BAO Resort Unguja Island, Zanzibar, Tansania

BAO resort is located on the northeast coast of the island of Zanzibar, right by the sea. The design features Moroccan themed villas with several outdoor and semi-outdoor spaces for people to enjoy the tropical Island. No infrastructure connection options are available there. The resort must be designed so that on-site resources alone are sufficient; it should be completely self-sufficient in terms of energy, water and sewage.
The development plan includes several buildings:
Private residences for the client and his family; for the visitors - Moroccan-style individual houses overlooking the sea, a large sloped-roofed building with several rooms, called the ‘Team Village’, and a restaurant.
Expectations are for about 70 guests in the off-season, which can increase to 90 in the high season, staff added.
Efforts were made to avoid a desalination plant, which is standard practice among the neighbours, but instead explore less energy intensive options like rainwater harvesting and ground water. Rainwater harvesting theoretically could provide sufficient water for the entire year but was considered not viable as the only option due to the size of the underground storage needed.. The ground water extraction was also not a viable option due to contamination. Nevertheless, a concept was developed to reduce the desalination requirements by combining with rainwater harvesting. The outdoor pools were designed to be shallow to reduce the volume of water. Natural ways of filtering the pool water was considered to avoid chlorinated water. These concepts were explored with IB kraft. An above ground water tank was sized to cover water demand of at least day and to ensure sufficient pressure in the pipes. Transsolar was given the tasks of enabling the lowest possible energy demand, quantifying it and reconciling it with the possible input from photovoltaics. The first step was to optimize the passive design of the buildings. Solar radiation and climate analysis were used to add sun protection and the various options of how these shading devices can look to be cohesive to the design was together explored with the architect. Different spaces were zoned and categorized for different comfort conditions.
The project plans on using special low-cement stabilized earth blocks for part of the construction and aims on using locally available building materials. After several iterations of thermal simulations, a double roof system, instead of insulation, exposed thermal mass, natural ventilation with night flushing was proposed for most spaces. Silent gravity cooling and air conditioners were proposed for the bedrooms for ensuring a cool space in the peak summers. Conditioning was limited only to bedrooms; thus energy demand was further minimized along with the passive measures.
Transsolar was also tasked with estimating the energy demand of the entire development, such as for plug loads, laundry, kitchen, pools, water desalination, ambient lighting, etc. Electricity production potential by Photovoltaics was simulated and calculated for daily and annual demands. In order to avoid supply bottlenecks even in case of full occupancy, an electricity storage system is necessary, since there is no other possibility of supply, and so sizing of the battery system was also estimated.