1kW wind turbines along with their related controllers. A portion of these units will be used as grid-tie application units, and others will be used for hybrid systems. The value of the order is US$135 000.
With any good idea, the challenge facing the inventor is to turn it into a marketable reality. Jim Carpy has spent thousands of hours since 1999 making wind turbines. To turn his idea however into a marketable, scalable factory, he sold the technologies to Eveready SA - a local battery manufacturer which has been in the battery market for many years.
More information:
Garth
Cambray: meadery@gmail.com
So, who are the team that has been assembled to take Kestrel onto the global
stage? Sharad Saxena as MD has expanded the distribution network globally. Johan
Ferreira has, as manufacturing manager set up the systems to produce the
products, while Gordon Marchard of Nelson Mandela Metropolitan University
Engineering has developed and designed the various towers which get the wind
turbines into decent wind flows. Andrew Swanepoel is the production team leader
involved in the complete production process, while Jason Goedhals is the
resident fibre-glass specialist who designs and over-sees all the fibre glass
components. Emma Sanan heads the Marketing Dept handling all marketing
activities of Kestrel including website re-vamp, market research and product
certification. Stuart Daniels is the National Sales Manager over-seeing domestic
distributors and domestic contracts & enquiries while Tracy Vosloo is the
Admin Co-ordinator in charge of administrative assistance to Management
& overall business activities and Morne Maneveld and Peggy Mistrorigo source
the materials for production.
Copyright Science in Africa, Science magazine for Africa CC. All Rights Reserved
