The Worldaware Award for Innovation
This award is given to a company or organization which has developed an innovative idea in, for example, medicine, technology, education or finance, with the proven potential to make a significant contribution to socially, economically or environmentally sustainable development.
The winner: Ove Arup, Zimbabwe
Mike Rainbow and colleagues at the Harare office of the design engineers, Ove Arup, have developed a wind turbine able to rival electricity as a power source for ventilation. The cost of installing the Vertical Axis Wind Turbine Extractor (Vawtex) is similar to that for conventional ventilation. But it is much less noisy, has no fuel cost and causes no pollution. Interest is growing in ventilation without electricity. In some conditions, a building can cool and ventilate itself. Hot air rises in a room and, as it leaves at the top, draws in cool air at the bottom. This effect can be enhanced with a cowl mounted on the building. But even with a cowl it lacks power.
Mike decided that the solution was a wind turbine rotating on a vertical axis and driving a fan. Most wind turbines, for pumping water or generating power, rotate on a horizontal axis like a windmill; but they are usually sited in open country. They cannot easily follow the constantly changing wind directions caused by the buildings in a city. A turbine on a vertical axis, however, can.
In addition, the Vawtex is designed to take advantage of the wind's lift effect which takes an aircraft off the ground. This additional force enables it to rotate three times as fast as if pushed by windspeed alone. Mike Rainbow says it was an exhilarating moment when the prototype spun furiously in a mild breeze. The Vawtex, which is 10 feet tall, will rotate in winds less than 3mph but it is also designed to turn less and less efficiently as the wind becomes dangerously high. Zimbabwe has no tunnel for high-wind testing; so the Arup team tested their turbine by putting it on a lorry and driving it at 75mph down a racetrack.
Mike Rainbow, who transferred to Zimbabwe from Cardiff in 1997 to pursue his interest in sustainable design, says his Harare colleagues with their knowledge of locally available materials made a crucial contribution to the Vawtex's efficient manufacture. It tapped into their ingenuity and resourcefulness, honed by years of hard-currency shortages. A local undergraduate helped as part of his course. The project has sustained jobs in what is currently the fastest shrinking economy in the world.
The first Vawtex was built for a new arts block at Harare International School, from which not only the heat of the day but also that from a kiln room needed to be dispersed. Chambers dug out below the building are filled with granite, and this with the Vawtex makes up a system that takes advantage of Harare's steep fall in temperature at night. Cold night air is drawn through the rock chambers, cooling the granite to below 20 degrees. Next morning, the hot day air drawn over the granite is cooled by up to ten degrees. This cooled air then flows into the lower part of the building at low speed, to avoid churning up the air already present. The Vawtex draws warm, stale air out at the top. Classrooms are eight degrees cooler than they would be otherwise. The system is also used to take the chill off winter mornings. Harare in winter has cold nights, so the granite is allowed to retain the heat collected in the warm afternoon. Chill air passing over it next morning is warmed. The system is constructed in such a way that people can see how it works. Mike Rainbow thinks this will encourage them to use it sensibly. He says his best moment was hearing from initially sceptical people who had changed their minds.
Vawtex turbines have been installed at Africa University on the Mozambique border and at the Mediterranean Shipping Co's Zimbabwean HQ. Eight are being installed at the Centre for Sustainable Construction in Belgium. Arup believes the international market for such devices could easily number thousands per year.
The Vawtex is intended for city use. However, vertical axis turbines can pump water or mill grain in rural areas. One called a Savonius can be built out of oil drums. The Arup team are working on a rural turbine more efficient than the oil-drum design but cheaper and simpler than the Vawtex.
In July 2002 the Vawtex was voted Innovation of the Year at the Building Services Awards in London.
The judges say
The Vawtex offers the prospect of a real breakthrough for environmentally sustainable cooling systems in hot countries. Ove Arup, Zimbabwe, is to be congratulated on a technically feasible solution which not only meets the local constraints but also allows simple, low maintenance, low cost operation. Using the natural power of wind, and constructed from local materials, the system is likely to be particularly attractive for air polluted cities in poorer countries, but also offers export potential to boost the local economy. It is a deserving winner, and we hope the company will be able to promote and market the system effectively throughout the African market, where we feel it has real economic and environmental potential.
Ove Arup, Zimbabwe, P.O.Box 984, Harare, Zimbabwe;
Tel: +263 4 882250; Fax: 882698