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Bahrain's first truly intelligent sky scraper - the Bahrain World Trade Centre (BWTC) two sail liked structure's standing at 240 m in height with 50 floors connected by three bridges on which three 29m-diameter turbine blades are mounted on. The objective of Ace Ltd is to design and build a structure which stands out in its environment and transcends to be a iconic landmark which can be recognised worldwide, while making Bahrain Trade centre a sustainably intelligent building by reducing the demand on fossil fuel energy reserves and cutting down on carbon emissions by 50% by using innovative designs and construction methods.
A multidisciplinary design team will be responsible for developing building's functional and operational purpose and ensure the building meets the criteria of being sustainable and economically viable. Numerous sustainable elements are integrated to the design during the design and planning stages; these include wind turbines on Bahrain's iconic landmark making it the first in the world to be integrated on such a scale, energy and water conservation, Wastewater treatment, improved indoor environmental quality. Life cycle analysis will be undertaken to select the materials that has the least impact on the environment for construction phase. Materials that have adverse effect on the environment will be avoided and be substituted with sustainable alternatives. During the construction stage contractors, designers and architects will work together and develop guidelines for the construction process. This will ensure the whole team understands and embraces the idea of delivering an environmentally sustainable sky scraper.
Table of ContentExecutive Summary 2
1.0 Background 4
2.0 Introduction 4
3.0 Objective 4
4.0 Planning and Design Stage 5
4.1 Wind Turbines 5
4.2 Solar Gain Reduction 6
4.3 Daylighting 6
4.4 Energy and Water Conservation 7
4.5 Wastewater Treatment 8
4.6 Ventilation Control System 9
5.0 Construction Phase 9
6.0 Conclusion 11
7.0 References 12
The Bahrain World Trade Centre will form the focal point of a master plan to rejuvenate an existing hotel and shopping mall on a prestigious site overlooking the Arabian Gulf in the downtown central business district of Manama, Bahrain. The two 50 storey sail shaped office towers taper to a height of 240m and support three 29m diameter horizontal-axis wind turbines. The towers are harmoniously integrated on top of a three story sculpted podium and basement which accommodate a new shopping centre, restaurants, business centres and car parking.(Shaun killa, 2008)
A steady increase in the urban population and aggressive infrastructure development will call for extensive implementation of sustainability. There is an ever growing demand for better sustainable infrastructure that has minimal impact on the environment during the structure's lifespan. Ace Ltd is commitment towards sustainable development by striving for environment friendly designs and construction process and these ideas are at the forefront of our company values. Ace Ltd has the necessary expertise and experience to provide sustainable solutions for the future, due to the fact that Ace Ltd is aware of public safety and welfare and embrace the principal of sustainable development.
Green buildingÂ is the approach of building structures that have very little impact on the environment and economical use of resources during a building's life span. This approach is incorporate during conceptual planning and feasibility studies, design and engineering, procurement and construction, operation, maintenance and renovation phases. Ace Ltd is committed towards developing new technologies and techniques to complement traditional methods in constructing greener structures.
The objective of Ace Ltd is to design and build a structure which stands out in its environment and become's an iconic landmark which can be recognised worldwide. Ace Ltd is highly motivated in making Bahrain Trade centre a sustainably intelligent building by reducing the demand on fossil fuel energy reserves and cutting down on carbon emissions by 50% by using innovative designs and construction methods. Innovations like a 3 wind turbine to be integrated to the skyscraper super structure making it the first of its kind in the world. This project is intended to be a paradigm and example to demonstrate that a structure of this size and magnitude can be environmentally friendly and sustainable while at the same time being economically viable and practical.
4.0 Planning and Design Stage
A multidisciplinary design team will be responsible for developing building's functional and operational purpose and ensure the building meets the criteria of being sustainable and economically viable. Ace Ltd prefers to use this team approach over individuals working in isolation in their own area of expertise. Such an integrated approach during the design phase allows all the members of the design team to experience the inter-related impacts of materials and designs, on the environment. The team would include Engineers, Architects, aero-dynamic and wind tunnel specialist, Interior designers, energy and water conservation management groups, waste water management experts and Environmentalist. Such a multidisciplinary team can share their skills from their area of expertise and will strive towards a common goal of achieving a sustainable building.
Numerous sustainable elements are integrated to the design during the planning stages, these include: Energy and water efficiency, minimal use of resources through new and innovative designs, using renewable and biodegradable materials wherever it is feasible and finally the centre piece of Bahrain Trade Centre the three wind Turbines.
4.1 Wind Turbines
Figure 1: Bahrain WTC 3 wind Turbines (Climate and Fuel, 2010)
The three wind turbines each 29 m in diameter will be capable of producing approximately 1,100MWh to 1,300MWh cumulatively. The wind turbines will operates at full capacity 50% of the time accounting for 11% to 15% of trade centre's annual electricity consumption. The wind turbines will be placed on bridges connecting the two towers at heights of 60, 98, and 136 meters.Â The towers will be shaped like a sail this profile acts as an airfoil, channelling the wind between the two towers as well as generating a negative pressure behind, thus propelling the wind velocity to higher speeds between them. The towers were designed to taper towards the top which leads to the reduction in airfoil cross-section at the top. Such reduction in airfoil section along with increasing wind speeds at higher heights creates a uniform wind flow for each of the three turbines. The shape and profile of the two towers creates "S" flow allowing the wind stream to remain perpendicular to the blades allowing the turbine to operate at maximum efficiency. Understanding and exploiting the full potential of wind energy in a sky scraper required lot of testing and fine tuning in the wind tunnels.
"The combined energy of 1300 MWh/ year is equivalent to carbon emission to an average of 2900KgC (oil burning station) or 2000KgC (gas burning power station). Turbine 1 (60m above ground level) produces between 340 to 400MWh/year, Turbine 2 (98m above ground level) produces between 360 to 430MWh/year and Turbine 3 (136m above ground level) produces between 400 to 470MWh/year." (Shaun & Richard, 2008)
4.2 Solar Gain Reduction
Bahrain has an arid desert climate; temperatures are high year round so reducing solar gain is vitally important. Adequate space has been left between the air conditioned and external spaces in the design. These empty spaces are utilised by having plants and vegetation such as a garden. Opaque materials will be used where possible to improve thermal insulation. High quality double glassed glass will be used to reflect back much of the sun's heatÂ Â reducing heat transfer through the glass. Solar control films were installed on the windows, these films can lessen heat gain up to 80%. These control films reflects thermal radiation reducing the interior temperature significantly. During winter season the films trap the heat escaping from the building, therefore leading to considerably reduction in energy consumption for air conditioning and heating systems. The Bahrain Trade Centre has a connection to the district cooling system where sea water is drawn from a central source and circulated around the building to dissipate the heat this system is economically and environmentally efficient as the source is centralised rather than having a local system for each building contributing to low-carbon emissions. There are also water pools around the building to provide localised evaporative cooling.
Daylighting is the process of utilising natural light and distributing it in a way the light illuminates the building better than artificial lighting. Daylighting significantly reduces energy consumption and operating costs. Energy used for lighting in buildings can account for 40 to 50 percent of total energy consumption. In addition, the added space-cooling loads that result from waste heat generated by lights can amount to three to five percent of total energy use. Properly designed and implemented daylighting strategies can save 50 to 80 percent of lighting energy. (Abraham, 1999)
The Bahrain trade centre is incorporated with ample aperture's allowing enough natural light to illuminate the interior space. Numerous skylight windows will be dotted around the building to practice daylighting. The skylights will be placed at higher location in interior rooms to avoid direct sunlight. Plants will be used to filter the direct sunlight and distribute the intensity. Use materials that reflect more light in the interior. The whole building envelop is designed to admit daylight in and most of the aperture in the envelope is placed on north and south of the building to avoid direct sunlight.
4.4 Energy and Water Conservation
Improved energy efficiency can be achieved by effective lighting controls. Motion sensors will be installed in common public spaces throughout the whole building these sensors will switch on the lights at the presence of occupants and switch off when no occupants are detected. Such a system can save up to 30% of Bahrain Trade Centre's energy consumption. While common spaces are installed with motion sensors the office and shops needed much more of a sophisticated system. Ace Ltd has come up with an innovative solution of using photo cell detectors; these controls constantly stabilise the illumination levels of the interior space and dim the artificial lighting according to the illumination levels of the reflected day light on the inside. Compact Fluorescent lights and Light Emitting Diodes bulbs will be used for artificial lighting as they are highly energy efficient. These bulbs are long lasting, durable, cool (does not increasing the room temperature), mercury free, cost effective and overall more efficient.
Active solar heater system will be installed to provide an alternate source of hot water. These systems consist of pumps to circulate water between the integrated collector storages (batch heaters) and the storage tanks. An electronic controller will operate the pump i.e. switch on the pumps when the water in the collectors is warm enough thereby distributing and replacing the hot water from the collectors. One of these Collector's can save as much as 7KW.h/day, with 10 hours of sunshine it can save up to 70KW.h/day and the pumps to operate this system take less than 100 W per day (about 1% of the total energy conserved) making this system almost leaving zero operational carbon footprint.
Figure 2: Active Solar System (US Department of Energy, 2007)
Water conservation was identified as key elements in making the Trade centre sustainable as water is very scarce in these parts. The Trade centre will be fitted with an extensive rainwater harvesting system to fully utilise any water that falls during rainfall. Rainwater harvesting system will mainly consist of three elements: accumulation, conveyance and storage. Water is collected from roofs and grounds through a network of pipes and gutters. This network connects to an underground filtering and treatment plant for cleansing. This non potable water can be used for gardening, flushing of toilets or can be used in the pools around the building. The rain harvesting system not only conserves water but it also prevents stromwater runoff. Fitting water conserving devices will largely reduce water demand on site; such fitting would include sensor taps, Vacuum toilets, spray taps with steady flow, flush free urinal and low flow shower heads. These water conserving devices reduce the demand for water along while reducing the waste water production.
4.5 Wastewater Treatment
There are two types of waste water generated from domestic use greywater and sewage or black water. GreywaterÂ isÂ wastewaterÂ produced from activities such as laundry, dishwashing, and bathing while sewage or blackwater includes human waste. Greywater constitutes the majority of wastewater up to 60% to 70%. Due to the lower level of contamination in graywater compared to blackwater it can be treated fairly easily onsite, for this purpose the Trade Centre will consist of two sanitary plumbing lines: one for graywater and the other for blackwater. While sewage or blackwater is discharged into the public sanitary sewer system Greywater will be captured, treated using the onsite underground treatment plant. This treatment plant will consist of several filtration process and UV treatment to kill of the bacteria. The recycled water will be distributed back to the building to be used as non-potable water i.e. flushing.
Figure 3: Grey water treatment plant (Zer0-M, 2008)
4.6 Ventilation Control System
To provide high quality indoor environment ventilation control systems are installed. Ventilation control system ensures air circulation in the building, ensuring fresh air to the occupants. This system will be controlled by controlled withÂ Carbon Dioxide monitors; air flow is increased in case of exceeding carbon monoxide levels. Filters are fitted to the ventilation system ensuring most of the particles are filtered before entering the building. This system ensures an dust free internal environment along with clean air.
5.0 Construction Phase
During the construction phase the Ace Ltd contractor's take over the project and plays a vital part in fulfilling all the design needs to make the Bahrain Trade Centre a green sky scraper. However, the design team would be involved and will be working in close relation with the contractors making sure there the designs are carried out as conceived and solve any issues with the design during the construction stage.
Building Materials for the construction of the Trade Centre will be chosen by following life cycle assessment standards. The reason for following the standards is to choose a material's social and environmental impact. (Wikipedia, 2010).
Figure 4: Life cycle assessment (WRT Associates, 2010)
The following materials will be used to ensure reduction of any adverse impact on the environment associated with constructing the Bahrain Trade Centre:
Fly-ash concrete will be used instead of Portland cement, fly ash is a char remain from burning of coal. By substituting Portland cement with fly ash we are not only reducing carbon emissions but also producing superior concrete.
Recycled aggregates will be used in the production of concrete for example crushed bricks, concrete and glass can be used as aggregates. For lightweight aggregates volcanic pumice rocks can be used as an alternative. Lightweight aggregates will be used in the top part of the towers to reduce the load on the structure.
Steel rebar will be coated with epoxy resin to stop corrosion occurring this can significantly reduce repair and maintenance costs.
Harmful acid wastes that are environmentally detrimental is negated by avoiding the use of Metal platting instead an alternative "powered coated" metal will be used.
Wooden pulp, cork, recycled paper and cotton will be used for insulation.
Recyclable Gypsum will be used for interior panelling.
Bio- degradable paint and water borne paints will be used. Water borne and bio degreadble paints are much more environment friendly compared to Convectional paint contains paint thinner which is highly toxic and detrimental to the environment.
The construction process can have a significant impact on environmental resources. Environmentally conscious construction practices can markedly reduce site disturbance, the quantity of waste sent to landfills, and the use of natural resources during construction. It can also minimize the prospect of adverse indoor air quality in the finished building. In addition to yielding environmental benefits, all of these actions can lower project costs. (Gerard, 1999)
The following construction methodology will be followed to ensure reduction of any adverse impact on the environment associated with constructing the Bahrain Trade Centre:
During the construction stage contractors, designers and architects will work together and develop guidelines for the construction process. The design team will ensure the contractor understands and embrace the idea of delivering an environmentally sustainable sky scraper
The construction process will ensure to minimize or eradicate any major site disturbances caused during construction. The prestigious site's natural and cultural characteristics will be well preserved through good construction management.
Since 80% of construction waste is recyclable waste material from construction is sorted and recycled and used on site for some other purpose. Plastic waste will be sent to the local recycling facility. The recycled material can be used to make insulation for the building.
To prevent pollution and dumping of silt and chemicals into the local drainage system the contractors will build silt fences, trenches, earthen dikes, sediment traps and basins.
Excavated soil will be reused as compost vegetation and plants around the site.
Construction workers will be encouraged to travel via the shuttle bus provided by Ace Ltd instead of driving to work.
Using environment friendly equipment during construction stages. Will be using low emission vehicles to reduce air quality impacts. Equipments using bio diesel and diesel-electric hybrid build will be preferred.
There is an ever growing demand for better sustainable infrastructure that has minimal impact on the environment during the structure's lifespan. I believe in this project Ace Ltd has achieved a environmentally sustainable building with innovative concepts and designs along with environment friendly construction process to truly create an "greenscraper". The Bahrain World Trade Centre is destined to achieve the LEED (Leadership in Energy & Environmental Design) certification for its design and construction management strategies which include energy and water conservation, Wastewater treatment, improved indoor environmental quality, pioneering wind turbines on sky scrapers, and stewardship of resources and sensitivity to their impacts.
I hope this project showed rest of Middle East and Asia that a structure of this size and magnitude can be environmentally friendly and sustainable while at the same time being economically viable and practical. I also think green sky scrapers is the way to go in the future as they have very little detrimental impact on the environment and leave a minimal carbon foot print, which is highly imperative considering our battle with global warming.