By Peter Ventin, P.Eng., CANSULT
INTERNATIONAL: climatic extremes building in the Middle EastEngineering
You can distinctly see waves of heat emanating off the ground under the midday sun. They seem to melt the horizon, obscuring the skyline in every direction. The desert oasis that is the city appears s...
You can distinctly see waves of heat emanating off the ground under the midday sun. They seem to melt the horizon, obscuring the skyline in every direction. The desert oasis that is the city appears scarcely more than a mirage — perhaps appropriately so, since building fully developed, even thriving, cities with sophisticated modern amenities in the Arabian Desert has been no small feat.
Spanning an expanse of desert land, Middle Eastern cities typically have temperatures that range between 40 and 50C. At the same time, those such as Abu Dhabi on the seacoast swelter under a relative humidity of 60%-95% during May to September. It is no wonder that one of the biggest challenges facing consulting engineers and builders in this part of the world is the extreme and sometimes hostile weather.
The atmospheric saline content compounds the difficulties, limiting the engineer’s selection of materials and equipment to those that will hold up with minimal corrosion under these conditions. Meanwhile the climate inside buildings averages the same as in North America, with 23C, with 50%-60% relative humidity. The stark contrast between indoors and out naturally puts an unduly heavy demand on refrigeration and air conditioning equipment, with exceedingly high levels of energy consumption.
Not only are engineers faced with the dilemma of finding the right materials and devising systems to withstand these conditions, but also they must find relatively economic solutions. The West may think of these countries as rich and flowing in oil, but Middle East clients are very cost-conscious.
“Clients and building owners in this part of the world expect their consulting engineer to provide them with good value for their investment,” says Riad Nashif, vice-president and manager in Cansult’s Abu Dhabi branch. “The analysis of capital cost versus operating cost therefore becomes a determining factor in the design process, materials selection process, and the property life cycle.” Capital expenditure is all too often affected by the fluctuating costs of day-to-day operations in countries that rely largely on the import of building materials using foreign currencies. It can sometimes be a constant juggling act to try to achieve a propitious balance between the two.
Few Canadian consulting engineer firms are equipped to effectively manage the heat, but a handful of them continue to survive and even flourish in the face of these challenges. Working with extreme weather conditions is no new challenge to Cansult. Established in 1961, the Canadian, employee-owned firm based north of Toronto has provided engineering and project management services in Africa, South America, Europe, Asia and the Caribbean, and especially in the Middle East.
Eight of its 11 international offices are in the Middle East, with a new office opened in Qatar just this year.
What about the events of 9/11? Has the tragedy had an impact on Cansult’s operations in the Middle East? The long-term impact seems to have been minimal. Cansult’s workload in the region has increased over the past year, and the company has been recruiting heavily throughout the period.
Following are two examples of Cansult projects in Abu Dhabi, capital of the United Arab Emirates on the Arabian Gulf.
Headquarters of the Emirates Center for Strategic Studies and Research, Abu Dhabi
Established in 1996, the Emirates Center for Strategic Studies and Research has a mission to strive for the social and economic betterment of the people of the United Arab Emirates. Cansult is responsible for the design and construction supervision of its new complex. It has six distinct elements, consisting of office and university blocks, a library, cafeteria, sports facility, and a prayer hall. The university block will include a 220-seat auditorium and a ballroom, and the entire complex is being built on a 229 x 225 metre piece of land in the heart of Abu Dhabi. The construction of the first two phases is almost complete.
To combat the heavy demands on the building systems caused by the climatic extremes, a microprocessor-based building management system was introduced that optimizes refrigeration loads based upon both occupancy levels and the varying solar gains during the different times of day and year. The high and low temperature extremes could vary by as much as a factor of five. The programmable controls are set to maintain comfortable conditions efficiently during business hours, but to raise the internal temperature after business hours while maintaining it at a level that preserves the building’s material finishes and contents.
The variable air volume dampers, or VAVs, also respond to the varying daily solar exposure and occupancy levels by providing for optimum space block refrigeration loads. The complex has a chilled water system designed on a “reverse return” principle using variable-speed chilled water pumps. The components modulate in response to space heat loads sensed by VAV controllers.
Many fine details flow together to make the complex a haven from the harsh weather. For instance, the ventilation system of each building has been designed to maintain a constant positive pressure to reduce the saline content in the atmosphere and combat the high relative humidity outdoors.
The chiller condenser fins are factory coated with anti-corrosion film. As well, air-handling units for treated fresh air have bag filters and sand trap louvers to minimize the transfer of fine dust and sand particles in the air. Pre-treated reheat coils are provided in the library where a close control of humidity and a higher rate of air circulation are essential. The circulating chilled water is treated against scale and corrosion, as well as bacterial and algae growth, by means of automatic chemical dosing. Other precautions consist of insulating service networks such as the water supply and drainage systems to prevent condensation at the saturation point.
The materials and design of the building exterior fabric mitigate the effects of solar gain. The components include:
Double glazed units of carefully selected thermal characteristics which provide an efficient temperature gradient between outdoors and indoors and also help to avoid condensation on the exterior glass panes. They include special glass coatings with a shading co-efficient of 0.22 and a U-value of 4.98, and glass panes 6 mm thick with 12 mm air spaces in between.
Triple glazed units for the roof skylight.
Double (sandwich) exterior solid concrete block walls with rock wool thermal insulation. The thermal insulation and the air space between the two walls act as the vapour barrier, an important consideration given the high levels of humidity outdoors.
Abu Dhabi Trade Center
Another example of the ingenuity needed to design buildings in hot weather extremes is the Abu Dhabi Trade Center, currently under construction.
This downtown redevelopment project includes two 14-storey office towers, a 13-storey fully serviced apartment tower, a shopping centre consisting of 300 retail units, restaurants, cineplex, family entertainment area, ballroom, car parking facility and a 13-storey extension to the existing Beach Hotel. The complex is situated on a premium site overlooking the sea in this bustling capital city, adding to a skyline that today rivals those of major cities around the world.
Cansult is acting on behalf of His Excellency, Sheikh Suroor bin Mohammed Al Nahyan to oversee the completion of the U.S. $300+ million complex. The client retained Cansult for the pre-contract development stages, as well as to provide ongoing project management, design review and construction supervision services. Cansult’s multi-disciplinary team has 26 full-time staff consisting of architects, civil, mechanical, and electrical engineers.
As an illustration of the sheer size and scale of this project, here are examples of the amount of materials and equipment from different parts of the world consumed within phase one:
Stainless steel handrail3,000 metres
of cooling (U.S.) 4,800 tons
Length of chiller pipework7,000 metres
Power capacity (Germany)42 MW
Total volume of concrete160,000 cubic metres
Days worked on site760
The floor area of the immense development is approximately 285,000 m2, all with artificial lighting. At the same time there are large areas of glazing to allow maximum daylight, which entails large solar heat gains. The conduction gains are particularly high due to the outside temperatures.
The various uses involve high occupancy levels — the ballroom alone holds 2,000 people — requiring high volumes of supply fresh air that needs to be cooled. The building also needs to be positively pressurized to prevent the ingress of hot humid ambient air that could cause condensation damage to the finishes and equipment. There are also high heat gains from the mechanical plant, electrical switchgear, kitchen, and laundry equipment.
The combination of these factors equates to a massive cooling load for the air conditioning system to overcome. The required cooling load for the development is 34 MW.
The most important element in designing an air-conditioning system of this size is the concept for the chilled water system and the selection of the central refrigeration plant. The client required a centralized plant to serve air conditioning to the whole development. We needed large capacity chillers but standard equipment of this size is not available. Cansult worked with the contractor and the chiller manufacturer to find equipment that could deliver the high cooling capacity and work in the high ambient conditions. The condensing temperature needs to be above the ambient temperature, which in the summer in Abu Dhabi is 46C.
After extensive design development we selected water-cooled centrifugal chillers. In all, there are seven chillers, six on duty and one standby, generating an installed total cooling load of 39 MW (11,200 tonnes). To reject the heat from the condensers there is a condenser water system connected to external dry air coolers.
The chilled water system was designed as a “plant building loop” or “primary-secondary circuit” system. It consists of two main piping circuits, a primary, and a secondary circuit. The primary circuit serves the chillers with water circulated by constant flow pumps. The pumps are sequenced such that the number of pumps in operation matches the required number of chillers in operation. There are eight secondary circuits serving the various areas of the building. Each secondary circuit includes a variable speed pump that adjusts the chilled water flow in the circuit to suit the air-conditioning load. Flow meters and temperature sensors calculate the energy requirement in the circuit and they are connected to the facilities management system, which sequences the chillers to match the load. BACnet is the network protocol used.
The dry air coolers are located externally, on the beachfront, meaning that the equipment needs to survive the high ambient temperatures and humidity, and the high saline content of the air and sand blown by the sea breezes. The heat exchanger bundle was coated with two coats of rust resistant paint, the fan blades were polyester coated, and the frame was hot dipped galvanized.
The amount of rejected heat from these chillers is vast, but in the desert environment there is little need to recover it for heating the building. The client required that the heat be recovered in some form, however, so a dedicated pumped distribution circuit connected to the condenser water circuit was incorporated into the design. It supplies condenser water to high efficiency plate heat exchangers that heat the domestic hot water and the swimming pool water. The hotel, service apartments, and kitchens require large quantities of domestic hot water, which otherwise would be heated by electricity.
Another design consideration for domestic water systems in this environment is the incoming water temperature. The mains water can reach 36C in summer. For cooking and personal washing this is too hot, and especially undesirable for a five-star hotel. A “chilled” cold water system was therefore included to reduce the mains water temperature to acceptable levels. It has high efficiency plate heat exchangers supplied with chilled water from the air conditioning system.
An advanced facilities management system controls all HVAC equipment, controls and monitors the plumbing equipment and controls all the variable air volume boxes and fan coil units in the complex from a central workstation. The system has thousands of data points connected to the central workstation, which not only ensures that the system runs at maximum efficiency, but also that maintenance staff have information to pinpoint any faults.
Peter Ventin is resident manager for Cansult’s office in Qatar.
Politics of doing business in the Middle East
Following the tragic events of September 11, 2001, the Middle East has received significant attention — not always of the favourable variety. The media exposure has, however, served to educate individuals the world over about the diverse nature of “the Middle East.”
Cultural and religious beliefs vary significantly across the region, as does the state of development. Yemen, Iran, and Iraq are on the road to development, while the United Arab Emirates and Qatar boast buildings and facilities that are truly world class. The opportunities that exist in some of these affluent countries continue to attract the interest of Canadian engineering firms.
Doing business in the region requires a focused approach that considers the regional, social, religious and moral attributes specific to each country. The region cannot be considered a homogeneous whole that can be approached using a common model. Throughout Cansult’s 35 years of continuous operation in the region, we have developed an understanding of the key elements of operating there successfully.
The following table provides an overview of similarities and differences of doing business in the Middle East.
Key similarities with Canada
Importance of personal relationships
Similar levels of technology
Key differences with Canada
Young and sometimes unreliable legal system for commercial disputes
System of commissions and sponsors
Labour workforce primarily imported
Women’s issues are different
Time is valued in a different way
Significance of trust and relationships in working arrangements
Difficulties in communication between different cultures
Different system and length of working hours (two distinct shifts and late afternoon hours)
Procedures for work permits and entry clearance