Wind towers stage a comeback
A traditional Arabic form of architecture could be a solution to the huge energy usage for air conditioning in hot countries, according to a UK-based design academic. The wind tower – a fixture of Middle Eastern architecture for almost 1,000 years – could provide 21st century sustainable construction solutions, said Ben Hughes, associate professor of building physics at Leeds University.
Previous attempts to utilise the towers in modern buildings have met with extremely limited success across the GCC region – in the main because energy is so cheap.
But as natural resources become an increasing factor in power generation – and a priority for governments – such traditional methods are making a comeback.
The historic Creek area of Dubai has some of the greatest concentrations of the towers in the GCC.
“They used to build the towers as tall as possible, to capture the air at high speed. As it hits the tower, there’s a wall that runs down the center of it that forces the wind down into the building,” said Hughes.
“The higher up you go, the faster the airspeed is.”
The build up of a positive pressure inside the building automatically creates a negative pressure on the outside, which means that stale air inside the building is drawn away.
“It creates a siphon effect,” Hughes explained. “It pushes air into the building and sucks stale and used air out the other side of the wind tower.
“In arid climates such as the Gulf a reduction in air con consumption of around 60% is possible.”
Local architects say that figure could only apply to low-rise structures as in taller buildings too much of the wind would be lost.
The professor said he felt the towers could be easily assimilated into contemporary architectural designs – but tall buildings offer some challenges . “Wind towers can be bespoke manufactured to meet any design requirements, either from traditional materials or sheet metal depending on the aesthetics of the project,” he said.
“Similarly the height of the tower can be adjusted by altering the angle of the air inlet vents to compensate, it follows similar principles of an aircraft where the air pressure is varied by altering the angle of the wing.
“Tall buildings are not necessarily the best use of the system as supplying the lower floors can prove problematic due to the length of ducting required and the need for careful design to include significant buoyancy effect to assist the airflow.”
The towers have been used in recent years although often as part of a mixed ventilation solution rather than just single ventilation system which is stand-alone.
Hughes has studied the current usage. “Masdar has a large wind tower and is the most recent large scale design. However Qatar University incorporated wind towers during it s construction circa 1970.”
Hughes said the heritage aspect of the design is important as well.
“In a period of development it is always important to embed the local tradition and culture to ensure the regional specific identity remains intact,” he said.
“The danger is by employing tried and tested techniques from around the world, the knowledge base of local architects and engineers is lost to ‘new technologies’.
“I based my research approach on that of Hassan Fathy (20th century Egyptian architect who championed Arabic design over imported western ideas) that we should always look at traditional design solutions before looking at new technologies.”
Wind speeds and other climatic data need to be taken into account before the work commences, Hughes said. “Essentially if the area is prone to low wind speeds then the device needs sufficient buoyancy to drive the flow.
An understanding of occupancy patterns and heat gains will provide this information as will historic weather data. Once the design is set the actual construction and installation is straightforward – there are many commercial partners who will undertake both the design and construction.”