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Masdar:A carbon-neutral city

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Masdar City is a project in the United Arab Emirates which is being built by the Abu Dhabi Future Energy Company, a subsidiary of  Mubadala Development Company. Pratik Raval, Project Leader at Transsolar Climate Engineering, New York explains the role of climate engineering in designing master plan for the world’s first carbon-neutral city.

Masdar city master plan has been developed with the most holistic approach towards defining sustainable urban development: The six square kilometer city, designed by Foster and Partner is eventually to house 50,000 people and will include specific targets of zero carbon and zero waste, sustainable transport, materials, food, water and habitats and balanced wildlife, culture and heritage.

The sustainable approach

The urban density is one of the most important measures of a sustainable approach. It has the greatest impact reducing the energy demands in this hot and humid climate. All energy consumption must come from renewable sources and materials have to be recycled. Due to the limited capacities of renewable energies, like sun, wind and geothermal, the first essential step is to minimize the demands. The local natural adaptations showed us the way to reduce energy and material consumption.

The first step was to analyze the environment and setting of the buildings. A close look is taken at all existing weather data, which need to be compared before use. An environmental data measurement station was set up on the site to collect more data for verification. Also the proximity to the airport called for quantifying noise and other pollution to be taken into account for protection measures. The second step included study of the cultural background, reflecting solutions of city planning and building designs. The closest relating cities with a historical cityscape were Dubai and Muscat built in a similar climate. They showed certain patterns like buildings separated by small streets (almost pathways) and shaded courtyards that helped minimize solar gains in the streets. Thirdly, by reviewing natural adaptations of flora and fauna in UAE, strategies of solar and sand dust protection for water collection from dew and minimized water consumption for body waste disposals were identified. It was important to study the historical height layering of plant growth in an oasis with mint growing below bushes and fruit trees that are shaded by date palms. The adaptation of the local mangroves to the increasing salinity of the Arabian Gulf was also analysed.

A sustainable approach cannot be solved only by technical solutions. It also demands rethinking lifestyles with respect to mobility, water, energy and waste production. Some of the key concepts of Masdar City are very innovative and have never been built in such a large scale.”
– Pratik Raval

From Macro to Micro

Sunlight and air are the most important natural resources for a city. Considering the local climate conditions with high outdoor temperatures and humidity levels in summer and zenith sun positions it required specific guidelines. Using air flow evaluations by computational fluid dynamic CFD simulations and fluent and daylight and shading analysis using backward ray tracing method by Radiance, the generic models were analyzed to direct the city design.

A similar approach was used for calculation of dynamic building loads, based on assumed construction types, external and internal gains and occupancies. Based on the final proposed exemplary building typologies the load calculations were updated to meet the possible energy production on site.

The CO2 neutral approach for Masdar development included banning cars with combustion engines from the inner city. This reduced the demand for ventilation in the city to simply providing fresh air and cool breezes. Starting with an isothermal air flow analysis to research the impact of air infiltration from the wind flow above the city into the street canyons, the model allowed to determine preferred street widths, length and piazza locations. To determine the micro climate above the city due to the high solar absorption of the photovoltaic roofs, a simplified calculation model of the whole street was defined. It was evaluated with and without wind in respect to the local temperature increases above the city.

In the Masdar development, streets are mainly used for circulation, fresh air distribution and micro climate protection. Two green park bands through the whole city are oriented towards the sea breeze and the cool night winds. They create the necessary fresh air corridors through the large city grid. The sizing of facade openings too was adjusted as per the high level of direct radiation on the project site. Using the generic building model and evaluations, the project team decided to illuminate the buildings through the courtyards and not via openings to the streets. Therefore the streets can be narrow and a better thermal comfort can more easily be achieved. The courtyard design differs depending on the type of building usage. All courtyards need either a retractable shading – to protect this microclimate from high temperatures – or at least an external shading of each facade opening. Facade ratios have been determined for the different floor levels based on the final typology design.

Reducing Building Loads

The city design determines the city climate and city heat or cold island effect, which are important boundary conditions for the building loads. These depend on the building design and construction, the external loads and the internal loads which are determined by the use. Using the simulation package TRNSYS and the generic building model annual hourly loads for air conditioning and electrical demands were identified. The results of the total loads and the differentiation between sensible, latent and electrical loads and their hourly daily profiles were the important inputs for the sizing of the infrastructure. The three following steps lead the city towards a sustainable development with a carbon neutral operation. The first step is a load reduction through passive design strategies which reduce primary energy consumption by 40%. The second step is to optimize the supply systems and the energy demand strategies to allow a further saving of 30% to 40%. Finally, renewable energy sources and active renewable strategies that will reduce the primary energy demand by the remaining 20 – 30%.

Project Facts:

Client: Abu Dhabi Future Energy Company

Area: 6.5 km²

Architect: Foster & Partner London, UK

Infrastructure: WSP Group plc, London, UK

Renewable Energies: ETA – Renewable Energies, Florence, Italy

Transportation Consultants: Systematica, Milano, Italy

Climate Engineering: Transsolar Energietechnik GmbH

 

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