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Thu 12 Aug 2010 04:00 AM

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The return of wind towers

The answer to energy-free air-con is literally blowing in the wind, says Dr Ben Richards Hughes of Heriot-Watt University, Dubai Campus.

The return of wind towers

The way in which we use energy in construction has a direct impact on global warming through carbon dioxide emissions. Designers, engineers and architects are under increasing pressure to build sustainable structures. However, we often overlook successful methods used in the past in pursuit of future technologies.

"Before inventing or proposing new mechanical solutions, traditional solutions in vernacular architecture should be evaluated and then adopted or modified and developed to make them compatible with modern requirements," Haasan Fathy.

Buildings account for up to 40% of the world's energy use. Breaking that figure down further, 60% of the total energy consumption of buildings is in the HVAC sector. In the UAE, the air-conditioning units in commercial and domestic dwellings are a major contributor to the total carbon dioxide emissions. However, this was not always the case.

Middle Eastern architecture has matured over time, shaped by the hot acrid climate. The Malgalf or wind tower adorned traditional buildings. These were used to trap cooler air at a high level to deliver to the occupants at a low level, often through water reservoirs so as to regulate humidity. This method offered comfortable indoor conditions at zero cost to the environment and the user. With the advancement of construction techniques and technologies, these systems have been phased out in favour of mechanical systems consuming large amounts of energy.

However, this traditional technique has been developed and applied to modern equivalents, with considerable success in Europe, where the climate is less susceptible to large temperature variations. The wind vents are designed to suit the aesthetics of the building, but function in the same way, trapping air at high level and delivering to the occupants below. The wind vent contains an internal structure that divides the duct into quadrants, thus providing a delivery flow irrespective of wind direction. The remaining quadrants are used as exhaust chambers for stale or used air.

The patented technology uses solar-driven internal fans to ensure a consistent stream of ventilated air, and therefore energy consumption is nil. Air is captured at high level and channelled down into the building below through existing ductwork and ventilation delivery points; hence retrofitting to existing structures is an option. The device is low-cost, and the simplicity of the system ensures minimum maintenance.

Adapting this technology to the climatic challenges of the UAE offers a significant opportunity for energy reduction, and to an overall reduction in carbon dioxide emissions for the region. Preliminary investigations utilising Computational Fluid Dynamics (CFD) simulation models of the technology in the UAE climate have been carried out by Heriot-Watt University, Dubai Campus. The studies have demonstrated the potential for modern wind towers to be implemented into both residential dwellings and commercial structures. Following the success of this study, full-scale field testing is now expected to commence in the latter half of the year.

Adapting this existing European system to meet the occupancy comfort demands here in the UAE requires the integration of a cooling system. Providing cooling without using mechanical methods or energy consuming techniques is a complex task. However, a year-long study into energy-free cooling devices has yielded several alternatives which may offer the equivalent of energy free air-conditioning to new build and pre-existing structures.

The benefits of the system are not only in energy consumption and carbon dioxide reduction. The use of natural air for ventilating occupied spaces provides the opportunity to reduce or eliminate the health-related complaints encountered by HVAC users. Numerous studies in Europe and worldwide have lauded the health benefits of natural ventilation over mechanical methods. Thus the system may offer cleaner and healthier environment for UAE citizens.

These developments may lead to the first genuinely energy-free air-conditioning, which means exciting times for the UAE. Thus it could be that the next step in zero carbon construction is already here, and always has been...

Dr Ben Richard Hughes is the Research Project Outreach Co-Ordinator for Heriot-Watt University, Dubai Campus. He has spent 16 years as a mechanical engineer, from apprentice to doctorate, and in 2009 was elected as a Sir Joseph Whitworth Scholar in recognition of this achievement.

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