How our cooling systems work, based on centuries of tradition
By Darío Cadavid
We've needed to keep cool for centuries – both indoors and outdoors – but the ways we've managed to achieve this have changed over the years.
One way of keeping places cool is with natural ventilation. This takes advantage of the differences in air pressure between two specific places, pushing wind from one area to the other to cool it.
An example of natural ventilation traditionally used in Qatar is the so-called "chimney effect", which is caused by the difference in the density between warm air and cold air. To keep a place cool, warm air needs to be able to flow out of an area through cracks and purpose-made openings at high level. This warm air must then be replaced by cooler air from outside, via lower-level openings.
Before air-conditioning was part of all infrastructures in Qatar, traditional architecture evolved in response to the climate and solutions were found to keep houses cool. Materials were carefully selected, specific building techniques were used, and ventilation was provided by creating conditions which encouraged the movement of air.
It is not surprising, then, that souqs in the Middle East were traditionally built with narrow stone corridors and high archways, and cooled by wind towers which would channel sea breezes inside and carry hot air outside. As this cool air entered the narrow corridors it would accelerate, while the high archways would provide enough height to create the chimney effect, and the stone walls would absorb heat from the air during the day and release it at night when ambient temperatures are lower.
Blending traditional concepts and modern technology, we can now control comfort conditions all year round. The challenge which we are now actively working towards is to do so in the most efficient and environmentally-friendly way possible.
Last year at our Brazil 2014 open-air Fan Zone here in Qatar, we used low-velocity displacement type ventilation to recreate a traditional chimney effect. We supplied cold air at floor level, which absorbed heat from the fans and surfaces as it rose, before being released as warm air through the roof, much like it was done traditionally in the past. We supplemented this with a number of cooling columns which used high-velocity ventilation jet nozzles. These columns provided bursts of air to deliver noticeable air movement, and a cold fog system sprayed mist into the Fan Zone which provided additional cooling by evaporation.
During the matches of a FIFA World Cup™, the temperature for fans comfort must remain between 24 and 28 degrees Celsius (measured as standard effective temperature). This takes into account environmental factors such as shade, radiant temperatures, humidity, air speed and wind, and also personal-based factors like clothing and people's individual metabolic rates.
The temperature for players should be 26 degrees Celsius (measured as wet bulb globe temperature). This takes into account factors including the air temperature, solar heat and air movement, among other factors, and is adjusted for outdoor environments. With this in mind, we at the Supreme Committee for Delivery & Legacy are incorporating cooling technologies into the designs of our proposed venues ahead of the 2022 FIFA World Cup Qatar™. This will ensure that football and sports can be played year-round by people in Qatar and countries with similar climates even after the tournament has finished.
Natural ventilation has been incorporated into the designs for our stadiums to recreate a chimney effect through purpose-built openings. The openings are strategically located to facilitate natural cooling whenever the external conditions render air conditioning unnecessary. We use Computational Fluid Dynamics (CFD) to perform tests and predict the movement of air, moisture, wind and temperature within different environments, in a time and cost-effective manner. Our stadium bowl and pitch cooling systems are being designed using a combination of analytical and CFD methods, which use sophisticated software to solve complex equations.
While the latest technology is being applied to our cooled stadiums, the tradition of cooling remains as important to our country and region as it has been for centuries. Just as stadiums are heated in winter in other parts of the world, so we are cooling ours in the summer months to make sure that we leave a lasting legacy of environmentally-friendly cooling technology for future generations to enjoy the benefits of sport throughout the year.