Bahrain World Trade CentreEdit profile
Bahrain World Trade Center Manama, Bahrain The Bahrain World Trade Center is the world’s first building to integrate large-scale wind turbines; and together with numerous energy reducing and recovery systems, this development shows an unequivocal commitment to raising global awareness for sustainable design. This building is pioneering a new direction for designers and owners to consider incorporating innovative renewable energy systems and better energy efficient measures into their developments in order to reduce their carbon emissions. As a technological precedent, the BWTC has shown that commercial developments can be created with a strong environmental agenda and addresses the needs of our future generations. The BWTC encapsulates the essence of a sustainable philosophy engaging all of the social, economic and environmental impacts of the project. As well as making significant strides in environmentally-balanced architecture, the building is now considered a source of national pride for Bahrain residents, and is attributed with generating economic prosperity within the capital of Manama. The inspiration for 42-storey, 240m high, twin towers originated from regional ‘Wind Towers’ and their ability to funnel wind, and the vast ‘sweeping sails’ of the traditional Arabian Dhow as they harness the breeze and amplify its energy, driving it forward. After careful CFD modelling and extensive wind tunnel testing, the towers’ shape was literally ‘carved’ out by the wind to create optimum airflow around the buildings. The elliptical plan forms act as aerofoils, funnelling the onshore breeze between them, creating a negative pressure behind; thus accelerating wind velocity between the two towers. Vertically, the sculpting of the towers is also a function of airflow dynamics. As they taper skywards, the aerofoil sections reduce. This effect, combined with the increasing onshore wind velocity at higher altitudes creates a near equal regime of wind speed on each of the three turbines, irrespective of height, allowing them to rotate at the same speed and generate the same energy levels. Understanding and utilising this phenomenon has been one of the key factors that has allowed the practical integration of wind turbines into a commercial building design. The premium on this project for including the wind turbines was less than 3.5% of project value. Based on the energy savings and the increased value of the building having wind turbines, the payback period is extremely favourable. The initial energy yields during the design phase was approximately 15% therefore 1300MWh per year, however from early commissioning results the turbines are estimated to generate substantially more energy due to the reduced occupancy profile of the building and the wider operational period of the turbines. Other than the wind turbine renewables, the building does include a number of other sustainable active and passive systems to reduce carbon emissions, such as: Buffer spaces between the external environment and air conditioned spaces – examples include a car park deck over and to the south of the mall which reduces solar temperature and conductive solar gain; Significant proportion of projected shading to external glass facades; Balconies on the end elevations with overhangs for shading and doors for fresh air during winter months and breakout areas; High quality solar glazing with low shading coefficient to minimise solar gains; Low leakage to reduce stack effect and windows to allow mixed mode operation in winter months; Enhanced thermal insulation for opaque elements; Dense concrete core and floors within the internal environment to level loads and reduce peak demand on air and chilled water transport systems; Variable volume chilled water pumps that operate at less pump power at part loads not constant volume; Total energy recovery heat wheels at fresh air intake and exhausts to recover `coolth` from the vitiated air and recover it to the fresh incoming air; Energy efficient, high efficacy, high frequency fluorescent lighting with zonal control; Dual drainage systems that segregate foul and waste water to allow grey water recycling; Connection to the district cooling system with sea water cooling; Electronic taps with excess water flow restrictors; Reflection pools at building entrances to provide local evaporative cooling; and Solar powered road and amenity lighting. Each 29m turbine diameter horizontal axis turbine produces 225kW at 12m/s, has a start up speed of 4m/s, shut down speed of 25m/s and weigh 11 tons. The bridges are ovoid in section for aerodynamic purposes and are complex structures because they incorporate maintenance free bearings where they connect to the buildings to allow the towers to move 0.5m relative to each other and without transferring any kinetic energy to either tower. They span 31.7m, weigh 70 tons are and made from steel in Bahrain. They are designed to withstand and absorb wind induced vibration, and vibrations induced by both an operating and ‘standstill’ turbine. Analysis was undertaken to estimate the natural frequency of the bridge and to ensure it does not conflict with the frequency of itself and the building. Further precautions are included in the design to allow the bridge to be dampened by adjusting the tuned mass damper.